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IQ phase Error and Image rejection - 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.


wallace0075
Post subject: IQ phase Error and Image rejection Posted: Tue Sep 12, 2006 12:06 pm

Lieutenant

Joined: Fri Feb 11, 2005 6:32 am
Posts: 4
hello guys,

two questions:

I have a device (Zero-IF) and an analyzer with IQ inputs , I'd like to measure- the image rejection. How can I do it?

-what is the relation between IQerror and image rejection??

regards,
Wallace


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jaslovkel
Post subject: Posted: Tue Jul 10, 2007 10:53 am

Captain


Joined: Tue Jun 26, 2007 10:27 am
Posts: 11
Location: Dallas, TX
Hi wallace0075,

For Image Rejection you may need to do a basic theoretical analysis. You can set up a basic block diagram (signal flow diagram) for an I/Q receiver. Add some gain mismatch in one path and add some phase mismatch to the LO path. Then, sum up the outputs of the I and Q paths (you can take the difference also, and get the same relationship) so that you end up with a SSB response at the output.

Your expression will then contain an expression for the desired frequency and for the sideband frequency. You then take the powers of the desired and undesired and take the quotient. This will then give you an expression for SBRR based on amplitude and phase mismatch.

An example of this can be found here:
http://ieeexplore.ieee.org.ezproxy.tamu ... mber=33037
Hope this helps!

-J





Posted  11/12/2012
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