Incoherent MLE of Array Antennas with Inordinate Spacing Using Subband Hopping Approach

Given a certain transmission frequency, Shannon spatial sampling limit defines an upper bound for the antenna element spacing. Beyond this bound, the exceeded ambiguity avoids correct estimation of the signal parameters (i.e. array manifold crossing). In this selective survey, the problem of simultaneous signal and direction of arrival (DOA) estimation of broadband sources is addressed when the element spacing of a uniform array antenna (ULA) is inordinate. It is illustrated that one can resolve the aliasing ambiguity by utilizing the inherent frequency diversity of the broadband sources. A maximum likelihood estimate (MLE) approach has been developed to estimate the transmitted data signal and the DOA of each source. Through confirmatory simulation, it is shown that the performance gain of the proposed setup is potentially significant, in particular under very low SNR and small separation of the sources. This relaxes the stringent maximum element-spacing constraint of ULAs pertinent to the upper-bound frequency of transmission and suggests that the element spacing - which in practical applications result in detrimental element coupling - can be conveniently increased, in particular under wide transmission spectrum and low SNR (e.g. license free communication). A method similar to the frequency hopping approach (i.e. subband hopping), is utilized for the problem of source associations and identification.