Principles of Modern Radar - Volume 2 1891121537

10.6 STAP Processing Architectures and Methods 485then forming and applying the adaptive weight vector ˆ˜w k =RD-STAP output is ỹ k = ˆ˜w H k ˜x k.−1 ˆ˜β ˆ˜R k ṽ, with ˆ˜β a scalar. The10.6.1.1 Element Space Post-DopplerPerhaps the most popular RD-STAP method is the extended factored algorithm (EFA)given in [23]. This approach, shown in Figure 10-16a, involves Doppler filtering eachreceive channel and then adaptively combining several adjacent Doppler filters and allspatial channels. For example, three to five Doppler DoFs is common, so the overallspace-time DoFs is 3M to 5M. The adaptive weights are shown in the figure as w m,n ,where m indicates channel number, and n characterizes the relative Doppler bin number(from the three bins of interest); the superscript, *, denotes conjugation; and y EFA,k ( ˜f d ) isthe EFA output for normalized Doppler, ˜f d .Figure 10-16b describes EFA operation in the angle-Doppler domain. The horizontal,rectangular boxes identify various Doppler filters. EFA is able to configure nulls alonga section of the angle-Doppler clutter ridge spanned by the reduced set of Doppler filterChannel 1DopplerProcessorChannel 2DopplerProcessorChannel MDopplerProcessorFIGURE 10-16Extended factoredalgorithmreduced-dimensionSTAP.* * * * * * * * *w 1,1 w 1,2 w 1,3 w 2,1 w 2,2 w 2,3 w M,1 w M,2 w M,3ADDERDopplerFiltersy EFA,k (f˜d )(a) EFA RD-STAP processing approach80065600604005520050045−2004035−40030−60025−80020−90 −60 −30 0 30 60 90Angle (Degrees)(b) Illustration of EFA operation in the angle-Doppler domainDoppler Frequency (Hz)Clutter Power Spectral DensityNullLocationsdB