Chapter 11: Antennas

Example 11.1, page no. 292

In [16]:
# Variable Declaration
f1      = 1.00*pow(10,6)  # Operating Frequency (Hz)
f2      = 10.00*pow(10,3) # Operating Frequency (Hz)
c       = 3.00*pow(10,8)  # Speed of light in vacuum (m/s)

# Calculation
Lambda1 = c/f1          # Mechanical Length (m)
Lambda2 = c/f2            # Mechanical Length (m)

# Result
print "(a) Mechanical Length at 1 MHz, Lambda1 =",round(Lambda1),"m"
print "(b) Mechanical Length at 10 kHz, Lambda2 =",round(Lambda2),"m"
print "    Increase in Length =",round(Lambda2/Lambda1),"times"

(a) Mechanical Length at 1 MHz, Lambda1 = 300.0 m
(b) Mechanical Length at 10 kHz, Lambda2 = 30000.0 m
    Increase in Length = 100.0 times

Example 11.2, page no. 294

In [15]:
# Variable Declaration 
f      = 1.00*pow(10,6)                                            # Operating Frequency (Hz)
Le     = 30                                                        # Hertzian Dipole Length (m)
I      = 5                                                         # Current value (A)
r      = 1.00*pow(10,3)                                            # Distance (m)
Theeta = 90                                                        # Angle (degrees)
c      = 3.00*pow(10,8)                                            # Speed of light in vacuum (m/s)

# Calculation
import math
Lambda = c/f                                                       # Wavelength (m)
E      = ((60*math.pi*Le*I)/Lambda*r)*math.sin(Theeta*math.pi/180) # Calculation of Field Strength (s/m)

# Result
print "Field Strength at a distance of 1 km and at an angle of 90 degrees, E =",round(E/(math.pi*pow(10,3))),"*pi*10^(-3) us/m"

Field Strength at a distance of 1 km and at an angle of 90 degrees, E = 30.0 *pi*10^(-3) us/m

Example 11.3, page no. 296

In [17]:
# Variable Declaration 
f   = 500*pow(10,3)         # Operating Frequency (Hz)
vel = 3.00*pow(10,8)        # Speed of light in vacuum (m/s)
Vf  = 0.95                  # Velocity Factor

# Calculation
import math                 # Math Library
Le  = vel/f*Vf              # Length of the antenna (m)

# Result
print "The Length of the Antenna, Le =",round(Le),"m or",round(Le*3.936),"ft"

The Length of the Antenna, Le = 570.0 m or 2244.0 ft

Example 11.4, page no. 299

In [18]:
# Variable Declaration 
P1 = 1*pow(10,3)          # Power of Half Wave Dipole antenna (w)
A = 2.15                  # Gain (dB)

# Calculation
import math               # Math Library
P2 = pow(10,A/10)*P1      # Power delivered (w)

# Result
print "The power delivered to the isotropic antenna to match the field strength of directional antenna, P2 =",round(P2,1),"W"

The power delivered to the isotropic antenna to match the field strength of directional antenna, P2 = 1640.6 W

Example 11.5, page no. 300

In [19]:
# Variable Declaration 
P          = 1.00*pow(10,3)       # Input Power (W)
field_gain = 2           # Field Gain
E          = 0.5                  # (*100) Efficiency (%)

# Calculation
import math                       # Math Library
Po         = P*E                  # Power fed (W)
erp        = Po*pow(field_gain,2) # Effective Radiated Power (w)


# Result
print " The Effective Radiated Power, erp =",round(erp),"W"

 The Effective Radiated Power, erp = 2000.0 W

Example 11.6, page no. 300

In [20]:
# Variable Declaration 
P_in = 800               # Input Power (W)
E_lost = 0.25            # (*100) Loss Percentage (%)

# Calculation
import math              # Math Library
Pd     = E_lost*P_in     # Power Lost (W)
P_rad  = P_in-Pd # Radiated Power (W)

# Result
print "Radiated Power, P_rad =",round(P_rad),"W"

Radiated Power, P_rad = 600.0 W

Example 11.7, page no. 301

In [10]:
# Variable Declaration 
R_rad = 100              # Radiation Resistance (Ohms)
E     = 0.75             # (*100) Efficiency (%)

# Calculation
import math              # Math Library
Rd    = R_rad/E-R_rad    # Antenna Resistance (Ohms)

# Result
print "Antenna Resistance, Rd =",round(Rd,2),"Ohms"

Antenna Resistance, Rd = 33.33 Ohms

Example 11.8, page no. 309

In [21]:
# Variable Declaration 
Zs = 5          # Impedance of the transmission line (Ohms)
Zr = 70                  # Impedance of the antenna (Ohms)

# Calculation
import math              # Math Library
Z  = Zs*Zr             # Characteristic Impedance (Ohms)

# Result
print "The characteristic impedance of the matching section, Z =",round(Z),"Ohms"

The characteristic impedance of the matching section, Z = 350.0 Ohms

Example 11.9, page no. 316

In [22]:
# Variable Declaration 
D      = 2               # Mouth diameter of reflector (m)
f      = 6.00*pow(10,9)  # Operating Frequency (Hz)
c      = 3.00*pow(10,8)  # Speed of light in vacuum (m/s)

# Calculation
import math              # Math Library
Lambda = c/f       # Wavelength (m)
phi_o  = 2*70*Lambda/D   # Beam width between nulls of a paraboloid reflector (degrees)

# Result
print "The beam width between nulls of a paraboloid reflector, phi_o =",round(phi_o,1),"degrees"

The beam width between nulls of a paraboloid reflector, phi_o = 3.5 degrees

Example 11.10, page no. 317

In [13]:
# Variable Declaration 
D      = 200                  # Mouth diameter of reflector (m)
Lambda = 5                    # Wavelength (m)

# Calculation
import math                   # Math Library
Ap     = 6*pow(D/Lambda,2)    # Gain of the antenna

# Result
print " The gain of the antenna, Ap =",round(Ap)

 The gain of the antenna, Ap = 9600.0