02.2-WCDMA RNP Antenna Selection_20051214

Antenna SelectionAntenna Selection

Review

Antenna is the interface between a radio transceiver and outside propagation environment. The same set of antenna can both transmit and receive radio waves. When transmitting radio waves, it converts the RF currents into electromagnetic (EM) waves; when receiving radio waves, it converts EM waves into RF currents.

Objectives

Learn the classification of antenna

Know some of characteristics of antenna

Study the principles for antenna selection

Understand the antenna usage at different scenarios

By this course, you will be able to:

Contents

Antenna Classification

Major Technical Performances of the Antenna

Principles for Antenna Type Selection

Antenna Selection for Different Scenarios

Summary

Based on the polarization mode: vertical polarization antennas (also called mono-polarization

antennas) Cross polarization antennas (also called dual polarization

antennas).


vertical polarization antenna dual polarization antenna


According to the outlines

whip antenna plate antenna cap antenna paraboloid antenna

Contents





Summary

Working Bands

in China and Europe UL: 1920 ~ 1980 MHz DL: 2110 ~ 2170 MHz

in North America UL: 1850 ~ 1910 MHz DL: 1930 ~ 1990 MHz

Antenna Gain

Gain is one of the most important indices of an antenna. It indicates the antenna’s capability of centralizing energy to a certain direction

dBi is defined as the energy centralizing capability of the actual directional antenna (including omni antenna) in relation to isotropic antennas, “i” means “isotropic”.

dBd is defined as the energy centralizing capability of the actual directional antenna (including omni antenna) in relation to dipole antennas, “d” means “dipole”.

Antenna Gain

As a passive device, antenna itself cannot increase the energy of transmitted signals. It only can centralize the energy to a certain direction by combining the antenna dipoles and changing their feeding mode

¸ Isotropic

DipoleActual antenna

The actual antenna gain is 11dBi

11dBi

8.85dBd 2.15dBi 2.15dBi ERP

EIRP

Antenna Pattern

The graph describes the distribution of EM field of the antenna transmission along the fixed distance on the angular coordinates is called pattern. A pattern presented by transmission field intensity is called field intensity pattern, a pattern presented by power density is called power density pattern, and a pattern presented by phase is called phase pattern.

Symmetric half-wave dipole Pattern

Top view side view

directional antenna pattern omni antenna pattern

Antenna Pattern

Antenna Pattern

Beam width (BW) (called semi-power angle) Front-to-back ratio Zero-point filling Upper side lobe suppression

Relationship between Wave Width and Gain

Antenna is an energy-centralizing device. The enhancement of transmission in one direction means the reduction of transmission in other directions. In general, we can enhance the transmission strength in a certain direction by reducing the horizontal lobe width so as to increase the antenna gain. Under a given antenna gain, the horizontal BW is in reverse proportion with the vertical BW:

10 lg 32400aG Ga : antenna gain, dBi;B: vertical BW, degree .Θ : horizontal BW, degree.

Polarization Mode

Polarization is the transmission performance describing the vector direction of EM field intensity. Unless specific state, the space direction of electric field vector is the polarization direction of EM wave. The vector direction refers to the direction of maximum transmission of antenna.

Single polarization antennas in WCDMA system adopt vertical polarization, while dual polarization antennas use polarization diversity to minimize the negative effect of multi-path fading in the mobile communication system so as to improve the quality of receiving signals. Dual polarization antennas in WCDMA system usually use

± 45° cross polarization mode.

Mechanical Down Tilt and Electric Down Tilt

Mechanical down tilt

electric down tilt

Voltage Standing Wave Ratio (VSWR)

When the input impedance is not consistent with the characteristic impedance, the reflected wave and the incident wave overlap on the feeder and form standing wave. The ratio between the maximum value and the minimal value of the adjacent voltage is VSWR. Big VSWR leads communications distance shortened, at same time reflection power returns to power amplifier (PA) of transmitter. PA might be damaged.

9.5 W

80 ohms

50 ohms

Forward: 10W

Reflection: 0.5W

Voltage Standing Wave Ratio (VSWR)

If and respectively stand for the input impedance and

nominal impedance of the antenna, the reflectance is

，， where . The matching feature of a

port can also be indicated by Reflection Loss. If

will be 13.98

A oZ

oA

oA

11

VSWR 50oZ

1:5.1VSWR

dBLR ..

Other Technical Performances

Port Isolation Power Capacity Input Interface of the Antenna Passive Inter-modulation (PIM) Antenna Size and Weight Wind Load Working Temperature and Humidity Lightning Protection Three-Proof Capability

Contents





Summary

Antenna Working Bands

Outdoor Antennas Both WCDMA and DCS systems simultaneously

1710 ~ 2170 MHz

Only for WCDMA system

1920 ~ 2170 MHz

Indoor Antennas for GSM/DCS/WLAN/WCDMA

800 ~ 2500 MHz

Principle for Antenna Beam Width Selection

Selection of beam width horizontal beam : depends on the type design of NodeB

vertical beam: depends on antenna gain

In urban areas 3-sector vertex-excited NodeBs, 65° horizontal beam width

6-sector vertex-excited NodeBs, 33° horizontal beam width

In suburbs

3-sector center-excited NodeBs, 90° horizontal beam width

Principle for Polarization Mode Selection

open mountainous areas and rural areas.

vertical single polarization antennas

urban area

dual polarization antennas

Principle for Downtilt Mode Selection

Comparison between Mechanical Downtilt and Electric DowntiltComparison between Mechanical Downtilt and Electric Downtilt


Comparison between Preset Electricity Downtilt and Zero-Point FillingComparison between Preset Electricity Downtilt and Zero-Point Filling

The use of preset electric downtilt can shorten the coverag

e range of the main lobe if the cell coverage is planed to

small.

