Post subject: Phase/Magnitude Detector Posted: Sun Oct 14,
2007 10:41 am
Joined: Sun Oct 14, 2007
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).
Posted: Tue Oct 16, 2007 3:57 am
Fri Feb 17, 2006 12:07 pm
Location: London UK
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.
Post subject: Posted: Tue Oct 16, 2007 4:34 am
Joined: Sun Oct 14, 2007 10:35 am
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