MTT15 Time:03 Hours Booklet No: ________________ Max. Marks: 150

Roll No:_________________ Name of the Candidate: _________________________________________________________________ (in capital letters) Name of the Centre : __________________________________________________________________

Signature of the Candidate

Instructions 1. Fill up the information above with a Pen/Ball Point Pen (Black or Blue). 2. The answer sheet is placed inside the test booklet. Without breaking the seal of the Test Booklet, take the

Answer Sheet out. Don’t break open the seal until you are asked to do so. 3. There are 150 questions. Each correct answer gets a score of one mark. There is no negative marking. 4. Each question is followed by four answers. You should select one answer from A, B, C or D considered by

you as the most appropriate or correct answer and color the appropriate circle using a black or blue ball pen.

5. Do your rough work only on the blank pages provided at the end of the question booklet. 6. Mobile phones, calculators, calculator-watche s, slide rules, mathematical tables, etc. are not allowed in

the examination hall. 7. Make sure that you do not possess any pages (Blank or Printed) or any unauthorized material. If such

material is found in your possession during the examination, you will be disqualified from entrance examination.

8. If you are found copying/helping others you will be disqualified from the entrance examination. 9. Do not leave examination hall until you have recorded your attendance and submitted the Answer Sheet

to the Invigilator. 10. You are not allowed to leave the examination hall till the end of the examination. 11. Ensure that there are 36 pages in this Test Booklet (including front and back page). 12. At the end of examination, candidate is permitted to take the question booklet.

P.T.O

2

3

Useful constants

Electron mass (m0) : 9.10 × 10-31 kg

Electron charge (q) : 1.60 × 10-19 C

Planck’s constant (h) : 6.62 × 10-34 m2kg/s

Boltzmann constant (kB) : 1.38 × 10-23 J/K

Permittivity of free space ( ) : 8.85 × 10-12

F/m

Permeability of free space ( ) : 4π × 10-7 H/m

4

5

001. The solution of the differential equation given below with initial conditions 5)0(and40 y )y( is

02dd

dd

2

2

yx

y

x

y

A. xxy 2e)

23(

B. 2

e2x

y

C. xy 2e3 D. xxy 2e3e

002. If A=

, then A-1 = ?

A.

B.

C.

D.

003. (1+i)6 = ?

A. -4i

B. 16

C. 4i

D. - 8i

004. (logx xy) (logxy xy) = ?

A. 1

B. x

C. y

D. xy

6

005. The trigonometric Fourier series of an even function does not have the

A. dc term B. sine terms C. cosine terms D. odd harmonic term

006. The Fourier transform of

, where is unit step function is

A.

B.

C.

D.

007. From a group of 10 persons consisting of 5 lawyers, 3 doctors and 2 engineers, four

persons are selected at random. The probability that the selection contains at least one of each category is

A. B. C. D.

008. The Laplace transform of the function is

A.

B.

C.

D.

7

009. Determinant of

is

A. 0 B. 1 C. D.

010. The eigenvalues of the matrix

are

A. 0, 1, 1 B. 0, ± C. 0, 1, 2 D. 0, ±

011. The series

(for : -1< x < 1)

coresponds to the the expansion of

A. B.

C.

D.

012. Which of the following function represents the graph shown in figure?

A. 12 xy

B. x

y1

C. 1 xey

D. xey

013. implies that

A. all the three vectors are parallel B. all the three vectors are mutually perpendicular C. all the vectors lie in a same plane D. two of the three vector are perpendicular

x

y

8

014. The average of the function in the interval is

A.

B.

C.

