Multiplication of envelope function to that of sine wave

Hello,

I am trying to multiply a base sine wave to that of a square wave and this square wave should act as an switch i,e if there is amplitude 1 then the sine should be present else 0,

t = 0:1e-4:0.1;

x = (1+square(4*pi*50*t)).*sin(2*pi*1000*t); %carrier frequency is 1khz and modulation frequency is 50hz

plot(t,x)

my question is I want different duration for both square function which is acting as an envelope and sine function which is the base and should be modified according to the envelope, but when I try to do it with two different durations it is giving me a matrix mismatch.

t = 0:1e-4:0.1;

ts = 0:1e-4:0.4

T = [t ts]

x = (1+square(4*pi*50*t).*sin(2*pi*1000*ts); %carrier frequency is 1khz and modulation frequency is 50hz

plot(T,x)

Thank you.

Answer 1

[Star Strider]

I would just use the same value (either ‘t’ or ‘ts’) for both —

t = 0:1e-4:0.1;
ts = 0:1e-4:0.4;
T = [t ts];
x = (1+square(4*pi*50*t).*sin(2*pi*1000*t)); %carrier frequency is 1khz and modulation frequency is 50hz

figure
plot(t,x)
xlim([0  0.02])                                                         % Zoom For Detail (Optional)

It would be possible to use both, however it would then be necessary to create a matrix of them, and that could be difficult to represent, for example —

x = (1+square(4*pi*50*t.')*sin(2*pi*1000*ts)); %carrier frequency is 1khz and modulation frequency is 50hz

figure
surf(ts, t, x)
grid on
xlabel('ts')
ylabel('t')
axis([0  0.025    0  0.00025    zlim])                                  % Zoom For Detail (Optional)

figure
surf(ts, t, x, 'EdgeColor','none')
grid on
xlabel('ts')
ylabel('t')

.