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Microwave Basic Theory
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5/21/2018 Microwave Basic Theory
1/22
HUAWEI TECHNOLOGIES Co., Ltd.
www.huawei.com
HUAWEI Confidential
Security Level:
Microwave Basic
Theory
Optical engineering Dep.
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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.
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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
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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
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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