Digital Signal Processing Reference
In-Depth Information
4.3
Computer Laboratory
Exercise 2: Simulation of A/D Sample and Hold (S & H) circuits using
Simulink
3
A Sample and Hold (S & H) circuit is the key element required in the
conversion of a voltage from analog to digital form. The S & H circuit samples
the input analog voltage periodically and then holds it constant. The circuit
following the S & H circuit is the quantizer circuit, which converts the
sampled signal into the digital signal.
In this laboratory, the aim is to study the effects of practical sampling and
quantization on the input signal and also on the reconstructed signal at the
receiver.
Practical circuit for A/D conversion:
The schematic of a practical A/D circuit is shown in Figure 4.5a. The ideal
S & H, shown in the figure, is equivalent to impulse train modulation
s(t)
0 T 2T
x
c
(t)
Uniform
quantizer
encoder
Quantized
Signal
Zero-order
hold
h
0
(t)
X
x
0
(t)
x
s
(t)
(a)
x
0
(t)
(b)
x
c
(t)
-3T -2T -T 0 T
FIGURE 4.5
Practical sampling using sample and hold (S & H) circuit.
