Clutter suppression using amplitude weighted waveforms

When the range extent of clutter exceeds the PRF interval of a constant amplitude radar pulse-burst (or coherent dwell), standard Doppler filtering using an FIR filter bank with amplitude weighting on receive, no longer provides adequate clutter suppression. A simple solution to this problem is to add fill pulses to each coherent dwell, so that every PRF interval processed by the FIR filter will include clutter from all range ambiguous intervals. For radars needing to operate with a short time-on-target, this approach degrades the performance due to wasted transmitter power and a longer dwell time. The use of amplitude weighting of the transmitted pulse burst to overcome this problem is well known from studies relating to ballistic missile defense radars operating in an environment of range extended debris and chaff. In conventional ground based radar scenarios, clutter is usually present in the same range interval as the target but may also come from longer ambiguous ranges. The maximum range of clutter is usually limited by the radar horizon, but may extend beyond the radar horizon due to non-standard propagation. For such scenarios an amplitude weighting scheme has been proposed where only the leading pulses in the coherent dwell are weighted in amplitude. This paper presents a trade-off between this unilateral weighting approach and the bilateral weighting schemes considered previously.