Plotting a high frequency sine

11 次查看(过去 30 天)
MerTesla
MerTesla 2023-4-1
Hello to all, I am a EE student who tries to learn MATLAB, I had homework about Fourier Series and LTI systems response, and I found the response of the filter as
y = ((-36/(pi^2))*sin(2*pi*10^3*t)) - ((28/(9*pi^2))*sin(2*pi*3*10^3*t))-((4/(5*pi^2))*sin(2*pi*5*10^3*t))-((12/(49*pi^2))*sin(2*pi*7*10^3*t))-((4/(81*pi^2))*sin(2*pi*9*10^3*t))
I need to plot this function, but when I try to do it, it looks like nonsense. Also, I do not know how should I set the interval of the independent variable "t", and I think this might be the problem. But the period of the input signal to the filter is 1mS and the filter's bandwidth is 10kHz.
If you can help I would be very appreciated it. I'm adding my codes below. Thanks in advance.
My Code:
t=-10^-3:10^3;
y = ((-36/(pi^2))*sin(2*pi*10^3*t)) - ((28/(9*pi^2))*sin(2*pi*3*10^3*t))-((4/(5*pi^2))*sin(2*pi*5*10^3*t))-((12/(49*pi^2))*sin(2*pi*7*10^3*t))-((4/(81*pi^2))*sin(2*pi*9*10^3*t))
y = 1×1001
1.0e-08 * -0.0000 0.0001 0.0001 0.0005 0.0012 0.0025 0.0028 0.0034 0.0038 0.0015 0.0019 -0.0004 0.0029 0.0008 0.0037 0.0025 -0.0004 0.0094 0.0083 0.0129 0.0091 0.0136 0.0055 0.0091 0.0118 0.0149 0.0089 0.0115 0.0133 0.0067
plot(t,y);
xlabel("t")
ylabel("y(t)")

回答(1 个)

Walter Roberson
Walter Roberson 2023-4-1
Pi = sym(pi);
syms t real
y = ((-36/(Pi^2))*sin(2*Pi*10^3*t)) - ((28/(9*Pi^2))*sin(2*Pi*3*10^3*t))-((4/(5*Pi^2))*sin(2*Pi*5*10^3*t))-((12/(49*Pi^2))*sin(2*Pi*7*10^3*t))-((4/(81*Pi^2))*sin(2*Pi*9*10^3*t))
y = 
If you look at that you can see there is a sine wave of frequency 9000 Hz -- but it has low amplitude so it is difficult to see.
The most you can see is to roughly
fplot(y, [0 0.03])
which is pretty boring.
When you go to 1000 like you do, in 1 Hz increments, you get a lot of aliasing.

类别

Help CenterFile Exchange 中查找有关 Plot Customization 的更多信息

产品


版本

R2023a

Community Treasure Hunt

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

Start Hunting!

Translated by