Chapter 3 : Amplitude Modulation Systems

Example 3.4 Page No : 163

In [1]:
#Transmission power effiency n  =  ((m**2)/(2+(m**2)))*100% where m is modulated index

#Given modulated indices are m1  =  0.25, m2  =  0.5 & m3  =  0.75

#Transmission power effiencies are n1, n2 & n3 respectively for m1, m2 & m3
n1  =  ((0.25**2)/(2+(0.25**2)))*100
n2  =  ((0.5**2)/(2+(0.5**2)))*100
n3  =  ((0.75**2)/(2+(0.75**2)))*100

print 'Transmission power effiency for modulated index 0.25 is %.4f'%n1, '%'
print 'Transmission power effiency for modulated index 0.5 is %.4f'%n2, '%'
print 'Transmission power effiency for modulated index 0.75 is %.4f'%n3, '%'

Transmission power effiency for modulated index 0.25 is 3.0303 %
Transmission power effiency for modulated index 0.5 is 11.1111 %
Transmission power effiency for modulated index 0.75 is 21.9512 %

Example 3.7 Page No : 185

In [4]:
import math 

#Given input inmedance of matching networkis R1  =  10 ohm & output impedance of matching networ is R2  =  50 ohm & carrier frequency is fc  =  500 KHz
R1  =  10.
R2  =  50.
fc  =  500000.

#Wc  =  2*pi*fc
Wc  =  2*math.pi*fc

#AS R1  =  R2*(X2**2)/[(R2**2)+(X2**2)], X2  =  25ohm
X2  =  25

#AS X1  =  (R2**2)*X2/[(R2**2)+(X2**2)] & R1>R2, X1  =  -20ohm
X1  =  -20

#|X1|  =  |jwL|  =  wL  =  20 & |X2|  =  |1/jwC|  =  1/wC  =  25, so |X1*X2|  =  L/C  =  500 denotes as LC_div
LC_div  =  500

#Wc**2  =  1/(L*C). LC is denoted as LC_prod
LC_prod  =  1/(Wc**2)

#In the textbook the calculated LC  =  10**-3, in reality the value of LC  =  1.013D-13
 
L  =  math.sqrt(LC_div*LC_prod)

#In the textbook the calculated L**2  =  50*10**-14, in reality the value of L**2  =  5.066D-11  
 
C  =  L/500

#In the textbook the calculated C  =  1.4*10**-9, in reality the value of C  =  1.424D-08  

print 'Inductance %.3e'%L,' H'
print 'Capacitance %.3e'%C,' F'

Inductance 7.118e-06  H
Capacitance 1.424e-08  F

Example 3.8 Page No : 185

In [4]:
#Given ohmnic loss resismath.tance is Ro  =  12 Ohm,  
Ro  =  12.
#radiation resismath.tance is Rr  =  48 Ohm,
Rr  =  48.
#directivity is D  =  2
D  =  2.
#Input current  =  0.1*math.cos[2*pi*(10**6)*t], Amplitude of input current is A  =  0.1 Amp
A  =  0.1
#Equivalent resismath.tance  =  Re  =  Ro+Rr
Re  =  Ro+Rr

#Total power used in antenna  =  Pin  =  (A**2)*Re/2
Pin  =  (A**2)*Re/2

#Power used in radiation  =  Prad  =  (A**2)*Rr/2
Prad  =  (A**2)*Rr/2

#Efficiency of the antenna  =  n  =  Prad/Pin
n  =  Prad/Pin

#Gain of antenna  =  Ga  =  efficiency*directivity
Ga  =  n*D

print 'Total power used in antenna ',Pin,' Watt'
print 'Power used in radiation ',Prad,' Watt'
print 'Efficiency of the antenna ',n
print 'Gain of antenna ',Ga

Total power used in antenna  0.3  Watt
Power used in radiation  0.24  Watt
Efficiency of the antenna  0.8
Gain of antenna  1.6