sine wave plot

Hi,

I am having some trouble plotting a sine wave and i'm not sure where i am going wrong.

i have

t = [0:0.1:2*pi]
a = sin(t);
plot(t,a)

this works by itself, but i want to be able to change the frequency. When i run the same code but make the change

a = sin(2*pi*60*t)

the code returns something bad. What am i doing wrong? How can i generate a sin wave with different frequencies?

[Ahmed Grera]

How many cycles do you need in drawing?

[Govinda Nahak]

in sine function in MATLAB it is always sin(wt). here frequency w is in radian/sec not f (in HZ) so w will give you the no.of the cycle.

suppose w=1 it is one cycle and so on

if you want to use the sin(2*pi*60*t) you can use the sind(2*pi*9.545*t). why i use the 9.545 bcz we should convert the f to w in the time interval of 2*pi.

[Jorge Ignacio Cisneros Saldana]

How can we make it 3 phase system? for 50 Hz and 230 V peak to peak

[Mellamputi Sai geetha]

x(t)=∆(t+7)-∆(t-7) prepare a MATLAB graph

[SREEGANESH VAKA]

Write a MATHLAB code to generate a CT step signal with peak Amplitude of 5 Volts and should be plotted on the time scale from 0 to 1000.

[Walter Roberson]

That does not seem to be relevant to the Question that was asked?

[Subhranil Barman]

Write a MATHLAB code to generate a CT step signal with peak Amplitude of 5 Volts and should be plotted on the time scale from 0 to 1000.

Answer 1

[Rick Rosson]

Please try:

   %%Time specifications:
   Fs = 8000;                   % samples per second
   dt = 1/Fs;                   % seconds per sample
   StopTime = 0.25;             % seconds
   t = (0:dt:StopTime-dt)';     % seconds

   %%Sine wave:
   Fc = 60;                     % hertz
   x = cos(2*pi*Fc*t);

   % Plot the signal versus time:
   figure;
   plot(t,x);
   xlabel('time (in seconds)');
   title('Signal versus Time');
   zoom xon;

HTH.

Rick

[Rajasekaran]

Thanks for your reply & detailed answer.

[Nauman Hafeez]

How to calculate Fs for a particular frequency signal?

I am generating a stimulating signal using matlab for my impedance meter and it gives me different results on different Fs.

[Sameeksha Singh]

This task has students detect the frequency of a sinusoid embedded within a noisy signal. To do so, we generate a set of candidate sinusoidal functions, each representing our guess for the unknown frequency. We then cross-correlate these functions with the input signal and then use the magnitude of the peaks in the output as a score for the presence of each frequency in the input signal. Let our signal be a sinusoid x(t) containing an unknown frequency that lies in the range from 1 Hz to 2 Hz. This signal is sampled at a rate of 30 samples per second by an analog-to-digital converter to create a digital signal x[n]. In this circumstance we will proceed as follows:

1. Hypothesize a sinusoidal sequence having frequencies ranging from f = [1Hz, 2Hz] in increments of 0.2 Hz. Create a digital lter h[n] to cross-correlate with the input x[n].

2. Adjust values of your lter coecients so that the sum of the lter coecients is equal to 0. This can be accomplished by sampling the sinusoid symmetrically about the origin since the sine function is odd symmetric, i.e., sin(x) = − sin(−x). Note that since sin(0) = 0 the sample h[0] has no contribution to either your lter or the output value.

3. For each sequence, cross-correlate your signal with the input signal. 4. Observe the output signal and nd the cross-correlation signal having largest peak response. This frequency is then the best guess for the unknown frequency in the input signal.

please help me I am new to MATLAB

[Jessica]

Att: Sameeksha Singh

Do not ask questions within other persons questions.

Here is how you do it:

Top right there is a "Ask the Community" button.

Click and copy/paste your question there.

Make sure that you have as much code or specific facts with, not so much text as possible.

