Beat frequency filter for removing harmonic signals on linear FM-CW radar

Abstract

This paper, a research on filter for removing the harmonic signals that interfere with the beat frequency at the radar receiver is presented. These interfering signals, which have levels above the noise level, may affect significantly the radar detection performance. False detections may arise due to these harmonic signals. For a detection range of 10 Km, the beat frequency is 66.67 kHz. The signal at the frequency of 66.67 kHz will have a higher magnitude than the signals with different frequencies. In addition to this beat frequency component, the three exists high frequency components with frequency about 1000 -1200 kHz. These high frequencies make the beat frequency hard to retrieve when the radar target ranges farther and closer to the unambiguous range of the system. Thus, a steep low pass filter is required to remove these interfering frequencies. A Chebyshev low pass digital filter is design and implemented to perform this task. The stop band attenuation at the cut off frequency of 900 kHz was achieved at about 80 dB.