TC-SAW 3D

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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.

im2.pngim3.png

Model Schematic for full scale (top) and quarter scale (bottom), shown without SiO2 layer for clarity.

im5.png      im4.png  

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 um
sio2_thk Thickness of Si02  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

im6.png

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:

 

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