New SAR Algorithm for Sidelobe Reduction in Range direction

Abstract

Sidelobes degrade radar performance by placing energy up and down range from its source. Range sidelobes associated with a large radar cross section (RCS) target may mask the presence of a smaller target located within a pulse width of the larger target; thus, "low" sidelobes are a desirable property. All the synthetic aperture radar (SAR) Sidelobe reduction algorithms which using matched filtering (windowing) like hamming window reduce the sidelobes on the expense of degrading the resolution. Our proposed algorithm using an optimum filter is reduced the sidelobes in range direction while keeping range resolution. In this paper, drive the formula for filter that reduce the sidelobe after linear frequency modulation matched filter then check the ambiguity function for proposed filter. Finally applied simulated and real raw data of SAR to proposal algorithm for SAR image formation and range Doppler algorithm and measure the quality of focused image.

Enhanced range-doppler algorithm for SAR image formation

“…RDA was presented in 1978 as an algorithm that efficiently utilizes Fast Fourier Transforms (FFT) to condense the azimuth and range direction of the unfocused raw SAR data [6]. It is the most widely utilized SAR processing technique [10], in addition, it consistently and effectively accounts for range-varying features including range cell migration, azimuth frequency modulation rate, and doppler centroid [4], as seen in figure 2.…”

“…It begins with a fast convolution that compresses the range of the data, followed by the multiplication of the raw data in the frequency domain with a range reference function [10]. This results in calculating the range FFT, multiplication with a matched filter, and applying the range inverse FFT [6]. An azimuth FFT is employed to transform the data into the Range-Doppler domain.…”

“…An approach that is widely used to address this high PSLR issue is using window functions, such as Taylor, Hamming, Kaiser, and Hann, Blackman windows at the reception side with different trade-offs [5]. Window functions may, however, widen the main lobe and reduce the SNR when applied to matched filter at the receiving side, which negatively impacts SAR image resolution [6]. Therefore, from the perspective of optimization, it makes sense to construct a mismatched filter.…”

“…This paper presents a modified version of RDA that utilizes an optimized mismatched filter to lower side lobe levels without the need for additional weighting or windowing functions [6]. The method is based on addressing the PSLR optimization problem as an identical QCQP [9].…”

Design and Implementation of an Enhanced Matched Filter for Sidelobe Reduction of Pulsed Linear Frequency Modulation Radar

“…In the inverse filter technique for the LFM waveform, implemented in [ 47 ], the sidelobe reduction is performed for the case of a zero-centered frequency LFM, where only the peak value of the mainlobe will pass. This technique was then applied in [ 48 ] for synthetic aperture radar (SAR) processing in range direction. Additionally, sidelobe reduction Barker–LFM was utilized in [ 49 ].…”