Home / Examples / Electromagnetic Analysis [Hertz] / Example 24: Waveguide-to-Coaxial Adapter

Example 24: Waveguide-to-Coaxial Adapter

          
General

Analysis Conditions

The harmonic analysis is set as follows.

Tab

Setting Item

Settings

Mesh Tab

Frequency-Dependent Meshing

Reference Frequency: 1x1010 [Hz]

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

 

Harmonic Analysis

Sweep Type

Select [Linear Step by Division Number]

Sweep Setting

Minimum: 8×109 [Hz]

Maximum: 15x109 [Hz]

Division: 7

Sweep Setting

Select Discrete Sweep

Input

1.0 [W]

 

Model

The model is a waveguide-to-coaxial adapter. The inner conductor of coaxial cable is penetrated into the circular waveguide.

 

 

 

Body Attributes and Materials

Body Number/Type

Body Attribute Name

Material Name

7/Solid

InnerConductor

003_Ag *

8/Solid

Waveguide

000_Air(*)

9/Solid

Resin

Resin

* Available from the material DB

 

 

The material properties of Resin are set up as follows:

Material Name

Tab

Properties

DRMat

Permittivity

Relative Permittivity: 2.3

 

Boundary Conditions

Boundary Condition Name/Topology

Tab

Boundary Condition Type

Settings

Port_001/Face

 

Electric

 

Port

 

Reference Impedance: Specify

enter 50 ohms

Number of Modes

Number of Precalculated Modes: 5

Number of Modes Used in the Actual 3D Analysis: 1

  Select modes: None

Port_002/Face

Electric

Port

Reference Impedance:
[Use the characteristic impedance calculated from the port structure].

Number of Modes

Number of Precalculated Modes: 5

Number of Modes Used in the Actual 3D Analysis: 2

  Select Modes: None

Outer Boundary Condition

Electric

Electric Wall

 

 

Notes:

The number of modes used in the actual analysis is 2 for Port_002.

This is because the electromagnetic solver has two modes corresponding to the TE11 modes which are the basic mode of the cylindrical waveguide.

As shown in Figure 1, the directions of their electric field vectors are angled 90 degrees each other.

The two modes must be used in order to perform analysis taking TE mode into account. Currently, Femtet cannot control the direction of electric field of mode.

Results

The port numbers are automatically assigned by the port name and the number of modes used for analysis.

Ports have been set as follows.

 

Port_001 “Number of modes used in the actual analysis”: 1

Port_002 “Number of modes used in the actual analysis”: 2

 

Therefore, S-parameters are a 3 x 3 matrix.

 

 

 

               Fig. 1 Frequency Response of S-parameters

 

On the Results tab, click [Chart] - [SYZ Matrix]. The following will appear.

 

Port Index
1:Port_001:m1
2:Port_002:m1
3:Port_002:m2

 

 

"m1" and "m2" indicate the mode number.

See [How to Examine the Ports of Electromagnetic Analysis] for the detail.

 

 

 

Fig. 2 Distribution of Electric Field of Two Propagation Modes Corresponding to TE11 Modes

 

The first propagation constant dialog box above shows the following:

 

(This dialog box appears when you click [Chart] - [Mode Information] on the Results tab )

 

Port_002 p2m1:  9.691647e+001 +j 0.000000e+000

 

This is for Port_002:m1 of Port Index.

Note that "p" is for port and "m" is for mode in p2m1. The second "propagation constant" dialog box shows the following:

 

PORT2_002 p2m2: 9.681297e+001 +j 0.000000e+000

 

This is for Port_002:m2 of Port Index.

 

The power entered at Port_001 reaches Port_002 in these two modes.

The total power is acquired by the following equation.

Please use Excel or any other tool to calculate it. Femtet doesn't calculate this equation.

 

          (1)

 

Please also keep in mind the following point.

A TM01 mode also propagates at 12 [GHz] or higher. For better accuracy at 12 [GHz] or higher,

increase [Number of modes used in the actual 3D analysis] for Port_002 from 2 to 3.

Fig. 3 shows that TM01 can propagate.

 

 

Fig. 3 TM0-Mode Electric Field Distribution (at 12 GHz)