Correspondence: Mutual coupling compensation for small, circularly symmetric planar antenna arrays

The paper describes a method for compensating for the effects of mutual coupling in small, circularly symmetric planar antenna arrays such as those used as feeds for parabolic relector antennas. This is achieved by breaking down the array excitation into a series of orthogonal circularly symmetric phase modes, as used in the case of circular antenna arrays. The compensation may then be achieved by means of fixed compensating impedance matches at the phase-mode excitation ports. Once applied, the compensation is independent of the subsequent aperture excitation. It is also shown how the scheme can apply to 4-element planar arrays used as a monopulse cluster feed for a parabolic reflector. Although presented as a physical method to compensate for mutual coupling, the concept may also be used to compute the correct array excitation needed to achieve this compensation.