Guide to CDMA2000 Base Station Antenna Type SelectionV1.0

Huawei Technologies Co., Ltd.

Radio Network Planning Dept.Document numberProduct versionConfidentiality level

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Guide to CDMA Base Station Antenna Type Selection

(For internal use only)

Prepared by:Date:2002-01-04

Reviewed by:Date:2002/02/07

Reviewed by:Date:yyyy/mm/dd

Approved by:Date:yyyy/mm/dd

Huawei Technologies Co., Ltd.All Rights ReservedRevision record

DateRevision versionDescriptionAuthor

2002/07/061.00Initial transmittalHe Qun

Table of Contents61 Overview

61.1 Antenna Types

61.2 Main Technical Performances of Antenna

61.2.1 Working Frequency Bands

71.2.2 Antenna Gain

71.2.3 Antenna Pattern

91.2.4 Polarization Mode

101.2.5 Downtilt

101.2.6 Voltage Standing Wave Ratio (VSWR)

101.2.7 Port Isolation

101.2.8 Power Capacity

111.2.9 Antenna Input Interface

111.2.10 Passive Inter-Modulation (PIM)

111.2.11 Antenna Size and Weight

111.2.12 Wind Load

111.2.13 Working Temperature and Humidity

121.2.14 Lightning Protection

121.2.15 3-Proof Capability

132 Principles of Antenna Type Selection

132.1 Principles of Selection of Antenna Working Frequency Bands

132.2 Principles of Selection of Antenna Gains

142.3 Principles of Selection of Antenna Beam Widths

142.3.1 Relationship between Beam Width and Gain

152.3.2 Principles of Selection of Beam Widths

162.4 Principles of Selection of Polarization Modes

172.5 Principles of Selection of Downtilt Modes

172.5.1 Comparison between Mechanical Downtilt and Electronic Downtilt

192.5.2 Comparison of Function between Preset Downtilt and Null fill-in

192.5.3 Downtilt Planning and Optimization

202.6 Principles of Selection of Front-and-Back Ratio

202.7 Principles of Selection of Antenna Sizes

202.8 Principles of Selection of Antenna Impedances

212.9 Principles of Selection of Antennas for Special Places

223 Selection of Antenna Types for Different Application Environments

223.1 Selection of Antennas for Urban Base Station

233.2 Selection of Antennas for Country Base Stations

243.3 Selection of Antennas for Suburban Base Stations

243.4 Selection of Antennas for Highway Coverage Base Stations

253.5 Selection of Base Station Antennas for Mountainous Coverage

263.6 Selection of Base Station Antennas for Offshore Coverage

263.7 Selection of Base Station Antennas for Tunnel Coverage

273.8 Selection of Base Station Antennas for Indoor Coverage

294 Main Technical Indices of Antennas Certificated by Huawei

305 Main Antennas not Certificated

305.1 Electronically Adjustable Antenna

305.2 Intelligent Antenna

32Appendix 1: Main Antenna Types Optional for Urban Environment (800MHz)

32Appendix 2: Main Antenna Types Optional for Rural Environment (800MHz)

33Appendix 3: Main Antenna Types Optional for Highway Application Environment

33Appendix 4: Main Antenna Types Optional for Mountainous Application Environment

33Appendix 5: Main Antenna Types Optional for Offshore Application Environment

33Appendix 6: Main Antenna Types Optional for Tunnel Application Environment

34Appendix 7: Main Antenna Types Optional for Indoor Application Environment

34Appendix 8: Website of Antenna Supplier Certificated by Huawei

Guide to CDMA2000 Base Station Antenna Type SelectionKey words: CDMAbase stationantenna type selection antenna pattern

Abstract: From the approach of network planning, this document first gives a description of the main characteristics and selection methods of antennas, then introduces the selection principles and recommendations of antennas that are used in different environments, and finally gives all the main characteristics data of antennas that have been certificated by Huawei.

List of abbreviations/acronyms:List of references: List of references

NameAuthorNumber

Issue dateQuery place or channel

Publishing organization

Guide to GSM Base Station Antenna Type SelectionTao Maodi and He QunSUPPORT Web site

1 OverviewAn antenna is an interface between a radio transceiver and the external media. An antenna can both transmit and receive radio waves: when transmitting radio waves, it converts high-frequency currents into electromagnetic waves, and electromagnetic waves into high-frequency currents when receiving radio waves.

1.1 Antenna Types

Like antennas for GSM base stations, antennas used for CDMA2000 can also be divided into omni-antennas and directional antennas according to the radiation directions.According to polarization modes, there can be: vertical polarized antenna (also called unipolarization antenna) and cross polarized antenna (also called bipolarization antenna). The above two modes are both linear polarization modes. Usually, circular polarization and elliptic polarization antennas are not used.According to the outward looks, there can be: whip antenna, flat plate antenna and cap antenna.Now, lets come to an isotropic antenna before going on our description of antenna-related theory. As a theoretical model, an isotropic antenna does not exist in reality. It hypothesizes an antenna as a radiation point source, which serves as the center from which energy evenly radiates around in the form of an electromagnetic field, as a spherical wave.In addition, an omni-directional antenna does not mean that it has no direction. It is only omni-directional horizontally, but it is directional vertically. An omni-directional antenna and an isotropic antenna are of two different concepts.A half-wave dipole is a fundamental unit of the main antenna of a CDMA2000 base station. A half-wave dipole has an advantage of high efficiency in energy conversion.1.2 Main Technical Performances of Antenna

The main technical performances of an antenna are: working frequency bands, gain, polarization modes, lobe width, preset downtilt, downtilt mode, downtilt adjustment, front/back suppression ratio, minor lobe suppression ratio, null fill-in, return loss, power capacity, impedance, third order inter-modulation, etc. The main mechanical performances include antenna size, weight, antenna input interface and wind load.1.2.1 Working Frequency Bands

There are three frequency bands available for a CDMA2000 base station. They are: 450MHz, 800MHz and 1900MHz. At present, this document only describes the principles of antenna selection for the 800MHz frequency band of the CDMA base station, leaving the other bands for later description.Frequency of the 800MHz CDMA2000/IS-95 system is:Forward: 869.025 to 893.985MHz

Reverse: 824.025 to 848.985MHz

1.2.2 Antenna GainAn antenna is a passive device. The concept of its gain is different from that of an ordinary power amplifier gain. A power amplifier has the function of energy amplification, whereas an antenna does not increase the energy of the signals it radiates, but it concentrates the energy to a certain direction by combining antenna dipoles and changing the feeding mode. Indicating the energy concentrating capability of an antenna in a certain direction, the gain is one of the important indices of an antenna. There are usually two units that represent the gain of an antenna: dBi and dBd. The relationship between the two is: .dBi is defined as a relative capability of energy concentration of an actual directional antenna (including omni-directional antenna) in relation with an isotropic antenna, with the i standing for Isotropic.dBd is defined as a relative capability of energy concentration of an actual directional antenna (including omni-directional antenna) in relation with a half-wave dipole antenna, with the d standing for Dipole.The relation between the two types of gain is shown in the following figure:

Figure 1 Relation between dBi and dBd

The gain of an antenna in related not only with the number of dipole units, but also with the width of horizontal beam and the width of vertical beam.1.2.3 Antenna PatternThe graph of electromagnetic fields, radiated by an antenna, that are distributed with the angular coordinates at a fixed distance is called an antenna pattern. An antenna pattern presented in radiation field strength is called a field strength pattern, an antenna pattern presented in power density is called a power pattern, and an antenna pattern presented in phase is called a phase pattern. In mobile communication engineering, power patterns are usually used.An antenna pattern is a 3-dimensional graph, but it is usually presented in a pattern within two main planes that are perpendicular to each other, and such a pattern is called a plane pattern. Usually it is called vertical pattern or horizontal pattern. In respect to a horizontal pattern, there are omni-antennas and directional antennas, and also some special directional antennas, such as heartlike antennas and 8-like antennas.

The directivity of an antenna is obtained by means of change of the dipole arrangement and dipole feed phase, which is very much similar in principles to optical interference effect. So the energy may be strengthened in some directions, and weakened in some others, i.e. there may be lobes (or beams) and null points. The lobe with the strongest energy is called major lobe, and the second strongest lobes above and below it are called the first minor lobes, and so on and so forth. In respect to a directional antenna, there are also back lobes. The horizontal and vertical patterns of a directional antenna are shown below.

