A Systematic Method for the Selection of Feedback Variables in MIMO RF Impedance Matching Systems

An impedance matching between the Radio-Frequency (RF) generator and the equipment is required in order to achieve maximum power transfer or minimum reflection. Different architectures of impedance matching control circuits are utilized in this problem depending on the selection of the tunable elements and topological structure. The matching network may not show expected topology behavior due to unknown elements and parameter drifting. Although there exist suggestions for the selection of feedback variables for various impedance matching control schemes, a comprehensive justification for the feedback variable selection on RF impedance matching is still missing in the literature to our best knowledge. To introduce a systematic approach on the feedback variable selection methodology, a coupling analysis for the MIMO impedance matching problem is introduced using Relative Gain Array (RGA) and interaction index analysis. Two most common matching networks are used for demonstration of the procedure namely L-Type up converting and T-Type considering additional inductor due to additional unknown element in the structure. At the end, a novel interaction coefficient is presented to as a metric for the coupling quantification of impedance matching MIMO problem for 6 candidate feedback variable scenarios. Clearly, one should select feedback variables in the impedance matching control so that the coupling effect is as small as possible. Topology changes due to performance degradation or unknown elements can be monitored with predictive maintenance and health monitoring applications. Hence, the selection of feedback variables can be updated to achieve possible error recovery. Results show that the selection of feedback variables with the aid of proposed systematic methodology enables to achieve higher convergence rate within feasible load impedance region.