Biomedical Engineering Reference
In-Depth Information
FIGURE 5-42
Typical configuration
for a DSP
application.
[Adapted from
(Brooker 2008).]
The signal can then be manipulated within a computer in various ways. This process
often produces intermediate results that are much larger than the input values, requir-
ing that a larger word size be used if fixed-point values are used; more commonly, a
floating-point representation is used. Once the signal has been processed, the final result
is often passed through a digital-to-analog converter (DAC) to change it from the internal
binary representation back to a voltage. It is therefore possible to represent a complete
digital signal processor (DSP), as shown in Figure 5-42, with ADCs a processor and
DACs.
The DAC outputs new values only at discrete times, so a continuous signal needs to be
reconstructed. This generally involves holding the signal constant (zero-order hold) during
the period between samples, as shown in Figure 5-43. This signal is then cleaned up by
being passed through a low-pass filter to remove high-frequency components generated
by the sampling process.
Other common methods of interfacing to the outside world include manipulating a
single-bit or a complete digital word to drive some peripheral device like a video display
FIGURE 5-43
Analog
reconstruction of a
sampled signal using
a zero-order hold.
