S.R.M Institute of Science and Technology (Deemed University) Department of Electronics & Communication Engineering QUESTION BANK Subject Code : EC211 Subject Name : Communication Engineering Year & Sem : II Year, 3rd Sem (CSE) UNIT I PART - A 1. Define Modulation. 2. Write the need for Modulation. 3. Define Amplitude Modulation & draw its Spectrum. 4. Define Modulation Index of AM. 5. What are the different degrees of Modulation? 6. What is the power efficiency or power saving in AM, SSB, DSB-SC? 7. Write the advantages of SSB. 8. Draw the block diagram of Balanced Modulator for generating AM with carrier. 9. Give two methods of generating DSB-SC 10. Compare DSB-SC & SSB. 11. State the demerits of Square-law Modulator. 12. Give the advantages of Suppressing a carrier during transmission. 13. Compare linear & non-linear modulator. 14. Compare different AM methods. 15. Mention some applications of SSB. 16. Give the bandwidth needed to transmit AM,DSB-SC & SSB. 17. What is VSB? 18. Draw the frequency Spectrum of AM,SSB & DSB-Sc. 19. Write the expression for total power of AM in terms of carrier power Pc? 20. Define critical Modulation. 21. A transmitter supplies 8KW to the antenna when unmodulated. Determine the total power radiated when modulated to 30%. 22. A 1MHz carrier is amplitude modulated by 400Hz,modulating signal to a depth of 50%.The modulated carrier power is 1KW.Calculate the power of unmodulated signal. 23. A sinusoidal Carrier voltage of frequency 1MHz & amplitude 100 volts is modulated by sinusoidal voltage of frequency 5KHz producing 50% modulation. Calculate the frequency & amplitude of USB & LSB. 24. A 400W carrier is modulated to a depth of 70%. Find the total power transmitted for the following forms of AM signal, AM, DSB-SC, SSB.
25. Define Thermal noise & Shot noise. 26. What are the different types of noise? PART B 1. Define Amplitude modulation & derive an expression for Amplitude modulated wave. 2. Explain Balanced Modulator technique for the generation of DSB-SC wave. 3. Explain Square law method for the generation of amplitude modulation. 4. Eplain Phase Discrimination & frequency discrimination method of generation of SSB. 5. Explain the method of generation of VSB. 6. Explain Ring modulator in detail. 7. Explain any one of the linear modulator for generating AM wave. 8. Explain any one non-linear modulator for generating AM wave 9. Explain about internal & external noise. 10. Compare different methods of AM. UNIT II PART A 1. Define Demodulation. 2. Define AM detector. 3. Give the difference between low level & high level AM transmitter. 4. Define Envelope detection. 5. Draw the circuit diagram of Square law detector. 6. Define diagonal clipping. 7. What is master oscillator? 8. Why class-b power amplifier is used in low power level AM transmitter? 9. What is TRF receiver? 10. Write the advantages of TRF receiver. 11. Write the limitations of TRF receiver. 12. Define Selectivity. 13. Define Fidelity. 14. Define Super-heterodyne receiver. 15. What is intermediate frequency? 16. Define Sensitivity. 17. What is the function of mixer in super-heterodyne receiver? 18. What is the fixed value of IF in AM receiver? 19. Write the advantages of using Super-heterodyne receiver. 20. What is meant by Synchronous detection? 21. Draw the Envelope detector circuit diagram. 22. What is the effect of Phase error in Synchronous detection of DSB-SC & SSB signals?
23. What are the types of AM receiver? 24. What is low power level AM transmitter? 25. What is high power level AM transmitter? 26. What is the difference between TRF & Super-heterodyne receiver? 27. Define Multiplexing. 28. Define FDM. 29. Give the applications of FDM. 30. What is frequency drift & frequency scintillation? PART B 1. Explain the detection of amplitude modulated signal using envelope detector circuit. 2. Explain synchronous detection of DSB-SC wave & discuss about the effect of phase & frequency error. 3. Explain synchronization techniques for the detection of DSB-SC & SSB. 4. Explain about low level AM transmitter. 5. Explain about high level AM transmitter. 6. Explain synchronization technique for the detection of VSB. 7. Explain TRF receiver with a neat diagram. 8. Explain Super-heterodyne receiver with a neat diagram. 9. Explain frequency division multiplexing in detail. UNIT 3 PART A 1. Define FM and PM. 2. How FM is modulated. 3. What is the function of discriminator? 4. What is meant by diversity reception? 5. What is the difference between FM and AM receivers. 6. What the drawbacks of slope detector 7. How does Ratio detector differ from foster seely discriminator? 8. What is the use of limiter in FM receivers 9. What is IF of AM and FM system. 10. Define Super heterodyne principle. 11. What is the function of Pre-emphasis in FM transmitter and De-emphasis in an FM transmitter? 12. Difference between modulation index and deviation ratio. 13. Define double super heterodyne principle. 14. What is AFC? 15. Write the relationship between FM and PM. 16. Write the difference between narrow band FM and wide band FM. 17. Define frequency sensitivity. 18. Draw the phasor diagram of narrow band FM. 19. Define figure of merit.
