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Complete XF project with results (ZIP, 125 MB)


An unmatched GPS Bluetooth antenna is created and simulated to determine how the antenna's length affects its performance.

This tutorial begins by adding the necessary materials and parameters and using them to create device geometry, including an unmatched feed that connects the printed circuit board (PCB) to the antenna using a ground connection and tab. The antenna radiator is parameterized in order to evaluate each antenna length from 20 to 30 mm in 1.25 mm increments, and is connected to a voltage source with 50 ohm resistor and automatic waveform to match the project's frequency range of interest from 1 to 3 GHz.

The grid is then defined with smaller cell sizes for increased accuracy, and port, surface current, and far zone sensors collect data during simulation. S-parameter, VSWR, and far zone results are analyzed to see the impact of the parameterized antenna length.

This tutorial utilizes the following skills:

Step 1: Set the Project Properties

Setting the frequency range of interest is the first step in the workflow because XFdtd uses this information when constructing the grid, creating a waveform, and setting the bounds of output plots. This simulation focuses on the antenna's performance from 1 GHz to 3 GHz.

  1. In the upper-left corner of XF, click Edit, then select Project Properties to open the editor.
  2. Under the Frequency Range of Interest tab, enter 1 GHz as the Minimum.
  3. Enter 3 GHz as the Maximum.
  4. Click Done to close the editor.

Step 2: Add the Materials

A material must be associated with each part in order to define its electromagnetic properties, so the necessary materials are first defined and then assigned to each part. The copper material is added to the project from the library, and the FR4 material is created in XF. The project tree's materials node allows users to define a set of electromagnetic properties once and use it in multiple places.

First, add the copper material.

  1. Click on the Libraries button on the right side of XF to open the Libraries window.
  2. In the Libraries section on the left side of the window, select Materials- Pure Metals.
  3. In the Filters section, select Materials.
  4. In the lower portion of the window, click on Copper (Pure) [ND] and drag it to the Materials node of the Project Tree.
  5. Close the Libraries window.
  6. Double-click on Copper (Pure) [ND] in the Project Tree to open the Material Editor.

Next, add a parameter to make the copper material valid.

  1. Click the Parameters button on the right side of XF.
  2. Click the Add button button in the upper-left corner of the Parameters window.
  3. Enter the Name by typing materialFrequency into the highlighted field.
  4. Press Tab and type 1.575 GHz into the Formula field.
  5. Click Apply to populate the Value field and apply the Parameter to the project.
  6. Close the Parameters window.
  7. Click Done to close the Material Editor.

Then, create the FR4 material.

  1. Right-click on the Materials node in the Project Tree and select New Material Definition.
  2. Name the material by typing FR4 into the highlighted field.
  3. Press Enter to save the name to the project.
  4. In the Project Tree, double-click on FR4 to open the Material Editor.
  5. Under the Electric tab, change the Entry Method by selecting Loss Tangent from the drop-down menu.
  6. Enter 3.4 as the Relative Permittivity.
  7. Enter 0.014 as the Loss Tangent.
  8. Enter materialFrequency as the Evaluation Frequency.
  9. If desired, navigate to the Appearance tab and change the FR4 material’s display color.
  10. Click Done to close the Material Editor.

Step 3: Create the PCB Geometry

This tutorial focuses on antenna analysis, and requires a simplified PCB containing only a ground plane and substrate made of copper and FR4, respectively.

First, create a ground plane.

  1. In the Project Tree, right-click on the Parts branch and select Create NewExtrude to open the editor.
  2. Under the Edit Cross Section tab, use the drop-down arrow to choose the Rectangle tool in the toolbar.
  3. In the Geometry window, click on (0, 0, 0) to select the first corner.
  4. Click on (60 mm, 120 mm, 0 mm) to select the second corner and close the rectangle

Create a cutout in the ground plane.

  1. Click again on (60 mm, 120 mm, 0 mm) to select the first corner of the smaller rectangle.
  2. Drag the mouse left 3 mm and down 20 mm, then click to select the second point and close the rectangle.
  3. Click on the Trim Edges tool on the left side of the toolbar.
  4. In the Geometry window, click on one of the overlapping lines to remove it.
  5. Click again to remove the second line.
  6. Click on the other pair of overlapping lines to remove one of them.
  7. Click again to remove the second line.

Round the corners of the ground plane.

