Digital Beamforming and Adaptive Processing
Modern ESAs present the opportunity to do digital processing on the outputs of multiple subarrays without having to digitally sample the output of each element, thereby greatly simplifying the design of the ESA while still achieving the benefits of adaptive processing. The principles behind two common techniques, minimum variance distortionless response (MVDR) and space-time adaptive processing (STAP), are described, and it is shown that under idealized conditions MVDR and STAP perform identically. An example of jammer nulling is discussed in detail when the interfering signal(s) is within the main beam of the ESA but outside of the full width at half maximum (FWHM) beamwidth. It is shown also that MVDR works better in this case when the jammers are distributed symmetrically about the desired signal, something that can be achieved in MVDR by simply modifying the subarray to subarray covariance matrix of the interference used to compute subarray weights.
KeywordsElectronically scanned array (ESA) Digital beamforming Adaptive processing Carrier-to-noise power spectral density Minimum variance distortionless response (MVDR) Space-time adaptive processing (STAP) MVDR and STAP equivalence
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