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Delhi University Entrance Test (DUET) 2020 Previous Year Question Paper With Answer Key

This post was last modified on 27 December 2020

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DUET Last 10 Years 2011-2021 Question Papers With Answer Key || Delhi University Entrance Test conducted by the NTA

DUMTech Microwave Electronics

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Topic: ME MTECH S2

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A family of arcs is obtained in the Smith chart by varying normalized reactance in a range of, [Question ID = 4165]
1. 0 to 1 [Option ID = 16654]
2. -8 to +8 [Option ID = 16655]
3. 0 to +8 [Option ID = 16656]
4. -1 to 0 [Option ID = 16657]
Correct Answer :-
- -8 to +8 [Option ID = 16655]
A 75 O quarter wave transformer is connected to a 125 O TV receiver. The impedance at the input of this transformer will be, [Question ID = 4166]
1. 25 O [Option ID = 16658]
2. 45 O [Option ID = 16659]
3. 75 O [Option ID = 16660]
4. 100 O [Option ID = 16661]
Correct Answer :-
- 45 O [Option ID = 16659]
If a coaxial line has dimensions a × b cm, the conductivity of the conductors is s and the permittivity of the filled medium is e. Conductance per unit length of this coaxial transmission line is given as, [Question ID = 4167]
1. 2ps
  ln(b/a) [Option ID = 16662]
2. 2pe
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  ln(b/a) [Option ID = 16663]
3. 1
  2psln(b/a) [Option ID = 16664]
4. 1
  2peln(b/a) [Option ID = 16665]
Correct Answer :-
- 2ps
  ln(b/a) [Option ID = 16662]
A lossless transmission line used in a TV Receiver has a capacitance of 50 pF/m and an inductance of 20 nH/m. The characteristic impedance of a 10 meter long line will be then, [Question ID = 4168]
1. 50 O [Option ID = 16666]
2. 20 O [Option ID = 16667]
3. 40 O [Option ID = 16668]
4. 100 O [Option ID = 16669]
Correct Answer :-
- 20 O [Option ID = 16667]
A one-half wavelength lossless line of 50 O is terminated to a load impedance of 50+j50 O, its input impedance is, [Question ID = 4169]
1. 50+j50 O [Option ID = 16670]
2. 50-j50 O [Option ID = 16671]
3. 25+j25 O [Option ID = 16672]
4. 25-j25 O [Option ID = 16673]
Correct Answer :-
- 50+j50 O [Option ID = 16670]

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ZL
If a line of characteristic impedance Zo is connected to a load of impedance ZL, then the normalized load impedance
Zo at a distance d is equal to, [Question ID = 4170]
1. 1-G(d)
  1 + G (d) [Option ID = 16674]
2. G(d)
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  1- G(d) [Option ID = 16675]
3. G (d)
  1 + G (d) [Option ID = 16676]
4. 1+ G (d)
  1-G(d) [Option ID = 16677]
Correct Answer :-
- 1+ G (d)
  1-G(d) [Option ID = 16677]
A copper rectangular cavity resonator is structured by 3x4x1 cm³. The resonant frequency for TM110 mode, is [Question ID = 4171]
1. 6.25 GHz [Option ID = 16678]
2. 5.81 GHz [Option ID = 16679]
3. 8.65 GHz [Option ID = 16680]
4. 2.04 GHz [Option ID = 16681]
Correct Answer :-
- 6.25 GHz [Option ID = 16678]
A transmission line of characteristics impedance Zo is terminated in a load having VSWR=2. The normalized load impedance Zn of the transmission line is [Question ID = 4172]
1. Zo [Option ID = 16682]
2. 1 [Option ID = 16683]
3. 0 [Option ID = 16684]
4. 2 [Option ID = 16685]
Correct Answer :-
- 2 [Option ID = 16685]

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In a Square coaxial transmission line shown in Fig., if the space between the conductors is filled with a material having a relative permittivity of 4.0 and the capacitance per unit length is 6.3 e F/m, the characteristic impedance of this line will be,
2 mm
2 mm
4 mm [Question ID = 4173]
1. 30 O [Option ID = 16686]
2. 50 O [Option ID = 16687]
3. 40 O [Option ID = 16688]
4. 20 O [Option ID = 16689]
Correct Answer :-
- 30 O [Option ID = 16686]
A parabolic antenna is operating at 5 GHz and has an antenna power gain of 216. The diameter of this antenna is [Question ID = 4174]
1. 8 cm [Option ID = 16690]
2. 16 cm [Option ID = 16691]
3. 25 cm [Option ID = 16692]
4. 36 cm [Option ID = 16693]
Correct Answer :-
- 36 cm [Option ID = 16693]

