TABLE OF CONTENTS 
Ground return falls into three categories: mainlobe return, sidelobe return, and altitude return, which is sidelobe return received from directly beneath the radar. Mainlobe return is signal for many applications ground mapping, altimetry doppler navigation, etc. But both mainlobe and sidelobe return are clutter for radars which must detect airborne targets or moving targets on the ground (Fig. 1).
The principal means of discerning target echoes from ground clutter is doppler resolution. In ground based applications, separating targets from clutter is straightforward. Since the radar is stationary, all of the clutter has essentially one doppler frequency zero. In airborne applications, however, this is far from true. Consequently, the way in which the clutter is distributed over the band of possible frequencies its doppler spectrum and the relationship of this spectrum to the doppler frequencies of anticipated targets critically influence a radar's design.
In this chapter, we'll consider what determines the amplitude of the ground return. We will then examine the doppler spectrum of each of the three categories of ground return, and the relationship of the composite spectrum to the doppler frequencies of target aircraft in representative situations. Finally, we'll consider the problem of exceptionally strong sidelobe return reflected by certain objects on the ground.
For simplicity, we will assume that the radar is transmitting...
