A double stub impedance tuner with SiC diode varactors

Design and characterization of a double-stub impedance tuner at 1.4 GHz, based on SiC varactors, fabricated at the Chalmers University, is presented. Preliminary studies are carried out to evaluate the capacitance range required to reach the desired impedance coverage, extending from 15 to 80Ω. Accurate optimization is then completed through RF CAD simulation adopting a reliable nonlinear varactor model. The circuit, that to the authors' knowledge is the first example of a generic tuner based on SiC varactors, represents a good compromise between coverage range and losses, the most important figures of merit of a tuner, that besides will be shown to exhibit very good agreement between measurements and simulations. Tuner performances, layout compactness and simplicity, together with the high voltage that can be handled by SiC varactors make it a viable solution for the tunable output networks required in reconfigurable RF power amplifiers.