Mutual coupling effect on thermal noise in multi-antenna wireless communication systems

This paper presents a framework for the thermal noise analysis of mutually-coupled antennae in the multi-antenna system. The electromagnetic coupling for thermal noise is included in the analysis of the multi-antenna system with small antenna element spacings. The method for thermal noise power calculation for the multi-antenna system with coupled antennae is presented. The thermal noise behavior in the multi-antenna system is determined by applying the Nyquist's thermal noise theorem. The partial correlation of thermal noise for antenna spacing lower then a wavelength is confirmed. The signal-to-noise ratio (SNR) for the closely spaced antennae in the multi-antenna system is then estimated, using presented method for thermal noise analysis. Simulation results confirm that as the antenna spacing decreases to zero, the multi-antenna system starts to act like a single antenna system.