Digital Microwave
Communication Principles
www.huawei.com
Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Foreword

This course is developed to meet the requirement of Huawei Optical
Network RTN microwave products.

This course informs engineers of the basics on digital microwave
communications, which will pave the way for learning the RTN series
microwave products later.
Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Page 2
Learning Guide

Microwave communication is developed on the basis of the
electromagnetic field theory.
Therefore, before learning this course, you are supposed to have
mastered the following knowledge:

Network communications technology basics

Electromagnetic field basic theory
Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Page 3
Objectives

After this course, you will be able to explain:

Concept and characteristics of digital microwave communications

Functions and principles of each component of digital microwave
equipment

Common networking modes and application scenarios of digital
microwave equipment

Propagation principles of digital microwave communication and
various types of fading

Anti-fading technologies

Procedure and key points in designing microwave transmission link
Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Page 4
Contents
1. Digital Microwave Communication Overview
2. Digital Microwave Communication Equipment
3. Digital Microwave Networking and Application
4. Microwave Propagation and Anti-fading Technologies
5. Designing Microwave Transmission Links
Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Page 5
Transmission Methods
in Current Communications Networks
Coaxial cable communication
Optical fiber communication
Microwave
communication
Microwave TE
Microwave TE
MUX/DEMUX
MUX/DEMUX
Satellite communication
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Page 6
Microwave Communication
vs. Optical Fiber Communication
Microwave Communication
Powerful space cross ability, little land
occupied, not limited by land privatization
Small investment, short construction
period, easy maintenance
Optical Fiber Communication
Optical fiber burying and land
occupation required
Large investment ,long construction period
Strong protection ability against natural
disaster and easy to be recover
Outdoor optical fiber maintenance required
and hard to recover from natural disaster
Limited frequency resources (frequency
license required)
Not limited by frequency, license not
required
Transmission quality greatly affected by
climate and landform
Stable and reliable transmission quality
and not affected by external factors
Limited transmission capacity
Large transmission capacity
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Page 7
Definition of Microwave

Microwave

Microwave is a kind of electromagnetic wave. In a broad sense, the
microwave frequency range is from 300 MHz to 300 GHz. But In
microwave communication, the frequency range is generally from 3
GHz to 30 GHz.

According to the characteristics of microwave propagation, microwave
can be considered as plane wave.

The plane wave has no electric field and magnetic field longitudinal
components along the propagation direction. The electric field and
magnetic field components are vertical to the propagation direction.
Therefore, it is called transverse electromagnetic wave and TEM wave
for short.
Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Page 8
Development of Microwave Communication
155M
Transmission
capacity
bit/s/ch)
SDH digital microwave
communication
system
34/140M
PDH digital microwave
communication
system
2/4/6/8M
480 voice
channels
Small and medium
capacity digital microwave
communication system
Analog microwave
communication
system
Late 1990s to now
1980s
1970s
1950s
Note:
Small capacity: < 10M
Medium capacity: 10M to 100M
Large capacity: > 100M
Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Page 9
Concept of Digital
Microwave Communication

Digital microwave communication is a way of transmitting digital information in
atmosphere through microwave or radio frequency (RF).

Microwave communication refers to the communication that use microwave as carrier .

Digital microwave communication refers to the microwave communication that adopts the
digital modulation.

The baseband signal is modulated to intermediate frequency (IF) first . Then the
intermediate frequency is converted into the microwave frequency.

The baseband signal can also be modulated directly to microwave frequency, but only
phase shift keying (PSK) modulation method is applicable.

The electromagnetic field theory is the basis on which the microwave communication
theory is developed.
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Page 10
Microwave Frequency Band
Selection and RF Channel Configuration (1)
Generally-used frequency bands in digital microwave transmission:


7G/8G/11G/13G/15G/18G/23G/26G/32G/38G (defined by ITU-R Recommendations)
1.5 GHz
2.5 GHz
Regional network
3.3 GHz
Long haul
trunk network
11 GHz
Regional network, local network,
and boundary network
2/8/34
Mbit/s
34/140/155 Mbit/s
2/8/34/140/155 Mbit/s
GHz
1
2
3
4
5
8
10
Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
20
30
Page 11
40 50
Microwave Frequency Band
Selection and RF Channel Configuration (2)

In each frequency band, subband frequency ranges, transmitting/receiving spacing
(T/R spacing), and channel spacing are defined.
Frequency range
Low frequency band
f0 (center frequency)
High frequency band
T/R spacing
T/R spacing
Protection
spacing
Channel
spacing
f1
Adjacent channel
T/R spacing
f2
fn
Channel
spacing
f1’
Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
f2’
fn’
Page 12
Microwave Frequency Band
Selection and RF Channel Configuration (3)
Frequency range (7425M–7725M)
f0 (7575M)
T/R spacing: 154M
28M
f1=7442
7G Frequency
f2=7470
F0 (MHz)
Range
f1’=7596
f5
T/R Spacing
f2’
f5’
Channel Spacing Primary and Non-
(MHz)
(MHz)
primary Stations
Fn=f0-161+28n,
7425–7725
7575
154
28
Fn’=f0- 7+28n,
(n: 1–5)
7575
161
7
7275
196
28
7597
196
28
7250–7550
7400
161
3.5
…
…
…
…
7110–7750
Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
…
Page 13
Digital Microwave
Communication Modulation (1)

Digital baseband signal is the unmodulated digital signal. The baseband signal
cannot be directly transmitted over microwave radio channels and must be converted
into carrier signal for microwave transmission.
Channel bandwidth
Baseband signal rate
Digital baseband signal
Modulation
IF signal
Service signal
transmitted
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Page 14
Digital Microwave
Communication Modulation (2)
The following formula indicates a digital baseband signal being converted into a digital
frequency band signal.

