Biologically inspired coupled antenna array for direction of arrival estimation

We propose to design a small-size antenna array having high direction of arrival (DOA) estimation performance, inspired by the Ormia ochracea's coupled ears. The female Ormia is able to locate male crickets' call accurately, for reproduction purposes, despite the small distance between its ears compared with the incoming wavelength. This phenomenon has been explained by the mechanical coupling between the Ormia's ears, modeled by a pair of differential equations. In this paper, we first solve the differential equations governing the Ormia ochracea's ear response, and convert the response to the pre-specified radio frequencies. Using the converted response, we then implement the biologically inspired coupling as a multi-input multi-output filter on a uniform linear antenna array output. We derive the maximum likelihood estimates of source DOAs, and compute the corresponding Cramér-Rao bound on the DOA estimation error as a performance measure. We use Monte Carlo numerical examples to demonstrate the advantages of the coupling effect.