DSPic Digital Lockin Amp

[EET72]

In one of the other posts a member mentioned and posted a link to Microchips Digital Lock In Amplifier. I downloaded the application and got it running on my Explorer board. My question is if this code can lock onto a specific frequency and tell you both phase and magnitude of that frequency couldn't you use this to ID \ discriminate targets? My idea was to generate a pulse width changing square wave into a transmit coil and read in the receive coil through an ADC. I would then run an FFT on this and grab the frequencies of interest. I could then look at magnitude and phase of each of these to build a table to use as my target ID look up list. Does this sound like it would work?

[bbsailor]

In one of the other posts a member mentioned and posted a link to Microchips Digital Lock In Amplifier. I downloaded the application and got it running on my Explorer board. My question is if this code can lock onto a specific frequency and tell you both phase and magnitude of that frequency couldn't you use this to ID \ discriminate targets? My idea was to generate a pulse width changing square wave into a transmit coil and read in the receive coil through an ADC. I would then run an FFT on this and grab the frequencies of interest. I could then look at magnitude and phase of each of these to build a table to use as my target ID look up list. Does this sound like it would work?

What the lock-in amplifier is doing is similar to the integration circuit where hundreds to thousands of cycles are processed while a small target signal is extracted from the noise.
If you always sample the target signal in the same phase place then you can add all those detected and integrated signals together to act as a very steep band pass filter. Since noise is random, only a quickly changing target signal gets processed and amplified, while slower changing signals like ground are subtracted to minimize the effects of ground variation.

The key factors are (1) TX frequency, (2) coil size, (3), sweep speed , and TX pulse optimization for defined target time constant ranges.

I hope this helps.

bbsailor