Figure 2 Horizontal and vertical pattern of a directional antennaBeam width (also called half power angle) includes horizontal beam width and vertical beam width. They are defined respectively as the beam width between two points with half of the power (3dB) dropping down in the horizontal and vertical directions in relation with the strongest radiation direction. The common horizontal beam widths of base station antennas are 360, 90, 65, 60, etc., and the vertical beam widths available are 6.5, 7, 10, 16, etc.

There is no narrow beam antenna of 800MHz band appropriate for a 6-sector configuration yet at present.Front/back suppression ratio means the ratio between the radiation strengths of signals in the major lobe direction and the back lobe direction of an antenna. The difference between the minor lobe level and the greatest beam in the backward 18030 of an antenna is presented in positive value. Generally, the forward/backward suppression ratio of an antenna is in the range of 18 to 45dB. For a densely populated urban area, an antenna with relatively greater forward/backward suppression ratio should be preferentially used.Zero stuffing: when shaped-beam design is adopted in the vertical surface of base station antennas, the first zero point of the lower secondary lobe need to be stuffed without any obvious depth, so as to make the radiant level more uniform within the service area. For the high gain antennas, it is especially necessary to adopt zero point stuffing technology to effectively improve nearby coverage, because the vertical half power angle of these antennas is more narrow. In usual cases, if zero depth greater than -26dB in relation to main beam, this means the antenna has zero stuffing; some suppliers use percentage to represent it, for example, the antenna zero stuffing is 10%, the relation between these two representative methods may be expressed by:

Y dB20log(X%/100%)

e.g.: zero stuffing 10%, that is, X=10; Represented by dB: Y=20log(10%/100%)=-20dB

Upper minor lobe suppression: For a microcell cellular system, in order to enhance the frequency multiplex efficiency and reduce the co-channel interference to adjacent cells, during base station antenna beam shaping, those minor lobes that aim at the interference area should be lowered as much as possible, and the D/U value (ratio of strengths of desired and undesired signals) should be increased, and the level of the upper minor lobe should be less than -18dB. There is no such a requirement for macrocell base station antennas.1.2.4 Polarization Mode

Polarization is a radiation characteristic describing the vector space direction of electromagnetic wave field strength. If not otherwise specified, the space direction of an electric field vector (and the electric field vector of the greatest radiation direction of the antenna at that) is taken as the polarization direction of an electromagnetic wave.

An electromagnetic wave whose electric field vector has an unchanged space direction at any time is called a linear polarization wave. Sometimes, with the ground as a reference, an electromagnetic wave whose electric field vector direction is in parallel with the ground is called a horizontal polarization wave, and that which is vertical with the ground is called a vertical polarization wave. The direction of an electric field vector will not be fixed sometimes. An electromagnetic wave whose electric field vector end draws a circle as its trace is called a circular polarization wave; and if the trace is an ellipse, the wave is called an elliptic wave. Both an elliptic polarization wave and a circular polarization wave have handedness.

Electromagnetic waves of different frequency bands may be transmitted in different polarization modes. A mobile communication system usually adopts the vertical polarization mode, a broadcast system usually adopts the horizontal polarization mode, and elliptic polarization is usually used for satellite communication.

An antenna of CDMA2000 is in two polarization modes: directional unipolarization and directional bipolarization. The essence of the two is linear polarization. A directional bipolarization antenna uses polarization diversity to reduce the influence of multi-path fading in a mobile communication system, so as to enhance the quality of signal receiving of a base station. Antennas of two types: 0/90 and 45/-45 are available. In a UHF band, a horizontal polarization wave is not as satisfactory as a vertical polarization wave when transmission effect is concerned. So a cross polarization antenna of 0/90 is rarely used at present.1.2.5 DowntiltAntenna downtilt is an important and frequently used means to strengthen the signal levels of the main service area and reduce interference of other cells. Antenna downtilt usually includes mechanical downtilt and electronic downtilt. In the mechanical mode, one can set a downtilt angle via adjusting the antenna support to lower the antenna to a certain position; while in an electronic mode, the downtilt angle is controlled by means of changing the phase of the antenna dipole. Of course, the electronic mode can be used in combination with the mechanical mode.Usually, the downtilt angle of an electronic downtilt antenna is fixed, i.e. the so-called preset downtilt. An antenna of the latest technology is an adjustable electronic downtilt antenna, which is usually called electronic-adjusted antenna, to be distinguished with the former antenna.1.2.6 Voltage Standing Wave Ratio (VSWR)In the base station antenna of the mobile communication cellular system, the maximum value of VSWR should be less than or equal to 1.5:1. If represents the antenna input impedance, and the antenna nominal characteristic impedance, then the reflection factor will be , where, is 50 ohm. The matching characteristic of the port can also be presented in return loss, , when the VSWR=1.5:1, the R.L.= 13.98dB.When the antenna input impedance is inconsistent with the characteristic impedance, the reflection wave and incident wave generated are overlaid on the feeder to form standing waves, and the ratio between the maximum and minimum values of their adjacent voltages is VSWR.. If the VSWR is too great, the communication distance will be shortened, and the reflection power will return the power amplification part of the transmitter, which is liable to burn down the power amplification tube. As a result, the normal operation of the communication system may be adversely influenced.1.2.7 Port Isolation

