SAW 3D Unit Cell

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SAW Displacement at Resonance

Model Description

This simple unit cell model of a single port 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.

The model comprises a pair aluminum electrodes on a piezoelectric substrate. 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.

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Model Schematic

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

Outputs

A wide range of outputs can be generated, including:

  • Electrical impedance / admittance
  • S parameters
  • Mode Shapes (Harmonic Analysis)
  • Energy flow analysis

 

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Example Post Processor Outputs

Runtime Statistics

Degrees of Freedom

 6222

Solve Time

140 s

Core Hours

0.078

Memory Usage

 17 MB

 

Files

The following input files are required to run this model, click here to download the input files:

Design Studies

The following example design studies were carried out using this model:

 

 
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Comments

2 comments
  • Thank you for this great example! I am new to piezoelectric modelling and have a question: Why do we need the bottom layer of "ltstruct" with only mechanical and electrical properties and no piezoelectric properties?

  • Hi,

    That is a great question. The material on the bottom is lithium tantalate ( the same material as the main body) but without the piezoelectric properties. It is used in this example because in OnScale it is not possible to place an absorbing boundary on a piezoelectric material.

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