D. 0

015. Divergence of the function, 2 3V xy i yz j zx k at the point 1,1,2 is

A. 1 B. 2 C. 3 D. -1

016. The maximum value of 5249)( 23 xxxxf in the interval [1,6] is

A. 46 B. 25 C. 41 D. 21

017. The values of a, b, c such that 3 4 5 2 7A x y az i cx y z j x by z k A x y az i cx y z j x by z kA x y az i cx y z j x by z k3 4 5 2 7A x y az i cx y z j x by z k3 4 5 2 7A x y az i cx y z j x by z k A x y az i cx y z j x by z kA x y az i cx y z j x by z k A x y az i cx y z j x by z k A x y az i cx y z j x by z k A x y az i cx y z j x by z k3 4 5 2 7A x y az i cx y z j x by z k3 4 5 2 73 4 5 2 7A x y az i cx y z j x by z k3 4 5 2 7 3 4 5 2 7A x y az i cx y z j x by z k3 4 5 2 7 3 4 5 2 7A x y az i cx y z j x by z k3 4 5 2 7 is irrotational, are, respectively

A. -4, 2, 1 B. 2, 1, -4 C. -1, 2, -4 D. 1, 2, -4

018. Which one of the following matrices is Hermitian?

A. 0

0i

i

B. 0

0i

i

C. 0

0i

i

D. 0

0i

i

9

019. The Fourier transform of is

A. 2

816

B. 2

816

C. 2

416

D. 2

416

020. Find

=

A.

B.

C.

D.

021. If the Newton Raphson Method is used to find the positive solution of the equation

xxf(x) sin2 , the iteration equation is

A. n

nnnn

x

xxxx

cos21)cos(sin2

1

B. n

nnnnn

x

xxxxx

cos21)cossin22

1

C. n

nnnn

x

xxxx

cos21)cos(sin2

1

D. n

nnnnn

x

xxxxx

cos21)cos(sin2

1

022. In C language, what is the output of the following code ?

main() { int i=-3,j=2,k=0,m; m=++i&&++j||++k; printf("\n%d%d%d%d",i,j,k,m); }

A. -3 3 1 1 B. -2 3 1 1 C. -2 3 0 1 D. -2 3 0 0

10

023. In C language, what is the output of the following code, assume location of integer ‘i’ is 1002? main() { int i=3; int *j; j=&i; printf("\n%u%u%u",j,*j,*(&i)); }

A. 1002 3 3 B. 1004 3 1002 C. 1004 1002 3 D. 3 3 3

024. In C language, what is the output of the following code?

int main() { int i=3, *j, k; j = &i; printf("%d\n", i**j*i+*j); return 0; }

A. 27 B. 9 C. 30 D. 3

025. In C language, the statement used to send back any value to the calling function is

A. return B. continue C. break D. exit

026. The process of repeating a group of statement in an algorithm is known as

A. sequence B. flow C. selection D. iteration

027. Simplify the Boolean Expression F = C (B +C) (A+B+C)

A. A B. B C. C D. 1+AB

11

028. The loop in which the statements within the loop are executed at least once is called

A. while B. do-while C. for D. if

029. The control automatically passes to the first statement after the loop in

A. break statement B. continue statement C. switch statement D. if statement

030. ‘C’ allows a three-way transfer of control with the help of

A. unary operator B. relational operator C. comparison operator D. ternary operator

031. In C language, if and then the statement

A. assigns a value 5 to p B. assigns a value 7 to p C. gives an error message D. assigns a value 8 to p

032. Which of the following is FALSE in C?

A. Keywords can be used as variable names B. Variable names can contain a digit C. Variable names do not contain a blank space D. Capital letters can be used in variable names

033. A typical modern computer uses

A. magnetic tape for primary memory B. more than 10, 000 vaccum tubes C. magnetic cores for secondary storage D. LSI chips

034. Which of the following memories has shortest access time?

A. Magnetic Bubble Memory B. Magnetic Core Memory C. Cache Memory D. RAM

12

035. Which of the following statements should be used to obtain a remainder after dividing 3.14 by 2.1 in C language?

A. rem = fmod(3.14, 2.1); B. rem = 3.14 % 2.1; C. rem = modf(3.14, 2.1); D. Remainder cannot be obtain in floating point division.

