Topic: Electromagnetics
For a directional coupler, if $P_{i}=$ Incident Power, $P_{o}=$ Output power, $P_{f}=$ Forward coupled power and $P_{r}=$ Reverse coupled power; then, Directivity of directional coupler is
- A. $P_{f}/P_{r}$
- B. $P_{r}/P_{o}$
- C. $P_{o}/P_{f}$
- D. $P_{i}/P_{f}$
Answer: A. $P_{f}/P_{r}$
Explanation: The directivity of a directional coupler is a measure of how well the coupler isolates the forward and reverse signals. It is defined as the ratio of the forward coupled power ($P_f$) to the reverse coupled power ($P_r$) at the coupled port, typically expressed in dB as $10 \log_{10}(P_f/P_r)$.