In respect to multi-port antennas, such as directional bipolarization antenna, dual-frequency band directional bipolarization antenna, when a port is used for receiving and sending alike, the isolation between ports should be greater than 30dB.1.2.8 Power Capacity

It means the average power capacity. An antenna includes coupling facilities of matching, balance, phase shift, etc. The power it bears is limited. Taking the actual maximum input power of the base station antenna into consideration (single carrier power 20W), if one port of the antenna can input 6 carrier waves at the maximum, then the input power of the antenna will be 120W, so the power capacity of a single port should be greater than 200W (in an environment temperature of 65).1.2.9 Antenna Input Interface

In order to improve the reliability of passive inter-modulation and radio frequency relation, the 7/16DIN-Female will be used for a base station antenna interface. Prior to using an antenna, the port should be protected with a cover to prevent oxide compounds or impurities.1.2.10 Passive Inter-Modulation (PIM)

Passive inter-modulation refers to the inter-modulation effect caused by the non-linearity of passive parts like connectors, feeders, antennas, filters, etc. themselves when these parts work under the circumstance of large power signals of multi-carrier frequencies. Generally, passive parts are considered as linear, but passive parts under a large power circumstance have more or less non-linearity. The non-linearity is caused by the following factors: different metal contacts; contact surfaces of the same material are not smooth; the connection is not tight and there is magnetic material existent, etc.

The existence of inter-modulation product causes interference to the communication system, especially the inter-modulation product that has fallen into the receiving zone will impose a serious adverse influence on the receiving performance of the system. Therefore, strict requirements are stipulated on the passive parts like connectors, cables, antennas, etc. It is required: the passive inter-modulation index of connectors should be-150dBc, the passive inter-modulation index of cables should be-170dBc, and the passive inter-modulation index of antennas should be-150dBc.1.2.11 Antenna Size and Weight

For the convenience of antenna storage, transport and installation, and its security, on condition that various electrical indices are satisfied, the size of an antenna should be as small, and the weight as little as possible.At present, the operators have become more and more particular about the size, weight and outlook of antennas, so when selecting antennas, we should be concerned not only about the technical performance indices, but also about these non-technical factors. For urban base stations, preference should be given to antennas light in weight, small in size and pleasant in look, but not so for base stations in the suburbs and townships.

1.2.12 Wind Load

As base station antennas are usually installed on buildings and towers, and particularly in coastal areas the wind speed is usually high al the year round, so it is required that an antenna should work normally when the wind speed is 36m/s, and remain undamaged when it is 55m/s.An antenna itself can stand a strong wind. In areas with strong winds, an antenna is usually damaged due to factors of its support or the tower it is attached to, so antennas with small surface area should be selected for these areas.1.2.13 Working Temperature and Humidity

A base station antenna should work normally under a range of environmental temperatures of -40C-+65C and a range of relative humidity of 0-100%.