036. How would you round off a value from 1.66 to 2.0 in C language?

A. roundoff(1.66) B. roundup(1.66) C. floor(1.66) D. ceil(1.66)

037. A computer program that converts entire program into machine language is called

A. Interpreter B. Simulator C. Compiler D. Commander

038. The ALU of a computer responds to the commands coming from

A. Control section B. Primary memory C. External memory D. Cache memory

039. A bulb rated at 60W, 120V is used for 30 minutes. The charge associated with this

operation is

A. 3600 C B. 7200 C C. 60 C D. 900 C

040. The current wave shape shown in figure (a) is applied to a circuit element. The voltage across the element is shown in figure (b). The element is

Figure (a) Figure (b)

i

0 4S t

V

0 4S t

13

A. an inductor B. a resistor C. a capacitor D. a semiconductor

041. In a purely capacitive circuit, the phase relationship between current and voltage is

A. voltage leads the current by 90. B. current leads the voltage by 180. C. current leads the voltage by 90. D. voltage leads the current by 180.

042. If an impedance ZL is connected across a voltage source V with source impedance Zs,

then for maximum power transfer, the load impedance must be equal to

A. source impedance, Zs B. real part of Zs C. imaginary part of Zs D. complex conjugate of Zs

043. A two-port network is reciprocal for which of the following condition

A. Z11 = Z22 B. AD-BC = -1 C. BC-AD = -1 D. h12 = h21

044. A series LCR circuit has a resonance frequency of 1 kHz and a quality factor of

Q = 100. If each of R, L and C is doubled from its original value, the new Q of the circuit is

A. 25 B. 100 C. 200 D. 50

045. An circuit consists of a resistance, R=20 k, inductance L=250 mH in series with a 40 mV battery and switch. If the switch is closed at 0t , the current in the circuit varies with time as

A.

B.

C.

D.

14

046.

If the Laplace transform of the voltage across a capacitor of value 0.5 F is

The value of the current through the capacitor at t= 0+ is

A. 0 A B. 2 A

C.

A

D. 1 A

047. A ramp voltage, V(t) = 100t volts is applied to an RC differentiating circuit with R = 5 kΩ and C = 4µF. The maximum output voltage is

A. 0.2 V B. 10 V C. 2 V D. 50 V

048. Two port networks are connected in cascade. The combination is to be represented as a

single two-port network, by multiplying the individual

A. ABCD parameter B. Z- parameter matrices C. h- parameter matrices D. Y- parameter matrices

049. The average power delivered to an impedance (4-3j)Ω by a current 5cos(100πt +100) A

is

A. 44.2 W B. 62.5 W C. 50 W D. 125 W

050. The transfer function of the circuit given below in Laplace domain is

A.

B.

15

C.

D.

051. The poles of the impedance Z(s) for the network shown below will be real and

coincident if

A.

B.

C.

D.

052. The current in the network given below is,

A.

B.

C. D.

053. A network N is to be connected to load of 500 ohms. If the Thevenin’s equivalent voltage and Norton’s equivalent current of N are 5Volts and 10mA respectively, the current through the load is

A. B. C. D.

054. A voltage of volt is applied to an inductance of . The instantaneous

power in watts across the inductor is

A. B. C. D.

16

055.

Find the transmission parameters for a two port network, if the ‘Z’ parameters are given by

A.

B.

C.

D.

056. A graph of an electrical network has 3 nodes and 9 branches. The number of links (l) ,

with respect to the chosen tree, would be

A. 7 B. 6 C. 5 D. 8

057. A capacitor is connected in parallel with a capacitor and the

combination is connected across a time varying voltage source. At a particular time, the current supplied by the source is 5 A. The magnitude of instantaneous currents through the individual capacitors is

A. B. C. D.

058. Energy stored in the capacitor of shown in the circuit under dc conditions is

A. µ B. µ C. D. µ

059. If each of the resistances in the network shown below is R, what is the resistance between terminals A and B?

A. 2R B. R/2 C. R/3 D. R

17

060. In a series RLC circuit with , L=1 H and

, the resonant frequency is

A. Hz 102 4 B. Hz 10 4

C. Hz 101 4

D. Hz 102 4

061. The induced electric field at x = 0 in an n-type semiconductor in thermal equilibrium at 300K due to linear variation in donor doped concentration for the range is

