problem with output from a demodulator (multiplier)

mpradhan1 said:

I am working on a project which is based on lock in amplification. Basically the main phase of the design is the phase sensitive detection where demodulation(multiplication) of two signals takes place.

For my project I have to extract a very weak signal buried in large noise. In the demodulator stage, the circuit works fine if i just multiply a simple sine wave and a square wave havin da same phase as it provides me fully rectified signal. But if I add the noise signal with the sin wave and then perform the demodulation step, the output does not turn out to be fully rectified signal.

I have tried lookin at all the specs but I cant figure out whats wrong with the procedure. Can anyone please please help me out with this ?? I will really appreaciate the help

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Code:

What does the output look like with noise added? Is it the rectified sine wave with nose?

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If you are trying to extract signal with wide bandwidth noise, then you need to apply a band pass filter at the frequency of the signal you're interested, prior to the modulator (multiplier).

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