22-05-2014, 02:36 PM
Delta modulation
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INTRODUCTION
Delta modulation (DM or Δ-modulation) is an analog-to-digital and digital-to-analog signalconversion technique used for transmission of voice information where quality is not of primary importance. DM is the simplest form of differentialpulse-code modulation (DPCM) where the difference between successive samples is encoded into n-bit data streams. In delta modulation, the transmitted data is reduced to a 1-bit data stream.
Its main features are:
the analog signal is approximated with a series of segments
each segment of the approximated signal is compared to the original analog wave to determine the increase or decrease in relative amplitude
the decision process for establishing the state of successive bits is determined by this comparison
only the change of information is sent, that is, only an increase or decrease of the signal amplitude from the previous sample is sent whereas a no-change condition causes the modulated signal to remain at the same 0 or 1 state of the previous sample.