A. 51.8 V/cm B. 12.8 V/cm C. 25.9 V/cm D. 0 V/cm

062. For a built-in potential of 0.63 V in silicon based p-n junction, the total space charge

region width is 0.95 µm. The maximum electric field present in the junction is

A. -6.60 × 103 V/cm B. -3.32 × 103 V/cm C. -1.32 × 104 V/cm D. 0 V/cm

063. In an n-channel MOSFET, the velocity of an electron is 1.57 107 cm/s. If the length of

the channel is 4 m, the maximum operating frequency is

A. 3 GHz B. 6.25 GHz C. 3.45 GHz D. 2.75 GHz

064. For a 0.6 µm thick n-channel GaAs MESFET, the estimated internal pinch-off voltage is

0.5 V. If the thickness of channel is increased by 20%, the internal pinch-off voltage is

A. 1.0 V B. 0.34 V C. 0.72 V D. 0.41 V

065. The high input impedance of Junction Field Effect Transistor (JFET) amplifier is due to

A. the source and drain being far apart B. its very low gate current C. the pinch-off voltage D. the geometry of the FET

18

066. If the energy of an electron is greater than ' ' above the Fermi energy, the electron is called

A. cold electron B. hot electron C. reduced mass electron D. None of the above

067. If the mobility of electrons in an n- type semiconductor is 3125 cm2V-1sec-1, the required

density of donor atoms to make an intrinsic germanium specimen to a n-type semiconductor of conductivity 5 mho/cm is

A. 0.51 1016 cm-3 B. 1 1016 cm-3 C. 1.6 1016 cm-3 D. 0.75 1016 cm-3

068. The effective mass of an electron in density of states of a semiconductor

A. can be increased or decreased B. can never be decreased C. can never be increased D. depends on its spin

069. A doped germanium crystal of length 2 cm, breadth 1 cm and width 1 cm, carries a

current of 1 mA along its length parallel to +x axis. A magnetic field of 0.5 T is applied along +z axis and the Hall voltage of 6 mV is measured with negative polarity at y = 0 plane. The Hall resistance is

A. -1.5 m B. -0.12 m C. 1.1 m D. 2.3 m

070. The power in Gunn diode based oscillator is

A. inversely proportional to f2 B. directly proportional to f2

C. inversely proportional to f D. directly proportional to f

071. The mobility of charge carriers in a semiconductor due to ionized impurities is

A. directly proportional to T

3/2 B. inversely proportional to T

3/2 C. directly proportional to T

1/2 D. directly proportional to T

5/2

19

072. The intrinsic carrier concentration of germanium at room temperature is 2.5 1019 m-3. It is doped with phosphorus at a rate of 1 phosphorus atom per million atoms of germanium. If the concentration of germanium atoms is 5 1028 m-3 for complete ionization of phosphorus atoms, the hole concentration is

A. 7.25 1016 m-3 B. 8.65 1016 m-3 C. 4.05 1016 m-3 D. 1.25 1016 m-3

073. In an n type GaAs at T = 300 K, the electron concentration varies linearly from 1 1018

to 7 1017 cm3 over a distance of 0.10 cm. If the electron diffusion coefficient Dn = 225 cm2/s, the diffusion current density is

A. 0.48 A/cm2 B. 1080 A/ cm2 C. 108 A/cm2 D. 48 A/cm2

074. Under low level injection assumption, the injected minority carrier current for an

extrinsic semiconductor is essentially the

A. drift current B. diffusion current C. recombination current D. induced current

075. What is the dielectric relaxation time constant for carrier in n-type doped Si with

conductivity of 1.17 / Ω-cm? (Assume permittivity of Si is 11.7)

A. 6.093 ps B. 0.885 ps C. 0.596 ps D. 22.264 ps

076. A system has a receiver noise of 50 . It is connected to an antenna with an input resistance of 50 . The noise figure of the system is

A. 1 B. 50 C. 2 D. 101

077. The carrier signal c(t) and the message signal m(t) are used to generate an AM signal.

The modulation index of the generated AM signal is 0.5. The quantity

is

A. 1/4 B. 1/6 C. 1/2 D. 1/8

20

078. The power transmitted in lower side band of an AM signal with total power content as 1000 W and the percentage modulation being 100 % is:

