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Alcatel GSM Antenna Systems - Product Description
Alcatel GSM Antenna Systems Product Description
Alcatel
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Date 14/09/98
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Alcatel GSM Antenna Systems - Product Description
CONTENTS
1. SCOPE........................................................................................................................................ 2 2. INTRODUCTION ......................................................................................................................... 3 3. ANTENNAS FOR MOBILE COMMUNICATION ........................................................................... 4 3.1 Standard antennas................................................................................................................ 5 3.2 Antennas with dual polarization............................................................................................. 8 3.3 Dual-band antennas............................................................................................................ 10 3.4 Microcellular antennas ........................................................................................................ 11 3.4.1 Outdoor antennas ...................................................................................................... 13 3.4.2 Indoor antennas......................................................................................................... 14 4. OPTIMIZED ANTENNA SYSTEMS ........................................................................................... 14 4.1 Antenna diversity ................................................................................................................ 15 4.2 Antenna beam tilt................................................................................................................ 16 5. ANTENNA CONFIGURATIONS IN MOBILE NETWORKS ........................................................ 18 5.1 EVOLIUM™ A9100 Base Station........................................................................................ 19 5.1.1 Antenna diversity and air combining........................................................................... 20 5.1.2 Configurations without antenna diversity .................................................................... 21 5.2 EVOLIUM™ Micro Base Station ......................................................................................... 21 6. MECHANICAL ANTENNA STRUCTURES............................................................... 22 6.1 Tower mounting for omni antennas..................................................................................... 23 6.2 Tower mounting for (directional) antennas................................................................. 24 6.3 Pole mounting on roof top................................................................................................... 26 6.4 Pole mounting on wall or parapet........................................................................................ 27 7. FEEDER SYSTEM .................................................................................................................... 27 7.1 Feeder cable....................................................................................................................... 28 7.1.1 Technical data for the feeders.................................................................................... 28 7.2 Feeder clamps.................................................................................................................... 30 7.3 Feeder accessory sets........................................................................................................ 31 7.3.1 Jumper cables ........................................................................................................... 31 7.3.2 Connectors ................................................................................................................ 32 7.3.3 Earthing of the feeder cable ....................................................................................... 32 7.4 Feeder systems for microcellular applications ..................................................................... 34 8. POWER DIVIDERS ................................................................................................................... 34
Alcatel
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Alcatel GSM Antenna Systems - Product Description
1. SCOPE This document describes the Alcatel GSM 900, GSM 1800, GSM 1900 and dual-band antenna systems. The description contains the different modules of a complete base-station antenna system.
2. INTRODUCTION An antenna system consists of the following default items: - Antennas including mounting clamps and mechanical downtilt kits, - Mechanical antenna structures, - Feeders and clamps, - Feeder accessories (earthing kits, wall glands, connectors, jumper cables, etc.). Available options are: - Power dividers, - Radiating cables, - Lightning protection for feeders. The following scheme illustrates the typical arrangement of an antenna system.
Alcatel
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OPTIONAL with TMA Lightning rod Antenna
Jumper cable
Mechanical antenna structure
Mounting clamp
TMA Jumper cable1)
Jumper 1) cable
Feeder to BTS
Earthing kit
Feeder installation clamps
Earthing kit Feeder Sockets 7/16”
Wall gland
Plugs 7/16” Grounding Jumper cables1) 1) Jumper
cables only required for feeder 7/8” or 1 5/8”
Figure 1: Typical arrangement of an antenna system
Alcatel
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Alcatel GSM Antenna Systems - Product Description
3. ANTENNAS FOR MOBILE COMMUNICATION For the link between base stations and mobile stations in general linear antennas are used, which are made of either monopole (slab) or dipole elements. Mobile-station antennas mostly consist of a single monopole or patch antennas. Base-station antennas are realized by an array of dipoles. The following chapters focus on the base-station antennas.
3.1 Standard antennas Antennas are generally composed of stacked dipoles (radiators) vertically bundling their radiated power or more generally spoken, to form a particular, desired antenna pattern in vertical plains around the antenna. Depending on the desired gain that wants to be achieved several of those dipoles can be arranged on top of one another (Figure 2).
Dipole
Figure 2: Typical flat- antenna For coverage of a complete, circular-shaped area, omnidirectional antennas are used, while sector antennas ‘illuminate’ a preferred section of the coverage area. Improved antenna directivity of such sector antennas is achieved by placing antenna elements (radiators) in front of a reflector. By doing so, superposition of wave components with suitable phase shifts will result in an accumulation of energy in a preferred direction of space. Besides such mechanical means to influence the antenna pattern (radiator and reflector positioning), the individual radiators can be fed with voltages of exactly defined amplitude and phase via a power distribution network to form the desired antenna pattern in the far field of the antenna. Generally macrocell antennas are offered with 7/16"-female connectors, but microcell antennas are offered with N-female connectors. The Alcatel antenna sets contain mounting clamps for standard poles (typically 90 mm diameter) and all directional antennas are delivered with a mechanical downtilt mounting kit as a standard, if not otherwise stated. Example for the meaning of the designation of an Alcatel antenna set:
Alcatel
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ANT*900/105/13.5/2T/XPol I I I I I I I Extension for dual-polarized antennas I I I I I I Electrical downtilt [ °]; swT: switchable Tilt I I I I I Antenna gain [dBi] I I I I Horizontal beam width [ °] (omni: 360°) I I I Frequency range [MHz] (GSM 900, GSM 1800 or dual band) I I Manufacturer ( * = independent from the manufacturer) I ANTenna
1)
1)
Extension for dual-polarized antennas: - XPol refers to +45° slanted (cross-polarized) antennas, - V+H refers to vertically and horizontally polarized antennas.
Remark: Antenna gains may be variously specified in dBi (related to an isotropic radiator), or in dBd (related to a λ/2 dipole). This document refers to dBi. For easy conversion between differently stated values, the following formula may be used: dBd = dBi - 2.1 Antennas are specified for a specific frequency range and cover usually the whole frequency band including uplink and downlink direction. The impedance of antennas in mobile networks is generally 50 Ω. Since it is not possible to have an exact impedance of 50 Ω over the entire frequency range, the parameter VSWR (Voltage Standing Wave Ratio) defines accordingly the maximum mismatch. VSWR is the ratio of the maximum and minimum voltage of the standing wave, in feeder cables caused by reflection due to impedance mismatch. The indicated HPBW (Half-Power Beam Width) in the designation of antennas specifies the angular range of main power emission. The HPBW is limited by the directions where the antenna radiates half of the power compared to main beam direction in the horizontal plane: 3 dB power decrease. The spatial radiation characteristics, like the location of the maximum radiated power, the respective sidelobes (local maximum, causing a certain risk of interference) and the null directions, in which no power is radiated, are illustrated in the antenna diagrams. With regard to the three dimensions, it is distinguished between the horizontal and the vertical antenna diagrams. The horizontal part refers to the shape of the illuminated area (omni, horizontal HPBW: 360°; or sectorized area), whereas the vertical concentration of the radiated power are shown in the vertical part. The following antenna diagrams present the spatial radiation characteristics of a antenna.
Alcatel
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0 dB
Horizontal
0 dB
Vertical
-3 dB
-3 dB
-10 dB
-10 dB
HPBW
Sidelobe
Main beam Null direction
Figure 3: Example of a -antenna diagram Horizontal HPBW: 65° Vertical HPBW: 9° Alcatel can provide all possible types of antennas (gain, beamwidth, polarization, etc.). The antennas are manufactured according to the highest standards, using the most up-to-date technologies. The following table gives a short overview about the antennas most commonly used. With these antenna types most of the applications can be covered. Antenna gain [dBi] HPBW
900 MHz
1800 MHz
1900 MHz
360°
11
11
11
105°
16
13
13
90°
15.5
16
15.5
65°
17
18
18
33°
20
20
23
Table 1: Values for standard antennas It is to be noted, that the offered antenna configurations in a tender should be considered as typical. When the results of the radio network planning are available and after a site survey, the final solution must be redefined, this can lead to different antennas and different prices.
Alcatel
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Figure 4a: Typical omni antenna
Figure 4b: Typical flat- antenna
3.2 Antennas with dual polarization Applications of dual-polarized antennas may lead to simplified antenna systems and save costs. Dual-polarized antennas contain two independent radiating systems, the polarization of which is differing by 90°. This can be achieved by either using vertical and horizontal polarizations or using systems with +45° slanted (cross) polarizations. Dual-polarized antennas consist of stacked dipoles functioning basically as the standard antennas bundling their radiated power. The dipoles for vertical/horizontal polarization, respectively ±45° are interlocked, therefore the same mechanical dimensions as for standard antennas can be achieved. For necessary decoupling of the two polarization branches the dipoles with a different orient-ation are isolated against each other. Each polarization branch has its own input connector. Figure 5 illustrates the construction of a +45° slanted (cross) polarized antenna.
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Figure 5: Arrangement of a dual- (cross) polarized antenna
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Reception by one dual-polarized antenna (polarization diversity) is an alternative to the conventional space diversity, where two adequately spaced antennas are used (please refer to section 4.1, antenna diversity). In this case both kinds of dual-polarized antennas are applicable . By using dual-polarized antennas also for transmitting it must be considered, that the preferred polarization plane for Tx signals is vertical and deviations will reduce the downlink budget. So the vertical- and horizontal-polarized antenna is the recommended one for a one-Tx signal application.
