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Example23Mixed-Mode S-Parameters Analysis of Balanced Line

General

• The characteristics of a balanced line are analyzed.

• The mixed-mode S-parameters are solved.

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

Analysis Space

 Item Setting Analysis Space 3D Modelunit mm

Analysis Conditions

 Item Setting Solver Electromagnetic Analysis [Hertz] Analysis Type Harmonic analysis Options for Electromagnetic Analysis Select Propagation mode transformation.

Mesh, harmonic analysis, and open boundary are set as follows.

 Tab Setting Item Setting Mesh Frequency-Dependent Meshing Reference frequency: 1×10^10[Hz] Select “The conductor bodies thicker than the skin depth constitute the boundary condition.” Harmonic Analysis Frequency Minimum: 0.1×10^9[Hz] Maximum: 5×10^9[Hz] Sweep Type Select Linear step by division number. Division number: 10 Sweep Setting Select discrete sweep Input 1.0[W] Open Boundary Type Absorbing boundary Order of Absorbing Boundary 1st degree

Graphical Objects

Two electrodes are created on a substrate. They function as a balanced line.

They are covered with rectangle air space.

Air and ports at both ends of the substrate are set as in the diagram below.
Set two integral paths (PATH1 and PATH2) connecting two electrodes and the bottom of the substrate.
The bottom of the substrate contacts the electric wall outer boundary condition.

Body Attributes and Materials

 Body Number/Type Body Attribute Name Material Name 0/Solid SUBSTRATE 006_Glass_epoxy * 1/Solid AIR 000_Air(*) 2/Solid LINE 003_Ag * 3/Solid LINE 003_Ag * 5/Sheet Imprinting body 6/Sheet Imprinting body

(*) Available from the Material DB

Boundary Conditions

 Boundary Condition Name/Topology Tab Boundary Condition Type Setting Port_001/Face Electric I/O Port Integral Path: Set PATH1 and PATH2 as shown in the diagram above. Set PATH1 and PATH2 for differential pair. *1 Reference Impedance: Select Specify Select Differential impedance *2 100 [Ω] Number of Modes number of precalculated modes: 5 number of modes used in the 3D analysis: select Automatic setting. Port_002/Face Electric I/O Port Same as above. Outer Boundary Condition Electric Electric wall

*1) Click [Differential pair] button while selecting PATH1 and PATH2.
The integral path in the same differential pair will be given the same number like “1” following the integral path name.

*2) Differential impedance can be selected if the differential pair is set.

Results

1. Propagation Mode

Select Port for [Analysis type]. From [Mode], select 5GHz which is the maximum analysis frequency.
As the number of modes to precalculate is set to 5,
five propagation modes are calculated for one frequency.
The diagram below shows the electric fields of five propagation modes calculated at PORT1 with 5GHz.

A part of the Propagation constant dialog box is also shown at the bottom of each picture in the diagram below.
Propagation constant dialog box can be opened from Mode Information of the [Chart] button.

 Mode Differential Mode Analysis 50: 5.000000e+09Hz: (0) PORT1 p1m1 51: 5.000000e+09Hz: (1) PORT1 p1m2 52: 5.000000e+09Hz: (2) PORT1 Not used 53: 5.000000e+09Hz: (3) PORT1 Not used 54: 5.000000e+09Hz: (4) PORT1 Not used

You can tell that the differential mode is calculated first, and then the common mode is calculated at PORT1.
The third mode is not used in the 3D analysis as the Propagation constant dialog box shows “Not used”.

Please confirm that the differential and common modes are used in the 3D analysis also at PORT2.

2. S-Parameters

Click [SYZ Matrix] of the [Chart] button. SYZ Matrix dialog box will show up.
Select your desired component and click the [XY Graph] button.
Mixed-mode S-parameters graph will appear as in the diagram below.

As shown in the Port Index of the SYZ Matrix dialog box, suffixes of S-parameters indicate the ports as follows.

 Number Port: Mode 1 PORT1:DIFF(PATH1,PATH2) 2 PORT1:COM(PATH1,PATH2) 3 PORT2:DIFF(PATH1,PATH2) 4 PORT2:COM(PATH1,PATH2)

“DIFF” means differential mode and “COM” means common mode.

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