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If a signal of 30 MHz is transmitted through a coaxial cable, which has a capacitance of 40 pF/m and an inductance of 900 nH/m. The propagation velocity for a 1m long cable is given by, [Question ID = 4175]
1. 2.36×10⁸ m/s [Option ID = 16694]
2. 1.66×10⁸ m/s [Option ID = 16695]
3. 2.66×10⁸ m/s [Option ID = 16696]
4. 1.33×10⁸ m/s [Option ID = 16697]
Correct Answer :-
- 1.66×10⁸ m/s [Option ID = 16695]
A perpendicularly polarized wave is incident at an angle of ?i = 15° and it is propagating from medium 1 to medium 2. Medium 1 is characterized by er1 = 9, µr1 = 1, s1= 0 and medium 2 is a free space. If the electric field intensity E1 = 3.0 mV/m, the value of the magnetic field intensity Hi, will be, [Question ID = 4176]
1. 23.87 µA/m [Option ID = 16698]
2. 48.53 µA/m [Option ID = 16699]
3. 15.46 µA/m [Option ID = 16700]
4. 10 µA/m [Option ID = 16701]
Correct Answer :-
- 23.87 µA/m [Option ID = 16698]
If capacitor plates of area 'A' are placed 'd' distance apart and the capacitor is filled with a material having dielectric constant e, then the current through this capacitor is expressed as, [Question ID = 4177]
1. e dV
  Ad dt [Option ID = 16702]
2. Ad dV
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  e dt [Option ID = 16703]
3. eA dV
  d dt [Option ID = 16704]
4. d dV
  eA dt [Option ID = 16705]
Correct Answer :-
- eA dV
  d dt [Option ID = 16704]
For a 4 GHz wave propagating in a free Space, the propagation constant of this wave will be, [Question ID = 4178]
1. j 3.14 [Option ID = 16706]
2. j 5.53 [Option ID = 16707]
3. j 2.09 [Option ID = 16708]
4. j 10.8 [Option ID = 16709]
Correct Answer :-
- j 2.09 [Option ID = 16708]
A transmission line of characteristic impedance Zo terminated by a load R= (1/2)Zo as shown in Fig., is connected to a matched source by a switch for a short time t to produce a pulse on the line.
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V
Zo
A
B
S
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Zo
Zo/2
If the propagation time along the line is T, where T > t, the values of the reflection coefficient at point A and point B are, respectively [Question ID = 4179]
1. 1, -1/3 [Option ID = 16710]
2. 1, -1 [Option ID = 16711]
3. 2, -1 [Option ID = 16712]
4. 1/2, -1/2 [Option ID = 16713]
Correct Answer :-
- 1, -1/3 [Option ID = 16710]
? /4 transformer is connected in between generator and load, which have impedence ratio ZL / ZG =0.16 and ZG = 50 O. The characteristic impedance of a ? /4 transformer is [Question ID = 4180]
1. 8 O [Option ID = 16714]
2. 20 O [Option ID = 16715]
3. 312 O [Option ID = 16716]
4. 25 O [Option ID = 16717]
Correct Answer :-
- 20 O [Option ID = 16715]
The input power needed to generate an output power of 3 W from an amplifier with a power gain of 30 dB is [Question ID = 4181]
1. 1 W [Option ID = 16718]
2. 100 mW [Option ID = 16719]
3. 1 mW [Option ID = 16720]
4. 3 mW [Option ID = 16721]
Correct Answer :-
- 3 mW [Option ID = 16721]