A*COS(Wc*t+φ)
Amplitude




Frequency
Phase
PSK and QAM are
most frequently
used in digital
microwave.
ASK: Amplitude Shift Keying. Use the digital baseband signal to change the carrier
amplitude (A). Wc and φ remain unchanged.
FSK: Frequency Shift Keying. Use the digital baseband signal to change the carrier
frequency (Wc). A and φ remain unchanged.
PSK: Phase Shift Keying. Use the digital baseband signal to change the carrier phase
(φ). Wc and A remain unchanged.
QAM: Quadrature Amplitude Modulation. ). Use the digital baseband signal to change
the carrier phase (φ) and amplitude (A). Wc remains unchanged.
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Page 15
Microwave Frame Structure (1)

RFCOH
171.072 Mbit/s
15.552 Mbit/s
RFCOH
STM-1 155.52 Mbit/s
SOH
Payload
MLCM
DMY
XPIC
ATPC
WS
RSC
INI
ID
FA
11.84 Mbit/s 64 kbit/s 16 kbit/s 64 kbit/s 2.24 Mbit/s 864 kbit/s 144 kbit/s 32 kbit/s 288 kbit/s
RFCOH: Radio Frame Complementary Overhead
RSC: Radio Service Channel
MLCM: Multi-Level Coding Modulation
INI: N:1 switching command
DMY: Dummy
ID: Identifier
XPIC: Cross-polarization Interference Cancellation
FA: Frame Alignment
ATPC: Automatic Transmit Power Control
WS: Wayside Service
Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Page 16
Microwave Frame Structure (2)

RFCOH is multiplexed into the STM-1 data and a block multiframe is formed. Each
multiframe has six rows and each row has 3564 bits. One multiframe is composed of
two basic frames. Each basic frame has 1776 bits. The remaining 12 bits are used
for frame alignment.
Multiframe 3564 bits
6 bits
FS
Basic frame 1
FS
Basic frame 2
6 bits
1776 bits（148 words）
6 bits
1776 bits (148 words)
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
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b
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C2
I
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a
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b
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C2
I
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C1
I
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C1
I
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C1
I
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C1
I
I
C1
I
I
C1
I
I
C1
I
I
C1
12 bits (the 1st word)
12 bits (the 148th word)
I: STM-1 information bit
C1/C2: Two-level correction coding monitoring bits
FS: Frame synchronization
a/b: Other complementary overheads
Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Page 17
Questions

What is microwave?

What is digital microwave communication?

What are the frequently used digital microwave frequency bands?

What concepts are involved in microwave frequency setting?

What are the frequently used modulation schemes? Which are the most
frequently used modulation schemes?
Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Page 18
Contents
1. Digital Microwave Communication Overview
2. Digital Microwave Communication Equipment
3. Digital Microwave Networking and Application
4. Microwave Propagation and Anti-fading Technologies
5. Designing Microwave Transmission Links
Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Page 19
Microwave Equipment Category
Digital microwave
System
Analog microwave
MUX/DEMUX
Mode
PDH
SDH
Capacity
Small and medium
capacity (2–16E1, 34M)
Large capacity
(STM-0, STM-1, 2xSTM-1)
(Discontinued)
Trunk radio
Structure
Split-mount radio
All outdoor radio
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Page 20
Trunk Microwave Equipment
•
•
High cost, large
transmission capacity,
more stable
performance, applicable
to long haul and trunk
transmission
MSTU: Main Signal
Transmission Unit
(transceiver, modem, SDH
electrical interface, hitless
switching)
P
M1
SCSU: Supervision,
Control and Switching
Unit
M2
…
RF, IF, signal
processing, and
MUX/DEMUX units are
all indoor. Only the
antenna system is
outdoor.
BRU: Branch RF Unit
BBIU: Baseband
Interface Unit (option)
(STM-1 optical interface,
C4 PDH interface)
SDH microwave equipment
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Page 21
All Outdoor Microwave Equipment
• All the units are
outdoor.
RF processing unit
IF cable
• Installation is easy.
IF and baseband
processing unit
• The equipment
room can be saved.
Service and power cable
All outdoor microwave equipment
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Page 22
Split-Mount Microwave Equipment (1)

The RF unit is an outdoor unit (ODU).
The IF, signal processing, and
Antenna
MUX/DEMUX units are integrated in
the indoor unit (IDU). The ODU and
IF cable
IDU are connected through an IF cable.

The ODU can either be directly
mounted onto the antenna or
ODU
(Outdoor Unit)
connected to the antenna through a
short soft waveguide.

IDU
(Indoor Unit)
Although the capacity is smaller than
the trunk, due to the easy installation
and maintenance, fast network
construction, it’s the most widely used
microwave equipment.
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Split-mount microwave
equipment
Page 23
Split-Mount Microwave Equipment (2)

Unit Functions

Antenna: Focuses the RF signals transmitted by ODUs and increases the signal
gain.

ODU: RF processing, conversion of IF/RF signals.

IF cable: Transmitting of IF signal, management signal and power supply of ODU.

IDU: Performs access, dispatch, multiplex/demultiplex, and
modulation/demodulation for services.
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Page 24
Split-Mount Microwave Equipment
– Installation
Direct Mount
Separate Mount
antenna
(direct mount)
antenna
(separate mount)
ODU
Soft waveguide
IF cable
IF cable
ODU
中频口
IDU
IF port
IDU
IF port
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Page 25
Microwave Antenna (1)
Parabolic antenna

Antennas are used to send and receive microwave signals.
Parabolic antennas is common type of microwave antennas.
Microwave antenna diameters includes: 0.3m, 0.6m, 1.2m, 1.8m,2.0m, 2.4m, 3.0m, 3.2metc.
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Page 26
Microwave Antenna (2)

Different frequency channels in same frequency band can share one antenna.
T
x
R
x
T
x
R
Channe
l
1
Channe
l
1
1
1
n
n
n
n
x
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Page 27
Antenna Adjustment (1)
Side lobe
Side view
Half-power angle
Main lobe
Tail lobe
Side lobe
Top view
Half-power angle
Main lobe
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Tail lobe
Page 28
Antenna Adjustment (2)
During antenna adjustment, change the direction
vertically or horizontally. Meanwhile, use a multimeter to
test the RSSI at the receiving end. Usually, the voltage
wave will be displayed as shown in the lower right corner.
The peak point of the voltage wave indicates the main lobe
position in the vertical or horizontal direction. Large-scope
adjustment is unnecessary. Perform fine adjustment on the
antenna to the peak voltage point.

