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1.3GHz filter design

Posted: Thu Oct 13, 2011 7:31 pm
by markaren1
Hi All,

Just working on field trials of DigiLite-ZL (http://www.idesignz.org/DigiLiteZL/DigiLiteZL.htm) and need a half reasonable filter between the survey antenna and a portable DVB-S RX.

Current thoughts are to hand build an interdigital design using strips of FR4 + copper, maybe 2mm wide as the resonators, grounded at one end and tuned using low value Johanson PTFE trimmers at the hot end. Resonators will be somewhat short than quarter-wavelength and will be glued to a ground plane.

50R feed point will be a few % from the cold end, and probably need 5 poles (?) to achieve > 40db rejection at +-100MHz.

This really seems like the sort of thing that should have been done before, and before I grapple with uWave office (or ask some kind soul to) I am hoping that someone may have pointers to prior art.

I looked at PCB hairpin filters, but performance and centre freq is dominated by variations in batch to batch FR4 laminate manufacture. I considered using Rogers laminate, but this is not readily available so I am planning to stick with FR4 for the moment.

Thoughts and pointers please.

Thanks,

Mark
ZL3JVX etc.

Re: 1.3GHz filter design

Posted: Sat Oct 15, 2011 11:14 am
by G8ADM
Alternatively you can buy suitable filters from:

http://www.bvdavies.org.uk/filter/index.htm

or

http://www.id-elektronik.de/en/index.htm

Regards,

Dave.
G8adm