Design an Input Signal

Hello everyone,

I am tasked with creating a PRBS signal without using matlab shortcuts. Please see below. Once I create this PRBS signal I will run it through a p-code file and get an output. I am supposed to plot the system input vs time. It should look like the second picture.

Here is the code I have so far. I attempted to create a random signal and then run it through the transfer function.

My code is probably wrong so it is definitly not set in stone.

I do not know how to make the signal look almost digital. The example shows the input signal is either negative 1 or positive 1.

When I ran my code, I got two figures back. Please see below.

Any help or direction is greatly appreciated.

clear all
close all
clc
fs=300;                 % Sampling Frequency in Hz
t_final=1140;           % Overall test duration in seconds
time=0:1/fs:t_final;
time=time';
fc=1000;
Wc=2*pi()*fc;
num=0.27;
den=[1 0.95*Wc 1.4*Wc^2 0.74*Wc^3 0.27*Wc^4];
G = tf(num,den)
x1=rand(length(time),1);
U = lsim(G,x1,time);
[Y]=MysterySystem(time,U);
figure
plot(time,Y,'linewidth',2)
xlabel('Time (seconds)')
ylabel('Output (dimensionless)')
title('Heraldo Tello - Experimental Testing of the Unknown System')
grid on
figure
plot(time,U)

Answer 1

[Image Analyst]

You might look at fewer seconds so you can see the signal. Who told you to use that fs, fc, and t_final?

To get values of -1 or +1 only, you can do

signal = 2 * randi([0, 1], 1, numElements) - 1;

[Heraldo Tello]

I had to manipulate the code a bit to make it work for me to this

U = 2*randi([0 1], length(time), 1)-1;

nonetheless, it did work and produced an input signal that closely mimics the example I provided.

Thanks very much. Saved me a ton of time and headache on this problem.

[Image Analyst]

You're welcome. Thanks for Accepting.

time() is a built-in function. Since you're not supposed to use built-in function names as variable names, I suggest you call it times instead of time.