Problem with Crystal Filters - IMD - RF Cafe Forums
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Post subject: Problem with Crystal Filters - IMD Posted: Thu Dec 04, 2008 10:52 pm
Joined: Fri Jan 26, 2007 2:40 am
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?
Post subject: Posted: Mon Dec 22, 2008 5:34 pm
Joined: Mon Jun 27, 2005 2:02 pm
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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