Fast factorised backprojection algorithm in elliptical polar coordinate for one‐stationary bistatic very high frequency/ultrahigh frequency ultra‐wideband synthetic aperture radar with arbitrary motion

Abstract

The precise disposal of azimuth variance of range cell migrations and motion errors in the one-stationary bistatic very high frequency/ultrahigh frequency ultra-wideband synthetic aperture radar imaging is a real challenge for efficient frequencydomain algorithms, but can be precisely managed by time-domain approaches. In this study, a novel bistatic fast factorised backprojection (BFFBP) algorithm is presented, which can deal with these two effects accurately and achieve the computational performance in parity with frequency-domain algorithms. First, the imaging geometry with arbitrary motion in elliptical polar coordinate is provided, and the analytical expression of the bistatic backprojection algorithm in this coordinate system is derived, which provides a theory basis for the proposed algorithm. Then, based on the subaperture imaging geometry, the sampling requirements considering motion errors is deduced, which offers the optimal tradeoff between the imaging quality and computational speed. The advantage of using elliptical polar coordinate system for implementing the BFFBP algorithm is analysed. Finally, the implementation and computational burden of the BFFBP algorithm are discussed. Simulation results are shown to prove the correctness of the theory analysis and validity of the proposed approach.

Efficient Time-Domain Imaging Processing for One-Stationary Bistatic Forward-Looking SAR Including Motion Errors

“…Similar to the ETDA for the BSSAR imaging processing in [46,47], the proposed ETDA is able to accommodate the non-ideal track of the moving radar (i.e., compensating the motion error of the moving radar), but does not increase the computational load. In the first processing stage, the motion error can be accurately compensated in the subaperture imaging using the bistatic ETDA.…”

“…These ETDAs are based on the subaperture processing techniques, which can keep all the advantages of the DTDA but with a reduced computational load. With the rapid development of the BSAR technologies in recent years, the monostatic ETDAs have been extended to the BSAR imaging processing, which are classified into two kinds: the bistatic FBPA [37,38,39,40,41,42] and bistatic FFBPA [43,44,45,46,47,48]. A study on the ability of the bistatic FBPA to handle the bistatic range history precisely was developed in [37].…”

“…However, the sampling requirement for the elliptical polar grids was derived not only for the linear track BSAR system, but also for the preferred BSAR case of the radars with the higher angular velocity. Considering the motion errors, the bistatic FFBPA with the derivation of the sampling requirement for the elliptical polar grids was developed in [46,47]. However, for the bistatic FFBPA given in [45,46,47], the elliptical polar range coordinate and polar angular coordinate were only referenced to the transmitter or receiver track, thus the applicability of these sampling requirements was limited in some instances.…”

“…Considering the motion errors, the bistatic FFBPA with the derivation of the sampling requirement for the elliptical polar grids was developed in [46,47]. However, for the bistatic FFBPA given in [45,46,47], the elliptical polar range coordinate and polar angular coordinate were only referenced to the transmitter or receiver track, thus the applicability of these sampling requirements was limited in some instances. The authors of [38] presented a bistatic FFBPA for the linear trajectory BSAR imaging processing in [48], which gave the requirements for splitting the subaperture and subimage, while the sampling requirements of the beams for the corresponding subimages were not given.…”

“…Similarly, the motion errors was not considered in the derivation of the sampling requirements for polar grids, which cannot offer a near-optimum tradeoff between the imaging precision and efficiency in the BSAR imaging processing in practical. It is known that the bistatic ETDA in [37,38,39,40,41,42,43,44,45,46,47,48,49] were developed for the traditional bistatic side-looking SAR (BSSAR) imaging processing. However, to our knowledge, the ETDA for the OS-BFSAR imaging processing has hardly been investigated in earlier publications, thus it may still be desirable for practical OS-BFSAR data processing.…”