Design of dual-mode resonators based on laterally coupled alternating thickness (LCAT) modes for WiFi 2.4G and n77 dual-passband filter

Abstract

This paper explores a dual-mode resonator that uses laterally coupled alternating thickness (LCAT) modes, and a dual-passband filter for WiFi 2.4G and n77 bands is constructed. The resonator's frequency can be adjusted by the electrode thickness, period and piezoelectric film thickness, and their effects on the quality factor (Q) values and effective electromechanical coupling coefficient (k2eff) were analyzed. In addition, the impact of Sc-doped concentration on resonators' performance was investigated, and the AlSc0.35N-based resonators exhibited both high Q and k2eff values. Furthermore, two resonant modes were effectively excited by setting two working regions. Adding an acoustic blocking groove reduces mutual acoustic energy leakage, increasing Q values for target modes and suppressing spurious signals. The dual-mode resonator’ structure were further optimized to ensure that both modes have similar high performance. Ultimately, this work constructs a dual passband filter with center frequencies of 2.49 and 3.54 GHz with 75 and 132 MHz bandwidths respectively, and achieves over 60 dB out-of-band rejection.