Dual-Passband SAW Filter Based on a 32°YX-LN/SiO2/SiC Multilayered Substrate

To meet the demands of highly integrated and miniaturized radio frequency front-end (RFFE) modules, multi-passband filters which support multi-channel compounding come to the foreground. In this work, we proposed a new design of a dual-passband surface acoustic wave (SAW) filter based on a 32 degrees YX-LiNbO3 (LN)/SiO2/SiC multilayered structure. The filter is of a standalone ladder topology and comprises dual-mode resonators, in which the shear horizontal (SH) mode and high-order SH mode are simultaneously excited through electrode thickness modulation. The impact of electrode thickness on the performance of the dual-mode resonator was systematically investigated by the finite element method (FEM), and resonators were prepared and verified the simulation results. The electromechanical coupling coefficients (K-2) of the SH modes are 15.1% and 17.0%, while the maximum Bode-Q (Q(max)) values are 150 and 247, respectively, for the fabricated resonators with wavelengths of 1 mu m and 1.1 mu m. In terms of the high-order SH modes in these resonators, the K-2 values are 9.8% and 8.4%, and Q(max) values are 190 and 262, respectively. The fabricated dual-band filter shows the center frequencies (f(c)) of 3065 MHz and 4808 MHz as two bands, with 3-dB fractional bandwidths (FBW) of 5.1% and 5.9%, respectively. Such a dual-band SAW filter based on a conventional ladder topology is meaningful in terms of its compact layout and diminished area occupancy. This work provides a promising avenue to constitute a high-performance dual-passband SAW filter for sub-6 GHz RF application.

Automated summary

In response to the demand for highly integrated and miniaturized radio frequency front-end (RFFE) modules, multi-passband filters that support multi-channel compounding have become the focus. This study proposes a new design of a dual-passband surface acoustic wave (SAW) filter based on a 32 degrees YX-LiNbO3 (LN)/SiO2/SiC multilayered structure. The filter is of a standalone ladder topology and consists of dual-mode resonators that simultaneously excite the shear horizontal (SH) mode and high-order SH mode through electrode thickness modulation. The fabricated dual-band filter shows compact layout and diminished area occupancy, making it a promising solution for high-performance dual-passband SAW filter for sub-6 GHz RF application.