Sub-6 GHz acoustic filters using laterally-excited bulk acoustic resonator with scattering vias in double-layer...

The suppression of in-band ripple and enhancement of power-handling capability (PHC) represent critical research imperatives for next-generation super-high-frequency (SHF) wideband filters. This study presents a laterally-excited bulk acoustic resonator with scattering vias in double-layer electrodes (SV-BAR) and its filter for sub-6G SHF wideband applications, to simultaneously suppress spurious modes by curved scattering boundaries and enhance PHC by gold-filled double-layer electrodes. Fabricated on a 358 nm Z-cut LiNbO₃-on-insulator (LNOI) substrate using a four-mask ion beam etching process, the SV-BAR achieves a K_t² of 24.1%, a Bode_Q_max of 366 at 5.946 GHz, as well as a remarkable product of merit (PoM, f·Bode_Q_max·K_t²) of 5.24 × 10¹¹Hz. In addition, the compact 2.5-order mirror ladder filter (1.949 mm² footprint) exhibits a center frequency of 5.8585 GHz, a 9.71% fractional bandwidth (569 MHz), 23.97 dB out-of-band rejection, and a temperature coefficient of frequency (TCF) of -64.04 ppm/°C. Notably, it demonstrates exceptional PHC of +30.88 dBm at 6.162 GHz (1-dB compression point), attributed to its mechanical stability, low ohmic loss, and thermal stability (3-dB lower cutoff TCF_l = -84.11 ppm/°C vs. upper cutoff TCF_h = -45.83 ppm/°C). This breakthrough enables ultra-wideband, miniaturized filters in next-generation wireless systems.