SAW 3D - CAD

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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.

 

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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 project file is required to run this model:

The base CAD model is publicly available to view and copy through Onshape:

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