12 Biomedical Engineering Fundamentals
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become very popular recently [9], although the use of antibodies in biological assays
has been a very common analysis in laboratory.
12.3 Basics of Signals and Systems
The signal definition plays a very important role in understanding the behavior of
signal processing algorithm and its interpretation. The signal can be represented as a
function of independent variables and these independent variables can vary from one
to many. In other words, signal can be considered as a physical quantity which varies
with respect to these independent variables and this physical quantity also contains
some kind of information and behaves as a function of one or many independent
variables.
12.3.1 Types of Signals
The major classification of signals is as follows [10].
12.3.1.1 Continuous, Discrete Time, and Digital Signals
The signals which have continuous amplitude and continuous time are known as
continuous signals. These signals are also known as analog signals and such signals
are defined at any point of time. These signals are generally denoted by f (t) where
f is a function which depends on the continuous variable t which is continuous in
nature. Figure 12.10 shows an example of continuous-time signal.
Fig. 12.10 Continuous-time sinusoidal signal