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The VSWR of a coaxial line which has a reflection coefficient of 0.6e^-j<60°, is [Question ID = 4182]
1. 4 [Option ID = 16722]
2. 1 [Option ID = 16723]
3. 1.6 [Option ID = 16724]
4. 2 [Option ID = 16725]
Correct Answer :-
- 4 [Option ID = 16722]
When EM waves travel along a metallic waveguide in which there is a discontinuity due to some lossy material filled in a small length and the other end is terminated with a matched load. The discontinuity will cause [Question ID = 4183]
1. Progressive waves throughout the line. [Option ID = 16726]
2. Progressive waves on the generator side and standing waves on the matched load side. [Option ID = 16727]
3. Standing waves on the generator side and progressive waves on the matched load side. [Option ID = 16728]
4. Standing waves thoughout the line. [Option ID = 16729]
Correct Answer :-
- Standing waves on the generator side and progressive waves on the matched load side. [Option ID = 16728]
The power output of an input power of 10 mW in the following system, is
Pin = 10 mW
25 dB
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-35 dB
Pout [Question ID = 4184]
1. 5 dBm [Option ID = 16730]
2. 10 dB [Option ID = 16731]
3. 0 dBm [Option ID = 16732]
4. 10 dBm [Option ID = 16733]
Correct Answer :-
- 0 dBm [Option ID = 16732]
At microwave frequency, hybrid(H), admittance (Y) and impedance (Z) parameters can not be measured because, [Question ID = 4185]
1. Short and open circuit conditions are realizable over broad frequency range. [Option ID = 16734]
2. Short and open circuit conditions are unrealizable over broad frequency range. [Option ID = 16735]
3. Only short circuit condition is realizable over broad frequency range. [Option ID = 16736]
4. Only open circuit condition Is realizable over broad frequency range. [Option ID = 16737]
Correct Answer :-
- Short and open circuit conditions are unrealizable over broad frequency range. [Option ID = 16735]
Noise temperature (T) and gain(G) are two important parameters of satellite antenna. Out of the following, the antenna having largest G/T ratio is [Question ID = 4186]
1. Cassegrain antenna [Option ID = 16738]
2. Pyramidal antenna [Option ID = 16739]
3. Parabolic reflector [Option ID = 16740]
4. Dipole antenna [Option ID = 16741]
Correct Answer :-
- Parabolic reflector [Option ID = 16740]
A generator of 50 O internal impedance and operating frequency of 1 GHz feeds a 75 O load via a coaxial line of characteristics impedance 50 O. The reflection coefficient on the feed line is, [Question ID = 4187]
1. 0.2 [Option ID = 16742]
2. 0.67 [Option ID = 16743]
3. 1.5 [Option ID = 16744]
4. 1.05 [Option ID = 16745]
Correct Answer :-
- 0.2 [Option ID = 16742]

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A lossless transmission line is excited by a signal of voltage 5?0° V at 1.2 MHz. If the line is terminated by ZL (= Zo) at a distance 1km, the electrical length at the end point of the line is [Question ID = 4188]
1. 4p [Option ID = 16746]
2. 6p [Option ID = 16747]
3. 8p [Option ID = 16748]
4. 2p [Option ID = 16749]
Correct Answer :-
- 8p [Option ID = 16748]
The modulated microwave signal with 1 kHz square wave modulating signal is detected by [Question ID = 4189]
1. Tunable detector [Option ID = 16750]
2. VSWR meter [Option ID = 16751]
3. Spectrum analyzer [Option ID = 16752]
4. Slotted line [Option ID = 16753]
Correct Answer :-
- Tunable detector [Option ID = 16750]
A parabolic dish has a gain of 40 dB at 3GHz. The diameter of this dish is [Question ID = 4190]
1. 4.08 m [Option ID = 16754]
2. 8.02 m [Option ID = 16755]
3. 3.04 m [Option ID = 16756]
4. 1.25 m [Option ID = 16757]
Correct Answer :-
- 4.08 m [Option ID = 16754]
A satellite operates with 12 GHz at a distance of 36000 km has effective isotropic radiated power (EIRP) of 20 dBW.The flux density at receiving antenna of each station is [Question ID = 4191]
1. 2.21 × 10^-14 W/m² [Option ID = 16758]
2. 3.6 × 10^-14 W/m² [Option ID = 16759]
3. 0.614 × 10^-14 W/m² [Option ID = 16760]
4. 2.0 × 10^-14 W/m² [Option ID = 16761]
Correct Answer :-
- 0.614 × 10^-14 W/m² [Option ID = 16760]
A broadside array operating at 100cm wavelength consist of 4 half-wave dipoles spaced 50cm apart. Each element carries radio frequency current In the same phase and of magnitude 0.5 A. The radiated power will be [Question ID = 4192]
1. 34p² W [Option ID = 16762]
2. 16p² W [Option ID = 16763]
3. 20p² W [Option ID = 16764]
4. 50p² W [Option ID = 16765]
Correct Answer :-
- 20p² W [Option ID = 16764]

