D- Jayakumar Ece Ece Ece Viva Questions-jk

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VIVA QUESTIONS DEPARTMENT OF ELECTRONICS & COMMUNICATION ENGINEERING VIVA- QUESTIONS-ANSWER

1. Define Rectifier? Rectifier is a Electronic circuit which converts Alternating signal into pulcating D.C 2. Define Full wave Rectifier? This rectifier consists of center rapped transformer and two diodes. The center tap is grounded. [i.e] it’s potential is maintained at Zero. 3. Define construction of Full wave Rectifier? The Anodes of diode1 and diode2 are connected to the terminal A and B of the transformer secondary respectively. The cathode of 2 diodes connected to the load. 4. What are the merits of Full Wave Rectifier? Ripple factor is low when compared to the Halt Wave Rectifier. 5. What is the major disadvantages of Full Wave Rectifier? Here center tapped transformers are used so, the cost in high. 6. what are the futures of Full Wave Rectifier [center-tap]? Efficiency – 81.2% Ripple factor 0.48 PIV 2vm. Output frequency 2fin. Diodes 2. 7. Define Photo diode? It is one of the junction Photo conductive devices. 8. Define Photo – conductive effect? When incident light falls on the surface of a semi – conductor, some adsorption of light by the semi – conductor results in generation of carriers resulting in increase of the conductivity. This effect is known as Photo conductive effect. 9.What are the two types of junction ? (i) Photo diode. (ii) Photo transistor 10.What are the devices that fall on the category of Bulk Photo – conductive devices. LDR, thermistor and sensistor. 11.What are the Applications of Photo diode? 1.Light detection system. 2.As an optical coupler. 3.Light operated switch. 4.Encoder. 5.Modulcation.

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12. Define semi-conductor diode? When we join a piece of ‘P’ material and ‘N’ material, so that the crystal structure remains continuous at the boundary. PN junction is formed. It is called a semi-conductor diode. 13. Define Depletion layer? A layer in which there is no free charge carriers. It consists of only uncompensated acceptor and donor ions. 14. Define knee voltage? Knee voltage is the voltage at which the diode starts conducting. 15. What is the Knee voltage for silicon and germanium? Si = 0.6v s Ge = 0.2v 16. What are the other names of knee voltage? (i) threshold voltage. (ii) cut-in voltage. (iii) offset voltage. 17. What are the other names of Depletion region? (i) space charge region. (ii) ionic region. 18. Why diode is called a uni-directional device? Because it conducts current in Forward direction only. 19. What is meant by Reverse saturation current? During reverse biasing, the reverse current produced by minority carriers is called Reverse saturation current. 20. What are the application of diodes? Diodes are used in rectifier, regulator, clipper, clamper, detector, etc..., 21. What is the other name of point contact Diode? Cut wisker diode. 22. What is transistor? A semi-conductor arranged in particular way offers low resistance to the flow of current in one portion while. Thigh resistance is offered in another portion. This kind of arrangement of a semiconductor is termed as transistor. 23. Why do we call transistor as a bi-polar component? Transistor is called as a bi-polar component because it is operation depends on both majority and minority carriers. 24. Why do we call transistor as a transfer resistor? Because, It transforms current from low resistance path to high resistance path. 25. What are the types of transistor? Two type: (i) Point contact (It is defective now it is out of use). (ii) Junction transistor (It is used now-a-day). 26 How many terminals are there in transistor, what are they? Define the function of that? Terminals : D. Jayakumar

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i. Emitter : It is more havily doped than any other regions. Because it is main function is to supply majority carriers [either ē or holes] to the base. ii. Base : It is lightly doped. It is main function is to control the flow of majority carriers from emitter to collector. iii. Collector: It is main function is to collect majority carriers through the base. In most of the transistors. collector region is made physically larger than emitter region. Because it has to dissipate much greater power. 27. What are the types of junction transistor? 1. NPN – In this current conduction is by electrons. 2. PNP – In this current conduction is by holes. 28. Define “Common Emitter”? In this Emitter terminal is common for both Input and Output (i.e) the input is applied between base and emitter and the output is taken from collector and emitter. 29. Output characteristics of CE – Define? It gives relationship between collector to Emitter voltage and collector current keeping base current constant. 30. Define input characteristics of CE configuration? The relationship between base-emitter voltage and base aments keeping VCE kept constant gives the input characteristics. 31. What are the characteristics of CE config? (i) Input resistances and output resistances are medium valve. (ii) Arrent gain, voltage gain and power gains are high. Hence, this config, is preferred anang the three. 32. Define Saturation, Active, Cut-off, Inverted regions? Active region : Emitter base junction is Forward biased Collector base junction is Reverse biased. Saturation region : Both the emitter-base junction and collector-base Junctions are forward biased. Cut-off region : Both the emitter-base junction and collector-base junctions are reverse biased. Inverted region : Emitter base junction is Reverse biased and collector base junction is Forward biased. 33. Define reverse leakage current? A leakage current in a transistor due to the flow of minority carriers. It is propotional to the temperature. Hence it is temperature dependent. 34. What is the main dis-advantage of CE config? It has very high leakage current. 35. What are the application of CE config? This config is preferred for Amplifier circuit because, it has a phase of 180° from Input to output and it has a high power gain than CB and CE. 36. What are the ideal characteristics of op - amp? 1. High voltage gain 2. High input impedance 3. Low output impedance 4. High Bandwidth 5. High CMRR(Common Mode Rejection Ratio) 37. What is meant by inverting and non-inverting terminal? The word inverting implies that if the signal is applied to the ‘-‘ terminal of the op-amp, it appears with the opposite polarity at the output (i.e) a sinusoidal signal will experience a phase shift D. Jayakumar

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of 180′. The inverting terminal implies that the signal applied to this terminal of the op-amp is amplified without inversion. 38. What is meant by differential amplifier? The input circuit of the op-amp, which is driven by inverting and non-inverting inputs, is called a differential amplifier. 39. What is the gain of the op-amp? The ideal op-amp have infinite gain but in practical op-amp the gain falls short of the infinite value. The gain is expressed in decibels. Av(dB) = 20 logV2/V1 Where V2-Inverting terminal input V1-Non-Inverting terminal input 40. What is the input resistance of op-amp? This is the differential input resistance as seen at either of the input terminals with the other terminal connected to ground. Ideally the input resistance of an op-amp is infinitely high. But for 741IC, its value is 2Mohms. But ,in practice ,its value is 250kohms and 40kohms for op-amps with bipolar transistor and 10^12ohms for the op-amps with FET input. 41. What is the value of output resistance? It is the resistance measured between the output terminal of the op-amp and the ground. But for 741c IC,its value is 75 ohms. Practical op-amps have the output resistance of the order of 100ohms. 42. What is CMRR? The signal applied to both the inputs is called as common mode signal. The ability of an op-amp to suppress common mode signals is expressed in terms of its common mode rejection ratio (CMRR). Mathematically the common mode rejection ratio is given by the relation, CMRR =( Differential voltage gain / Common mode voltage gain) = Adm/Acm 43. What is meant by slew rate? The slew rate of an op-amp is the maximum ratio at which its output voltage is capable of changing. It is expressed in volts per µ seconds. The slew rate of op-amp is in the range of 0.312V/µs. 44. How does an input offset voltage arises? This voltage arises because of small imbalances within the op-amp. Its range is 10µ to 7mV for op-amps with bipolar transistor input type and 0.5 to 15mV for op-amps with FET. 45. What is meant by summing amplifier? A summing amplifier can be used to produce the mathematical average of input voltages. 46. What are the applications of op-amp? Op-amp can be used as 1. Constant gain multipliers 2. Voltage summing amplifier 3. Voltage buffer amplifier 4. Basic amplifier in instrumentation circuits &Comparator in oscillator circuits and active filters 47. How the voltage follower can be obtained from a non-inverting amplifier? The voltage follower circuit can be obtained from the non-inverting amplifier by removing resistors R1 and R2(Rf). 48. What is the relation between gain and bandwidth of an op-amp? D. Jayakumar

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1. The higher the gain of an op-amp, the narrower is its bandwidth, and 2. The lower the gain of an op-amp, the wider is its bandwidth. 49. What is the expression for the maximum operating frequency of op-amp? The maximum operating frequency of op-amp is, fmax = slew rate/2ПVpk where Vpk = peak output voltage 50. Why it is called as RC Coupled Amplifier? a. It is the most important method of coupling the signal from one stage to the next. b. In this method, the signal developed across the collector resistor of each stage is coupled through capacitor into the base of next stage. c. The cascaded stages amplify the signal and overall gain is product of individual stages gains. The amplifier using this coupling scheme is called as RC coupled amplifier. 51. Mention the uses of each capacitor in the circuit? a. Capacitor C1- is used to couple the input signal to base of Q1. b. Capacitor C2 – is used to couple the output signal from the collector of Q2 to the load. c. Capacitor CE – is connected at the emitters of Q1 because they bypass the emitter to the ground. Without these, voltage gain of each stages will be reduced. 52. How will be the output signal? The output signal of two stage RC coupled amplifier is inphase with the input signal. 53. Why the output signal will be in phase with input signal? Is is because of the fact, that its phase has been reversed twice by the amplifier. 54. Formula for voltage gain? Overall voltage gain Av = Av1 x Av2 Ro2 Ro1 = ---------- x -------------r’o2 r’o1 Ro1 x Ro2 Av = -------------re2 If the transmission used in both stages are identical the current gain will be equal . , the emitter current will also be equal. Thus r’e1 = r’e2 = re. 55. What do you mean by frequency response of RC coupled amplifier? The graphs shows, the voltage gain drops off (rolls off) at low frequencies ( below 50hz) and at high frequencies (above 20khz) while it remains constant in mid range frequency. 56. Why at mid range frequency it maintains constant? At mid frequency (50Hz to 20MHz). the effect of coupling capacitor in this frequency range, is such that it maintain constant a constant voltage gain. When the frequency increases, the reactance of capacitance decreases. When kinds to increase the gain. 1 to ever the lower capacitor reactance increases the loading effect to next stage due to which gain reduces. The two factors almost cancel each other. These the constant gain is maintained throughout this frequency range. 57. Advantages of RC Coupled amplifier? a. b. c. D. Jayakumar

It si most convenient and least expensive multistage amplifier. Is has a wide frequency response. It provided less frequency distortion. 5

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58. Disadvantages of RC coupled amplifier? a. The overall gain of the amplifier is comparatively small because of loading effect of successive stages. b. It provides poor resistance (or impedance matching between two stages. c. It has a tendency to become noisy with age, especially in mosty elimate. 59. Applications of RC Coupled amplifier? RC Coupled amplifier has an excellent frequency response, this property makes it very useful in the stages of all public address systems. 60. What is Tuned voltage amplifier? Specify it purposes? An amplifier which amplifies a specific frequency (or) a narrow band of frequencies is called Tuned voltage amplifier. It serves two purposes. • Selection of desired radio frequency signal. • Amplification of the selected signal to a suitable voltage level. 61. Classification of Tuned Amplifier? The Tuned Amplifier are classified according to cascaded stages are i) Single Tuned amplifier. ii) Double Tuned amplifier iii) Stagger tuned amplifier. According to the Coupling i) Capacitive coupled ii) Inductive coupled iii) Transformer coupled. 62. What do you mean by Single tuned amplifier. Single tuned multistage amplifier circuit uses one parallel tuned circuit as local in each stage with tuned circuits as a load in ach stage with tuned circuits in all stages are tuned to the same frequency. 63. What do you mean by Double Tuned Amplifier. In Double tuned amplifier, the voltage developed across tuned circuit is coupled inductivity to another tuned circuit. Both tuned circuits are tuned at same frequency. 64. Advantages of Tuned amplifier. • They amplify defined frequencies. • Signal to noise ratio at output is good • They are well suited for radio transmitters and receivers. • The band of frequencies over which amplification required can be varied. 65. Disadvantages of Tuned amplifier. • They are not suitable to amplify audio frequencies. • Since they uses inductors and capacitors as wining elements, the ciruit is bulky and costly. • If the band of frequency is increased, design becomes complex.

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66. Advantages of Double Tuned over single tuned. • Process a flatter response having steeper sides. • Provides larger 3db bandwidth. • Provides larger gain width product. 67. What is resonant frequency ? conditions for resonance? In Resonant circuit, As the frequency increases, the inductive reactance (XL) increase and capacitive reactance (XC) decreases. But at particular (or) certain frequency, of a.c applied voltage, the XL is equal to XC. this frequency is called resonance frequency. Under resonance condition: • Impedance of the resonant circuit becomes maximum • Line current (or) current drawn from source is minimum. Expression for resonant frequency, XL = XC 1

f0 = -------------2π√LC 68. Explain the sharpness of resonance? In the resonance curve, of a resonant circuit, required to be as sharp as possible in order to provide a high selectivity. The sharp resonance means that the impedance falls of rapidly as the frequency is varied above and below of resonant frequency. Sharpness is defined by, Bandwidth Sharpness =----------------------------Resonant frequency

=

BW ---------f0

69. What is quality factor? XL Qo = ------R BW Sharpness of resonance = ------------Qo fo

1 f2 – f1 = ------------ = ---------f0

L à value of circuit inductance R à value of circuit resistance. Sharpness of resonance (or) selectivity depends on quality factor. • •

Higher value of quality factor provides higher selectivity, but smaller bandwidth. Lower value of quality factor provides lower selectivity , but larger bandwidth.

