A 2-D Signal Processing Model to Predict the Effect of Mutual Coupling on Array Factor

A semi-analytical method for modeling the effects of electromagnetic mutual coupling in uniform linear array (ULA) of N antennas is proposed. The coupling is described as a two-dimensional (2-D) spatiotemporal transfer function derived from S-parameter measurements. The proposed 2-D transfer function enables prediction of the distortions in array factor due to coupling, and thereby enables the potential design of coupling-compensation algorithms. The method is verified with simulations in the 1.5-2.0-GHz range on both an N=7-element ULA using CST Microwave Studio using 50- Ω terminations and a N=3-element ULA in FEKO but with non-50 Ω impedance obtained from measurements of a CMOS low noise amplifier (LNA). Coupling effect on array factor of delay-sum-type beamformer was examined. The proposed model matches within an error of 4%-12% and 4%-10% with respect to the results from two full-wave electromagnetic simulators CST Microwave Studio and FEKO, respectively, in the frequency range 1.75-2 GHz.