microwave basic theory

5/21/2018 Microwave Basic Theory

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HUAWEI TECHNOLOGIES Co., Ltd.

www.huawei.com

HUAWEI Confidential

Security Level:

Microwave Basic

Theory

Optical engineering Dep.


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HUAWEI TECHNOLOGIES CO., LTD. HUAWEI Confidential Page 2

CONTENTS

Introduction of microwave system

some basic concept

some basic knowledge


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DIFFERENT TRANSMISSION METHODS

MUX

Satellite

Fiber-optics cable

Radio link

Coaxial cable

MUX


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Frequency for microwave300MHZ300GHZWavelength 1mm~1m

SubbandUHF: 0.3-1.12G X8.2-12.4G

L: 1.12-1.7G KU12.4-18G

LS1.7-2.6 G K: 18-26G

S2.6-3.95 G Ka:26.5-40G

C3.95-5.85G U: 40-60G

XC5.85-8.2G

10Km 1Km 100m 10m 1m 10cm 1cm 1mm

f 30KHz 300KHz 3MHz 30MHz 300MHz 3GHz 30GHz 300GHz

LF MF HF VHF UHF SHF EHF

microwave


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85432 10 201 30 40 50

1.5 2.5Regional network

National network

Regional and local area network

2

8

34

Mbit/s

34140

155

Mbit/s

2834

140155

Mbit/s

3.3 11 GHz

GHz

RADIO-FREQUENCY USE

In this engineering 7G8G12G15G is the main frequency.


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FREQUENCY PLAN

Channel number

Frequency

F3

F1F2

Fo

1 2 n 1' n'

Lower half band Upper half band

Center frequency

2'

Channel number is also called waveguide number.


7/22HUAWEI TECHNOLOGIES CO., LTD. HUAWEI Confidential Page 7

For example

7Ghz(L)frequency band Frequency range:7125-7425MHz

Channel pairs:5 T/T spacing:28MHz( 1 to 2) T/R spacing:154MHz (1 to 1)

Channel# Center freq. Start freq. End freq. Channel# Center freq. Start freq. End freq.

1 7142.00 7128.00 7156.00 1' 7296.00 7282.00 7310.00

2 7170.00 7156.00 7184.00 2' 7324.00 7310.00 7338.00

3 7198.00 7184.00 7212.00 3' 7352.00 7338.00 7366.00

4 7226.00 7212.00 7240.00 4' 7380.00 7366.00 7394.00

5 7254.00 7240.00 7268.00 5' 7408.00 7394.00 7422.00



For example

7Ghz(U)frequency band Frequency range:7425-7725MHz

Channel pairs:5 T/T spacing:28MHz( 1 to 2) T/R spacing:154MHz (1 to 1)

Channel# Center freq. Start freq. End freq. Channel# Center freq. Start freq. End freq.

1 7442.00 7428.00 7456.00 1' 7596.00 7582.00 7610.00

2 7470.00 7456.00 7484.00 2' 7624.00 7610.00 7638.00

3 7498.00 7484.00 7512.00 3' 7652.00 7638.00 7666.00

4 7526.00 7512.00 7540.00 4' 7680.00 7666.00 7694.00

5 7554.00 7540.00 7568.00 5' 7708.00 7694.00 7722.00

Pay attention: There are ten frequency points in 7Ghz



Tx/Rx space and high/low site

Tx/Rx space

determined by the state

Different frequency has different Tx/Rx space

High/Low site

High site: Transmission frequency is higher than receival

frequency.

Low site: Transmission frequency is lower than receival

frequency.

Pay attention: High site and Low site are forbidden in one station!


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Changes of transmitting media,such as, atmosphere, link, time, altitude,climate etc.

Fading due to multipath arising from surface reflection

Attenuation due to atmospheric gases;

Attenuation due to rainsnow

Type of fading:

fast fading and slow fading;

fast fading: the channel impulse response changes rapidly within the symbol duration.

slow fading:the channel impulse response changes at a rate much lower than the

transmitted base band signal.

up fading and down fading;

up fading: direct wave arrives later than reflecting wave;down fading: direct wave arrives faster than reflecting wave

FADING


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FADINGMain cause: Rain snow for frequencies > 10 GHz

The frequency is higherthe Rain Fading is more!

Transmitter

FI

-80 < Pr < -20 dBm

Receiver Demodulator

Digital

Signal

IF

A B

CAG

A

Time

dBm

W0

Noise

WSignal

Noise

B

dBm

Time

IF Level 0 dBr 2dB

C

N


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How to confirm frequency?

In general

If the two sites distance is below 20Km, we can use 10GHz or

above to get connection. Such as 12GHz 15GHz

If the two sites distance is above 20Km, we can use 10GHz or

below to get connection. Such as 7GHz 8Ghz

The frequency is lower, the distance we can get is more!


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Basic concept

HOPA radio-link connection with a pair of communicating

terminals


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Basic concept

Gain of antenna:

])/(6.0lg[10 20 DG

D: diameter

: Wavelength

The diameter is more, Gain of antenna is more!

The diameter is more, the distance we can get is more!


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P = TX Power

PTX

Basic concept

Free Space Basic Transmission Loss

Power

Level

Distance

GTX GRX

PRX

G = Antenna Gain

A0

A0= Free Space Loss

M

Receiver Threshold

M = Fading Margin


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FSL = Free space loss (dB)

FSL = 92.4 20 lg D 20 lg F

FSL = Free Space Loss

D = Path Length in kilometres

F = Radio Frequency in Gigahertz

D

Km F

GHz


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PR : received voltage

PR = PT+ GT+ GR- FSL - A fTx- A fRx- ABR- A

PT = Transmitted Power (dBm)

PR= Received Power (dBm)

GT = Tx antenna gain (dB)

GR= Rx antenna gain (dB)FSL = Free space loss (dB)

A f,Tx= Loss in Tx feeder (dB)

A f,Rx= Loss in Rx feeder (dB)

ABR = Loss in RF branching system (dB)

A = Other attenuations


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Polarization

- The time varying direction and amplitude of the electric field vector of the

electromagnetic (radio) wave- Point- to- point microwave paths can be either vertically or horizontally

polarized

- Vertical to horizontal isolation is about 30 dB

Vertical polarization

E

Horizontal polarization

E

The polarization must be identical in one hop!


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Vertically Polarized

WaveguideHorizontally Polarized

Waveguide


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Vertical polarization


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Horizontal polarization


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Main-lobeSide-lobe

This concept is very important.

When we adjust the antenna, we will use this concept!

Main-lobe: maximal radiation intensity

Side-lobe: else lobe

Main-lobe

Side-

lobe

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