3 dB 2 dB
Figure 6: Effect of different antenna polarizations on propagation When air combining with dual-polarized antennas is introduced, transmission takes place on both antenna branches. The idea of air combining is to combine transmitted signals in the air and not with an additional combiner, in order to save the respective combiner losses. In this case the crosspolarized antenna is the preferred dual-polarized antenna type, because it must be avoided to transmit in the horizontal plane (worst case for propagation conditions). The use of cross-polarized antennas for urban and suburban areas can be recommended. Due to less reflection and diffrection events in the rural area, the origin polarization (+45° or -45° of the cross-polarized antenna) of the transmitted signal will be conserved and the signal content in the other polarizations can be ignored. This leads to a dependence on the polarization and the assigned TRX (transceiver) and might cause transmission problems as the following example shows: Assuming a two-TRX BTS, one TRX transmitting with +45° and the other TRX transmitting with -45°. The BCCH (Broadcast Control CHannel) is assigned to the antenna branch with +45°. If a neighbour-cell mobile tries to perform an HO (HandOver), caused by power budget or signal level, the decision will be based on the received BCCH level. If the mobile is allocated on a TCH (Traffic CHannel) of the other antenna branch (-45 °), there will occur a sudden change in signal level, due to the different polarization. At the worst there will happen a drastic signal drop and the level-based decision for the HO was incorrect and might lead to a call drop. With respect to this problem and because in rural areas the polarization diversity gain is negligible (please refer to section 4.1, antenna diversity), the vertical-polarized antenna is the preferred type for rural applications.
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3.3 Dual-band antennas A further step to simplify antenna systems is the usage of dual-band antennas. Among other things the reduction of the antenna quantity improves the visual aspects. Thus a GSM-900 and a GSM1800 antenna are combined in one dual-band antenna. The antennas are available as single- or as dual-polarized types. Dual-band antennas, e.g. for GSM-900 and GSM-1800 applications, are characterized by being suitable for both frequency ranges with separate input connectors. This leads to a double number of antenna connectors, compared to a corresponding single-band antenna; two connectors for singleand four connectors for dual-polarized antennas. In this case a dual cable run from the BTS is required to both bands.
GSM 900
Dual-band antenna
GSM 900
GSM 1800
+45°
-45°
+45°
-45°
GSM 1800
+45°
-45°
Diplexer +45°
Feeder
-45°
GSM 900
+45°
-45°
Diplexer -45°
Feeder Diplexer +45°
+45°
Dual-band antenna
+45°
-45°
GSM 1800
+45°
Diplexer -45°
-45°
+45°
GSM 900
-45°
GSM 1800
Figure 7: Cross-polarized dual-band antenna with and without diplexer application
Alcatel
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By upgrading the dual-band antennas with additional diplexers (often integrated in the antenna radome), combining the GSM-900 and GSM-1800 antenna branches with the same polarization, the number of antenna connectors will be less by half and the required feeder system will be the same compared to a single-band antenna system. This kind of application requires further base station diplexers with a corresponding resplit function (please refer to figure 7). The additional costs for the diplexers will be justified, if the reduced expenditure of the feeder system is predominant. Especially for the transition of a single- to a dual-band system the existing feeder system can be used, ensuring a fast installation during retrofit. The decision whether a dual-band antenna or two independent GSM-900 and GSM-1800 antennas should be used, depends strongly on the planning philosophy of the network and operator’s aims. This approach will be explained in the following examples: Example 1: Application of a dual-band antennas in high-traffic urban areas The customer has a GSM-900 as well as a GSM-1800 licence and is currently running a GSM-900 network in an urban area. With increasing traffic, network densification has already been performed, thus the cell ranges are reduced and the omni sites are already sectorized. Typically six single-polarized or three dual-polarized antennas are installed per site in case of a three-sector diversity configuration. In order to increase the traffic a two-layer network should be installed. The coverage ranges of the GSM-900 and GSM-1800 cells will be similar, therefore it is a good solution to reuse the existing sites and replace the existing GSM-900 antennas by dual-band antennas, instead of increasing the amount of antennas up to twelve (or six), or what is even more difficult to realize, that is the acquisition of new GSM-1800 sites. Example 2: Application of separated GSM-900 and GSM-1800 antenna configurations An operator is installing a new dual-band network in low-traffic areas. Since higher coverage ranges can be achieved by means of GSM 900, the operator will try to perform coverage in rural areas with GSM-900 cells and choose smaller cell sizes in urban areas by applying GSM-1800 cells there. In these scenarios no dual-band antennas are required, the cells need to be configured independently of each other. So basically antenna configurations in a dual-band network can be split up in dual-band antenna or monoband antenna configurations.
Alcatel
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3.4 Microcellular antennas In the often heavily multipath-loaded environment of microcells, the electrical antenna properties like gain, pattern, characteristics, etc. loose importance, while on the other hand, for aesthetical reasons, visual appearance/style may appear more significant for the selection of a specific antenna type. For serving the microcellular environment, indoor as well as outdoor, microcellular antennas will be installed at relative low height (generally below roof-top level) in very flexible ways, using house/room walls, urban devices, ceilings, etc. as or for fixation. Following the very compact design of the Micro-BTS, the antenna installation (i.e. antenna plus connecting cables) should also remain visually non-intrusive and - even more important for indoor installations - should respect aesthetic aspects of the installation ambiance.
Figure 8: Mounting of an outdoor and an indoor microcellular antenna
The use of small, inconspicuous antennas is made possible due to the low transmit power of the Micro-BTSs. The antennas are generally equipped with N-type female connectors.
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3.4.1 Outdoor antennas The following table lists the commonly used outdoor antennas for microcellular applications. Antenna gain [dBi] HPBW
900 MHz
1800 MHz
360°
2 5
2 5
90°
8
8
65°
5 bidirectional
10
Table 2: Values for outdoor microcellular antennas The figures below show typical designs for outdoor microcellular antennas.
Figure 9b: Flat
Figure 9a: Omni antenna
Figure 9c: Bidirectional
Figure 9: Typical outdoor microcellular antennas
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3.4.2 Indoor antennas The following table lists the commonly used indoor antennas for microcellular applications. Antenna gain [dBi] Beam width
900 MHz
1800 MHz
360°
2
2 2 Multi-band antenna 7 Multi-band antenna
90° 8
8
Table 3: Values for indoor microcellullar antennas The figures below show typical designs for indoor microcellular antennas:
Figure 10c:
Figure 10b: Flat
Figure 10a: Omni, pole
Figure 10d: Omni antenna
Figure 10: Typical indoor microcellular antennas
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4. OPTIMIZED ANTENNA SYSTEMS In this chapter, two methods will be introduced which improve the effectivity of antenna systems.
4.1 Antenna diversity The purpose of using diversity is to reduce short-term fading effects, in order to achieve an acceptable level of performance (receiver sensitivity), instead of increasing the transmitted power or the bandwidth on the other side. The principle relies on the combination of two or more signals, containing the same information, which are at least partially decorrelated. If two signals of the same level are completely decorrelated, the probability that both signals will undergo the same depth of fade is only the square compared to the probability for one signal. Therefore the signal reliability is increased. The most commonly used diversity system is space diversity. The decorrelation is achieved by receiving the signals by means of two spatially separated (horizontal or vertical) antennas. If the separation of the antennas is at least 20 λ for horizontal separation (6 m for GSM 900 and 3 m for GSM 1800) and 15 λ for vertical separation (5 m for GSM 900 and 2.5 m for GSM 1800), a sufficient low correlation coefficient of 0.7 can be achieved. Space diversity systems use only one polarization direction.
Rx
Demod Deci- To BTS sion
Rxdiv Dualpolarized antenna
Demod
Singlepolarized antennas
Figure 11: Diversity systems In urban scenarios, where multipath propagation due to reflection and diffraction is predominant, the orientation of a single wave (and therefore the polarization) changes. Besides of signals with the original vertical polarization, there are also signals with horizontal polarization. Considering the fact, that a hand-held mobile or the antenna of a moving car is usually inclined to the vertical, there is a degradation due to signal loss using space diversity systems. Another diversity system, the polarization diversity system, recovers this signal energy loss by an additional orthogonal polarization. Decorrelation is achieved by using antennas with different polarizations (please refer to section 3.2, antennas with dual polarization).
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For urban and suburban application the achievable diversity gain is comparable for both types, the space and polarization diversity. Due to the less multipath propagation the gain in rural areas is generally lower. The polarization diversity gain of the rural area is even negligible, thus that the space diversity is the preferred type for rural areas. The diversity gain itself depends on a lot of parameters, like signal decorrelation and level, morphostructure, topology, antenna mounting, etc., and differs in the range of 2 dB up to 6 dB.
4.2 Antenna beam tilt In dense networks it is often advisable to lower the main lobe of the antenna in the vertical plane (downtilt) to ensure a reduction of interferences (see Figure 12). Hereby the main radiation lobe is adjusted below the horizontal by a specific angular displacement expressed in degrees (°).
Main beam direction
a
Ma in b eam
a
dire
ctio n
b
c
Figure 12: Illumination with and without antenna downtilt There are three kinds of beam tilt, the mechanical, the fixed electrical and the switchable electrical downtilt and when used, it must be applied for the Tx as well as for the Rx antennas.
Mechanical beam tilt is achieved by physically tilting the antenna out of the perpendicular by using a downtilt kit (brackets), factory-made specifically for that type of antenna. The following figure presents such a downtilt kit.
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Figure 13: Mechanical downtilt kit for antennas The advantages of this kind of beam tilting are the cost effectivity and the flexibility. A later adjustment of the vertical tilt is possible and therefore only one single antenna type may be used. The additional expenses for the mechanical downtilt are moderate and already included in the costs for the Alcatel antenna sets. The drawback is that the mechanical beam tilt has no effect on the side-lobe characteristics of the antenna (please refer to section 3.1, Figure 3). Providing a much more accurate and predictable means of controlling antenna coverage, the electrical beam tilt provides a distinct performance advantage; all directions/lobes (main, side and rear) are tilted to the same measure, controlling interferences of all directions. The electrical tilt is achieved by altering the phasing within the antenna. This technique produces beam tilt without physical movement of the antenna.
