IP3 narrowband versus wideband- RF Cafe Forums
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Post subject: IP3 narrowband versus wideband Posted: Fri Oct 26, 2007 6:28 pm
Joined: Fri Oct 26, 2007 5:29 pm
I have measured the IP3 point of an amplifier with a narrowband signal.
Is there a formula which takes into account the bandwidth of the signal. Is it simply IP3 + 10 log (BWratio)?
Is there a reference which talks about this issue?
Post subject: Posted: Sat Oct 27, 2007 8:05 am
Joined: Mon Jun 27, 2005 2:02 pm
As far as I know there is no formula that takes into consideration the BW of the signal.
According to the IEEE, the space between the 2 tones should be up to
+/-5% of the carrier or the middle frequency of operation.
Post subject: Posted: Sun Oct 28, 2007 8:20 pm
Joined: Sat Apr 22, 2006 11:14 pm
The intercept point is defined as a combination of single tones, so there really isn't a wideband equivalent. I've read several papers about modeling wideband signals with multiple tones (Dr. Gard @ NC State has some good papers on this), so people are looking at that. In this case, you are looking at combinations of IP3/IP5/IP7, and spectral regrowth is generally what's its referred as.
If you are looking at wideband separation of tones (2 tones separated at several MHz), then the relative phasing of the 2F1-F2 and 2F2-F1 terms can lead to asymmetry on the high side and low side tones.