Non-Zero Power Flow Angles in Surface Acoustic Wave Resonators for Transverse Mode Suppression

Abstract

The non-zero power flow angle (PFA) was proposed for transverse mode suppression in shear horizontal surface acoustic wave (SH-SAW) resonators on heterogeneous substrates. SAW resonators with different in-plane orientations based on 42° Y-cut LiTaO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> /SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /sapphire substrate were studied by simulation and experiment. The simulated 3D mode shapes demonstrate that the non-zero PFA can be realized through in-plane rotation of the interdigital-transducer (IDT), thus changing the mode displacement distribution. The resonator with an in-plane orientation θ=5° (PFA≈-9°) exhibits the transverse modes suppressed frequency response while maintaining an excellent <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</sub> ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i> value at the anti-resonance frequency) of 4105. The SAW resonator with rotated IDT on 42° Y-cut LiTaO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> /SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /poly-Si/Si substrate was also fabricated and measured. The measured results prove the general applicability of this method in suppressing transverse modes. Overall, the non-zero PFA promotes high-order transverse modes to enter the dummy electrode regions and suppresses transverse modes, and rotating IDT is a very simple method to achieve an appropriate PFA.

Topics & Concepts