Digital Communication
Report : Lab 0
11 January 2020
Ajay Ramesh Ranganathan (IMT2017502)
_____________________________________________________________________________________
Q1) Free Space Path Loss Model - The linear path loss of a channel is defined as the ratio of
transmit power to receive power.
P
loss
=
P
t
P
r
The path loss in decibels is given by -
(dB) 10log ( )P
loss
=
10
P
t
P
r
The Friss free space equation is given by -
P
r
P
t
=
(4πd)
2
G G λ
t
r
2
Where G
t
and G
r
are the transmitter and receiver antenna gains, is the wavelength of theλ
carrier signal and d is the distance between the transmitter and receiver antennas.
The free space path loss in decibels is -
20log ( )L =
10
λ
4πd
The free space path loss in decibels vs distance between the antennas for different carrier
frequencies is shown in the following graph. Wavelength of the carrier signal is obtained as -
λ =
c
f
c
Where c is the speed of light (electromagnetic wave).
Q2)