  1. Click the Fillet Vertex tool.
  2. In the Geometry window, click on the vertex located at (0 mm, 120 mm, 0 mm) and drag it inward 1 mm.
  3. Click again to apply the rounded edge.
  4. Click on the vertex located at (0 mm, 0 mm, 0 mm) and drag it inward 1 mm.
  5. Click again to apply the rounded edge.
  6. Click on the vertex located at (60 mm, 0 mm, 0 mm) and drag it inward 1 mm.
  7. Click again to apply the rounded edge.
  8. Click on the vertex located at (60 mm, 100 mm, 0 mm) and drag it inward 1 mm.
  9. Click again to apply the rounded edge.
  10. Click on the vertex located at (57 mm, 100 mm, 0 mm) and drag it outward 1 mm.
  11. Click again to apply the rounded edge.
  12. Click on the vertex located at (57 mm, 120 mm, 0 mm) and drag it inward 8 mm.
  13. Click again to apply the rounded edge.
  14. Name the extrude by typing Ground Plane into the Name field.

Give the ground plane thickness.

  1. Under the Extrude tab, enter 0.1 mm as the Extrude Distance.
  2. Enter -1 as the W′ value.
  3. Click Done to add the Ground Plane to the project.

Then, assign the copper material to the ground plane.

  1. Click on Copper (Pure) [ND] in the Definitions branch of the Project Tree and drag it to the Ground Plane in the Parts branch.

Then, create a substrate.

  1. In the Project Tree, right-click on the Parts branch and select Create NewSheet Body from Faces to open the editor.
  2. Select the face in the XY plane by clicking in the Geometry window.
  3. Name the part by typing Substrate into the Name field.
  4. Click Done to add the Substrate to the project.

Give the substrate thickness.

  1. In the Project Tree, right-click on Substrate and select ModifyThicken Sheet to open the editor.
  2. Type 0.7 mm into the Distance field.
  3. Uncheck the Thicken Both Sides option.
  4. Click Done to apply the modifications to the project.

Finally, assign the FR4 material to the substrate.

  1. Click on FR4 in the Definitions branch of the Project Tree and drag it to the Substrate in the Parts branch.

Step 4: Add the Ground Connection Assembly

An assembly organizes a project's geometry by grouping parts together in the project tree, and users can assign a material to either the entire assembly or the individual parts within it. For this project, a ground connection assembly is created and the via and pad are defined within it. The assembly is then moved into the correct position relative to the PCB.

First, create an assembly and add the via.

  1. In the Parts branch of the Project Tree, press Ctrl while clicking on Ground Plane and Substrate to select both parts, then right-click and choose Set Invisible.
  2. Right-click on Parts and select Create NewAssembly.
  3. Enter the name by typing Ground Connection into the highlighted field.
  4. Press Enter to apply the name change.
  5. Right-click on the Ground Connection assembly and select Create NewCylinder to open the editor.
  6. Under the Edit Cylinder tab, type 0.7 mm into the Height field.
  7. Enter 0.15 mm as the Radius.
  8. Name the cylinder by typing Via into the Name field.
  9. Click Done to add the Via to the project.

Next, create the pad and add it to the assembly.

  1. In the Project Tree, right-click on the Ground Connection assembly and select Create NewSheet Body to open the editor.
  2. Under the Specify Orientation tab, enter 0.7 mm as the Z value.
  3. Under the Edit Profile tab, select the Rectangle tool in the toolbar.
  4. Press Tab to specify the position of the first point.
  5. Enter -0.25 mm as the U′ value.
  6. Enter -0.25 mm as the V′ value.
  7. Click OK.
  8. Press Tab to specify the position of the second point.
  9. Enter 0.25 mm as the U′ value.
  10. Enter 0.25 mm as the V′ value.
  11. Click OK to close the rectangle.
  12. Name the Sheet Body by typing Pad into the Name field.
  13. Click Done to close the editor and add the Pad to the project.

Then, assign a material to the assembly.

  1. In the Definitions branch of the Project Tree, click on Copper (Pure) [ND] and drag it to the Ground Connection assembly in the Parts branch.

Finally, move the geometry into place.

  1. In the Project Tree, press Ctrl while clicking Ground Plane and Substrate to select both parts, then right-click and choose Set Visible.
  2. Right-click on the Ground Connection assembly, then select ModifySpecify Orientation to open the editor.
  3. Enter 41.3 mm as the X value.
  4. Enter 118.85 mm as the Y value.
  5. Enter 0 mm as the Z value.
  6. Click Done to close the editor and apply the changes to the project.

Step 5: Create the Antenna Radiator

Parameters applied to a project can be used to define geometry. For this tutorial, both a length and a width parameter are added and then used to define the antenna radiator. The antenna is created from an extrude with both a rectangle and circle cutout, modified, and rotated.

First, add parameters to the project.

