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Delta Modulation (DM) 619
FIGURE 12.8
Block diagram of a delta modulation system
it follows that
̂˜s(n) =s (n − 1) + q (n − 1) (12.22)
Thus the estimated (predicted) value of s(n) isreally the previous sample
s (n − 1) modified by the quantization noise q (n − 1). We also note
that the difference equation in (12.21) represents an integrator with an
input ẽ(n). Hence an equivalent realization of the 1-step predictor is an
accumulator with an input equal to the quantized error signal ẽ(n). In general,
the quantized error signal is scaled by some value, say ∆ 1 , which is
called the step size. This equivalent realization is illustrated in Figure 12.9.
In effect, the encoder shown in Figure 12.9 approximates a waveform s (t)
FIGURE 12.9
An equivalent realization of a delta modulation system
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