Impact of in-plane diffraction in TC-SAW Resonator

This work investigates impact of SAW diffraction on anti-resonance quality factor Q<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a</inf> in Temperature Compensated Surface Acoustic Wave (TC-SAW) Resonator using 131-LN. First, excellent agreement is seen between the full three-dimensional finite element method simulation and measurement, in which the Cu stripes are not applied for transverse modes suppression. Next loss analysis is given to case of TC-SAW by studying impact of number of IDT finger pairs(N<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</inf>) and aperture length(W), whose slowness curve is concave. Then the same analysis is given to I.H.P. SAW case. It is shown the Bode Q curves, in TC-SAW cases, are more sensitive to the frequency(f) , W and N<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</inf> due to the stronger in-plane diffraction thus making the achievable Q<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a</inf> low. In other words, the main loss mechanism causing lower Q<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a</inf> in TC-SAW than I.H.P.SAW is the in-plane diffraction.