SHORT-RANGE SEA CLUTTER IN HORIZON SEARCH RADAR SYSTEMS - ANTENNA PATTERN EFFECTS

Short-range clutter can limit the performance of radar systems using h igh pulse repetition frequency (PRF) waveforms. The paper evaluates th e antenna pattern effects of short-range sea clutter for an example ho rizon search system. Clutter-to-noise ratio (C/N) and signal-to-noise ratios (S/N) are evaluated for several antenna designs, in which apert ure illumination weighting can be achieved on either transmit or recei ve. Three antenna effects are studied: illumination function (pattern) , elevation of the pattern with respect to horizontal ('upspot'), and aperture diameter. Of several cases examined, one with uniform weighti ng on transmit and Taylor weighting on receive gives the most desirabl e clutter response. With reference to the case of uniform transmit and receive patterns with no upspot, a Taylor receive pattern with -42 dB sidelobe level in combination with an optimal upspot angle reduces wo rst-case clutter by almost-equal-to 14.7 dB at the expense of almost-e qual=to 10.25 dB increase in the transmit power required to equalise S /N to that of the reference. Doubling the aperture diameter further re duces worst-case clutter by almost-equal-to 13.2 dB, with required tra nsmit power actually decreasing (almost-equal-to 12.41 dB) over the pr evious case. Here, the cost is a larger antenna. Antenna consideration s are shown to have a considerable impact on clutter and to be perhaps the best method of reducing radar dynamic range requirements.