Multirate Digital Signal Processing

PRESENTED BYD.KIRUBASANKAR

ECE-III

Multirate signal processing means change(extend) the sampling rate in various parts of the system

There are many cases used in this process In high quality data acquisition and storage

systems Also used in audio signal processing In transmultiplexers Narrowband filtering for fetal ECG and EEG

Introduction

Up-sampler - Used to increase the sampling rate by an integer factor

Down-sampler - Used to decrease the sampling rate by an integer factor

There rare two samplers used in MRSP

An up-sampler with an up-sampling factor L, where L is a positive integer, develops an output sequence with a sampling rate that is L times larger than that of the input sequence x[n]

Block-diagram representation

Up-sampler

Lx[n] ][nxu

0 10 20 30 40 50-1

-0.5

0

0.5

1Output sequence up-sampled by 3

Time index n

Am

plitu

de

Figure below shows the up-sampling by a factor of 3 of a sinusoidal sequence with a frequency of 0.12 Hz obtained using

0 10 20 30 40 50-1

-0.5

0

0.5

1Input Sequence

Time index n

Am

plitu

de

Up-Sampler

Input sampling frequency

TFT

1

otherwise0,2,,0),/( LLnLnTxa

L)(][ nTxnx a y[n]

Output sampling frequency

'1'T

LFF TT

Figure below shows the relation between and for L = 2 in the

case of a typical sequence x[n]

SPECUTRUM OF UPSAMPLED SIGNAL

Down-sampling operation is implemented by keeping every M-the sample of x[n] and removing in-between samples to generate y[n]

Down-Sampler

0 10 20 30 40 50-1

-0.5

0

0.5

1Input Sequence

Time index n

Am

plitu

de

0 10 20 30 40 50-1

-0.5

0

0.5

1Output sequence down-sampled by 3

Am

plitu

de

Time index n

M

M

x[n]y[n]

Down-sampling Factor

An down-sampler with a down-sampling factor M, where M is a positive integer, develops an output sequence y[n] with a sampling rate that is (1/M)-th of that of the input sequence x[n]

Block-diagram representation

Anti-imaging filter Identifies(6 types) Cascading sample rate converters Efficient travel structure for decimator Efficient travel structure for interpolator Poly phase structure of decimator Poly phase structure of interpolator & Z-

transform Poly phase decimation using Z-transform Quatrature mirror filter bank

It also have more types

Sampling rate conversion is high

It gives more accuracy

Advantages

compact disc digital audio American television European television(All are used in frame type not in bitwise)

Applications

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