The impact of antenna mutual coupling on signal correlation in multi-antenna receivers has been studied in great detail. By contrast, there has been little work on how mutual coupling affects noise. In this paper we present a noise model for a diversity receiver that includes noise generated by the antennas, front-end amplifiers, and other receiver components. This model shows that noise in a compact diversity receiver may be spatially correlated. Expressions relating noise correlation to properties of the antennas and amplifiers are derived and its impact on the outage probability of an optimal diversity combiner is studied. Examples illustrating the relationship between mutual coupling and noise correlation demonstrate how different noise sources may impact performance in profoundly different ways.

The effect of antenna mutual coupling on fading correlation in compact MIMO arrays has received considerable attention. By contrast, relatively little attention has been paid to the noise. In this paper we present a circuit model for a noisy MIMO receiver front-end that includes arbitrary coupling and noise correlation. The noise figure for two-port networks is extended to multiport networks, from which theorems for optimal front-end design are derived. Numerical results are presented which provide insight into receiver noise behavior in the presence of coupled antennas.

Previous studies of receive diversity have carefully modeled the impact of spatial correlation and antenna coupling on the signal component at the receiver. By contrast, relatively little attention has been paid to noise. In this paper we introduce a receive diversity model that articulates the dominant physical noise sources and relates their spatial correlation to the properties of the antennas, front-end amplifiers and matching networks. We then derive an optimal receiver as well as a formula for the resulting outage probability in terms of these noise sources. Numerical results are presented which suggest that different noise sources can impact performance in profoundly different ways.