Solidly Mounted Resonator (SMR)

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In this tutorial we will learn how to simulate a 2D Solidly Mounted Resonator (SMR).  We will analyse the maximum velocity and impedance of the device and the mode shapes.

You will learn:

  • The basic simulation workflow in OnScale Designer
  • How to set up a 2D model
  • How to create a simple geometry

How to duplicate geometries

  • How to pattern out geometry
  • How to use material copies for easy load assignment
  • How to display and post-process results

What is an SMR?: SMRs are a type of film bulk acoustic resonator for microwave operation applications and is usually a set of quarter wavelength thick layers attached to a substrate fabricated onto a the resonator. 

Model Definition

model.png

Characteristics of the model

Model:

SMR

Mesh Size:

15 Elements per Wavelength

Analysis Time:

2.5 us

Output Results:

-Data Array of Maximum Y Velocity 

-Velocity Mode Shape at 2 GHz

Material Data

Name

Code Name

Density 

Bulk Velocity 

Shear Velocity

Poling

Aluminum Nitride

aln

3260 kg.m-3

-

-

Y+

Aluminium

alum

2690 kg.m-3

6306 ms-1

3114 ms-1

-

Silicon, Generic

si

2330 kg.m-3

7526 ms-1

4346 ms-1

-

Silicon Dioxide, Generic

sio2

2650 kg.m-3

5750 ms-1

2200 ms-1

-

Tungsten, Generic

tung 19400 kg.m-3 5200 ms-1 2900 ms-1 -

Aluminum Nitride (Copy)

aln 3260 kg.m-3 - - Y+

Note: All of these materials were taken from the Project Materials Database. However, aln2 is a copy of the material aln which is used to define a load across only half of the aluminium nitride layer.

Why This Simulation?

SMRs use acoustic mirrors (Bragg layers) typically to reduce substrate losses to maintain a high quality factor, a key performance metric for these types of filters. Simulation can be used to find a design which minimises these losses.

The simple 2D model consists of an Aluminum Nitride active layer on top multiples layers of Silicon Dioxide and Tungsten and Silicon substrate.

The Simulation Process

Let's go through the step by step tutorial and see how to simulate a 2D SMR in OnScale!

Step 1 - Create a New Project

Open up OnScale in Designer Mode. The first step is to create a new project.

  1. Click New Project to open the New Project dialogue
  2. Enter Model Name
  3. Change working units to um 
  4. Set Model Type to 2D
  5. Click ... to choose a directory to save the project to
  6. Click OK to create the project.
new_prjct.png

Step 2 - Set the Frequency of Interest

First we will specify the frequency of interest.

  1. Select Project Settings in the Model Tree
  2. Expand the Frequency of Interest property
  3. Tick the box
  4. Enter a value of 2e9
  5. Expand the Frequency of Damping property
  6. Tick the box
  7. Enter a value of 2e9
project_settings.png

Step 3 - Add the Materials from the Material DB

The second step is to add the required materials for the SMR to the Project Materials database.

Aluminum Nitride

Add positively polled piezoelectric material.

  1. Click Project Materials icon to open the Material Database
  2. Expand the 'Piezoelectric' materials dropdown 
  3. Double click 'Aluminium Nitride- aln' to add this to Project Materials
aln.png

Silicon / Silicon Dioxide

Add substrate material.

  1. Expand the 'Misc' materials dropdown 
  2. Double click 'Silicon, generic - si' to add this to Project Materials
  3. Double click 'Silicon Dioxide, generic - sio2' to add this to Project Materials
silicon.png

Tungsten

Now add the bragg layers material.

  1. Expand 'Metal' materials dropdown 
  2. Double click on 'Tungsten, generic - tung' to add it to Project Materials
tung.png

Aluminium Nitride (Copy)

Now copy AlN material.

  1. Right click 'aln' and select Copy
  2. Set Material Name to aln2
  3. Select OK
  4. Select Done
aln2.png

Step 4 - Create Basic Geometric Shapes

We will make use of the geometric primitives to build the SMR. The geometry consists of a silicon substrate, bragg layers and a resonator.

Substrate

We will start by creating the substrate. 

  1. Select the Rectangle primitive
  2. Set the Material property of primitive_1 to si
  3. Set the X End property to 100
  4. Set the Y End property to 2
prim1.png

Bragg Layers

Next we will add geometry to represent the 5 Bragg layers.

  1. Select the Rectangle primitive
  2. Set the Material property of primitive_2 to tung
  3. Set the Y Begin property to 2
  4. Set the X End property to 100
  5. Set the Y End property to 2.65
  6. Set Pattern Type to Linear
  7. Expand Num of Reps. and set X to 1
  8. Set Y to 5
  9. Expand Seperation Distance and set X to 0
  10. Set to 1.39
prim2.png
  1. Select the Rectangle primitive
  2. Set the Material property of primitive_3 to sio2
  3. Set the Y Begin property to 2.65
  4. Set the X End property to 100
  5. Set the Y End property to 3.39
  6. Set Pattern Type to Linear
  7. Expand Num of Reps. and set Y to 5
  8. Expand Seperation Distance and set Y to 1.39
prim3.png

Aluminim Nitride Resonator

Having added the Bragg layers, lastly we need to add the piezoelectric layer to act as the resonator.

