Modeling and Suppression of SiO2 Guided Mode on TC-SAW with a Cancelling Circuit

A TC-SAW (Temperature Compensated Surface Acoustic Wave) by LiNbO
3
covered with a SiO
2
film structure is proposed as a temperature compensation method. The TC-SAW with SiO
2
/LiNbO
3
structure has satisfactory Q and TCF and moderate k
²
eff
. However, this structure contains various spurious responses in and out of the passband. Management of these spurious responses is necessary for TC-SAW filter design. One of the spurious responses observed well above the passband is the SiO
2
guided mode. Suppression of this spurious mode is critical to achieving the attenuation required by Carrier Aggregation. This study discusses the SiO
2
guided mode analysis and modeling method. Additionally, a design technique for suppression of the SiO
2
guided mode by means of a cancelling circuit is discussed and applied to a ladder-type filter design.