Qs Asked inESE-2014 Interviews from 05.01.2015 to 09.01.2015

(Feedback given by candidates after Interview) Chairman: Professor H.C.Gupta 1

st member

2nd

Lady member

3rd

Member

Q.1 What is antenna bandwidth ? Ans: It is the range of frequency over which antenna can radiate or receive EM wave properly. Higher is the bandwidth lower will be the Quality factor. Q.2 What is antenna gain? If it is gain why not active device ? Ans: It is the ratio of the power required at the input of a lossless reference antenna to the power supplied to the input of the given antenna to produce in a given direction the same field strength at the same distance. It is Not producing any gain but Gain means how much it is radiating in particular direction. So it deals with directivity Q.3 What is polarization and how polarization decides type of antenna? Ans: Polarization of antenna means polarization of far field or radiated field produced by an antenna. For

better reception both TX and RX antenna must have same type of polarization. If there is mismatch between polarization then signal will be lost. Power loss due to mismatching between antenna is proportional to

cos2α If both antennas are horizontally polarized ,vertically polarized or circularly polarized then there is no

loss but if one antenna is horizontally polarized and other is vertically polarized then cos2α will have zero

value If one antenna is circularly polarized and other is linearly polarized then there is loss of 3 dB.

Q. 4 What is VHDL? Its uses ? And Advantages? Ans: “Very High Speed Integrated Descriptive Hardware Descriptive Language”

It is used in electronic design simulation of various Analog and digital circuits. By use of VHDL we can analyze behaviors of various circuits before implemented into real design. Advantages of VHDL:

1. Implementation Independent

2. Increase Productivity

3. VHDL can be simulated

4. Can specify specifications also

Q.5 Difference between Verilog and VHDL? Ans: Both are basically hardware descriptive languages but basic difference between both is :

1. VHDL is based upon Pascal language but verilog is based upon recent C language

2. Verlog is easy while VHDL is difficult

3. Verilog is used for simple data type while VHDL for Complex data type.

4. No library management in Verilog but available in VHDL

Q.6 Whether both Tx and Rx antenna should have same

polarization? Ans: See Ans.3 Q.7 What happened if one antenna is circular and other is vertically polarized ? Ans: See Ans.3

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Q.8 Design Hour,Minute and second clock by using digital electronics ? Ans: Pass 1 Hz clock to MOD-60 Counter for Second Followed by MOD-60 counter for minutes followed by MOD-60 counter for Hours.

Q.9.How will you minimize any logic circuit ? Other than K-Map what are the methods? Ans: Minimization of Logic circuit is done with the help of :

1.Boolean Algebra method 2. K-Map methods.

3. tabulation method Q.10 What is use of tabulation method for minimizing circuit ? Ans: It is used for more than 6 variables simplifications Q.11 For better voltage gain which is preferred CE or CS and why? Ans: Due to high value of trans conductance gain in BJT value of voltage gain is high in compare to FET. It is generally 30-40 times high in case of BJT in compare to BJT. Q.12 What are advantages of CS amplifier over CE amplifier ? Ans: High input impedance and low output impedance of FET are advantages of CS or CE Q.13 How will you minimize circuits in VHDL Ans: By use of VHDL we are not minimizing circuits we are doing analysis of various analog circuits and

doing simulation in lab before going to actual fabrication. Q.14. How VHDL programming is done? Ans: it has entity ports and test bench. Q.15 Difference between Hartley and Colpitt oscillator ? which one is better and why? Hartley uses 2 Inductors and 1 capacitor while Colpitt uses 2 capacitors and 1 inductors .Colpitt has lower size due to less bulky inductors and at the same size it has better frequency stability. It also has wide frequency operation. Q.16 How Hartley oscillator follows Barkhausen criterion ?

Ans: When VCC is on capacitor will charge up to a voltage and this initial voltage acts as excitation for tank circuit and causes a current to flow in LC circuit. It will induce damped harmonics oscillations which

will derive the base of transistor and both extreme end of voltage are at opposite polarity so there is 1800

phase shift introduced by feedback network. Q.17 What are the various topologies of negative feedback ? Ans: It is of 4 types 1. Voltage shunt

2. Voltage series

3. Current shunt

4. Current series Q.18 Is there any advantage of one over another? Ans: As such there is no advantage of one over other. Various feedback have different applications

Q.19 Why negative feedback make stable ? Ans: In the case of negative feedback gain becomes independent of gain without feedback and depends only

upon feedback network. Feedback network is generally register network so it remains stable.

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Q.20 Is negative feedback improves Signal to Noise ratio if yes which type of noise it is affecting? Ans: Negative feedback effects internal noise produced in amplifier. It will be reduced by a factor of de-sensitivity.

Q.21 Can it improves External noise ? Ans: External noise is not improved it will reduces both signal and noise so SNR remains same .

Q.22 What is frequency range of Wein bridge oscillator ? Ans: It works in audio frequency range

Q.23 How Wein bridge better than RC phase oscillator ? Ans: It can generate variable frequency oscillator. By varying component either R or C Frequency can be varied. The is so called because the circuit is based on a frequency-selective form of the Whetstone bridge circuit. It has low distortion due to presence of negative feedback and very good tuning also so that it is very popular in audio frequency range.

Q.24 Voltage divider biasing is the best method how ? Ans: In case of voltage divider value of collector current is independent of beta and depends upon Emitter resistance only. So it will become temperature stable and more stable circuit.

Q.25 What is role of bypass capacitor ? Ans: Bypass capacitor prevents negative feedback

Q.26 what type of feedback it prevents ? Ans: It is current series negative feedback

Q.27 Why voltage divider biasing is known as self biasing circuit ? Ans: By use of emitter resistance any increase in Collector current is reduced. Value of emitter resistance should be high for better self biased circuit.

Q.28 In Radar what type of polarization are used ? Ans: It uses an antenna that is designed to transmit and receive EM waves of a specific polarization. Antennas may be horns, waveguides, dipoles and micro strip-patches. According to requirement antennas may be used. In RADAR only one antenna is used for transmission and reception so there will be no mismatching in polarization. This polarization may be linearly or circular according to requirement. Common polarizations are Horizontal linear (H) or vertical linear (V) and Circular polarization.

Q.29 What is the frequency range of Radar? Ans: It may uses HF VHF UHF and upto 90 GHz. Various bands used are L S C X Ku K Ka ,V and W bands.

Q.30 Is there possibility of circular polarization in radar? Ans: Circularly polarized signal can be transmitted by feeding the H and V parts of the antenna simultaneously with signals of equal strength and a 90° phase difference. This polarization is used generally for weather forecasting radars.

Q.31 What is the use of Duplexer in radar? What is duplexer made of ? Ans: when same antenna is used for transmitter and receiver purpose then duplexer is used as switch in RADAR. This duplexer may be designed by use of Ferrite circulators , resonant cavities ,TR and ATR tubes or PIN diodes. It also protects receiver form high power transmitter.

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Q.32 Duplexer is active or passive device? Ans: It is basically a switch so must be passive device.

Q.33 What is difference between resonator and oscillator ? Ans: Resonator is basically a passive device in which Inductor and capacitor exchange their energy after every quarter cycle and it can resonate between a certain frequency range. Oscillator is an active device which generates sinusoidal or non sinusoidal waveform by using DC power supply.

Q.34 Block diagram of Foster Seeley Receiver ?

Q.35 What are the various methods for detection of FM? Ans: There are two methods direct and indirect methods. Direct methods uses either frequency discriminator or phase discriminator methods. Frequency discriminator uses Single slop and balanced slope while phase discriminator uses Foster Seeley and Ratio detector methods. Indirect method uses PLL

Q.36 What are the various methods for generation of FM? Ans: Indirect method uses Armstrong method while Direct method uses FET reactance modulator or VCO methods.

Q.37 Which method is the best method for generation of FM and why ? Ans: FET reactance modulator is the best method for generation of FM because frequency deviation can be done over a wide range and over the same range it is linear and distortion is minimum,.

Q.38 How PLL works and why it is the best method for detection of FM? Ans: It is highly effective in eliminating noise and interference and is basically a BPF. It is the best demodulation methods due to better frequency selectivity.

Q.39 What are the different type of capacitors ? Ans: Basically they are classified in two class polarized capacitor( for Larger value greater than 1 micro farad) and unpolarized capacitors( For Values < 1 Micro farad). Other capacitors are Polysterene trimmer and variable capacitors.

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Q.40 Which capacitors are used at radio frequency ? Ans: Ceramic capacitors are used at radio frequency.

Q.41 How these capacitors are designed? Ans: Ceramic Capacitor is a non-polarized fixed capacitor made out of two or more alternating layers of ceramic and metal in which the ceramic material acts as the dielectric and the metal acts as the electrodes. The ceramic material is a mixture of finely ground granules of par electric or ferroelectric materials, modified by mixed oxides that are necessary to achieve the capacitor's desired characteristics.

Q.42 What is difference between ray and wave front ? Ans: ray is set of straight lines passing though one point while wave front is a surface containing points.

Q.43 Wave front in which dimension ? 2D or 3D Ans: wave front is surface so 2D

Q.44 What is the dipole antenna ? Ans: It is a straight conductor and consists of two identical conductive elements such as metal wires or rods, which are usually bilaterally symmetrical. For almost any type of frequency whether MF or HF diploes are easy to build and install. So simplicity and wide range of communication is main reason of use of dipole. It

may be /2 dipole, Folded dipole or short dipole antenna.

Q.45 What is the use of dipole antenna?

Ans: /2 dipole antenna is generally used as reference antenna. It can help in measurement of gain.

Q.46 What is use of folded diploe antenna ? Ans: Due to increase in input impedance and wide bandwidth these are widely used where balanced feeder may be used. One of very important application is in Yagi Antenna.

Q.47 Difference between directivity and directive gain ? Ans: Directivity is nothing but maximum directive gain.

Q.48 Which band is preferred in satellite and why ? Ans: it is C band due to less effect of Rain attenuation and Less absorption loss.

Q.49 What is C band crowding ? how one can overcome it ? Ans: Spread spectrum is used for C band applications where C band crowding is more severe. C band antenna have lower gain antennas and thus adjacent satellite antenna is worse. To avoid this one can shift to other available frequencies.

Q.50 DTH works in which band of satellite ? Ans: It works in KU band (12-14 GHz)

Q.51 Why DTH not uses C band ? Ans: For Ku band (12-14 GHz) small size antenna is used while for C band antenna size is large.

Q.52 What are the advantages and disadvantages of using C band ? Ans: By using C band there will be no problem of rain attenuation and absorption loss but size of antenna will be large.

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Q.53 Define RAR RAL and RRC in Microprocessor? Ans:

RAR-Rotate Accumulator Right

RAL- Rotate Accumulator Left RRC: Each binary bit of the accumulator is rotated right by one position. Bit D0 is placed in the position of D7 as well as in the Carry flag. CY is modified according to bit D0. Any other bit is not affected.

Q.54 What is the use of ALE pin in microprocessor ? Ans: Address Latch Enable

Q.55 What is function of program counter ? Ans: A program counter is a register that contains the address location of the instruction being executed at the current time.

Q.56 What is the white noise and why it is white ? Ans: White noise is noise which has constant power spectral density .It contains all frequency range that’s why it is called white.

Q.57 What is the output of white noise once it is passed through LPF? Ans: It is called band limited white noise.

Q.58 Have you heard about noise bandwidth ? Ans: The noise bandwidth is the frequency which when multiplied by the LOW frequency value of the spectral noise power density at the output gives the same noise power value as the actual total noise power at the output integrated over the filter transfer function over all frequency.

Q.59 What is the physical meaning of Autocorrelation function& PSD ? Ans: ACF is the function that shows how much similarity is included in the signal itself. Power Spectral Density (PSD) is a measure of a signal's power intensity in the frequency domain. Q.60 Can you relate PSD and ACF and what is the name of that relation ? Ans: PSD is nothing but Fourier Transform of ACF.

Q.61 What are he uses of S band and C band ? Ans: S-band is in range of 2-4 GHZ Applications of S-band:

1. Used in Wi-Fi

2. Microwave oven, Cordless phone and Blue tooth

3. Used in satellite communication also

4. Used in RADAR for weather, surface radar

C-band is in range of 4-8 GHZ

Applications of C band: 1. Satellites communication

2. Satellite TV network

3. Fixed point to point ground stations

4. Non Military applications

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Q.62 Do you know spread spectrum technique ? Ans: Spread spectrum technique is used in wireless communication in which frequency of transmitted signal is varied to achieve greater bandwidth. It is used in CDMA . Ans: Q.63 How FDMA and TDMA are used in satellite communication ?

FDMA: Total transponder bandwidth is divided into various channels where each channel has fixed bandwidth. Each earth station is given one channel and all Earth stations are transmitted simultaneously TDMA: Each earth station transmits a data burst during a pre allocated period of time. Each data burst access same time slot.

Q.64 What is the limitation of uplink frequency ? Ans: Intermodulation distortion which is reduced by input back off

Q.65 What is the back off in power amplifier ? Ans: Input back off is provided on the uplink at earth station. This back off is provided to operate TWT amplifier in its linear region. Because of this backing off intermodulation distortion is reduced

Q.66 Why we have 6/4 GHz frequency in satellite ? Ans: Less effect of rain attenuation and insignificant sky back ground noise

Q.67 Why uplink is greater than down link frequency ? Ans: At earth more loss can be managed by using how power transmitter which is not possible at satellite side.

Q.68 What is Noise figure ? Value of noise figure is <1 or >1? Ans: it is the ratio of input signal to ratio to output signal to noise ratio and its value is greater than1. It is parameter for performance of a receiver. Lower the value better is performance.

Q.69 Can you explain noise in DM? Ans: There are two type of noise Granular noise and slope-overload modulation. Granular noise is due to lower value of rate of change of message signal while slope overload is higher value of rate of change of message signal.

Q.70 DM is oversampled how ? Difference between DPCM and DM? Ans: There is high correlation i.e. difference between adjacent samples has a variance which is smaller than signal itself. Here sampling rate is higher than Nyquist rate and i.e. why it has high signal to noise ratio. In DPCM the difference between successive samples are encoded into n-bit data streams while In delta modulation the transmitted data are reduced to a 1-bit data stream.

Q.71 Application of DPCM and DM? Ans: DPCM is used in voice and video transmission.DM is used in voice transmission where quality is not of much importance. ADM is modified form of Dm which is used in OFC,Satellite links transmission etcs.

Q.72 What are PSD of uniploar and bipolar pulses ? Ans:

Q.73 Why FM is more popular than PM? Ans: FM is Popular in Analog transmission while PM is popular in digital transmission.

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Q.74 Why FM is used for short distance only ? Ans: FM uses LOS propagation which has short range.

Q.75 Difference between FM and Short wave frequency ? Ans: FM uses frequency range from 88-108 MHz while SW uses 3-30 MHz

Q.76 What is Fourier series ? Ans: The representation of signals over a certain interval of time in terms of linear function of orthogonal function is known as Fourier Series which is mostly used for representation of periodic signals.

Q.77 What is application of Fourier series ?? Ans: By use of Fourier series any non sinusoidal periodic function can be converted into periodic signals. Since Fourier series contains many harmonics hence more details of non sinusoidal signals are available.

Q.78 What is difference between Fourier series and transform? Ans: Fourier series decomposes a periodic function into a sum of sines and cosines with different frequencies and amplitudes. Fourier Transform is a mathematical operation that breaks a signal in to its constituent frequencies. The Fourier transform is called the frequency domain representation of a signal since it depends on the frequency. Fourier series is generally used for Periodic signals while Fourier transform is used for non periodic signals.

Q. 79 What is the Fourier series of a noise signal ? Ans: Noise is a signal which has fixed amplitude and infinite number of frequencies

Q.80 What antennas are used in satellite ? Ans: Various antennas used are Parabolic, helical and phased array antennas

Q.81 Can you explain reciprocity theorem in antenna? Ans: If one knows the radiation pattern in transmit antenna then it is easy to decide radiation pattern in receive antenna by use of reciprocity theorem.

Q.82 What are the functions of Pins Trap,Ready and Hold in 8085 Ans: TRAP- It is the highest priority Non Mask able interrupts and is used in emergency conditions Hold- This pin causes the microprocessor to stop processing instructions and to release the bus. (HLDA) is used to confirm that the bus will be released on the next negative going clock edge. This is also called as DMA system in which data is transferred without any intervention of CPU. The main function of ready pin is to synchronize slower peripheral device to faster microprocessor.

Q.83 What are various interrupts and their priority ? Ans: TRAP RST7.5 RST 6.5 RST 5.5 and INTR are various interrupts out of that TRAP has the highest priority.

Q.84 How clocking is done in 8085 microprocessor ? Ans: Its Clock frequency is 3 MHz which can be given by use of crystal oscillator

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Q.85 What is Moor’s law ? Ans: The number of transistors in a dense integrated circuit doubles approximately every two years.

Q.86 What decides power of a processor ? Ans: it is the ability of a computer to manipulate data. CPU cycles is other name and it varies with architecture and clock speed of CPU.

Q.87 Difference between Hardwired and microprogrammed? Ans: Hardwired has high speed and more compact implementation but microprogramming has slower speed but flexibility and extension is easily possible.

Q.88 Why ARM processor is used for Mobile Laptop and smart phone? Ans: It needs low power consumption i.e. why it is preferred over other processors.

Q.89 How one selects processor for doing error correcting codes? Ans:

Q.90 Why NMOS is preferred over PMOS? Ans: Due to high mobility of electrons NMOS is faster than PMOS. NMOS need only half the size of P channel device with same geometry. So N MOS takes less space in compare to PMOS.

Q.91What are the advantages of PMOS over NMOS? Ans: 1. Better noise immunity

2. Low cost process

3. Highly controllable technology

Q.92 Why MOS is preferred in VLSI ? Ans: MOS becomes ON after application of crossing threshold voltage only means it is always not ON and CMOS can be designed easily becoz one MOS will be On while other will be OFF. There is no effect of small signal amplitude like noise because it is on after crossing Threshold voltage only.

Q.93 How UJT works as Relaxation oscillator ? Ans: UJT works on the concept of charging and discharging of capacitor. Its output is saw tooth waveform and here UJT is used as active element. It works as negative resistance device.

Q.94 What are negative resistance devices ? Other Relaxation oscillator ? Ans: If voltage is increased then current is decreased i.e dv/di <0 these devices behaves like an active device and can be used as an oscillator. UJT and Tunnel Diode are examples of negative resistance device

Q.95 Lissajous figure ? where it is used and why ? Ans: when two sinusoidal waves of different amplitude and phase are applied to X and Y channels of CRO then pattern seen is Lissajous pattern. By this we can see phased difference between two waveforms Q.96 What are PN sequences and uses? Ans: It is also known as Pseudo noise sequence which is random in nature and can be generated by use of shift registers and follows some rules regarding polynomial. It is used in spread spectrum like CDMA.

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Q.97 Spread spectrum modulation ? and its application ? Ans: Spread spectrum technique is used in wireless communication in which frequency of transmitted signal is varied to achieve greater bandwidth. It is used in CDMA . Frequency reuse concept is used by this only.

Q.98 What is DSSS? Ans: In direct sequence spread spectrum, the stream of information to be transmitted is divided into small pieces each of which is allocated across to a frequency channel across the spectrum. It is also known as Direct Sequence CDMA

Q.99 Wave guide is which type of filter ? Ans: Since wave which propagates in wave guide has frequency higher than cut off frequency hence it is high pass filter.

Q.100 What is the use of spiral antenna? Ans: it comes under the category of frequency independent antenna. It is generally has circular polarization and due to RHCP it is used in GPS. Other applications are in military purposes.

Q.101 Give practical example of Omni-directional antenna? How different from isotropic antenna? Ans: Omni directional antenna radiates power uniformly in all direction in one plane. Its radiation pattern is “Doughnut shaped”. Isotropic antenna radiates equal power in all direction and its radiation pattern is “Spherical”. Examples of Omni directional antennas are discone, Omni directional and half wave dipole antenna.

Q.102 What is camera resolution ? Ans: Resolution is nothing but number of pixels in particular portion of image. Pixel is unit of image and number of pixels decide resolution.

Q.103 What is the meaning of pixels in camera? Ans: Pixel is smallest part of image. A pixel is every liitle dot of color you can see more are the numbers of pixels more accurate will be image

Q.104 Spatial and grey level resolution ? Ans: Spatial resolution as the number of independent pixels values per inch. If we have two images of same size then one with more spatial resolution will be called as more clear picture. The number of bits per pixel is known as grey level resolution.

