Delta-Sigma Modulation?

Discussion in 'General Electronics Chat' started by ELECTRONERD, Jul 22, 2009.

  1. ELECTRONERD

    Thread Starter Senior Member

    May 26, 2009
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    Has anyone heard of Delta-Sigma Modulation? I've never heard of it before. What is it?

    Thanks in advance!
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
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  3. millwood

    Guest

    it is a way to convert amplitude information into a time information.

    it is basically a comparator that takes your input signal, and compares it against an integrated output from the comparator itself.

    the output has only two states: high or low. and it is how long it stays high / low (or its duty cycle) that carries the information about the original amplitude.

    aka, it is a "1-bit" adc.
     
  4. Dave

    Retired Moderator

    Nov 17, 2003
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    It is a single-bit quantisation, pulse-code modulation of an analogue signal, which works around the principle of delta-modulation.

    A delta modulator will produce an output that reflects the difference in adjacent sample of the input values rather than their absolute values (as in other analogue sampling regimes). It uses a sigma-section which subtracts from the incoming signal, lets call it x, another signal we'll call x' - if the difference is positive the 1-bit quantiser gives the output +q and if the difference is negative it gives -q. The stream of +qs and -qs gives the output stream y[n] which is a time-representation of the incoming signal. The x' signal is derived from an integration of the quantised stream. You can recover the original signal (at least a very close approximation of) from the output stream by firstly integrating y[n] (which gives x') and then filtering through an analogue reconstruction filter - this the process of delta-demodulation.

    Delta-sigma converters work on this principle though are structurally different employing both 1-bit ADCs and DACs with the integration section positioned immediately after the sigma-section as oppose to in the feedback path. From a circuits prespective try the e-book: http://www.allaboutcircuits.com/vol_4/chpt_13/9.html

    Dave
     
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