[MUHAMMAD BASIM]

Can anybody please provide the MATLAB code for kalman filter for filtering out noise from a sine signal.please refer to attached picture for detail

[Walter Roberson]

When you searched MATLAB Answrs for kalman filter, and found the more than 600 results, what was unique about your situation such that none of the more than 600 results were suitable for even starting the code?

Answer 2

[Mike Mki]

Dear Mr. Rick, Is it possible to create knit structure in Matlab as follows:

Answer 3

[Robert]

aaa,

What goes wrong: by multiplying time vector t by 2*pi*60 your discrete step size becomes 0.1*2*pi*60=37.6991. But you need at least two samples per cycle (2*pi) to depict your sine wave. Otherwise you'll get an alias frequency, and in you special case the alias frequency is infinity as you produce a whole multiple of 2*pi as step size, thus your plot never gets its arse off (roundabout) zero.

Using Rick's code you'll be granted enough samples per period.

Best regs

    Robert

Answer 4

[Junyoung Ahn]

clear;
clc;
close;

f=60; %frequency [Hz]
t=(0:1/(f*100):1);

a=1;    %amplitude [V]
phi=0;  %phase
y=a*sin(2*pi*f*t+phi);
plot(t,y)
xlabel('time(s)')
ylabel('amplitude(V)')

Answer 5

[soumyendu banerjee]

%% if Fs= the frequency u want,
x = -pi:0.01:pi;
y=sin(Fs.*x);
plot(y)

Answer 6

[wilfred nwakpu]

   %%Time specifications:
   Fs = 8000;                   % samples per second
   dt = 1/Fs;                   % seconds per sample
   StopTime = 0.25;             % seconds
   t = (0:dt:StopTime-dt)';     % seconds
   %%Sine wave:
   Fc = 60;                     % hertz
   x = cos(2*pi*Fc*t);
   % Plot the signal versus time:
   figure;
   plot(t,x);
   xlabel('time (in seconds)');
   title('Signal versus Time');
   zoom xon;

Answer 7

[sevde busra bayrak]

sampling_rate = 250;

time = 0:1/sampling_rate:2;

freq = 2;

%general formula : Amplitude*sin(2*pi*freq*time)

figure(1),clf

signal = sin(2*pi*time*freq);

plot(time,signal)

xlabel('time')

title('Sine Wave')

Answer 8

[shampa das]

clc; t=0:0.01:1; f=1; x=sin(2*pi*f*t); figure(1); plot(t,x);

fs1=2*f; n=-1:0.1:1; y1=sin(2*pi*n*f/fs1); figure(2); stem(n,y1);

fs2=1.2*f; n=-1:0.1:1; y2=sin(2*pi*n*f/fs2); figure(3); stem(n,y2);

fs3=3*f; n=-1:0.1:1; y3=sin(2*pi*n*f/fs3); figure(4); stem(n,y3); figure (5);

subplot(2,2,1); plot(t,x); subplot(2,2,2); plot(n,y1); subplot(2,2,3); plot(n,y2); subplot(2,2,4); plot(n,y3);

Answer 9

[Radwa Ahmed]

9- Consider modulating a carrier cos(10t) with the following signals:

(a) 𝑥1 (𝑡) = 𝑒 −|𝑡| . Use MATLAB to find the Fourier transform of 𝑦1 (𝑡) = 𝑥1 (𝑡) cos(10𝑡) and plot y1(t) and its magnitude spectra. (b) 𝑥2 (𝑡) = 0.2[𝑟(𝑡 + 5) − 2𝑟(𝑡) + 𝑟(𝑡 + 5)], where r(t) is the ramp signal. Use MATLAB to 𝑥2 (𝑡) 𝑎𝑛𝑑 𝑦1 (𝑡) = 𝑥2 (𝑡) cos(10𝑡) and compute and plot the magnitude of their Fourier transforms.

[Walter Roberson]

This is not an Answer to the question that was asked.