TC-SAW 3D Unit Cell

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im1.png

Modal displacement of a TC SAW at series resonance

Model Description

This simple unit cell model of a single port Temperature Compensated (TC) 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 aluminium electrodes on a piezoelectric substrate. Above the electrodes a layer of SiO2 is used for 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.

im2.png

Model Geometry, with SiO2 TC layer highlighted

Design Variables


The base model allows the following design variables to be adjusted. By default electrode thickness and SiO2 thickness are set as design variables to be swept (indicated by *).

Parametric Variable

Description

Default Value

 subs_thk

Thickness of substrate

 7.5 um

 elec_thk*

Thickness of the electrodes

 200 nm

 si02_thk*

Thickness of Si02 layer

 350nm

 fin_pitch

SAW finger pitch

 1.3 um

 aratio

Electrode aspect ratio

 0.5

 nfing

Number of finger pairs

100

 fin_len

Finger length

50 um

piezo_mat

Piezo material

lt

cut_ang

Y-cut angle

42

 Outputs


A wide range of outputs can be generated, including:

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

im3.png

im4.png

Typical outputs, Impedance (top) mode shape (bottom)

 

Runtime Statistics

Degrees of Freedom

 6426

Solve Time

 74 secs (8 CPUS)

Core Hours

 0.16

Memory Usage

 75 MB

Files

The following input files are required to run this model:

Design Studies

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

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