Antennas Questions and Answers – Half Power Beam Width

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This set of Antennas Quiz focuses on “Half Power Beam Width”.

1. Beam area and directivity are related as _____
a) \(D=\frac{2\pi}{B}\)
b) \(D=\frac{4\pi}{B}\)
c) \(D=\frac{B}{2\pi}\)
d) \(D=\frac{B}{4\pi}\)
View Answer

Answer: b
Explanation: Beam width/ beam area is the measure of directivity of an antenna.
\(D=\frac{4\pi}{B}\)
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2. What is the Beam area in radians when the HPBW in perpendicular planes are given by 60°, 30°?
a) \(\frac{\pi^2}{8}\)
b) \(\frac{\pi}{2}\)
c) \(\frac{\pi^2}{18}\)
d) 2
View Answer

Answer: c
Explanation: Beam area B=θE θH=60°×30°=\(\frac{\pi}{3}×\frac{\pi}{6}=\frac{\pi^2}{18}\)

3. Beam width is the measure of directivity of antenna in terms of angles either radians or degrees.
a) True
b) False
View Answer

Answer: a
Explanation: Beam width is defined as the measure of angular width at two points on the major lobe where the power decreases to half of the maximum radiated power. So beam width is the measure of directivity of antenna.
\(D=\frac{4\pi}{B}\)
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4. Find the directivity when the half power beam widths are 45° and 60° in perpendicular planes.
a) 12.58
b) 17.98
c) 22.91
d) 15.28
View Answer

Answer: d
Explanation: Directivity in terms of HPBW (in degrees) is given by \(D=\frac{41257}{θ_E θ_H} =\frac{41257}{45° × 60°}=15.28\)

5. What happens to the beam-width of antenna if the frequency of operation is increased?
a) Beam-width will decrease
b) Beam-width will increase
c) Beam-width is independent of frequency
d) Beam width may increase or decrease
View Answer

Answer: a
Explanation: If frequency is high, power radiated is low (From Radar range equation). That means directivity is high as \(D=\frac{4\pi U}{P_{rad}}.\) Beam width and directivity are inversely proportional to each other. So beam width will be low.
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6. Half-power beam width is also called as 6-db beam width.
a) True
b) False
View Answer

Answer: b
Explanation: Half-power beam width is also called as 3-db beam width. It the angular width calculated between the points when the power drops to half of the maximum power radiated.

Sanfoundry Global Education & Learning Series – Antennas.

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Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer & SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage, Advanced C Programming, SAN Storage Technologies, SCSI Internals & Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him @ LinkedIn | Youtube | Instagram | Facebook | Twitter