SAW 3D

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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 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.

im1.png

im2.png

Model Schematic for full scale (top) and quarter scale (bottom)

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 um

fin_pitch

Finger pitch

 1.3 um

aratio *

Metalization aspect ratio

 0.5

nfing

Number of pairs of fingers in full device

 100

fin_len

Length of fingers

 50 um

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

Runtime Statistics

Degrees of Freedom

 25M (2.3M for 1/4 scale)

Solve Time (8 cores)

 32 hours (20 min for 1/4 scale)

Core Hours

 256 (2.7 for 1/4 scale)

Memory Usage

 32 GB (2.5 GB for 1/4 scale)

 Files

The following input files are required to run this model:

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