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τ =0 τ=t gle tilt an n w o D
τ = 2t τ = 3t
τ = delay time Figure 14: Electrical-downtilt technology
The electrical downtilt can be provided as fixed or switchable. The fixed one is tuned by the manufacturer, a later adjustment is not possible (except by means of an additional mechanical downtilt kit). This is disadvantageous because new antenna types have to be introduced, if other downtilts concerning a new network planning phase are required. This drawback can be avoided by using antennas with switchable electrical downtilt. By means of this advanced antenna type the electrical downtilt can be adjusted by a lever on the rear of the antenna. The antenna becomes very flexible with regard to the changing network conditions while maintaining the advantages of an electrical downtilt. On the other side this antenna type is rather expensive. The common mechanical downtilt-values range is from 2° to 10° (sometimes even more), depending on the vertical beam pattern of the actual antenna. Antennas with switchable electrical downtilt allow adjustments of the tilt angle from e.g. 3° to 15°, in one-degree steps. Both mechanical and electrical downtilt can also be combined. This results in a distinct range reduction in sidelobe direction (interference reduction). When choosing sector antennas with high electrical downtilt (6° to 8°) and applying mechanical-uptilt installation, an optimum coverage range in main-beam direction can be achieved.
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5. ANTENNA CONFIGURATIONS IN MOBILE NETWORKS In general there are many possibilities for antenna configurations. The antenna configuration depends on the antenna coupling level (stage between the antennas and the TRX level) of the BTS (Base Transceiver Station). This chapter gives an overview about the standard antenna configurations of the Alcatel EVOLIUM™ Base Station family.
5.1 EVOLIUM™ A9100 Base Station The antenna coupling level of the EVOLIUM™ A9100 Base Station is based on the separation between the combiner stage and a suitable antenna output stage. With this kind of modular construction the antenna coupling level can be adapted to a wide range of mobile-network requirements for antenna configurations, like reduction of attenuation losses (e.g. combiner loss) and minimization of the number of antennas per base station site.
Air interface Crosspolarized antenna
Singlepolarized antenna
Singlepolarized antenna
....
....
Antenna configurations
Antenna output stage
Antenna output stage
Antenna coupling level
.............
Combiner stage
TRX level
TRX
TRX
TRX
......
........................................
TRX
TRX
TRX
............. BCF level
Station unit module
EVOLIUMTM A9100 Base Station Abis interface
Abbreviations: BCF Base station Control Function; TRX Transceiver
Figure 15: Antenna configurations in conjunction
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with the EVOLIUM™ A9100 Base Station 5.1.1 Antenna diversity and air combining For antenna configurations with antenna diversity, which use air combiner technique, Alcatel provides the twin Receiver Front End (RFE) and duplexer stage. This antenna output stage connects two transmit signals to two antennas (or to one dual-polarized antenna) and distributes the received signals from each antenna to two receivers (for normal and the diversity reception). The module includes duplexers, LNAs and splitters. Each EVOLIUM™ A9100 Base Station cell is equipped with at least one such stage, which features high sensitivity, low attenuation and minimum intermodulation products. The following figure illustrates the ed antenna configurations of the twin receiver front end and duplexer stage.
Crosspolarized configuration
Antenna
Feeder TxA - RxA - RxdivB
TxB - RxB - RxdivA
Antenna
Singlepolarized configuration
Feeder
TxA - RxA - RxdivB
TxB - RxB - RxdivA
TxA - RxA - RxdivB
TxB - RxB - RxdivA
Duplexer Filter
Duplexer Filter
LNA
LNA
Splitter
Splitter
TxA
RxdivA RxA
RxdivB
Twin RFE and duplexer stage
TxB
RxB
Figure 16: Antenna configurations with one twin Receiver Front End (RFE) and duplexer stage for one cell
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The cross-polarized configuration has the advantage of minimizing the amount of antennas. Both configurations fulfil diversity aspects: By means of cross-polarized antennas the polarization diversity and with single-polarized antennas the space diversity is realized. One of this twin receiver front end and duplexer stage s the air combining (no additional combiner stage necessary) for up to two TRXs per cell. Under the name ‘low-loss configuration’ the EVOLIUM™ A9100 Base Station s two of these stages per cell, and air combining for up to four TRXs per cell is possible. 5.1.2 Configurations without antenna diversity For antenna configurations with only one single-polarized antenna, in order to minimize the number of antennas per site, Alcatel developed another antenna output stage: the RFE, duplexer and WBC stage. This module covers the functionalities of both twin receiver front end and duplexer stage as well as twin wide-band combiner stage.
Antenna
Feeder Tx
Rx
Duplexer Filter
Filter
LNA
WBC
TxA RxA
Duplexer combiner stage (ANs)
Splitter
TxB RxB
Figure 17: Antenna configuration with one RFE, duplexer and WBC stage for one cell This one-antenna configuration (for one cell) does not the diversity and air-combining aspects.
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5.2 EVOLIUM™ Micro Base Station Alcatel has developed a broad range of EVOLIUM™ Micro Base Stations to provide against any coverage needs. By using a modular concept the EVOLIUM™ Micro Base Stations are upgradable with regard to the amount of TRXs and cells. Figure 18 presents the different antenna configurations for one-cell applications.
Antenna
Antenna
Feeder
Feeder
3-dB coupler
1 TRX
2 TRXs
2 TRXs
Figure 18: Different antenna configurations with the EVOLIUM™ Micro Base Stations for one-cell applications With regard to the requirements of micro base stations, like consideration of aesthetic aspects of the installation ambiance (number of antennas), the antenna output stage of the EVOLIUM™ Micro Base Station contains a duplexer which combines the transmitter (Tx) and receiver (Rx) paths. With this technology only one antenna for one-TRX applications is needed. The high output power provided by EVOLIUM™ Micro Base Stations can be achieved by using air combining (no additional combiner losses) for the 2-TRX configuration. In this application either two standard micro antennas (single-polarized) or one dual-polarized antenna are used, ing the antenna diversity technology. In addition, Alcatel offers a one-antenna system for the 2-TRX configuration. The resulting benefits are reduced site acquisition constraints and lower antenna installation efforts and costs.
Alcatel
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6. MECHANICAL ANTENNA STRUCTURES Mechanical antenna structures serve two purposes: Grouping and accurate positioning of the antennas or antenna arrays, as laid out for generation of the desired pattern to illuminate the specified area, Mechanical interface and fixation of antennas or antenna arrays at the desired altitude to the carrier structure, which may be a tower, mast, building wall or roof top, etc.. The following paragraphs concentrate on a few, but more often used and most convenient realization variants for antenna mounts. In general, the mounting hardware kits are applicable for antennas of all frequency ranges (900 MHz, 1800 MHz, 1900 MHz) and for dual-band antennas including installation and grounding material. Important remark: The figures, pictures and realization examples shown below shall be considered only as a basic technical reference. The detailed technical realization for a specific mount must be traced to the respective materialization lists and has to be determined in co-operation with the installation department. Safety remark: Rigidity and stability of the mounts have to be checked/analyzed with respect to total weight, ice and wind load (in projects often mandatory to get official tower permit).
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6.1 Tower mounting for omni antennas If the tower or mast top is still available, the omnidirectional mounting as per Figure 19 will be the preferable solution (for the EVOLIUM™ A9100 Base Station). A minimum horizontal spacing of three or six meters between the poles bearing the Rx and Rxdiv antennas (please refer to section 4.1, antenna diversity) respectively between the poles carrying Tx and Rx antennas should be preserved in order to confirm a sufficient decoupling between the antenna branches. If the horizontal spacing is below the required minimum an additional vertical spacing of 0.5 m is necessary.
Omni antennas
Figure 19: Tower mounting for omni antennas
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6.2 Tower mounting for (directional) antennas By means of horizontally ing arms in conjunction with vertical carrier pipes, antennas can be positioned at the right spacing away from the tower and at the required altitude along the tower.
Horizontally ing arms
Vertical carrier pipe
Grounding
Figure 20: Tower mounting for antennas
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The ing arms are mounted to the tower legs by means of crossover plates. The type of tower leg (tubular or angular cross section) and its size determine the required type of crossover plate. The antenna s are fixed by the usual U-clamps to the vertical carrier pipe, which itself is mounted on both ends to the ing arms by pipe crossover clamps, the latter being part of the mounting assembly kit. The mounting assemblies can be used on towers with square or triangular cross section. Instead of the unidirectional (single-sector) configuration, also bi- or tri-sectored versions can be realized by additional mounting assemblies at the adjacent/opposite tower legs.
6.3 Pole mounting on roof top Especially in conjunction with tall buildings, small pipe masts or poles can be used for mounting and carrying antenna arrays. Usually each pole would carry one or max. two s in line, depending on the height and the wind load restrictions. The Alcatel antenna pipe masts are modularly upgradable. Therefore the masts are suitable for most applications.
Figure 21: Pole mounting on roof top
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Usually the pole is fixed by four heavy load bolts to the concrete roof surface. Tall poles are additionally propped by two bracons. The antenna itself is fixed by means of standard U-clamps to the pole. In some cases it is necessary to have an additional mounting layer between the roof and the pole mounting hardware. It protects the roof against direct mechanical effects of the mounting hardware and has the benefits, that the weight of the mounting hardware is distributed over a larger plain (stability aspects) and no fixing holes in the roof are necessary. The layer is set up with a corresponding amount of hexagonal pavings (according to the stability requirements) and an additional isolation between them and the roof. The hexagonal pavings are pre-manufactured steel frames which will be fixed together and will be replenished with concrete on site. This is an Alcatel option for the standard pole mounting.
6.4 Pole mounting on wall or parapet Also small pipe masts or poles are applied to mount directive antennas in front of house walls, house corners, roof edges or parapets. Adequately spaced, separate poles carry the corresponding antennas. Due to the high bending momentum at least two anchor plates are needed (please refer to Figure 22).
Anchor plates
Figure 22: Wall mounting
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7. FEEDER SYSTEM The feeder system presents the interface between the antennas and the base station. It includes the feeder cable, the feeder clamps, and essential accessories, like jumper cables and earthing kits.
7.1 Feeder cable The typical design of todays RF-transmission lines for mobile communications shows a dielectric of foam polyethylene with a very low dielectric loss. This dielectric does not age and is not hygroscopic. The inner conductors are copper wires. The outer conductors have an annular corrugation. By means of the dielectric the inner conductor is centered in such a manner that no relative movement between the conductors due to temperature variations or due to pulling can occur. The cables have abrasion-resistant black polyethylene outer jackets. If required, the cables can be supplied with flame-retarded low-smoke zero-halogen sheaths. Inner conductor
Outer conductor
Dielectric
Jacket
Figure 23: Feeder cable Feeder types and lengths depend on specific site and radio network planning requirements. The exact length will be determined after a site survey.
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7.1.1 Technical data for the feeders Inner conductor Dielectric Outer conductor Jacket
Type
Copper wire Low-density foam polyethylene (PE) Corrugated copper tube Polyethylene (PE), black
Minimum bending radius
Jacket (outer diameter)
Weight (m)
Recommended clamp spacing
Single bending
Repeated bending
LCF 1/2”
70 mm
210 mm
16 mm
0.35 kg
0.6 m
LCF 7/8”
120 mm
360 mm
28 mm
0.62 kg
0.8 m
LCF 1 5/8”
300 mm
900 mm
49.7 mm
1.5 kg
1.2 m
Table 4: Mechanical data for feeders
Operating frequency:
900 MHz
Type
Attenuation / 100 m
Commonly used for up to 1)
LCF 1/2”
6.6 dB
45 m
LCF 7/8”
4.0 dB
75 m
LCF 1 5/8”
2.6 dB
115 m
Operating frequency:
1800 MHz
Type
Attenuation/100 m
Commonly used for up to 1)
LCF 1/2”
10.3 dB
30 m
LCF 7/8”
6.0 dB
50 m
LCF 1 5/8”
4.0 dB
75 m
Operating frequency:
1900 MHz
Type
Attenuation/100 m
Commonly used for up to 1)
LCF 1/2”
10.6 dB
28 m
LCF 7/8”
6.3 dB
47 m
LCF 1 5/8”
4.2 dB
71 m
1) See next page
Table 5: Electrical data for feeders
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Remarks: All attenuation values given in the above tables are related to 50-Ω impedance type of feeder. Values were derived from ‘attenuation-vs.-frequency’ tables provided by manufacturer of feeders through linearization between fixed, measured samples. Consequently, above statements should not be regarded as highly accurate, measured values at a specific operating frequency (indicated in the headers of tables). 1)
Column ‘Commonly used for up to’ in table 5 is given in order to ensure feeder losses below or equal to 3.0 dB (connector and jumper cable losses not included). These ‘upper limits’ in feeder length should be considered as guidelines only; rounded down to the closest integer value in meters.
Deviations from ‘recommended length’ values are possible, but must be considered in the radio network planning process after discussion with the radio network planning team.
7.2 Feeder clamps The feeder clamps mount the feeder cable to the mounting object, e.g. a mast or a pole. Each cable clamp includes a twin-cable run for the common fixture of two feeders.
1. Cable clamps 3. Double bearing 2. Antenna cable 4. Counterpart 5. Anchor tape
Figure 24: Feeder installation
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7.3 Feeder accessory sets Alcatel provides different accessory sets depending on the feeder type. These accessory sets contain earthing kits, wall glands, connectors, isolation material and, if required, the jumper cable between feeder and antenna. The standard delivery consists of three earthing kits per feeder cable. An additional lightning protection, by means of a lightning rod at the top of the building or mast and an EMP device (ElectroMagnetic Protection, already included in the outdoor BTS) is available. 7.3.1 Jumper cables With regard to the restricted minimum bending radius of the standard LCF feeder cable (please refer to section 7.1.1, technical data data for feeders) a higher flexible connecting feeder cable, the so-called jumper cable, is required. This jumper cable allows an accurate mounting and connection of the feeder cable with the antenna or the BTS in areas that require tight bending and extremely small bending radii. Particularly for the 7/8“ and the 1 5/8“ feeder cables these jumper cables are essentially.
Feeder type
Jumper cable Jumper cable Jumper cable
Cable length
Cable diameter
Total attenuation
m 2 3 5
mm 13.5 13.5 13.5
900 MHz 1800 MHz 0.32 dB 0.42dB 0.42 dB 0.57dB 0.63 dB 0.88dB
Min. bending radius mm 30 30 30
Cable type
HCF 1/2" CuH HCF 1/2" CuH HCF 1/2" CuH
Table 6: Jumper cables
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Figure 25: Flexible jumper cable 7.3.2 Connectors One possible connection between feeder cable and jumper cable is shown in the following illustrations. The connecting point must provide a perfect and long-term mechanical and electrical connection, which is also resistant against environmental influences. These conditions are met due to the construction of the components, and no further protection of the connecting point is required.
Figure 26: Connection between feeder and jumper cable The connectors are generally 7/16 connectors with an outer-conductor diameter of 16 mm. This system is used in all cases where robust and precise connections are required. The mating being screw thread and sealed by a face ring. The feeder cable is equipped with female, the jumper cable with male connector as a standard.
Male connector
Female connector
Figure 27: 7/16 connectors 7.3.3 Earthing of the feeder cable The feeder cable earthing kits ground the feeder cable. They are mounted in defined distances over the total cable length in order to protect overvoltages on the feeder cable. The earthing kit complies with all relevant standards and is resistant to all relevant environmental influences. Figure 28 presents a possible earthing kit. The earthing body consists of stainless steel with vulcanized Ethylene-Propylene-Caotchouc. The grounding wire (16 mm2, both ends terminated with cable eyes) is fixed with stainless steel screws to the surface. This construction of a preassembled grounding kit enables a quick and accurate mounting.
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Figure 28: Cable earthing At least three earthing points are recommended in order to achieve a good grounding result: - One near the top of the feeder cable, - One where the feeder cable leaves the tower or mast, - One where the feeder cable enters the building or shelter, - In areas of high lightning activities one on top of that every 20 m. The following figure illustrates the earthing of the feeder cable at the cable entry of a building.
Figure 29: Feeder earthing at cable entry (wall gland)
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7.4 Feeder systems for microcellular applications As already mentioned in section 3.4, microcellular antennas, the antenna installation (e.g. antenna and connecting cables) for a Micro-BTS should consider the aesthetic installation aspects. Figure 30 outlines the simple RF installation of the Micro-BTS. For the connection between the Micro-BTS and the antenna, a factory-made feeder cable is used. Additional earthing, as shown, is needed only in case of outdoor installation and in mixed configurations, when the BTS is installed indoor and the antenna is mounted outdoor.
Microcellular antenna
Micro-BTS unit
N-connector
Earth clamps AC + data interface N-connector Cable channel (to and ’hide’ the cable) Factory-made feeder cable (optional lengths: 5 m and 15 m) Earthing kit (required for outdoor installation)
Figure 30: Example of a microcellular antenna installation The factory-made feeder is a highly flexible low-loss cable, already equipped with N-type male connectors on both ends. If necessary, the cable length can be cut to the specific needs on site and the connector can be reassembled.
Feeder type
MIC FEED 5 MIC FEED 15
Cable length
Cable diameter
Total attenuation
m 5 15
mm 13.5 13.5
900 MHz 1800 MHz 0.62 dB 0.88 dB 1.68 dB 2.43 dB
Min. bending radius mm 30 30
Cable type
HCF 1/2" CuH HCF 1/2" CuH
Table 7: Feeders for microcellular applications In case of microcellular antenna feeder installation, cable tubes or plastic cable channels/ducts are used. This allows to hide the (black-coloured) cable inside the cable channel. Besides this, the use of cable channels enables an exact and rapid fixation.
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8. POWER DIVIDERS Power dividers (or power splitters) can be used to connect two, three or four antennas to a single feeder cable. Two main applications for power dividers exist: Creation of omni-directional antenna patterns by using directional antennas, when the top of a mast or tower is not accessible (radial, skew or quasi-omni configuration), Feeding of two directional antenna sets by a single BTS (cell) for road coverage.
Quasi-omni configuration
4-to-1 power divider 6 dB ‘distribution loss’
To the BTS
Figure 31: Typical application of power dividers The Power Divider (PD) can be combined with the tower-mounted amplifier equipment (TMA). To combine antennas for particular radiation patterns or for an indoor distribution network, power dividers with the following features are available: Low-loss coaxial-line transformation, High power rating, Indoor and outdoor use, Very small dimensions.
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The technical data of symmetrical power dividers are given in the tables below:
Electrical specifications Divider type Distribution loss
[dB]
Insertion loss
[dB]
2-way
3-way
4-way
3
4.8
6
< 0.05
VSWR
< 1.1
Impedance
50 Ω
Mechanical specifications [mm]
Dimensions W x H x D
210 x 80 x 80
160 x 80 x 80
Connector type
285 x 80 x 80
7/16’’ female
Material
Case: Aluminum Inner conductor: Brass
Mounting
Bracket included for wall mounting: For tubular-mast mounting clamps with diameter between 50 mm and 105 mm
Table 8: Technical data for power dividers For an especially adapted indoor distribution network, there are also asymmetrical power dividers available.
End of Document
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CONTENTS
1. SCOPE........................................................................................................................................ 2 2. INTRODUCTION ......................................................................................................................... 3 3. ANTENNAS FOR MOBILE COMMUNICATION ........................................................................... 4 3.1 Standard antennas................................................................................................................ 5 3.2 Antennas with dual polarization............................................................................................. 8 3.3 Dual-band antennas............................................................................................................ 10 3.4 Microcellular antennas ........................................................................................................ 11 3.4.1 Outdoor antennas ...................................................................................................... 13 3.4.2 Indoor antennas......................................................................................................... 14 4. OPTIMIZED ANTENNA SYSTEMS ........................................................................................... 14 4.1 Antenna diversity ................................................................................................................ 15 4.2 Antenna beam tilt................................................................................................................ 16 5. ANTENNA CONFIGURATIONS IN MOBILE NETWORKS ........................................................ 18 5.1 EVOLIUM™ A9100 Base Station........................................................................................ 19 5.1.1 Antenna diversity and air combining........................................................................... 20 5.1.2 Configurations without antenna diversity .................................................................... 21 5.2 EVOLIUM™ Micro Base Station ......................................................................................... 21 6. MECHANICAL ANTENNA STRUCTURES............................................................... 22 6.1 Tower mounting for omni antennas..................................................................................... 23 6.2 Tower mounting for (directional) antennas................................................................. 24 6.3 Pole mounting on roof top................................................................................................... 26 6.4 Pole mounting on wall or parapet........................................................................................ 27 7. FEEDER SYSTEM .................................................................................................................... 27 7.1 Feeder cable....................................................................................................................... 28 7.1.1 Technical data for the feeders.................................................................................... 28 7.2 Feeder clamps.................................................................................................................... 30 7.3 Feeder accessory sets........................................................................................................ 31 7.3.1 Jumper cables ........................................................................................................... 31 7.3.2 Connectors ................................................................................................................ 32 7.3.3 Earthing of the feeder cable ....................................................................................... 32 7.4 Feeder systems for microcellular applications ..................................................................... 34 8. POWER DIVIDERS ................................................................................................................... 34
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1. SCOPE This document describes the Alcatel GSM 900, GSM 1800, GSM 1900 and dual-band antenna systems. The description contains the different modules of a complete base-station antenna system.
2. INTRODUCTION An antenna system consists of the following default items: - Antennas including mounting clamps and mechanical downtilt kits, - Mechanical antenna structures, - Feeders and clamps, - Feeder accessories (earthing kits, wall glands, connectors, jumper cables, etc.). Available options are: - Power dividers, - Radiating cables, - Lightning protection for feeders. The following scheme illustrates the typical arrangement of an antenna system.
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OPTIONAL with TMA Lightning rod Antenna
Jumper cable
Mechanical antenna structure
Mounting clamp
TMA Jumper cable1)
Jumper 1) cable
Feeder to BTS
Earthing kit
Feeder installation clamps
Earthing kit Feeder Sockets 7/16”
Wall gland
Plugs 7/16” Grounding Jumper cables1) 1) Jumper
cables only required for feeder 7/8” or 1 5/8”
Figure 1: Typical arrangement of an antenna system
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3. ANTENNAS FOR MOBILE COMMUNICATION For the link between base stations and mobile stations in general linear antennas are used, which are made of either monopole (slab) or dipole elements. Mobile-station antennas mostly consist of a single monopole or patch antennas. Base-station antennas are realized by an array of dipoles. The following chapters focus on the base-station antennas.
3.1 Standard antennas Antennas are generally composed of stacked dipoles (radiators) vertically bundling their radiated power or more generally spoken, to form a particular, desired antenna pattern in vertical plains around the antenna. Depending on the desired gain that wants to be achieved several of those dipoles can be arranged on top of one another (Figure 2).
Dipole
Figure 2: Typical flat- antenna For coverage of a complete, circular-shaped area, omnidirectional antennas are used, while sector antennas ‘illuminate’ a preferred section of the coverage area. Improved antenna directivity of such sector antennas is achieved by placing antenna elements (radiators) in front of a reflector. By doing so, superposition of wave components with suitable phase shifts will result in an accumulation of energy in a preferred direction of space. Besides such mechanical means to influence the antenna pattern (radiator and reflector positioning), the individual radiators can be fed with voltages of exactly defined amplitude and phase via a power distribution network to form the desired antenna pattern in the far field of the antenna. Generally macrocell antennas are offered with 7/16"-female connectors, but microcell antennas are offered with N-female connectors. The Alcatel antenna sets contain mounting clamps for standard poles (typically 90 mm diameter) and all directional antennas are delivered with a mechanical downtilt mounting kit as a standard, if not otherwise stated. Example for the meaning of the designation of an Alcatel antenna set:
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ANT*900/105/13.5/2T/XPol I I I I I I I Extension for dual-polarized antennas I I I I I I Electrical downtilt [ °]; swT: switchable Tilt I I I I I Antenna gain [dBi] I I I I Horizontal beam width [ °] (omni: 360°) I I I Frequency range [MHz] (GSM 900, GSM 1800 or dual band) I I Manufacturer ( * = independent from the manufacturer) I ANTenna
1)
1)
Extension for dual-polarized antennas: - XPol refers to +45° slanted (cross-polarized) antennas, - V+H refers to vertically and horizontally polarized antennas.
Remark: Antenna gains may be variously specified in dBi (related to an isotropic radiator), or in dBd (related to a λ/2 dipole). This document refers to dBi. For easy conversion between differently stated values, the following formula may be used: dBd = dBi - 2.1 Antennas are specified for a specific frequency range and cover usually the whole frequency band including uplink and downlink direction. The impedance of antennas in mobile networks is generally 50 Ω. Since it is not possible to have an exact impedance of 50 Ω over the entire frequency range, the parameter VSWR (Voltage Standing Wave Ratio) defines accordingly the maximum mismatch. VSWR is the ratio of the maximum and minimum voltage of the standing wave, in feeder cables caused by reflection due to impedance mismatch. The indicated HPBW (Half-Power Beam Width) in the designation of antennas specifies the angular range of main power emission. The HPBW is limited by the directions where the antenna radiates half of the power compared to main beam direction in the horizontal plane: 3 dB power decrease. The spatial radiation characteristics, like the location of the maximum radiated power, the respective sidelobes (local maximum, causing a certain risk of interference) and the null directions, in which no power is radiated, are illustrated in the antenna diagrams. With regard to the three dimensions, it is distinguished between the horizontal and the vertical antenna diagrams. The horizontal part refers to the shape of the illuminated area (omni, horizontal HPBW: 360°; or sectorized area), whereas the vertical concentration of the radiated power are shown in the vertical part. The following antenna diagrams present the spatial radiation characteristics of a antenna.
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0 dB
Horizontal
0 dB
Vertical
-3 dB
-3 dB
-10 dB
-10 dB
HPBW
Sidelobe
Main beam Null direction
Figure 3: Example of a -antenna diagram Horizontal HPBW: 65° Vertical HPBW: 9° Alcatel can provide all possible types of antennas (gain, beamwidth, polarization, etc.). The antennas are manufactured according to the highest standards, using the most up-to-date technologies. The following table gives a short overview about the antennas most commonly used. With these antenna types most of the applications can be covered. Antenna gain [dBi] HPBW
900 MHz
1800 MHz
1900 MHz
360°
11
11
11
105°
16
13
13
90°
15.5
16
15.5
65°
17
18
18
33°
20
20
23
Table 1: Values for standard antennas It is to be noted, that the offered antenna configurations in a tender should be considered as typical. When the results of the radio network planning are available and after a site survey, the final solution must be redefined, this can lead to different antennas and different prices.
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Figure 4a: Typical omni antenna
Figure 4b: Typical flat- antenna
3.2 Antennas with dual polarization Applications of dual-polarized antennas may lead to simplified antenna systems and save costs. Dual-polarized antennas contain two independent radiating systems, the polarization of which is differing by 90°. This can be achieved by either using vertical and horizontal polarizations or using systems with +45° slanted (cross) polarizations. Dual-polarized antennas consist of stacked dipoles functioning basically as the standard antennas bundling their radiated power. The dipoles for vertical/horizontal polarization, respectively ±45° are interlocked, therefore the same mechanical dimensions as for standard antennas can be achieved. For necessary decoupling of the two polarization branches the dipoles with a different orient-ation are isolated against each other. Each polarization branch has its own input connector. Figure 5 illustrates the construction of a +45° slanted (cross) polarized antenna.
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Figure 5: Arrangement of a dual- (cross) polarized antenna
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Reception by one dual-polarized antenna (polarization diversity) is an alternative to the conventional space diversity, where two adequately spaced antennas are used (please refer to section 4.1, antenna diversity). In this case both kinds of dual-polarized antennas are applicable . By using dual-polarized antennas also for transmitting it must be considered, that the preferred polarization plane for Tx signals is vertical and deviations will reduce the downlink budget. So the vertical- and horizontal-polarized antenna is the recommended one for a one-Tx signal application.
3 dB 2 dB
Figure 6: Effect of different antenna polarizations on propagation When air combining with dual-polarized antennas is introduced, transmission takes place on both antenna branches. The idea of air combining is to combine transmitted signals in the air and not with an additional combiner, in order to save the respective combiner losses. In this case the crosspolarized antenna is the preferred dual-polarized antenna type, because it must be avoided to transmit in the horizontal plane (worst case for propagation conditions). The use of cross-polarized antennas for urban and suburban areas can be recommended. Due to less reflection and diffrection events in the rural area, the origin polarization (+45° or -45° of the cross-polarized antenna) of the transmitted signal will be conserved and the signal content in the other polarizations can be ignored. This leads to a dependence on the polarization and the assigned TRX (transceiver) and might cause transmission problems as the following example shows: Assuming a two-TRX BTS, one TRX transmitting with +45° and the other TRX transmitting with -45°. The BCCH (Broadcast Control CHannel) is assigned to the antenna branch with +45°. If a neighbour-cell mobile tries to perform an HO (HandOver), caused by power budget or signal level, the decision will be based on the received BCCH level. If the mobile is allocated on a TCH (Traffic CHannel) of the other antenna branch (-45 °), there will occur a sudden change in signal level, due to the different polarization. At the worst there will happen a drastic signal drop and the level-based decision for the HO was incorrect and might lead to a call drop. With respect to this problem and because in rural areas the polarization diversity gain is negligible (please refer to section 4.1, antenna diversity), the vertical-polarized antenna is the preferred type for rural applications.
