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Multitone 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.

Post subject: Multitone IMD Posted: Fri Oct 02, 2009 3:58 pm


Joined: Tue Sep 04, 2007 7:54 am
Posts: 13
Location: Dallas

This is about IM calculations in case of multitone.

For example take an amplifier with OPI3 of 18.1dBm, gain =11 dB. Two tone IM is 58.2 dBc. Input is -19 dBm
Output = -19+11 = -8 dBm. IM = 2(18.1-(-8))+6 = 58.2dBc

Now, I am driving this amplifier with 15 tones each having an input power of -19-10*log(15)=-30.8dBm
Total output power for 15 input tones = -8 dBm.
What will be the worst case IM in dBC with respect to -8dBm of total output power?


Kirt Blattenberger
Post subject: Re: Multitone IMDPosted: Fri Oct 09, 2009 3:32 pm

Site Admin

Joined: Sun Aug 03, 2003 2:02 pm
Posts: 308
Location: Erie, PA
Greetings ljoseph:

The link I used to have for a paper titled "A General Algorithm to Calculate Third Order Intermodulation Product Locations for any Number of Tones," by Chris Arnott, has disappeared from it's location on the CED website. So, I just scanned in and OCRed a copy provided to me by Chris back when I worked with him at RF Micro Devices. You can access it here:

Hopefully that will get you where you're going.

- Kirt Blattenberger
RF Cafe Progenitor & Webmaster

Posted  11/12/2012

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