When antennas are poorly aligned, a small voltage may
be detected in one direction. In this case, perform coarse
adjustment on the antennas at both ends, so that the
antennas are roughly aligned.

The antennas at both ends that are well aligned face a
little bit upward. Though 1–2 dB is lost, reflection
interference will be avoided.

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AGC
Voltage
detection point
VAGC
Angle
Side lobe position
Main lobe position
Page 29
Antenna Adjustment (3)

During antenna adjustment, the two
wrong adjustment cases are show here.
One antenna is aligned to another
antenna through the side lobe. As a
result, the RSSI cannot meet the
requirements.
Wrong
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Wrong
Page 30
Correct
Split-Mount Microwave Equipment
– Antenna (1)

Antenna gain

Definition: Ratio of the input power of an isotropic antenna Pio to the input power of a
parabolic antenna Pi when the electric field at a point is the same for the isotropic antenna
and the parabolic antenna.
P
D 
Calculating formula of antenna gain: G  io  
 
Pi   
2


Half-power angle

Usually, the given antenna specifications contain the gain in the largest radiation (main lobe)
direction, denoted by dBi. The half-power point, or the –3 dB point is the point which is
deviated from the central line of the main lobe and where the power is decreased by half. The
angle between the two half-power points is called the half-power angle.

Calculating formula of half-power angle:
 0.5  (650 ~ 700 )

D
Half-power angle
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Page 31
Split-Mount Microwave Equipment
– Antenna (2)

Cross polarization discrimination
Suppression ratio of the antenna receiving heteropolarizing waves, usually, larger than 30 dB.


XdB＝10lgPo/Px

Po: Receiving power of normal polarized wave

Px: Receiving power of abnormal polarized wave
Antenna protection ratio

Attenuation degree of the receiving capability in a direction of an antenna compared with
that in the main lobe direction. An antenna protection ratio of 180° is called front-to-back
ratio.
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Page 32
Split-Mount Microwave Equipment
– ODU (1)
ODU system Uplink
architecture
IF/RF conversion
IF
amplificat
ion
Frequency
mixing
Sideband
filtering
Local
oscillation
(Tx)
ATPC
Local
oscillation
(Rx)
Supervi
sion and
control
signal
IF
amplification
Filtering
Frequency
mixing
RF
attenuation
Power
amplification
Power
detection
RF loop
Low-noise
amplification
Bandpass
filtering
Downlink RF/IF conversion
Alarm and control
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Page 33
Split-Mount Microwave Equipment
– ODU (2)

Specifications of Transmitter

Working frequency band
Generally, trunk radios use 6, 7, and 8 GHz frequency bands. 11, 13 GHz and
higher frequency bands are used in the access layer (e.g. BTS access).

Output power
The power at the output port of a transmitter. Generally, the output power is 15 to
30 dBm.
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Page 34
Split-Mount Microwave Equipment
– ODU (3)

Local frequency stability
If the working frequency of the transmitter is unstable, the demodulated effectived
signal ratio will be decreased and the bit error ratio will be increased. The value
range of the local frequency stability is 3 to 10 ppm.

Transmit Frequency Spectrum Frame
The frequency spectrum of the transmitted signal must meet specified
requirements, to avoid occupying too much bandwidth and thus causing too much
interference to adjacent channels. The limitations to frequency spectrum is
called transmit frequency spectrum frame.
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Page 35
Split-Mount Microwave Equipment
– ODU (4)

Specifications of Receiver

Working frequency band
Receivers work together with transmitters. The receiving frequency on the local
station is the transmitting frequency of the same channel on the opposite station.

Local frequency stability
The same as that of transmitters: 3 to 10 ppm

Noise figure
The noise figure of digital microwave receivers is 2.5 dB to 5 dB.
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Page 36
Split-Mount Microwave Equipment
– ODU (5)

Passband
To effectively suppress interference and achieve the best transmission quality, the
passband and amplitude frequency characteristics should be properly chosen. The
receiver passband characteristics depend on the IF filter.

Selectivity
Ability of receivers of suppressing the various interferences outside the passband,
especially the interference from adjacent channels, image interference and the
interference between transmitted and received signals.

Automatic gain control (AGC) range
Automatic control of receiver gain. With this function, input RF signals change within a
certain range and the IF signal level remains unchanges.
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Page 37
Split-Mount Microwave Equipment
– ODU (6)
Frequency range (7425M–7725M)
T/R spacing: 154M
Subband A
7442
Subband B
f0(7575M)
Subband C
Subband A
Subband B Subband C
ODUs are of rich
types and small
volume. Usually,
ODUs are
produced by small
manufacturers and
integrated by big
manufacturers.
7498
Non-primary station
Primary station
ODU specifications are related to radio
frequencies. As one ODU cannot cover an entire
frequency band, usually, a frequency band will be
divided into several subbands and each subband
corresponds to one ODU.
 Different T/R spacing corresponds to different
ODUs.
 Primary and non-primary stations have different
ODUs.

Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Types of ODUs = Number
of frequency bands x
Number of T/R spacing x
Number of subbands x 2
(ODUs of some
manufacturers are also
classified by capacity.
Page 38
Split-Mount Microwave Equipment
– IDU
Service
channel
IF unit
Tributary
unit
Microwave
frame
demultiplexing
Modulat
ion
Demod
ulation
Tx IF
Rx IF
Line unit
O&M
interface
Power
interface
Service
channel
Supervision and control
DC/DC conversion
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Page 39
Cable interface
Crossconne
ction
Microwave
frame
multiplexing
From/to ODU
Questions

What types are microwave equipment classified into?

What units do the split-mount microwave equipment have? And
what are their functions??

How to adjust antennas?

What are the key specifications of antennas?

What are the key specifications of ODU transmitters and receivers?

