04-02-2013, 12:49 PM
Delta Modulation
Delta Modulation.ppt (Size: 620 KB / Downloads: 161)
INTRODUCTION
Next form of pulse modulation
Transmits information only to indicate whether the analog signal that is being encoded goes up or goes down
The Encoder Outputs are highs or lows that “instruct” whether to go up or down, respectively
DM takes advantage of the fact that voice signals do not change abruptly
The analog signal is quantized by a one-bit ADC (a comparator implemented as a comparator)
The comparator output is converted back to an analog signal with a 1-bit DAC, and subtracted from the input after passing through an integrator
The shape of the analog signal is transmitted as follows: a "1" indicates that a positive excursion has occurred since the last sample, and a "0" indicates that a negative excursion has occurred since the last sample.