1. In which of the following bands the horn antenna operates?
a) HF and VHF
b) UHF and LF
c) UHF and SHF
d) LF and VHF
Explanation: Horn antenna is used in the frequency range 300MHz to 30GHZ. So, it is used in UHF and SHF frequency bands.
HF- VHF: 3MHz to 300MHz
LF-UHF: 30kHz to 3GHz
LF-VHF: 30kHz to 300MHz
2. In a horn antenna, with increase in aperture, the directivity is ____ and diffraction is ______
a) increased, decreased
b) decreased, increased
c) increased, increased
d) decreased, decreased
Explanation: Horn antenna is designed to improve the directivity and reduce the diffractions. It is used to properly match the waveguide to a large radiating aperture by shaping transition gradually. So, reflections are also decreased.
3. In Horn antennas impedance matching is provided by _______
a) flaring
b) increasing Power
c) decreasing axial length
d) Balun
Explanation: In horn antennas, we use Flaring technique for impedance matching. The sides of the waveguide are flared to match the impedance and improve the radiation efficiency.
4. Principle used in Horn antenna is Huygens principle.
a) True
b) False
Explanation: Horn antenna uses Huygens principle where aperture field is considered as a second source which gives rise to far field. It states that each point on a primary wave front can be considered to be a new source of a secondary spherical wave and that a secondary wave front can be constructed as the envelop of these secondary spherical waves.
5. Which of the following doesn’t apt for flaring?
a) Improve Gain
b) Impedance matching
c) Decreases side lobes
d) Improve Standing waves
Explanation: Flaring is done to provide the impedance matching. So, the reflections are minimized so there will be no standing waves. Side lobes will be reduced so the forward gain is also improved.
6. The radiation pattern of H-plane Sectoral horn is narrower than the E-plane Sectoral horn.
a) True
b) False
Explanation: The radiation pattern of H-plane Sectoral horn is narrower than the E-plane Sectoral horn. It is because of the dimension of the horn antenna in that direction.
7. The small the flare angle, ___ is the directivity and ____ is the beam width.
a) high, low
b) low, high
c) low, low
d) high, high
Explanation: The smaller flare angle means the beam is narrower. The Beamwidth and directivity are inversely proportional to each other. If beamwidth increases then directivity will decrease. So, for a small fare angle, the directivity is more and beamwidth is less.
8. For a horn antenna, in which flaring is done only in one direction is ________
a) Conical antenna
b) Sectoral antenna
c) Pyramidal horn antenna
d) Exponential horn antenna
Explanation: In Sectoral horn antenna, flaring is done only in one direction. Depending on the flaring direction with respect to field propagation, it is divided into E-plane or H-plane horn antenna. Conical horn flared cross section is in shape of a cone.Pyramidal horn flared cross section is in shape of a four-sided pyramid. In exponential horn, the separation of sides increases as a function of length.
9. If flaring is done in the boarder direction of the rectangular waveguide then it is called ______
a) E-plane horn
b) H-plane horn
c) Conical horn
d) Pyramidal horn
Explanation: If the flaring is done in the electric field that means in the boarder direction of the rectangular waveguide, then it is called E-plane horn antenna.
10. If flaring is done in the magnetic field direction of the rectangular waveguide then it is called ______
a) E-plane horn
b) H-plane horn
c) Conical horn
d) Pyramidal horn
Explanation: In Sectorial horn antenna, flaring is done only in one direction.If the flaring is done in the magnetic field direction, then it is called H-plane horn antenna.