Can you describe the entire signal flow of microwave transmission?
Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Page 40
Summary

Classification of digital microwave equipment

Components of split-mount microwave equipment and their
functions

Antenna installation and key specifications of antennas

Functional modules and key performance indexes of ODU

Functional modules of IDU

Signal flow of microwave transmission
Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Page 41
Contents
1. Digital Microwave Communication Overview
2. Digital Microwave Communication Equipment
3. Digital Microwave Networking and Application
4. Microwave Propagation and Anti-fading Technologies
5. Designing Microwave Transmission Links
Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Page 42
Common Networking Modes of
Digital Microwave
Ring network
Chain network
Add/Drop
network
Hub network
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Page 43
Types of Digital Microwave Stations
• Digital microwave stations are classified into Pivotal stations, add/drop relay stations,
relay stations and terminal stations.
Add/Drop
relay station
Relay
station
Terminal
station
Terminal
station
Pivotal
station
Terminal
station
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Page 44
Types of Relay Stations
Passive
• Back-to-back antenna
• Plane reflector
Active
• Regenerative repeater
• IF repeater
• RF repeater
Relay station
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Page 45
Active Relay Station

Radio Frequency relay station
An active, bi-directional radio repeater system without frequency shift. The
RF relay station directly amplifies the signal over radio frequency.


Regenerator relay station

A high-frequency repeater of high performance. The regenerator relay station
is used to extend the transmission distance of microwave communication
systems, or to deflect the transmission direction of the signal to avoid
obstructions and ensure the signal quality is not degraded. After complete
regeneration and amplification, the received signal is forwarded.
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Page 46
Passive Relay Station

Parabolic reflector passive relay station

The parabolic reflector passive relay station is composed of two
parabolic antennas connected by a soft waveguide back to back.

The two-parabolic passive relay station often uses large-diameter
antennas. Meters are necessary to adjust antennas, which is time
consuming.

The near end is less than 5 km away.
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Page 47
Plane Reflector Passive Relay Station
Plane reflector passive relay station: A metal board which has smooth surface,
proper effective area, proper angle and distance with the two communication
points. It is also a passive relay microwave station.


Full-distance free space loss:
d1(km)

Ls  1421
.  20 log d1d2  20 log a
d 2(km)
a  A cos 2
“a” is the effective area (m2) of the flat reflector.
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Page 48
Passive Relay Station (Photos)
Passive relay station
(plane reflector)
Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Passive relay station
(parabolic reflectors)
Page 49
Application of Digital Microwave
BTS backhaul
transmission
Complementary
networks to optical
networks (access the
services from the last
1 km)
Special transmission
conditions (rivers, lakes,
islands, etc.)
Microwave
application
Emergency
communications
(conventions, activities,
danger elimination,
disaster relief, etc.)
Redundancy backup
of important links
VIP customer
access
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Page 50
Questions

What are the networking modes frequently used for digital microwave?

What are the types of digital microwave stations?

What are the types of relay stations?

What is the major application of digital microwave?
Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Page 51
Contents
1. Digital Microwave Communication Overview
2. Digital Microwave Communication Equipment
3. Digital Microwave Networking and Application
4. Microwave Propagation and Anti-fading Technologies
5. Designing Microwave Transmission Links
Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Page 52
Contents
4. Microwave Propagation and Anti-fading Technologies

4.1 Factors Affecting Electric Wave Propagation

4.2 Various Fading in Microwave Propagation

4.3 Anti-fading Technologies for Digital Microwave
Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Page 53
Key Parameters in
Microwave Propagation (1)

Fresnel Zone and Fresnel Zone Radius

Fresnel zone: The sum of the distance from P to T and the distance from P to R
complies with the formula, TP+PR-TR= n/2 (n=1,2,3, …). The elliptical region
encircled by the trail of P is called the Fresnel zone.
T
O
R
F1
P
d1

d2
Fresnel zone radius: The vertical distance from P to the TR line in the Fresnel
zone. The first Fresnel zone radius is represented by F1 (n=1).
Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Page 54
Key Parameters in
Microwave Propagation (2)


Formula of the first Fresnel zone radius:
F1  17.32
d1 (km)  d 2 (km)
f (GHz )  d (km)
The first Fresnel zone is the region where the microwave transmission energy is
the most concentrated. The obstruction in the Fresnel zone should be as little as
possible. With the increase of the Fresnel zone serial numbers, the field strength of the
receiving point reduces as per arithmetic series.
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Page 55
Key Parameters in
Microwave Propagation (3)

A
Clearance
F
M
h3
h1
hc
B
hp
h5
hs
h4
h6
d1

h2
d2
d
Along the microwave propagation trail, the obstruction from buildings, trees, and
mountain peaks is sometimes inevitable. If the height of the obstacle enters the first Fresnel
zone, additional loss might be caused. As a result, the received level is decreased and the
transmission quality is affected. Clearance is used to avoid the case described previously.

The vertical distance from the obstacle to AB line segment is called the clearance of the
obstacle on the trail. For convenience, the vertical distance hc from the obstacle to the
ground surface is used to represent the clearance. In practice, the error is not big because
the line segment AB is approximately parallel to the ground surface. If the first Fresnel zone
radius of the obstacle is F1, then hc/ F1 is the relative clearance.
Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Page 56
Factors Affecting Electric Wave Propagation
– Terrain

The reflected wave from the ground surface is the major factor that affects the received level.
Straight line
Reflection

Straight line
Reflection
Smooth ground or water surface can reflect the part of the signal energy transmitted by the
antenna to the receiving antenna and cause interference to the main wave (direct wave). The vector
sum of the reflected wave and main wave increases or decreases the composite wave. As a result,
the transmission becomes unstable. Therefore, when doing microwave link design, avoid reflected
waves as much as possible. If reflection is inevitable, make use of the terrain ups and downs to block
the reflected waves.
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Page 57
Factors Affecting Electric Wave Propagation
– Terrain

Different reflection conditions of different terrains have different effects on electric
wave propagation. Terrains are classified into the following four types:


Type A: mountains (or cities with dense buildings)

Type B: hills (gently wavy ground surface)

Type C: plain

Type D: large-area water surface
The reflection coefficient of mountains is the smallest, and thus the mountain terrain
is most suitable for microwave transmission. The hill terrain is less suitable. When
designing circuits, try to avoid smooth plane such as water surface.
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Page 58
Factors Affecting Electric Wave
Propagation – Atmosphere

Troposphere indicates the low altitude atmosphere within 10 km from the ground.
Microwave antennas will not be higher than troposphere, so the electric wave
propagation in aerosphere can be narrowed down to that in troposphere. Main effects
of troposphere on electric wave propagation are listed below:

Absorption caused by gas resonance. This type of absorption can affect the
microwave at 12 GHz or higher.

