Q4/:- For VCO-LO circuit block, if the message signal is the sine wave as shown in the figure below and the frequency carrier =520kHz 1. Calculate the frequency deviation (AF). 2. Calculate the bandwidth frequency for an FM signal.

In an AM modulator the message signal is m(t) = coswmit+2coswm2t, and the carrier wave is c(t) = Acosw.t. The modulation index is m = 0.5. a) Determine the amplitude of the carrier wave A. b) Determine the expression of the modulated signal with the AM modulation scheme. c) Determine the expression of the frequency spectrum of the AM modulated signal and then plot the frequency spectrum.

Q6. Figure Q6 shows the line spectrum of a modulated signal (all components are positive and real). 3 1 232 234 236 238 frequency/kHz Figure Q6: Line spectrum of a modulated signal (a) Describe the modulation scheme. (b) What are the values of the carrier frequency, modulation frequency and the modulation index? (c) What is the transmission efficiency (ratio of modulated to total power) in this example? (d) The reception of this signal is undertaken with a superheterodyne detector using an intermediate frequency of 110 kHz. What is the appropriate local oscillator frequency? (e) Demodulation of this type of signal is usually accomplished using an envelope detector. Describe the principles of operation of an envelope detector and sketch an example circuit. (f) What considerations should be made about the component values in the design of an envelope detector in order to demodulate the signal after shifting to the intermediate frequency? Relative unitsS

A sinusoidally modulated AM waveform is shown below: Determine: a) Peak amplitude of the upper and lower side frequencies. b) Peak amplitude of the unmodulated carrier. The modulation index. The carrier power and the power in the sidebands. The total transmitted power. 3 0 -3 -9 The transmission efficiency. The amplitude of the carrier which must be added or subtracted to attain a modulation index of 0.5. In AM modulation, the modulation index is kept < 100%, why?