  1. In the Parts branch of the Project Tree, press Ctrl while clicking on Ground Plane, Substrate, and Ground Connection to select the three parts, then right-click and choose Set Invisible.
  2. Click on the Parameters button on the right side of XF.
  3. Click the Add button button in the upper-left corner of the Parameters window.
  4. Enter the parameter name by typing antennaLength into the highlighted field.
  5. Press Tab and type 21.25 mm into the Formula field.
  6. Click the Add button button to add another parameter.
  7. Type antennaWidth into the highlighted Name field.
  8. Press Tab and type 5.16 mm into the Formula field.
  9. Click Apply to apply the parameters to the project.
  10. Close the Parameters window.

Next, define the antenna.

  1. In the Project Tree, right-click on the Parts branch and select Create NewAssembly.
  2. Name the Assembly by typing Antenna and Contact into the highlighted field.
  3. Press Enter to apply the name change.
  4. Right-click on the Antenna and Contact assembly, then select Create NewExtrude to open the editor.
  5. Under the Edit Cross Section tab, use the drop-down arrow to choose the Rectangle tool in the toolbar.
  6. Select the first corner by clicking (0 mm, 0 mm, 0 mm) in the Geometry window.
  7. Select the second corner by clicking on any coordinates to close the rectangle.
  8. Click on the Select tool in the toolbar.
  9. In the Geometry window, click on (0 mm, 0 mm, 0 mm) to select the vertex.
  10. Right-click on the vertex and select Lock Position.
  11. On the right side of the toolbar, use the drop-down arrow to select the Distance constraint.
  12. In the Geometry window, click on a long edge of the rectangle.
  13. Move the cursor outward, then click to place a length indicator away from the selected edge.
  14. Enter antennaLength into the highlighted field.
  15. Press Enter to apply the parameter and display the length label.
  16. Click on the short edge of the rectangle.
  17. Move the cursor outward, then click to place a width indicator away from the selected edge.
  18. Enter antennaWidth into the highlighted field.
  19. Press Enter to apply the parameter and display the width label.

Then, add cutouts.

  1. Select the Rectangle tool in the toolbar.
  2. Press Tab to specify the first corner position.
  3. Enter 3.264 mm as the U′ value.
  4. Enter 1.384 mm as the V′ value.
  5. Click OK to close the editor.
  6. Press Tab to specify the second corner position.
  7. Enter 9.68 mm as the U′ value.
  8. Enter 2.584 mm as the V′ value.
  9. Click OK.
  10. Select the Circle Center, Radius tool in the toolbar.
  11. Press Tab to specify the circle center's position.
  12. Enter 16.55 mm as the U′ value.
  13. Enter 1.9 mm as the V′ value.
  14. Click OK.
  15. Press Tab to specify the radius position.
  16. Enter 0.6 mm as the Radius value.
  17. Click OK.
  18. Name the antenna by typing Antenna into the Name field in the upper-right corner of the editor.

Give the antenna thickness.

  1. Under the Extrude tab, enter 0.01 mm as the Extrude Distance.
  2. Click Done to close the editor and add the Antenna to the project.

Blend the antenna's edges.

  1. In the Project Tree, right-click on Antenna and select ModifyBlend Edges to open the editor.
  2. Click to select a vertical edge of the cutout rectangle.
  3. Press Ctrl while clicking on the second vertical edge of the cutout rectangle .
  4. Press Ctrl while clicking on the third vertical edge of the cutout rectangle.
  5. Press Ctrl while clicking on the fourth vertical edge of the cutout rectangle.
  6. In the sidebar, use the View Left button button's drop-down arrow to select View from +Z (Top).
  7. Press Ctrl while clicking on one of the vertical edges on the right side of the large rectangle.
  8. Press Ctrl while clicking on the other vertical edge on the right side of the large rectangle.
  9. Under the Specify Radius tab, enter 0.5 mm as the Blend Radius.
  10. Click Done to save the changes to the project.
  11. In the Project Tree, right-click on Antenna and select ModifyBlend Edges to open the editor.
  12. Click to select a vertical edge on the left side of the large rectangle.
  13. Press Ctrl while clicking on the second vertical edge on the left side of the large rectangle.
  14. Under the Specify Radius tab, enter 2 mm as the Blend Radius.
  15. Click Done to save the changes to the project.

Then, bend the antenna.

