Study On Dimension——Reduced Space ——Time Adaptive Signal Processing Approaches For Airborne Early Warning Radars

As one of tire key technology of the coming generation airborne early warning (AEW) radars with high l)erforlnaflce, st)ace-tiIne adaptive processing (STAP) is being an important study problem in the field of radar signal processing. This dissertation discusses the engineering-realizable dimension-reduced STAP technique under home present conditions for AEW radars working in 14 band and medium pulse repetition frequency (MPRF) mode. Its emphasis is placed on the reduction of the number of spatial channels in STAP.In this dissertation, the fewer and fixed spatial channels are formed by antenna at microwave stage. They are mainly used to cancel the maiiilohe clutter which covers relatively larger doppler regions and degrades the detection performance seriously. In element domain, adaptive processing at suharrav level may he employed. In beam space, the auxiliary beams should be selected around the niainheatn.Contiguous subarra.ys are simpler to iIUl)lemCIlt than overlapping ones. limit grating lobe effects which occur in the former case may (legra(le the sidelobe clutter suppression performance. in MPRF mode, the sidelobe clutter also occupies relatively larger doppler regions and is not neglectahle. There are a tot of methods to depress intensity of grating lobes, in the case of no weighting or equal weighting within each subarrav, we propose a practical method to group irregular contiguous subarrays. In the case of unequal weighting within each subarray, we found that amplitude tapering should be used before synthesizing either regular or irregular contiguous subarrays. 慒 he dimcnsion-reduced STAP approaches with contiguous suharrays got by aforenwiitioncd methods have fe~vcr l)rol)lenls of grating lobe effects.A set of two梔imensional (2桪) spatial梩emporal channels a.rouII(l target. may be miua,de up of several a(Ija.ceIIt (loI)plCr filters iii cacti of a. few adjacent, Fourier梑ase bea.mmus or the existing simm a fl(l difference beams of A EW radars or soimw other cluster 揵eams? If these 2桪 channels are linear independent, a 2?) slant notch niatclmiiing ~vith the corrcspolI(ling section of clutter spectrum ca.im be adaptively formed itt a smaller 2?D subspace covered by them. However, the dimension-reduced SlAP aj)proaches with ahovementioned 2-D cluster channels minced a stmflicieiit condition to cancel the sidelohc clutter far from the main channel: the sidelobe waveforms of auxiliary channels should be about the same as that of the main channel, and their level should be higher.Among all kinds of errors presenting iuevitablely in actual filtering systems, the clement amplitude and phase errors which are hard to be corrected in advance attenuate the clutter suppression performance of the (himueulsioll-reduce(l STAP approaches more seriously. how to select the additiona.I spatial channels suited to improve the ability to correc errors of those dimension-reduced STAP approaches is discussed preliminarily.