Clutter mitigation in weather radar systems filter design & analysis

One of the factors limiting the performance of weather radar systems is the presence of "clutter" in the received signal. Clutter is the group of signal components caused by reflections from objects other than weather targets; it is undesirable because it can obscure meteorologically interesting signals from actual weather targets. Objects that cause clutter are usually stationary, so the signal components with zero and near-zero Doppler shifts are usually clutter. Most weather radar systems use digital high-pass filters to reduce clutter by severely attenuating the zero and near-zero frequency components of the received signal. An alternative and relatively new technique for reducing clutter is frequency-domain filtering, where the Doppler velocity spectrum of the received signal is calculated and manually altered below a certain velocity. The frequency-domain filter performs the same task as the high-pass digital filter but never removes too much of the signal, as the digital filter sometimes does, because an appropriate cutoff frequency is calculated for each spectrum. The performance of a frequency-domain filter is compared with a digital high-pass clutter filter, and the frequency-domain filter is shown to remove more clutter from the radar signal.