Abstract
The subaperture processing is one of the essential strategies for low frequency ultrawideband synthetic aperture radar (LF UWB SAR) imaging, especially for the real-time LF UWB SAR imaging because it can improve the parallelization of the imaging algorithm. However, due to the longer synthetic aperture of LF UWB SAR, the traditional subaperture imaging encounters an azimuth ambiguities problem, which severely degrades the focused quality of the imaging results. In this paper, the reason for the presence of azimuth ambiguities in the LF UWB SAR subaperture imaging and its influence on image quality is first analyzed in theory. Then, an extended subaperture imaging method based on the extension of subaperture length before Range Cell Migration Correction (RCMC) was proposed. By lengthening the subaperture length, the azimuth ambiguities are effectively eliminated. Finally, the extended part of subaperture is wiped off before the azimuth compression (AC), and the LF UWB SAR image of high focused quality is obtained. The correctness of the theory analysis and the effectiveness of the proposed method have been validated through simulated and real LF UWB SAR data.
Highlights
The low frequency ultra wideband synthetic aperture radar (LF UWB SAR) has excellent foliageor ground-penetrating capability to detect concealed targets [1,2,3,4]
Based on the previous work, this paper carries out an in-depth theory analysis on this type of azimuth ambiguities, and a novel method was proposed based on the extension of subaperture length before Range Cell Migration Correction (RCMC) processing to suppress the azimuth ambiguities
To eliminate the effect of azimuth ambiguities, an extended subaperture imaging approach based on the extension of the subaperture echo data before RCMC operation is proposed in this paper
Summary
The low frequency ultra wideband synthetic aperture radar (LF UWB SAR) has excellent foliageor ground-penetrating capability to detect concealed targets [1,2,3,4]. The system PRF is higher than the Doppler bandwidth, and the azimuth ambiguities are caused by the under-sampling in the azimuth Doppler domain This type of azimuth ambiguity exists in both full aperture imaging processing and subaperture imaging processing, and it is more severe in the subaperture imaging processing. Based on the above analysis, to suppress the azimuth ambiguities, the azimuth extension of imaging result should be enlarged, which can be done by reducing the sampling interval of Doppler frequency. Based on the previous work, this paper carries out an in-depth theory analysis on this type of azimuth ambiguities, and a novel method was proposed based on the extension of subaperture length before Range Cell Migration Correction (RCMC) processing to suppress the azimuth ambiguities.
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