presentation on digital signal processing

Digital signal processing

CONTENTS

INTRODUCTION

TERMS AND COMPONENTS

WORKING OF DIGITAL SIGNAL PROCESSOR

COMPARISION WITH MICROPROCESSORS

DIGITAL FILTER AND ITS TYPES

APPLICATIONS

Terms of signal processing

DIGITAL: Operating by the use of discrete signals

to represent data in the form of numbers. SIGNAL: A variable parameter by which

information is conveyed through an electronic circuit.PROCESSING: To perform operations on data

according to the programmed instructions. Digital signal processing :IT can be

defined as analysis, interpretation, and manipulation of signals like sound, images time-varying measurement values and sensor data

What is DSP?

Converting a continuously changing waveform (analog) into a series of discrete levels (digital)

What is DSP?

The analog waveform is sliced into equal segments and the waveform amplitude is measured in the middle of each segment

The collection of measurements make up the digital representation of the waveform

What is DSP?

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How Does It Work?

A waveform is sliced up and converted it into digital form

Draw a simple waveform on graph paper Scale appropriately

“Gather” digital data points to represent the waveform

Starting Waveform Used to Create Digital Data

Waveform Created from Digital Data

How Does It Work?

Compare the original with the recreating, note similarities and differences

Noise Filtering Using Averaging

NOISE FILTERING

Three most commonly used digital modulation schemes for transmitting

Digital data over bandpass channels are:

Amplitude shift keying (ASK) Phase shift keying (PSK) Frequency shift keying (FSK)

When digital data is transmitted over an all digital network a scheme known As pulse code modulation (PCM) is used.

Digital modulation techniques

DIFFERENCE BETWEEN MICROPROCESSOR AND DIGITAL SIGNAL PROCESSOR

A microprocessor with its limited speed is meant for low speed applications whereas the DSP is meant for fast real time applications.

Generally microprocessors use Van-nuemann architecture whereas most of the DSP processors use a modified Harvard architecture with two or three memory buses.

VARIOUS DSP PROCESSORSTexas DSP Processors

16-bit Fixed point arithmetic processors TMS320C1X TMS320C2X TMS320C5X TMS320C8X

32-bit floating point arithmetic processors

TMS320C3X TMS320C4X

WHAT IS DIGITAL FILTER

Digital filter:numerical procedure or algorithm that transforms a given sequence of numbers into second set of sequence that has some more desirable properties.

DIGITAL FILTER

INPUT SEQUENCEOutput sequence

TYPES OF DIGITAL FILTER

Broadly speaking ,two types of digital filters exists.

FIR Filters(Finite impulse response filters)

IIR Filters (Infinite Impulse response filters)

FINITE IMPULSE RESPONSE FILTER

INFINITE IMPULSE RESPONSE FILTER

DIFFERENCE BETWEEN FIR AND IIR FILTER

FIR filter: uses only current and past input digital samples to obtain a current output sample value. It does not utilize past output samples. Simple FIR equation is mention below.

y(n)= h(0)x(n) + h(1)x(n-1) + h(2)x(n-2) + h(3)x(n-3) + h(4)x(n-4) 

IIR filter: uses current input sample value, past input and output samples to obtain current output sample value. Simple IIR equation is mention below.

 y(n)= b(0)x(n) + b(1)x(n-1) + b(2)x(n-2) + b(3)x(n-3) + a(1)y(n-1) + a(2)y(n-2) + a(3)y(n-3)

WHAT IS IDEAL FILTER?

An ideal filter is transmits signal under the pass band without attenuation and completely suppress the signal in stop band.

Characteristics – it have constant gain in pass band

and zero gain in the stop band. It has linear phase response. It must be causal .

Desired features

Desired features depend on the application. INPUT SIGNAL OUTPUT SIGNAL

Generated by sensing Having less noise Device(microphone) or interference Speech With reduced

redundancy for

better efficiency of transmission

ADVANTAGES OF DIGITAL FILTER OVER ANALOG

An analog filter is constructed using active, passive components like resistors, capacitors and op ampsbut a digital filter constitutes adder, multiplier and delay elements.

 Digital filters are software programmable, which makes them easy to build and test.

 Digital filters require only the arithmetic operations of addition, subtraction, and multiplication.

 Digital filters do not drift with temperature or humidity .

 Digital filters have a superior performance-to-cost ratio.

APPLICATIONS OF DSP

Digital signal processing has variety of applications in diverse fields like

Digital filteringSpectral analysisSpeech processing Image processingRadar processing

Robot controlTelecommunicationConsumer electronicsBiomedical engineeringMilitary applications

In graphic equalizers sound as well as frequency levels can varied to produce special sound effects

and compensate for the lower sensitivity of the ear .

• enhancement of edges in imagesimprove recognition of object (by human or

computer)edge – a sharp transition in the image brightness,

sharptransitions in a signal (from Fourier theory) appear

ashigh-frequency components which can be amplified

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