Impact of mutual coupling on wideband adcock direction finders

Direction finding (DF) techniques based on a circular array of monopoles or dipoles have the advantage of being able to provide unambiguous direction of arrival (DOA) estimates over 360 degrees. Of the various implementation approaches that are possible, the Adcock direction finder (ADF) is commonly used at UHF and lower frequency ranges. One of the physical constraints is that the diameter of the antenna array must be small compared to the shortestwavelength of interest. However, the close electrical spacing of the antenna elements introduces undesirable electromagnetic coupling between the elements and adversely affects the DOA estimation accuracy. This paper explores the impact of mutual coupling on wideband ADFs based on both amplitude and phase techniques. It is observed that mutual coupling affects the DOA estimates through the reference signal and that these effects can result in substantial DOA errors for both techniques.