How to use hanning window to get 5 cyles of sine waves?

load ( 'x.mat' )
t = 0: 10 * pi; % 5 cyeles
sf = 200e3; % frequency
sinewave = sin (2 * pi * sf * x); % gen continuous sine waves
w = hanning (length (sinewave)); % hann
figure (1);
plot (w);

% I do not know where to include the 5 cycles here

Answer 1

[Andrey Kiselnikov]

First of all you should properly define your data: "t = 0: 10 * pi; % 5 cyeles" I assume that you would like to define something like this "t = 0:1/sf:10*pi", more over "t" never used. Can you describe your task more properly?

>> t = 0: 10 * pi

t =

  Columns 1 through 17

     0     1     2     3     4     5     6     7     8     9    10    11    12    13    14    15    16

  Columns 18 through 32

    17    18    19    20    21    22    23    24    25    26    27    28    29    30    31

[Ramesh Bala]

Hi I want to generate 5 cycles,200 kHz sine waves and my x is a time vector

[Ramesh Bala]

I want to generate for this time vector 'x' ,5 cycle sine waves and rest of the values to be as '0'

[Andrey Kiselnikov]

Can you attach your *.mat file with your time vector here?

[Ramesh Bala]

alright attached

[Andrey Kiselnikov]

This code was made for better understanding, it's quite not optimal.

If this answer is ok, mark it as accepted or let me know what's wrong.

load ( 'x.mat' )

sf = 200e3; % frequency

x1= 2*pi*sf*x;

five_cycles = find(x1 < 10*pi);

five_cycles = x1(five_cycles);

sine_five_cycles = sin(five_cycles);

w = hanning (length (five_cycles));

subplot(2,1,1);

plot(sine_five_cycles);

subplot(2,1,2);

stem (w);

[Ramesh Bala]

The code looks good,one question here

the sine_five_cycles values goes upto 1*64 for the time vector ,so the rest of the values are to be taken as '0' for remaining time values?

[Andrey Kiselnikov]

"find" return the result of comparison between array members and value 10*pi, the result has the same length as x1 array and it's logical type. Then we take from x1 the values that meet our condition by x1(five_cycles).

[Ramesh Bala]

HI

But the total time for this should be 2.5e-5

f = 200*10^3; % sine frequency[Hz]

sf = 10*10^6; % sampling frequency [Hz]

n = 5; % number of sine periods [-]

T = 1/f; % sine period [s]

tt = n*T; % total time [s]

but the code of yours gives 30 ?

So,I think it's converted to radians ,instead of using seconds.So,is that the reason.

Also,how to make it a modulated signal for the entire time vector,as the values are changing

[Andrey Kiselnikov]

Ok?

plot(x(1:length(sine_five_cycles)),sine_five_cycles);

[Ramesh Bala]

What I meant was the sine wave looks similar,will that be in modulated state as the time increases

f = 200*10^3; % sine frequency[Hz]

sf = 10*10^6; % sampling frequency [Hz]

n = 5; % number of sine periods [-]

T = 1/f; % sine period [s]

tt = n*T; % total time [s]

t = 0:1/sf:tt; % time vector

burst = sin(2*pi*f*t) .* hanning(size(t,2))';

plot(t,burst);

In this example the sine waves starts with 0,then increases and then decreases - a modulate signal.

How can i make the same with the 'x' time vector?

[Ramesh Bala]

this gives me a modulated signal (increasing-decreasing)

f = 200*10^3; % sine frequency[Hz]

n = 5; % number of sine periods [-]

T = 1/f; % sine period [s]

tt = n*T; % total time [s]

burst = sin(2*pi*f*x) .* hanning(size(x,2))';

plot(x,burst);

but it's not correct as it should be only for 5 signals and then rest of the vecot should be '0'( a flat signal)

[Ramesh Bala]

So,how to make it to start as modulated signal and then after 5 cycles to be flat signal =0

[mm99]

Hi!

Did you get the result? I need the same thing and stucked in the same moment.