1.2.14 Lightning Protection

Direct DC grounding is required for all the radio frequency input ports of a base station.1.2.15 3-Proof Capability

A base station antenna should have a 3-proof capability, namely, humidity-proof, salt fog-proof and mould-proof. A base station omni-antenna should allow upside installation, and should satisfy the 3-proof requirement as well.2 Principles of Antenna Type Selection 2.1 Principles of Selection of Antenna Working Frequency Bands

Antennas should be selected according to the frequency bands they use. To reduce the engineering cost and purchasing cost, on condition that the technical index requirements are satisfied, broad frequency band (different from double frequency band, i.e., with no feeder port added) antennas, such as broad frequency band antennas of 800MHz and 900MHz frequencies, and broad frequency band antennas of 1800MHz and 1900MHz frequencies, should be selected.2.2 Principles of Selection of Antenna Gains

Usually, the gain range of a GSM base station antenna is: 2dBi to 11dBi. And 2dBi, 9dBi, 11dBi, etc. are available.While the gain range of a directional antenna is usually: 3dBi to 22dBi. And 3dBi, 8.5dBi, 10dBi, 13dBi, 15dBi, 15.5dBi, 17dBi, 18dBi, 21dBi, 22dBi are available.Low gain antenna When an antenna has a low gain, its coverage and interference can be better controlled. Usually it is used in combination with a micro base station and micro cells, mainly for indoor coverage and outdoor blind spot compensation, for instance, the back of a building, a new residential area, a new professional market, etc. Antennas of this type are small in size, easy to install. For instance, a Yagi antenna can be used at the inner sides of a tunnel, this type of antenna features a narrow beam, and good directivity.

Medium gain antenna A medium gain antenna is appropriate for urban areas. On one hand, the volume and dimensions of a medium gain antenna are appropriate for urban areas, on the other, in a relatively shorter coverage radius, the signals are more even because of a greater vertical beam width. The signals covered by a medium gain antenna in the neighboring sectors are more reasonable in terms of intensity than those by a high gain antenna. At the beginning of the construction stage, since the coverage radius of a base station is relatively long (longer than 1 km), directional antennas with relatively high gain can be selected for use. As network construction is going on, density of base stations will get greater while the coverage radius gets smaller. Now directional antennas of lower gain should be used, and preset downtilt antennas or electronically adjustable antennas should be taken into consideration.High gain antenna High gain antennas are usually used for broad coverage, such as coverage along expressways, railways, tunnels, long and narrow areas. This type of antenna features narrow lobe width and deep zero spot, so when the antenna is hung high, make sure to select an antenna that has null fill-in or preset electronic downtilt, so as to avoid the zero effect at the near end of the coverage. This type of antenna usually has a relatively large volume because of multiple dipoles, so make sure if it is feasible to install it. For example, it may be inappropriate to install an antenna of this type at the mouth of a tunnel. Besides, attention is drawn to the wind load, especially in coastal areas where are strong winds. And the cost of this type of antennas is relatively high.2.3 Principles of Selection of Antenna Beam Widths

2.3.1 Relationship between Beam Width and Gain

An antenna is a facility where energy is concentrated. The strengthening of radiation in a certain direction means the weakening of radiation in another direction. Usually, the gain of an antenna can be enhanced by means of reduction of horizontal lobe width to strengthen the radiation intensity in a certain direction. With the antenna gain fixed, the horizontal lobe width is inversely proportional to the vertical lobe width. The relation can be presented as follows:

Where, Ga is the antenna gain, in DBi; is vertical beam width, in degree; is horizontal beam width, in degree.According to the above formula, when we know the gain and horizontal beam width of a certain antenna, we can estimate the vertical beam width.For instance: an omni-antennas gain is 11 dBi, the horizontal beam width is 360, then its vertical beam width will be:.

Due to the difference between the design and the production technology, the actual vertical beam width of an omni-antenna will often be smaller than the above calculation. The little the difference between the two, the better the design will be.

The relationship among the antenna gain, vertical beam width and horizontal beam width is shown in the following figure:

Figure 3 Relation between antenna gain and beam width

It can be seen that when the antenna gain is little, the vertical and horizontal beam widths are usually great; and when the antenna gain is big, the vertical and horizontal beam widths will usually become small.

In addition, the antenna gain depends on the number of the dipoles. The more the dipoles, the higher the gain, and the antenna diameter (the effective receiving area of the antenna) will also get bigger. In respect to an omni-antenna, when the gain increases by 3dB, the antenna length will increase by one time. So the gain of an omni-antenna will not be larger than 11dBi, and the antenna length in this case will be about 3 meters (in terms of an 800MHz antenna).When the antenna gain is certain, the antenna horizontal beam width is inversely proportional to the vertical beam width.

