文档介绍：Digital Processing of Digital Processing of
Continuous-Time Signals Continuous-Time Signals
• Digital processing of a continuous-time
• Conversion of a continuous-time signal into
signal involves the following basic steps:
digital form is carried out by an analog-to-
(1) Conversion of the continuous-time digital (A/D) converter
signal into a discrete-time signal,
• The reverse operation of converting a
(2) Processing of the discrete-time signal, digital signal into a continuous-time signal
(3) Conversion of the processed discrete- is performed by a digital-to-analog (D/A)
time signal back into a continuous-time converter
signal
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Copyright © 2001, S. K. Mitra Copyright © 2001, S. K. Mitra
Digital Processing of Digital Processing of
Continuous-Time Signals Continuos-Time Signals
• Since the A/D conversion takes a finite • To prevent aliasing, an analog anti-aliasing
amount of time, a sample-and-hold (S/H) filter is employed before the S/H circuit
circuit is used to ensure that the analog • To smooth the output signal of the D/A
signal at the input of the A/D converter converter, which has a staircase-like
remains constant in amplitude until the waveform, an analog reconstruction filter
conversion plete to minimize the is used
error in its representation
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Copyright © 2001, S. K. Mitra Copyright © 2001, S. K. Mitra
Digital Processing of
Sampling of Continuous-Time
Continuous-Time Signals
Signals
Complete block-diagram
Anti- • As indicated earlier, discrete-time signals in
aliasing S/H A/D Digital D/A Reconstruction
filter processor filter many applications are generated by
• Since both the anti-aliasing filter and the sampling continuous-time signals
reconstruction filter are analog lowpass • We have seen earlier that identical discrete-
filters, we review first the theory behind the time signals may result from the sampling
design of such filters of more than one distinct continuous-t