Week 7

Question 1

Doppler shift effect on spectrum

Answer 1

Shifts the spectrum to f0+fd

If 2 targets are present and moving at different velocities, they will produce 2 Doppler-shifted signals

Question 2

Can these signals be resolved in the spectrum as coming from separate targets

Answer 2

Doppler resolution is determined by the width of an individual spectral line 1/Td

2 Doppler shifts can be resolved only if they differ by at least 1/Td

If 2 Doppler shifts are too close with respect to spectral line width, they will merge into a single peak in the frequency domain

Question 3

Separation of targets in Doppler domain

Answer 3

Commonly applied to identify moving targets against stronger signal from a stationary background (“clutter”)

Detect target against the background of echoes from stationary clutter with Doppler processing; moving target hugs the ground to try to evade the radar; moving target is revealed by an airborne surveillance radar with Doppler processing

Question 4

What is clutter

Answer 4

Often due to distributed targets, which may be fairly uniform (ground, sea surface) or non-uniform (buildings)