Chapter 2 linear time invariant systems continuous time systems Prepared by Dr. Taha MAhdy.
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Transcript of Chapter 2 linear time invariant systems continuous time systems Prepared by Dr. Taha MAhdy.
Chapter 2linear time invariant systems
continuous time systemsPrepared by
Dr. Taha MAhdy
What is a system?
A system is a mathematical model that represents the transformation of some input signal x(t) into an output signal y(t).
Systems
• In digital domain, the system may be a digital filter
Systems
• For our purposes, we aren't going to worry about the particulars of how the system is implemented.
• It will be a black box and our only concern will be the mathematical properties of the system.
Systems
• Mathematically, we represent the system by a transformation or operator that we will denote by T.
• Then we can write the action of a system on an input signal as
• Y(t) = T{x(t)}
• A system is known as a continuous time system if x = x(t) and y = y(t) are continuous time signals.
System properties: Memoryless Systems
• If the output y(t) of a given system depends only on the input x(t) at the same time, then the system is called memoryless.
• A simple example of a memoryless system is an output that depends on a constant multiple of the input y(t) = ax(t)
• where a is some real constant.
Memory system
• A system with memory is one where the output depends on the values of the
• input at previous times. An example of such a system is one where we add up
Example
Causal and Noncausal Systems
• If a system output y(t) depends only on the input at present or earlier times, we say that the system is causal. Another way to say this is that the output does not anticipate future values of the input.
• All memoryless systems are causal.
Non causal system
Linear Systems
Example
• Check the linearity (soln. a,c linear)
(soln. a,c linear)
Time (Shift) Invariance
System Stability
Example
cosh
The Unit Impulse Function
Properties of unit impulse
More properties
Very important
The Unit Step Function
The Unit Step Function
The Unit Step Function
The Unit Step Function
Square pulse using unit step
Relationship between unit impulse and unit step
Assignment
• Solve the problems of the chapter