Article | SIGNALS AND SYSTEMS

Running head: SIGNALS AND SYSTEMS
SIGNALS AND SYSTEMS
Name of the Student
Name of the University
Author Note

SIGNALS AND SYSTEMS1
The Fourier transform of discrete signal is obtained by the fft function in MATLAB. The fft
of any discrete signal x(n) is represented by,
X(k+1) = ∑
n =0
N−1
x ( n+ 1 ) W N
kn
Where, X(k+1) is the signal after performing Fourier transform.
Where,
W N =e
− j 2 π
N
MATLAB code for DFT:
data = xlsread('data.xlsx');
t = data(:,1);
signal = data(:,2);
figure(1)
plot(t,signal)
title('blood flow signal')
ylabel('signal amplitude')
xlabel('time t in secs')
dftsig = fft(signal); amp = abs(dftsig);
phase = angle(dftsig);
df = 1/(t(2)-t(1));

SIGNALS AND SYSTEMS2
freq = ((t(1):length(dftsig)-1)*df)/length(dftsig);
figure(2)
subplot(2,1,1)
plot(freq,amp)
xlabel('Frequencies of sinusoids')
ylabel('Amplitude of sinusoids in kg/h')
ax= gca;
ax.XTick = [0,1,2,3,4,5];
title('Amplitudes vs frequency')
subplot(2,1,2)
plot(freq,phase*180/pi)
xlabel('Frequencies of sinusoids')
ylabel('Phase of sinusoids in degrees')
ax= gca;
ax.XTick = [0,1,2,3,4,5];
title('Phase vs frequency')