B. DSBSC modulated signal is transmitted over a noisy channel, with the power spectral density of noise being as shown in Figure 1. The Costas receiver shown in figure 2 is used to recover the signal. (Assume: () phase shift is constant value arrange between zero to 90 degree) 1. Derive the demodulated signal at upper and lower sides 2. Determine the maximum power of the demodulated signal at upper side 3. Determine the signal to noise ratio for the demodulated signal at upper side lehanel Podut modulator Los fite Denodlatad Vitage controlled Oll Pra phase-shiter Pudct medulet Loepes Figure 1 Figure 2

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

H.W A carrier signal given by 10cos27×108t volt is FM modulatedby single tone message 4cos2nx103t voltif the modulation constantis 1000 HzlVolt a) Compute max. frequency deviation and deviation ratio. b) Write the equation of modulatedwave. c) Sketch the spectrum. d) Calculate sidebands carrierand total power.