Difference Between Lock-In Amplifiers and other Coherence methods

[Caleb Rhyne]

Hello, I was wondering if somebody could explain to me the difference between using a lock-in amplifier and other signal coherence methods such as MSC. From my experience MSC is limited to the SNR. Are there any other methods that could produce signal detection in very low SNR, very low being -20 dB or more.

 

[zappedagain]

A lot depends upon your frequency range. When we used lock-ins 20+ years ago it allowed us to basically shift our low frequency data onto a carrier to move away from the 1/f noise at low frequencies, and then use the carrier to convert it back down to low frequencies (baseband) with a quieter circuit. If you already have a fast signal and can filter out the low frequency noise then it doesn't really help.

Are you referring to Magnitude Squared Coherence? A quick search shows that is more for higher frequency signals that probably don't have the 1/f problem. Others may chime in with more info.

Z