Generating signals

I have been away from Matlab for awhile and will need to refresh myself. In the mean time I could use a little help getting restarted. I need analyze an output signal that consists of a binary signal that is added to a two tone interference signal.

The binary signal is; +1 for one unit of time starting a zero, -1 for two units of time then +1 for one unit of time, -1 for one unit of time and and finally +1 for one unit of time.

The interference signal is; .7cos(6pit)+.5cos(9pit+pi/4)

How would I go about generating these two signals, then adding them together? Thanks

Answer 1

[Arturo Moncada-Torres]

I assume that your binary signal is periodic (+1, -1, +1, -1, ...). You would have to do something like this:

% Sampling characteristics.
fs = 1000;  % [Hz]
Ts = 1/fs;  % [s]

t = 0 : Ts : 10-Ts;     % Time vector.

% Signals' amplitudes.
a1 = 0.7;
a2 = 0.5;

% Signals' frequencies [rad].
f1 = 6*pi;
f2 = 9*pi;

% Signals' phase [rad].
theta1 = 0;
theta2 = pi/4;

% Create the signals.
signal1 = a1 * cos((f1.* t) + theta1);
signal2 = a2 * cos((f2.* t) + theta2);

signal = signal1 + signal2;

% Create noise.
noise = zeros(1, numel(t));
for ii = 1:numel(noise)
    if mod(ii, 2) == 0
        noise(ii) = 1;
    elseif mod(ii, 2) == 1
        noise(ii) = -1;
    end
end

% Pollute signal.
signalNoise = signal + noise;

% Plots
figure();

subplot(3,1,1);
plot(t, signal1);
ylim([-1.5 1.5]);

subplot(3,1,2);
plot(t, signal2);
ylim([-1.5 1.5]);

subplot(3,1,3);
plot(t, signal);
ylim([-1.5 1.5]);

figure();

subplot(3,1,1);
plot(t, noise);
ylim([-1.5 1.5]);

subplot(3,1,2);
plot(t, signal);
ylim([-1.5 1.5]);

subplot(3,1,3);
plot(t, signalNoise);
ylim([-1.5 1.5]);

Try it and let me know if it works.

Answer 2

[Walter Roberson]

resolution = 20;
oneunit = ones(1,resolution);
binarysignal = [oneunit, -oneunit, -oneunit, oneunit, -oneunit, oneunit];
t = ((1 : length(binarysignal)) - 1) ./ resolution;
interference = 0.7*cos(6*pi*t) + 0.5 * cos(9*pi*t + pi/4);
totalsignal = binarysignal + interference;

Answer 3

[Al]

Thanks guys for the help, sorry I haven't got back sooner but got buried. I tired both scripts and they worked great. Really appreciate the help.