Modeling Lowpass and Highpass Filters with MATLAB

[odimachkie]

Homework Statement

use MATLAB to model a lowpass and highpass filter

Homework Equations

the high-pass filter:
V(sin(ωt)) = 1/C ∫i dt + iR
V(ω/(s^2 + ω^2)) = 1/C ∫i dt + iR
⇔LAPLACE⇔
L(i) = (Vωs/R)(1/(s^2 + ω^2)(s + 1/RC)) ⇔ partial fractions...
⇔LAPLACE^-1⇔
V/2 (cos(t) + sin(t)) - (V/2) e^-t

hope i got that all right...

The Attempt at a Solution

I can plot the poles on the s-plane and I can successfully transform and inverse transform into a statement with cos & sin...all on paper.

this question is more of a plea for help with matlab. I'm hoping someone has experience doing this sort of thing with MATLAB as i have next to no MATLAB knowledge... and our prof has just tossed us into the deep end without any guidance. he doesn't even know how to use it.

any sort of reference would be helpful.

 

[mighty2000]

Hello! As a fellow scientist, I can definitely relate to the struggle of learning new software without proper guidance. I have some experience using MATLAB for filter design, so I hope I can offer some helpful tips and resources.

First, I recommend checking out the MATLAB documentation on filter design. This page has a step-by-step guide on how to design and simulate lowpass and highpass filters in MATLAB: https://www.mathworks.com/help/signal/ug/designing-lowpass-and-highpass-filters.html

Additionally, you can use the built-in functions in MATLAB such as 'butter', 'cheby1', and 'cheby2' to design lowpass and highpass filters. These functions use the Butterworth, Chebyshev type 1, and Chebyshev type 2 filter design methods, respectively.

For example, to design a 6th order Butterworth lowpass filter with a cutoff frequency of 100 Hz, you can use the following code:

[b,a] = butter(6,100/(fs/2),'low'); % fs is the sampling frequency
freqz(b,a); % plots the frequency response of the filter
title('Butterworth Lowpass Filter');

You can also use the 'filter' function to apply the filter to your data. For more information on these functions, you can type 'help butter' or 'help filter' in the MATLAB command window.

Lastly, if you prefer a more visual approach to designing filters, MATLAB has a Filter Design and Analysis app which allows you to interactively design and simulate filters. You can access it by typing 'filterDesigner' in the command window.

I hope this helps get you started with designing lowpass and highpass filters in MATLAB. Don't hesitate to reach out if you have any further questions. Good luck!