Mitigation of correlated non-linearities in digital phased arrays using channel-dependent phase shifts

Abstract

In an active phased array, each Transmitter/Receiver Module (TRM) performs a set of approximately linear functions (e.g., amplification, mixing, etc.) with the resulting signals later combined via beamforming techniques. Since these nearly-linear functions are performed prior to beamforming, it is theoretically possible to improve upon the dynamic range (DR) of each TRM through post-module array integration gain. It has been demonstrated, however, that DR enhancement may be limited by correlated nonlinear distortion (i.e., correlated from module to module). A general technique that ensures nonlinearities do not add constructively from module to module has been proposed recently, and verified experimentally for a special case. Another special case of the general technique has been described analytically, but with no experimental verification. In this paper, we correct a flaw in this analysis, and extend it. Measurements on a thirteen channel digital phased array demonstrate that introducing random phase shifts into an array can substantially mitigate nonlinear distortion, thus improving DR over the array.