how to compute the complex Fourier series expansion of half-wave rectified signal. and plot its phase and amplitude spectrum?

My Question in the title, i am new to matlab and i need help with this please

Answer 1

[Sulaymon Eshkabilov]

Hi,

Here are several nice tutorial examples of matlab on Fourier Transform.

https://www.mathworks.com/help/matlab/math/fourier-transforms.html

Answer 2

[Star Strider]

My impression is that this is homework. We give hints for homework, not complete code. (You must write the code. We will help you to get your code to run if you have problems with it.)

It is straightforward to compute the Fourier transform symbolically. You need to remember also to allow for the part of the signal that is zero in the time range that you are computing it.

You already discovered Hi how do i plot a halfwave rectifier signal in matlab? i tried the coding below and only got the fullwave (since you posted a Comment to it to request thatI look at this Question), all you then need to do is to read the documentation for fft and use that with the signal I provided in that Answer.

[WJ]

its actually not a homework, i am trying to check the amplitude and the phase, for my own study, but i never used matlab before and idont even know how to code, i know the coefficants of the series and the idea of phasing, but i dont know how to use this app thats why i am asking for some help, please help me and thanks

[WJ]

and the thing is that i dont even have the function of the half wave rectified so i can use fft

[Star Strider]

In that instance, use the second part of my Answer and plot the fft of the half-wave rectified signal.

The table that you posted appears to require a context that is not provided.

[WJ]

i am trying to

f=50;

t=linspace(0,30,500);

x=sin(2*pi*f*t);

rect_sig = sig > 0;

y = fft(x);

f = (0:length(y)-1)*50/length(y);

plot(f,abs(y))

title('Magnitude')

subplot(221)

stem(t,abs(sig))

i cant get the amplitude spectra

it should be straight lines, any help?

[WJ]

i fixed it a little bit

l=linspace(0,10,100);

sig=sin(2*pi*50*l);

subplot(211)

plot(sig);

grid

% u=1:9;

% t=(1:)

for t=1:100

if sin(2*pi*50*l(t))<=0

sig(t)=0;

else

sig(t) = sin(2*pi*50*l(t));

end

end

subplot(212)

plot(sig);

grid

stem(l,abs(sig),'b')

still cant get straight lines

whats the issue?

[Star Strider]

Try this slightly modified version of your code:

f=50;
t=linspace(0,30,500);
Fs = 1/(t(2)-t(1));
Fn = Fs/2;
sig=sin(2*pi*f*t);
rect_sig = sig.*(sig > 0);                          % Half-Wave Rectification
y = fft(rect_sig)/numel(sig);     
f = linspace(0, 1, fix(numel(sig)/2)+1)*Fn;         % Frequency Vector
idx = 1:numel(f);                                   % Index Vector
% f = (0:length(y)-1)*50/length(y);
figure
subplot(2,1,1)
semilogy(f,abs(y(idx))*2)
title('Magnitude')
grid
subplot(2,1,2)
plot(f,unwrap(angle(y(idx))))
title('Phase')
grid

figure
% subplot(221)
stem(t,rect_sig)

.

[WJ]

how can i change the magnitude to amplitude?

i know i made trouble for you but i reaLLY APPRECIATE IT

[WJ]

how can i make the amplitude and phase look like this? as straight lines

or is it just like this when n= a constant number?

[Star Strider]

To get the amplitude (amplitude = magnitude) spectrum such as in the plot image, use the fftshift function, then plot using a symmetric frequency vector, for example:

sy = fftshift(y);
sf = linspace(-10,10, numel(sy));

then:

figure
stem(sf, sy)

or something similar.

Answer 3

[Swapnil Khot]

How we write code for half wave rectifier using Fourier series

Answer 4

[EE_student]

Wait have you sorted it out?