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"Mode Matching" method ?

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Member level 3
Jun 17, 2002
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Hi there:

I asked question about microstrip discontinuity
before, and now my question changes to

Is there any "mode-matching"software which
gives analytical solution at the discontinuty of

If yes, I also want to do the comparison between
this analytical solver and other numerical solvers, and
I will show you the results.



The results of mode-matching is generally not analytic. For example, consider a waveguide step junction, you can analyze it by expressing the fields on two side of the junction in terms of a large number of modes. You would get the coupling coefficients (numerical) between those modes. If you take only one or two on each sides, you might get some analytical formula. But that is valid under restricting conditions.

For simple discontinuity, many people have worked out analytical formula for the elements for an equivalent circuits. If it is available, (I think) it should have been built into a circuit modeler. Check ADS for for the components of your interest


According to my information, mode matching is a NUMERICAL technique in which you may find the generalized scatttering matrix for any waveguide junction, when there is no analytical solution available. The main advantage of mode matching with respect to other numerical techniques is its speed and accuracy.

Concerning a mode matching software there is one called microwave wizard at

but it produces numerical results not analytical ones.
Hope this might help.

Mode Matching method, where and when applicable, require very little computation power. Usually, the same problem require the same time running on HFSS on high end processor than a mode matching algoritm running on a 386 processor.

Historically mode matching algoritm was closed inside the acamemic world, recently two cuncurrent companies, both german, sell user friendly packages.

I want to program with mode-matching method to design wave-guide filter with optimization. Will anybody give me some references.
I have progammed with mode-matching method to design waveguide absorber.


I found also at some places a note that Mode matching method is stated as analytic. It really is in a sence that it approaches the problem in the EM domain by analytically preparing the EM solution procedure of discontinuity or related problems by solving a part of a problem in analytical domain, so ralatively speaking a very litle work is done in numeric domain on a PC.

As Sergio Mariott already pointed out, it makes computer run for a much shorter time for this kind of specialized solutions as oposed to general FEM or FDTD solvers that are targeted for arbitrary structures. You can always use these general solvers to asses your problem, it is very straight forward, using of mode matching or spectral domian requires equation manipulation to start with and a bit of programming for numerical portion.


MMT is analytical method however the solution could be very complicated (you're summing a lot of modal fields) thus numerical solution is usually needed..

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