Absorption and scattering caused by rain, fog, and snow. This type of
absorption can affect the microwave at 10 GHz or higher.

Refraction, absorption, reflection and scattering caused by inhomogeneity of
atmosphere. Refraction is the most significant impact to the microwave
propagation.
Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Page 59
Contents
4. Microwave Propagation and Anti-fading Technologies

4.1 Factors Affecting Electric Wave Propagation

4.2 Various Fading in Microwave Propagation

4.3 Anti-fading Technologies for Digital Microwave
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Page 60
Fading in Microwave Propagation

Fading: Random variation of the received level. The variation is irregular and the
reasons for this are various.
Fading
mechanism
Fading time
Frequency selective fading
Page 61
Influence of
fading on signal
Flat fading
Down fading
Up fading
Slow fading
Fast fading
Duct type fading
K-type fading
Scintillation
fading
Rain fading
Absorption fading
Free space propagation
fading
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Received
level
Free Space Transmission Loss

Free space loss: A = 92.4 + 20 log d + 20 log f
(d: km, f: GHz). If d or f is doubled, the loss will increase by 6 dB.
d
GTX
PTX = Transmit power
GRX
PRX = Receive power
G = Antenna gain
f
Power level
A0 = Free space loss
M = Fading margin
G
A0
PTX
PRX
G
M
Receiving threshold
Distance
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Page 62
Absorption Fading

Molecules of all substances are composed of charged particles. These particles
have their own electromagnetic resonant frequencies. When the microwave frequencies
of these substances are close to their resonance frequencies, resonance absorption
occurs to the microwave.

Statistic shows that absorption to the microwave frequency lower than 12 GHz is
smaller than 0.1 dB/km. Compared with free space loss, the absorption loss can be
ignored.
10dB
1dB
0.1dB
0.01dB
60GHz
23GHz
12GHz
7.5GHz
1GHz
Atmosphere absorption curve (dB/km)
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Page 63
Rain Fading

For frequencies lower than 10 GHz, rain loss can be ignored. Only a few db may
be added to a relay section.

For frequencies higher than 10 GHz, repeater spacing is mainly affected by rain
loss. For example, for the 13 GHz frequency or higher, 100 mm/h rainfall causes a
loss of 5 dB/km. Hence, for the 13 GHz and 15 GHz frequencies, the maximum relay
distance is about 10 km. For the 20 GHz frequency and higher, the relay distance is
limited in few kilometres due to rain loss.

High frequency bands can be used for user-level transmission. The higher the
frequency band is, the more severe the rain fading.
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Page 64
K-Type Fading (1)

Atmosphere refraction

As a result of atmosphere refraction, the microwave propagation trail is bent. It is
considered that the electromagnetic wave is propagated along a straight line above
the earth with an equivalent earth radius of

Re , Re
= KR (R: actual earth radius.)
The average measured K value is about 4/3. However, the K value of a specific
section is related to the meteorological phenomena of the section. The K value may
change within a comparatively large range. This can affect line-of-sight propagation.
Re
Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
R
Page 65
K-Type Fading (2)

Microwave propagation
k > 1: Positive refraction
k = 1: No refraction
k < 1: Negative refraction
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Page 66
K-Type Fading (3)

Equivalent earth radius
In temperate zones, the refraction when the K value is 4/3 is regarded
as the standard refraction, where the atmosphere is the standard
atmosphere and Re which is 4R/3 is the standard equivalent earth radius.

k=∞
4/3
1
2/3
Ground surface
Actual earth radius (r)
2/3
1
4/3
k=∞
Ground surface
Equivalent earth radius (r·k)
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Page 67
Multipath Fading (1)
Multipath fading: Due to multipath propagation of refracted waves, reflected
waves, and scattered waves, multiple electric waves are received at the
receiving end. The composition of these electric waves will result in severe
interference fading.

Reasons for multipath fading: reflections due to non-uniform atmosphere,
water surface and smooth ground surface.

Down fading: fading where the composite wave level is lower than the free
space received level. Up fading: fading where the composite wave level is
higher than the free space received level.


Non-uniform atmosphere

Water surface

Smooth ground surface.
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Ground surface
Page 68
Multipath Fading (2)

Multipath fading is a type of interference fading caused by multipath transmission.
Multipath fading is caused by mutual interference between the direct wave and
reflected wave (or diffracted wave on some conditions) with different phases.

Multipath fading grows more severe when the wave passes water surface or
smooth ground surface. Therefore, when designing the route, try to avoid smooth
water and ground surface. When these terrains are inevitable, use the high and low
antenna technologies to bring the reflection point closer to one end so as to reduce
the impact of the reflected wave, or use the high and low antennas and space
diversity technologies or the antennas that are against reflected waves to overcome
multipath fading.
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Page 69
Multipath Fading
– Frequency Selective Fading
Received power (dBm)
Flat
Selective fading
Normal
Frequency (MHz)
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Page 70
Multipath Fading – Flat Fading
Up fading
Received level
in free space
Threshold level
(-30 dB)
1h
Signal
interruption
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Page 71
Duct Type Fading
Due to the effects of the meteorological conditions such as ground cooling in the
night, burnt warm by the sun in the morning, smooth sea surface, and anticyclone, a
non-uniform structure is formed in atmosphere. This phenomenon is called
atmospheric duct.
If microwave beams pass through the atmospheric duct while the receiving point is
outside the duct layer, the field strength at the receiving point is from not only the
direct wave and ground reflected wave, but also the reflected wave from the edge of
the duct layer. As a result, severe interference fading occurs and causes interruption
to the communications.
Duct type fading
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Page 72
Scintillation Fading
When the dielectric constant of local atmosphere is different from the ambient due to the
particle clusters formed under different pressure, temperature, and humidity conditions,
scattering occurs to the electric wave. This is called scintillation fading. The amplitude
and phase of different scattered waves vary with the atmosphere. As a result, the
composite field strength at the receiving point changes randomly.
Scintillation fading is a type of fast fading which lasts a short time. The level changes
little and the main wave is barely affected. Scintillation fading will not cause
communications interruption.
Scintillation fading
闪烁衰落示意图
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Page 73
Summary

The higher the frequency is and the longer the hop distance is, the more severe the
fading is.

