Phase Sensitive Detection methods

Thread Starter

hunterage2000

Joined May 2, 2010
487
Hi, I'm working on different ways to do PSD using a 3 op-amp inst amplifier. I have done it with a CMOS 4053 switch with 555 timer and with a AD630 mod/demodulator device. Is there any other effective ways to do this?
 

BillB3857

Joined Feb 28, 2009
2,501
Phase-locked-loop IC's will do phase detection and provide an output voltage proportional to the phase displacement. Also, a Google search of Phase Detector will give a variety of suggestions.
 

t06afre

Joined May 11, 2009
5,934
Hi, I'm working on different ways to do PSD using a 3 op-amp inst amplifier. I have done it with a CMOS 4053 switch with 555 timer and with a AD630 mod/demodulator device. Is there any other effective ways to do this?
You have also a digital way of doing this. Used in digital lock-in amplifiers.
The lock-in amplifier is basically a synchronous demodulator followed by a low-pass filter. The measured signal and the reference signals are sampled. And after that all is done digitally. Signals are multiplied sample by sample. Then run through a low pass filter. I once made an AC skin conductance meter using a sound card and Labview. Using the latter technique.​
 
The phase sensitive detector is basically a 4 quadrant multipler.
Phase lock loops often use a simple exclusive OR function to approximate it.
A simple one op amp and one switch to ground circuit will do an Analogue x digital multiplication or phase sensitive detection.
Take a standard inverting op amp circuit with gain of -1.
disconnect to +ve opamp input from ground and connect it to the Analogue input via a resistor, add the shunt switch to ground at the +ve input of the op amp.
When the switch is on the circuit has a gain of -1.
When the switch is off the circuit has a gain of +1.
If the signals are in phase you will get a full wave rectified version of the input.
If they are out of phase the output polarity will be reversed.
The switch is driven from the signal you want to phase detect to.
Follow up with some filtering as necesary.
 
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