Question

What is the number of beams that a Doppler radar uses?

(a) 4

(b) 2

(c) 1

(d) 3

This question was addressed to me in an interview for job.

My query is from Doppler Radar in chapter Celestial Navigation, Doppler and Altimeter Radars of Avionics

Answer 1

The correct option is (a) 4

The explanation is: Although only three beams are required to provide the three components of velocity, most modern Doppler radars employ four beams, because of the planar array antennas generally four such beams. The fourth beam shift can be combined with that of the third to obtain a more accurate component of velocity.