N, t) with the i-th channel within the range constant, and envelop the azimuth multichannel impulse response Ssmul,i ( f r , terms, the azimuthfrequency azimuth time domain is rewritten as ( f r , t ) of your i-th channel within the multichannel impulse response Ss mul,i follows:(a) variety frequency azimuth time (domain is rewritten as follows: 2 f + f ) (b)Neglecting the unimportant range frequency modulation, constant, and envelop terms,azimuth multichannel 2 ( f + f ) reconstruction is mainly operated in the 2D frequency domain, the r c Ss mul,i ( range-variant phase errormul, reconstruction, when the second Doppler t ) exp – R also residual f r ,azimuth jmultichanneli ( t )wants to be compensated in the rangeone The very first phase term is for c must be removeddomain. The flowchart of the proposed azimuth multichannel reconstruction TD139 supplier approach is ahead of reconstruction, which can be implemented inside the 2D time do- (20) which rincludes steps xi azimuth 2 ( r + f ) shown in Figure 11, two ( f + f ) of time-varying fphase removing, 2D = exp – j time Paliroden site offsets txi two + in distinctive Ri ( t main. Moreover, various azimuth azimuth cmultichannelvreconstructioninjazimuthc channels Rs – s Rcost.i exp – the 2D frequency)domain, spectrum de-skewing, c c 2vs range-variant de-skewing operation in every single azimuth channel. As the azmust be deemed through the reconstruction phase error compensation, and 2D spectrum re-skewing. The first phase term is for azimuth multichannel 2D frequency domain, the imuth multichannel reconstruction is mainly operated in thereconstruction, though the second a single really should be removed also reconstruction, which is often implemented in Doppler residual range-variant phase error beforeneeds to become compensated inside the rangethe 2D time domain. Moreover, distinct azimuth time offsets xi 2vs in distinct azimuth channels(20) 2 ( + 2 frequency r) fc ) Rs t de-skewing. =2D ( – j+ f cfspectrum following xi + Rcos t.i exp – j two ( fr + fc ) Ri (t) (b) exp f r – 2vs c R c Ss mul,i ( f r , t ) exp – j mul, i ( t ) c The initial phase term is for azimuth multichannel reconstruction, when the second Neglecting the unimportant variety frequency modulation, constant, and(20) envelop 1 2 f + fremoved ahead of must be terms, ther azimuth multichannel impulse whichSs (berrimplemented channel within the ,+ f cof the -th in the 2D time response can two xi ) ( In addition,distinctive reconstruction, x mul,i (ff int )differentiazimuth channels ) c azimuth time exp – j i /2vs = exp domain. -j + Rcost. offsets Ri ( t ) Rs t – range frequency azimuth time domain isi rewritten as follows: c c two the have to be regarded duringvs de-skewing operation in every azimuth channel. As theSsmul,i ( f r , t)c Figure ten.2D frequency spectrum in the squint case. (a) 2D frequency spectrum before de-skewing;exp – jrcRmul,i (t)313 314 315 316318 319domain. The flowchart with the proposed azimuth multichannel reconstruction approach is shown in Figure 11, which involves actions of azimuth time-varying phase removing, 2D spectrum de-skewing, azimuth multichannel reconstruction within the 2D frequency domain, range-variant reconstruction phase error compensation, and 2D spectrum re-skewing.Remote Sens. 2021, 13, 4705 Remote Sens. 2021, 13, x FOR PEER REVIEW13 of 22 14 ofH1,1 ( , t )H1,i ( , t )Range FFTRange FFTH two,1 ( f r , t )H two,i ( f r , t )Azimuth FFTAzimuth FFTP1 ( f r , f a ; Rref )Pi ( f r , f a ; Rref )Variety IFFTRange IFFTP1 ( f r , f a ; R0 )Pi (.