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RobG

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Bozeman, MT

Re: DC offset cancellation
Reply #15 - Apr 24^th, 2012, 6:21am

loose-electron wrote on Apr 23^rd, 2012, 8:14pm:

This method gets used in GSM receivers for many years with the offset setting frozen for the TDMX cycle. (Adjust while transmitting, freeze setting while receiving.)

OK, I understand what you are doing now. I didn't realize you were holding the correction value since that hasn't been an option for me (excepting when you ping-pong between two zeroed amps). Yes, that would be probably be better if you have two different modes.

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loose-electron

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San Diego California

Re: DC offset cancellation
Reply #16 - Apr 24^th, 2012, 2:29pm

RobG wrote on Apr 24^th, 2012, 6:21am:

loose-electron wrote on Apr 23^rd, 2012, 8:14pm:

This method gets used in GSM receivers for many years with the offset setting frozen for the TDMX cycle. (Adjust while transmitting, freeze setting while receiving.)

OK, I understand what you are doing now. I didn't realize you were holding the correction value since that hasn't been an option for me (excepting when you ping-pong between two zeroed amps). Yes, that would be probably be better if you have two different modes.

Like I said - you can also do it in a continuous mode ,
as long as the feedback offset steps are a small amount of the received signal.

I don't see what the problem is visualizing this.

This stuff is old news you don't see it in IEEE JSSC
publications, because its been around so long.

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Jerry Twomey
www.effectiveelectrons.com
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Contract IC-PCB-System Design - Analog, Mixed Signal, RF & Medical

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RobG Community Fellow Offline Posts: 570 Bozeman, MT	Re: DC offset cancellation Reply #17 - Apr 24^th, 2012, 2:48pm loose-electron wrote on Apr 24^th, 2012, 2:29pm: Like I said - you can also do it in a continuous mode , as long as the feedback offset steps are a small amount of the received signal. Well duh, even I can see that �;) But won't that put a 1 lsb tone at the update frequency?
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loose-electron Senior Fellow Offline Best Design Tool = Capable Designers Posts: 1638 San Diego California	Re: DC offset cancellation Reply #18 - May 5^th, 2012, 10:46am sure will, but that can be dealt with, and you have a lot of freedom in how you control your feedback updates.
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