# Extraction of Periodic  signal masked by noise using correlation.

Aim: To extract a periodic signal masked by noise using correlation.

EQUIPMENTS:

PC with windows (95/98/XP/NT/2000).

MATLAB Software.

Program Code:

clear all;

close all;

clc;

n=256;

k1=0:n-1;

x=cos(32*pi*k1/n)+sin(48*pi*k1/n);

plot(k1,x)

%Module to find period of input signl

k=2;

xm=zeros(k,1);

ym=zeros(k,1);

hold on

for i=1:k

[xm(i) ym(i)]=ginput(1);

plot(xm(i), ym(i),'r*');

end

period=abs(xm(2)-xm(1));

rounded_p=round(period);

m=rounded_p

% Adding noise and plotting noisy signal

y=x+randn(1,n);

figure

plot(k1,y)

% To generate impulse train with the period as that of input signal

d=zeros(1,n);

for i=1:n

if (rem(i-1,m)==0)

d(i)=1;

end

end

%Correlating noisy signal and impulse train

cir=cxcorr1(y,d);

%plotting the original and reconstructed signal

m1=0:n/4;

figure

plot(m1,x(m1+1),'r',m1,m*cir(m1+1));

Output:

Result: In this experiment the Extraction of periodic signal masked by noise using correlation have been verified using MATLAB.

Viva Questions:

1. Define the condition for distortion less transmission through the system.

Ans: Transmission is said to be distortion less if the input and output have identical wave shapes within a multiplicative constant.A delayed output that retains the input waveform is also considered distortion less.Thus in distortion-less transmission, the input x(t) and output y(t) satisfy the condition:

y(t) = Kx(t - t) where t is the delay time and k is a constant

2. What is filter?

Ans:  Electronic filters are electronic circuits which perform signal processing functions, specifically to remove unwanted frequency components from the signal, to enhance wanted ones, or both.

3. What are low-pass and band-pass filter and what is the difference between these two?

Ans: Low-pass filter allows frequencies below cutoff frequency.

High-pass filter allows frequencies above cutoff frequency

4. Why is the impulse response "finite.

Ans: Impulse response is finite, Because Impulse has only one sample.

5.What is the importance of decimation for a given signal/sequence?

Ans: Decimation for a given signal/sequence will reduce the sampling frequency to required level.

• Updated
Feb 02, 2020
• Views
1,787
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