Krusevac, SnezanaRapajic, PredragKennedy, Rodney2015-12-13August 280780392434http://hdl.handle.net/1885/83937In this paper, we investigate the performance of the multi-antenna communication systems, when antenna elements are closely spaced. We analyze the combined mutual coupling effect on both, signal and thermal noise. We apply the Nyquist's thermal noise theorem to determine the thermal noise in the multi-antenna system and to confirm the partial correlation of thermal noise for antenna spacing lower then one wavelength. Then, we evaluate the thermal noise power behavior for the coupled multi-element antenna system. Simulation results show that the signal-to-noise ratio level is underestimated if the effect of mutual coupling for thermal noise is not accounted for.Keywords: Antennas; Communication systems; Computer simulation; Correlation methods; Nyquist diagrams; Thermal noise; Antenna elements; Multi-antenna communication; Mutual coupling; Partial correlation; Signal to noise ratio200510.1109/ISSPA.2005.15802862015-12-12