  1. In the Project Tree, right-click on Antenna and select ModifyBend to open the editor.
  2. Under the Specify Bend tab, enter -1 as the U′ value in the Bend Axis (red) section.
  3. Enter 0 as the V′ value.
  4. Enter 0 as the W′ value.
  5. In the Normal (yellow) section, enter 0 as the U′ value.
  6. Enter 0 as the V′ value.
  7. Enter 1 as the W′ value
  8. In the Origin section, enter 0 mm as the U′ value.
  9. Enter 3.16 mm as the V′ value.
  10. Enter 0 mm as the W′ value.
  11. Enter 2 mm as the Radius value.
  12. Enter 2 mm as the Width.
  13. Uncheck the Centered Bend option.
  14. Check the Localized, View bend region, and Apply bend options.
  15. Click Done to apply the changes and close the editor.
  16. In the Project Tree, right-click on Antenna and select ModifyBend to open the editor.
  17. Under the Specify Bend tab, enter 0 as the U′ value in the Bend Axis (red) section.
  18. Enter 1 as the V′ value.
  19. Enter 0 as the W′ value.
  20. In the Normal (yellow) section, enter 0 as the U′ value.
  21. Enter 0 as the V′ value.
  22. Enter 1 as the W′ value.
  23. In the Origin section, enter 8.3 mm as the U′ value.
  24. Enter 2.584 mm as the V′ value.
  25. Enter 0.01 mm as the W′ value.
  26. Enter 90 degrees as the Angle.
  27. Enter 15 mm as the Radius.
  28. Verify that Centered Bend is unchecked.
  29. Verify that the Localized, View bend region, and Apply bend options are checked.
  30. Click Done to save the changes to the project.

Assign a material to the antenna.

  1. Click on Copper (Pure) [ND] in the Definitions branch of the Project Tree, and drag it to the Antenna in the Parts branch.

Finally, rotate the antenna.

  1. In the Project Tree, right-click on Antenna and select ModifySpecify Orientation to open the editor.
  2. Right-click on the U-axis' red arrow in the geometry window and select Rotate Around U′.
  3. Enter 90 degrees.
  4. Click Done to save the changes to the project.

Verify that the Antenna is in the correct plane relative to the Substrate by clicking on Substrate in the Project Tree and looking in the Geometry window.

Step 6: Create the Antenna Contact Geometry

Geometry added to the antenna and contact assembly includes a pad created from a sheet body, and a contact that combines a cylinder and frustum. A copper material is assigned to these parts, and the pad attaches them to the substrate.

First, create the large pad.

  1. In the Parts branch of the Project Tree, right-click on Antenna and select Set Invisible.
  2. Right-click on the Antenna and Contact assembly and select Create NewSheet Body to open the editor.
  3. Under the Edit Profile tab, select the Rectangle tool in the toolbar.
  4. Press Tab to specify the first point.
  5. Enter -0.5 mm as the U′ value.
  6. Enter -0.5 mm as the V′ value.
  7. Click OK.
  8. Press Tab to specify the second point.
  9. Enter 0.5 mm as the U′ value.
  10. Enter 0.5 mm as the V′ value.
  11. Click OK to close the rectangle.
  12. Name the rectangle by typing Large Pad into the Name field.
  13. Click Done to save the changes to the project.

Then, assign a material to the large pad.

  1. Click on Copper (Pure) [ND] in the Definitions branch of the Project Tree, and drag it to the Large Pad in the Parts branch.

Next, create the contact.

  1. In the Project Tree, right-click on the Antenna and Contact assembly and select Create NewCylinder to open the editor.
  2. Under the Edit Cylinder tab, enter 0.75 mm as the Height.
  3. Enter 0.25 mm as the Radius.
  4. Click Done to save the Cylinder to the project.

Then, create the frustum.

  1. In the Project Tree, right-click on the Antenna and Contact assembly and select Create NewFrustum to open the editor.
  2. Under the Specify Orientation tab, enter 0.75 mm as the Z value.
  3. Under the Edit Frustum tab, enter 0.25 mm as the Height.
  4. Enter 0.25 mm as the Radius 1 value.
  5. Enter 0.25 mm as the Radius 2 value.
  6. Enter 0.125 mm as the Top value.
  7. Click Done to save the Frustum to the project.

Combine the cylinder and frustum into one part.

  1. Press Ctrl while clicking to select both the Cylinder and Frustum in the Project Tree, then right-click and select BooleanUnion to open the dialog box.
  2. Click OK to apply the default settings and combine the two parts.
  3. In the Project Tree, right-click on the modified Cylinder and select Rename.
  4. Enter Contact into the highlighted field.
  5. Press Enter to apply the name change.

Next, smooth the edge.

  1. Right-click on Contact and select ModifyBlend Edges to open the editor.
  2. In the Geometry window, click on the edge that separates the cylindrical portion from the narrowed end.
  3. Under the Specify Radius tab, enter 0.3 mm as the Blend radius.
  4. Click Done to save the rounded profile to the project.

Finally, assign a material to the contact.

  1. Click on Copper (Pure) [ND] in the Definitions branch of the Project Tree and drag it to the Contact in the Parts branch.