A. 250 W B. 166.6 W C. 333 W D. 500 W

079. An RF amplifier with a gain of 20 dB and a noise factor of 2.5 is operating over a

bandwidth of 30 MHz at 27 oC. The noise power at the output of this amplifier is

A. 33.57 pW B. 28.96 pW C. 31.05 pW D. 40.34 pW

080. An amplifier operating over the frequency range from 7 to 14 MHz has a 700 input

resistance at the ambient temperature 27 oC. The rms noise voltage at the input to this amplifier is

A. 9 µV B. 7 µV C. 10 µV D. 15 µV

081. Nyquist bandwidth in case of a PCM sampling at 8000 sample/s and using 6-bits/word

for transmission is

A. 24 kHz B. 30 kHz C. 12 kHz D. 18 kHz

082. In a PCM system, 24 telephone channels, each limited to band 3.4 kHz are time

multiplexed for 128 quantization levels and 8 kHz sampling frequency. The bandwidth in this PCM system is nearly

A. 1.5 MHz B. 1.0 MHz C. 2.5 MHz D. 3.1 MHz

083. For a QPSK signal, the baud rate for a bit rate of 800 bps is

A. 100 B. 450 C. 400 D. 200

21

084. A communication channel has a bandwidth of 100 MHz. The channel is extremely noisy such that the signal power is very much below the noise power. The capacity of this channel is

A. 50 Mbps B. nearly 0 bps C. 100 Mbps D. 2400 bps

085. Johnson noise voltage is 0.25 µV for a receiver operating in a bandwidth of 3 kHz at

27 C temperature. In bandwidth of 48 kHz, the same receiver has a Johnson noise voltage of

A. 2.25 µV B. 0.25 µV C. 1 µV D. 0.5 µV

086. A phase modulation transmitter is operating with a carrier of frequency 100 MHz and

carrier voltage of 8 V. The modulating signal has amplitude of 2 V and a frequency of 6 kHz resulting in a deviation of 60 kHz. The phase modulated voltage equation is

A. π π B. π π C. π π D. π π

087. A BPSK modulator is operating with a carrier frequency of 70 MHz and an input bit rate of 10 Mbps. The maximum upper side and minimum lower side frequencies are

A. 75 MHz, 65 MHz B. 70 MHz, 65 MHz C. 75 MHz, 60 MHz D. 70 MHz, 60 MHz

088. In a 16-bit QAM modulator, an input data rate fb is equal to 10 Mbps and a carrier

frequency of 70 MHz. The minimum Nyquist bandwidth is

A. 1.25 MHz B. 5 MHz C. 2.5 MHz D. 7.5 MHz

22

089. A 8-bit PSK system is operating with an information bit rate of 24 kbps. The bandwidth efficiency of this system is

A. 3 bits/s/Hz B. 8 bits/s/Hz C. 6 bits/s/Hz D. 4 bits/s/Hz

090. For a system having 1 Hz bandwidth, the noise power at room temperature (T = 27 C)

is -174 dBm . If the band width of this system increases to 10 MHz, the noise power is

A. -104 dBm B. -70 dBm C. -174 dBm D. 0 dBm

091. An earth station transmitter is transmitting an output power of 40 dBW with the help of

antenna of 40 dB gain. The backoff loss and the total branching and feeder losses are 3 dB each. The effective isotropic radiated power of transmitter is

A. 44 dBW B. 64 dBW C. 57 dBW D. 74 dBW

092. For a binary FSK signal with a mark frequency of 49 kHz, a space frequency of 51 kHz, and an input bit rate of 2 kbps, the minimum bandwidth of the signal will be

A. 2 kHz B. 4 kHz C. 6 kHz D. 8 kHz

093. In amplitude modulation, the efficiency () for 50% modulation is

A. 50 % B. 22.22 % C. 11.11 % D. 19.6 %

23

094. In the circuit shown below, the input signal of first AM modulator is message signal m(t) and input signal of second AM modulator is inverted m(t). The final output S(t) is

A. B. C. D.

095.

