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how to generate time_step in matlab code

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andy2000a

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Hi
How to use matlab write a Low_pass filter .. I can use simulink for
simulation , but I want to know how to write a matlab code..

simulink file can novert to Matlab code or not ??

a low pass filter = 1/ (s+1) = e^(-t)

but how to descript expt(-t) in matlab code ??


thank you
 

To write e^(-t)=exp(-t)
also to have an interval of time in order to see your functions write
n=0:1:100 for example. 0 the strarting point 100 final point 1 step of time

Hope i helped
 

Hi
a simple 1 order Low_pass filter can be said Y= 1 /(s+1)
from DSP book
y= 1 / (s+a) ---> e^(-at)

if I use Matlab write
x=[0:1:100];
y=exp(-x);
plot(x, y);

but plot time response is from 1 --> 0

in real circuit is R=10k C=100u , time response from 0->1
time_constant = 4 sec ,
I also use simlink simulation it is ok , but how convert simulink to matlab
? by the way , simulink have "scope" can see "time response"
but if I want to see "frequency domain" like hspice .ac simulation
ho wshould I do ..

thank you
 

answer :

t=[0:1:10];
y= 1- exp(-t);
plot(t, y);


by the way , have anone use Dolphin smash ABCD language ?
I try use smash behavior simulation low pass filter ..
but no detail manual about ..
 

That is a standard issue.

Use substitution s->a*(1+z^(-1))/(1-z^(-1))

then you get an expression which could be easy translated to a Matlab formula.
 

If you have signal processing box installed, function 'freqs' is also useful. **broken link removed**

regards
 

If you want to implement the transferfunction 1/s+1 in Matlab:

Y= Tf([1],[1 1]);

%Plot the Bodediagram
figure
Bode(Y)

Greetz E-goe
 

andy2000a said:
Hi
How to use matlab write a Low_pass filter
thank you
Click to expand...

you can use butterworth, write "help butter" in command window or Chebyshev type I digital and analog filter design write "help cheby1",
 

try this code,

Code: 
% Filter Construction
fsample=2000;
frmsz=128;
f1=50;
f2=400;
t=(1:frmsz)/fsample;

yt=sin(2*pi*f1*t)+sin(2*pi*f2*t);
subplot(2,2,1)
plot(t,yt);
title('Input signal (time domain)')
xlabel('time (sec)')
ylabel('AMP.')

f=(1:frmsz/2)*fsample/frmsz;
yf=abs(fft(yt));
subplot(2,2,2);
plot(f,yf(1:frmsz/2))
title('Input signal (freq domain)')
xlabel('freq (hz)')
ylabel('AMP.')

forder=10;
fcutoff=200;
wn=fcutoff/(fsample/2);
[b,a]=butter(forder,wn,'low');
[H,w]=freqz(b,a,512);
w=w*fsample/2/pi;
plot(w,20*log10(abs(H)))
title('filter frequency response')
xlabel('freq (hz)')
ylabel('Magnitude (DB)')

ytfiltered=filter(b,a,yt);
subplot(2,2,3);
plot(t,ytfiltered);
title('Output signal (time domain)')
xlabel('time (sec)')

yff=abs(fft(ytfiltered));
subplot(2,2,4);
plot(f,yff(1:frmsz/2));
title('Output signal (Freq domain)')
xlabel('freq (hz)')
ylabel('AMP.')
 

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