Re: Anti-aliasing ADC samples

There is a way to digitally filter a signal without suffering from
aliasing. It is called the bi-linear z transform method. You design
an analog filter, and then transform it to a digital filter by
substituting (2/T)[(1-z^-1)/(1+z^-1)] for s, where T is the sampling
interval. Actually, the (2/T) factor is not necessary, but most books
on DSP include it. The resultant filter will have better attentuation
performance than the corresponding analog filter prototype. The
transformed filter suffers from "frequency warping". You compensate for
this by pre-warping the critical frequencies before you design the
analog prototype filter. Neither the phase vs frequency curve nor the
step response of the digital filter will match the correspondimg phase
and step response characteristic of the analog prototype filter. Any
book that covers digital filtering will have a section on the bilinear
z-transform. See, for example, "Therory and Application of Digital
Signal Processing" by Rabiner and Gold.

.

Relevant Pages

  • Analog to digital filter
    ... RC filter with time constant Ï? ... system that has the same sample rate and equivalent impulse response. ... response of the analog filter, create a digital system with a sampled ... Your digital filter should ...
    (comp.dsp)
  • Re: FIR Filter limitation (or not?)
    ... So I got the point that the response of a digital filter just ... > correctly, this is because all signals when digitized, are, in the ... we would be commiting a huge no-no for the frequency components ...
    (comp.dsp)
  • Re: FIR filter sampling frequency
    ... the reason for the sampling requirements are to ... The operation, or rather clock rate, of your digital filter depends ... You can 'clock' your digital filter at pretty much any rate you want. ...
    (comp.dsp)
  • Re: Delta-sigma ADC digital filtering
    ... I'm working on a university project, building a delta-sigma ADC converter ... from discrete components and implementing a digital filter in an AVR ... Probably the goal of the project is to learn what is AVR and how does delta-sigma work. ...
    (comp.dsp)
  • Re: Effect of OverSampling
    ... modulation frequency. ... That data is then put through a digital filter to ... A sigma delta converter usually has graphs showing what the frequency response of the digital filter looks like. ...
    (comp.dsp)
Loading