Fading is more severe at night than in the daylight, in summer than in winter. In the
daylight, sunshine is good for air convection. In summer, weather changes frequently.

In sunny days without wind, atmosphere is non-uniform and atmosphere subdivision
easily forms and hardly clears. Multipath transmission often occurs in such conditions.

Fading is more severe along water route than land route, because both the reflection
coefficient of water surface and the atmosphere refraction coefficient above water
surface are bigger.

Fading is more severe along plain route than mountain route, because atmosphere
subdivision often occurs over plain and the ground reflection factor of the plain is
bigger.

Rain and fog weather causes much influence on high-frequency microwave.
Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Page 74
Contents
4. Microwave Propagation and Anti-fading Technologies

4.1 Factors Affecting Electric Wave Propagation

4.2 Various Fading in Microwave Propagation

4.3 Anti-fading Technologies for Digital Microwave
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Page 75
Anti-fading Technologies
for Digital Microwave System (1)
Category
Equipment level
countermeasure
Effect
Adaptive equalization
Waveform distortion
Automatic transmit power
control (ATPC)
Power reduction
Forward error correction
(FEC)
Power reduction
System level
Diversity receiving technology
countermeasure
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Power reduction and
waveform distortion
Page 76
Anti-fading Technologies
for Digital Microwave System (2)

Frequency domain equalization
Multipath fading
Signal frequency
spectrum

Slope equalization
Frequency spectrum
after equalization
The frequency domain equalization only equalizes the amplitude frequency
response characteristics of the signal instead of the phase frequency spectrum
characteristics.

The circuit is simple.
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Page 77
Anti-fading Technologies
for Digital Microwave System (3)

Time domain equalization
Time domain equalization directly counteracts the intersymbol
interference.

T
C-n
…
T
…
C0
T
Cn
After
Before
-2Ts
-Ts
Ts
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-2Ts
-Ts
Page 78
Ts
Anti-fading Technologies
for Digital Microwave System (4)

Automatic transmit power control (ATPC)
Under normal propagation conditions, the output power of the transmitter is always
at a lower level, for example, 10 to 15 dB lower than the normal level. When
propagation fading occurs and the receiver detects that the propagation fading is
lower than the minimum received level specified by ATPC, the RFCOH is used to let
the transmitter to raise the transmit power.

Working principle of ATPC
Modulator
Transmitter
ATPC
Demodulator
Receiver
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Receiver
Demodulator
ATPC
Transmitter
Page 79
Modulator
Anti-fading Technologies
for Digital Microwave System (5)

ATPC: The output power of the transmitter automatically traces and changes with the
received level of the receiver within the control range of ATPC.

The time rate of severe propagation fading is usually small (<1%). After ATPC is
configured, the transmitter works at a power 10 to 15 dB lower than the nominal
power for over 99% of the time. In this way, adjacent channel interference and
power consumption can be reduced.

Effects of ATPC:
 Reduces the interference to adjacent
systems and over-reach interference
 Reduces up fading
 Improves residual BER
 Reduces DC power consumption
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Page 80
Anti-fading Technologies
for Digital Microwave System (6)

ATPC adjustment process (gradual change)
High level
-35
31
-45
Low level
21
-55
ATPC dynamic range
-72
45
75
85
102
Link loss (dB)
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Page 81
Transmitter output level (dBm)
Received level (dBm)
-25
Anti-fading Technologies
for Digital Microwave System (7)
Cross-polarization interference
cancellation (XPIC)

680MHz
30MHz
340 MHz
80MHz
60MHz
In microwave transmission, XPIC is

1
used to transmit two different signals
2
3
4
5
6
7
8
1’
2’
3’
4’
5’
6’
7’
8’
V (H)
over one frequency. The utilization
ratio of the frequency spectrum is
H (V)
doubled. To avoid severe interference
between two different polarized signals,
the interference compensation
680 MHz
30MHz
technology must be used.
340MHz
80MHz
Electric field direction
1
2
1X
2X
3
4
5
6
7
60MHz
8
1’
2’
3’
4’
5’
6’
7’
8’
V (H)
Horizontal polarization
H (V)
3X
4X 5X
6X
7X
8X 1X’ 2X’ 3X' 4X’ 5X’ 6X’ 7X’ 8X’
Vertical polarization
Shape of waveguide interface
Frequency configuration of U6 GHz frequency band (ITU-R F.384-5)
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Page 82
Anti-fading Technologies
for Digital Microwave System (8)

Diversity technologies
For diversity, two or multiple transmission paths are used to transmit the same information
and the receiver output signals are selected or composed, to reduce the effect of fading.

Diversity has the following types, space diversity, frequency diversity, polarization diversity,
and angle diversity.

Space diversity and frequency diversity are more frequently used. Space diversity is
economical and has a good effect. Frequency diversity is often applied to multi-channel systems
as it requires a wide bandwidth. Usually, the system that has one standby channel is configured
with frequency diversity.

f1
H
Space diversity (SD)
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f2
Frequency diversity (FD)
Page 83
Anti-fading Technologies
for Digital Microwave System (9)

Frequency diversity

Signals at different frequencies have different fading characteristics. Accordingly,
two or more microwave frequencies with certain frequency spacing to transmit and
receive the same information which is then selected or composed, to reduce the
influence of fading. This work mode is called frequency diversity.

Advantages: The effect is obvious. Only one antenna is required.

