COMSOL 6.3 - Modeling of Dipole Antenna Array Using the Boundary Element Method

Modeling of Dipole Antenna Array Using the Boundary Element Method

This example of a dipole antenna array demonstrates a cost-effective analysis using the Boundary Element Method (BEM). When dealing with a large array made of metallic radiators, the Finite Element Method (FEM) would necessitate greater computational resources. The simulation results depict the radiation patterns of a 12-by-1 array, consisting of metallic half-wave dipole antennas resonant at 1 GHz.

Figure 1: 12-by-1 half-wave dipole antenna array.

Model Definition

The model begins by constructing a single metallic half-wave dipole antenna. The radiator of this antenna has a rectangular rod shape, and an impedance boundary condition is applied to account for losses due to the finite conductivity of copper. Given that the simulation frequency is set at 1 GHz, these losses are negligible. A lumped port is placed at the center of the antenna to excite the radiator and to compute antenna parameters, such as input impedance and S-parameter. The antenna’s length is not exactly half the wavelength of the given frequency; instead, it is slightly reduced to achieve better impedance matching with the reference characteristic impedance of 50 ohms. A far-field calculation boundary condition is enforced on the external boundaries for the near-field to far-field transformation.

After analyzing the single antenna, the original geometry is extended to form a 12-by-1 antenna array. Extra lumped ports are integrated to activate all 12 antenna components. The configurations for other boundary conditions are then automatically adjusted based on the updated 12-by-1 antenna array geometry.

Results and Discussion

Figure 2 displays the updated default plot with the modified Grid dataset for visualizing the norm of electric fields outside the antenna radiator. Adjustments have also been made to the manual color range and color table to more clearly depict the resonant near-field surrounding the single dipole antenna.

Figure 2: The norm of electric field around the single dipole antenna.

The polar-formatted E- and H-plane patterns are shown in the Figure 3. The E-plane is defined with a plane in which the dominant antenna polarization is included while the H-plane is perpendicular to the antenna polarization.

Figure 3: E-plane (blue) and H-plane (green) radiation patterns.

Figure 4 displays the 3D far-field pattern, illustrating a typical dipole antenna radiation pattern: an omni-directional pattern around the radiator with nulls in the direction of each pole.

For the 12-by-1 dipole antenna array, the analysis of the computed results repeats that of the single dipole antenna, covering aspects such as the norm of the electric field surrounding the antenna structure, the polar-formatted patterns for both the E- and H-planes, and 3D far-field pattern.

Figure 5 depicts the norm of the electric field for the antenna array, and Figure 6 visualizes the radiation patterns in the E- and H-planes, respectively.

Figure 4: The 3D far-field radiation pattern of the single dipole antenna.

Figure 5: The norm of electric field for 12-by-1 dipole antenna array.

Figure 6: E-plane (blue) and H-plane (green) radiation patterns of the 12-by-1 dipole antenna array.

Figure 7: The 3D far-field realized gain pattern of the 12-by-1 dipole antenna array.

Figure 8: H-plane pattern analysis using graph markers.

Figure 7 displays the realized gain pattern on a dB scale. Owing to the orientation of the array geometry, a directive radiation pattern emerges along the z-axis, with a notably sharp beam width relative to the y-axis.

Radiation patterns can be depicted not only in polar plot groups but also in 1D plot groups. For the latter, graph marker subfeatures are useful for swiftly analyzing maximum, minimum, and bandwidth values. Figure 8 highlights the half-power beam width, as well as the maximum values of the main lobe and the first sidelobe, within the H-plane pattern.

Notes About the COMSOL Implementation

For this type of metallic antenna simulation using the BEM, it is required to set the domain selection for the Electromagnetic Waves, Boundary Elements interface to All voids.

RF_Module/Antenna_Arrays/dipole_antenna_array

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

Geometry 1

In the window, under click .

In the window for , locate the section.

From the list, choose .

Block 1 (blk1)

In the toolbar, click

First, build a single dipole antenna geometry.

In the window for , locate the section.

In the text field, type 135.

In the text field, type 5.

Locate the section. From the list, choose .

Block 2 (blk2)

Right-click and choose .

In the window for , locate the section.

In the text field, type 5.

Click

Electromagnetic Waves, Boundary Elements (embe)

In the window, under click .

In the window for , locate the section.

From the list, choose .

Lumped Port 1

In the toolbar, click

and choose .

Add a at the center of the antenna structure.

Click the

button in the toolbar.

Select Boundaries 7–10 only.

In the window for , locate the section.

In the hport text field, type 5[mm].

In the wport text field, type 20[mm].

Specify the ah vector as


1	x
0	y
0	z

From the list, choose .

Add a lossy conducting boundary condition.

Impedance Boundary Condition 1

In the toolbar, click

and choose .

Select Boundaries 1–5 and 12–16 only.

Define the area where the near-field to far-field transformation should be performed for radiation pattern analyses.

Far-Field Calculation 1

In the toolbar, click

and choose .

Materials

Material 1 (mat1)

In the window, under 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	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