Step 7: Create the Antenna Tab and Reposition

The antenna tab is created from an extrude, then modified, and assigned the copper material. The tab connects the antenna and contact, and the entire assembly is moved to the correct position relative to the substrate.

First, create the antenna tab.

  1. In the Project Tree, right-click on the Antenna and Contact assembly and select Create NewExtrude to open the editor.
  2. Under the Specify Orientation tab, use the Select tool's drop-down arrow to choose Origin.
  3. Mouse over the face at the narrow end of the Contact, then press c and click.
  4. Verify that the Origin coordinates round to (0 mm, 0 mm, 1 mm).
  5. Under the Edit Cross Section tab, select the Rectangle tool in the toolbar.
  6. Press Tab to specify the first point.
  7. Enter -0.5 mm as the U′ value.
  8. Enter -0.5 mm as the V′ value.
  9. Click OK.
  10. Press Tab to specify the second point.
  11. Enter 0.5 mm as the U′ value.
  12. Enter 2.7 mm as the V′ value.
  13. Click OK to close the rectangle.
  14. Select the Fillet Vertex tool in the toolbar.
  15. Select the first corner by clicking on (-0.5, -0.5, 0) in the Geometry window.
  16. Press Tab to specify the radius.
  17. Enter 0.5 mm as the Radius.
  18. Click OK to apply the bend.
  19. Select the second corner by clicking on (0.5, -0.5, 0) in the Geometry window.
  20. Press Tab to specify the radius.
  21. Enter 0.5 mm as the Radius.
  22. Click OK to apply the bend.
  23. Name the part by typing Tab into the Name field.
  24. Under the Extrude tab, enter 0.01 mm as the Extrude Distance.
  25. Click Done to save the changes to the project.

Next, bend the tab.

  1. In the Project Tree, right-click on Tab and select ModifyBend to open the editor.
  2. Under the Specify Bend tab, enter -1 as the U′ value in the Bend Axis (red) section.
  3. Enter 0 as the V′ value.
  4. Enter 0 as the W′ value.
  5. In the Normal (yellow) section, enter 0 as the U′ value.
  6. Enter 0 as the V′ value.
  7. Enter 1 as the W′ value.
  8. In the Origin section, enter 0 mm as the U′ value.
  9. Enter 1.5 mm as the V′ value.
  10. Enter 0.01 mm as the W′ value.
  11. Verify that the Centered Bend option is unchecked.
  12. Verify that the Localized, View bend region, and Apply bend options are checked.
  13. Enter -32 degrees as the Angle.
  14. Enter 1 mm as the Radius.
  15. Click Done to save the changes to the project.
  16. Right-click on Tab in the Project Tree, then select ModifyBend to open the editor.
  17. Under the Specify Bend tab, enter 0.5 mm as the V′ value in the Origin section.
  18. Enter 32 degrees as the Angle.
  19. Click Done to save the changes to the project.

Then, assign a material to the tab.

  1. Click on Copper (Pure) [ND] in the Definitions branch of the Project Tree, and drag it to the Tab in the Parts branch.

Attach the antenna to the contact.

  1. In the Project Tree, right-click on Antenna and select Set Visible.
  2. Right-click on Antenna and select ModifySpecify Orientation to open the editor.
  3. Uncheck the Construction Grid option in the middle of the editor.
  4. Use the Alignment Tools drop-down arrow to select Match Points.
  5. In the Geometry window, select the first point by clicking on the Antenna vertex positioned along the top of the antenna's blended edge (located at approximately 2.0 mm, 4.8 mm, 0.9 mm).
  6. Select the second point by clicking on the closest edge of the tab's left vertex (located at approximately -0.5 mm, 2.5 mm, 0.5 mm).
  7. Click Done to save the changes to the project.

Finally, move the antenna and contact assembly into position.

  1. Press Ctrl while clicking in the Project Tree to select the Ground Plane, Substrate, and the Ground Connection assembly, then right-click and select Set Visible.
  2. Right-click on the Antenna and Contact assembly and select ModifySpecify Orientation to open the editor.
  3. Enter 42.55 mm as the X value.
  4. Enter 118.85 mm as the Y value.
  5. Enter 0.7 mm as the Z value.
  6. Click Done to save the changes to the project.

Step 8: Add an Unmatched Feed

The feed circuitry serves as the point where the source connects to the antenna. For this tutorial, it will consist of a voltage source in series with a resistor that is added between the two pads.

