# Phase/Magnitude Detector - RF Cafe Forums

The original RF Cafe Forums were shut down in late 2012 due to maintenance issues. 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

Top

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.

Top

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!

Posted  11/12/2012

RF Cafe Software

Wireless System Designer

RF & EE Symbols Word
RF Stencils for Visio
Calculator Workbook
RF Workbench
Smith Chartâ„¢ for Visio
Smith Chartâ„¢ for Excel

1996 - 2022
Webmaster:
Kirt Blattenberger,
BSEE - KB3UON

RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling 2 MB. Its primary purpose was to provide me with ready access to commonly needed formulas and reference material while performing my work as an RF system and circuit design engineer. The Internet was still largely an unknown entity at the time and not much was available in the form of WYSIWYG ...

All trademarks, copyrights, patents, and other rights of ownership to images and text used on the RF Cafe website are hereby acknowledged.

My Hobby Website:
AirplanesAndRockets.com

Try Using SEARCH
to Find What You Need.
There are 1,000s of Pages Indexed on RF Cafe !