I Need Help In Phase Sensitive Demodulator

[fawad_hd97]

I need a Phase Sensitive detector(demodulator) that has two inputs i.e
a reference input " ASinwt" and a modulated input "kASinwt" and the output should be 'k'

where parameters are;

ASinwt has amp 2 Vrms and freq 60Hz

k is a varrying factor (-1<k<1) and may vary sinusoidally

 

[manojkrshukla]

YOU NEED BASICALLY DIVIDING CIRCUIT.
USE A DIVIDE-BY CIRCIT USING OPAMP.

 

[Kral]

fawad_hd97,
Connect an op amp and 3 equal valued resistors as follows (R1 = R2):
R1: Input resistor to Inv Input
R2: Feedback resistor from output to Inv input
R3: Input resistor to NI input
Bottom side of analog switch to ground
R1, R3, input sides connected to kASin(wt)
Analog switch driven by "sqared-up" Asin(wt), e.g., thru a comparator.
.
This is a full-wave demodulator with output proportional to k. Output is either + or -, depending on whether the analog switch drive is in-phase or out of phase with the input, i.e., whether k is + or -. You can filter the output to get pure DC.
.
The output is also proportional to the cosine of the phase shift between the input sine wave, and the analog switch drive. Of course, in your application the phase shift is zero.
Regards,
Kral