Disadvantages: The utilization ratio of frequency bands is low.
f1
f2
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Page 84
Anti-fading Technologies
for Digital Microwave System (10)
 Space diversity
Signals have different multipath effect over different paths and thus have different fading
characteristics. Accordingly, two or more suites of antennas at different altitude levels to
receive the signals at the same frequency which are composed or selected. This work
mode is called space diversity. If there are n pairs of antennas, it is called n-fold diversity.


Advantages: The frequency resources are saved.
Disadvantages: The equipment is complicated, as two or more suites of antennas are
required.

Antenna distance: As per experience, the distance between the diversity antennas is
100 to 200 times the wavelength in frequently used frequency bands.
f1

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Page 85
Anti-fading Technologies
for Digital Microwave System (11)

Rx
Dh calculation in space diversity
Tx
Dh
h1
d

Approximately, Dh can be calculated according to this formula:
(nl＋l/2)d
Dh =
l: wavelength
d: path distance
h1: height of the antenna at the transmit end
2h1
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Page 86
Anti-fading Technologies
for Digital Microwave System (12)

Apart from the anti-fading technologies introduced previously, here are two
frequently used tips:

Method I: Make use of some terrain and ground objects to block reflected waves.
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Page 87
Anti-fading Technologies
for Digital Microwave System (13)

Method II: high and low antennas
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Page 88
Protection Modes of
Digital Microwave Equipment (1)
Hybrid coupler
With one hybrid coupler added between two
ODUs and the antenna, the 1+1 HSB can be
realized in the configuration of one antenna.
Moreover, the FD technology can also be
adopted.

The 1+1 HSB can also be realized in the
configuration of two antennas. In this case,
the FD and SD technologies can both be
adopted, which improves the system
availability.

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Page 89
Protection Modes of
Digital Microwave Equipment (2)

N+1 (N≤3, 7, 11) Protection
In the following figure, Mn stands for the active channel and P stands for the standby
channel. The active channel and the standby channel have their independent
modulation/demodulation unit and signal transmitting /receiving unit.

When the fault or fading occurs in the active channel, the signal is switched to the
standby channel. The channel backup is an inter-frequency backup. This protection mode
(FD) is mainly used in the all indoor microwave equipment.


Products of different vendors support different specifications.
ch1
ch2
ch3
chP
Switching
control unit
M1
M1
M2
M2
M3
M3
ch1
ch2
ch3
P
P
chP
RFSOH
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Switching
control unit
Page 90
Protection Modes of
Digital Microwave Equipment (3)
Configuration
Protection Mode
Remarks
Terminal of the network
1+0
NP
Non-protection
1+1
FD
Channel protection
1+1
SD
Equipment protection
and channel protection
Intrafrequency
1+1
FD+SD
Equipment protection
and channel protection
Interfrequency
N+1
FD
Equipment protection
and channel protection
Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Application
Interfrequency
Interfrequency
Select the proper mode
depending on the
geographical condition
and requirements of the
customer
Large-capacity
backbone network
Page 91
Questions

What factors can affect the microwave propagation?

What types of fading exists in the microwave propagation?

What are the two categories is the anti-fading technology?

What protection modes are available for the microwave?
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Page 92
Summary

Importance parameters affecting microwave propagation

Various factors affecting microwave propagation

Various fading types in the microwave propagation (free space propagation fading,
atmospheric absorption fading, rain or fog scattering fading, K type fading,
multipath fading, duct type fading, and scintillation type fading)

Anti-fading technologies

Anti-fading measures adopted on the equipment: adaptive equalization, ATPC,
and XPIC

Anti-fading measures adopted in the system: FD and SD

Protection modes of the microwave equipment
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Page 93
Contents
1. Digital Microwave Communication Overview
2. Digital Microwave Communication Equipment
3. Digital Microwave Networking and Application
4. Microwave Propagation and Anti-fading Technologies
5. Designing Microwave Transmission Links
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Page 94
Contents
5. Designing Microwave Transmission Links

5.1 Basis of Designing a Microwave Transmission Line

5.2 Procedures for Designing a Microwave Transmission Line
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Page 95
Basis of Designing a Microwave
Transmission Line

Requirement on the point-to-point line-of-sight communication

Objective of designing a microwave transmission line

Transmission clearance

Meanings of K value in the microwave transmission planning
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Page 96
Requirement on a Microwave
Transmission Line

Because the microwave is a short wave and has weak ability of diffraction, the
normal communication can be realized in the line-of-sight transmission without obstacles.
Line propagation
Irradiated wave
Antenna
D
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Page 97
Requirement on a Microwave
Transmission Line

In the microwave transmission, the transmit power is very small, only the antenna in
the accurate direction can realize the communication. For the communication of long
distance, use the antenna of greater diameter or increase the transmit power.
Direction demonstration of the microwave antenna
Microwave antenna
Half power angle of the
microwave antenna
Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
3 dB
Page 98
Objective of Designing a Microwave
Transmission Line

In common geographical conditions, it is recommended that there be no
obstacles within the first Fresnel zone if K is equal to 4/3.

When the microwave transmission line passes the water surface or the
desert area, it is recommended that there are no obstacles within the first
Fresnel zone if K is equal to 1.
The first Fresnel zone
k = 4/3
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Page 99
Transmission Clearance (1)

The knife-edged obstacle blocks partial of the Fresnel zone. This also causes
the diffraction of the microwave. Influenced by the two reasons, the level at the
actual receive point must be lower than the free space level. The loss caused by
the knife-edged obstacle is called additional loss.
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Page 100
Transmission Clearance (2)

When the peak of the obstacle is in the line
connecting the transmit end and the receive end, that
8
is, the HC is equal to 0, the additional loss is equal to
6
4
2

When the peak of the obstacle is above the line
connecting the transmit end and the receive end, the
additional loss is increased greatly.

