GATE 2002 ECE Question Paper

SECTION – A (75 marks)
1. This question consists of TWENTY-FIVE sub-questions (1.1 – 1.25) of ONE mark
each. For each of these sub-questions, four possible alternatives (A,B, C and D)
are given, out of which ONLY ONE is correct. Indicate the correct answer by
darkening the appropriate bubble against the question number on the left hand
side of the Objective Response Sheet (ORS). You may use the answer book
provided for any rough work, if needed

1.3 Convolution of x(t + 5) with impulse function δ(t – 7) is equal to
(a) x(t - 12) (b) x(t + 12) (c) x(t - 2) (d) x(t + 2)

1.4 Which of the following cannot be the Fourier series expansion of a periodic
signal?
(a) x(t) = 2cos t + 3 cos 3t (b) x(t) = 2cos πt + 7 cos t
(c) x(t) = cos t + 0.5 (d) x(t) = 2cos 1.5πt + sin 3.5 πt

1.6 In a negative feedback amplifier using voltage-series (i.e. voltage-sampling
series mixing) feedback. (Ri and Ro denote the input and output resistance
respectively)
(a) Ri decreases and Ro decreases (b) Ri decreases and Ro increases
(c) Ri increases and Ro decreases (d) Ri increases and Ro increases

1.7 A 741-type op-amp has a gain-bandwidth product of 1 MHz. A non-inverting
amplifier using this op-amp and having a voltage gain of 20 dB will exhibit a 3-dB
bandwidth of
(a) 50 KHz (b) 100 KHz (c)1000/17 KHz (d) 1000/7.07

1.9 4-bit 2’s complement representation of a decimal number is 1000. The number is
(a) +8 (b) 0 (c) -7 (d) -8

1.11 The number of comparators required in a 3-bit comparator type ADC is
(a) 2 (b) 3 (c) 7 (d) 8

1.18 A linear phase channel with phase delay TP and group delay Tg must have
(a) TP= Tg=constant (b) TP ∝f and Tg∝f
(c) TP = constant and Tg∝f (d) TP ∝f and Tg =constant

1.19. A 1 MHz sinusoidal carrier is amplitude modulated by a symmetrical square wave
of period 100µsec. Which of the following frequencies will NOT be present in the
modulated signal?
(a) 990 KHz (b) 1010 KHz (c) 1020 KHz (d) 1030 KHz

1.21. For a bit-rate of 8 Kbps, the best possible values of the transmitted frequencies
in a coherent binary FSK system are
(a) 16 KHz and 20 KHz (b) 20 KHz and 32 KHz
(c) 20 KHz and 40 KHz (d) 32 KHz and 40 KHz

1.22. The line-of-sight communication requires the transmit and receive antenna to
face each other. If the transmit antenna is vertically polarized, for best reception
the receive antenna should be
(a) horizontally polarized (b) vertically polarized
(c) at 45° with respect to horizontal polarization
(d) at 45° with respect to vertical polarization

1.23. The VSWR can have any value between
(a) 0 and 1 (b) -1 and +1 (c) 0 and ∞ (d) 1 and ∞
1.24. In an impedance Smith chart, a clockwise movement along a constant resistance
circle gives rise to
(a) a decrease in the value of reactance
(b) an increase in the value of reactance
(c) no change in the reactance value
(d) no change in the impedance value

1.25 The phase velocity for the TE10-mode in an air-filled rectangular waveguide is (c is the velocity of plane waves in free space)
(a) less than c (b) equal to c
(c) greater than c (d) none of the above

2. This question consists of TWENTY-FIVE sub-questions (2.1 – 2.25) of TWO marks
each. For each of these sub-questions, four possible alternatives (A,B, C and D)
are given, out of which ONLY ONE is correct. Indicate the correct answer by
darkening the appropriate bubble against the question number on the left hand
side of the Objective Response Sheet (ORS). You may use the answer book
provided for any rough work, if needed.

2.5. An amplifier using an opamp with a slew-rate SR = 1V/µsec has a gain of 40 dB.
If this amplifier has to faithfully amplify sinusoidal signals from dc to 20 KHz
without introducing any slew-rate induced distortion, then the input signal level
must not exceed.
(a) 795 mV (b) 395 mV (c) 79.5 mV (d) 39.5 mV

2.20. A signal x(t) = 100 cos(24π×103)t is ideally sampled with a sampling period of 50 µsec and then passed through an ideal low-pass filter with cutoff frequency of 15
KHz. Which of the following frequencies is/are present at the filter output?
(a) 12 KHz only (b) 8 KHz only
(c) 12 KHz and 9 KHz (d) 12 KHz and 8 KHz

2.25. A person with a receiver is 5 Km away from the transmitter. What is the distance that this person must move further to detect a 3-dB decrease in signal strength?
(a) 942 m (b) 2070 m (c) 4978 m (d) 5320 m

SECTION – B (75 Marks)
This section consists of TWENTY questions (EC3-EC22) of FIVE marks each. Attempt ANY
FIFTEEN questions. Answers must be given in the answer book provided. Answer for
each question must start on a fresh page and must appear at one place only. (Answers
to all parts of a question must appear together).

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