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    Colin created the topic: stripline(buried) filter??

    I was thinking of making a filter buried between the ground plane/power plane to avoid radiation. All the filter's I've ever seen/designed were built on microstrip such that they were visible- I'm wondering if that's a good/bad idea and if anyone's seen that before? My googling hasn't gotten me too far.
    thanks, cc
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    Tomassoni replied the topic: stripline(buried) filter??

    Yes, it is possible to obtain buried filters by using stripline technology. However there is a risk of exciting spurious modes, such a the spurious TEM mode and the parallel plate modes. To avoid the excitation of such modes, vias surrounding the filter can be exploited. The vias connect the top metal plate to the bottom metal plane.
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    Dave replied the topic: stripline(buried) filter??

    If you've got access to a decent CAD tool (Sonnet, CST, MWO/Axiem, HFSS, etc) you can check that the structure won't exite unwanted modes.

    The bigger challenge with stripline filters is that you can't easily get in and fiddle with line lengths/impedances to tweak the response. But depending what you're after (frequency, IL, VSWR, skirts, etc) again a good CAD tool will help you get pretty close. Sonnet have a free version which IIRC is limited only in model size.
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    Desert Sage replied the topic: stripline(buried) filter??

    A well built microstrip filter doesn't radiate badly. Stay away from parallel coupled line filters though. They will (launch surface modes, radiate, etc.).
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