Continuously tunable impedance matching network using ferroelectric varactors

A prototype of an electronically tunable impedance matching network in "T "-configuration at 1.95 GHz has been realized with discrete ferroelectric varactors of Barium-Strontium-Titanate Ba_0.6 Sr_0.4TiO₃ (BST). The tunable load impedance range has been analyzed in dependency of tuning voltage. For a 50 Ω load and source impedance, the measured insertion loss is 1.15 dB. The high power handling capability of the varactors has been experimentally verified. A nonlinear varactor model was implemented to simulate the large-signal circuit behavior. Two-tone measurements on the network show an output IP₃ of 46.5 dBm at 26 dBm average input power and 52.8 dBm at 33 dBm average input power.