Q.105 What is ISO 9000? Ans: ISO 9000 is a quality management standard that presents guidelines intended to increase business efficiency and customer satisfaction. The goal of ISO 9000 is to embed a quality management system within an organization, increasing productivity, reducing unnecessary costs, and ensuring quality of processes and products.

106. What is pseudo noise ? Ans: See Q.96

Q.107 RADAR range ? Is Radar color blind ? Ans: it is the maximum range which radar can detects it depend upon transmitted power, target crossectional area, minimum detectable signal power and wavelength

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Q.108 What are the various orbits in satellite ? Ans: Q. 109. What is relation between range and power relation in RADAR? Ans: Range is one fourth power of transmitted power.

Q.110 What are the advantages of satellite communication Ans: 1. Best performance and more reliable

2. Possible at every place i.e global availability Q.111 What are disadvantages in satellite comm. Ans: 1. High cost

2. Delay in propogation Q.112 What are type of antenna used in satellite communication ? Ans: Q.80 Q.113 What is relation between antenna gain power gain directivity Ans: Efficiency is the ratio of power gain and directive gain. Directivity is nothing but maximum

directive gain Q.114 What is radiation intensity in antenna? Ans: It is total power divide by 4π where 4π is the total solid angle . Q.115 What is the meaning of near field in antenna? Ans: This is like evanescent region in antenna it represents how much magnetic field energy is stored Q.116 What is Gaussian distribution ? Ans: The normal distributions are a very important class of statistical distributions. All normal distributions are symmetric and have bell-shaped density curves with a single peak. It is always symmetrical, with equal areas on both sides of the curve. The highest point on the curve corresponds to the mean score, which equals the median and the mode in this distribution.68 %of the observations fall within 1 standard deviation of the mean, 95% of the observations fall within 2

nd standard deviation of the mean& 99.7% of the

observations fall within 3rd

standard deviation of the mean. Q.117 What is applications of Gaussian distribution ? Ans: In Employee human resource management where employee performance some time is referred as normally distributed. Also used in operation research where process variations are normally distributed. Q.118 What is central Limit theorem ? Ans: The central limit theorem states that the sampling distribution of any statistic will be normal or nearly normal, if the sample size is large enough. Q.119 Application of Central Limit theorem? Ans: The unexpected appearance of a normal distribution from a population distribution that is skewed (even quite heavily skewed) is used by C.L.T Q.120 Limitation of Central Limit theorem? Ans: it is used for large data. Q.121 What is mean in terms of pdf

Ans: E[ X ] xf X (x ) dx

Q.122 What is variance in terms of pdf Ans:

2 x E[ X

2 ] (E[ X ])

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Q.123 Difference between random variable and random process? Ans: Q.124 What is stationary process? Ans: If mean of a random process is constant and ACF is function of time difference then it is stationary process.

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Q.125 What is Ergodic process? Ans: If time average and statistical average are same then process is known as ergodic process. Q.126 What is correlation coefficient? what is range of correlation coefficient ?

Ans:

CXY

value of correlation coefficient lies between -1 and +1

E[ X ] E[Y ]

Q.127 Difference between white noise and pink noise ? Ans: White noise is a sound that contains every frequency within the range of human hearing (generally from 250 hertz to 8,000 kHz) in equal amount. Pink noise is a variant of white noise. Pink noise is white noise that has been filtered to reduce the volume at each octave. Q.128 What is standard deviation and variance ? Ans: Q.122 standard deviation is positive square root of variance Q.129 Explain Tunnel diode taking Fermi level into consideration ? Ans: Figure is required. Q.130 How Tunneling occurs ? Ans: when VB of P type and CB of N types comes at same energy level then there is heavy flow of electrons and that is known as tunneling? Q.131 Is tunneling for e’s only ? or for holes also? Ans: Only electrons Q.132 What is meaning of tunneling ? Ans: Refer 124 Q.133 Draw chacteristics of Tunnel diode ? Ans:

Q.134 Where is negative resistance region in this ? Ans: Everyone knows it Q.135How it behaves like an negative resistance oscillator ? Ans: If value of voltage is increased then current is decreased hence it is known as negative resistance

Q.136 Why after some time Tunnel behaves like a normal diode? Ans: After sufficient voltage both VB and CB go away from each other hence not at same energy level and it behaves like normal diode. Q.137 Relation between doping and position of Fermi Level Ans: If doping is increased Fermi level will enter in CB and VB respectively. If doping is decreased then Fermi Level will move towards Centre. Q.138 What are degenerate semiconductors ? Ans: Heavily doped SC are known as degenerate semiconductors Q.139 What is position of Fermi level in heavily doped N type and P type Semiconductors

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Ans: In Type it is inside the CB and in P type it is inside the VB

Q.140 UJT and Tunnel diode which one is voltage controlled or current controlled? Ans: UJT is current controlled while Tunnel is Voltage controlled Q.141 SCR and Triac are negative resistance device ? Ans: No Q.142 If No then what type of device they are? Ans: They are simple diode which work like a controlled rectifier or switch Q.143 Applications of SCR and Triac? Ans: Applications of Triac: 1.Motor speed regulation, 2. Temperature control& Illumination control,

3. Power switches Applications of SCR: 1. Power control

2. Switching

3. Battery charging regulator

4. Overvoltage protection Q.144 How will u design a prototype of a FM modulator and demodulator ? Ans: For FM Modulator you simply take PM and then uses Integrator and design FM. For FM take frequency discriminator followed by envelop detector ?

Q.145 What are the audio amplifiers used in modern audio devices ? Ans: It is basically Class –A amplifier by using either BJT or FET so that there will be minimum distortion.

Q.146 Tell a signal which does not have any harmonic? Ans: Constant signal

Q.147 What is channel coding ? and its type and methods? Ans: Channel coding can reduces error and codes for channel coding are block codes and convolution codes. It code data for transmission over a noisy communication channel. Increases size of data and add redundancy to identify and correct errors.

Q.148 What is source coding ? its types and methods? Ans: By this coding data rate is enhanced and a code word is assigned to each symbol and this code word is of variable length. It reduces size of data also. Its Lossy and lossless . Examples are Huffman and Shannon Fano. Q.149 Source coding is enhancing rate ? Ans: Yes Information is converted from symbols per second to bits per second. Q.150 How error is reduced by channel coding technique ? Ans: it deals with error control techniques. If the data at the output of a communications system has errors that are too frequent for the desired use, the errors can often be reduced by the use of ARQ and FEC methods. ARQ is Automatic Repeat Request and FEC is Forward Error Correction. Q.151 Which antenna in Normal phone ? Ans: Micro strip Patch Antenna

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Q.152 Which antenna is used in smart phone ? Ans: Planar Inverted F antenna Q.153 How OFC cables are connected ? Splicing ? Ans: By Method of splicing which may be done by mechanical or fusion Q.154 OFC sensors ? Ans: An optical fiber sensing system is basically composed of a light source, optical fiber; a sensing element or transducer and a detector .It uses optical fiber either as the sensing element ("intrinsic sensors"), or as a means of relaying signals from a remote sensor to the electronics. The principle of operation of a fiber sensor is that the transducer modulates some parameter of the optical system (intensity, wavelength, polarization, phase, etc.) which gives rise to a change in the characteristics of the optical signal received at the detector. Q.155 Which OFC is used for long distance and which is used for short distance ? Ans: Step for long and graded for short Q.156 Why Modulation is needed ? Ans: To reduce size of antenna and for proper multiplexing Q.157 Can You define Uniform Plane wave ? Ans: If Amplitude and phase both are constant throughout the plane then it is called UPW Q.158 What is power installed capacity in India ? Ans: 2,55,681 MW on 31.12.14 Q.159 How will you define plane wave and how will you define uniform plane wave ? Ans: Q.157 Q.160 What is propagation constant in Uniform plane wave ? Ans: it is K and decides direction of propagation of wave Q.161 What is cut-in voltage of Si and Ge Ans: 0.2 V for Ge and 0.7 V for Si Q.162 Why Si is better than Ge ?

