Mumbai University > EXTC > Sem 8 > Satellite Communication and Networks

Marks: 8M

A 12 GHz receiver consists of an RF stage with gain G1 =30dB and noise temperature T1 = 20 K, a down converter with gain G2 = 10dB and noise temperature T2 = 360 K and an IF amplifier stage with gain G3 =15 dB and noise temperature T3 = 1000 K. Calculate the effective noise temperature and noise figure of the system. Take reference temperature as 290 K. Compute the noise figure specifications of the three stages and then compute an overall noise figure from the individual noise figure specifications.

The three stages are connected in cascade.

G1 = 30 dB = 103 =1000

G2 = 10 dB = 101 =100

G3 = 15 dB = 101.5 =31.6227

The equivalent noise temperature Teq

$T_{eq}=T_{1}+\frac{T_2}{G_1} +\frac{T_3}{G_1 G_2 }$

$T_{eq}=20+\frac{360}{1000}+\frac{1000}{(1000)(100)}=20.37 K$

Equivalent noise factor of the system $F_{eq}$

$T_{eq} = (F_{eq} -1)T_o$ …