Rajiv Gandhi Proudyogiki Vishwavidyalaya, Bhopal
New Scheme Based On AICTE Flexible Curricula
CSIT-Computer Science & Information Technology | IV-Semester
Unit-I Signals and Systems:
Block diagram of a communication system, signal-definition, types of signals continuous, discrete, deterministic, non-deterministic, periodic, non-periodic, energy, power, analog and digital signals. Electromagnetic Spectra, Standard signals- DC, sinusoidal, unit step, ramp, signum, rectangular pulse, impulse(delta) signal. System definition, classification of systems, linear, nonlinear, time variant, time invariant, causal, non causal, stable and unstable systems. Fourier transforms: Time domain and frequency domain representation of signal, Fourier Transform and its properties, conditions for existence, Transform of Gate, unit step, constant, impulse, sine and cosine wave. Shifting property of delta function, convolution, time and frequency convolution theorems.
Previous Years questions appears in RGPV exam.
Q.1) Define a signal. Explain the concepts of periodic, non-periodic, deterministic and non-deterministic signals? Provide examples for each. (June-2024)
Q.2) Find the Fourier Transform of the following function
i) Gate
ii) Unit Step
iii) Delta (June-2024)
Q.3) Explain the time convolution theorem and derive the mathematical expression of the convolution of two signals using the time convolution theorem. (June-2024)
Q.4) Explain and differentiate the following.
i) Linear and non linear system.
ii) Time invariant and time varying systems.
iii) Causal and non causal system. (June-2023)
Q.5) State and prove the following properties of Fourier Transform.
i) Time shifting
ii) Time Integration
iii) Convolution (June-2023)
Q.6) Find the Fourier transform of the function $x(t)=5t^{2}-15t$. How will be the Fourier transform be changed if this function has a period of 10 sec. (June-2023)
Q.7) Consider the following signal $f(t)=2 \sin(3t)+4 \cos(5t)+6 \sin(7t)$
i) Determine if the signal is periodic or not
ii) If signal is periodic, find its fundamental period and sketch one period of the signal.
iii) If the signal is non-periodic, explain why? (Nov-2023)
Q.8) Find the Fourier transform of an impulse function $x(t)=\delta(t)$. Also draw the spectrum. (Nov-2023)
Unit-II Amplitude Modulation:
Modulation, need of modulation, types of modulation techniques, amplitude modulation (DSB-FC), modulation index, frequency spectrum of AM wave, linear and over modulation, power relation in AM, transmission efficiency, modulation by a complex signal, bandwidth of AM, AM modulators, square law and switching modulator, advantages and disadvantages of AM. Demodulation of AM: Suppressed carrier amplitude modulation systems, DSB-SC, SSB-SC, VSB-SC systems, comparison of various amplitude modulation systems. Demodulation of AM, square law and envelope detector, synchronous detection of AM, Low and high power AM transmitters, AM receivers, TRF and superheterodyne receivers, sensitivity, selectivity and fidelity of receivers.
Previous Years questions appears in RGPV exam.
Q.1) What is the principle of Amplitude modulation? Derive expression for the AM wave and draw its spectrum. (June-2024, Nov-2023)
Q.2) Explain the operation of Tuned Radio Frequency (TRF) receiver with the block diagram and mention its advantages and disadvantages. (June-2024)
Q.3) Define suppressed carrier modulation. Explain single-Sideband Suppressed Carrier (SSB-SC) modulation with suitable diagram. What are the benefits of SSB-SC modulation over DSB-SC modulation? (June-2024)
Q.4) What is modulation and what is the need of modulation in communication system explain in detail. (June-2023)
Q.5) A conventional AM transmitter station transmits with a modulation index of 0.9. the total power transmitted is 100kW. Find out the following
i) Power carries by the carrier.
ii) The faction of the total power carrying any message
iii) Does the total transmitted power is vary with the depth of modulation? Why?
iv) Calculate total transmitted power if the modulation is 100%. (June-2023)
Q.6) A modulating signal of $2 \cos(5000t)$ is amplitude modulated over a carrier signal of $5 \cos(20000t)$. Derive the expression for modulation index, LSB and VSB frequencies, Bandwidth and the ratio of side band power in the Total Power of AM wave. (Nov-2023)
Q.7) Explain the concept of DSB-FC modulation. Discuss its advantages and disadvantages. (Nov-2023)
Q.8) Discuss the demodulation technique used for AM signals. Explain the working principle of the square law detector and envelope detector in demodulating AM signals. Compare and contrast the advantages and limitation of these demodulation techniques. (Nov-2023)
Q.9) Write a short note on the following: Superheterodyne receiver (June-2024, June-2023)
Unit-III Angle modulation:
Introduction and types of angle modulation, frequency modulation, frequency deviation, modulation index, deviation ratio, bandwidth requirement of FM wave, types of FM. Phase modulation, difference between FM and PM, Direct and indirect method of FM generation, FM demodulators- slope detector, Foster seeley discriminator, ratio detector. Introduction to pulse modulation systems.
Previous Years questions appears in RGPV exam.
