Digital Signal Processing Reference
In-Depth Information
Figure 20.5
Typical dedicated services of the embedded DASP systems provided for digital
processing of wideband analog signals
systems are unusual, not paralleled by other types of embedded systems. Basically
they need to widen significantly the frequency band within which the analog input
signals can be fully processed digitally. More specifically, the dedicated services
provided by them are based on the following functions:
digitizing analog input signals in a way making it possible to avoid aliasing-
induced errors at the following digital processing of these signals;
performing signal digital preprocessing matched to the nonuniformities of the
sampling process;
presenting the results of digital preliminary processing of the signals into a form
acceptable for the classic DSP hardware and software tools, which are used for
further additional signal processing.
Some application hints are given in Figure 20.5 for the cases where the sig-
nals to be processed by the discussed embedded systems are analog. Firstly,
these signals could be digitized, the digital versions of them stored in a memory
and then processed when requested (Figure 20.5(a)). Note that the digital sig-
nal is typically encoded in a compressed form. Secondly, the digitized signals
are transmitted over wire or wireless channels, received, demodulated and pro-
cessed (Figure 20.5(b)). At least two embedded systems are obviously needed in
that case. Thirdly, processing of the digitized signal is carried out without delay,
preferably in the real-time processing mode, as illustrated by Figure 20.5(c).
Consider the suggested structure of this type of embedded system given in
Figure 20.1. It is assumed that signal sample values are taken at time instants dic-
tated by the generated pseudo-random sampling point process. This means that
