Plot a sine wave with decreasing frequency over time

조회 수: 29(최근 30일)
Alison Huffman
Alison Huffman 2021년 8월 4일
댓글: Eike Blechschmidt 2021년 8월 9일
Hi! I'm trying to plot a sine wave whose frequency decreases linearly over time (amplitude stays the same). This is my code:
clear all;
close all;
clc
period = 0.08;
for x = 0:4/1000:2
a = 5;
b = ((2*pi)/(period + 0.001));
c = 300;
d = 30;
c = c * -1;
output = a.*sin(b.*(x+c))+d;
plot(x, output, 'Linewidth', 2);
end
When I run the code, my plot is blank. I know Matlab doesn't require the use of a "for" loop when plotting sinusoids, however I'm unsure of how else I can modify the frequency over time if I don't use a "for" loop. Any help is much appreciated!

답변(3개)

Eike Blechschmidt
Eike Blechschmidt 2021년 8월 4일
How about
f_upper = 50;
f_lower = 10;
t = 0:0.01:10;
f = linspace(f_upper, f_lower, numel(t));
a = 10;
x = a * sin(2*pi*f.*t);
plot(t,x)
  댓글 수: 1
darova
darova 2021년 8월 4일
DOesn't work well
f_upper = 5;
f_lower = 1;
t = 0:0.01:10;
f = linspace(f_upper, f_lower, numel(t));
a = 10;
x = a * sin(2*pi*f.*t);
plot(t,x)

댓글을 달려면 로그인하십시오.


darova
darova 2021년 8월 4일
Modify x coordinate
x = 0:.1:30;
y = sin(x);
x1 = x - 10*(x/max(x)).^2; % shift last point 10 units
plot(x1,y)
  댓글 수: 5
Eike Blechschmidt
Eike Blechschmidt 2021년 8월 9일
@darova changed the x-axis after calculating the sin. So I'm unsure (as in "I have not mathematically checked") if that solution is still expressable with a single sin function (you can always find multiple sin-waves to express any kind of time signal -> fourier transformation) which was my understanding of "is it still a sin function". My first solution does that as I only manipulate the input to the sin function. So I guess my question was not precise.

댓글을 달려면 로그인하십시오.


Eike Blechschmidt
Eike Blechschmidt 2021년 8월 5일
The easiest and correct is probably to use:
f1 = 50;
f2 = 10;
t = 0:0.001:10;
y = chirp(t,f1,t(end),f2);
plot(t, y);
  댓글 수: 3
Eike Blechschmidt
Eike Blechschmidt 2021년 8월 6일
You can also do
edit chirp
and scroll downt to
function yvalue = calculateChirp(f0,f1,t1,p,t,phi,isComplex)
It shows quite clear how the chirp is calculated.

댓글을 달려면 로그인하십시오.

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by