High-frequency thin-film piezoelectric transformers

Abstract

A voltage step-up/impedance transformer is presented which operates by modifying the electrode configuration of lateral-extensional mode thin-film piezoelectric-on-substrate (TPoS) resonators. The individual electrode pairs that cover the stress concentration areas of a 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup> order harmonic 30MHz resonator are connected in series at the output port to effectively unbalance the input and output impedances. After inductive cancellation of the electrode/pad capacitances at the output port, a voltage gain of +10.4 dB is achieved in such transformers. Additionally, an impedance transformation ratio of 19:1 is obtained.