Topic: Electromagnetics
The half-power beam width (HPBW) of an antenna in the two orthogonal planes are 120° and 40° respectively. The directivity of the antenna is approximately equals to
- A. 10 dB
- B. 6.5 dB
- C. 12 dB
- D. 8.5 dB
Answer: D. 8.5 dB
Explanation: HPBW in two orthogonal planes = 120° and 40°.
Directivity = $10\log_{10}(\frac{41253}{120 \times 40})$ (Standard approximation uses 41253 sq. degrees).
Directivity $\approx 8.6$ dB. Nearest option is 8.5 dB.