The Simulation Corner |
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How to model E-plane components with MEFiSTo-2D
The documentation for MEFiSTo-2D describes several applications involving H-plane waveguide components such as the H-plane Tee shown if Fig. 1 (a). The question is: is it possible to model E-plane components such as the E-plane Tee in Fig. 1 (b), and how?
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H-plane (a) and E-plane (b) waveguide tees. |
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Here is a brief instruction on how to model an E-plane Tee in a rectangular waveguide. The method applies also to any other E-Plane waveguide components in which only TE1n modes are excited. In such cases there is no electric field component parallel to the a-dimension, and all field components can be derived from the y-directed component of the magnetic field (assuming the orientation shown in Fig. 1 (b)).
Strictly speaking, these problems are 3D, but they can still be accurately solved with a 2D simulator by using the following steps:
- Orient the structure as shown in Fig. 1 (b) and use a dual representation of the fields and their boundary conditions as follows: The voltage Vy in the TLM network is used to model the magnetic field Hy in the waveguide. The wider waveguide walls are then represented by magnetic walls, and the incident field is a uniform plane wave (TEM). Note that in the drawing and in the *.tlm file, the a-dimension of the waveguide is oriented along the y-direction.
- Assume at this stage that the a-dimension is infinite so
that the fields are constant in y-direction. This limiting case
represents a true TE situation. The Draw window of MEFiSTo-2D will
look like Fig. 2. Note the reference structure for the extraction of
S-parameters. The green walls are matched boundaries for normal
TEM incidence (
= 0). Solve this problem and extract the
S-parameters vs. frequency.
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MEFiSTo-2D Draw Window |
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- Apply the following frequency transformation to these results in order to obtain the S-parameters for the same structure with a finite a-dimension:
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(1) |
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This transformation or mapping can be easily performed using an EXCEL
spreadsheet or one of the popular math packages such as MATLAB,
MATHEMATICA or MAPLE. The S-parameter data are available in the
test file *.rep that you can generate using the
Save Text Report command in the File menu of MEFiSTo-2D.
