L-band microstrip filter

[psoltan]

I'm trying to use the Filter Synthesis tool to create a a quarter-wave microstrip filter on FR4 dielectric (er=4.5, h=1.6mm, t=35um). The Qucs Filter screen says it successfully calculated a filter and put it in the clipboard. When I paste it, the microstrip dimensions are all NAN and the dielectric parameters for the substrate are all wrong.
I'm running on Linux Mint (although I had the same problem on Windows). I've compiled Qucs-s 25.2 from source.
Is that feature broken or am I doing something wrong?

Thanks,
Phil

[ra3xdh]

It is a bug. Something is wrong with substrate Er combo box. Try to put er=4.50 instead of er=4.5 in the input field and filter synthesis will work.

[psoltan]

Yep. Now it works. Thanks!

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On Mon, Nov 3, 2025 at 8:33 AM Vadim Kuznetsov ***@***.***> wrote: It is a bug. Something is wrong with substrate Er combo box. Try to put er=4.50 instead of er=4.5 in the input field and filter synthesis will work. — Reply to this email directly, view it on GitHub <#1509 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AFJIB53CCPWL3ZGTSMBJWMT325KR3AVCNFSM6AAAAACK7PNI42VHI2DSMVQWIX3LMV43URDJONRXK43TNFXW4Q3PNVWWK3TUHMYTIOBVHAZTQNY> . You are receiving this because you authored the thread.Message ID: ***@***.***>