Sample phase aspects of FM pulse compression waveforms

By utilizing a long low-power pulse, pulse compression waveforms allow systems to improve sensitivity without sacrificing range resolution. Matched filters are traditionally used for pulse compression, but range sidelobe responses are too high to adequately measure weak weather echoes near strong targets such as aircraft, ground clutter and heavy weather. Least-squares sidelobe suppression filters have superior characteristics for hard targets, but have not been well tested for weather radars. When these filters are applied to FM waveforms, the sampled phase of the target rarely matches the sampled phase from which the filter was defined. This causes the sidelobes to rise steeply. In this paper the authors propose a technique to minimize sidelobes over arbitrary sampling phase by integrating the effects of all sample phase shifts into the minimizing equations. Comparing this technique with simply oversampling shows that oversampling generally yields lower expected integrated sidelobes.