70. What type of coupling is used for astable multivibrator? The capacitive coupling is used for astable multivibrator. D. Jayakumar

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71. What is the other name of astable multivibrator? Free running relaxation oscillator is the other name for astable multivibrator. 72. What is equation frequency for astable multivibrator ? 1 f = -------------1.38 x RC 73. How the phase shift is obtained in astable multivibrator? The amplifying stage introduces a 180o phase – shift and another 180o phase – shift is introduced by a capacitor, therefore the feedback signa; has a total phase – shift of 360o(or)0o. 74. Explain the operation of astable multivibrator? Due to capacitive coupling, none of the transistor can remain permanently cut-off or saturated. Instead the circuit has two quasi-stable states (ON and OFF) and it makes periodic transition between these two states. 75. Give the application of astable multivibrator? • • •

It is used in time base circuits oscillators clock generators etc….

76.Explain the sample and hold circuit? A sample and hold circuit, samples an input signal and holdson to its last sampled value until the input is sampled again. 77. Explain the time constants for sample and hold oscillator? [(R0 + rDS(on))]C. Here R0 is the output resistance of the voltage follower. RDS(on) is the resistance of the MOSFET when on. 78. Explain sampling theorem? It states that “ the sampling frequency should be greater than twice the maximum input signal”. Fs > 2fm .

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MOBILE UNIT - VIVA QUESTIONS What is the general block diagram for GSM?

OMC – Operation maintenance unit BTS – Base transceiver station HLR – Home location register VLR – Visitor location register MSC – Mobile switching center AUC – Authentication center BSS – Base station subsystem BSC – Base station controller 2. What is the frequency range of forward link and reverse link in GSM? 890-915 MHZ à Subscriber – to – base transmissions (Reverse link) 935-960 MHZ à Base – to – Subscriber transmissions (Forward link) 3. What is the modulation data rate for GSM? Radio transmission on both the forward and reverse link are made at channel data rate 270.833 Kbps

of

4. What is the type of modulation used in GSM? 0.3 GMSK Modulation 5. What is the number of traffic channels used in GSM? There are totally 1000 traffic channels were present within GSM . What is the maximum delay for the GSM? The maximum delay is 40ms 7. What are the types of channels in GSM? There are totally two channels were used in GSM 1. Traffic channel D. Jayakumar

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2. Control channel TRAFFIC CHANNEL: It carries digitally encoded user speech or user data and has identical functions and formats on both the forward and reverse link. CONTROL CHANNEL: It carries signaling and synchronizing commands between the BS and the MS 8. What is the advantage of GSM? The main advantage of using GSM is roaming facility 9. What is known as roaming? Roaming is defined as the facility for a cellular and customer to automatically make and receive voice calls. Send and receive data or access other services when traveling outside the geographical coverage area of the home network, By means of using a visited network.

SATTELLITE LINK BLOCK DIAGRAM: TRANSMITTER

TRANSPONDER

RECEIVER

1. Frequency range used in lab? 2-4GHz which falls in S band. 2.

General frequency range? C and KU band C band=6/4 GHz Ku band=14/11GHz

3. 4. What type of antenna is used in lab? Helical type of antenna is used in lab. 5. 6. C/N ratio of a satellite link? C/N = [EIRP]+[G/T]-[LOSSES]-[k] dBHz [C/N]u = [EIRP]u + [G/T]u – [LOSSES]u – [k] [C/N]d = [EIRP]d + [G/T]d – [LOSSES]d – [k] – [B] 7. Why uplink frequency greater than downlink frequency? Attenuation is more 6. What is the bandwidth of S-Band? 27 MHz 7.

What is the antenna used in the earth station? Aperture antenna, parabolic antenna, cassegrain antenna

8. Antennas used in Space craft? Directional antennas D. Jayakumar

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9. What is the use of satellite link? Satellite link is used for the transmission of point to multipoint link. 10. Who launched the first satellite? When? SPUTNIK by USSR in 1957 11. INTELSAT I– 1965 INTELSAT II– 1966 INTELSAT III- 1968 INTELSAT IV - 1971 INTELSAT IV - 1975 INTELSAT III- 1980 TRANSMIISION LINE 1. What do you meant by transmission line? It is a means of conveying signals or power from one point to another. 2. What is meant by “BALANCED LINE”? In open wire line or twisted pair line are called as “BALANCED LINE” since the two conductors of this type of line have similar relationship with respect to ground. 3. Which line is called as unbalanced line and why? The coaxial line is an unbalanced line since the two conductors do not have similar relationship with respect to ground. 4. What is a radiation loss for coaxial cable? Coaxial cable has extremely low radiation loss due to shielding. 5. What are the losses in transmission line? There are three main sources of losses in RF transmission lines they are 1. Copper losses 2. Dielectric losses 3. Radiation losses 8. What is the characteristic impedance of transmission line? Characteristic of input impedance of a transmission line is infinitely long. Z=√(R+jWL)/(G+jwC) 9. What is the characteristic impedance of a lossless transmission line? Z0=√L/C Where (R=0; G=0) MEASUREMENT OF BIT ERROR RATE AND EYE PATTERN 1.

