Biomedical Engineering Reference
In-Depth Information
TABLE 2.1:
How Are Systems Classified
When classifying a system, the following questions should
be considered:
1.
What is the order of the system?
2.
Is it a causal or noncausal system?
3.
Is it a linear or nonlinear system?
4.
Is it a fixed or time-varying system?
5.
Is it a lumped or distributed parameter system?
6.
Is it a continuous or discrete time system?
7.
Is it an instantaneous or a dynamic system?
of the system. For example, (2.2) may be used to represent a system as a differential
equation and to classify the system as an “
n
th” order system.
a
n
d
n
y
dt
n
a
n
−1
d
n
−1
y
dt
n
−1
a
1
dy
+
+···+
dt
+
a
◦
(
t
)
y
b
m
d
m
x
dt
m
b
m
−1
d
m
−1
x
dt
m
−1
b
1
dx
=
+
+···+
dt
+
(2.2)
b
◦
y
2.2 CAUSAL VS. NONCAUSAL
What is a causal or noncausal system? A “Causal System” is defined as a physical nonan-
ticipatory system whose present response does not depend on future values of the input,
whereas a “Non-causal System” does not exist in the real world in any natural system.
“Non-causal System” exists only when it is man-made by simulating the system with a
time delay.
2.3 LINEAR VS. NONLINEAR
What is a linear or a nonlinear system? From previous classes you have learned that when
the output vs. the input is a straight line, the system is considered to be linear. Do not
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