2.3.2 Principles of Selection of Beam Widths

Selection of beam widths includes selection of horizontal beam width and vertical beam width, and the two are interrelated. The main basis for the selection is the specific coverage requirements and interference control. For the sake of interference control, the horizontal beam width of antennas for urban areas should not be greater than 65. Antennas of 90 and up will cause contamination of multiple PNs (more than 3 PNs) that have similar pilot intensity due to the overlarge coverage. Whereas in the suburbs and the countries, there is a very little probability of existence of multiple PNs that have similar pilot intensity. It is a main consideration in planning optimization that a cell should provide as large coverage as possible. Antennas with a horizontal beam width of 90 can be selected to strengthen the coverage over the peripheral areas.

Once the antenna gain and the horizontal beam width are selected, the vertical beam width is generally determined. But, antennas with a very wide vertical beam, say 20 or so, will be selected sometimes, for instance, the base station is set up on a hill, while the areas to be covered are somewhere down the hill, then coverage in the vertical direction should be taken into consideration. Generally, the narrower the vertical lobe, the higher antenna gain and better directivity, but there will be more obvious null depth effect. In this case, make sure to adopt preset downtilt or null fill-in technology for the problem. But, the narrower the vertical lobe, the longer and heavier the antenna will be, so how the antenna will be installed should be taken into consideration, and the antenna will be more expensive.Generally, the maximum beam width in the horizontal plane of a directional bipolarization antenna should not be greater than 90 degrees.2.4 Principles of Selection of Polarization Modes

Comparison between a directional unipolarization antenna and a directional bipolarization antenna: From the transmission point of view, a mobile phone set that is vertical to the ground will be easier to match with vertical signals, so a vertical directional unipolarization antenna will have a better covering effect than a non-vertical polarization antenna. This will all the more be the case when an open mountainous area or plain country villages are concerned. Experiments show that in open mountainous areas or plain rural areas, the covering effect of vertical polarization antennas is better than that of bipolarization antennas (45). However, in the urban areas, as there many buildings, and metallic objects within and without the buildings will make the polarization rotate, so there will be little difference between a unipolarization antenna and a 45 directional bipolarization antenna in covering capability.From the receiving point of view, as two directional unipolarization antennas are needed to realize diversity receiving, whereas only one directional bipolarization antenna will be enough for the purpose, so more space will be needed for installation of directional unipolarization antennas, and more maintenance will be needed for directional unipolarization antennas than for directional bipolarization antennas. As to space diversity gain and polarization diversity gain, there is little difference between them. Generally, the space diversity gain is 3.5dB or so. From the point of view of antenna size, in a directional bipolarization antenna, sufficient isolation is guaranteed even if the dipoles in different polarization directions are overlaid, so the size of a directional bipolarization antenna is not larger than that of a directional unipolarization antenna.Comparison between a 45/-45 directional bipolarization antenna and a 0/90 directional bipolarization antenna: All the antenna subsystems in the 45/-45 mode can be used as transmission signals, whereas a 0/90 directional bipolarization antenna only uses vertical polarization dipoles as transmission signals. Experiences show that the efficiency of signal transmission with a horizontal polarization antenna is much lower than with a vertical polarization antenna. In an ideal free space (suppose the mobile set receiving antennas are in vertical polarization mode), the covering capability with transmission by means of vertical polarization dipoles is stronger by about 3dB than that with transmission via 45/-45. In an actual application environment, however, there are multi-path transmissions. On the receiving points, the above-mentioned difference will basically disappear through average in statistics of multi-path signals. Various experiments also show that this is true. But the difference still exists in open plains, though the specific value is not available yet from experiments. In a word, there is little difference between the two polarization modes in actual application. At present, antennas of 45/-45 quadrature polarization are often seen in the markets.

It is recommended that in the urban area, directional bipolarization antennas are to be selected preferentially, while in the suburbs and the country; directional unipolarization antennas are to be selected preferentially.2.5 Principles of Selection of Downtilt Modes

