A Hybrid Approach to Joint Estimation of MIMO Channel and Antenna Impedance Matrices

Abstract

Antenna impedance matching significantly affects the channel capacity of compact MIMO receivers. When antenna impedance is known to the receiver, channel capacity can be optimized. However, channel capacity may diminish, when antenna impedance varies due to time-varying near-field loading. This motivates impedance estimation in real-time. In this paper, we derive joint MAP/ML estimators for channel and impedance matrices in closed-form. As one result, we develop a design principle leveraging a trade-off between channel and impedance estimation, which depends on transmit diversity.