Digital Signal Processing Reference
In-Depth Information
Therefore the analog and digital approaches can complement each other as well
as compete. There are still relatively wide areas where signals are processed in an
analog way simply because the available digital techniques are not applicable un-
der given conditions or are not good enough. Application of digital techniques is
limited. The dominant and most important limitation is the highest value of signal
sample that is achievable under given specific conditions. It is well defined and
violation of this limitation leads to distortion of the signal processing results due
to frequency overlapping or the so-called aliasing effect. Attempts to eliminate the
harmful impact of aliasing have led to the development of advanced digital tech-
nologies for signal processing, specifically to the development of an innovative
technology called 'digital alias-free signal processing', or DASP. This strength-
ens the competitiveness of digital techniques considerably. The successful use of
special digitizing techniques for the elimination of aliasing has been important
in showing the significance of digitizing in the whole process of signal digital
processing. Many other benefits could be obtained similarly by focusing on dig-
itizing and matching it to the needs of signal processing, as suggested by DASP.
This topic provides answers to questions as to what can be achieved in this way
and how the signal digitizing process needs to be to altered to gain these benefits.
While the application range of the suggested approach is rather wide and various
benefits could be gained in this way, specific aspects need to be taken into account.
This is the subject covered by the whole topic. In this chapter, the first comments
are made to clarify this issue, the basic one being the attitude towards digitization
of signals.
The most frequent applications of the traditional DSP technology belong to
the entertainment sphere, forming the basis for audio, digital radio, TV and vari-
ous other multimedia systems. Quite popular is also the use of these techniques
for building fixed-line and mobile phone sets. Less visible are DSP industrial
applications, especially because they are often presented as embedded systems.
However, the role of digital signal processing techniques in modern telecommu-
nication, instrumentation, industrial control, biomedical, radar, navigation and
many other data acquisition and processing areas is significant.
An attempt is made in this topic to focus the discussions basically to industrial
applications of the considered digital technology. The industrial tasks for signal
processing are typically challenging and cover a wide range of signal processing
conditions. Signals have to be processed in time, frequency, modulation and
spatial domains. The frequency range to be covered is very wide, extending from
ultra-low frequencies up to several GHz. Processing is often multidimensional
and in real-time. The signal digitizing and digital processing problems considered
in this topic are related to these industrial applications through described methods,
algorithms, hardware, and software tools.