2.5.1 Comparison between Mechanical Downtilt and Electronic Downtilt

Three downtilt modes are available: mechanical, electronic (also called preset downtilt) and electronically adjustable downtilt (also called adjustable electronic downtilt). When adjusting the downtilt of an electronically adjustable antenna, the antenna itself is not moved, the radiation energy is diverged from the direction of zero degree via adjusting the phase of the antenna dipoles via electric signals and by means of modifying the synthesized component field strength. The field strength of the antenna in every direction is increased or reduced simultaneously. This ensures that when the downtilt angle is changed, the shape of the antenna pattern is changed very little, and the horizontal half power width is independent of the downtilt angle. But in the case of a mechanical antenna, when the downtilt angle is being adjusted, the antenna itself will be moved. The downtilt angle cannot be changed unless the position of the support at the back of the antenna is adjusted. When the downtilt angle is relatively large, signals in the direction that is vertical to the antenna major lobe are hardly changed (though the covering distance in the major lobe direction is changed obviously), so the antenna pattern is seriously deformed, and the horizontal beam width increases as the downtilt angle increases. The principle of a preset downtilt antenna is similar to that of an electronically adjustable antenna, but the downtilt angle of the former is not adjustable (yet it can be adjusted by mechanical means).The advantages of an electronically adjustable are: When the downtilt angle is very large, the covering distance in the antenna major lobe direction will obviously become shorter, the antenna pattern shape is changed little, hence call loss is reduced, and interference also reduced. But in the case of mechanical downtilt, the pattern will be deformed. The larger the downtilt angle, the more serious the pattern is deformed. So it will be hard to control interference. Changes of antenna patterns in the two different modes are given below. Of course, it is related with the antenna vertical beam width.

Mechanical downtilt

Electronically-adjustable downtilt

Figure 4 Changes of horizontal antenna patterns with different downtilt anglesIn addition, electronically adjustable downtilt is different from mechanical downtilt when the influence on the back lobe is concerned. Electronically adjustable downtilt makes it possible to control the influence on the back lobe, whereas mechanical downtilt may make the influence on the back lobe extended, as shown in the following figure:

Peak value of back lobe

Peak value of major lobe

Horizontal antenna pattern

Mechanical downtilt

Electronically adjustable downtilt

Rotation axis

Figure 5 Different influences on the back lobe by different downtilt modes

When a mechanical downtilt angle is relatively large, the radiation signals of the antenna may be transmitted into the high buildings in the back direction via the back lobe, causing undesired interference.

What is more, if adjustment of downtilt angles is needed during the optimization, management and maintenance of a network, and if electronically adjustable antennas are used, no close down will be necessary for the whole system. In this case, dedicated test devices of mobile communication can be used to monitor the adjustment of the downtilt angles to ensure an optimal value. In respect to the step degree of downtilt angle adjustment, it is 0.1 degree with an electronically-adjustable antenna, but it is 1 degree with a mechanically-adjustable antenna. So, electronically adjustable antennas have higher accuracy and more satisfactory effect. After installation, during the downtilt adjustment of an electronically adjustable antenna, the maintenance personnel do not bother to be present up the place where the antenna is placed, but adjust the downtilt on the ground instead, and also can perform an remote monitored adjustment to the base station antennas on high mountains or in outlying areas. As to mechanical antennas, the downtilt adjustment requires that the cell should be closed down, and you cannot monitor while adjusting the downtilt. There is certain deviation of the mechanical downtilt angle from the actual optimal downtilt angle, as the former is a theoretical value derived via computer simulation analysis software calculation. In addition, it is troublesome to adjust a mechanical antenna, for maintenance personnel have to climb up at night to the place where the antenna is placed for the adjustment, and it will be very painstaking to adjust some certain antennas once they are installed, for instance, those at the top of a mountain, in a special building, etc. The level-3 intermodualtion indices of electronically adjustable antennas are generally better than those of mechanical antennas. And level-3 intermodualtion index are very much important for eliminating adjacent interference and stray interference, especially in areas of high traffic density with short distance between base stations and multiple carrier frequencies, where the index is required to be -150 dBc or so, to prevent great interference.CDMA is very sensitive to interference and noise. PN contamination and reduction of cell capacity will be caused if an MS receives at a certain point more than three sector signals with similar levels. So priority should be given to electronically adjustable antennas in selecting antennas for urban areas. But as electronically adjustable antennas are expensive and the quality is not stable at present, priority can be given to preset downtilt antennas. For downtilt angle calculation in details, please refer to the Guide to Antenna Downtilt Planning and Adjustment.2.5.2 Comparison of Function between Preset Downtilt and Null fill-in

Preset downtilt and null fill-in can both be used to solve the problem of Blind spot under tower caused by antenna null point. Yet, there is difference between the two. The use of preset downtilt may reduce the coverage of the major lobe, but it can increase the adjustable downtilt range in places with large downtilt angles. As a shaping technique, null fill-in can result in good antenna patterns. In this case, the upper minor lobe is suppressed, so antennas of this type will cause no adverse influence in other respects, though it is not able to increase the antenna Some antennas may possess both of these two characteristics, or one of the two, or none at all. So selection should be conducted according to the specific requirements of coverage in the planning stage.

