Chapter 4: Radiation

Example 4-4.1, Page number: 75

import math

#Variable declaration
theta = 30              #Angle of radiation (degrees)
epsilon_0 = 8.854e-12   #Permittivity of free space (F/m)
I_dl = 10               #Current in length dl (A-m)
r = 100e3               #Distance of point from origin (m)

#Calculation
E_mag = (I_dl*math.sin(theta*math.pi/180))/(4*math.pi*epsilon_0)
                        #Magnitude of Electric field vector (V/m)
H_mag = (I_dl*math.sin(theta*math.pi/180))/(4)
                        #Magnitude of Magnetic field vector (T)

#Result
print "The magnitude of E vector is ", round(E_mag,-9), "V/m"
print "The magnitude of H vector is", round(H_mag, 3), "/pi T"

The magnitude of E vector is  45000000000.0 V/m
The magnitude of H vector is 1.25 /pi T

Example 4-4.2, Page number: 76

import math

#Variable declaration
v = 3e8         #Speed of light(m/s)
f = 10e6        #Frequency (Hz)

#Calculation
w = 2*math.pi*f     #Angular frequency(rad/s)
r = v/w             #Distance (m)

#Result
print "The distance for the specified condition is", round(r, 2), "m"

The distance for the specified condition is 4.77 m

Example 4-4.3, Page number: 76

import math

#Variable declaration
c = 3e8             #Speed of light (m/s)
f = 3e9             #Frequency (Hz)

#Calculation
v = 0.6*c           #60% of velocity of light (m/s)
w = 2*math.pi*f     #Angular frequency (rad/s)
r = v/w             #Distance (m)

#Result
print "The distance for the specified condition is", round(r,6), "m"

The distance for the specified condition is 0.009549 m

Example 4-5.1, Page number: 80

import math

#Variable declaration
dl = 1e-2       #Length of radiating element (m)
I_eff = 0.5     #Effective current (A)
f = 3e9         #Frequency (Hz)
c = 3e8         #Velocity of light (m/s)

#Calculation
w = 2*math.pi*f     #Angular Frequency (rad/s)
P = 20*(w**2)*(I_eff**2)*(dl**2)/(c**2)     #Radiated power (W)

#Result
print "The radiated power is", round(P, 2), "W"

#The final result is incorrect in the book because of the calculation mistake

The radiated power is 1.97 W

Example 4-5.2, Page number: 80

#Variable declaration
L = 5         #Length of radiating element (m)
f1 = 30e3     #Frequency (Hz)  
f2 = 30e6     #Frequency (Hz)  
f3 = 15e6     #Frequency (Hz)
c = 3e8       #Velocity of light (m/s)  

#Calculation
wave_lt1 = c/f1                 #Wavelength (m)
wave_lt1 /= 10
R_r1 = 800*(L/wave_lt1)**2      #Radiation resistance (ohm)

wave_lt2 = c/f2                 #Wavelength (m)
L = wave_lt2/2                  #Effective length (m)
R_r2 = 200*(L/wave_lt2)**2      #Radiation resistance (ohm)

wave_lt3 = c/f3                 #Wavelength (m)
L = wave_lt3/4                  #Effective length (m)
R_r3 = 400*(L/wave_lt3)**2      #Radiation resistance (ohm)

#Result
print "The radiation resistance for f1 is", R_r1, "ohms"
print "The radiation resistance for f2 is", round(R_r2), "ohms"
print "The radiation resistance for f3 is", round(R_r3), "ohms"

The radiation resistance for f1 is 0.02 ohms
The radiation resistance for f2 is 50.0 ohms
The radiation resistance for f3 is 25.0 ohms

Example 4-6.1, Page number: 82

import math

#Variable declaration
Im = 5              #Maximum current (A)
r = 1e3             #Distance (km)
eta = 120*math.pi   #Intrinsic impedence (ohm)
theta = 60*math.pi/180          #Angle of radiation (radians)

#Calculation
sin2 = math.sin(theta)**2       #Sine squared theta (unitless)
P_av = (eta*(Im**2))/(8*(math.pi**2)*(r**2))
P_av = P_av*(math.cos(math.pi/2*math.cos(theta))**2)/(sin2)
                        #Average power (W)
                        
#Result
print "The average power available at 1km distance is", round(P_av,9), "W"

The average power available at 1km distance is 7.9577e-05 W