DC offset and low frequency noise compensation for direct-conversion receiver in pulse compression radar

Abstract

In this paper, we replace low-pass filter (LPF) in traditional direct-conversion receiver (DCR) in pulse compression radar (PCR) by pre-defined filter (PDF) to directly filter direct-current offset and low frequency noise. We also accordingly propose an algorithm for compensating the distance range resolution degradation caused by PDF's effect on low frequency components of received linear frequency modulation (LFM) signals. Based on the theoretical understanding on how the low frequency band influences the pulse compression, a set of newly deduced equations are used to calculate the compression, and the range resolution degradation can be recovered based on the priori knowledge of the employed LFM signal and filters. This method can be used in all pulse compression radars where pre-defined continuous radar signals are employed.

Detrending Technique for Denoising in CW Radar

“…In this case, it is difficult to estimate the variation in the arc length in general. The phenomenon shown in Figure 1 b is generated not only by the short length difference between the wavelength of the operating frequency and the desired displacement of the target but also by the characteristic change in the radar components due to heat generation and the ambient vibration in the very low frequency band [ 27 , 29 ]. In particular, the detection accuracy of the vital sign detection using the CW/FSK radar can be lowered by the DC drift generated by undesired movement of the subject in the radar sensor.…”

“…This assumption can be accepted in general for an I/Q imbalance caused by hardware imperfections but not for a DC offset generated by clutters in the surroundings and device characteristics in the radar [ 24 , 25 , 26 ]. In particular, changes in the characteristics of components due to heat generation, vibrations at a very low frequency, and unintentional movements of a subject with limited movement can generate the so-called DC drift phenomenon, which is the slow movement of the DC offset [ 27 , 28 ]. DC drift lowers the phase-detection accuracy in CW/FSK radars because it makes it difficult for the DC offset to be removed in the circle fitting method [ 29 ].…”