A Non-Reciprocal Filter Using Asymmetrically Transduced Micro-Acoustic Resonators

This letter reports a non-reciprocal filter based on the use of nonlinearities in high quality-factor (Q) silicon micro-acoustic resonators with asymmetric piezoelectric transducers. The two-port resonators are created by the integration of 120-nm piezoelectric aluminum nitride and 10-nm ferroelectric hafnium-zirconium-oxide transducers atop of 70-nm single-crystal silicon. The asymmetric electromechanical transduction architecture results in highly contrasted power-handing of the micro-acoustic resonator when excited at different ports, resulting in nonreciprocal transmission response for excitation powers beyond a certain threshold. A proof-of-concept filter at 253 MHz with 0.25% -3-dB bandwidth is implemented through electrical coupling of two asymmetrically transduced resonators with individual Q of ~870. The filter demonstrates a non-reciprocal transmission ratio of 16 dB for input power exceeding 5 dBm.