Ans: Si is more thermal stable and due to formation of SiO2 which is insulator

Q. 163. How Si is more temperature stable than Ge Ans: It is due to atomic structure of Si which has configuration 2,8,4 so valance electrons are more tightly bounded to nucleus Q.1624How Antenna works ? How Transmission line is connected ? Ans: It is just like transducer where transmission line is matched with antenna Q.165 Difference between wave guide and transmission line ? Ans: wave guide is used at high frequency while transmission line at low frequency .Wave guide uses concept of E&H while transmission line uses concept of V&I Q.166 What is Electronics in Bullet train ? Ans: Superconductors are used for generating high value of magnetic field . Q.167 What are superconductors materials ? Ans: Materials whose resistivity decreases by decreasing the temperature Q.168 How satellites are placed ? Q. 169 Type of orbits in satellite ? Ans: Low earth orbit, High Elliptical orbit and Geosynchronous orbits Q.170 What is range of frequency of satellite ? Ans: from 1GHz-10 GHZ and 3GHz to 6 GHz for long distance Q.171 What is Bandwidth of satellite ? Ans: 500 MHz Q.172 How BJT works as an amplifier and how its gain changes ? Ans: In CE Mode If input is given at base and output at collector then it works like an amplifier. Q.173 Different types of biasing in BJT? Which one is the best and why ? Ans: Fixed ,Emitter stabilized and voltage divider.. Voltage divider is the best Q.174 How will you calculate your GATE score ?

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Ans: Q.175 What is the meaning of percentile in GATE Ans:

Q.176 What is full form of FPGA ? Ans: “Field Programmable GATE Array”

Q.177 what is FPGA ? Ans: It is an Integrated circuit designed after manufacturing hence it is known as Field Programmable i.e IC at user side.

Q.178 What is ASIC design ? Ans: It is Application Specific Designed Integrated circuit. I.e. IC designed for a specific purposes

Q.179 Difference between simulation and synthesis ? Ans: It uses the sensitivity list to figure out when it needs to run the process. Synthesis tools focus on logic design (FPGA, ASIC) and ignore sensitivity lists

Q.180 What are Engineers doing in VLSI in India? Ans: It is basically verification part and nothing related with manufacturing parts.

Q.181 When RC circuit acts as an differentiator ? Ans: If RC time constant is very small in compare to pulse width

Q.182If Square wave is given then what will be the output ? Ans: Impulses

Q.183If Pulse width of input is high then what is the output for a given input? Ans: same as above because time constant RC will be less in compare to input pulse width

Q.184 Can you design Differentiator circuits with OPAMP? Ans: yes By proper design of RC values

Q.185 Phase oscillators work for which frequency range ? Ans: Audio frequency range

Q.186What is CMOS switch ? Ans: will use both NMOS and PMOS and hence very less power dissipation. Q.187What is CMOS transmission gate ? Ans: A CMOS transmission gate can be constructed by parallel combination of NMOS and PMOS transistors, with complementary gate signals. The main advantage of the CMOS transmission gate compared to NMOS transmission gate is to allow the input signal to be transmitted to the output without the threshold voltage attenuation Q.188Why leakage current is less in CMOS? Ans: As at one time one MOS will be ON and other will be OFF hence it will be reverse current in it.

Q.189Why GSM is more popular than CDMA? Ans: In CDMA due to code generation there is no roaming facility hence it is less popular

Q.190. Frequency in GSM and CDMA? Ans: GSM(MHz) : 890-915 (UL) & 935-960(DL) CDMA: 824-849(UL)&869-894(DL)

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Q.191What is modulation used in GSM? Ans: GMSK Q.192What is multiplexing in GSM? Ans: Hybrid combination of FDMA and TDMA Q.193How it used FDM and TDM?

Ans: 1st

25 MHz frequency is divided into 200 channels and then every channel has given 8 time slots. Q.194Give physical examples of 1-D 2-D 3-D signals Ans: 1 D is sound 2 D is image and 3 D is video Q.195Sound is 1-D or 2-D Ans: It is 1D

Q.196What are anlog and digital sensor ? Q.197How will you convert Analog to Digital Q.198 Draw block diagram of A-D convertor ? Q.199What is fan beam and pencil beam and how will u differentiate between them? Q.200 Which technique is used when RADAR when you have to search object in less time.

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