Full 3D TC-SAW Surface Displacement
Model Description
This full 3D model of a single port Temperature Compensated (TC) Surface Acoustic Wave (SAW) filter provides a complete picture of device performance. By simulating the device in full 3D a range of parasitic effects can be considered to avoid carrying undesirable performance into production.
The model comprises a pair of aluminum IDT electrodes on a piezoelectric substrate. These are terminated with a grating. Above this an SiO2 layer provides temperature compensation. The substrate can either be Lithium Tantalate (LiTaO3) or Lithium Niobate (LiNbO3). The model is set up to simulate a Y-cut, which can be rotated to the desired angle. The base design generates an SH mode at 1.5 GHz using a finger pitch of 1.3 µm.
To make it easy to run initial simulations the model is set up to create a 1/4 scale device. To simulate the full device simply scale up the finger length, number of IDT pairs and the number of grating fingers as directed in the example file.
Model Schematic for full scale (top) and quarter scale (bottom), shown without SiO2 layer for clarity.
Model Schematic for full scale (left) and quarter scale (right), shown with SiO2 layer for clarity.
Design Variables
The base model allows the following design variables to be adjusted. By default electrode thickness and electrode aspect ratio are set as design variables to be swept (indicated by *).
| Design Variable | Description | Default Value |
|---|---|---|
| elec_thk * | Thickness of electrode | 200 nm |
| subs_thk | Thickness of substrate | 7.5 µm |
| sio2_thk | Thickness of Si02 | 7.5 µm |
| fin_pitch | Finger pitch | 1.3 µm |
| aratio * | Metalization aspect ratio | 0.5 |
| nfing | Number of pairs of fingers in full device | 100 |
| fin_len | Length of fingers | 50 µm |
| piezo_mat | Piezoelectric material | lt (LiTaO3) |
| cut_ang | Rotated y-cut angle | 0.5 |
| edge_y | Edge of substrate in y | 0.5 |
| eelec_len | Length of the stub fingers | 0.5 |
| egap_len | Gap at end of fingers | 0.5 |
| gap | Gap between IDT and grating | 0.5 |
| ngrat | Number of grating fingers | 0.5 |
| grat_pitch | Pitch on grating fingers | 0.5 |
| agratio | Grating metallization ratio | 0.5 |
Outputs
A wide range of outputs can be generated, including:
- Electrical impedance / admittance
- S parameters
- Mode Shapes (Harmonic Analysis)
- Energy flow analysis
Mode shape on full 3D SAW filter
Runtime Statistics
| Degrees of Freedom | 26M (2.4M for 1/4 scale) |
| Solve Time (8 cores) | 22 hours (25 min for 1/4 scale) |
| Core Hours | 176 (3.3 for 1/4 scale) |
| Memory Usage | 42 GB (4.1 GB for 1/4 scale) |
Files
The following input files are required to run this model, click here to download the input files: