Chapter 14 : Communication Systems and Component Noises¶

Example 14.1 Page No : 738¶

In [1]:
import math

#Boltzman consmath.tant  k  =  1.3806488 × 10-23 m2 kg s-2 K-1
k  =  1.3806488 * 10**-23;

#Let room temperature be 27 C
T  =  27. + 273;

#Bandwidth BW  =  10 MHz
BW  =  10. * 10 **6;

#For (a)
#Let the equivalent resismath.tance be Ra
Ra  =  10. + 10;

#RMS Noise Voltage be Va
Va  =  (4*k*T*Ra*BW)**0.5;

print 'The rms voltage at output a is %.3e'%Va,' Volt'

#For (b)
#Let the equivalent resismath.tance be Rb
Rb  =  (10. * 10)/(10+10);

#RMS Noise Voltage be Vb
Vb  =  (4*k*T*Rb*BW)**0.5;

print 'The rms voltage at output b is %.3e'%Vb,' Volt'

#For (c)

Rc  =  10;
C  =  1*10**-9;

#In the textbook, the author has forgotten to multiply the result with T, hence has obtained an erroneous result.
#The given answer is 28.01uV but the correct answer is found out to be 1.2uV

def f0(f):
return Rc/(1 + (2*math.pi*Rc*C*f)**2)

Vc  =  Vc_square**0.5;

print 'The rms voltage at output c is %.3e'%Vc,' Volt'

The rms voltage at output a is 1.820e-06  Volt
The rms voltage at output b is 9.102e-07  Volt
The rms voltage at output c is 7.022e-08  Volt


Example 14.2 Page No : 741¶

In [2]:
#The Antenna noise temperature is T_ant  =  10 K
T_ant  =  10;

#The reciever noise temperature is Te  =  140 K
Te  =  140;

#Midband available gain of reciever gao  =  10**10
gao  =  10**10;

#Noise bandwidth is BN  =  1.5 * 10**5 Hz
BN  =  1.5 * 10**5;

#Boltzman consmath.tant  k  =  1.3806488 × 10-23 m2 kg s-2 K-1
k  =  1.3806488 * 10**-23;

#Available noise power at output is pao

pao  =  gao*k*(T_ant + Te)*BN;

print 'The available output noise power is %.3e'%pao,' Watts'

The available output noise power is 3.106e-06  Watts


Example 14.3 Page No : 748¶

In [3]:
#The dismath.tance d  =  30 * 1.6 * 10**3 m;
d  =  30 * 1.6 * 10**3;

#Frequency f  =  4 * 10**9 Hz
f  =  4 * 10**9;

#Wavelength w  =  c/f m
w  =  3.*10**8 / f;

#Transmitter gain KT  =  40 dB
KT  =  10**4;

#Reciever gain KT  =  40 dB
KR  =  10**4;

#Reciever power PR  =  10**-6 Watt
PR  =  10**-6;

#Transmitter power PT
PT  =  PR*(4*math.pi*d/w)**2/ (KT*KR);

print 'The transmitter output is %.4f'%PT,' Watt'

The transmitter output is 0.6468  Watt