In SSB-SC technique, the modulation index is decreased from 100% to 70 %. The percentage saving in the side band power is

A. 30 % B. 70 % C. 68 % D. 51 %

096. A Doppler radar operating at 12 GHz is intended to detect target velocities ranging from 1 to 20 m/s. The required passband of the Doppler filter is

A. B. C. D.

097. Two amplifiers each with 40 dB gain are connected in cascade. The noise figure of first

amplifier is 10 dB and second amplifier is 20 dB. The overall noise figure of the cascaded system is

A. B. C. D.

m(t) -m(t) Inverted

AM modulator

AM modulator

Oscillator

m(t)

)(tm

tcosωV cc

tcosωV cc

S(t)

+

-

-

-

24

098. A FM wave is represented by the voltage equation The maximum frequency deviation of this FM wave is

A. B. C. D.

099. The antenna current of an AM transmitter is 8 A when only the carrier is sent, but it

increases to 24 A when the carrier is modulated by a single sine wave. The modulation index of AM wave is

A. B. C. D.

100. Twenty four voice signals are sampled uniformly and then time division multiplexed.

The highest frequency component for each voice signal is 3.4 kHz. The bit rate of the system is 1.5 Mbps. If the signals are pulse code modulated with an 8 bit encoder, the sampling rate is

A. B. C. D.

101. Which type of error detection technique uses binary division?

A. Check sum checking B. Parity check C. Longitudinal redundancy checking D. Cyclic redundancy checking

102. The sequence of the binary digits representing the outcomes of parity checks in

Hamming codes is known as

A. look up entry B. syndrome C. hamming distance D. radix

103. Rather than sending the absolute value of each sample, it is possible to achieve a smaller

transmission bit rate by sending the difference between consecutive samples. This is known as

A. delta sigma modulation B. delta modulation C. adaptive delta modulation D. pulse code modulation

25

104. On which of the following parameter/s does the effective propagation of a signal through wireless medium depend?

A. Medium through which the signal propagates B. Antenna size only C. Signal wavelength only D. Relative size of antenna and signal wavelength

105. In the circuit shown below, the npn transistor Q has a very high value of . The

required value of R2 in k to produce Ic=1 mA is

A. 30 B. 10 C. 20 D. 40

106. A coaxial cable is made of two brass conductors. The spacing between the conductors is filled with Teflon ( 0tan ,1.2 r ). Which of the following circuits can represent the lumped element model of a small length z of the cable?

A.

B.

C.

D.

26

107. Which of the following represents the electric field lines of the TE02 mode of the rectangular waveguide shown in the figure?

108. Consider a 3 m long air filled lossless transmission line with characteristic impedance of 50 . If it is terminated by a short circuit and is excited with the frequency of 37.5 MHz, the input impedance iZ is

A. capacitive B. open C. short D. inductive

109. A plane wave propagating in air with V/m is incident on a perfectly conducting slab positioned at 0x . The E

of the reflected wave is given by

A. V/m B. V/m C. V/m D. V/m

110. A 25 dBm power in Watts is equal to

A. 0.96 W B. 0.316 W C. 0.4 W D. 0.16 W

111. If is the amplitude attenuation coefficient in nepers/m of a propagating

electromagnetic wave, the attenuation in dB/m is

A. 434.0 B. 343.4 C.

8686.0

D. 686.8

D.

A.

B.

C.

27

112. For a lossy distortionless transmission line, the attenuation coefficient is given by

A. LC B. RG

C. G

R

D. R

G

113. A pure resistance RL when connected at the load end of a 100 ohm transmission line

produces a VSWR of 2. The value of RL in ohms can be

A. only 50 B. only 200 C. 400 or 200 D. 50 or 200

114. If the impedance of a series resonant circuit is inductive at f = 1000 Hz, it will be

capacitive at some frequency f, where

A. f > (1000- f0) Hz B. f = 1000 +f0 Hz, where f0 is the resonance frequency C. f < (1000- f0) Hz D. f = f0 Hz, where f0 is the resonance frequency

115. A parallel RLC resonant circuit has R = 4 , L = 4 H and C = 0.25 F. The value of Q of

the circuit is

A. 4 B. 10 C. 1 D. 20

116. The modes of a rectangular waveguide are denoted by TEmn or TMmn where m and n

define the number of half cycles along the larger and smaller dimensions respectively. Which of the following statements is TRUE?