  1. Select the Rectangle primitive
  2. Set the Material property of primitive_4 to aln
  3. Set the Y Begin property to 8.95
  4. Set the X End property to 50
  5. Set the Y End property to 11.7
prim4.png
  1. Select the Rectangle primitive
  2. Set the Material property of primitive_5 to aln
  3. Set the X Begin property to 50
  4. Set the Y Begin property to 8.95
  5. Set the X End property to 100
  6. Set the Y End property to 11.7
prim5.png

The resulting SMR geometry should be as follows:

geom.png

Step 5 - Define a Time Function

The next step is to add a drive function. We will use a Ricker Wavelet function with a frequency of 2 GHz.

  1. Click '+' to open the Drive Function dialogue
  2. Change function type from Sinusoidal to Ricker Wavelet
  3. Set Drive Frequency to 2e9
  4. Click Insert to close the window. A record called timefunc_1 will be added to the Model Tree
time_func.png

Step 6 - Choose The Right Mesh Size

It is time to set up the meshing of the model. 

  1. Expand Model in the Model Tree
  2. Expand Mesh 
  3. Select Configuration
  4. Set Definitions to Advanced
  5. Set Elements per Wavelength to 15
  6. Expand Mesh Velocity
  7. Set Value to 6000
mesh.png

Step 7 - Create Voltage Loads Across Piezo

We will now create two loads on each side of the aln material.

  1. Expand Boundary Conditions in the Model Tree
  2. Click '+' to open the Load dialogue
  3. Set Creation Mode to be Geometry Interface
  4. Set Geometry to primitive_4
  5. Set Interfacing Item to side 4 (ymax)
  6. Select Create Load
  7. Repeat steps 3-6 for the following
load_def.png

Geometry

Interfacing Item

primitive_4

primitive_3

Change the properties of the loads

Now that each load has been defined, we can set each load's properties.

  1. Select load_1
  2. Set Load Type to Voltage
  3. Set Area Scaling to 0.0002
  4. Set Termination to timefunc_1
  5. Set Amplitude Scale Factor to 1
  6. Select load_2
  7. Set Load Type to Voltage
  8. Set Area Scaling to 0.0002
  9. Set Termination to Ground
load_prop.png

Step 8 - Define the Boundary Conditions

We will now apply boundaries to the exterior surfaces of the SMR.

  1. Click Domain Boundaries in the Model Tree
  2. Set X Minimum to Symmetry
  3. Set X Maximum to Impedance
  4. Set Density to 3385
  5. Set Longitudinal Velocity to 11099.6
  6. Set Shear Velocity to 6012.87
  7. Set Y Minimum to Impedance
  8. Set Density to 3385
  9. Set Longitudinal Velocity to 11099.6
  10. Set Shear Velocity to 6012.87
  11. Set Y Maximum to Free
boun.png

Step 9 - Define Simulation Time

We will now set the model simulation time to be 2.5 us.

  1. Click Analysis 
  2. Change Simulation Run Time to 2.5e-6
analysis.png

Step 10 - Define the Simulation Output Results

We will now define the 2 outputs we wish to see - data array of max velocity and a velocity mode shape at the center frequency.

Output Result 1 : Field Data Array of Maximum Velocity

  1. Click '+' to create a new output
  2. Set Output Type to Field Data
  3. Set Array Type to Velocity
  4. Set Array Component to Y
  5. Set Field Type to Maximum
out2.png

Output Result 2 : Velocity Mode Shape at Center Frequency

  1. Click '+' to create a new output
  2. Set Output Type to Shape Data
  3. Set Array Type to Velocity
  4. Set Array Component to Y
  5. Set Frequency to 2e9
out2.png

Step 11 - Run the Simulation on the Cloud

At this point the model is completely set up and it can now be run on the cloud.

  1. Click Run on Cloud 
  2. Select Estimate 
  3. Select Run
run.png

How to Get the Simulation Results?

Once the simulation has finished, the results are available in your storage to download.

  1. Click the Storage icon to open the cloud storage
  2. Select your job from the dropdown menu
  3. Expand the simulation folder
  4. CTRL + select the -shape.flxdato, flxdato & flxhst file, right click and select Download Selection
storage.png

Choose an appropriate save location and close the cloud storage.

Step 12 - Check the Simulation Results

Switch to the Post Processor

  1. Click this icon to access the Post Processor to analyse simulation results
ppswitch.png

Open Results

  1. Click File Explorer
  2. Double click the -shape.flxdato to open the shape results
  3. Double click the .flxdato file to open the data array results
  4. Double click the history file to open the time history results
file_explorer.png

Velocity Mode Shape at Center Frequency

  1. Expand Mode Shapes
  2. Expand Mode-1
  3. Right-click yvel and select Plot Shape Movie
  4. In the Model Graphics tab, select Symmetry > About X
  5. Set Scale Factor to 0.01
  6. Select Play button to play mode shape animation
yvel.png

Data Array of Maximum Y Velocity

  1. Expand Time-179652 
  2. Double click 'yvmx' to plot maximum velocity data field
  3. Select Continue
  4. Select Surface Plot
  5. Rotate viewport to see suface plot of yvmx
yvmx.png

Impedance

  1. Select pize load1:Voltage 
  2. Select Impedance button
  3. Double click Impd:load1.amp
  4. Select Continue
  5. Select Log yAxis
  6. Set xAxis Minimum to 1.8e9
  7. Set xAxis Maximum to 2.2e9
impd.png

Try for Yourself

Now that we have introduced you to the tutorial, try have a play around with some of the settings, add some other outputs, or use this model as a starting point of your own.

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