chapter 2 Amplitude Modulation-Transmission

Example 2.1 Page no 74

In [1]:
# given
c=1.4*10**6             #frequency of carrier wave,Hz
m1=20                   #frequency component,Hz
m2=10*10**3             #KHz

#calculation 
Ur1=c+m1
Ur2=c+m2
Lr1=c-m1
Lr2=c-m2

#result
#range of upper sideband(usb)
print"upper sideband will include frequencies from  ",Ur1,"Hz"
print"to  ",Ur2,"Hz"
#range of lower sideband (lsb)
print"lower sideband will include frequencies from ",Lr2,"Hz"
print"to  ",Lr1,"Hz"

upper sideband will include frequencies from   1400020.0 Hz
to   1410000.0 Hz
lower sideband will include frequencies from  1390000.0 Hz
to   1399980.0 Hz

Example 2.2 Page no 78

In [3]:
# given
b=100.0                       #maximum p-p carrier (V)
a=60.0
d=125.0
c=35.0
x=180
y=0

#Calculation
m1=((b-a)/(b+a))*100
m2=((d-c)/(d+c))*100
m3=((x-y)/(y+x))*100

#result
print"(a) percent(m) =  ",m1,"percent"
print"(b) percent(m) = ",m2,"percent"
print"(c) percent(m) = ",m3,"percent"
print"(d) this is a case of overmodulation"
print"(e) this is a distorted AM wave as the increase > decrease in carrier's amplitude"

(a) percent(m) =   25.0 percent
(b) percent(m) =  56.25 percent
(c) percent(m) =  100 percent
(d) this is a case of overmodulation
(e) this is a distorted AM wave as the increase > decrease in carrier's amplitude

Example 2.3 Page no 79

In [5]:
#given
c=1*10**3       #carrier output

#calculation
esb= 1/4.0*(c)
tsp=(esb*2)
tp=(tsp+c)

#result
print"Total transmitted power =",tp,"W"

Total transmitted power = 1500.0 W

Example 2.4 Page no 81

In [6]:
# given
m=0.9                           #modulation index
Pc=500                          #carrier Power 

#calculation
x=(m**2)/2.0
y=(1+x)*Pc

#result
print"total transmitted power=  ",y,"W"               #total transmitted powwer

total transmitted power=   702.5 W

Example 2.5 Page no 81

In [7]:
# given
m=0.95                                                     #modulation index
Pt= 50*10**3                                               #total transmitted power

#calculation
x=(m**2)/2.0
y=1+x
z=(Pt/y)
Pi=Pt-z

#result
print"Pc = ",round(z,2),"W"                                #carrier power
print"total intelligence power = ",round(Pi,2),"W"         #intelligence signal

Pc =  34453.06 W
total intelligence power =  15546.94 W

Example 2.6 Page no 81

In [9]:
# given
Ic=12                             #antenna current of AM transmitter when unmodulated
It=13                             #current when modulated

#calculation
import math
x=2*((13/12.0)**2-1)
m=math.sqrt(x)
a=m*100

#result
print"percent(m) = ",round(a,0),"percent"            

percent(m) =  59.0 percent

Example 2.7 Page no 82

In [14]:
# given
n=0.7                                    #efficiency
c=10*10**3                               #carrier wave

#calculation
Is=0.5*c                                 #intelligence signal
p=(Is/n)

#result
print"dc input power = ",round(p,2),"W"       #dc input power

dc input power =  7142.86 W

Example 2.8 Page no 82

In [15]:
#given
Pc=10.0*10**3                                  #carrier power
Pt=11.2*10**3                                  #transmitted power
m2=0.5                                         #modulation index of another sine wave

#calculation
import math
x=2*((Pt/Pc)-1)
m=math.sqrt(x)
meff=math.sqrt((m**2)+(m2**2))
a=Pc*(1+((meff**2)/2.0))

#result
print"Pt = ",a,"W"                             #total transmitted power

Pt =  12450.0 W

Example 2.9 Page no 100

In [4]:
# given
v1=1.0
v2=0.03
v3=0.05
v4=0.02
v5=0.04

#calculation
import math
x=math.sqrt((v2**2+v3**2+v4**2+v5**2)/v1**2)
y=x*100

#result
print"THD = ",round(y,2),"percent"            #Total harmonic distortion      

THD =  7.35 percent