Nonlinear effects in solidly-mounted ZnO BAW resonators

The mechanical nonlinearity due to high power level in zinc oxide thin film bulk acoustic wave resonators has been studied in this work. The nonlinear behavior of these resonators was investigated using transmission response measurements. The resonator was decoupled from the 50 Ohm line impedance by 20 pF shunting capacitors in order to allow the excitation of high mechanical vibration levels at the series resonance frequency. The power levels ranged from +5 dBm to +29 dBm at the resonator input. At low excitation power (+5 dBm) the measured series and parallel resonance frequencies of the studied device were 941 MHz and 969 MHz, respectively. When increasing the excitation power level the transmission response exhibits a Duffing-behavior with tilting direction towards lower frequencies. The transmission shows a two-valued response starting at +15 dBm.