Re: noise reduction
1. Minimize the noise source.
Often this source operates as antenna.
Digital high current outputs spread the noise very well.
Therefore minimize the current in such outputs.
Freese the warm noise source, or minimize its resistance .
2. Make the signal immune to noise.
Such signal can be transferred through high current, low impedance wire.
Noise immune modulation can be used.
3. Signal and/or noise source screening.
Divide the digital and analog circuit feeding.