Question
(a) Differentiate between Modulation and Demodulation. (02 marks) (b) Draw a well -labeled diagram of an FM receiver. (07 marks) (c) Explain the operation of the receiver in 2(b) (06 marks) (d) An FM system has a rated system deviation of 76kHz and this is produced by a modulating signal voltage of 10V. Determine; (i) Sensitivity of the modulator. (ii) Frequency deviation produced by a 2V modulating signal. (02 marks) (03 marks)
Solution
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Dieison
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Resposta
(a) Modulation and Demodulation:Modulation is the process of encoding information onto a carrier signal. It involves varying the characteristics of the carrier signal, such as amplitude, frequency, or phase, to represent the information being transmitted. Modulation allows the transmission of information over a communication channel.Demodulation, on the other hand, is the process of extracting the original information from the modulated signal. It involves reversing the modulation process to recover the original information. Demodulation is performed at the receiving end of the communication system to extract the information from the received signal.(b) Diagram of an FM Receiver:[Insert diagram of an FM receiver](c) Operation of the Receiver in 2(b):The operation of the receiver in an FM system involves several steps:1. Antenna: The FM signal is received by the antenna, which converts the radio waves into an electrical signal.2. Tuner: The tuner circuit filters out unwanted signals and selects the desired FM frequency. It does this by adjusting the capacitance or inductance of the circuit to match the frequency of the incoming signal.3. Amplifier: The amplifier circuit amplifies the weak signal received from the tuner to a level suitable for further processing.4. Discriminator: The discriminator circuit extracts the information from the modulated signal. In the case of FM, the information is encoded in the frequency of the signal. The discriminator converts the frequency variations into amplitude variations.5. Audio Output: The output of the discriminator is fed into an audio amplifier, which amplifies the signal to drive a speaker or headphone. The speaker then reproduces the original audio information.(d) Sensitivity of the Modulator and Frequency Deviation Produced by a 2V Modulating Signal:(i) Sensitivity of the Modulator:The sensitivity of the modulator is defined as the ratio of the modulating signal voltage to the resulting frequency deviation. It is given by the formula:Sensitivity = Modulating Signal Voltage / Frequency DeviationGiven that the rated system deviation is 76kHz and the modulating signal voltage is 10V, the sensitivity of the modulator can be calculated as:Sensitivity = 10V / 76kHz = 0.1316 V/Hz(ii) Frequency Deviation Produced by a 2V Modulating Signal:The frequency deviation produced by a modulating signal can be calculated using the formula:Frequency Deviation = Modulating Signal Voltage * SensitivityGiven that the sensitivity of the modulator is 0.1316 V/Hz, the frequency deviation produced by a 2V modulating signal can be calculated as:Frequency Deviation = 2V * 0.1316 V/Hz = 0.2632 kHz