Radar clutter is defined as unwanted echoes, typically from the ground, sea, rain or other precipitation, chaff, birds, insects, and aurora [183]. This chapter covers two bistatic clutter topics: surface clutter, consisting of ground and sea echoes, and chaff.
The bistatic RCS of surface clutter, ? c is a measure, as is the monostatic radar surface clutter cross section, of the energy scattered from a clutter cell area, A c, in the direction of the receiver. The bistatic RCS is defined as ? c = ? B A c, where ? B is the scattering coefficient, or the clutter cross section per unit area of the illuminated surface. The clutter cell area is given for beam- and range-limited cases in Section 5.6. This section considers measured and estimated values of ? B, which vary as a function of the surface composition, frequency, and geometry. Also, in contrast to the monostatic case, little measured data for ? B have been reported [42, 43, 107-115].
The available database for ground and sea clutter at microwave frequencies consists of six measurement programs, which are summarized in Table 9.1. The measurement angles shown in Table 9.1 are defined in Figure 9.1, which is a clutter-centered coordinate System. Because ground and sea are reciprocal media, ? i, and ? s are interchangeable in the subsequent data [103]. The Pidgeon data were analyzed by Dom ville [109] and Nathanson [116].
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