Tutorial for XFDTD Written by Cynthia Furse Utah State University
Tutorial for XFDTD
Written by Cynthia Furse
Utah State University
XFDTD
• 3D Finite Difference Time Domain code
• Written by Remcom, Inc.
• http://www.remcom.com
To start XFDTD at USU
• Edit your .cshrc file. Add the path/opt/xfdtd
• Type “source .cshrc” to run this file (otherwise you would have to log out/in)
Other versions of XFDTD available:
• Version 5Add path /opt/xfdtd/version5
• Multiple user-defined sourcesAdd path /opt/xfdtd/quicksign
This is what the XFDTD Window Looks Like
To Create an FDTD Grid Space:
Define the FDTD Grid
Cell Size
Total Space (model plus surrounding air)
This means you will be defining the materials at the locations of the E field components
View the Grid.
This will show you the grid. So far it contains only air.
Orientation.You are viewing the xy-plane.Slice #Zoom FactorWhere in the plane...
Location of your cursor
To change the plane you are viewing:
Edit the Menu of Electrical Material Parameters
Edit Electrical Properties of the Materials to be in your model
Material 0=airMaterial 1 = PEC (metal)Here Material 2 will be teflon.
r
Display the Edit Panel to Draw or Edit your Model
Here are Several Model Elements
Choose Material
Draw one planeor more simultaneously.
Types of Single-Cell Models
Wire Plate Cube
The Library has Other Elements
Let’s Start with a Single-Cell “Wire” made of Material 2
Ex
Ey
EzEach Cell has Ex, Ey, Ez components
Electric Grid Lines Represent Each Ex,Ey,Ez Component…
(The Grid has also been Zoomed)This means the Ex component is “in” material 2 (but the Ey,Ez components are in material 0=air)
Ez is in Material 2
Ey is in Material 2
See How a Cube of Material is Defined in this layer:
Ex
ExEyEy
Ez
Ez
Ez
Ez
And in the Layer Above it
Ex
Ex
EyEy
No Ez’s
Draw the Teflon Box for Patch Antenna on Slice 25
Alternatively we could have used rectangular box in the library.
Hold Middle Mouse Button to Drag, Click Left Button to Build.
Add Another Layer
Slice 26
And Another
Slice 27
The Top is Slice 28
But we want the top of the patch antenna to be metal, so choose the plate element
and change it to Material 1 (PEC)
Add a plate to the bottom, too.
Slice 24
(Checking the coordinates of the teflon box in layer 25 and repeating them on layer 24 helped draw this plate)
Look at this “sandwich” in the yz and xz planes
If the plates andboxes aren’t linedup correctly, fix them
We want to add a feedpoint to the center. Use the cursor to find
where this is.
(24,28)
Look at the feed location
X=24
View-YZplane
Use Single Cell Wire (PEC) from Edit Panel
Use these wires to connect top to bottom plate, leaving one cell gap
for voltage feed source
3 single-cellwires in thez (vertical)direction
gap
Find the Location of the Feed Point Gap with the Cursor
(24,28,27)
Open Voltage Sources Panel
Choose a Source and “Add Feed to List”. You may have several
sources.
This is yourfeedpoint location
Close the Source Window, and Reopen It to see the source
location on your grid.
The source location will only show when the source window is open.
Define what you want FDTD to save after calculation
Other valuesof interest areavailable forsine wave sourceonly
These areavailable forpulsed FDTD
Save your geometry
Save FDTD Parameters
Run FDTD
This is what is displayed