Performance Analysis of MIMO Links with Non-Isolated Active Antenna Arrays

In this paper, we analyze the performance of non-isolated active arrays in a multiple-input multiple-output (MIMO) system. When ferromagnetic-type isolators are removed in the transmitter (Tx) chains, the antenna mutual coupling will dynamically change the load impedance seen by the power amplifiers (PAs) at their outputs, which subsequently alter their gains/transfer coefficients and eventually introduce interference into the end-to-end link. To study the performance drop caused by PA and antenna array nonlinear interaction, we first mathematically derive the PA dynamic load variation, and the closed-form formulation for signal-to-interference and noise ratio (SINR) is then presented. By comparing with the conventional ideally isolated systems, the throughput simulations reveal the impact of array coupling and PA loadpulling effect on end-to-end link performance.