Modal displacement of a wafer bonded TC SAW at series resonance
This simple unit cell model of a single port Temperature Compensated (TC) Surface Acoustic Wave (SAW) filter allows rapid simulation of device performance. This allows a very wide range of designs to be explored before moving to more complex full 3D simulations. This particular device uses a wafer bonded layer of Lithium Tantalate (LiTaO3) on top of a silicon substrate.
The model comprises a pair aluminium electrodes on top of the LiTaO3 piezo layer. This structure sits on a silicon substrate. The model is set up to simulate a Y-cut, which can be rotated to the desired angle - set to 36 degrees by default. The base design generates a leaky mode at 1.5 GHz using a finger pitch of 1.3 µm.
The base model allows the following design variables to be adjusted. By default electrode thickness and LiTaO3 thickness are set as design variables to be swept (indicated by *).
|Parametric Variable||Description||Default Value|
|subs_thk||Thickness of substrate||10 um|
|elec_thk*||Thickness of the electrodes||200 nm|
|piezo_thk*||Thickness of piezo layer||600 nm|
|fin_pitch||SAW finger pitch||1.3 um|
|aratio||Electrode aspect ratio||0.5|
|nfing||Number of finger pairs||100|
|fin_len||Finger length||50 um|
A wide range of outputs can be generated, including:
- Electrical Impedance / admittance
- S parameters
- Mode Shapes (Harmonic Analysis)
- Energy flow analysis
Typical Impedance output
|Degrees of Freedom||6800|
|Solve Time||63 secs (8 CPUS)|
|Memory Usage||72 MB|
The following input files are required to run this model: