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Phase/Magnitude Detector - 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.


eeboy
Post subject: Phase/Magnitude Detector Posted: Sun Oct 14, 2007 10:41 am

Lieutenant


Joined: Sun Oct 14, 2007 10:35 am
Posts: 2
Hello,

I am looking for a simple phase magnitude circuit. I have a few references which have a straight forward solution for obtaining the magnitude but the phase seems to be overly complicated (involving a diode ring modulator).

Any suggestions?

Thanks,
Jason


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nubbage
Post subject: Posted: Tue Oct 16, 2007 3:57 am

General


Joined: Fri Feb 17, 2006 12:07 pm
Posts: 218
Location: London UK
Hi eeboy
If you can down-convert the channels to HF (maybe the signal frequency is already <50MHz?) then an XOR logic followed by an integrator will measure phase fairly accurately. With the two channels squared off to logic levels and fed to a 74LS exclusive OR, the output will contain a narrow spike when the channels are in phase, and will be a logic 1 when they are 180 out of phase. Any in-between state gives a pulse whose width is proportional to the phase difference. The integrator is a pulse width to analog level low-pass filter.


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eeboy
Post subject: Posted: Tue Oct 16, 2007 4:34 am

Lieutenant


Joined: Sun Oct 14, 2007 10:35 am
Posts: 2
That's a beatiful solution... very simple!

One more issue though... this would give a good indication as to when the phase angle is zero however, it does not give an indication as to wether it's lagging or leading. I can't think of an easy method to accomplish this. I could always calculate the time between the voltage and current peak but this becomes not trivial. Any suggestions?

FYI, the frequency is 27MHz.

Thanks!







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