Practice Problems for Exam 1 - Communication Systems | ECE 457, Exams of Digital Communication Systems

Download Practice Problems for Exam 1 - Communication Systems | ECE 457 and more Exams Digital Communication Systems in PDF only on Docsity! ECE 457 Practice Problems for Exam 1 1. Answer the following questions briefly: a) For a message with baseband bandwidth W , the maximum transmitted bandwidth using a linear modulation scheme is ________ . b) Draw the block diagram of a system that achieves AM demodulation. c) For PM modulation, the frequency deviation is proportional to _____________. d) State briefly the operating principle of a frequency discriminator. e) The video signals in a TV system are transmitted using __________ modulation. 2. Show that a coherent demodulation scheme can be used to demodulate AM signals. Draw the block diagram and find the output at each point. 3. An angle-modulated signal with carrier frequency MHzfc 1= is described by the equation ))2000sin(1.02cos(10)( ttftx cc ππ += a) Find the power of the modulated signal. b) Find the peak frequency deviation. c) Find the peak phase deviation. d) Determine whether this signal is narrowband or wideband. e) Sketch the amplitude spectrum and estimate the bandwidth. 4. Design an Armstrong indirect FM modulator to generate an FM carrier with a carrier frequency of 96 MHz and kHzf 20=∆ . A narrowband FM generator with kHzfc 200= and adjustable f∆ in the range of 9 to 10 Hz is available. We also have an oscillator with adjustable frequency in the range of 9 to 10 MHz. There is a bandpass filter with any center frequency, and only frequency doublers are available. 5. An USB signal is generated by using the phase-shift modulator method shown in Figure 3.8. a) If the input to this system is )(ˆ tm instead of )(tm , what will be the output? b) Is this signal still an SSB signal with bandwidth equal to that of )(tm ? c) Can this signal be demodulated to get back )(tm ? If so, how?