Biomedical Engineering Reference
In-Depth Information
CHAPTER
3
Classification of Signals
In this chapter, an overview of various methods to describe signals in a quantitative
manner is presented. Most medical devices in the 1950s and 60s presented their output in
a strip chart for the physician to view and make some determination (diagnosis); however,
with the advent of digital computers and advanced automated analytical processes, it has
become necessary to classify and quantify signals.
So, the questions are: “Why is it necessary to quantify signals?” and “How is it
useful?” Reasons for signal quantification are as follows:
1.
By representing signals as mathematical models, the engineer/researcher is able
to carry out system analyses under specified conditions
2.
The engineer may be after the information that the signal carries.
a. Can your thoughts be decoded from your brainwaves?
3.
To specify the form of a signal that will be used in the design of systems to
perform specific tasks.
a. Examples:
i. Petrofski's work in feeding electrical signals back into paralytic limbs in
order to cause the patient to walk
ii. Auditory or visual prostheses?
4.
Finally, classification and quantification provide physical insight for the analyst
or designer.
a. If an engineer wants to design a “Star Trek Tricoder” for vital life signs, what
signal characteristics and values does the engineer need to consider?
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