Since the height of antennas in many occasions is not very great (over 50 meters), so the null depth effect of the antennas is not obvious, even if preset downtilt and null fill-in techniques are not used. Therefore, these two techniques are more used when wide coverage is required. And in this case, the increase of coverage is more important than the antenna adjustable downtilt range. Hence it is recommended that null fill-in antennas should be selected. But this is not applicable to urban areas where larger adjustable downtilt range is required and the null depth effect is not obvious. For urban areas, preset downtilt antennas are recommended for the sake of larger adjustable downtilt range.2.5.3 Downtilt Planning and Optimization

For omni-antennas, downtilt angles cannot be adjusted, but preset downtilt can be selected.In respect to directional antennas, the requirements for adjustable downtilt range are different in different occasions. In urban areas where control on coverage is more strict, larger adjustable downtilt range is required, which is generally X to 18, where X can either be 0, or a fixed preset electronic downtilt, an angle of 3 for instance. But the maximum downtilt angle of some mechanical downtilt antennas is 12 only, which is unfavorable for interference control, especially in case of tight multiplex. So reasonable downtilt range should be selected according to the actual situation of the planned area.But in places where interference is not important, a small adjustable downtilt range will be required. For instance, no consideration on downtilt is necessary at all in the case of wide coverage.

The maximum gain of the high gain shaping omni-antenna, which is certificated by Huawei, is 11dBi. The null fill-in level of antennas of this type is 25% (i.e., the depth of the first zero being -12dB), level-3 fixed electronic downtilt. It will be relatively ideal for antennas of this type to be used in mountainous and hilly areas, as it can effectively solve the problem of Blind spot under tower caused by too much height of antennas. Since a shaping antenna only fills the first zero under the antenna, so it will be able to do nothing if the antenna is hung too high. Therefore, it is recommended that R (the radial distance between the building that needs effective coverage and the antenna) and H (hanging height of the antenna) should satisfy the following relationship:

H14281296*262*116KATHREIN

806-960739 622681615X0-16degrees00/301296*262*116KATHREIN

806-960739 623681016.5X0-15degrees00>15301936*262*116KATHREIN

806-960739 634681016.5X0-15degrees60>14>301396*262*116KATHREIN

806-960739 624687.517.5XAfter cascade 0-16 degrees00/>302580*262*116KATHREIN

806-960739 636687.517.5XAfter cascade 0-16 degrees60>18>302580*262*116KATHREIN

Appendix 2: Main Antenna Types Optional for Rural Environment (800MHz)Working frequency band (MHz)Antenna type Horizontal beam width (degree)Verticalbeam width (degree)Gain (dBi)Polarization modeSupport adjust degree Electronic downtilt angle (degree)Null fill-in (degree)Upper lobe suppression (dB)Fron and back ratio (dB)Engineering specifications (MM) L*W*DDescriptionSupplier

806-960739 649901015X0/>14>251936/262/116KATHREIN

806-960739 650907.516.5X0/>15>252580/262/116KATHREIN

806-960739 662907.516.5X6/>16>252580/262/116KATHREIN

824-894738 192360711V0///3,237KATHREIN

806-960

Appendix 3: Main Antenna Types Optional for Highway Application Environment

Not available for the time being

Appendix 4: Main Antenna Types Optional for Mountainous Application Environment

Not available for the time being

Appendix 5: Main Antenna Types Optional for Offshore Application Environment

Not available for the time being

Appendix 6: Main Antenna Types Optional for Tunnel Application Environment

Not available for the time beingAppendix 7: Main Antenna Types Optional for Indoor Application Environment

Not available for the time being

Appendix 8: Website of Antenna Supplier Certificated by Huawei

The website of supplier of CDMA2000 base station antennas that have been certificated by the company up to now is given below:Http://www.kathrein.de

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2002-9-17 All Rights Reserved Page4 of 34