Q.1) Distinguish between FM and PM by giving its mathematical analysis. (June-2024)
Q.2) A 100 M Hz carrier is frequency modulated by a sinusoidal signal of amplitude 20V and frequency 100K Hz. The frequency sensitivity of the modulator is 25K Hz/volt.
Determine:
i) Frequency deviation
ii) Modulation index $\beta$
iii) Bandwidth (June-2024)
Q.3) Discuss the operation of a Foster-Seeley discriminator as an FM demodulator with suitable diagram. (June-2024)
Q.4) A 400Hz modulating signal of voltage 2.4 Volts is modulated under FM to have a modulation index of 60. Calculate the maximum deviation and required bandwidth. (June-2023)
Q.5) Explain the wideband FM transmission. What should be the value of modulation index for it to behave as Narrow band FM. (June-2023)
Q.6) Explain ratio detector method of detection of FM signals. Give its merits and demerits. (June-2023)
Q.7) Explain frequency modulation. Derive the relation between frequency modulation and phase modulation. (Nov-2023)
Q.8) A 107.6 MHz carrier signal is frequency modulated by a 7 kHz sine wave. The resultant FM signal has a frequency deviation of 50 kHz. Determine:
i) The carrier swing of the FM signal.
ii) The highest and the lowest frequencies attained by the modulated signal.
iii) The modulation index of the FM wave. (Nov-2023)
Q.9) Explain the working principle of Foster-Seeley discriminator. Derive an expression for its output voltage and explain how the discriminator provides frequency demodulation. (Nov-2023)
Q.10) Discuss the concept of pre-emphasis and de-emphasis in FM systems. Explain how pre-emphasis and de-emphasis techniques help in improving signal quality. (Nov-2023)
Q.11) Write a short note on the following: Ratio Detector (June-2024, June-2023)
Unit-IV Sampling of signal:
sampling theorem for low pass and Band pass signal, Pulse amplitude modulation (PAM), Time division, multiplexing (TDM). Channel Bandwidth for PAMTDM signal Type of sampling instantaneous, Natural and flat top, Aperture effect, Introduction to pulse position and pulse duration modulations, Digital signal, Quantization, Quantization error, Pulse code modulation, signal to noise ratio, Companding, Data rate and Baud rate, Bit rate, multiplexed PCM signal, Differential PCM (DPCM), Delta Modulation (DM) and Adaptive Delta Modulation (ADM), comparison of various systems.
Previous Years questions appears in RGPV exam.
Q.1) State and prove Sampling theorem. (June-2024)
Q.2) Explain the elements of PCM system with a neat block diagram and also draw the waveforms. (June-2024)
Q.3) Find the signal amplitude for minimum quantization error in a delta modulation system if step size is 1 volt having repetition period 1 ms. The information signal operates at 100 Hz. (June-2024)
Q.4) Discuss the sampling and reconstruction of a low pass signal. (June-2023)
Q.5) With the help of block diagram explain the PCM communication system. (June-2023)
Q.6) Describe delta modulation system. What are its limitations? How can be overcome it. (June-2023)
Q.7) State and explain sampling theorem in time domain. Explain about Nyquist rate. (Nov-2023)
Q.8) Find the Nyquist rate and Nyquist interval for the signal $x(t)=\frac{1}{2\pi}\cos(4000\pi t)\cos(1000\pi t)$ (Nov-2023)
Q.9) Discuss the advantages and limitation of Pulse Code Modulation (PCM) as digital modulation technique. Illustrate your answer with suitable examples. (Nov-2023)
Q.10) Compare and contrast Natural Sampling, Flat top Sampling and Aperture Effect in analog to digital conversion. Explain their implication on the reconstructed signal. (Nov-2023)
Q.11) Write a short note on the following: AM and ADM (June-2024)
Q.12) Write a short note on the following: TDM (June-2023)
Unit-V Digital modulations Techniques:
Generation, detection, equation and Bandwidth of amplitude shift keying (ASK) Binary Phase Shift keying (BPSK), Differential phase shift keying (DPSK), offset and non offset quadrature phase shift keying (QPSK), M-Ary PSK, Binary frequency Shift Keying (BFSK), M-Ary FSK Quadrature Amplitude modulation (QAM).
Previous Years questions appears in RGPV exam.
Q.1) For a BPSK modulator with a Carrier frequency of 70 MHz and an input bit rate of 10 Mbps, determine the maximum and minimum upper and lower side frequencies, draw the output spectrum, determine the minimum Nyquist bandwidth, and calculate the baud (Assume $f=5MHz$) (June-2024)
Q.2) Define binary FSK and explain about the generation and detection of Binary FSK signal using block diagram. (June-2024)
Q.3) Explain the generation and receptions of BPSK system compare it with BFSK system. (June-2023)
Q.4) Discuss the generation and detection, spectrum and bandwidth of Amplitude Shift Keying. (June-2023)
Q.5) Explain DPSK. With the help of block diagram explain generation and detection of DPSK. (Nov-2023)
Q.6) Describe with the help of neat diagram, the operation of QPSK modulator. Draw its phasor and constellation diagram. (Nov-2023)
Q.7) Write a short note on the following: QAM (June-2024, June-2023)
