INTRODUCTION TO SIGNALS AND SYSTEMS:

A signal is a function of time, e.g.,

f is the force on some mass

vout is the output voltage of some circuit

p is the acoustic pressure at some point

notation:

f, vout, p or f(.), vout(.), p(.) refer to the whole signal or function

f(t), vout(1.2), p(t + 2) refer to the value of the signals at times t, 1.2, and t + 2, respectively
for times we usually use symbols like t, t , t1, . .

AM radio signal

FM radio signal

cable TV signal

audio signal

NTSC video signal

10BT Ethernet signal

telephone signal

Signal: something conveys information, represented mathematically as functions of one or more independent variables. Classified as:

Continuoustime (analog) signals, discretetime signals, digital signals

Signalprocessing systems are classified along the same lines as signals: Continuoustime (analog) systems, discretetime systems, digital systems

In sampling of an analog signal x_{a}(t):
1/T (reciprocal of T) : sampling frequency
Fig:1 Graphical representation of a discrete time signal; the abscissa is continuous while the x[n] is defined only at discrete instances
System

a system transforms input signals into output signals

a system is a function mapping input signals into output signals

we concentrate on systems with one input and one output signal, i.e., singleinput, singleoutput (SISO) systems

notation:
Block System

systems often denoted by block diagram

boxes denote systems; arrows show inputs & outputs
SIGNALS AND SYSTEMS

Modeling the physical world

Physical system (e.g., LRC circuit) – using mathematical equation

Input/output signal – using mathematical function
Example :LRC

LRC represented by a mathematical Equation

ordinary diff. eqn.

No sampling (continuous time system)

V(i) is a mathematical function
Different systems can be MODELED using the same mathematical function
Human speech production system — anatomy and block diagram
Signals and System Categorizations
Discrete time (digital)
Continuous System Example

A digital player/recorder
Analog Input Sampling Signal Reconstructed Digital Output
Digital Signal
References: Authors are unknown.
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