MTD205

Question 2

(a)

Given that a Macbook Pro laptop is receiving a music stream and passes this music to

an audio multiplicative mixer apple software inside the system. This music has three

signal components with frequency at Middle C note and its third and fifth harmonics

with amplitude of 3 volts, 2 volts, and 1 volt peaks respectively.

(1)

(b)

(ii)

Tutor-Marked Assignment

(ii)

Obtain the Middle C Note frequency and its respective harmonic of the music

stream where p = 60. Hence, describe the frequency spectrum for the music

stream. Hint: p = 69 + 12 log₂ (1) Hz

440

(4 marks)

The music stream passes through the multiplicative mixer apple software. It

produces various beat frequencies among each other. Explain the mixing

process by calculating the mixed and beat frequencies.

(8 marks)

(iii) Analyse through plotting the amplitude spectrum of the output of the

multiplicative mixer in Question 2(a)(ii). Clearly indicate the beat frequencies

in the plot.

(4 marks)

Given that amplitude modulation (AM) technology is being used to broadcast the audio

music stream via Wi-Fi technology. The audio modulating signal is given as b(t) =

1+8 cos(2nft) V where f is the fifth harmonics frequency in the music stream in

Question 2a (1). The carrier is given as p(t) = 5 cos(10000000000zt) V.

(1)

Derive and analyse through plotting the frequency spectrum of the modulated

signal.

(6 marks)

Determine the receiver carrier frequency used and determine the bandwidth of

the recovering filter to recover the modulating signal.

(3 marks)