Filter Synthesis tool: coupled microstrip filter strange design

[PieroTognolatti]

I noticed that the Filter Synthesis tool of uSimmics 5.8 designs a coupled-microstrip filter with Chebyshev response and even order that requires a load impedance different from the source impedance.  Why? In any microwave filter book you can find the recipe for a filter that, even in the case of an even-order Chebyshev, is always symmetric. Look at the following screenshots or run the package you can find attached.

Regards

Piero

 

Attachments:

1. Compare-filter-design.qucs

[PieroTognolatti]

Running the package I have attached you can also find a schematic where you find all the relevant equations of my design.

[QucsStudio]

Yes, you are right! That’s not as it should be. Thanks a lot for reporting it. It will be fixed in the coming release.

It came from the lowpass filter design, but for bandpass filters it’s indeed unnecessary.

[Author]

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