Networking. Wireless Communication Assignment

Networking
Wireless Communication
Task and Research Project
Student Name –
Student ID -

Task 1: Microwave Link Budget Design
Frequency = 20 GHz = f
Transmission capacity ( at both transmitter and receiver sides ) = 4 Mbps
Antenna diameter = 0.5 m = d
Transmitter
RF Output Power – High
Power Version:
+20 dBm At Transmission port
Tx RF Branching loss 2 dB From Transmitter to antenna

Receiver
Rx RF Branching loss 2 dB From Antenna to Receiver
Figure 1: Microwave Link Configuration
1. Assume free space conditions.
Wavelength = λ = c / f = 3 x 10 8 / 20 x 10 9 = 0.015 m
Nominal Receive Signal Level ( RSL ) at the input of the receiver ( in dBm ) = ?
RSL = IRL ( dBm ) + Gtx – TLLtx – FSLrx + Grx – TLLrx

FSL = 20 log 10 (4 ∏ * distance / λ )
Grx = Gtx = 20 log 10 (4 ∏ * A / λ 2)
RSL = 20 dBm – 2 – 1 -1 -1 -2 - 20 log ( 4 ∏ 500 / 0.015) - 20 log ( 4 ∏ 5000 / 0.015)
+ 4 * 10 log ( 4 ∏ A / 0.015 * 0.015)
= 20 dBm – 7 - 20 log ( 4 ∏ 500 / 0.015) - 20 log ( 4 ∏ 5000 / 0.015) + 4 * 10 log ( 4
∏ 0.25 * 0.25 / 0.015 * 0.015)
= 20 dBm – 7 – 112.4 – 132.44 + 141.7 = 20 dBm -110.14 dB
2. Purpose of the passive repeater in the system :
A passive repeater is used for installation in remote areas. They help to reflect the
radio signal from an antenna at a distance. They do not need power of their own. They
are small in size and have a small weight. Hence, it is easy to transport them by using
helicopters and trucks. It is also called passive radio link deflection. It is a panel
( reflective or refractive ) or an object and helps to close a microwave link or radio
link. It is used if any obstacle does not allow the line of sight ( LOS ) / direct
communication and the signal path is blocked. It is very simple and needs very less
maintenance. It does not need extra frequencies. The signal that is returned is weak, if
no amplification is used.