Adaptive Filtering v Lock In Amp
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From: Bret Cahill on 12 Feb 2010 01:50 Can lock in amplification properly be considered a form of adaptive filtering? Bret Cahill
From: HardySpicer on 12 Feb 2010 02:46 On Feb 12, 7:50 pm, Bret Cahill <BretCah...(a)peoplepc.com> wrote: > Can lock in amplification properly be considered a form of adaptive > filtering? > > Bret Cahill I beleive a PLL could be classified in this way. It's non-linear of course and originally analogue in nature (though software version exist). It's all a matter of definitions. No way does it come under the current LMS FIR category but under perhaps an earlier Analogue genre - maybe. It could be looked at in the basic form as a tracking band-pass filter. Hardy
From: Bret Cahill on 12 Feb 2010 11:19
> > Can lock in amplification properly be considered a form of adaptive > > filtering? > I beleive a PLL could be classified in this way. It's non-linear of > course and originally analogue in nature (though software version > exist). > It's all a matter of definitions. No way does it come under the > current LMS FIR category but under perhaps an earlier Analogue genre - > maybe. > It could be looked at in the basic form as a tracking band-pass > filter. In a band that could change over time. The signal could have a constantly changing frequency and waveform and lock in filtering would still work as long as the reference changed along with the signal. Match filtering could also be made to work on wave form that changed with each pulse or cycle. The difference is that without a known phase angle match filtering has less information to begin with and therefore cannot reduce noise as much as PPL. Bret Cahill |