A. The TE10 mode does not exist B. The TM10 and TE10 modes both exist and have the same cut-off frequency C. The TM10 and TM01 modes both exist and have the same cut-off frequency D. The TM10 mode does not exist

117.

The input impedance of a short circuited transmission line of length λ/8 having Z0 = 50 Ω is

A. j 50 2 Ω B. j 400 Ω C. j50 Ω D. j 50 2 Ω

28

118. A transmission line has a characteristic impedance of 50 Ω and a resistance of 0.1Ω/m. If the line is distortionless, the attenuation constant (in Np/m) is

A. 0.002 B. 500 C. 5 D. 0.014

119. A lossless transmission line is terminated in a load which reflects a part of the incident

power. The measured VSWR is 2. The percentage of the power that is reflected back is

A. 11.11 B. 33.33 C. 0.11 D. 57.73

120. The capacitance per unit length and the characteristic impedance of a lossless

transmission line are C and Z0 respectively. The phase velocity of travelling wave on the transmission line is

A. oZ C

B. o

C

Z

C. 1

oZ C

D. oZ

C

121. The input impedance of a lossless transmission line is 100 Ω when terminated in a short

circuit and 64 Ω when terminated in an open circuit. The characteristic impedance of the line is

A. 164 Ω B. 36 Ω C. 64 Ω D. 80 Ω

122. A sinusoidal electric field intensity of amplitude 250 V/m with frequency 1 GHz exists

in a lossy dielectric medium of effective conductivity 1.39 × 10-4 S/m. The power dissipated per unit volume is

A. 8.68 W/m3 B. 1.62 W/m3 C. 4.34 W/m3 D. 3.86 W/m3

29

123. If the electrostatic potential at a point is given by volt, the electrostatic energy density at that point (in J/m3) is

A. B.

C. D.

124. The minimum frequency of an electromagnetic wave, which can propagate along a

hollow, metallic waveguide whose cross-section is a square of side W (c is the velocity of light) is

A.

B.

C.

D.

π

125. The time average Poynting vector is related to the amplitude of the electric field by the following relation

A. 00EcS

B. 2002

Ec

S

C. 200ES

D. 002E

cS

126. A quarter wave transformer designed using a dielectric (r = 9) filled coaxial line is

required to transform load impedance ZL= 120 to input impedance Zin= 50 at 2 GHz. The length of this transformer is

A. 4.16 mm B. 112.5 mm C. 12.5 mm D. 50 mm

30

127. Frequency tuning in a reflex klystron is obtained by varying

A. positive voltage applied to the anode B. negative voltage applied to the cathode C. RF signal applied to RF output electrode D. negative voltage applied to the repeller

128. A parabolic antenna is operating at 5 GHz and has a half power point beamwidth of 10.

The antenna power gain as a ratio is

A. 490 B. 294 C. 160 D. 320

129. A pyramidal horn antenna has aperture dimensions of 12 6 cm and is operating at

5 GHz. The beamwidth of this antenna is

A. 7.5 B. 15 C. 12.5 D. 20

130. An air-filled rectangular waveguide has cross-section dimensions of width a = 25 mm

and height b = 11 mm. The characteristic impedance of the dominant mode at 10 GHz is

A. 471.25 B. 301.6 C. 62.50 D. 40

131. A lossless transmission line with characteristic impedance 100 is excited by a signal

of voltage 100 V at 1.2 MHz. If the line is terminated by ZL(= Z0 ) at a distance 1 km, the voltage in volts at the midpoint of the line is

A. 410 je

B. 820 je

C. 45 je

D. 8100 je

132. An air-filled rectangular waveguide section of length 1.5 cm is used as a quarter wave

transformer at operating frequency of 10 GHz. The broad dimension of a waveguide in its dominant mode is

A. 2.28 cm B. 1.50 cm C. 1.73 cm D. 3.07 cm

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133. A lossless 50 coaxial air line is terminated with a short load. The successive first two voltage minimas are at 1.25 cm and 7.25 cm from the load end. The frequency of operation is

A. 3.0 GHz B. 1.5 GHz C. 2.5 GHz D. 3.5 GHz

134. In a microwave mixer, the incoming RF signal and a local oscillator signals are fed to

A. E-arm and H-arm, respectively B. E-arm and one-collinear arm, respectively C. H-arm and one-collinear arm, respectively D. Both collinear arm.

