Super detailed teaching you how to use HFSS to design and simulate inverted F antenna 2

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Super detailed teaching you how to use HFSS to design and simulate inverted F antenna 2 [Copy link]

HFSS simulation design process

New construction design project

1) Open ANSYS Electronics Desktop 2019 R2. A project Project1 is created by default. Right-click Project1, save and enter the project name IFA_20200212, select the folder, and save.

Click HFSS, and the HFSS working interface pops up:

(2) Set the solution type

Select HFSS-->Solution Type from the main menu to open the following dialog box. Select the terminal driven solution type Terminal and click OK.

(3) Set the model length unit to mm

Select Modeler-->Units from the main menu bar to open the settings window:

Adding and defining design variables

Select HFSS-->Design Properties from the main menu bar to open the Design Properties dialog box. Click the Add button in the dialog box to open the Add Property dialog box and add variables in sequence:

IFA Antenna Design Modeling

Set the system's coordinate origin to the center of the top of the ground plate.

Both the ground plane and the antenna radiator are set as ideal thin conductors regardless of thickness.

First, create a ground plate on the xoy plane with a length and width of variables GndY and GndX, and set its boundary conditions to ideal conductor boundaries to simulate the characteristics of ideal conductors.

Then create a dielectric layer with a material of FR4 and a thickness of SubH just above the ground plane.

Finally, an inverted-F antenna is created on the upper surface of the dielectric layer (i.e., the plane where z is equal to the variable SubH).

(1) Create a ground plane

Create a rectangular surface on the xoy plane with one vertex at (-GndX/2, -GndY, 0), and its length and width are GndY and GndX respectively. After the rectangular surface model is built, set its boundary condition to an ideal conductor boundary.

Select Draw-->Rectangle command from the main menu or click the button on the toolbar to enter the state of creating a rectangular surface, and then create a rectangular surface of any size on the xy surface of the 3D model window.

The newly created rectangular surface will be added to the sheets node in the operation history tree. Its default name is Rectangle1. Double-click the Rectangle1 option under sheets in the operation history tree to open the Attribute tab of the new rectangular surface properties dialog box. Enter GND in the Name text box, set the color to copper yellow, and click OK.

Expand the GND node under the Operation History tree, double-click the GreatRectangle option under the node, open the Command tab of the New Rectangle Face Properties dialog box, and set the vertex coordinates and size of the rectangle face in the tab.

Enter the vertex coordinates (-GndX/2, -GndY, 0) in the Position text box, enter the width and length GndX and GndY in the XSize and Ysize text boxes respectively, and click OK.

Press Ctrl+D to display the created object model in full screen:

Select the reference ground model in the 3D model window, then right-click and select Assign Boundary-->Perfect E in the pop-up shortcut menu to open the Ideal Conductor Boundary Setting dialog box. Change the default Name of PerfE1 to PerfE_GND and click OK.

(2) Create a dielectric layer

Create a rectangular model to represent the dielectric layer. The model is located directly above the ground plane, that is, the ground of the model is located on the xoy plane, the model medium is FR4, and the model is named Substrate.

Select Draw-->Box from the main menu bar, or click the button on the toolbar to create a cuboid of any size, name it Box1, double-click Box1 under the Solids node, change the name to Substrate, set the Value corresponding to the Material option to FR4_epoxy, set its material to FR4_epoxy, then set the color to dark green, set the transparency to 0.6, and click OK.

Double-click the CreateBox option under the Substrate node in the operation history tree to open the properties dialog box. Set the vertex coordinates and size of the cuboid as shown below and click OK.

Ctrl+D Preview

(3) Create an inverted F antenna model

Create a radiation patch model of the inverted F antenna, which is located on the upper surface of the dielectric layer and grounded through an ideal conductor rectangular surface. The shape of the antenna radiation patch is shown in the figure:

A. Create a rectangular surface 1, named FeedLine, with length H and width W respectively:

B. Create a rectangular surface 2, named Gndstub1, with a length of H and a width of W:

C. Create a rectangular surface 3, named Gnd_stub2, with a length of S+2*W and a width of W respectively.

D. Create rectangular surface 4 and name it Antenna. Its length and width are L and W respectively.

E. Create rectangular surface 5 and name it as the xz plane. Click the

drop-down list box on the toolbar and select XZ.

Create the plane and name it Gnd_via, with a length of SubH and a width of W.

F. Merge the rectangular faces to generate a complete inverted-F antenna.

Hold down the Ctrl key and click Antenna, FeedLine, Gnd_stub1, Gnd_stub2 and Gnd_Via under the sheets in the operation history tree, then select Modeler-->Boolean-->Unite command from the main menu bar, or click the button on the toolbar to perform the merge operation. The name of the new object generated by the merge is Antenna.

G. Set the boundary conditions of the inverted-F antenna model, select the Antenna option under sheets, right-click, select Assign Boundary-->Perfect E command, change the name to PerfE_Antenna, OK.

4) Set the excitation port

Because the input port of the antenna is located inside the model, lumped port excitation is required.

Create a rectangular surface parallel to the xz plane between the bottom end of the antenna's feed line (i.e., rectangular surface FeedLine) and the ground plate, and use it as the excitation port surface of the antenna, as shown in rectangular surface 6 in the figure, and then set the excitation mode of the excitation port surface to lumped port excitation.

Make sure the work plane is in the xz plane, create a rectangular surface and name it Feed_Port:

Set the excitation, click Feed_Port under sheets in the operation history tree, select the rectangular surface, then right-click the mouse, Assign-->Lumped Port command, and open the lumped port setting dialog box under the terminal driven solution type.