20. Define capture effect in FM. 21. Define threshold effect in FM. 22. Define signal to noise ratio in FM. 23. Define phase deviation. 24. Show that a LPF can be used as a discriminator. 25. An FM signal, modulated to a depth of 8,generates a bandwidth of 180khz.calculate the frequency deviation. PART B 1. Explain Narrow band FM in detail. 2. Explain the generation of FM using Phase Modulator & generation of PM using frequency modulator. 3. Explain Armstrong method for FM generation. 4. Explain the FM generation using direct method. 5. With a neat diagram explain ratio detector in detail. 6. Explain Slope detector with a neat diagram. 7. Explain the noise in angle modulated systems. 8. Explain FM transmitter using direct method. 9. Compare AM & FM. 10. Explain FM transmitter using indirect method. 11. Explain the principles of PLL with a neat block diagram. 12. Explain FM demodulation using PLL. 13. Explain the representation of narrow band & wide band FM. 14. Explain about foster-seely discriminator in detail. UNIT 4 PART A 1. What is the advantage of digital modulation system? 2. What is PAM? 3. Define PAM, PDM. 4. Define Intersymbol interference. 5. What is eye pattern? 6. Define Companding? 7. Define TDM. 8. How synchronization is achieved in PAM 9. What are the measures taken to avoid Intersymbol interference? 10. What is pulse stuffing? 11. What is equalization? 12. Define Nyquist rate. 13. What is quantization error/noise? 14. Define Quantization. 15. Write down different types of quantizer?
16. Define sampling theorem. 17. What is aliasing? 18. Write down the advantage of PCM system? 19. What are the elements in a PCM system? 20. What is the transmission Bandwidth of PCM? 21. What are the noise in PCM? 22. Define Quantization Noise. 23. What is the advantage of using Delta Modulation. 24. What are the types of noise in Delta modulation. 25. Compare PCM and DM. PART B 1. Explain Low pass Sampling theorem. 2. Write short notes on Companding and Uniform quantization. 3. What is Quantization? Explain and derive an expression for signal to quantization noise ratio? 4. Explain TDM system with neat diagram. 5. Explain Delta Modulation System, What are the limitations? How can they be overcome. 6. Explain Adaptive delta Modulation System 7. Compare PCM, DPCM and DM. 8. With neat diagram explain the elements in a PCM system. 9. Explain ISI and what are the necessary steps taken to avoid ISI 10. Explain Equalization and explain the difference between crosstalk and interference. 11. Describe DPCM system with neat diagram. 12. What is quantization error? How does it depends upon the step size? Suggest some methods to overcome the difficulties encountered when the modulating signal amplitude swing is large. UNIT V PART-A 1. What is frequency range used for RADAR? 2. What are advantages of CW RADAR? 3. Mention any two application of CW RADAR? 4. What are the different types of RADAR systems? 5. Write the difference between pulsed RADAR and CW RADAR? 6. Discuss the RADAR range equation. 7. What are the application of RADAR? 8. What is Television? 9. What is interlaced scanning? 10.What is image scanning? 11. Mention the function of colour killer circuit in TV receiver? 12. What is aspect ratio?
13. What is the horizontal and vertical scanning frequency in India? 14. What are luminance and chrominance signals? 15. Why VSB is used for TV? 16. What is bandwidth of TV system? 17. Compare the performance of different types of camera tubes? 18. What is meant by the resolution in a TV system? 19. Draw the frequency spectrum of a TV wave. 20. Give two advantages of Satellite communication. 21. What is geostationary Satellite? 22. What are the basic components of Satellite subsystem and earth station subsystem? 23. Name some domestic Satellite. 24. Distinguish active and passive Satelite. 25. Define RADAR. 26. What is Doppler effect? 27. Draw the simple block diagram of pulse RADAR. 28. What is transponder in a Satellite system? 29. What is meant by frequency translation? 30. Specify the up and down link frequency range for Satellite communication. 31. What is need for optical fiber communication? 32. Enumerate the different types of losses in optical fiber. 33. Define Numerical Aperture. 34. Define single mode fiber. 35. What are the characteristics of LASER diode. 36. Define Attenuation of an optical fiber. 37. What are the advantages of optical fiber? 38. Define Snell s Law. 39. Classify different types of fiber. 40. What are the characteristics of LASER diode? PART-B 1. With a block diagram explain the operation of a monochrome TV receiver. 2. Describe the construction and working of a camera tubes. 3. Draw the block diagram of a colour tv receiver and describe briefly its operation. 4. Explain the principle of operation of a TV transmitter. 5. Derive an expression for RADAR range equation. 6. Explain about pulsed radar system with block diagram. 7. Explain about Satellite subsystem with neat block diagram. 8. Explain about earth station subsystem with neat block diagram. 9. Discuss on the principle of light transmission in a fiber. 10. Draw the basic block diagram of an optical fiber communication link and explain the function of various parts.