a. An AM transmitter has the unmodulated carrier power of 20kW and can be modulated to a maximum of 70% before the system saturates/overloads. Find the value to which carrier power can be increased if 40% modulation limit is imposed. b. An analog communication system using FM has the highest modulating frequency of 5 kHz and maximum deviation of 25 kHz. Calculate the bandwidth of modulated signal using Carson’s rule. Compare this value with the one obtained using the simple formula. For practical systems which of these values should be used?

Problem1: the figure shows multiple modulation schemes for the signal that is given by the dashed line sinusoidal function, the X-axis is the time axis is seconds and the Y-axis is the amplitude. Answer the following: 1. What is the value of the duty cycle in A? 2.What is the quantization noise in a modulator that uses a 4-bits register for the analog to digital conversion of the given sinusoidal signal?

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?

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.

c) An audio signal 10sin 27(2000t) amplitude modulates a carrier 20sin 2π(200000t). i) ii) iii) d) How Sketch the amplitude modulated wave. Determine the modulation index? What is the frequency content of the modulated wave? AM broadenet stations. nodated in a 100 KH