Problem Since the Ts value is quite large,ie .07 and the period of the sinusoidal t0 = .0769 So, we cant plot 13 ycles of 13Hz accurately as we hardly get 1 point in each cycle.
Solution
However when we lower the Ts value considerably,say Ts=0.7/100 we increase the step size and get a clearer sinusoidal wave.
Matlab code:.F0 =13; T0 =1/F0; Ts = 0.07/100; t = 0:Ts:13*T0; x = real(exp(j*(2*pi*F0*t-pi/2))); plot(t,x)