Home / Examples / Electromagnetic Analysis [Hertz] / Example 43: Ground-Penetrating Radar

Example 43: Ground-Penetrating Radar

General

A ground-penetrating radar with an exponential TEM horn antenna is analyzed.
How the electromagnetic waves transmitted from the transmitter are received at the receiver can be viewed by the output voltage and result field.
The detection of foreign matter is verified by comparing the results obtained with and without the presence of foreign matter, based on the received voltage.
Unless specified in the list below, the default conditions will be applied.

Electromagnetic-transient analysis is available in an optional package.

Analysis Space

Item	Settings
Analysis Space	3D
Model Unit	m

Analysis Condition

This model requires tracing the propagation of electromagnetic waves over multiple wavelengths, which results in a large analysis size. So the 1st-order elements are used to reduce calculation time.

Item

Settings

Solver

Electromagnetic Analysis [Hertz]

Analysis Type

Transient Analysis

Select Input at each port

Tab	Setting Item	Settings
Mesh	General Mesh Size	0.05 [m]
	Element Type	1st-order Element
	Frequency-Dependent Meshing	Select The conductor bodies thicker than the skin depth constitute the boundary condition Select Determine the reference frequency automatically from the input waveform
Transient analysis	Waveform Type	Broadband Pulse Minimum Frequency: 0.5 [Hz] Maximum Frequency: 1.0 [Hz]
	Finish time of calculation	2.0×10-8 [s]
	Output Field *1	Select Output Field Output Interval for Field: 1

*1 If you want to reduce the result size, increase the Output Interval for Field or deselect Output Field.
If the fields are not output, only the table values are output.

Model

The model consists of an exponential TEM horn antenna (Horn1 and Horn2), which is a transmitting and receiving antenna, a reflecting object (Reflector) with an electric wall which is intended to avoid noise due to direct wave reception and diffraction,

an air domain (Air), soil, and a conductive pipe (Pipe) as a foreign body.

Body Attributes and Materials

Body Number/Type	Body Attribute Name	Material Name
0, 1/Sheet	Horn1	001_Al *
2, 3/Sheet	Horn2	001_Al *
4/Solid	Air	000_Air *
6/Solid	Pipe	008_Cu (*)
10/Solid	Soil	Soil

* Available from the material DB

The material properties of Soil are set up as follows.

Material Name

Tab

Properties

Soil

Permittivity

Relative Permittivity: 2.0

Conductivity

Conductor

Conductivity: 1.0×10-3 [S/m]

Boundary Condition

Boundary Condition Name/Topology	Tab	Boundary Condition Type	Setting
Port1/Face	Electric	Port	Reference Impedance: 50Ω Integral Path: Set Path1
Port2/Face	Electric	Port	Reference Impedance: 50Ω Integral Path: Set Path1
Reflector/Face	Electric	Electric Wall
Outer Boundary Condition	Electric	Open Boundary

Results

The transient analysis result of the output voltage is shown by red line.

For comparison, the result of analysis without foreign body (WithoutPipe) is shown by black line. As the graph shows, the analysis with a foreign body has a large signal reception

at around 10ns. It indicates that the electromagnetic waves from the transmitting antenna (Port1) are reflected by the conductive pipe and propagate to the receiving antenna (Port2).

The figures below are electric field contours of the XY cross section. From these figures too, it can be viewed how the electromagnetic waves from the transmitting antenna are reflected by the conductive pipe and propagate to the receiving antenna.

For clear comparison, the maximum value of the electric field is fixed at 0.5 [V/m] in the graphics setup.

Time [s]	Electric Field Contour
2 ns
4 ns
5 ns
6ns
7 ns
8ns
9ns
10 ns