Question 1

An audio sound system from HUAWEI has spatial audio feature to give surrounding sound

effect. Assuming there is an audio input signal with fundamental frequency of 8 KHz and fifth

harmonics with signal strength of 1 volt and 0.5 volts respectively. It passes through the anti-

aliasing filter before it goes through the 10 bits 2's complement ADC of the system to process

the audio signal fidelity. It is being processed by the system before passes through an audio

amplifier that has a volume gain of 2 but it also produces additional 2nd and 4th harmonics at

0.05 V and 0.025 V at the output respectively.

(a)

(b)

(c)

(d)

Execute the calculation of anti-aliasing filter sampling frequency and its bandwidth.

Hence, plot the ideal bandwidth spectrum of the filter.

(5 marks)

Analyse the ADC quantization level that is required to cover the full voltage swing of

5 V peak-to-peak of the audio input signal. Hence, obtain its quantization error range

with the rounding rule being used in the ADC conversion.

(6 marks)

Analyse the ADC binary representation for an instantaneous audio input signal of

-2.2 V.

(8 marks)

Describe the audio performance through the calculation of the total harmonic distortion

(THD) at the output of the amplifier in percentage. Hence, plot the amplitude spectrum

of the output of the amplifier.

(6 marks)