Through zero-point filling, a kind of shaping technology, w

e can obtain a good pattern. In this case, the upper side lo

be can be suppressed, so this kind of antennas will influen

ce other aspects


Planning and Optimization of Downtilt AnglePlanning and Optimization of Downtilt Angle

For an omni antenna, we cannot adjust the mechanical do

wntilt angle, but we can select preset electricity downtilt an

gle antennas.

For a directional antenna, in different occasions, requirem

ents for the downtilt angle adjustment range are different.

Principle for Front-to-back Ratio Selection

In occasions where NodeB sites are densely distributed, if

the back lobe is too big, it will be likely to cause pilot polluti

on and the network quality will be influenced. In urban are

as, the antenna front-to-back ratio should be ≥ 25dB. In su

burbs or rural areas, the antenna front-to-back ratio can a

ppropriately lower.

The front-to-back ratio is in reverse proportion to the beam

width. The narrower the beam is, the higher the front-to-ba

ck ratio is.

Principle for Antenna Size Selection

Antenna size selection is mainly related to tAntenna size selection is mainly related to t

he installabilityhe installability

Firstly, the antenna size is related to the tec

hnical level of manufacturers

Secondly, the antenna size is related to the a

ntenna gain

Principle for Antenna Impedance Selection

The input impedance of a combiner is 50Ω. In order to reduce the standing wave ratio, the characteristic impedance of an antenna should match with the input impedance, namely, it should be 50Ω. In general, the characteristic impedance can meet this requirement, but attention should be paid to this index during selection or certification of new antennas.

Contents





Summary


In WCDMA system, antenna selection is of great importance. Antennas should be selected based on the practical situations such as the NodeB design, network coverage requirements and interference conditions.

Practical situations In urban coverage In sub-urban coverage In rural coverage In highway coverage In indoor coverage In offshore coverage In tunnel coverage

In Urban CoverageIn Urban Coverage

Huawei Recommendation

Frequency range: 1710 ~ 2170 MHz/±45°dual polarization / 65°horizontal BW/15 dBi gain/preset 6°electrical DT or 0 ~ 10°adjustable electrical DT and 0 ~ 15° adjustable mechanical DT/upper side lobe suppression and zero-point filling/25dB or higher front-to-back ratio.


In Suburban CoverageIn Suburban Coverage

Huawei Recommendation:

Select the specific antennas by referring to antenna selection for urban areas and that for rural areas depending

on the distance between two NodeBs.


In Rural CoverageIn Rural Coverage

Recommendation (for directional antennas): Working freq

uency 1710 ~ 2170 MHz / vertical polarization / 90° horizont

al beam width / 18 dBi antenna gain / without preset downtilt

/ zero-point filling

Recommendation (for omni antennas): Working frequency

1710 ~ 2170 MHz / vertical polarization / 11 dBi antenna gai

n / without preset downtilt / zero-point filling


In Highway CoverageIn Highway Coverage

Recommendation (for directional antennas): Working freq

uency 1710 ~ 2170 MHz / vertical polarization / 30° horizont

al beam width / 21 dBi antenna gain / without preset downtilt

/ zero-point filling

Recommendation (for 8-figure-shape antennas): Working

frequency 1710 ~ 2170 MHz / vertical polarization / dual 70°

horizontal beam width / 14 dBi antenna gain / without preset

downtilt / zero-point filling


For Highway CoverageFor Highway Coverage

Recommendation (for heart-shape antennas):

Frequency range: 1710 ~ 2170 MHz/VP/210°horizontal BW/

12 dBi gain/ without preset DT / zero-point filling

S0.5/0.5 NodeB configuration with high-gain directional ante

nnas 8-figure-shape antennas


In Indoor CoverageIn Indoor Coverage

Recommendation (for omni antennas):

Frequency range: 800 ~ 2500 MHz/vertical polarization

(VP)/360°horizontal BW, 90° vertical BW/2dBi gain.

Recommendation (for plate directional antennas): Frequency range: 800 ~ 2500 MHz/vP/90°horizontal BW,

60°vertical BW/7dBi gain.

Recommendation (for log-periodical antennas):

Frequency range: 800 ~ 2500 MHz/VP/55°horizontal BW,

50° vertical BW/11.5dBi gain.


In Offshore CoverageIn Offshore Coverage

Antenna Recommended:

frequency range: 1710 ~ 2170 MHz

vertical polarization

30° horizontal BW

gain 21 dBi

without preset DT

zero-point filling


In Tunnel CoverageIn Tunnel Coverage

Antenna Recommended

Frequency range: 800 ~ 2200 MHz

vertical polarization

55°horizontal BW

log-periodical type with gain 11.5 dBi (consider sharing with GSM/DCS systems).

Leaky cable


Contents





Summary

Summary

This course helps you: To make sure antenna classification To familiarize with performances of antenna To understand the principles of antenna selection To select antenna focusing on specific working

environments

02.2-WCDMA RNP Antenna Selection_20051214

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