Low loss mid/high band filter integration in single die using a multi-layered SAW device on a direct mount type package

In this work, we demonstrated a mid/high bands integration in single die using multi-layered SAW device on a direct mount type package. Firstly, we investigated the dependence of cut angle of LiTaO3 and electrode thickness on Surface Acoustic Wave (SAW) resonator characteristics in Leaky SAW (L-SAW) and multi-layered SAW using Finite Element Method (FEM) simulation. The admittance ratio of L-SAW strongly depends on the cut angle of LiTaO3 and electrode thickness. In contrast, the admittance ratio of multi-layered SAW depends less on both cut angle of LiTaO3 from 30°Y-X to 56°Y-X and electrode thickness per wavelength from 0.07 to 0.11. Therefore, the cut angle of LiTaO3 and the electrode thickness can be selected according to the filter bandwidth of each band by multi-layered SAW structure. Finally, we fabricated a n34/n39/n40/n41 filter bank in a single die with the same electrode thickness using a multi-layered SAW on direct mount package. The minimum insertion losses in the pass band of all filters were achieved at less than 1dB. This technology can lead to compact and high-performance integrated RF front end circuits and contribute to the miniaturization of smartphones.