COMSOL 6.4 - Car Windshield Antenna Effect on a Cable Harness

Car Windshield Antenna Effect on a Cable Harness

This example simulates an FM antenna printed on the rear windshield of a vehicle. The simulation computes the far-field radiation pattern of the antenna and the electric fields on an interior cable harness.

Figure 1: A simplified car model consisting of a metallic body, lossy tires, tire rims, thin dielectric windshields, a printed antenna, and a cable harness connected to electronic component enclosures. The surrounding air domain and ground plane are not included in this figure.

Model Definition

Modeling begins by importing the geometry that describes a car body, cable harness, and a windshield FM antenna (Figure 1). Interior objects inside the car are not included. All metal parts are modeled as perfect electric conductors (PEC), which include the car body, a printed antenna on the rear windshield, tire rims, a cable harness connected to electronic component enclosures, and the ground plane. The tire domains are modeled as a lossy medium, using a loss tangent constitutive relation. Except for the ground plane, the car is surrounded by an air domain, which is enclosed by perfectly matched layers (PML). The 1 cm thick windshield is considered transparent and very thin in the FM frequency range. It is configured using the Transition boundary condition.

To calculate the Far-field radiation pattern over the ground plane (which is simplified as a PEC surface) and create an image of a radiating source, a symmetry condition in the Far-field Calculation Boundary settings is applied.

The antenna is excited by a lumped port with a 50 ohm reference impedance.

Results and Discussion

In Figure 2, the default electric field norm is visualized on the ground plane.

Figure 2: The electric field is nonuniformly illuminated over the ground, which contributes to the distorted radiation pattern of the antenna.

A 3D far-field radiation pattern is shown in Figure 3. Due to the shape and placement of the antenna, the overall shape of the radiation pattern is asymmetric.

Figure 3: 3D far-field radiation pattern of the printed antenna.

Figure 4 shows the electric field norm over the cable harness surface as well as which part of the cable is more affected by the antenna radiation.

Figure 4: The cable harness that is closer to the right-side tires is more exposed to the antenna radiation.

RF_Module/EMI_EMC_Applications/car_emiemc

Modeling Instructions

From the menu, choose .

New

In the window, click

Model Wizard

In the window, click

In the tree, select > .

Click .

Click

In the tree, select > .

Click

Study 1

Step 1: Frequency Domain

Define the study frequency ahead of performing any frequency-dependent operation such as building mesh. The physics-controlled mesh uses the specified frequency value.

In the window, under click .

In the window for , locate the section.

In the text field, type 80[MHz].

Geometry 1

Import 1 (imp1)

In the toolbar, click

In the window for , locate the section.

Click

Browse to the model’s Application Libraries folder and double-click the file car_emiemc.mphbin.

Click

Click the

button in the toolbar.

Sphere 1 (sph1)

In the toolbar, click

In the window for , locate the section.

In the text field, type 4.

Click to expand the section. In the table, enter the following settings:


Layer name	Thickness (m)
Layer 1	0.5

Block 1 (blk1)

In the toolbar, click

In the window for , locate the section.

In the text field, type 8.

In the text field, type 4.

Locate the section. From the list, choose .

In the text field, type -2.

Difference 1 (dif1)

In the toolbar, click

and choose .

Select the object only.

In the window for , locate the section.

Click to select the

toggle button for .

Select the object only.

Click

Ignore Vertices 1 (igv1)

In the toolbar, click

and choose .

In the window for , locate the section.

Click the

button for .

In the dialog, type 110 111 117 118 190 191 in the text field.

Click .

This removes some vertices generating unnecessary finer mesh elements.

In the toolbar, click

Disable the analysis of the geometry as the remaining small geometric details can be kept.

In the window, click .

In the window for , locate the section.

Clear the checkbox.

In the toolbar, click

Definitions

Create a set of selections before setting up the physics.

Windshield

In the toolbar, click

In the window for , type Windshield in the text field.

Locate the section. From the list, choose .

Click

In the dialog, type 66-67, 104-107, 127-128, 169-170, 191-196, 202 in the text field.

Click .

Tire

In the toolbar, click

In the window for , type Tire in the text field.

Select Domains 5, 6, 18, and 19 only.

Harness

In the toolbar, click

In the window for , type Harness in the text field.

Select Domains 7–12 and 15–17 only.

Perfectly Matched Layer 1 (pml1)

In the toolbar, click

Select Domains 1, 2, 13, and 14 only.

In the window for , locate the section.

From the list, choose .

Electromagnetic Waves, Frequency Domain (emw)

Perfect Electric Conductor 2

In the toolbar, click

and choose .

In the window for , locate the section.

Click

In the dialog, type 9-31, 45-46, 54-60, 88-89, 95-96, 98-103, 108-111, 121-126, 145-155, 172-173, 177-178, 181-182, 185-188, 198-200, 203-206, 208-219 in the text field.

Click .

Perfect Electric Conductor 3

In the toolbar, click

and choose .

In the window for , locate the section.

Click

In the dialog, type 44, 47, 171, 174 in the text field.

Click .

Perfect Electric Conductor 4

In the toolbar, click

and choose .

In the window for , locate the section.

Click

In the dialog, type 189-190, 197, 207 in the text field.

Click .

Perfect Electric Conductor 5

In the toolbar, click

and choose .

In the window for , locate the section.

From the list, choose .

Transition Boundary Condition 1

In the toolbar, click

and choose .

In the window for , locate the section.

From the list, choose .

Wave Equation, Electric 2

In the toolbar, click

and choose .

In the window for , locate the section.

From the list, choose .

Locate the section. From the list, choose .

Lumped Port 1

In the toolbar, click

and choose .

Select Boundary 201 only.

For the first port, wave excitation is by default.

Far-Field Domain 1

In the toolbar, click

and choose .

Far-Field Calculation 1

In the window, expand the node, then click .

In the window for , locate the section.

Select the checkbox.

From the list, choose .

Materials

Material 1 (mat1)

In the window, under right-click and choose .

In the window for , locate the section.

In the table, enter the following settings:


Property	Variable	Value	Unit	Property group
Relative permittivity	epsilonr_iso ; epsilonrii = epsilonr_iso, epsilonrij = 0	1	1	Basic
Relative permeability	mur_iso ; murii = mur_iso, murij = 0	1	1	Basic
Electric conductivity	sigma_iso ; sigmaii = sigma_iso, sigmaij = 0	0	S/m	Basic

Material 2 (mat2)

Right-click and choose .

In the window for , locate the section.

From the list, choose .

Locate the section. In the table, enter the following settings:


Property	Variable	Value	Unit	Property group
Relative permittivity (real part)	epsilonPrim_iso ; epsilonPrimii = epsilonPrim_iso, epsilonPrimij = 0	2	1	Loss tangent, loss angle
Loss tangent, loss angle	delta	0.00005	rad	Loss tangent, loss angle
Relative permeability	mur_iso ; murii = mur_iso, murij = 0	1	1	Basic

Material 3 (mat3)

Right-click and choose .

In the window for , locate the section.

From the list, choose .

Locate the section. In the table, enter the following settings:


Property	Variable	Value	Unit	Property group
Relative permittivity	epsilonr_iso ; epsilonrii = epsilonr_iso, epsilonrij = 0	4	1	Basic
Relative permeability	mur_iso ; murii = mur_iso, murij = 0	1	1	Basic
Electric conductivity	sigma_iso ; sigmaii = sigma_iso, sigmaij = 0	0	S/m	Basic