# Chapter 3 : Amplitude Modulation Systems¶

## Example 3.4 Page No : 163¶

In :
#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 :
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 :
#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

#Efficiency of the antenna  =  n  =  Prad/Pin

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

print 'Total power used in antenna ',Pin,' Watt'

Total power used in antenna  0.3  Watt