Define Bit error rate (BER)? The Bit error rate is the ratio of bits that have errors relative to the total number of bits received in a transmission. 2. 3. What is the BER for optical fiber communication? BER rate ranges from 10^(-9) to 10^(-12) 4. 5. What is meant by eye pattern? Eye pattern technique is a powerful measurement method for accessing the data handling ability of a digital transmission system. The eye pattern measurements are made in the time domain. It is used to show the effect of waveform distortion

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STUDY OF SPECTRUM ANALYSER 1. what is meant by spectrum analyzer? Spectrum analyzer is an instrument which displays the electrical signal values in frequency domain. 2. 1. 2.

What are the types of spectrum analyzer? Swept timed Real time analyzer 3.What do you meant by swept timed analyzer

The swept timed analyzer are tuned by electrically sweeping over their sweeping range 4.What do you meant by real time analyzer? Real time analyzer are capable of displaying transient response as well as provide periodic and random signals. 6. 1. 2. 3. 4. 5. 6.

Condition to be satisfied for spectrum analyzer? Wide tuning range Stability Resolution Flat frequency response High sensitivity Low internal distortion

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Prepare answer for the following questions. MOBILE LINK 1. Draw the block diagram of mobile link. 2 What is the general block diagram for GSM? 3. What is the frequency range of forward link and reverse link in GSM? 4. What is the modulation data rate for GSM? 5. What is the type of modulation used in GSM? 6. What is the number of traffic channels used in GSM? 7. What is the maximum delay for the GSM? 8. What are the types of channels in GSM? 9. What is the advantage of GSM? 10. What is known as roaming? 11.What do you mean by handoff? 12. Which service provider uses CDMA technique? 13 .Which service provider uses GSM technique? 14. Why cell site shape is hexagon? 15 .What is the frequency range of cellular mobile communication?

SATELLITE LINK 1. Draw the general block diagram of satellite link. 2. Frequency bands used in satellite link. 3. Frequency bands used for satellite link in our lab? 4. What types of antennas used for earth stations and transponder for satellite link 5. What type of antenna is used in our lab? 6. Explain C/N ratio of a satellite link? 7. Why uplink frequency greater than downlink frequency? 8. What is the bandwidth of S-Band? 9. What is the uplink frequency of C band and Ku band and downlink frequency of C band and Ku b band?. 10. Why C band is most widely used? 11. What is the use of satellite link? 12. Who launched the first satellite? When? 13. What do you mean by single conversion and double conversion transponder?

TRANSMIISION LINE ANALYSER 1. 2. 3. 4. 5. 6. 7. 8. 9.

What do you meant by transmission line? What is meant by “BALANCED LINE”? Which line is called as unbalanced line and why? What is radiation loss for coaxial cable? What are the losses in transmission line? What is the characteristic impedance of transmission line? What is the characteristic impedance of a lossless transmission line? What do you mean by VSWR? What is the ideal value of VSWR?

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OPTICAL LINK 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15.

.Draw the general block diagram of optical communication. What is the wavelength range of optical link What type of sources are used in transmitter in optical link. What type of detectors are used in receiver for optical link. Compare PIN and Avalanche photodiode with diagram. Compare LED and LASER. Compare single and multimode fiber. Compare step index and graded index fiber. What do you mean by responsitivity and Quantum efficiency? What do you mean by dark current and leakage current? What are advantages of optical link? Define Bit error rate (BER)? .What is the BER for optical fiber communication? What is meant by eye pattern? What do you mean by SONET/SDH?

SPECTRUM ANALYSER AND NETWORK ANALYSER 1. What is meant by spectrum analyzer with the help of block diagram? 2. What are the types of spectrum analyzer? 3. What do you meant by swept timed analyzer

4. What do you meant by real time analyzer? 5. Condition to be satisfied for spectrum analyzer? 6. What is meant by Network analyzer with the help of block diagram 7. What are the types of Network analyzer. 8. Give the application of spectrum analyzer and Network analyzer. 9. What do you mean by active and passive filter 10. Compare AM and FM 11. Give the application of AM and FM. 12. Compare FSK, ASK, PSK. 13. Give the applications of FSK, PSK. 14. What do you mean by roll off in the frequency response of filters? 15. What do you mean by order in the filters? GENERAL QUESTIONS 1. What are the ideal characteristics of op - amp? 2. What is meant by inverting and non-inverting amplifier? 3. What is meant by differential amplifier? 4. What is the gain of the op-amp (741C)? 5. What is the input resistance of op-amp (741C)? 6. What is the value of output resistance of op-amp (741c)? 7. What is CMRR? 8. What is meant by slew rate? 9. How does an input offset voltage arises? 10. Explain the block diagram and the symbol of op-amp? 11. What is meant by summing amplifier? 12. How the voltage follower can be obtained from a non-inverting amplifier? 13. What is the relation between gain and bandwidth of an op-amp? 14. What is the expression for the maximum operating frequency of op-amp? 15. Explain the difference between integrator and differentiator? Give its applications? 16. Why it is called as RC Coupled Amplifier? 17. Mention the uses of each capacitor used in RC coupled amplifier. 18. How will be the output signal in RC Coupled Amplifier? D. Jayakumar

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19. What are the different types of amplifiers based on configuration? 20. What type of configuration used in Rc coupled amplifier? 21. What do you mean by frequency response of RC coupled amplifier? 22. What do you mean by Figure of Merit in amplifier? 23. Why at mid range frequency, Gain maintains constant? 24. Advantages of RC Coupled amplifier 25. Disadvantages of RC coupled amplifier 26. Applications of RC Coupled amplifier 27. What is Tuned amplifier? Specify it purposes? 28. Classification of Tuned Amplifier 29. What are the different types of amplifier with respect to coupling? 30. What do you mean by Double Tuned Amplifier? 31. Advantages of Tuned amplifier. 32. Disadvantages of Tuned amplifier. 33. Advantages of Double Tuned Amplifier over single tuned Amplifier. 34. What is resonant frequency? Conditions for resonance? 35. Explain the sharpness of resonance? 36. What is quality factor? 37. Applications of Tuned amplifier: 38. What type of coupling is used for Astable multivibrator? 39. What is the other name of Astable multivibrator? 40. What is equation of frequency for Astable multivibrator? 41. How the phase shift is obtained in Astable multivibrator? 42. Explain the operation of Astable multivibrator? 43. Give the application of Astable multivibrator? 44. What is the use of sample and hold circuit? 45. What is the use of op-amp circuit in sample and hold circuit? 46. What is the use of FET device used in Sample and Hold circuit? 48. Explain sampling theorem? 47. Explain the operation of Sample and Hold circuit. 48. Tell about Different IEEE Standards. 49 What is the use of different layers in OSI MODEL? 50. Application of Fourier transform 51. What is the difference between FDM and TDM? 52. What do you mean by attenuation and distortion in optical link? 53. What do you mean by Source coding ? What are its types? 54. What do you mean by Line coding? What are its types? 55. What is the special feature about Casse-grain antenna and Parabolic antenna? 56. What is the special feature about Horn and Yagi-Uda antenna? 57. What do you mean by directivity? 58. What do you mean by Beam-width and Half power Beam-width? 59. Compare TCP/IP and OSI model? 60. Give the IEEE standards for different networks 61. What do you mean by Hub, Bridge, Switch, Routers? 62. Compare FDMA, TDMA,CDMA. 63. Compare Satellite link, optical link and Microwave link 64. What are the different generations of Mobile link 65. What are the different generations of optical link

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Final Year ECE /Compressive Viva Voce Test I 1. Frequency range and band of Microwave Link 2. Draw the block diagram of a digital communication system 3. What do you mean by source encoding? Explain the different types of source encoding techniques. 4. What do you mean by channel encoding? Explain the different types of channel encoding techniques. 5. Define power spectral density. 6. Define BER. 7. Which type of digital modulation is having less BER. 8. Frequency Bands used for satellite link. 9. Advantages of digital communication system. 10. Define FIR filter. 11. Define IIR filter. 12. Compare Chebhyshev filter and Butterworth filter. 13. Compare all types of windowing techniques used for FIR filter. 14. Applications of windowing techniques used for FIR filter. 15. Applications of IIR filter . 16. Specify the special features of Chebhyshev and Butterworth filter. 17. What do you meant by Emitter follower? 18. What type of configuration used in Emitter follower? 19. Give the applications of Emitter follower. 20. Give the characteristics of Emitter follower. 21. Explain the circuit operation of emitter follower. 22. Explain how Emitter follower is used as impedance matching circuit. 23. What type of biasing is used in RC coupled amplifier and Emitter follower? 24. What are the advantages of Voltage Divider Biasing? 25. Mention the frequency range of FM. 26. Mention the bandwidth of FM. 27. What is the use of Pre-emphasis and De-emphasis circuit? 28. Give the application of Pre-emphasis and De-emphasis. 29. Explain the operation of Pre-emphasis circuit? 30. Explain the operation of De-emphasis circuit? 31. Advantages of FM over AM 32. Explain the operation of Tuned amplifier circuit. 33. Explain the electromagnetic spectrum of frequency. 34. What is the need for computer networks? 35. What is the difference between OSI and TCP/IP model? 36. What is the difference between LAN, MAN and WAN? 37. Give an example for connection oriented and connectionless services 38. What is the design issues carried out in data link layer? 39. What do you mean by error control? 40. Mention any two methods for error control schemes? 41. What do you mean by flow control? 42. Mention the different types of methods for flow control schemes 43. What do you mean by framing? 44. What is the difference between X.25 and frame relay? 45. What are the design issues of network layer? 46. What do you mean by Flooding? 47. What do you mean by Congestion? 48. . What are the different types of Routing algorithm? 49. What do you mean by CSMA/CD, Pure ALOHA and Slotted ALOHA? 50. Compare coaxial line, Microwave link and optical link.

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Final Year ECE / COMPHRENSIVE VIVA VOCE TEST 3 1. What is the general block diagram for GSM? 2. What is the frequency range of forward link and reverse link in GSM? 3. What is the data rate for GSM? 4. What is the type of modulation used in GSM? 5. What is the number of traffic channels used in GSM? 6. What is the maximum delay for the GSM? 7. What are the types of channels in GSM? 8. What is the advantage of GSM? 9. What do you mean by roaming? 10. Frequency ranges used for satellite link? 11. Define C/N ratio of a satellite link? 12. Why uplink frequency greater than downlink frequency? 13. What is the bandwidth of S-Band? 14. What are the types of antennas used in the earth station? 15. What are the types of antennas used in Space craft? 16. What is the use of satellite link? 17. Who launched the first satellite? When? 18. What do you meant by transmission line? 19. What is meant by “BALANCED LINE”? 20. Which line is called as unbalanced line and why? 21. What are the losses in transmission line? 22. What is the radiation loss for coaxial cable? 23. What is the characteristic impedance of transmission line? 24. What is the characteristic impedance of a lossless transmission line? 25. Define Bit error rate (BER)? 26. What is the BER for optical fiber communication? 27. What is meant by eye pattern? 28. What is meant by spectrum analyzer? 29. What are the types of spectrum analyzer? 30. What do you meant by swept timed analyzer 31. What do you meant by real time analyzer? 32. What do You Mean by Network analyzer? 33. What is the difference between Network analyzer &Spectrum analyzer? 34. What is the characteristic impedance of TV receiver? 35. What are the different generations of Mobile Communication? Final Year ECE / COMPHRENSIVEVIVA VOCE TEST V 1. What is a Causal System? 2. What is convolution? 3. What is a LTIS system? 4. What is the relation between z transform and Fourier transform? 5. Why do we need FFT? What are the Drawbacks of DFT? 6. Give the basic Butterfly of DIT and DIF algorithms. 7. Compare FIR and IIR filters. 8. What is Gibb’s phenomenon? 9. What are Windows? Why do we need it? 10. Realize the filter in direct form H(z) = 1 + 2 z-1 + 3 z-3 + 2 z-5 + z-6 11. What are the drawbacks of Impulse Invariance Method? 12. What is frequency transformation? 13. What are Limit cycles? 14. What is coefficient Quantization Error? 15. What is decimation and Interpolation? 16. Write the Maxwell’s equation. 17. What is Gauss law? D. Jayakumar

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VVQ&A

18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29.

In its simplest form What is waveguide? Describe the cutoff frequency; cutoff wavelength for a waveguide. What is meant by TE mode of propagation? TM mode of propagation. What type of filter is a waveguide? Draw the mode pattern of TE10 , TM11. When is it advantageous to use a circular waveguide? What is phase velocity and group velocity? What is characteristic impedance? What is the use of a Balun? What is stub matching? What is Poynting theorem? What is impedance matching?What is VSWR and reflection coefficient?