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Charge needed within a unit sphere centred at the origin for producing a potential field, V = - 6r⁵/e for the distance r = 1 meter, is [Question ID = 4193]
1. 30 p Coulomb [Option ID = 16766]
2. 240 p Coulomb [Option ID = 16767]
3. 120 p Coulomb [Option ID = 16768]
4. 180 p Coulomb [Option ID = 16769]
Correct Answer :-
- 120 p Coulomb [Option ID = 16768]
A material has conductivity of 10^-2 mho/m and a relative permittivity of 4. The frequency for which conduction current in the medium is equal to displacement current is [Question ID = 4194]
1. 90 MHz [Option ID = 16770]
2. 180 MHz [Option ID = 16771]
3. 27 MHz [Option ID = 16772]
4. 45 MHz [Option ID = 16773]
Correct Answer :-
- 45 MHz [Option ID = 16773]
For a electricity short dipole of length 80 cm operating at 30 MHz, the loss resistance (Rloss) is 1.5 O. Its radiation efficiency is [Question ID = 4195]
1. 92.4% [Option ID = 16774]
2. 94.9% [Option ID = 16775]
3. 102.5% [Option ID = 16776]
4. 86.7% [Option ID = 16777]
Correct Answer :-
- 94.9% [Option ID = 16775]
A Hertzien dipole of length ?/50 has an efficiency of 6.5%. The total quality factor for this dipole is [Question ID = 4196]
1. 1.1 [Option ID = 16778]
2. 0.20 [Option ID = 16779]
3. 3.7 [Option ID = 16780]
4. 5.5 [Option ID = 16781]
Correct Answer :-
- 0.20 [Option ID = 16779]
The value of integral ?₀^p sin³ a da is given by [Question ID = 4197]
1. 8/3 [Option ID = 16782]
2. 4/3 [Option ID = 16783]
3. 1/2 [Option ID = 16784]
4. 2/3 [Option ID = 16785]
Correct Answer :-
- 4/3 [Option ID = 16783]

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p/2
The region specified by {(?,f,z): 3 = ? = 5, p/6 = f = p/3 ,3 = z = 4.5} in cylindrical coordinates has volume of [Question ID = 4198]
1. 4.712 [Option ID = 16786]
2. 9.424 [Option ID = 16787]
3. 2.725 [Option ID = 16788]
4. 5.725 [Option ID = 16789]
Correct Answer :-
- 4.712 [Option ID = 16786]
dx
With the initial condition x(1) = 0.5 the solution of the differential equation, t dt + x = t is [Question ID = 4199]
1. x = t/2 [Option ID = 16790]
2. x = t - 1/2 [Option ID = 16791]
3. x = t² - 1/2 [Option ID = 16792]
4. x= t²/2 [Option ID = 16793]
Correct Answer :-
- x = t/2 [Option ID = 16790]
The Newton - Raphson method is used to solve the equation f(x) = x³ - 5x² + 6x - 8 = 0. Taking the initial guess as x = 5, the solution obtained at the end of the first iteration is [Question ID = 4200]
1. 2.2903 [Option ID = 16794]
2. 4.515 [Option ID = 16795]
3. 4.2903 [Option ID = 16796]
4. 2.515 [Option ID = 16797]
Correct Answer :-
- 4.2903 [Option ID = 16796]