Alcatel
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3.3 Dual-band antennas A further step to simplify antenna systems is the usage of dual-band antennas. Among other things the reduction of the antenna quantity improves the visual aspects. Thus a GSM-900 and a GSM1800 antenna are combined in one dual-band antenna. The antennas are available as single- or as dual-polarized types. Dual-band antennas, e.g. for GSM-900 and GSM-1800 applications, are characterized by being suitable for both frequency ranges with separate input connectors. This leads to a double number of antenna connectors, compared to a corresponding single-band antenna; two connectors for singleand four connectors for dual-polarized antennas. In this case a dual cable run from the BTS is required to both bands.
GSM 900
Dual-band antenna
GSM 900
GSM 1800
+45°
-45°
+45°
-45°
GSM 1800
+45°
-45°
Diplexer +45°
Feeder
-45°
GSM 900
+45°
-45°
Diplexer -45°
Feeder Diplexer +45°
+45°
Dual-band antenna
+45°
-45°
GSM 1800
+45°
Diplexer -45°
-45°
+45°
GSM 900
-45°
GSM 1800
Figure 7: Cross-polarized dual-band antenna with and without diplexer application
Alcatel
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By upgrading the dual-band antennas with additional diplexers (often integrated in the antenna radome), combining the GSM-900 and GSM-1800 antenna branches with the same polarization, the number of antenna connectors will be less by half and the required feeder system will be the same compared to a single-band antenna system. This kind of application requires further base station diplexers with a corresponding resplit function (please refer to figure 7). The additional costs for the diplexers will be justified, if the reduced expenditure of the feeder system is predominant. Especially for the transition of a single- to a dual-band system the existing feeder system can be used, ensuring a fast installation during retrofit. The decision whether a dual-band antenna or two independent GSM-900 and GSM-1800 antennas should be used, depends strongly on the planning philosophy of the network and operator’s aims. This approach will be explained in the following examples: Example 1: Application of a dual-band antennas in high-traffic urban areas The customer has a GSM-900 as well as a GSM-1800 licence and is currently running a GSM-900 network in an urban area. With increasing traffic, network densification has already been performed, thus the cell ranges are reduced and the omni sites are already sectorized. Typically six single-polarized or three dual-polarized antennas are installed per site in case of a three-sector diversity configuration. In order to increase the traffic a two-layer network should be installed. The coverage ranges of the GSM-900 and GSM-1800 cells will be similar, therefore it is a good solution to reuse the existing sites and replace the existing GSM-900 antennas by dual-band antennas, instead of increasing the amount of antennas up to twelve (or six), or what is even more difficult to realize, that is the acquisition of new GSM-1800 sites. Example 2: Application of separated GSM-900 and GSM-1800 antenna configurations An operator is installing a new dual-band network in low-traffic areas. Since higher coverage ranges can be achieved by means of GSM 900, the operator will try to perform coverage in rural areas with GSM-900 cells and choose smaller cell sizes in urban areas by applying GSM-1800 cells there. In these scenarios no dual-band antennas are required, the cells need to be configured independently of each other. So basically antenna configurations in a dual-band network can be split up in dual-band antenna or monoband antenna configurations.
Alcatel
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3.4 Microcellular antennas In the often heavily multipath-loaded environment of microcells, the electrical antenna properties like gain, pattern, characteristics, etc. loose importance, while on the other hand, for aesthetical reasons, visual appearance/style may appear more significant for the selection of a specific antenna type. For serving the microcellular environment, indoor as well as outdoor, microcellular antennas will be installed at relative low height (generally below roof-top level) in very flexible ways, using house/room walls, urban devices, ceilings, etc. as or for fixation. Following the very compact design of the Micro-BTS, the antenna installation (i.e. antenna plus connecting cables) should also remain visually non-intrusive and - even more important for indoor installations - should respect aesthetic aspects of the installation ambiance.
Figure 8: Mounting of an outdoor and an indoor microcellular antenna
The use of small, inconspicuous antennas is made possible due to the low transmit power of the Micro-BTSs. The antennas are generally equipped with N-type female connectors.
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3.4.1 Outdoor antennas The following table lists the commonly used outdoor antennas for microcellular applications. Antenna gain [dBi] HPBW
900 MHz
1800 MHz
360°
2 5
2 5
90°
8
8
65°
5 bidirectional
10
Table 2: Values for outdoor microcellular antennas The figures below show typical designs for outdoor microcellular antennas.
Figure 9b: Flat
Figure 9a: Omni antenna
Figure 9c: Bidirectional
Figure 9: Typical outdoor microcellular antennas
Alcatel
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3.4.2 Indoor antennas The following table lists the commonly used indoor antennas for microcellular applications. Antenna gain [dBi] Beam width
900 MHz
1800 MHz
360°
2
2 2 Multi-band antenna 7 Multi-band antenna
90° 8
8
Table 3: Values for indoor microcellullar antennas The figures below show typical designs for indoor microcellular antennas:
Figure 10c:
Figure 10b: Flat
Figure 10a: Omni, pole
Figure 10d: Omni antenna
Figure 10: Typical indoor microcellular antennas
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4. OPTIMIZED ANTENNA SYSTEMS In this chapter, two methods will be introduced which improve the effectivity of antenna systems.
4.1 Antenna diversity The purpose of using diversity is to reduce short-term fading effects, in order to achieve an acceptable level of performance (receiver sensitivity), instead of increasing the transmitted power or the bandwidth on the other side. The principle relies on the combination of two or more signals, containing the same information, which are at least partially decorrelated. If two signals of the same level are completely decorrelated, the probability that both signals will undergo the same depth of fade is only the square compared to the probability for one signal. Therefore the signal reliability is increased. The most commonly used diversity system is space diversity. The decorrelation is achieved by receiving the signals by means of two spatially separated (horizontal or vertical) antennas. If the separation of the antennas is at least 20 λ for horizontal separation (6 m for GSM 900 and 3 m for GSM 1800) and 15 λ for vertical separation (5 m for GSM 900 and 2.5 m for GSM 1800), a sufficient low correlation coefficient of 0.7 can be achieved. Space diversity systems use only one polarization direction.
Rx
Demod Deci- To BTS sion
Rxdiv Dualpolarized antenna
Demod
Singlepolarized antennas
Figure 11: Diversity systems In urban scenarios, where multipath propagation due to reflection and diffraction is predominant, the orientation of a single wave (and therefore the polarization) changes. Besides of signals with the original vertical polarization, there are also signals with horizontal polarization. Considering the fact, that a hand-held mobile or the antenna of a moving car is usually inclined to the vertical, there is a degradation due to signal loss using space diversity systems. Another diversity system, the polarization diversity system, recovers this signal energy loss by an additional orthogonal polarization. Decorrelation is achieved by using antennas with different polarizations (please refer to section 3.2, antennas with dual polarization).
Alcatel
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For urban and suburban application the achievable diversity gain is comparable for both types, the space and polarization diversity. Due to the less multipath propagation the gain in rural areas is generally lower. The polarization diversity gain of the rural area is even negligible, thus that the space diversity is the preferred type for rural areas. The diversity gain itself depends on a lot of parameters, like signal decorrelation and level, morphostructure, topology, antenna mounting, etc., and differs in the range of 2 dB up to 6 dB.
4.2 Antenna beam tilt In dense networks it is often advisable to lower the main lobe of the antenna in the vertical plane (downtilt) to ensure a reduction of interferences (see Figure 12). Hereby the main radiation lobe is adjusted below the horizontal by a specific angular displacement expressed in degrees (°).
Main beam direction
a
Ma in b eam
a
dire
ctio n
b
c
Figure 12: Illumination with and without antenna downtilt There are three kinds of beam tilt, the mechanical, the fixed electrical and the switchable electrical downtilt and when used, it must be applied for the Tx as well as for the Rx antennas.
Mechanical beam tilt is achieved by physically tilting the antenna out of the perpendicular by using a downtilt kit (brackets), factory-made specifically for that type of antenna. The following figure presents such a downtilt kit.
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Figure 13: Mechanical downtilt kit for antennas The advantages of this kind of beam tilting are the cost effectivity and the flexibility. A later adjustment of the vertical tilt is possible and therefore only one single antenna type may be used. The additional expenses for the mechanical downtilt are moderate and already included in the costs for the Alcatel antenna sets. The drawback is that the mechanical beam tilt has no effect on the side-lobe characteristics of the antenna (please refer to section 3.1, Figure 3). Providing a much more accurate and predictable means of controlling antenna coverage, the electrical beam tilt provides a distinct performance advantage; all directions/lobes (main, side and rear) are tilted to the same measure, controlling interferences of all directions. The electrical tilt is achieved by altering the phasing within the antenna. This technique produces beam tilt without physical movement of the antenna.
