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RFI Suppression Based on Azimuth Frequency Domain Notch for Low Frequency UWB SAR

The low frequency ultra-wideband synthetic aperture radar (LF UWB SAR) is widely used in military and civil areas, because of its high-resolution imaging and strong penetration ability. Because the operation frequency of LF UWB SAR is in the same frequency band as radio, television and mobile communication signals, these radio frequency interference (RFI) signals are inevitably received by LF UWB SAR. RFI signals and target echo signals are mixed together, resulting in lines or noise in the imaging results, therefore seriously affect the detection ability and imaging quality of the LF UWB SAR. Although the traditional notch method is widely used in RFI suppression, its RFI suppression effect is poor. Moreover, the traditional notch method is only suitable for the suppression of narrowband RFI signals, but when the wideband RFI signal exists, the effect of RFI suppression is quite poor. But in practice, wideband RFI signal and narrowband RFI signal exist at the same time, so it is difficult to obtain ideal RFI suppression effect by using the traditional notch method. Based on the traditional notch method, an RFI suppression method based on azimuth frequency domain notch is proposed in this paper. Not only the proposed method can suppress narrowband RFI signal, but also it can obtain the great RFI suppression effect when there exists the wideband RFI signal. Experimental results show that the proposed RFI suppression method based on azimuth frequency domain notch has better RFI suppression effect than the traditional notch method when narrowband RFI signal and wideband RFI signal exist at the same time.