Analysis of clutter cancellation capability considering radar system phase noise effects

Ground clutter returns in an airborne Doppler weather radar will create a very strong spectral power around zero frequency. Without proper clutter cancellation, the spectrum moment estimates will be so seriously biased that they no longer provide the reliable information for windshear detection. It is considered that 10 dB signal-to-clutter ratio (SCR) is needed for accurate mean velocity estimation via pulse pair processor while the spectrum width estimation may require 15 dB SCR. Therefore, it means that at least 10 dB SCR should be achieved by filtering clutter power. Clutter power located around zero frequency can be removed very effectively using a high pass filter which attenuates low frequency powers to the desired level in a stopband region, but the width of stopband should be carefully selected to avoid elimination of low frequency weather signals. Usually clutter spectrum is so narrow that clutter cancellation may be done very successfully without degrading the weather spectrum. However, phase noise in a radar system will broaden the clutter spectrum making some portions of power spill to a pass band region limiting clutter cancellation capability which may be a problem in the case of dry weather situations where the weather signal is much weaker than the clutter return.