Home / Examples / Electromagnetic Analysis [Hertz] / Example 37: Electromagnetic Field Correction

Example 37: Electromagnetic Field Correction

General

The electromagnetic field of a minute dipole antenna is corrected by the function of [Correct errors of the electromagnetic field originated in the open boundary]

Unless specified in the list below, the default conditions will be applied.

Results will vary depending on Femtet version and the PC environment.

Analysis Condition

Item	Settings
Solver	Electromagnetic Analysis [Hertz]
Analysis Space	3D
Analysis Type	Harmonic Analysis
Unit	mm
Options	Select Correct errors of the electromagnetic field originated in the open boundary

Harmonic Analysis tab and Open Boundary tab are set as follows.

Tab	Setting Item	Settings
Harmonic Analysis	Sweep Type	Single Frequency
	Frequency	3×106 [Hz]
	Sweep Setting	Select Discrete Sweep
	Input	1.0 [W]
Open Boundary	Type	Absorbing Boundary
Open Boundary	Order of Absorbing Boundary	1st-order

Graphical Object

A minute dipole antenna consists of a perfect electric conductor ('PEC') and port, surrounded by ambient air. The 'correction' body serves as a domain for correcting electromagnetic fields, specifically set to minimize calculation time.

The air domain is surrounded by another air domain. The open boundary condition is set to the outer-most area of the analysis domain. The accuracy of the electromagnetic field near the open boundary condition is deteriorated. Therefore, for the better look, another air box is created to hide the area with low accuracy.

Whole model Antenna

Model viewed from X axis direction

Body Attributes and Materials

Body Number/Type	Body Attribute Name	Material Name
45,46,69,71,75,76/Solid	PEC	PEC
78,79,81/Sheet	AIR	AIR
80/Solid	Correction	AIR
47,70,77/Sheet	Imprinting body

* Available from the material DB

Body Number/Type	Body Attribute Name	Material Name	Mesh Size
45,46,69,71,75,76/Solid	PEC	PEC	0.5
47,70,77/Sheet		Imprinting body	0.5

Body Attribute Name	Analysis Domain
Correction	Select [Correct errors of the electromagnetic field originated in the open boundary]

Correction is executed only for the bodies with this option selected.

Boundary Condition

Boundary Condition Name/Topology	Tab	Boundary Condition Type	Settings
PORT/Face	Electric	Port	Current port
Outer Boundary Condition	Electric	Open Boundary	Select on the open boundary tab of the analysis condition setting.

Set up Mesher/Solver

Setting Item

Setting

Frequency-Dependent Meshing

Reference Frequency: 300x106 [Hz]

Select [The conductor bodies thicker than the skin depth constitute the boundary condition].

Results

You can view the results fields (such as Results tab > Field).

Go to Results tab > Display > Solver, and select [Electromagnetic waves correction field].

The field types are as follows.

Electric Field [V/m] Original	Electric field before correction. It is in the same state of electric field as when the electromagnetic solver is selected. Depending on the display method, they don't necessarily match.
Electric Field [V/m] Data for Correction	It is the electric field for correction. The larger the value, the greater the reflection on the open boundary.
Electric Field [V/m] Data after Correction	The sum of "Electric Field Original" and "Electric Field Data for Correction".
Magnetic Field [A/m] Original	It is the magnetic field before correction. It is in the same state of magnetic field as when the electromagnetic solver is selected. Depending on the display method, they don't necessarily match.
Magnetic Field [A/m] Data for Correction	It is the magnetic field for correction. The larger the value, the greater the reflection on the open boundary.
Magnetic Field [A/m] after Correction	The sum of "Magnetic Field Original" and "Magnetic Field Data for Correction".

The left figure below shows the results with the following conditions. The gradation contour diagram is displayed with bodies "AIR" and "PEC" hidden because the corrected body in this example is body "Correction" only.

Electromagnetic waves correction field	0.300000 GHz
Electric field [V/m] original	Magnitude
270°	Log

The right figure below is obtained by changing "Electric field [V/m] original" to "Electric field [V/m] after correction".

The color scale is set from 3ｘ105 [V/m] to 3x104 [V/m]. This setting makes the overall distribution easy to view.

While the lower left diagram shows the field pulled to the boundary unnaturally in the upper and lower areas of the dipole antenna, the lower right diagram shows the natural field after the correction. The influence of the boundary is not observed.

The correction has been successfully executed.

Please note that the diagrams at the top of this page are drawn with the cross sectional view and the line contour.