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The limitations of current mutual coupling compensation methods in antenna arrays are thoroughly reviewed. The theory of mutual coupling compensation is unified in such a way that efficient methods can be employed for calibrating both transmit and receive systems having arbitrary geometries. The theory leads to methods that can evaluate mutual coupling using either theoretical or experimental means. Reciprocity is studied through the careful comparison of receive and transmit analytical formulations. Examples involving various applications are presented for the validation of the theory. This theory has numerous applications and contributes to the areas of antenna theory, mutual coupling analysis, complex structure modeling, and antenna measurements.

Abstract-Practical antenna array designs generally require that the elements are separated by electrically short distances. The resultant mutual coupling often adversely affects the achievable performance. Various methods are available to quantify the effects of mutual coupling in arrays and improve performance through mutual coupling compensation. Mutual coupling is often described by a coupling matrix that relates the coupled and uncoupled quantities. Unfortunately, the accuracy with which the coupling matrix can be calculated is highly dependent on both the method selected and the frequency. This is a significant limitation for wideband analysis where the coupling matrix needs to be calculated accurately at all frequencies of interest. This paper introduces a novel method for the precise calculation of the coupling matrix at any frequency of interest. It is an extension of the induced EMF method to multiple array elements. The method has the important practical advantage of being independent of the numerical technique used in the analysis. Since the coupling matrix is calculated by exciting the elements in the transmission mode, the method resembles well-known network analysis. However, as outlined in the paper, there are subtle differences between the two approaches, which lead to more accurate results with the new proposed method. It is also demonstrated that antennas with arbitrary geometries and illuminations are handled accurately by the method.Corresponding author: S. Henault (henault@rmc.ca). 104Henault et al.

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 shortest wavelength 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.