Adaptive Multifunction Filter for Radar Signal Processing

Filtering of radar signals frequently takes place to realize a certain task, such as interference reduction or Doppler processing to remove clutter. However, in this paper a digital filter is proposed to be designed as a multifunction processor, achieving several sorts of signal processing within the same module. Processing is easily done in the baseband rather than in passband, for a moderately slow DSP processor. Hence, a low-pass filter will perform the task of rejection of the out-of-band interference. Higher SNR can be obtained to enhance the detection of targets inside noise if that filter is matched to the expected radar signal, even if it caused signal distortion. Doppler processing makes use of digital filters to cancel signals from fixed and slow targets. The proposed filter would be designed as an adaptive filter to follow interference and clutter changes, and eliminate blindness to some moving radar targets that arise in digital Doppler processing due to aliasing caused by targets of higher speeds. Matlab simulations are made to validate the idea and observe features and limitations of the proposed adaptive filter. Adaptive filter that is based on the least-mean-square algorithm is designed to achieve the best outcome.