Full 3D SAW Surface Displacement
Model Description
This full 3D model of a single port 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. 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 specified in the material properties. 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. A CAD file of this 1/4 scale device is provided with the example file set.
Model Schematic for quarter scale
Parametric Variables
The base CAD model was created in Onshape and allows the following design variables to be adjusted. By default the number of pairs of fingers, metallization aspect ratio, finger length, and number of grating fingers are added as configuration variables for quick access through the Configuration Panel in Onshape.
| Parametric Variable | Description | Default Value |
|---|---|---|
| nfing | Number of pairs of fingers in full device | 100 |
| aratio | Metallization aspect ratio | 0.5 |
| fin_len | Length of the fingers | 50 µm |
| ngrat | Number of grating fingers | 40 |
| elec_thk | Thickness of electrode | 200 nm |
| subs_thk | Thickness of substrate | 7.5 µm |
| fin_pitch | Finger pitch | 1.3 µm |
| edge_y | Edge of substrate in y | 2 µm |
| eelec_len | Length of the stub fingers | 1 µm |
| egap_len | Gap at end of fingers | 650 nm |
| gap | Gap between IDT and grating | 1.035 µm |
| grat_pitch | Pitch on grating fingers | 1.3 µm |
| 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 1/4 Scale 3D SAW filter
Runtime Statistics
| Model size | 67199 elements |
| Solve Time | 84 s (4 CPU) |
| Core Hours | 0.0939 |
| Memory Usage | 23 MB |
| Recommended CPU Configuration | 4 CPU |
CAD Project File
The following input files are required to run this model, click here to download the input files:
The base CAD model is publicly available to view and copy through Onshape: