Electrical Engineering Optional – Other Questions Outside the Present Syllabus (1995–2026)

These 140 questions from UPSC Electrical Engineering Optional papers (1995–2026) fall outside the present syllabus of their paper – mostly from papers set on the older syllabus. We keep them here for completeness.

Each question ends with a code such as [2024/15m/3b] – the year, the marks, the word limit (where UPSC set one) and the question number in the paper.

Paper I

35 questions

1. Explain the speed enhancement gained in MOS device by using silicon-on-sapphire or spinel (SOS). What are the other good features of the process? Mention the drawbacks. [2015/20m/4a]

2. Explain tropospheric scatter propagation. [2007/10m/4c(i)]

3. A reflex klystron operates at the peak of the n = 2 mode. The dc power input is 40 mW and $V_1/V_0=0.278$. If 20% of the power delivered by the beam is dissipated in the cavity walls, find the power delivered to the load. Assume ${\beta }_1=1$ and $J_1\left(1.53\right)=0.562$. [2007/10m/4c(ii)]

4. List the differences between microwave transistors and transferred electron devices. [2007/10m/5d(i)]

5. Explain the structure of IMPATT diode. [2007/5m/5d(ii)]

6. Compare linear broadside arrays having uniform, binomial and Dolph – Tchebyscheff distributions. [2007/10m/6c(ii)]

7. Show that the radiation resistance of a small loop antenna is $31200{\left(A/{\lambda }^2\right)}^2$ ohm. [2007/20m/7c]

8. The ionosphere can be considered as a dielectric with refractive index n. Derive an expression for n. [2006/20m/4c]

9. A magnetic field strength of 15 μA/m is required at a point on $\theta =\pi /2$ [?], 2 km from an antenna in air. Neglect ohmic loss. How much power would the antenna transmit if it is (1) a $\lambda /2$ dipole? (2) a 10 turn loop [?] antenna of radius $\lambda /20$? [2006/10m/5d(ii)]

10. Draw a neat schematic of a traveling-wave amplifier. List the elements of the tube and their constructional details. [2006/10m/6c(i)]

11. Compare the salient features of O- and M-type tubes. (at least eight points) [2006/10m/6c(ii)]

12. Draw a simple two-valley conduction band diagram for GaAs. The band structure of a semiconductor must satisfy three criterions to exhibit negative resistance for transferred electron effect to occur. State them. [2006/10m/7c(i)]

13. With the help of neat sketches explain the fabrication steps for making MOSFETs. [2006/10m/7c(ii)]

14. Show that the first minor lobe is $-13.5$ dB to principal maxima for broadside array for large n. [2005/10m/1d(iii)]

15. Explain Faraday rotation isolator. A matched isolator has insertion loss of 0.5 dB and isolation 25 dB, Calculate the scattering coefficient. [2005/15m/4c(i)]

16. Explain construction of Ionosphere. [2005/5m/4c(ii)]

17. Describe transmission & radiation modes of helix. [2005/5m/5d(iii)]

18. Explain the term ‘virtual height’ with respect to ionospheric transmission. Calculate the transmission-path distance for an ionospheric transmission that utilizes a layer of virtual height 200 km. The angle of elevation of the antenna beam is 20°. Consider flat earth. [2005/10m/6c(i)]

19. Explain the different input statements in SPICE. [2005/5m/7a(i)]

20. Draw and explain construction details of reflex klystron. Explain electronic tuning. [2005/10m/7c(i)]

21. A helix travelling wave tube operates at 4 GHz with a beam voltage of 10 kV and a beam current of 500 mA. The helix impedance is 25 ohm and interaction length is 15 cm [?]. Determine the output power gain in dB. [2004/10m/1d(ii)]

22. What is troposphere? State the parameters that characterise troposphere. Write empirical formulae for the variation of these parameters within the first 1 – 2 km of the troposphere. Write expressions for the permittivity (${\epsilon }_r$) and refractive index (n) of the tropospheric medium. What is the value of n at an altitude of 1 km? [2004/20m/4c]

23. A paraboloidal reflector antenna of cross-sectional area of 8000 cm² works at 3 GHz. Calculate the (i) beam width between first nulls, (ii) half power beam width, and (iii) gain of the antenna. [2004/20m/5d]

24. Find the field strength at distances of 500 m and 2,500 m from a dipole centre fed with $I_m=0.1$ A. Dipole has a length of 200 cm and the frequency of operation is 3 GHz. Consider $E_{\theta }$ only in the maximum direction. [2004/20m/7c]

25. Show that the field strength at a point close to the antenna (at distances of unto 200-300 miles from the transmitting antenna) in terms of the power is given by $\epsilon =\frac{9.49\sqrt{P}}{r}\mathrm{\text{volts/m}}$ Where: $\epsilon$ is the field strength in volts/m, P is the power radiated in watts, r is the distance in meters. Calculate the field strength at 20 km away from a transmitting station of 50 kW power. [2003/20m/4b]

26. Define directive gain and directivity of an antenna. The radiation intensity of a certain antenna is $U(\theta ,\varphi )=\left[\begin{array}{cc}\hfill 4sin\theta {sin}^3\varphi \hfill & \hfill 0\le \theta \pi ,0\le \varphi \le \pi \hfill \\ \hfill 0\hfill & \hfill \mathrm{\text{elsewhere}}\hfill \end{array}\right]$ Determine the directivity of the antenna. [2002/20m/4b]

27. What is a Hertzian dipole? Find the radiation resistance of a Hertzian dipole. [2002/20m/5d]

28. A transmitting antenna at a height of $h_2$ above a smooth perfectly flat-earth surface sends a signal to a receiving antenna of height $h_1$ with ground range between them equal to a. Obtain the path difference between the direct and reflected signals reaching the receiving antenna. Assume $h_2>h_1$. [2001/20m/6c]

29. Obtain relationship between the skip distance and maximum usable frequency over the flat earth surface. [2001/20m/7c]

30. .

(i) What factors influence the performance of Yagi–Uda antenna? Explain it clearly with the help of a neat sketch showing the direction of e.m.w. [2000/10m/1d(i)]

(ii) Determine field strength at a distance of 50 kin of a short vertical monopole radiating power of 20 kW at a frequency 1 MHz over ground with mean conductivity of 10 mS/metre [2000/10m/1d(ii)]

31. What is the difference between TWT and Klystron? How TWT operates as microwave oscillator? Determine (i) the gain parameter; (ii) the power gain, and (iii) any two propagation constants in a traveling wave tube having the following parameters Beam voltage $V_0=2$ kV Beam current $I_0=20$ mA Frequency f = 10 GH Characteristic impedance of helix $Z_0=10\Omega$ Circuit length = 50 (wavelength) [2000/20m/4c]

32. .

(i) Derive relationship between critical frequency and the maximum density of a layer N. [2000/10m/6c(i)]

(ii) Calculate skip distance for a wave of frequency 4.5 MHz when the maximum ionization in the E – region has value of ${10}^{10}electrons/m^3$ at a height of 105 km. [2000/10m/6c(ii)]

33. .

(i) A n-type GaAs Gunn diode of length 10 μm, doping concentration $2\times {10}^{14}/m^3$ and threshold field 3 kV/cm operates at a frequency of 10 GH with applied voltage of 3.5 kV/cm. Calculate electron drift velocity, current density and negative mobility of electron. [2000/10m/7b(i)]

(ii) A circular loop of 20 cm radius made of 3 mm dia. of copper wire is used as an antenna. Calculate its radiation resistance. ohmic resistance, input resistance and radiation efficiency at 1 MHz. [2000/10m/7b(ii)]

34. Describe, giving reasons, the choice of materials for the following applications: (i) Magnetic tapes (ii) Recording heads (iii) Super conductors (iv) Insulation for 11 KV cable. [1999/20m/7b]

35. An infinitesimal dipole (Hertzian) antenna of 1 cm length radiates a power of 1 mW at 100 MHz. Calculate (i) the current in the dipole, (ii) E and H fields at 100 meters. $\varphi ={90}^{\circ }$, $\varphi =0^{\circ }$ [1998/20m/5d]

Paper II

105 questions

1. Colour sub-carrier (3.58 MHz for FCC standard and 4.43 MHz for CCIR standard) is chosen as some odd multiple of one-half of line frequency. Justify the statement. [2007/20m/1d]

2. Explain the sea waves phenomena and vortex motion of waves. Discuss the principles of two possible devices used for generating electrical energy from the wave energy. Draw the block diagram from wave energy device to utility grid. Write the relation for the potential power in terms of height of wave and its time period. If the time period of a wave is 10 secs having height 7 meters, estimate the power that can be generated. [2007/20m/2c]

3. How is the surface layer of silicon dioxide formed? How thick is this layer? What are the reasons for forming the silicon dioxide layer? [2007/20m/3a]

4. With the aid of a block schematic, describe the functioning of the receiving unit of a DBS TV/FM receiving system intended for home reception. [2007/20m/4b]

5. Consider an optical fiber with refractive index of the core 1.8 and of cladding 1.7; calculate: (i) Critical angle (ii) Acceptance angle (iii) Brewster angle (iv) Numerical aperture. [2007/20m/4c]

6. What do you understand by dielectric films? State any two dielectric film material and point out their important properties and applications. Explain (i) the orientation polarization, (ii) electronic polarization; and (iii) ionic polarization referred to polyatomic gas. Discuss the effect of frequency on electronic polarization and ionic polarization. What is electronegative gases? State the important features of SF6 and its applications. [2007/20m/5a]

7. Why and to what degree do optical signals get degraded as they propagate along a fiber? Discuss in detail. [2007/23m/6c]

8. Draw the waveform at the end of one of the vertical fields, showing a horizontal and a vertical blanking pulse. Indicate the duration and relative amplitudes of two pulses and explain their functions. Where are synchronizing pulses placed? Does it matter that there are no horizontal blanking pulses during vertical blanking period? [2007/23m/7c]

9. State and explain principle of Magnetio Hydro Dynamics (MHD) generation, Draw a block diagram of close cycle MHD system and explain operation of the system. State the advantages of MHD generation over other methods of electric generation. An ideal MHD generator using gas as working fluid has the following data:

Electrode Area	$0.2m^2$
Distance between electrodes	24 cm
Magnetic Flux density	$1Wb/m^2$
Conductivity of gas	50 Siemens/m
Gas velocity	1800 m/s

Find: (i) Output voltage, power and efficiency at a loading factor of 0.7. (ii) Open circuit voltage and short circuit current. (iii) Maximum power output. [2006/20m/2c]

10. How are diodes realized in integrated circuits using transistor structures? Describe and compare the three most popular diode structures with diagrams. [2006/20m/3a]

11. What is meant by eccentricity, semi-major axis, apogee and perigee? The cosmos 1675 satellite has an apogee height of 39, 342 kms and a perigee height of 613 kms. Determine the semi-major axis, and the eccentricity of its orbit. Assume the mean earth radius of 6371 kms. [2006/20m/4b]

12. Summarize the attractive attributes and limitations of phased array radar. [2006/20m/4c]

13. In a single mode fibre the waveguide dispersion can cancel the material dispersion making intra modal dispersion zero over a small range of wavelength. Comment. The wavelength range is around 1.3 μm. [2006/20m/5d]

14. Discuss the phenomenon of superconductivity. What is ‘critical-field’ in a superconductor? How it is affected by temperature? Write the functional relationship. Write application of a superconductor as an electrical switching element. [2006/20m/6a]

15. Discuss how a CW radar extracts the Doppler frequency shift from a moving target with the stationary clutter echoes rejected. [2006/20m/6c]

16. Discuss the processes involved in realizing the epitaxial growth, masking and etching for the fabrication of integrated circuits. [2006/20m/7a]

17. What are the considerations for choice of the differentiating and the integrating circuit used for separating the H and V sync pulses? Discuss with schematic and waveforms; how is ripple reduced at the integrating circuit. [2006/20m/7b]

18. Consider a Fabry Perot Laser diode made of InGaAsP with refractive index = 3.5 If the gain profile is $g\left(\lambda \right)=g_0{e}^{-{(\lambda -{\lambda }_0)}^2/{\sigma }^2}$ [?] (i) With $g_0=1500m^{-1}$, $\sigma =10$ mm and distributive cavity loss, $\alpha =1000m^{-1}$ find the lower limit of cavity length for lasing. (ii) If the cavity length, L = 2000 μm, $\alpha =500m^{-1}$ and ${\lambda }_0=1.5$ μm, find the number of longitudinal modes in the output of the laser. [2006/20m/7c]

19. Select any three of the following statements, read them carefully and identify the correct and the incorrect ones. Justify your answer using not more than 200 words in each case. 2:1 interlace ratio is used for interlaced scanning in television systems. [2005/20m/200w/1d]

20. Sketch and discuss the fabrication of a planar transistor made for monolithic integrated circuits using epitaxy and diffusion with that of a discrete planar epitaxial transistor. [2005/20m/3a]

21. The relevant data for closed-circuit TV system is given below. Calculate the highest modulating frequency that will be generated while scanning alternate black and white dots for equal vertical and horizontal resolution. Data: Number of lines = 250, Interlace ratio = 1:1, Aspect ratio = 4:3, Picture repetition ratio = 50 per second, Resolution factor = 0.8, Vertical retrace time = 10% of picture frame time, Horizontal retrace time = 20% of total line time. [2005/20m/4b]

22. With the aid of a block diagram, explain the operation of FMCW radar altimeter. [2005/20m/4c]

23. Select any three of the following statements, read them carefully and identify the correct and the incorrect ones. Justify your answer using not more than 200 words in each case. Electrical isolation different elements of a monolithic integrated circuit is obtained by creating isolation islands. [2005/20m/200w/5b]

24. Select any three of the following statements, read them carefully and identify the correct and the incorrect ones. Justify your answer using not more than 200 words in each case. Transmission links using optical fibres need components with specific characteristics to fulfill the system requirements. [2005/20m/200w/5d]

25. Calculate the apogee and perigee heights for the orbital parameters given Eccentricity = 0002, Mean Earth’s radius = 6378 km, Mean distance to the semi-major axis = 7100 km. [2005/20m/6c]

26. Distinguish between (i) spontaneous and stimulated emission, (ii) step index and graded index optical fibre. [2005/20m/7a]

27. What is wave energy? Explain the difficulties facing wave-power development. Give a list of devices developed for converting wave energy into electrical energy and fully describe one of these. [2004/20m/2c]

28. Describe the various steps involved in the fabrication of a monolithic circuit shown below:

[Figure: Terminal 1 connected to node X; a resistor from node X up to terminal 2; node X also connected to the base of an NPN transistor whose collector goes to terminal 3 and whose emitter (arrow outwards) goes to terminal 4.] [2004/20m/3a]

29. A CW radar operates at a frequency of 10 GHz. What is the doppler frequency produced by (i) an aeroplane flying at a speed of 250 kms per hour (ii) a man crawling at a speed of 2.5 cms per second? [2004/20m/4b]

30. The guided missile tracking radar operates at 5 GHz and a 1.0 MW peak power output. If the antenna diameter is 4 meters, the receiver band-width 1.6 MHz and the receiver has a 10 dB noise figure, what is its maximum detection range for 1 m² targets? [2004/20m/4c]

31. Select any THREE of the following statements, read them carefully and identify the correct and the incorrect ones. Justify your answer using not more than 200 words in each case:- Capacitors in integrated circuits are obtained by using the transition capacitance of a reverse-biased pn junction. [2004/20m/200w/5b]

32. Select any THREE of the following statements, read them carefully and identify the correct and the incorrect ones. Justify your answer using not more than 200 words in each case:- Do we have a system which makes a fuller utilization of the transmission capacity of an optical fibre and needs multiplexing? [2004/20m/200w/5d]

33. State Kepler’s three laws of planetary motion. Illustrate in each case their relevance to artificial satellites orbiting the earth. [2004/20m/6c]

34. How I, Q and Y signals are generated in a colour TV transmitter? Explain with tube and matrix arrangement. [2004/20m/7b]

35. Select any three of the following statements, read them carefully and identity the correct and the incorrect ones. Justify your answer using not more than 200 words in each case: Considering state of the art, the communication links of satellites for weather forecasting are at present very effective. [2003/20m/200w/1d]

36. Describe a few features of a wind wheel for efficient generation of electrical energy and discuss economic viability of this form of energy vis-a-vis conventional method. Which generator do you recommend and why? [2003/20m/2c]

37. What is solar power? Describe very briefly with neat diagram the scheme for (i) residential cooling and heating and (ii) solar power plant, using solar energy. [2003/20m/3c]

38. Explain what is meant by saying that a satellite is stationary. Why are such satellites used for worldwide communications in preference to any other kind? [2003/20m/4c]

39. Select any three of the following statements, read them carefully and identify the correct and the incorrect ones. Justify your answer using not more than 200 words in each case The magnetic property of a material is completely lost above its characteristic Curie temperature. [2003/20m/200w/5b]

40. Explain the significance of blind speed in moving target indicator (MTI) by radar. A MTI operates at 5 GHz with a pulse repetition frequency (PRF) of 400 pps. Calculate the lowest blind speed of radar. [2003/20m/6c]

41. Describe radar beacons and their application. [2003/20m/7b]

42. What do you mean by bandwidth of single mode fibre and describe the factors on which it depends? [2003/20m/7c]

43. Explain the terms energy management, energy audit and energy economics. Explain how these techniques can be used to improve the performance of an energy starved inter connected power system. [2003/20m/8c]

44. Select any three of the following statements read them carefully and identify the correct and the incorrect ones. Justify your answer using not more than 200 words in each case A satellite earth station must have as many receive chains as there are carriers transmitted to it. [2002/20m/200w/1d]

45. Explain clearly the construction of a p-n junction and its use to convert sun-light directly into electricity. What distinguishes a solar cell from a conventional p-n junction diode? [2002/20m/2c]

46. What is wave power? Describe some of the devices used for converting wave power into electrical power. Discuss briefly its feasibility with reference to Indian sub-continent. [2002/20m/3c]

47. Differentiate between para-magnetic, diamagnetic and ferro-magnetic materials. Discuss various factors which affect permeability and hysteresis loss. [2002/20m/4a]

48. Explain how television is capable of displaying complete moving pictures, despite the fact that at any instant of time, only a tiny portion of the picture tube screen is active. [2002/20m/4b]

49. How do the functions of a communication satellite compare with those of a microwave link repeater? What is the most significant difference in their functions? [2002/20m/4c]

50. Select any three of the following statements, read them carefully and identify the correct and the incorrect ones. Justify your answer using not more than 200 words in each case “Tan δ” of an insulating material is an indication of its health. [2002/20m/200w/5b]

51. Derive a simple expression for the orbital period of a satellite in terms of the mechanical constants of the satellite and the earth. [2002/20m/7b]

52. A multimode fiber has a core refractive index 1.5 and the relative refractive index difference is 3 per cent and the operating wavelength is 0.8 in. Calculate the critical radius of curvature at which large bending losses occur. [2002/20m/7c]

53. Discuss one scheme each of (i) constant speed constant frequency (CSCF) (ii) variable speed constant frequency (VSCF) of a wind-electrical energy conversion system. [2002/20m/8c]

54. Select any THREE of the following statements, read them carefully and identify the correct and the incorrect ones. Justify your answer using not more than 200 words in each case. For the correct reproduction of the picture on the screen of a television, it is desired that the scanning at the receiver and transmitter are synchronized. [2001/20m/200w/1d]

55. Calculate the maximum power by a solar cell at an intensity of $200W/m^2$. Given $V_{max}=0.14$ V and $I_{max}=-6$ mA. Also calculate the cell efficiency if the area is $4c{m}^2$. [2001/20m/3c]

56. While manufacturing IC, the Si wafer is oxidized time and again. What functions can an oxide layer perform during and after the manufacture? What role is played by dislocations which get generated during the growth of the single crystal and during processing of the wafer? [2001/20m/4a]

57. Explain, what is meant by the term Blind Speed in MTI (Moving Target Indicator) radar. What is the method of overcoming the problems of blind speed in radar? [2001/20m/4b]

58. What do you understand by the term Satellite Communication Package? Explain in brief the working of satellite repeaters in use. [2001/20m/4c]

59. Select any THREE of the following statements, read them carefully and identify the correct and the incorrect ones. Justify your answer using not more than 200 words in each case. Using energy audit and energy management techniques, one avoid or postpone the installation of costly peaky generation. [2001/20m/200w/5c]

60. Select any THREE of the following statements, read them carefully and identify the correct and the incorrect ones. Justify your answer using not more than 200 words in each case. In pulse compression radar, one gets a higher maximum range capability and a better range resolution. [2001/20m/200w/5d]

61. With reference to the colour television transmission and reception, explain (i) hue and saturation, and (ii) colour subscriber. [2001/20m/6c]

62. Discuss the effect of temperature on the relative dielectric constant of a material. [2001/20m/7a]

63. The semi-major axis and the semi-minor axis of an elliptical satellite orbit are 25000 km and 20000 km respectively. Determine the apogee and perigee distances. [2001/20m/7b]

64. Explain; how energy is lost at a sharp bend in a fibre. What do you understand by the term Dispersion, as applied to optical fibre? [2001/20m/7c]

65. Select any three of the following statements, read them carefully and identify the correct and the incorrect ones. Justify your answer using not more than 200 words in each case. Optical fibre is the best choice for heavy demand long line telephone communication systems. [2000/20m/200w/1d]

66. Boron is doped in n-type Si wafer having $2\times {10}^{22}$ phosphorus atoms $m^3$ through a circular window of 0.1 μm diameter for 10 minutes at 1100° C The gaseous atmosphere of $B{H}_3$ used for doping provides the B concentration of $1\times {10}^{23}$ atoms $m^3$ at the surface of the wafer Estimate the location of the p-n junction beneath the surface. Given the diffusivity of B in Si at 1100°C is $4\times {10}^{-17}{m}^2{s}^{-1}$. [2000/20m/3a]

67. What are solar concentrators? Describe various components of a solar concentrator giving their functions. [2000/20m/3c]

68. Explain with the help of block diagram a CW Doppler radar using an intermediate frequency in the receiver. Give its advantages applications and limitations. [2000/20m/4c]

69. Select any three of the following statements, read them carefully and identify the correct and the incorrect ones. Justify your answer using not more than 200 words in each case. The cost of fabrication and installation of system for utilizing solar energy is too high to be viable. [2000/20m/200w/5c]

70. Select any three of the following statements, read them carefully and identify the correct and the incorrect ones. Justify your answer using not more than 200 words in each case. ICs, although cheaper, are less reliable as compared to discrete components interconnected by conventional techniques. [2000/20m/200w/5d]

71. Discuss salient features of a fibre optic communication system. List some of the optical components used to interconnect a digital voice or data systems. [2000/20m/6c]

72. Discuss multiple access techniques for satellite communications. Explain the meaning of the following FDMA, TOMA, COMA and SOMA. [2000/20m/7b]

73. Briefly describe two different types of phase array radars. How can phased arrays overcome the difficulties occasioned by the use of moving radar antennae? [2000/20m/7c]

74. Select any three of the following statements and indicate with justification whether they are correct or incorrect. Your answer must not exceed 200 words for each statements: The transposition of telephone lines is desirable. [1999/20m/200w/9b]

75. Select any three of the following statements and indicate with justification whether they are correct or incorrect. Your answer must not exceed 200 words for each statements: Magnetrons are capable of delivering low pulsed power output. [1999/20m/200w/9c]

76. Select any three of the following statements and indicate with justification whether they are correct or incorrect. Your answer must not exceed 200 words for each statements: Only one kind of dielectric substrate is used in microwave integrated circuits (MICs). [1999/20m/200w/9d]

77. Discuss the microwave spectrum in satellite communication. [1999/10m/10b]

78. Discuss the realization techniques, with circuit diagrams, for inductor and capacitor in microwave communication. [1999/20m/11a]

79. Derive the equivalent circuits and find out ‘Q’ factor of the inductor and capacitor. State any assumptions made. [1999/20m/11b]

80. Describe the relative merits of single mode and multimode fibres used in communication system. [1999/20m/12a]

81. Discuss the significance of G/T ratio of an earth station. [1998/20m/12a]

82. Give the frequency range of a gunn diode and order of available power. How many junctions does it have? [1998/20m/12b]

83. Describe a DME system for measurement of distance. [1998/20m/12c]

84. An electric train has an average speed of 42 kmph on a level track between stops 1400 m apart. It is accelerated at 1.7 kmphps and is broken at 3.3 kmphps. Draw the speed-time curve for the run. Estimate the energy consumption at the axle of the train per ton km. Take tractive resistance constant at 50 N/ton and allow 10 per cent for rotational inertia. [1997/20m/8a]

85. Select any three of the following statements and indicate with justification whether they are correct or incorrect. Your answer must not exceed 200 words for each statement. VHF band is most suited for communication between a ship and a submarine. [1997/20m/200w/9a]

86. Select any three of the following statements and indicate with justification whether they are correct or incorrect. Your answer must not exceed 200 words for each statement. Round trip propagation time with geostationary satellites is very large and poses a peculiar problem for telephone service. [1997/20m/200w/9b]

87. Select any three of the following statements and indicate with justification whether they are correct or incorrect. Your answer must not exceed 200 words for each statement. Colour, television transmitter has to transmit more information than black and white but has to mange within the same bandwidth. [1997/20m/200w/9c]

88. An MTI radar operating at 6GHz is having a PEW [?] of 900 pps. Find the two lowest blind speeds for this radar. [1997/20m/10a]

89. A silica fibre has a large core diameter. The refractive indices of core and cladding are 1.49 and 1.46 respectively. Find the NA of the fibre, the acceptance angle in air and the critical angle at the core-cladding interface. [1997/20m/10c]

90. What is a three-port circulator? Write its S-matrix. One of the ports of such a circulator is terminated in a load having a reflection coefficient $\rho$. If the system is now viewed as a two-port at the other pair of ports, find the scattering matrix of the two-port. [1997/20m/11b]

91. A deep space probe radar operating at 3 GHz is using a 64 m dish and peak pulse power of 20MW. The receiver noise figure is 1.0 dB, the target cross section is 1.5 $m^2$ and the receiver bandwidth 8kHz. Find the maximum range under threshold detection conditions. Take antenna noise temperature to be 290K. [1997/20m/11c]

92. A broadside antenna array has 20 identical radiators, equally fed and spaced 1/2 apart. Find the directivity of the array and express it in decibels. [1997/20m/12c]

93. Explain the principle of electric welding. Describe with the help of a neat diagram the principle of operation of a timer circuit used for electric welding. [1996/20m/4b]

94. Explain the principle and applications of (i) induction heating, and (ii) dielectric heating. Discuss the range of frequencies used in these systems of heating. [1996/20m/8a]

95. Select any three of the following statements and indicate with justification whether they are correct or incorrect. Your answer must not exceed 200 words for each statement. The conical scanning method of tracking an acquired target is an improvement over lobe switching. [1996/20m/200w/9d]

96. Give the properties of paraboloid reflectors. Explain why an antenna using a paraboloid reflector is likely to be a highly directive receiving antenna. Describe the Cassegrain method of feeding a paraboloid reflector. Give some shortcomings and difficulties associated with the method. [1996/20m/10c]

97. (i) What is meant by saying that colour TV must be compatible? (ii) Explain what is meant by the Y, I and Q signals in colour TV, and why they are generated. With the help of circuit diagram of a simplex matrix, explain how the I, Q and Y signals are generated in a colour TV transmitter. [1996/20m/11b]

98. Give the advantages and disadvantages of submarine cables and communication satellites for intercontinental telephone and television. Show how the two media may be complementary. Explain what is done to ensure that intercontinental telephone calls are not misrouted. [1996/20m/11c]

99. With the help of a schematic diagram, explain a four-cavity klystron amplifier. A four-cavity klystron amplifier has the following parameters: Beam voltage: $V_0=20$ kV Beam current: $I_0=2$ A Operating frequency: $f=10$ GHz d.c. charge density: ${\rho }_0={10}^{-6}C/m^2$ RF charge density: $\rho ={10}^{-8}C/m^2$ Velocity perturbation: $v={10}^5$ m/s Determine (i) The d.c. electron velocity (ii) The d.c. phase constant (iii) The plasma frequency (iv) The reduced plasma frequency for $R=0.5$ (v) The d.c. beam current density (vi) The instantaneous beam current density. [1996/20m/12b]

100. A slab of material 2.5 cm thick and 200 sq. cm in area, having relative permittivity 5 and 0.05 is to be heated using dielectric heating. The power required is 200 watts at a frequency of 30 MHz. Determine the voltage required and the current that will flow through the material. If the voltage were to be limited to 600 V, what should be the frequency for the same power requirement? [1995/20m/4c]

101. Discuss various types of electric traction used in India. Explain the characteristics of the motor used in any one such system. [1995/15m/8a]

102. Select any three of the following statement and indicate with justification whether they are correct or incorrect. Your answer must not exceed 200 words for each statement. An ideal directional coupler must have infinite directivity. [1995/20m/200w/9b]

103. Select any three of the following statement and indicate with justification whether they are correct or incorrect. Your answer must not exceed 200 words for each statement. Telecommunication carriers can increase the utilization of their existing cable ducts significantly if fibre-optic cables are substituted for copper. [1995/20m/200w/9c]

104. Discuss the advantages and list applications of parametric amplifiers. Draw the circuit diagram of a TW parametric amplifier and explain briefly how it works. [1995/20m/11c]

105. Compare and contrast the performance and advantages of co-axial cable and microwave links as broad band ‘continental’ transmission media. Draw and explain block diagram of a microwave link carrier chain. [1995/20m/12a]

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Last updated: 30 October 2026