  1. In the Project Tree, right-click on Circuit Components and select New Circuit Component withNew Feed Definition to open the editor.
  2. Click the Select button button next to the first endpoint's y coordinate.
  3. Press v to select only vertices.
  4. Click on the vertex along the edge of the Pad to select the first endpoint, located at (41.55 mm, 118.85 mm, 0.7 mm).
  5. Click on the adjacent vertex along the edge of the Large Pad to select the second endpoint, located at (42.05 mm, 118.85 mm, 0.7 mm).
  6. Click Done to apply the changes.
  7. In the Circuit Components branch of the Project Tree, right-click on Component [Port 1] and select Rename.
  8. Type Unmatched Feed [Port 1] into the highlighted field.
  9. Press Enter to apply the name change.

Verify that a 50 ohm Voltage Source has been added to the Circuit Component Definitions node of the Project Tree. Double-clicking on the definition will open the editor, where users can change the component's properties. The Waveform setting defaults to Automatic, which can be viewed by double-clicking in the Project Tree.

Step 9: Define the Grid

XF's gridding and meshing controls are used to discretize the CAD geometry into cell edges. This discretized representation is passed to the calculation engine, so it is important to update and define the grid before creating a simulation.

  1. In the Project Tree, double-click on the Grid node to open the editor.
  2. Double-click on Mesh to open the controls.
  3. On the left side of the Mesh controls, check the XY Plane option.
  4. In the sidebar, use the View Front button button's drop-down arrow to select View from +Z (Top).
  5. In the Mesh controls, click and drag the Z Slice sliding control all the way to the right.
  6. In the gridding editor, enter 40 as the Min Cells Per Wavelength.
  7. In the Min Feature Size section, uncheck the Ratio option to the right of the Good Conductors field.
  8. Enter 0.5 mm as the Good Conductors value.
  9. In the Cells Across section, enter 5 in the upper field.
  10. In the sidebar, use the View Top button button's drop-down arrow to select View from -X (Left).
  11. In the Mesh controls, check the YZ Plane option.
  12. Uncheck the Ratio option to the right of the Poor Conductors field.
  13. Enter 0.7 mm as the Poor Conductors value.
  14. Enter 7 in the lower Cells Across field.
  15. Click Apply to see the changes in the Geometry window.
  16. Click Done to close the editor.
  17. In the Project Tree, right-click on Substrate and select Gridding/MeshingGridding Properties to open the editor.
  18. In the Fixed Points section, check the Use Automatic Fixed Points option.
  19. Click Apply.
  20. Click Done to close the editor.
  21. In the sidebar, use the View Left button button’s drop-down arrow to select View from +Z (Top).
  22. In the Project Tree, right-click on Antenna and select Gridding/MeshingGridding Properties to open the editor.
  23. In the Grid Regions section, check the Custom Min Cells Per Wavelength option.
  24. Enter 250 as the minimum cells per wavelength.
  25. Click Apply.
  26. Click Done to close the editor.
  27. In the Project Tree, double-click on Mesh to close the controls.
  28. In the upper-left corner of XF, click View and select Parts List (All Parts) to open the editor.
  29. Press Ctrl to select the Antenna, Contact, and Tab, then right-click to choose Gridding/MeshingEnable XACT Mesh.
  30. Right-click on Substrate and select Gridding/MeshingEnable dielectric volume averaging.
  31. Close the Parts List - Parts window.

Step 10: Request Results

The last step before running a simulation is requesting results, which is done through sensors. This project utilizes two sensors: surface current and far zone. The surface current sensor records the surface current density on conductive parts at each steady-state frequency. The far zone sensor saves the antenna's far-zone radiation pattern at certain frequencies once the simulation is performed. The desired frequencies will be input when the simulation is launched.

First, create a surface current sensor.

  1. In the Project Tree, right-click on the Near Field Sensors node and select New Surface Current Sensor to open the editor.
  2. Under the Properties tab, type Surface Currents into the Name field.
  3. Use the Sensor Definition drop-down arrow to select Surface Current Sensor Definition.
  4. Verify that the Enable Surface Current Sensor option is checked.
  5. Under the Parts tab, check the Enable Part List option.
  6. Click on the Antenna in the Geometry window.
  7. Press Ctrl while clicking on the Tab.
  8. In the Project Tree, press Ctrl while selecting the Ground Plane.
  9. Under the Bounding Box tab, check the Enable Bounding Box option.
  10. Enter the first corner's X value by typing 30 mm into the field.
  11. Press Tab and enter 95 mm as the Y value.
  12. Press Tab and enter -5 mm as the Z value.
  13. Enter the second corner's X value by typing 70 mm into the field.
  14. Press Tab and enter 125 mm as the Y value.
  15. Press Tab and enter 5 mm as the Z value.
  16. Click Done to close the editor.
  17. In the Project Tree, double-click on Surface Current Sensor Definition to open the editor.
  18. Uncheck the Transient Js option.
  19. Check the Steady State Js option.
  20. Click Done to save the changes to the project.

Then, create a far zone sensor.

