Passive High Power RF Comb Filters Using Epitaxial GaN/NbN/SiC HBARs

This report presents the first demonstration of passive RF comb filters made using epitaxial GaN/NbN/SiC high overtone bulk acoustic resonators (epi-HBARs). The two-port device is fabricated on electronic-gradeGaN, electrically transduced, and acoustically coupled. The multimode epi-HBAR comb filter demonstrated here has 158 sharp filter passbands periodically distributed between 1 and 4 GHz, f x Q (L-S-bands) with a free spectral range (FSR) of 17 MHz. The individual passbands of the epi-HBAR comb filter demonstrate transmission bandwidths (BWs) up to 800 kHz, fxQ values of up to 7 x 1014 Hz, and an average k(eff)(2) Q figure of merit of 41.2 at room temperature. The GaN/NbN/SiC epi-HBAR comb filter is capable of operating at high RF power levels, with linear and distortion-free performance seen up to at least 1 W of continuous wave (CW) power and up to at least 10 W of pulsed power. The compact epi-HBAR comb filters can be co-fabricated with GaN-based electronics and could potentially replace larger, off-chip or discrete-component comb filters. They can be used for spectrumsensing and as signal processing elements for remote sensing and pulsed radar.

Automated summary

This report demonstrates the first passive RF comb filters made using epi-HBAR technology, with multiple sharp filter passbands suitable for high-power RF operation, and potential to replace larger off-chip or discrete-component comb filters.