Calculate the directivity of an antenna for ?E = 30�, ?H = 60 46 23 50 100 .

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Question
Calculate the directivity of an antenna for ?_E = 30�, ?_H = 60
Options
A. 46
B. 23
C. 50
D. 100

Correct Answer

23

Explanation

Calculate the directivity of an antenna for ?E = 30�, ?H = 60 46 23 50 100 .

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Electromagnetic Field Theory problems

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1. Two identical antennas are placed in the ? = p/2 plane as shown in the figure. The elements have equal amplitude excitation with 180� polarity difference, operating of the far-zone resultant electric field strength normalized with that of a single element, both computed for ? = 0, is
Options
A.
B.
C.
D.

2. A rectangular metal waveguide filled with a dielectric of relative permittivity ?_r = 4, has the inside dimensions 3 x 1.2 cm, the cut off frequency for the dominant mode is
Options
A. 2.5 GHz
B. 5 GHz
C. 10 GHz
D. 12.5 GHz

3. A broadside array operating at 100 cm wavelength consist of 4 half-wave dipoles spaced 50 cm apart. Each element carries radio frequency current in the same phase and of magnitude 0.5 A. The radiated power will be
Options
A. 196 W
B. 73 W
C. 36.5 W
D. 18.25 W

4. The divergence of the electric field intensity at any point equals
Options
A. 1/4 p?₀ times the volume charge density
B. l/?₀ times the volume charge density at that point
C. ?₀ times the volume charge density at that point
D. the volume charge density at that point

5. Radiation intensity of a dipole depends strongly on frequency. If at a frequency f, the intensity of radiation is 'I'. Then at a frequency of f/2, the intensity will be
Options
A.
B.
C.
D.

6. A broadside array consisting of 200 cm wavelength with 10 half-wave dipole spacing 10 cm. And if each array element feeding with 1 amp. current and operating at same frequency then find the half power beamwidth
Options
A. 4�
B. 2�
C. 10�
D. 15�

7. A wave is propagated in a waveguide at frequency of 9 GHz and separation is 2 cm between walls find cut off wavelength for dominant mode.
Options
A. 4 cm
B. 1 cm
C. 2 cm
D. 8 cm

8. A (75 - j 40) W load is connected to a co-axial line of z₀ = 75? at 6 MHz. The load matching on the line can be accomplished by connecting
Options
A. a short circuit stub at the load
B. an inductance at the load
C. a short circuit stub at a specific distance from the load
D. a capacitance at a specific distance from the load

9. The electric field of the incident wave is , where ? = 3 x 10⁹p and ? = 10 p. The electric field of the transmitted wave E_t is given by
Options
A.
B.
C.
D.

10. The electric field on the surface of a perfect conductor is 2V/m. The conductor is immersed in water with ? = 80 ?₀. The surface charge density on the conductor is ((?₀ = 10^-9/36p)F/m)
Options
A. 0 c/m²
B. 2 c/m²
C. 1.8 x 10^-11 c/m²
D. 1.14 x 10^-9 c/m²

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