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τ =0 τ=t gle tilt an n w o D
τ = 2t τ = 3t
τ = delay time Figure 14: Electrical-downtilt technology
The electrical downtilt can be provided as fixed or switchable. The fixed one is tuned by the manufacturer, a later adjustment is not possible (except by means of an additional mechanical downtilt kit). This is disadvantageous because new antenna types have to be introduced, if other downtilts concerning a new network planning phase are required. This drawback can be avoided by using antennas with switchable electrical downtilt. By means of this advanced antenna type the electrical downtilt can be adjusted by a lever on the rear of the antenna. The antenna becomes very flexible with regard to the changing network conditions while maintaining the advantages of an electrical downtilt. On the other side this antenna type is rather expensive. The common mechanical downtilt-values range is from 2° to 10° (sometimes even more), depending on the vertical beam pattern of the actual antenna. Antennas with switchable electrical downtilt allow adjustments of the tilt angle from e.g. 3° to 15°, in one-degree steps. Both mechanical and electrical downtilt can also be combined. This results in a distinct range reduction in sidelobe direction (interference reduction). When choosing sector antennas with high electrical downtilt (6° to 8°) and applying mechanical-uptilt installation, an optimum coverage range in main-beam direction can be achieved.
Alcatel
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5. ANTENNA CONFIGURATIONS IN MOBILE NETWORKS In general there are many possibilities for antenna configurations. The antenna configuration depends on the antenna coupling level (stage between the antennas and the TRX level) of the BTS (Base Transceiver Station). This chapter gives an overview about the standard antenna configurations of the Alcatel EVOLIUM™ Base Station family.
5.1 EVOLIUM™ A9100 Base Station The antenna coupling level of the EVOLIUM™ A9100 Base Station is based on the separation between the combiner stage and a suitable antenna output stage. With this kind of modular construction the antenna coupling level can be adapted to a wide range of mobile-network requirements for antenna configurations, like reduction of attenuation losses (e.g. combiner loss) and minimization of the number of antennas per base station site.
Air interface Crosspolarized antenna
Singlepolarized antenna
Singlepolarized antenna
....
....
Antenna configurations
Antenna output stage
Antenna output stage
Antenna coupling level
.............
Combiner stage
TRX level
TRX
TRX
TRX
......
........................................
TRX
TRX
TRX
............. BCF level
Station unit module
EVOLIUMTM A9100 Base Station Abis interface
Abbreviations: BCF Base station Control Function; TRX Transceiver
Figure 15: Antenna configurations in conjunction
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with the EVOLIUM™ A9100 Base Station 5.1.1 Antenna diversity and air combining For antenna configurations with antenna diversity, which use air combiner technique, Alcatel provides the twin Receiver Front End (RFE) and duplexer stage. This antenna output stage connects two transmit signals to two antennas (or to one dual-polarized antenna) and distributes the received signals from each antenna to two receivers (for normal and the diversity reception). The module includes duplexers, LNAs and splitters. Each EVOLIUM™ A9100 Base Station cell is equipped with at least one such stage, which features high sensitivity, low attenuation and minimum intermodulation products. The following figure illustrates the ed antenna configurations of the twin receiver front end and duplexer stage.
Crosspolarized configuration
Antenna
Feeder TxA - RxA - RxdivB
TxB - RxB - RxdivA
Antenna
Singlepolarized configuration
Feeder
TxA - RxA - RxdivB
TxB - RxB - RxdivA
TxA - RxA - RxdivB
TxB - RxB - RxdivA
Duplexer Filter
Duplexer Filter
LNA
LNA
Splitter
Splitter
TxA
RxdivA RxA
RxdivB
Twin RFE and duplexer stage
TxB
RxB
Figure 16: Antenna configurations with one twin Receiver Front End (RFE) and duplexer stage for one cell
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The cross-polarized configuration has the advantage of minimizing the amount of antennas. Both configurations fulfil diversity aspects: By means of cross-polarized antennas the polarization diversity and with single-polarized antennas the space diversity is realized. One of this twin receiver front end and duplexer stage s the air combining (no additional combiner stage necessary) for up to two TRXs per cell. Under the name ‘low-loss configuration’ the EVOLIUM™ A9100 Base Station s two of these stages per cell, and air combining for up to four TRXs per cell is possible. 5.1.2 Configurations without antenna diversity For antenna configurations with only one single-polarized antenna, in order to minimize the number of antennas per site, Alcatel developed another antenna output stage: the RFE, duplexer and WBC stage. This module covers the functionalities of both twin receiver front end and duplexer stage as well as twin wide-band combiner stage.
Antenna
Feeder Tx
Rx
Duplexer Filter
Filter
LNA
WBC
TxA RxA
Duplexer combiner stage (ANs)
Splitter
TxB RxB
Figure 17: Antenna configuration with one RFE, duplexer and WBC stage for one cell This one-antenna configuration (for one cell) does not the diversity and air-combining aspects.
Alcatel
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5.2 EVOLIUM™ Micro Base Station Alcatel has developed a broad range of EVOLIUM™ Micro Base Stations to provide against any coverage needs. By using a modular concept the EVOLIUM™ Micro Base Stations are upgradable with regard to the amount of TRXs and cells. Figure 18 presents the different antenna configurations for one-cell applications.
Antenna
Antenna
Feeder
Feeder
3-dB coupler
1 TRX
2 TRXs
2 TRXs
Figure 18: Different antenna configurations with the EVOLIUM™ Micro Base Stations for one-cell applications With regard to the requirements of micro base stations, like consideration of aesthetic aspects of the installation ambiance (number of antennas), the antenna output stage of the EVOLIUM™ Micro Base Station contains a duplexer which combines the transmitter (Tx) and receiver (Rx) paths. With this technology only one antenna for one-TRX applications is needed. The high output power provided by EVOLIUM™ Micro Base Stations can be achieved by using air combining (no additional combiner losses) for the 2-TRX configuration. In this application either two standard micro antennas (single-polarized) or one dual-polarized antenna are used, ing the antenna diversity technology. In addition, Alcatel offers a one-antenna system for the 2-TRX configuration. The resulting benefits are reduced site acquisition constraints and lower antenna installation efforts and costs.
Alcatel
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6. MECHANICAL ANTENNA STRUCTURES Mechanical antenna structures serve two purposes: Grouping and accurate positioning of the antennas or antenna arrays, as laid out for generation of the desired pattern to illuminate the specified area, Mechanical interface and fixation of antennas or antenna arrays at the desired altitude to the carrier structure, which may be a tower, mast, building wall or roof top, etc.. The following paragraphs concentrate on a few, but more often used and most convenient realization variants for antenna mounts. In general, the mounting hardware kits are applicable for antennas of all frequency ranges (900 MHz, 1800 MHz, 1900 MHz) and for dual-band antennas including installation and grounding material. Important remark: The figures, pictures and realization examples shown below shall be considered only as a basic technical reference. The detailed technical realization for a specific mount must be traced to the respective materialization lists and has to be determined in co-operation with the installation department. Safety remark: Rigidity and stability of the mounts have to be checked/analyzed with respect to total weight, ice and wind load (in projects often mandatory to get official tower permit).
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6.1 Tower mounting for omni antennas If the tower or mast top is still available, the omnidirectional mounting as per Figure 19 will be the preferable solution (for the EVOLIUM™ A9100 Base Station). A minimum horizontal spacing of three or six meters between the poles bearing the Rx and Rxdiv antennas (please refer to section 4.1, antenna diversity) respectively between the poles carrying Tx and Rx antennas should be preserved in order to confirm a sufficient decoupling between the antenna branches. If the horizontal spacing is below the required minimum an additional vertical spacing of 0.5 m is necessary.
Omni antennas
Figure 19: Tower mounting for omni antennas
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6.2 Tower mounting for (directional) antennas By means of horizontally ing arms in conjunction with vertical carrier pipes, antennas can be positioned at the right spacing away from the tower and at the required altitude along the tower.
Horizontally ing arms
Vertical carrier pipe
Grounding
Figure 20: Tower mounting for antennas
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The ing arms are mounted to the tower legs by means of crossover plates. The type of tower leg (tubular or angular cross section) and its size determine the required type of crossover plate. The antenna s are fixed by the usual U-clamps to the vertical carrier pipe, which itself is mounted on both ends to the ing arms by pipe crossover clamps, the latter being part of the mounting assembly kit. The mounting assemblies can be used on towers with square or triangular cross section. Instead of the unidirectional (single-sector) configuration, also bi- or tri-sectored versions can be realized by additional mounting assemblies at the adjacent/opposite tower legs.
6.3 Pole mounting on roof top Especially in conjunction with tall buildings, small pipe masts or poles can be used for mounting and carrying antenna arrays. Usually each pole would carry one or max. two s in line, depending on the height and the wind load restrictions. The Alcatel antenna pipe masts are modularly upgradable. Therefore the masts are suitable for most applications.
Figure 21: Pole mounting on roof top
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Usually the pole is fixed by four heavy load bolts to the concrete roof surface. Tall poles are additionally propped by two bracons. The antenna itself is fixed by means of standard U-clamps to the pole. In some cases it is necessary to have an additional mounting layer between the roof and the pole mounting hardware. It protects the roof against direct mechanical effects of the mounting hardware and has the benefits, that the weight of the mounting hardware is distributed over a larger plain (stability aspects) and no fixing holes in the roof are necessary. The layer is set up with a corresponding amount of hexagonal pavings (according to the stability requirements) and an additional isolation between them and the roof. The hexagonal pavings are pre-manufactured steel frames which will be fixed together and will be replenished with concrete on site. This is an Alcatel option for the standard pole mounting.
6.4 Pole mounting on wall or parapet Also small pipe masts or poles are applied to mount directive antennas in front of house walls, house corners, roof edges or parapets. Adequately spaced, separate poles carry the corresponding antennas. Due to the high bending momentum at least two anchor plates are needed (please refer to Figure 22).
Anchor plates
Figure 22: Wall mounting
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7. FEEDER SYSTEM The feeder system presents the interface between the antennas and the base station. It includes the feeder cable, the feeder clamps, and essential accessories, like jumper cables and earthing kits.
