Overview of Signals & Systems

Hany FerdinandoDept. of Electrical Engineering

Petra Christian University

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General Overview

It is an general introduction to signals and systems

Examples of signals and systems Applications of signal and system

theory

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Introduction

The concept of signals and systems arise in and extremely wide variety of fields

They have important role in such diverse areas of science and technology Communication, aeronautics, circuit design,

acoustics, seismology, biomedical, energy generation and distribution, chemical process control, speech processing, etc.

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Communication

Design of RF transceiver Modulation Choosing the suitable media for

transmission Noise removal Echo cancellation Filtering

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Circuit Design

Block diagram concept Simulation and analysis

Transient and steady state response Transformation Filter design Sampling

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Biomedical Engineering

Signal processing of EEG and ECG Image processing in USG Noise removal Signal amplification Filtering

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Energy Generation & Distribution

Active power filter High freq. in the power line signal Simulation and analysis Block diagram concept

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Speech Processsing

Noise removal Filtering Transformation

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Definition

A signal is a phenomenon, arising in some environment, that may be describe quantitatively

Examples of signal are voltages and current in electrical circuit, audio signals, visual signals, sequence of bits from computers, RF signal from transmitter, ECG and EEG signal,

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Definition

A system is any part of environment that causes certain signals that exist in that environment to be related

Examples of system are

an electrical circuit (it relates voltage and current),

a television (audio and visual signals),

a country (national income, demography, etc.)

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General Concept

System usually has input and output Such a system is called input-output

system We do not require that the input

determine the output uniquely

System outputinput

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Examples…

Resistive electrical circuit system

Consider a resistor element connected to a voltage source. We can assume that voltage is the input and current acts as output. But for some input voltage, there is no unique output current

This is input-output system

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General Concept (cont.)

If an input uniquely determines the output, it is called input-output mapping system

Usually, signal is a function of time, such a signal is called time-signals Discrete-time signals Continuous-time signals

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Examples…

Parity Bit Generator

A Parity bit generator always receives the digital input and gives the output uniquely for every input. It depends on the parity bit generator uses even- or odd-parity

This is input-output mapping system

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Examples…

Dow-Jones averages

It is a weighted average of the price of a selected portfolio of stocks traded in NYSE, which has been daily computed and recorded since 1897

This is discrete-time signals

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Examples…

The outdoor temperature

The outdoor temperature at any given place taken as a continuous function of time. The physical world abounds with continuous-time signals

This is continuous-time signals

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General Concept (cont.)

There are two systems: Discrete-time systems (systems

associated with discrete-time signals) the time axis is finite and countable

Continuous-time systems (system associated with continuous-time signals) the time axis is infinite and uncountable

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App. to Signal Processing

A typical problem in the area of signal processing is the removal of unwanted noise from a signal.

Can you give examples?

A model u = s + n is frequently used, where s is transmitted signal and n is noise added to the signal

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App. to Signal Processing

The problem is how to design a filter as shown in figure below, whose function is to remove or at least attenuate the noise.

Filter+

+signals

noisen

received signalu = s + n

filtered signaly

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App. to Communication Eng.

Communication engineering deals with transferring information from one location to another. It uses high frequency waves as carrier.

Modulatormessage

s

Modulated carrier (z)

Demodulatormessage

y

Modulated carrier (z)

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App. to Automatic Control

Control engineering concerns itself with the design of automatic controller, whose purpose is to govern the dynamic behavior of a given system, e.g. automatic cruise control in a car

Cruise Controller Car

Car speed (v)Ref. speed (vr)

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App. to Power System

Power Filter

Voltage and current with high frequency due to non linear load

Controller

Normal signal

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Next…

We have discussed the overview of signals and systems. This is important in giving a brief information about signal and system.

Next, we will study an introduction to signal. You can read books:

Signals and Systems by Alan V. Oppenheim, chapter 2, page 7-35