135. Two coaxial cables are filled with different dielectric constants εr1 and εr2 respectively.

The ratio of the wavelengths in the two cables (λ1/ λ2) is

A. 1 2r r

B. 1 2r r C. 2 1r r

D. 2 1r r

136. In an impedance Smith chart, a clockwise movement along a constant resistance circle gives rise to

A. decrease in the value of reactance B. no change in the reactance value C. increase in the value of reactance D. no change in the impedance value

137. If the electric field intensity associated with a uniform plane electromagnetic wave

travelling in a perfect dielectric medium is given by V/m, the velocity of the travelling waves is

A. 3 108 m/sec B. 6.2 108 m/sec C. 2 107 m/sec D. 2 108 m/sec

138. A rectangular metal wave guide filled with a dielectric material of relative permittivity

εr = 4 has the inside dimensions 3.0 cm 1.2 cm. The cut-off frequency for the dominant mode is

A. 5.0 GHz B. 10.0 GHz C. 2.5 GHz D. 12.5 GHz

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139. In the case of reflection and refraction of light at the dielectric interface

A. tangential components of D and B are continuous B. tangential components of D and normal component of B are continuous C. normal components of D and B are continuous D. normal components of D and tangential component of B are continuous

140. An electromagnetic wave is propagating in free space in the z direction. If the electric

field is given by where , the magnetic field is

A.

B.

C.

D.

141. A parallel plate capacitor with plate area 5 cm2 and plate separation 3 mm has a voltage

of 50sin103t applied to its plates. If ε = 2εo, the displacement current is

A. 210 cos 103t nA B. 150 sin 103t nA C. 120 cos 103t nA D. 147 cos 103t nA

142. In a non magnetic medium for which 74sin 2 x10 0.8E t x k E t x k4sin 2 x10 0.8E t x k4sin 2 x10 0.84sin 2 x10 0.8E t x k4sin 2 x10 0.8E t x k V/m, the value of εr is A. 14.5 B. 42.5 C. 11.5 D. 22.5

143. A 250 MHz, 40 V peak signal is incident on a 72 transmission line. The phase

velocity of the signal in this transmission line is 0.8c, where c is speed of light. The wavelength of the signal on line is

A. 1.2 m B. 0.24 m C. 1.5 m D. 0.96 m

144. A quarter wave transformer is used for the purpose of matching a 100 load to a

transmission line having L = 1.35 H/m and C = 60 pF/m. The characteristic impedance of matching transformer is

A. 377 B. 100 C. 150 D. 122. 47

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145. A radar pulse sent to a target returns after 20 s. The distance of the target from the radar is

A. 3 km B. 2.4 km C. 10.8 km D. 1.5 km

146. The propagation coefficient for a transmission line is (0.0005 + j π/10) m-1. The

attenuation in nepers for a 50 m line is

A. 0.0005 Np B. 0.217 Np C. 25 Np D. 0.025 Np

147. A plane wave with V/m is propagating in a medium with

r = 1. The wave impedance of the medium is

A. 377 B. 120 C. 0 D. 72

148. An optical fibre cable with 0.25 dB/km loss is connected to 0.1 mW light source. The

optical power at 100 km from the source is

A. -25 dBm B. -10 dBm C. -35 dBm D. 0 dBm

149. A transmission line is connected to a load of reflection coefficient 0.2. If the measured

voltage across the load is 30V, the incident voltage is

A. 150 V B. 15 V C. 100 V D. 25 V

150. Radiation resistance of a dipole antenna

long is

A. 80 B. 12 C. 5.5 D. 7.9

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SPACE FOR ROUGH WORK

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SPACE FOR ROUGH WORK