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Microstrip BP Filter from an Elliptic Prototype - RF Cafe Forums

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Post subject: microstrip BP filter from an elliptic prototype Posted: Sat Dec 31, 2005 8:20 am


Joined: Sun Aug 14, 2005 3:24 pm
Posts: 2
Location: iran
Hi everybody

I should design a narrow band BP filter on microstrip in s band. the requiered degree of the filtr using chebyshev prototype is 21 but using elliptic is just 7. but I can't find a systematic way to depart from this elliptic LP prototype to a BP common filtr type on microstrip. All I found is for all-pole filtrs not for an elliptic type.

may anyone help?


Post subject: Posted: Sat Dec 31, 2005 9:51 am

Site Admin

Joined: Mon Jun 27, 2005 2:02 pm
Posts: 373
Location: Germany
Hello eastern,

In general you reach to any type of filter from the LP prototype by using the Koruda transformations. To transfer to microstrip from lumped elements you will have to use Richards transformations.

Nowadays you can use a simulation tool which does all this work for you and provides you with pretty accurate results. You will need to use both linear simulation to tune your microstrip length and width and coupling between the resonators and also to use an EM simulation to see how the filter performs inside walls.

My preferred choice would be Eagleware GENESYS (Now part of Agilent). This tool has synthesis functoins for lumped and distributed filters in which you can define the topology, required attenuation etc and get a circuit schmeatic including values. It also has an EM simulation capability.

Good Luck!

Best regards,

- IR


Post subject: Microstrip Elliptic-function filtersPosted: Sat Dec 31, 2005 7:48 pm
Just a small point: If you google for the transformations, you need to type in "Kuroda" not "Korodah".

Good Luck!


Post subject: Posted: Sat Dec 31, 2005 10:03 pm

Site Admin

Joined: Mon Jun 27, 2005 2:02 pm
Posts: 373
Location: Germany
Thanks for the correction guest. It should be Kuroda.

For you eastern here is a link to an application note that may be useful:


Best regards,

- IR

Posted  11/12/2012

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