Fourier Transform
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hey guys i am kinda new to matlab, and would really appreciate it if you guys help me thanx so much
Generate the following function
y1(t)=2*sin(2*pi*1*t)+4*sin(2*pi*2*t)+3*sin(2*pi*4*t)
y2(t)=2*cos(2*pi*1*t)+4*cos(2*pi*2*t)+3*cos(2*pi*4*t)
First, required by sampling theorem, the step size of t (delta t) has to be smaller than a value. Figure out this value and set the delta t at least 3 times smaller than this value and calculated y1(t) and y2(t). Increase the step size and recalculate y1(t) and y2(t). See the difference.
Calculate Fourier Transform of y1(t) and y2(t) using ‘fft’ and plot your results. Using frequency as the x axis data and amplitude as the y axis data. Also, plot the phase, too.
f=[0:1/length(y1):1/2]*(1/delta_t)
figure; plot(f, abs(y1(1:length(f))), ‘-*’)
Use function of ‘abs’ to calculate the amplitude and ‘angle’ to calculate phase.
3 个评论
Paulo Silva
2011-2-21
doc fft
zaini
2011-2-21
please use code writing mode, to make it more readable
khalid
2011-2-21
回答（2 个）
Sulaymon Eshkabilov
2019-5-16
delta_t=0.001; % Sampling time
fs=1/delta_t; % Sampling frequency
t = 0:delta_t:pi;% Time space
N = 2048; % Block size
y1=2*sin(2*pi*1*t)+4*sin(2*pi*2*t)+3*sin(2*pi*4*t);
y2=2*cos(2*pi*1*t)+4*cos(2*pi*2*t)+3*cos(2*pi*4*t);
Y1 = abs(fft(y1, N));
Y2 = abs(fft(y2, N));
f=(0:length(Y1)-1)*fs/length(Y1);
plot(f, Y1, 'r-', f, Y2, 'b'), grid on, legend('Y1', 'Y2', 'location', 'SouthEast')
title 'FFT of y_1(t) and y_2(t)'
xlim([0, 10])
shg
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2022-1-16
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