Final Year ECE / COMPHRENSIVEVIVA VOCE TEST 4 1. Describe the piezoelectric effect 2. Describe a phase –locked loop. 3. Define synthesize. What is frequency synthesizer? Describe direct indirect frequency synthesizer. 4. What is the relationship between the modulating – signal frequency and the bandwidth in a conventional AM system? 5. Give the differences between low level and high level modulators 6. Define noise temperature and equivalent noise temperature 7. Define heterodyning receiver 8. Define image frequency 9. Describe the following terms a) Simple AGC b) Delayed AGC c) Forward AGC 10. What is pilot carrier? 11. Define peak envelope detector. 12. Give the basic difference between AM & FM receivers. 13. What is the difference between mobile radio and mobile telephone? 14. What is the purpose of the communication protocol in a cellular radio system? 15. Explain the inverse square low. 16. Define electromagnetic wage interference 17. Define maximum reusable frequency 18. Define A) antenna polarization B) antenna Bandwidth C ) antenna beam-width 19. what is the difference between PSK & QAM 20. Define information capacity 21. Explain the relationship between the minimum bandwidth required for a FSK system and the bit rate 22. Explain the relationship between mark and space frequencies 23. What are the three most predominant modulation schemes used in digital radio systems? 24. Explain the relationship between bits per record and laud for a BPSK system? 25. What is the difference between MSK and FSK? COMPREHENSIVE VIVA VOCE INTERNAL TEST

1. 2. 3. 4. 5. 6. 7. 8. 9. D. Jayakumar

What are the ideal characteristics of op - amp? What is CMRR and Slew rate? Explain the difference between integrator and differentiator? Give its applications? What do you mean by Figure of Merit in amplifier? What is Tuned amplifier? Specify it purposes? What is Barkhausen Criteria? What is resonant frequency? Conditions for resonance? What are the types of channels in GSM? What do you mean by roaming? What do you mean by VLR and HLR? 18

VVQ&A

10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. 43. 44. 45. 46. 47. 48. 49. 50. 51. 52. 53. 54. 55. 56. 57. 58. 59. 60.

D. Jayakumar

What is meant by “BALANCED LINE”? What is meant by eye pattern? What is the difference between Network analyzer & Spectrum analyzer? Define C/N ratio of a satellite link? Why uplink frequency greater than downlink frequency What is SPADE? What is transfer orbit? What is the use of Apogee Kick motor? What is INMARSAT? Give its uses. Differentiate LEO, MEO and GEO satellites. What is convolution? What do you mean by Fourier transform? Give its applications Why do we need FFT? What are the Drawbacks of DFT? Compare FIR and IIR filters. What is Gibb’s phenomenon? What is the use of a window function? What are Limit cycles? Write the Maxwell’s equation. What do you meant by TE and TM waves? What do you meant by dominant modes in TE and TM waves? Draw the mode pattern of TE10, TM11. What is phase velocity, group velocity and intrinsic impedance? What is characteristic impedance? What is VSWR? What is stub matching? What do you mean by source encoding? Explain the different types of source encoding techniques. Why information is measured in Logarithmic scale? Define power spectral density. Explain how Emitter follower is used as impedance matching circuit. Explain sampling theorem? What is the use of Pre-emphasis and De-emphasis circuit? Advantages of FM over AM Describe a phase –locked loop. Give the differences between low level and high level modulators Define Super heterodyning receiver. What are the Advantages of IF? What is image frequency? What is pilot carrier? What is channel capacity theorem? What is the difference between MSK and FSK? What is the difference between OSI and TCP/IP model? What do you mean by Flooding and Congestion List the functions of Data link Layer. Explain CSMA/ CD. Why Ethernet is popular than Token ring/bus? Explain DTMF signaling. What is ISDN? What are BRI and PRI? How do we arrive at 64 Kbps for a standard PCM? Why bit stuffing is used in data communications? Compare Pulse and Tone dialing. What is Maximum power transfer theorem? What are hybrid parameters? Give the four h-parameters. State Thevenin’s theorem with examples. What are transient and steady states? What are Poles and zeros? Explain stability of a system in s-domain. Explain the star – delta transformation.

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Final Year ECE / COMPHRENSIVE VIVA VOCE 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24.

25.

What is the difference between MSK and FSK? Give the basic difference between AM & FM receivers Define heterodyning receiver Why uplink frequency greater than downlink frequency n satellite link? What is the difference between Network analyzer &Spectrum analyzer? What is the characteristic impedance of TV receiver? What are the different generations of Mobile Communication? What is decimation and Interpolation? Write the Maxwell’s equation. What is Gauss law? What is phase velocity and group velocity? Compare FIR and IIR filters. What is the relation between z transform and Fourier transform? What are the advantages of optical communication? What do you mean by intrinsic impedance? What do you mean by characteristic impedance? Tell about Different IEEE Standards What is CMRR? Who are the service providers of GSM Who are the service providers of CDMA What are the different generations of optical communications What are the advantages of satellite communication What is the relation between z transform and Fourier transform? Define cut off frequency, cut off wavelength in waveguide. Tell about frequency ranges of satellite link.

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Dontabhaktuni Jayakumar DECE., PGDCA., B.Tech., M.Tech

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D. Jayakumar

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