# chapter 05 : Practical Antennas-I¶

## Exa 5.1 : page 5.57¶

In [26]:
from math import pi
#For Single Turn:
from sympy import symbols, sqrt
lamda = symbols('lamda')
a=lamda/25
A=pi*pow(a,2)
Rr = (A/lamda**2)**2*31171.2
print "radiation Resistance =",round(Rr,4),"Ohm for single turn "

#For Eight Turn:
N=8 #no. of turns
Rr=Rr*N**2 #in Ohm
print "radiation Resistance = %0.2f Ohm for Eight turn " %Rr

radiation Resistance = 0.7876 Ohm for single turn
radiation Resistance = 50.40 Ohm for Eight turn


## Exa 5.2 : page 5.58¶

In [32]:
from math import pi, acos, sqrt
#Given data :
f=20.0 #in MHz
N=15.0 #No. of turns
A=2.0 #in m**2
Vrms=200.0 #in uV
mu_o=4*pi*10**-7 #in H/m
#Formula : Vm=2*pi*f*mu_o*H*A*N
Vm=Vrms*sqrt(2) #in uV
H=(Vm*10**-6)/(2.0*pi*f*10**6*mu_o*A*N) #in A/m
print "Peak Value of magnetic feld intensity = %0.3e mA/m " %(H*1000)
#Note : Answer in the book is wrong.

Peak Value of magnetic feld intensity = 5.970e-05 mA/m


## Exa 5.3 : page 5.58¶

In [35]:
from math import sqrt
#Given data :
f=20 #in MHz
f=f*10**6 #in Hz
Wmax=25 #in mW/m**2
A=10.0 #in m**2
c=3*10**8 #speed of light in m/s
lamda=c/f #in meter
Rr=31171.2*(A/lamda**2)**2 #iin Ohm
#Formula : Wmax=V**2/(4*Rr)
V=sqrt(Wmax*10**-3*4*Rr) #in Volts
print "Maximum emf in the loop = %0.3f Volts "%V

Maximum emf in the loop = 2.481 Volts


## Exa 5.4 : page 5.59¶

In [36]:
from math import pi
#Given data :
N=20.0 #turns
D=1.0 #in meter
r=D/2 #in meter
E=200*10**-6 #in V/m
L=50*10**-6 #in H
R=2.0 #in Ohm
f=1.5 #in MHz
f=f*10**6 #in Hz
c=3*10**8 #speed of light in m/s
lamda=c/f #in meter
A=pi*r**2 #in m**2
Vrms=2*pi*E*A*N/lamda #in Volts
Q=2*pi*f*L/R #unitless
Vc_rms=Vrms*Q #in Volts
print "Voltage across the capacitor = %0.2f mV" %(Vc_rms*1000)
#Note : Answer in the book is wrong.

Voltage across the capacitor = 23.25 mV


## Exa 5.5 : page 5.59¶

In [40]:
from math import pi, cos
#Given data :
N=100 #No. of turns
A=2 #in m**2
f=10 #in MHz
f=f*10**6 #in Hz
Q=150 #Quality factor
c=3*10**8 #speed of light in m/s
lamda=c/f #in meter
Erms=10*10**-6 #in V/m
theta=60 #in degree
Vrms=2*pi*Erms*A*N*cos(theta*pi/180)/lamda
Vin=Vrms*Q #in Volts
print "Voltage to the receiver = %0.1f mV  " %(Vin*1000)
#Note : Answer in the book is wrong.

Voltage to the receiver = 31.4 mV