Filter Synthesis tool: coupled microstrip filter strange design

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  • 28. November 2025 at 11:22 #9154
    PieroTognolatti
    Participant

      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
      28. November 2025 at 11:24 #9156
      PieroTognolatti
      Participant

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

        29. November 2025 at 19:02 #9157
        QucsStudio
        Keymaster

          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.

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