Resonant Impedance Tuners: Theory, Design, Power Handling, and Repeatability

Abstract

The theory of coupled-resonator-based impedance tuners is presented for the first time, establishing coverage limitations for two-and three-resonator designs. Besides the advantages of resonant impedance tuners, practical considerations including resonator loss and limited tuning range are included in the analysis. From this theoretical background, a rigorous design procedure is presented for creating optimal resonant impedance tuners, designed for maximum Smith chart coverage, for both the two-and three-pole structures. A proof-of-concept threepole impedance tuner is created following this procedure. This state-of-the-art tuner achieves at least 90% Smith chart coverage from 4 to 8 GHz while maintaining minimum transducer losses of 0.4 dB. The designed tuner is implemented on printed circuit board (PCB) technology and uses electronically controllable linear actuators for tuning. With these design choices, a repeatability of 48 dB is achieved, while maintaining tuning times of less than 100 ms, and is capable of operating at 100 W. This represents performance competitive with the highest repeatability tuners available today. Moreover, it simultaneously achieves 10× faster response time and >10× smaller footprint than state-of-the-art highly repeatable tuners.