Delta Modulation

Discussion in 'General Electronics Chat' started by mentaaal, Feb 19, 2009.

  1. mentaaal

    Thread Starter Senior Member

    Oct 17, 2005
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    Hey guys, We were recently doing a tutorial on delta modulation and I am puzzled by the receiver's operation.

    The receiver is baically an accumulator and a delay circuit . The accumulator sums the previous value (provided by the delay circuit) along with the new value and the output of this gets passed through a band pass filter and you have your reconstructed analogue signal. What's bothering me is not how the receiver follows the signal, thats fine, its more the AMPLITUDE of the demodulated signal. The demodulator has the facility of following the modulated signal (up down up up down, etc) but, say for example the demodulator gets turned on at an arbitrary time and the accumulator (using an integrator with a capacitor and say the capacitor is initially uncharged) the demodulator will be able to follow the waveform but how does the whole waveform get appropriatly represented at the receiver?

    I'm rambling so perhaps an example will help elaborate my problem:
    Say the modulating signal is a sinusoidal signal with a dc component such that the entire sinusoid is shifted up (looking at an oscilloscope screen) the delta modulator follows this and sends the appropriate errors across to the decoder which is only just turned on with 0 amplitude in the accumulator. This then follows the sinusoid but about the zero axis, effectively removing any dc component. I'm guessing this doesnt happen in reality so how is this problem prevented?
     
  2. bertus

    Administrator

    Apr 5, 2008
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  3. mentaaal

    Thread Starter Senior Member

    Oct 17, 2005
    451
    0
    Thanks for the links Bertus, and I looked at the page on sigma-delta modulation but it doesnt explain much about the demodulator following the modulator. Perhaps my question is trivial but I am just missing something here...
     
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