Home / Examples / Electromagnetic Analysis [Hertz] / Example 21: Waveguide Analysis of Differential Lines

Example 21: Waveguide Analysis of Differential Lines

General

 

 

 

 

Analysis Space

Item

Settings

Analysis Space

2D

Model Uit

mm

 

Analysis Conditions

Item

Settings

Solver

Electromagnetic Analysis [Hertz]

Analysis Type

Waveguide Analysis

 

Mesh tab, Harmonic analysis tab and Open boundary tab are set as follows.

Tab

Setting Item

Settings

 

Meshing Setup

Deselect Automatically set the general mesh size *

General Mesh Size 0.2 [mm]

Mesh Tab

Frequency-Dependent Meshing

Reference Frequency: 1x109 [Hz]

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

Waveguide Analysis

Sweep Type

Select [Linear Step by Division Number]

Sweep Setting

Minimum: 1×109 [Hz]

Maximum: 1x109 [Hz]

Division: 0

Maximum Number of Propagation Modes

2

* The general mesh size is a bit too large in this example. Smaller mesh size is set.

Model

Two electrodes are created on a substrate. They function as differential lines.
Rectangle air space (AIR) is defined to cover them.

Setting place of the wire body for integral path (PATH) depends on the mode to analyze.
For the differential mode analysis, place the wire body between the electrodes as in the diagram A.
For the common mode analysis, place the wire body between one of the electrodes and the ground as in the diagram B.

Body Attributes and Materials

Body Number/Type

Body Attribute Name

Material Name

0/Sheet

SUBSTRATE

006_Glass_epoxy *

1/Sheet

ELECTRODE

008_Cu *

2/Sheet

ELECTRODE

008_Cu *

3/Sheet

AIR

000_Air(*)

4/Wire

 

 

* Available from the material DB

Boundary Conditions

Boundary Condition Name/Topology

Tab

Boundary Condition Type

Outer Boundary Condition

Electric

Electric Wall

PATH

Electric

Integral Path

 

Results

1. Propagation Mode

As the maximum number of the propagation modes is set to 2 in the analysis condition,
two propagation modes are calculated for one frequency.

Regardless of the integral path location, electric fields of two modes are as follows
From the distributions of the electric fields, you can tell that the first mode is the common mode and the second mode is the differential mode.

Mode

Electric Field

0: 1.000000e+09 [Hz](0)

1: 1.000000e+09 [Hz](1)

2. Characteristic Impedance

On the Characteristic impedance (Zpv) [ohm] tab in Table, you can check the characteristic impedance.
The following diagram shows the characteristic impedance obtained for the models with integral path locations A and B above.
Be aware that the characteristic impedances of the common and the differential modes calculated with
the integral path A for the differential mode and the integral B for the common mode, respectively, are not accurate.

Mode

Integral Path Location A

Integral Path Location B

0: 1.000000e+09 [Hz](0) (Common mode)

1.307 Ω

(inaccurate)

60.754 Ω

1: 1.000000e+09[ Hz](1) (Differential mode)

93.237 Ω

23.196 Ω

(inaccurate)
3. Propagation Constant

Unlike characteristic impedance, propagation constant is not affected by the location of integral path.

Propagation constant tab in Table, you can check the propagation constant as follows.
Regardless of the integral path location, the same values are calculated.

Mode

Integral Path Location A

Integral Path Location B

0: 1.000000e+09[Hz](0) (Common mode)

Attenuation Constant: 0.236 Np/m
Phase Constant: 36.793 rad/m

Attenuation Constant: 0.239 Np/]
Phase Constant: 36.814 rad/m

1: 1.000000E+09 Hz](1)  (Differential Mode)

Attenuation Constant: 0.408 Np/m
Phase Constant: 33.423 rad/m

Attenuation Constant: 0.424 Np/m
Phase Constant: 33.474 rad/m