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Problem with Crystal Filters - IMD - RF Cafe Forums

Because of the high maintenance needed to monitor and filter spammers from the RF Cafe Forums, I decided that it would be best to just archive the pages to make all the good information posted in the past available for review. It is unfortunate that the scumbags of the world ruin an otherwise useful venue for people wanting to exchanged useful ideas and views. It seems that the more formal social media like Facebook pretty much dominate this kind of venue anymore anyway, so if you would like to post something on RF Cafe's Facebook page, please do.

Below are all of the forum threads, including all the responses to the original posts.


jom
Post subject: Problem with Crystal Filters - IMD Posted: Thu Dec 04, 2008 10:52 pm

Captain


Joined: Fri Jan 26, 2007 2:40 am
Posts: 14
Anyone have a problem with IMD with crystal filters? I'm not quite sure what to do about it. I have a 100 MHz BPF with 15 kHz or so BW. It is pretty much the driver for the IMD in the radio chain. I could move around the gain distribution but the filter doesn't have a constant IP3 like most amplifiers. The IMD3 really doesn't drop at the 2 for every 1 rate.

Is this a common problem with crystal filters?

jom


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IR
Post subject: Posted: Mon Dec 22, 2008 5:34 pm

Site Admin


Joined: Mon Jun 27, 2005 2:02 pm
Posts: 373
Location: Germany
I would check the impedance match of the crystal to the amplifiers in the chain. It can be that this behavior is derived by impedance mismatch of the IMD products compared to a good impedance match of the fundamental signals.

Just my guess...








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