Mutual Coupling in the Signal-to-Noise Ratio Optimization of Antenna Arrays

In terms of network parameters defined at the input terminals, expressions applicable to any array configuration are derived for the S/N ratio. The formulation is made in such a way that it becomes possible to account for coupling effects that arise from the geometry of the array and the current distributions on the elements of the array. Since the S/N ratio consists of the ratio of two Hermitians forms, known techniques are used for its optimization. Comparisons with simplified theories are given that demonstrate clearly the importance of mutual coupling in many cases. Numerical results for a 4-element circular array are included for two idealized noise temperature distributions. Applications of this theory to EMC fields are also mentioned.