22-05-2012, 12:32 PM
SIGNALS and SYSTEMS
SIGNALS & SYSTEMS.ppt (Size: 2.86 MB / Downloads: 156)
SIGNAL
Signal is a physical quantity that varies with respect to time , space or any other independent variable
Eg x(t)= sin t.
the major classifications of the signal are:
(i) Discrete time signal
(ii) Continuous time signal
Energy and power signal
A signal is said to be energy signal if it have finite energy and zero power.
A signal is said to be power signal if it have infinite energy and finite power.
If the above two conditions are not satisfied then the signal is said to be neither energy nor power signal
SYSTEMS WITH MEMORY AND WITHOUT MEMORY
A system is said to be memory less if the output at any time depends on only the input at that same time. Otherwise, the system is said to have memory
y(t) = Rx(t)
An example of a system with memory is a capacitor C with the current as the input x( t ) and the voltage as the output y ( t) ; then
y(t) = 1/c ʃ x(τ) dτ
A second example of a system with memory is a discrete-time system whose input and output sequences are related by
y[n] = Σ x[n]
LINEAR TIME INVARIANT SYSTEMS
Two most important attributes of systems are linearity and time-invariance. The input-output relationship for LTI systems is described
in terms of a convolution operation. The importance of the convolution operation in LTI
systems stem from the fact that knowledge of the response of an LTI system to the unit
impulse input allows us to find its output to any input signals