7.1 Feeder cable The typical design of todays RF-transmission lines for mobile communications shows a dielectric of foam polyethylene with a very low dielectric loss. This dielectric does not age and is not hygroscopic. The inner conductors are copper wires. The outer conductors have an annular corrugation. By means of the dielectric the inner conductor is centered in such a manner that no relative movement between the conductors due to temperature variations or due to pulling can occur. The cables have abrasion-resistant black polyethylene outer jackets. If required, the cables can be supplied with flame-retarded low-smoke zero-halogen sheaths. Inner conductor
Outer conductor
Dielectric
Jacket
Figure 23: Feeder cable Feeder types and lengths depend on specific site and radio network planning requirements. The exact length will be determined after a site survey.
Alcatel
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7.1.1 Technical data for the feeders Inner conductor Dielectric Outer conductor Jacket
Type
Copper wire Low-density foam polyethylene (PE) Corrugated copper tube Polyethylene (PE), black
Minimum bending radius
Jacket (outer diameter)
Weight (m)
Recommended clamp spacing
Single bending
Repeated bending
LCF 1/2”
70 mm
210 mm
16 mm
0.35 kg
0.6 m
LCF 7/8”
120 mm
360 mm
28 mm
0.62 kg
0.8 m
LCF 1 5/8”
300 mm
900 mm
49.7 mm
1.5 kg
1.2 m
Table 4: Mechanical data for feeders
Operating frequency:
900 MHz
Type
Attenuation / 100 m
Commonly used for up to 1)
LCF 1/2”
6.6 dB
45 m
LCF 7/8”
4.0 dB
75 m
LCF 1 5/8”
2.6 dB
115 m
Operating frequency:
1800 MHz
Type
Attenuation/100 m
Commonly used for up to 1)
LCF 1/2”
10.3 dB
30 m
LCF 7/8”
6.0 dB
50 m
LCF 1 5/8”
4.0 dB
75 m
Operating frequency:
1900 MHz
Type
Attenuation/100 m
Commonly used for up to 1)
LCF 1/2”
10.6 dB
28 m
LCF 7/8”
6.3 dB
47 m
LCF 1 5/8”
4.2 dB
71 m
1) See next page
Table 5: Electrical data for feeders
Alcatel
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Remarks: All attenuation values given in the above tables are related to 50-Ω impedance type of feeder. Values were derived from ‘attenuation-vs.-frequency’ tables provided by manufacturer of feeders through linearization between fixed, measured samples. Consequently, above statements should not be regarded as highly accurate, measured values at a specific operating frequency (indicated in the headers of tables). 1)
Column ‘Commonly used for up to’ in table 5 is given in order to ensure feeder losses below or equal to 3.0 dB (connector and jumper cable losses not included). These ‘upper limits’ in feeder length should be considered as guidelines only; rounded down to the closest integer value in meters.
Deviations from ‘recommended length’ values are possible, but must be considered in the radio network planning process after discussion with the radio network planning team.
7.2 Feeder clamps The feeder clamps mount the feeder cable to the mounting object, e.g. a mast or a pole. Each cable clamp includes a twin-cable run for the common fixture of two feeders.
1. Cable clamps 3. Double bearing 2. Antenna cable 4. Counterpart 5. Anchor tape
Figure 24: Feeder installation
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Alcatel GSM Antenna Systems - Product Description
7.3 Feeder accessory sets Alcatel provides different accessory sets depending on the feeder type. These accessory sets contain earthing kits, wall glands, connectors, isolation material and, if required, the jumper cable between feeder and antenna. The standard delivery consists of three earthing kits per feeder cable. An additional lightning protection, by means of a lightning rod at the top of the building or mast and an EMP device (ElectroMagnetic Protection, already included in the outdoor BTS) is available. 7.3.1 Jumper cables With regard to the restricted minimum bending radius of the standard LCF feeder cable (please refer to section 7.1.1, technical data data for feeders) a higher flexible connecting feeder cable, the so-called jumper cable, is required. This jumper cable allows an accurate mounting and connection of the feeder cable with the antenna or the BTS in areas that require tight bending and extremely small bending radii. Particularly for the 7/8“ and the 1 5/8“ feeder cables these jumper cables are essentially.
Feeder type
Jumper cable Jumper cable Jumper cable
Cable length
Cable diameter
Total attenuation
m 2 3 5
mm 13.5 13.5 13.5
900 MHz 1800 MHz 0.32 dB 0.42dB 0.42 dB 0.57dB 0.63 dB 0.88dB
Min. bending radius mm 30 30 30
Cable type
HCF 1/2" CuH HCF 1/2" CuH HCF 1/2" CuH
Table 6: Jumper cables
Alcatel
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Date 14/09/98
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Alcatel GSM Antenna Systems - Product Description
Figure 25: Flexible jumper cable 7.3.2 Connectors One possible connection between feeder cable and jumper cable is shown in the following illustrations. The connecting point must provide a perfect and long-term mechanical and electrical connection, which is also resistant against environmental influences. These conditions are met due to the construction of the components, and no further protection of the connecting point is required.
Figure 26: Connection between feeder and jumper cable The connectors are generally 7/16 connectors with an outer-conductor diameter of 16 mm. This system is used in all cases where robust and precise connections are required. The mating being screw thread and sealed by a face ring. The feeder cable is equipped with female, the jumper cable with male connector as a standard.
Male connector
Female connector
Figure 27: 7/16 connectors 7.3.3 Earthing of the feeder cable The feeder cable earthing kits ground the feeder cable. They are mounted in defined distances over the total cable length in order to protect overvoltages on the feeder cable. The earthing kit complies with all relevant standards and is resistant to all relevant environmental influences. Figure 28 presents a possible earthing kit. The earthing body consists of stainless steel with vulcanized Ethylene-Propylene-Caotchouc. The grounding wire (16 mm2, both ends terminated with cable eyes) is fixed with stainless steel screws to the surface. This construction of a preassembled grounding kit enables a quick and accurate mounting.
Alcatel
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Date 14/09/98
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Alcatel GSM Antenna Systems - Product Description
Figure 28: Cable earthing At least three earthing points are recommended in order to achieve a good grounding result: - One near the top of the feeder cable, - One where the feeder cable leaves the tower or mast, - One where the feeder cable enters the building or shelter, - In areas of high lightning activities one on top of that every 20 m. The following figure illustrates the earthing of the feeder cable at the cable entry of a building.
Figure 29: Feeder earthing at cable entry (wall gland)
Alcatel
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Date 14/09/98
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Alcatel GSM Antenna Systems - Product Description
7.4 Feeder systems for microcellular applications As already mentioned in section 3.4, microcellular antennas, the antenna installation (e.g. antenna and connecting cables) for a Micro-BTS should consider the aesthetic installation aspects. Figure 30 outlines the simple RF installation of the Micro-BTS. For the connection between the Micro-BTS and the antenna, a factory-made feeder cable is used. Additional earthing, as shown, is needed only in case of outdoor installation and in mixed configurations, when the BTS is installed indoor and the antenna is mounted outdoor.
Microcellular antenna
Micro-BTS unit
N-connector
Earth clamps AC + data interface N-connector Cable channel (to and ’hide’ the cable) Factory-made feeder cable (optional lengths: 5 m and 15 m) Earthing kit (required for outdoor installation)
Figure 30: Example of a microcellular antenna installation The factory-made feeder is a highly flexible low-loss cable, already equipped with N-type male connectors on both ends. If necessary, the cable length can be cut to the specific needs on site and the connector can be reassembled.
Feeder type
MIC FEED 5 MIC FEED 15
Cable length
Cable diameter
Total attenuation
m 5 15
mm 13.5 13.5
900 MHz 1800 MHz 0.62 dB 0.88 dB 1.68 dB 2.43 dB
Min. bending radius mm 30 30
Cable type
HCF 1/2" CuH HCF 1/2" CuH
Table 7: Feeders for microcellular applications In case of microcellular antenna feeder installation, cable tubes or plastic cable channels/ducts are used. This allows to hide the (black-coloured) cable inside the cable channel. Besides this, the use of cable channels enables an exact and rapid fixation.
Alcatel
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Date 14/09/98
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Alcatel GSM Antenna Systems - Product Description
8. POWER DIVIDERS Power dividers (or power splitters) can be used to connect two, three or four antennas to a single feeder cable. Two main applications for power dividers exist: Creation of omni-directional antenna patterns by using directional antennas, when the top of a mast or tower is not accessible (radial, skew or quasi-omni configuration), Feeding of two directional antenna sets by a single BTS (cell) for road coverage.
Quasi-omni configuration
4-to-1 power divider 6 dB ‘distribution loss’
To the BTS
Figure 31: Typical application of power dividers The Power Divider (PD) can be combined with the tower-mounted amplifier equipment (TMA). To combine antennas for particular radiation patterns or for an indoor distribution network, power dividers with the following features are available: Low-loss coaxial-line transformation, High power rating, Indoor and outdoor use, Very small dimensions.
Alcatel
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Date 14/09/98
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Alcatel GSM Antenna Systems - Product Description
The technical data of symmetrical power dividers are given in the tables below:
Electrical specifications Divider type Distribution loss
[dB]
Insertion loss
[dB]
2-way
3-way
4-way
3
4.8
6
< 0.05
VSWR
< 1.1
Impedance
50 Ω
Mechanical specifications [mm]
Dimensions W x H x D
210 x 80 x 80
160 x 80 x 80
Connector type
285 x 80 x 80
7/16’’ female
Material
Case: Aluminum Inner conductor: Brass
Mounting
Bracket included for wall mounting: For tubular-mast mounting clamps with diameter between 50 mm and 105 mm
Table 8: Technical data for power dividers For an especially adapted indoor distribution network, there are also asymmetrical power dividers available.
End of Document
Alcatel
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Reference 3DC 21019 0003 TQZZA
Date 14/09/98
Edition 03
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