Question

Power density from an isotropic antenna is equal to ________

(a) \(\frac{P_t}{4 \pi R^2}\)

(b) \(\frac{P_c}{4 \pi R^2}\)

(c) \(\frac{P_t}{2 \pi R^2}\)

(d) \(\frac{P_t}{4 \pi R}\)

I have been asked this question during an interview.

The question is from Envelope Detector topic in section Amplitude Modulation of Analog Communications

Answer 1

Right option is (a) \(\frac{P_t}{4 \pi R^2}\)

For explanation: Power of a transmitter that is radiated from an isotropic antenna will have a uniform power density in all direction. An isotropic antenna is an ideal antenna that radiates its power uniformly in all directions. There is no actual physical isotropic antenna. However, an isotropic antenna is often used as a reference antenna for the antenna gain. The power density at any distance ‘R’ for an isotropic antenna is equal to \(\frac{P_t}{4 \pi R^2}\).