Question

Electro Magnetic Interference (EMI) is normally considered as being either conductive or radiative. For each type of interference describe ways of reducing their effects. A carrier of frequency 800kHz is

being Amplitude Modulated (AM) by a modulating signal that is a sine wave at a constant frequency of 8kHz and constant amplitude. The modulation index is less than 100%. Determine the frequency of the upper sideband and lower sideband and total bandwidth of the resultant Amplitude Modulated(3 marks)waveform. If the carrier in part (b) has a peak-to-peak voltage of 10V and the modulating signal has a peak-to-peak voltage of 5V, determine the modulation index, the maximum and minimum voltages of the resultant Amplitude Modulated waveform and the peak amplitude of the upper and lower side bands. Hence, determine the modulating signal voltage that would result in 100% modulation.(7 marks) Briefly describe the process by which the modulating signal would be extracted from the Amplitude Modulated waveform at a receiver. Using the signal described in part(b) and if the demodulator comprises a simple diode detector, determine a value for the demodulator's time constant and justify your choice. Hence, determine the value of capacitance required if the resistance = 2k.(9 marks)

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