June 7, 2010 1RPS

Hardware and Software Optimization of BABSMOM System

FIR Filter

s1150072 Yumiko Kimezawa

Research Progress Seminar

Outline

• Digital filter• FIR filter• Why is an FIR filter used ?• Structure of an FIR filter• Data flow diagram• Future work

June 7, 2010 RPS 2

Raw ECG/EKGData ROM

VirtualExternalMemory

LEDController

Graphic LCD Controller

SlaveCPU

Slave CPU Memory

Timer Master CPUMemory

MasterCPUTimerShared

MemoryFIR Filter

GraphicLCDLED JTAG

UART

PPD Module Master Module

ADC 1

ADC 12

FIR 1

FIR 12

Buffer

ECGSignal

Analysis

ExternalMemory

1:Signal reading 2:Filtering 3:Analysis

P = # mV Q = # mVR = # mV S = # mV T = # mV U = # mV Interval = # ms

4:Display

June 7, 2010 3RPS

Digital filter

June 7, 2010 RPS 4

•Digital filter Mathematical processing to digital signalNoise rejectionWaveform extraction

•FIR filter- Finite Impulse Response filter

•IIR filter- Infinite Impulse Response filter

There are two main types of a digital filter are

This ECG/EKG system uses an FIR filter.

FIR filter

June 7, 2010 RPS 5

FIR filter•One of the ways to configure a digital filter

•A liner phase

an oscillation does not happen

•Inherent stability

a distortion of waveform does not happen

•Impulse response is finite

Why is an FIR filter used ?

June 7, 2010 RPS 6

The data from analog/digital converter is finite and discrete digital signal.

This ECG/EKG system use FIR filter.

Structure of an FIR filter

June 7, 2010 RPS 7

An FIR filter is shown by the following difference equation.

NnNnn xaxaxany 110][

N

iinixa

0

nx][ny),,1,0( Niai

N

: Input signals

: Output signals

: Filter order

: Filter coefficient

It shows the way to process signals.

Data flow diagram

June 7, 2010 RPS 8

The FIR filter is composed of three parts.

1Z 1Z 1Z

nx 1nx 2nx Nnx

0a 1a 2a Na

][ny

Figure: The basic block diagram for an FIR filter of N order.

Data flow diagram

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1Z 1Z 1Z

nx 1nx 2nx Nnx

0a 1a 2a Na

][ny

Delay element- temporal delay- delay signal for one clock for

sampling

Data flow diagram

June 7, 2010 RPS 10

1Z 1Z 1Z

nx 1nx 2nx Nnx

0a 1a 2a Na

][ny

Data flow diagram

June 7, 2010 RPS 11

1Z 1Z 1Z

nx 1nx 2nx Nnx

0a 1a 2a Na

][ny

Multiplier- multiply filter coefficient by an input

signal

Data flow diagram

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1Z 1Z 1Z

nx 1nx 2nx Nnx

0a 1a 2a Na

][ny

Data flow diagram

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1Z 1Z 1Z

nx 1nx 2nx Nnx

0a 1a 2a Na

][ny

Adder-Add output result from all

multiplier

Difference equation

June 7, 2010 RPS 14

An FIR filter is shown by the following difference equation.

NnNnn xaxaxany 110][

N

iinixa

0

nx][ny),,1,0( Niai

N

: Input signals

: Output signals

: Filter order

: Filter coefficient

1Z 1Z 1Z

nx 1nx 2nx Nnx

0a 1a 2a Na

][ny

Future work

• Understand current ECG Algorithm- Pam Tompskins

• Understand new algorithm developed last year- Period-Peak Detection (PPD) Algorithm

June 7, 2010 RPS 15