Eclipsing effects with high-duty-factor waveforms in long-range radar

The partial eclipsing of returns in long-range radar with a high-duty-factor waveform is considered, and two eclipsing zones are shown to exist. The effects on clutter levels, by virtue of increased range sidelobes, and on signal/noise ratio, pulsewidth and pulse amplitude are examined. It is shown that the enhancement of range sidelobes caused by eclipsing, and the associated clutter effects, do not extend outside the eclipsing zones. It is further shown that, for a phased array radar, it is feasible to envisage working well within the first eclipsing zone, which extends to the range equivalent of the transmitted pulse length, and that the instrumented range can be usefully extended beyond the range which corresponds to the resumption of transmission. The use of auxiliary compression filters matched to eclipsed returns as a means of restoring low-range sidelobes is considered.