  1. In the Project Tree, right-click on Far Zone Sensors and select New Far Zone Sensor to open the editor.
  2. Under the Geometry tab, use the Coordinate System Type drop-down arrow to select Theta, Phi.
  3. In Theta section, verify that the Start Angle and Stop Angle are set to 0 degrees and 180 degrees, respectively.
  4. Enter 2 degrees as the Increment value.
  5. In the Phi section, verify that the Start Angle and Stop Angle are set to 0 degrees and 360 degrees, respectively.
  6. Enter 2 degrees as the Increment value.
  7. Under the Properties tab, type Far Zone - 3D into the Name field.
  8. Verify that the Enable Far Zone Sensor, Use Project Value, and Collect Steady State Data options are checked.
  9. Click Done to save the changes to the project.

Step 11: Create and Run a Simulation

Once the project is complete, it must be saved in order to create a new simulation and write output files. When creating a simulation, XF provides options for creating a parameter sweep, collecting S-parameters, and specifying the frequencies at which the surface current and far zone patterns will be saved.

First, save the project.

  1. Save the project by selecting FileSave Project As.
  2. Enter the Project Name by typing GPS-BT-Unmatched into the field.
  3. Click Save.

Then, create and run a simulation.

  1. Click the Simulations button in the upper-right corner of XF to open the Simulations window.
  2. Use the Create Simulation drop-down menu to select FDTD to open the editor.
  3. In the Create FDTD Simulation window, enter the simulation Name by typing Unmatched Antenna 20-30 mm into the field.
  4. Under the Setup Parameter Sweep tab, check the Perform Parameter Sweep option.
  5. On the left side of the tab, click the New parameter Sequence button button to add a new parameter sequence.
  6. In the left pane, select antennaLength from the available options.
  7. On the right side of the tab, use the Sweep Type drop-down menu to select Start, Incr., Count.
  8. Enter 9 as the Count value.
  9. Enter 20 mm as the Starting Value.
  10. Enter 1.25 mm as the Increment.
  11. Under the Setup S-Parameters tab, verify that the Compute S-Parameters option is checked.
  12. Verify that the Unmatched Feed is selected in the Active Port(s) pane.
  13. Under the Frequencies of Interest tab, check the Collect Steady-State Data option.
  14. Click the Add button button on the right side of the tab.
  15. Enter 1575.42 MHz as the first frequency.
  16. Click the Add button button to enter a second frequency.
  17. Enter 2.402 GHz into the highlighted field.
  18. Click Create and Queue Simulation.

Step 12: View Port Results

Once the simulation is complete, the results are available to view through the results browser. S-parameter computation was enabled when the simulation was created, so the port sensor saved data to compute S-parameters and VSWR for the unmatched feed. By exporting the results to a Touchstone file, users can view them in a circuit simulator and create a matching network. Net input power and system efficiency is also viewed.

View S-parameter results.

  1. Click the Results button on the right side of the XF window to open the Results browser.
  2. Select Unmatched Feed as the Sensor.
  3. Select Frequency as the Domain.
  4. Select S-Parameters as the Result Type.
  5. Click on the first result line in the lower portion of the window, and press Shift while clicking on the last result line to select all S-parameter results from the parameter sweep.
  6. Right-click on the selected results and select View (default) to open the graph.

Highlight the operating bands.

  1. Click the Create Region Highlight button on the right side of the toolbar to open the editor.
  2. Type GPS into the Name field.
  3. Use the drop-down arrow to select Bound X.
  4. In the X-Axis section, enter 1563 MHz as the lower value.
  5. Press Tab and enter 1587 MHz as the upper value.
  6. Click OK to apply the change.
  7. Click the Create Region Highlight button on the right side of the toolbar to open the editor.
  8. Type BT into the Name field.
  9. Use the drop-down arrow to select Bound X.
  10. In the X-Axis section, enter 2.402 GHz as the lower value.
  11. Press Tab and enter 2.480 GHz as the upper value.
  12. Click OK to apply the change.

View VSWR results.

  1. Click the Results button on the right side of the XF window to open the Results browser.
  2. Select VSWR as the Result Type.
  3. Click on the first result line in the lower portion of the window, and press Shift while clicking on the last result line to select all VSWR results from the parameter sweep.
  4. Right-click on the selected results and select View (default) to open the graph.

Export to a Touchstone file.

  1. Click the Results button on the right side of the XF window to open the Results browser.
  2. Select S-Parameters as the Result Type.
  3. In the lower portion of the window, right-click on the Run0001 result line to select the 0.02 antennaLength, and choose ExportExport to Touchstone file to open the file directory.
  4. Choose a location and name the file as desired.
  5. Click Save to save the file.

