Problem with Crystal Filters - IMD - RF Cafe Forums

RF Cafe Forums closed its virtual doors in late 2012 mainly due to other social media platforms dominating public commenting venues. RF Cafe Forums began sometime around August of 2003 and was quite well-attended for many years. By 2012, Facebook and Twitter were overwhelmingly dominating online personal interaction, and RF Cafe Forums activity dropped off precipitously. Regardless, there are still lots of great posts in the archive that ware worth looking at. Below are the old forum threads, including responses to the original posts. Here is the full original RF Cafe Forums on Archive.org

-- Amateur Radio

-- Anecdotes, Gripes, & Humor

-- Antennas

-- CAE, CAD, & Software

-- Circuits & Components

-- Employment & Interviews

-- Miscellany

-- Swap Shop

-- Systems

-- Test & Measurement

-- Webmaster

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

Top

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...

Posted  11/12/2012