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The inverse Laplace transform of the function
s+5
(s + 1)(s+3) is equal to [Question ID = 4201]
1. 2e^-t + e^-3t [Option ID = 16798]
2. e^-t + 2e^-3t [Option ID = 16799]
3. e^-t- 2e^-3t [Option ID = 16800]
4. 2e^-t-e^-3t [Option ID = 16801]
Correct Answer :-
- 2e^-t-e^-3t [Option ID = 16801]
A 4 GHz carrier is amplitude modulated by a low-pass message signal is to be ideally sampled. The minimum frequency of the sampling impulse train should be [Question ID = 4202]
1. 4 MHz [Option ID = 16802]
2. 8 GHz [Option ID = 16803]
3. 4 GHz [Option ID = 16804]
4. 8 MHz [Option ID = 16805]
Correct Answer :-
- 8 MHz [Option ID = 16805]
?1?
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A message signal given by mt = ?3? cos?1t amplitude-modulated with a carrier of frequency ?c to generate
s(t) = [1+m(t)]cos?ct. What is the power efficiency achieved by this modulation scheme? [Question ID = 4203]
1. 20% [Option ID = 16806]
2. 11.11% [Option ID = 16807]
3. 8.33% [Option ID = 16808]
4. 25% [Option ID = 16809]
Correct Answer :-
- 20% [Option ID = 16806]
The number of quantization levels with 8-bits required to reduce the quantization noise by a factor of 4 would be [Question ID = 4204]
1. 1024 [Option ID = 16810]
2. 64 [Option ID = 16811]
3. 256 [Option ID = 16812]
4. 512 [Option ID = 16813]
Correct Answer :-
- 512 [Option ID = 16813]
An ideal band - pass channel 500 Hz - 2000 Hz is deployed for communication. A modem is designed to transmit bits at the rate of 4800 bits/s using 16 - QAM. The roll off factor of a pulse with a raised cosine spectrum that utilizes the entire frequency band is [Question ID = 4205]
1. 0.20 [Option ID = 16814]
2. 0.25 [Option ID = 16815]
3. 0.30 [Option ID = 16816]
4. 0.15 [Option ID = 16817]
Correct Answer :-
- 0.25 [Option ID = 16815]
sin(pt)
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The Nyquist rate for the signal s(t) = ---------------- is given by
pt [Question ID = 4206]
1. 1200 Hz [Option ID = 16818]
2. 400 Hz [Option ID= 16819]
3. 600 Hz [Option ID = 16820]
4. 1400 Hz [Option ID = 16821]
Correct Answer :-
- 1200 Hz [Option ID = 16818]
The Vestigial Side Band (VSB) modulation is preferred in TV systems because It reduces the bandwidth requirement to half it avoids phase distortion at low frequency [Question ID = 4207]
1. 1 only [Option ID = 16822]
2. 2 only [Option ID = 16823]
3. Neither 1 nor 2 [Option ID = 16824]
4. Both 1 and 2 [Option ID = 16825]
Correct Answer :-
- Neither 1 nor 2 [Option ID = 16824]
A communication channel distributed by Gaussian noise has a bandwidth of 6 kHz and S/N ratio of 15. The maximum transmission rate that such a channel can support is [Question ID = 4208]
1. 48 kbits/s [Option ID = 16826]
2. 24 kbits/sec [Option ID = 16827]
3. 2.4 kbits/s [Option ID = 16828]
4. 32 kbits/s [Option ID = 16829]
Correct Answer :-
- 24 kbits/sec [Option ID = 16827]
In the given circuit, the value of Vx is
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5A
0.5 V
10 O
+
V 20 O
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8O
0.25 V [Question ID = 4209]
1. 12 V [Option ID = 16830]
2. 10 V [Option ID = 16831]
3. 0.8 V [Option ID = 16832]
4. 8 V [Option ID = 16833]
Correct Answer :-
- 8V [Option ID = 16833]
In the circuit shown, the current I flowing through the 50 O resistor will be zero if the value of Capacitor C (in µF) is
5? sin(5000t)
50 O
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I
1 mH
1 mH
1 mH
C [Question ID = 4210]
1. 15 µF [Option ID = 16834]
2. 20 µF [Option ID = 16835]
3. 10 µF [Option ID = 16836]
4. 22.5 µF [Option ID = 16837]
Correct Answer :-
- 20 µF [Option ID = 16835]

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In the circuit shown, the initial voltages across the capacitors C1 and C2 are 1V and 3V, respectively. The switch is closed at time t = 0. The total energy dissipated (in Joules) in the resistor R until steady state is reached, is
+
C1 = 3F
R = 10 O
+
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C2 = 1F [Question ID = 4211]
1. 1.5 J [Option ID = 16838]
2. 1.0 J [Option ID = 16839]
3. 0.5 J [Option ID = 16840]
4. 2 J [Option ID = 16841]
Correct Answer :-
- 1.5 J [Option ID = 16838]
The driving point impedance of the following network is given by Z(s) = 2+ ---------------------
Z(s)
L
C
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R
0.2s
+0.1s + 2 The component values are [Question ID = 4212]
1. L = 0.1 H, R = 0.5 O, C = 5 F [Option ID = 16842]
2. L = 5 H, R = 0.5 O, C = 0.1 F [Option ID = 16843]
3. L = 0.1 H, R = 2 O, C = 5 F [Option ID = 16844]
4. L = 5H, R = 2 O, C = 0.1 F [Option ID = 16845]
Correct Answer :-
- L = 0.1 H, R = 2 O, C = 5 F [Option ID = 16844]

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This download link is referred from the post: DUET Last 10 Years 2011-2021 Question Papers With Answer Key || Delhi University Entrance Test conducted by the NTA

This post was last modified on 27 December 2020

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