what do you obtain when you do the f

y(t) = rect(t/pi)*cos(25t)

what do you obtain ? How do you plot it not with Matlab ?

what is FT Y(w)

[KSSV]

What is rect?

[Babacar Dieng]

the rectangular box function whose FT is the sinC function.

[Babacar Dieng]

to do this by hand. you consider the fact that the product is null every where the rect box is null, that is outside of width of box = [-pi/2, pi/2]. Then inside the rect box width, the max value of the the product is 5.

Plot the cosine(25t) inside the box and you get the result. ( freq = 25/2pi, period=1/freq=0.2513, number of period inside the box n= pi/(0.2512) =12.5).

Answer 1

[Star Strider]

‘what do you obtain ?’

Run it and plot it (using the Signal Processing Toolbox rectpuls function) to see the result —

t = linspace(-pi, pi, 500);
y = @(t) rectpuls(t/pi).*cos(25*t);

figure
plot(t, y(t))
grid
xlabel('Time')
ylabel('Amplitude')

.