Training-based joint channel and antenna impedance estimation

We consider joint channel and antenna impedance estimation based on training data for single-input, single-output channels. The aim is to leverage the resources available in wireless systems for channel estimation to estimate antenna impedance as well. We assume the transmitter sends a known training sequence, during which the receiver varies its impedance in a known way. Based on this observation, we derive maximum-likelihood estimators for the channel and impedance. We show these estimators generally exhibit heavy tails, and explore estimator performance through numerical examples. Our results suggest that antenna impedance can be accurately estimated, in exchange for a small, controlled increase in channel estimation error.