Users can load the saved file in a circuit simulator where they can design a matching network.

View system sensor results.

  1. Click the Results button on the right side of the XF window to open the Results browser.
  2. Select System as the Sensor.
  3. Select Discrete Frequencies as the Domain.
  4. In the lower portion of the window, double-click on any Run0001 result line.
  5. In the upper-left corner of XF, click Edit, then Project Properties to open the editor.
  6. Under the Display Units tab, change the Power by selecting milliwatt decibels (dBmW, dBm) from the drop-down menu.
  7. Click Done to save the changes to the project.
  8. In the table, change the Net Available Power by clicking in the GPS frequency column on the left and entering 23 dBmW.
  9. Click in the Bluetooth frequency column on the right and enter 23 dBmW.

Click outside the active Bluetooth frequency field to see the other adjusted values, then close the editor and any open windows.

Step 13: View Surface Currents

Surface current results can be viewed for each swept value in the parameter specified when creating the simulation. Users can display the data in different modes and animate the sequence to watch the fields change.

Orient the geometry to view the antenna.

  1. In the Project Tree, select the Antenna and Contact assembly.
  2. Click the Zoom to selection button in the right sidebar.

View currents on the ground plane beneath the substrate.

  1. Click the Results button on the right side of XF to open the Results browser.
  2. Select Surface Currents as the Sensor.
  3. In the lower portion of the Results browser, double-click on the result line associated with an antenna length of 21.25 mm.
  4. In the Project Tree, right-click on Substrate and select Set Invisible.

Display the field data.

  1. In the controls at the bottom of the Geometry window, change the Display Mode by selecting Vector Field from the drop-down menu.
  2. Enter 3 as the Size Factor.
  3. Click Apply to view the change in the Geometry window.
  4. Change the Display Mode by selecting Flat from the drop-down menu.
  5. Click Apply to view the change in the Geometry window.
  6. Change the Frequency by selecting 2.402 GHz from the drop-down menu.
  7. Click Apply to view the change in the Geometry window.
  8. Under the Sequence tab, enter 1 degree as the Increment.

Edit the scale bar.

  1. Right-click on the scale bar at the top of the Geometry window and select Properties to open the Scale Bar Editor.
  2. In the Limits section, uncheck Automatic Range.
  3. Enter -42 dB as the Minimum.
  4. In the Units section, uncheck Automatic.
  5. In the Colors section, double-click on the blue color in row 4 of the Color column.
  6. Use the Preset drop-down arrow to select White.
  7. Click Apply to see the change in the color bar.
  8. Click Done to close the editor.

Play the sequence.

  1. Under the Sequence tab, uncheck Compute Bounds.
  2. Click the Play the given sequence button in the lower-right corner of the Sequence tab controls.
  3. Click Unload at the top of the tab controls.

Once the surface current results are removed from the window, users can set the Substrate visible through its right-click menu in the Project Tree.

Step 14: View Far Zone Results

Far zone results can be viewed for each swept value in the parameter specified when creating the simulation. Users can display 2-D and 3-D gain patterns and view different polarizations.

View a 3-D gain pattern.

  1. Click the Results button on the right side of the XF window to open the Results browser.
  2. Select Far Zone - 3D as the Sensor.
  3. Select Gain as the Result Type.
  4. In the lower portion of the browser, double-click the result line associated with an antenna length of 21.25 mm.
  5. Click Zoom to selection in the right sidebar.

View different polarizations.

  1. Under the Setup tab of the controls, select Theta from the Viewing drop-down menu.
  2. Change the Frequency by selecting 2.402 GHz from the drop-down menu.
  3. Click Apply to update the pattern.

View the power and efficiency.

  1. Under the Statistics tab, change from Full Pattern to Open Sky using the drop-down arrow.
  2. Use the Change Output Global Opacity button in the sidebar to change the Output Opacity to 50.

Define a rotated coordinate system.

  1. Under the Coordinate System tab, right-click on Phi in the Geometry window and select Rotate by, then enter 90 degrees.
  2. Click Apply.

View the updated radiated power.

  1. Click on the Statistics tab to view the results for the rotated coordinate system.

Verify that the power and efficiencies reflect the device's performance with the rotated coordinate system.

  1. Click Unload to close the controls.

View a 2-D polar plot.

  1. Click the Results button on the right side of the XF window to open the Results browser.
  2. In the lower portion of the window, click on the first result line and then press Shift while clicking on the last result line to select all available results.
  3. Right-click on the selected results, then select Create Line Graph to open the editor.
  4. Change the Graph Type to Polar.
  5. Change the Independent Axis to Phi using the drop-down arrow.
  6. Change the Theta index to 45.
  7. Click View to display the Gain vs. Angle graph.