When the peak of the obstacle is below the line
connecting the transmit end the receive end, the
additional loss fluctuates around 0 dB. The
Additional loss (dB)
6 dB.
transmission loss in the path and the signal receiving
level approach the values in the free space
transmission.
0
-2
-4
-6
-8
-10
-12
-14
-16
-18
-20
-22
-24
-26
-28
-2.5-2.0-1.5-1.0-0.5 0 0.51.0 1.5 2.0 2.5 HC/F1
Loss caused by block of knife-edged obstacle
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Page 101
Transmission Clearance (3)

Clearance calculation

Calculation formula for path clearance
h1d 2  h2 d1
hc 
 hb  hs
d
The value of clearance is
required greater than that
of the first Fresnel Zone’s
radius.

hb stands for the projecting
hc
h2
hs
h1
height of the earth.
d1
hb
d
d1d 2
hb  0.0785
K

K stands for the atmosphere refraction factor.
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Page 102
d2
Transmission Clearance (4)

To present the influence of various factors on microwave transmission, the field
strength fading factor V is introduced. The field strength fading factor V is defined as the
ratio of the combined field strength when the irradiated wave and the reflected wave
arrive at the receive point to the field strength when the irradiated wave arrives at the
receive point in the free space transmission.
 h
E
2
V 
 1    2  cos   ce
E0
  F1



2



E : Combined field strength when the irradiated wave and reflected wave
in
E0
arrive at the receive point
: Field strength when the irradiated wave arrives at the received point
free space transmission
 : the
Equivalent ground reflection factor
Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Page 103
Transmission Clearance (5)


The relation of the V and
can be
represented by the curve in the figure on the
right.

In the case that Φ is equal to 1, with the
influence of the earth considered, HC/F1 is
equal to 0.577 when the signal receiving level
is equal to the free space level the first time.

In the case that Φ is smaller than 1, HC/F1 is
V（dB）
10
5
0
-5
-20
receiving level is equal to the free space level
-25
the first time.
-30
φ＝0.8
φ＝1
-35
clearance is called the free space clearance,
-40
represented by H0 and expressed in the
0 .6
4
1 .0
4
1 .3
1
1 .4
3
1 .5
6
1 .7
6
1 .9
3
2 .0
1
2 .1
0
2 .2
6
2 .3
9
2 .4
6
2 .5
4
2 .6
6
2 .7
8
2 .8
5
3 .0
2
When the HC/F1 is equal to 0.577, the
φ＝0.5
-15
approximately equal to 0.6 when the signal

φ＝0.2
-10
HC/F1=N
following formula:
H0 = 0.577F 1 = (λd1d2/d)1/2
Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Relation curve of V and Hc/F1
Page 104
Meaning of K Value in Microwave
Transmission Planning (1)

To make the clearance cost-effective and reasonable in the engineering, the height
of the antenna should be adjusted according to the following requirements.

In the case that Φ is not greater than 0.5, that is, for the circuit that passes the
area of small ground reflection factor like the mountainous area, city, and hilly
area, to avoid over great diffraction, the height of the antenna should be
adjusted according to the following requirements:
When K = 2/3, HC ≥ 0.3F1 (for common obstacles)
HC ≥ 0 (for knife-shaped obstacles)

The diffraction fading should not be greater than 8 dB in this case.
Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Page 105
Meaning of K Value in Microwave
Transmission Planning (2)

In the case that Φ is greater than 0.7, that is, for the circuit that passes the area of
great ground reflection factor like the plain area and water reticulation area, to avoid
over great reflection fading, the height of the antenna should be adjusted according to
the following requirements
When K = 2/3, HC ≥ 0.3F1 (for common obstacles)
HC ≥ 0 (for knife-edged obstacles)
When K = 4/3, HC ≈ F1
When K = ∞, HC ≤ 1.35F1 (The deep fading occurs when HC = 21/2 F1.)

If these requirements cannot be met, change the height of the antenna or the route.
Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Page 106
Procedure for Designing a Microwave
Transmission Line

Step 1 Determine the route according to the engineering map.

Step 2 Select the site of the microwave station.

Step 3 Draw the cross-sectional chart of the terrain.

Step 4 Calculate the parameters for site construction.
Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Page 107
Procedure for Designing a Microwave
Transmission Line (1)
Step 1
Determine the route according to engineering map.

We should select the area that rolls as much as possible, such as the hilly
area. We should avoid passing the water surface and the flat and wide
area that is not suitable for the transmission of the electric wave. In this
way, the strong reflection signal and the accordingly caused deep fading
can be avoided.

The line should avoid crossing through or penetrating into the mountainous
area.

The line should go along with the railway, road and other areas with the
convenient transportation.
Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Page 108
Procedure for Designing a Microwave
Transmission Line (2)
Step 2

Select the site of the microwave station.
The distance between two sites should not be too long. The distance
between two relay stations should be equal, and each relay section should
have the proper clearance.

Select the Z route to avoid the over-reach interference.

Avoid the interference from other radio services, such as the satellite
communication system, radar site, TV station, and broadcast station.
f1
f1
f1
f2
f2
f2
Over-reach
interference
Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
The signal from the first
microwave station
interferes with the
signal of the same
frequency from the third
microwave station.
Page 109
Procedure for Designing a Microwave
Transmission Line (3)
Step 3
Draw the cross-sectional chart of the terrain.

Draw the cross-sectional chart of the terrain based on the data of each site.

Calculate the antenna height and transmission situation of each site. For the
line that has strong reflection, adjust the mounting height of the antenna to
block the reflected wave, or have the reflection point fall on the earth
surface with small reflection factor.

Consider the path clearance. The clearance in the plain area should not be
over great, and that in the mountainous area should not be over small.
Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Page 110
Procedure for Designing a Microwave
Transmission Line (4)
Step 4
Calculate the parameters for site construction.

Calculate the terrain parameters when the route and the site are already
determined.

Calculate the azimuth and the elevation angles of the antenna, distance
between sites, free space transmission loss and receive level, rain
fading index, line interruption probability, and allocated values and margin
of the line index.

When the margin of the line index is eligible, plan the equipment and
frequencies, make the approximate budget, and deliver the construction
chart.
Input
There is special network
planning software, and the
commonly used is CTE
Pathloss.
Input
Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Page 111
Questions

What are the requirements for microwave communication?

What is the goal of microwave design?

What extra factors should be taken into consideration for microwave
planning?

Can you tell the procedure for designing a microwave transmission line?
Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Page 112
Thank You
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