Terrestrial Microwave
TK2133
A103418 Lee Hau Sem
A103411 Lai Horng Meau
What is Terrestrial Microwave ?
• transmission systems consisting of at least two
radio transmitter/receivers (transceivers)
connected to high gain antennas (directional
antennas which concentrate electromagnetic or
radio wave energy in narrow beams) focused in
pairs on each other.
• The operation is point-to-point-communications
are established between two and
only two antennas with line-of-sight visibility.
• This can be contrasted to point-tomultipoint systems like broadcast radio or
television.
How Terrestrial Microwave
Transfer and Receive Data
• Terrestrial microwave communication employs
Earth-based transmitters and receivers to transfer
and receive data.
• The frequencies used are in the low-gigahertz
range, which limits all communications to line-ofsight.
• Example of terrestrial microwave equipment telephone relay towers, which are placed every
few miles to relay telephone signals cross country.
Antenna That Use to Transfer
Data
• Microwave transmissions typically use a parabolic
antenna that produces a narrow, highly directional
signal.
• A similar antenna at the receiving site is sensitive
to signals only within a narrow focus.
• Because the transmitter and receiver are highly
focused, they must be adjusted carefully so that
the transmitted signal is aligned with the receiver.
An Antenna is :
An effective interface between the radio and free
space:
Free space
Radio
Antenna
For Terrestrial Communications, antennas must be
directional:
Radio
Formula Parabolic Antenna
Directive Gain
Ga (dBi) = 10 log10 h [ 4 p Aa / l2 ]
Where:
Ga = Antenna Directive Gain (Catalog spec)
h
= Aperture Efficiency (50-55%)
Aa = Antenna Aperture Area
l
= Wavelength (speed of light / frequency)
Typical Parabolic
Antenna Gain in dBi
Frequency
Antenna Diameter
2 GHz
4 GHz
6 GHz
8 GHz
11 GHz
15 GHz
18 GHz
22 GHz
38 GHz
2 ft
(0.6m)
19.5
25.5
29.1
31.6
34.3
37
38.6
40.4
45.1
4 ft
(1.2m)
25.5
31.6
35.1
37.6
40.4
43.1
44.6
46.4
51.1
6 ft
(1.8m)
29.1
35.1
38.6
41.1
43.9
46.6
48.2
49.9
NA
8 ft
(2.4m)
31.6
37.6
41.1
43.6
46.4
49.1
50.7
NA
NA
10 ft
(3.0m)
33.5
39.5
43.1
45.5
48.3
51
NA
NA
NA
12 ft
(3.7m)
35.1
41.1
44.6
47.1
49.9
52.6
NA
NA
NA
15 ft
(4.5m)
37
43.1
46.6
49.1
51.8
NA
NA
NA
NA
Standard Parabolic Antenna
• Basic Antenna
• Comprised of
– Reflector
– Feed Assembly
– Mount
Terrestrial Microwave Antennas for
Point-To-Point Communication
• Terrestrial microwave antennas generate a beam
of RF signal to communicate between two
locations.
• Point-To-Point communication depends upon a
clear line of sight between two microwave
antennas.
• Obstructions, such as buildings, trees or terrain
interfere with the signal.
• Depending upon the location, usage and
frequency, different types can be utilized.
• We will address the basic characteristics of
these various types…
The Use of Microwave Link
• A microwave link frequently is used to transmit
signals in instances in which it would be
impractical to run cables.
• If you need to connect two networks separated by
a public road,
• for example, you might find that regulations
restrict you from running cables above or below
the road. In such a case, a microwave link is an
ideal solution.
Ability To Connect With Other
Devices
• Some LANs operate at microwave frequencies at
low power and use unidirectional transmitters and
receivers.
• Network hubs can be placed strategically
throughout an organization, and workstations can
be mobile or fixed.
• This approach is one way to enable mobile
workstations in an office setting.
Frequencies That Use By
Terrestrial Microwave
• In many cases, terrestrial microwave uses
licensed frequencies.
• A license must be obtained from the FCC,
and equipment must be installed and
maintained by licensed technicians.
Frequencies That Use By
Terrestrial Microwave
• Terrestrial microwave systems operate in the lowgigahertz range, typically at 4-6 GHz and 21-23
GHz, and costs are highly variable depending on
requirements.
• Long-distance microwave systems can be quite
expensive but might be less costly than
alternatives. (A leased telephone circuit, for
example, represents a costly monthly expense.)
• When line-of-sight transmission is possible, a
microwave link is a one-time expense that can
offer greater bandwidth than a leased circuit.
Advantages of Terrestrial
Microwave over Satellite
• Lower cost
– Avoid exorbitant costs of leasing satellites (unless
satellites are already owned by the customer)
• Reduced latency
– Video is delivered with minimal delay. Satellite signals
must travel significantly further with an average delay
of 250 milliseconds for signals to travel to a geosatellite and return to earth (this excludes video
processing delay).
Advantages of Terrestrial
Microwave over Satellite
• Increased Flexibility
– BMS terrestrial systems are easily reconfigurable for
different power levels and frequencies.
– BMS terrestrial systems are mobile and easily deployed
wherever coverage is needed. Multiple satellites may
need to be utilized for all the required coverage areas.
– Video can be captured using light weight, mobile
equipment in difficult-to-reach areas. Video can also be
captured by moving aircraft, ships, and vehicles.
– Aircraft with BMS digital microwave for line-of-sight
(LOS) communications can also be equipped with a
satellite tracking antenna for beyond-line-of-sight
(BLOS) satellite communications when needed.
Advantages of Terrestrial
Microwave over Satellite
• Reduced Size & Weight
– The RF link operates over a shorter distance and
requires less power than a satellite equivalent. Lower
power means less weight, smaller size and reduced
power consumption.
– Ground-based systems can use a tracking antenna for
higher gain. Higher antenna gain results in lower
transmit power requirements. This is less practical for
satellite mounted antennas.