The Port Name option defaults to 1. The Conductor option below sets the port reference ground. Here, select the GND checkbox. Click OK to complete the setting of the lumped port excitation. After completion, the set lumped port name 1 will be automatically added to the project tree under Excitations. 1 is the lumped port excitation name, and Antenna_T1 is the terminal line name:

Double-click the port excitation name 1 under the Excitations node to open the Lumped Port dialog box and confirm that the port impedance is 50Ω. Double-click the terminal line name Antenna_T1 to open the Terminal dialog box. The name can be changed to T1 and confirm that its normalized impedance is also 50Ω.

(5) Create and set radiation boundaries

When using HFSS to analyze antenna problems, radiation boundary conditions must be set, and the distance between the radiating surface and the antenna must be no less than 1/4 of the operating wavelength.

In this design, the surface of a rectangular model is set as the radiation surface, and the distance between the radiation surface and the inverted F antenna model is 1/2 working wavelength.

First, create a rectangular model AirBox. The distance between each surface of the rectangular model and the surface of the dielectric layer Substrate is 1/2 working wavelength. Then set all surfaces of the rectangular model as radiation boundary conditions.

Set the current working plane to xy, create a Box and name it AirBox:

After the rectangular model AirBox is created, right-click the AirBox option under the Solids node in the operation history tree, select the Assign Boundary-->Radiation command, open the dialog box, keep the default settings unchanged, and click OK to set the surface of the rectangular model as the radiation boundary condition.

After the settings are completed, the default name of the radiation boundary condition Rad1 is automatically added to the Boundaries node in the project tree.

(6) Solution settings

The designed inverted F antenna works at 2.4GHz with a center frequency of 2.45GHz, so the solution frequency can be set to 2.45GHz. At the same time, add a 1.8G-3.2GHz sweep setting, select the interpolating sweep type, and analyze the antenna's return loss and input impedance in the 1.8-3.2GHz frequency band.

A. Solution frequency and mesh analysis settings

Right-click the Analysis node under the project tree, select Add Solution Setup-->Advanced command in the pop-up shortcut menu, open the dialog box, and set as follows:

B. Frequency sweep settings, expand Setup1 under Analysis, right-click, select Add Frequency Sweep command, open the Edit Sweep dialog box, and set as follows:

OK

(7) Design check and run simulation calculation

HFSS-->Validation Check

Right-click Analysis and select Analysis All to start the simulation calculation.

(8) Check antenna performance parameters

After the simulation analysis is completed, the various performance parameters of the antenna can be viewed in the data post-processing section.

A. By looking at the antenna's return loss (S11), you can see the antenna's resonant frequency. Right-click the Result node in the project tree, select Create Terminal Solution Data Report-->Rectangular Plot in the pop-up shortcut menu, and open the report dialog box:

Verify that Setup1:Sweep is selected in the Solution option on the left side of the dialog box, select Terminal S Parameter in the Gategory list box, select St(Antenna_T1, Antenna_T1) in the Quantity list box, and select dB in the Function list box.

Then click New Report, and then click Close to generate the following S11 analysis results:

Right click to add a mark point:

From the result report, we can see that the antenna resonant frequency is 2.45GHz and the 10dB bandwidth is about 400MHz. At 2.45GHz, S11=-35.2655.

B. Check the input impedance of the antenna

Check the relationship between the input impedance of the antenna and the frequency in the rectangular coordinate system and the Smith original diagram.

Right-click the Result node under the project tree and select Create Terminal Solution Data Report-->Rectangular Polt in the pop-up shortcut menu to open the report setup dialog box. Select Setup1: Sweep for Solution, select Terminal Z Parameter in the Category list, select Zt (Antenna_T1, Antenna_T1) for Quantity, and select im and re in Function, which means to view the imaginary part (reactance part) and real part (resistance part) of the input impedance at the same time.

Then click New Report, and then click Close to generate a report of the antenna input impedance results:

Add mark point

It can be seen from the report that at the center frequency of 2.45GHz, the input impedance of the antenna is (51.5622+j0.7925)Ω, which shows that the input impedance of the antenna is well matched with 50Ω at this time.

Right-click Result again, Create Terminal Solution Data Report-->Smith Chart to open the setup dialog box, select Setup1: Sweep for Solution, select Terminal S Parameter in the Category list, select St (Antenna_T1, Antenna_T1) for Quantity, and select none for Function.

Then click New Report, and then click Close to generate the antenna input impedance result report displayed on the Smith chart.

It can be seen from the report that at the center frequency of 2.45 GHz, the normalized input impedance of the antenna is (1.0312+j0.0159) Ω.

C. Check the antenna's directivity pattern

Here we can view the 3D gain pattern of the antenna. The antenna pattern is determined in the far field. When viewing the far field analysis results of the antenna, we first need to define the radiation surface.

Right-click the Radiation node in the project tree, select Insert Far Field Setup-->Infinite Sphere in the pop-up shortcut menu, open the Far Field Radiation Sphere Setup dialog box, and define the radiation surface:

Click OK to define a radiating surface named Infinite Sphere 3D and add it to Radiation.

View the three-dimensional gain pattern: right-click the Result node in the project tree, select Create Far Fields Report --> 3D Polar Plot in the pop-up shortcut menu, open the settings dialog box, select Infinite Sphere 3D in Geometry, select Gain in the Category list, select GainTotal in Quantity, and select dB in Function.

Then click New Report, and then click Close to generate the three-dimensional gain pattern of the inverted F antenna: