A sinusoidal signal of frequency 0 = 10 4 /2 Hz is sampled at the rate

Question:

A sinusoidal signal of frequency ƒ₀ = 10⁴/2π Hz is sampled at the rate of 8 kHz and then applied to a sample-and-hold circuit to produce a flat-topped PAM signal s (t) with pulse duration T = 500μs

(a) Compute the waveform of the PAM signal s (t).

(b) Compute | S (ƒ) |, denoting the magnitude spectrum of the PAM signal s (t).

(c) Compute the envelope of | S (ƒ) |. Hence confirm that the frequency at which this envelope goes through zero for the first time is equal to (1/T) = 20 kHz.