11) The type of antenna to be used for producing circularly polarized beams is
a) pyramidal horn
b) log-periodic array
c) paraboloid
d) helical antenna
12) In LOS-line of sight propagation systems, to take account of normal refraction, an effective earth radius factor k is used whose value is
a) 4/3
b) 4
c) ¾
d) ½
13) Which is the most common antenna to obtain a predetermined radiation pattern ?
a) Array antenna
b) Corner reflector
c) Sectoral horn
d) Helical antenna
14) Why is an attenuator used in a TWT ?
a) To help bunching
b) To prevent oscillations
c) To prevent saturation
d) To increase gain
15) For a parabolic reflector of 5 meter diameter, the far field pattern measurement at 6 GHz should be carried out a distance of at least
a) o.5 km
b) 1.0 km
c) 1.5 km
d) 2.0 km
16) Which of the following are microwave sources ?
a) klystron
b) Magnetron
c) IMPATT
d) TWTA
17) X-band frequencies are in which one of the following ranges?
a) 3.5 to 5.5 GHz
b) 5.5 to 8.0 GHz
c) 8.0 to 12.0 GHz
d) 12.4 to 16.4 GHz
18) In microwave communication links, what causes intense fading in the 18GHz band ?
a) Snow
b) Rain
c) Fog
d) Dust
19) A amplifier has a power gain of 200. What is its gain in dB? (log10 2 = 0.30)
a) 14 dB
b) 17 dB
c) 20 dB
d) 23 dB
20) Which of the following modes can exist in a rectangular wave guide ?
a) TM10
b) TE10
c) TM00
d) TM01
21) Which one of the following is a transferred electron device ?
a) BARITT diode
b) IMPATT diode
c) TRAPATT diode
d) Gunn DIODE
22) Which of the following is a circularly polarized antenna ?
a) Horn
b) Dipole
c) Helical
d) Pyramidal
23) The main disadvantage of using coaxial cable for microwave signals is its
a) Low selectivity
b) Low distortion
c) High attenuation
d) High sensitivity
24) Which is the dominant mode in rectangular waveguides ?
a) TE10
b) TE11
c) TM01
d) TM11
25) A Gunn diode is a negative resistance device, which is used as source of microwaves. What is the number of p-n junctions ?
a) 1
b) 2
c) 3
d) 0
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