www.pacific-university.ac.in PhD ECE Model Question Paper : Pacific University

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Name of the organisation : Pacific University (pacific-university.ac.in)
Description : Model Question Paper

Index Page : http://pacific-university.ac.in/Cont...earch_and_P.hd
Model Question Paper : http://pacific-university.ac.in/User...ngineering.pdf

Sample Paper
PhD Section B Electronics & Communication Engineering
Max. Marks 100
Instructions for Candidates:
Attempt all 50 questions, each question carries 02 marks. There is no negative marking. Please mark the correct answer as A/B/C/D at appropriate place, on the right hand side of the question, in blue or black ink.

Q. 1 The very high frequency (VHF) range extends from
(A) 3-30MHz (B) 30-300MHz
(C) 300-3000MHz (D) 3000-30000MHz

Q.2 The function of the transducer in a communication system is
(A) To transmit the massage signal
(B) To modulate the massage signal
(C) To convert massage sound signal into electrical signal
(D) None

Q.3 If G (f) represents the Fourier transform of a signal g (t) which is real and old symmetric in time, then
(A) G (f) is complex (B) G (f) is imaginary
(C) G (f) is real (D) G (f) is real and non negative

Q.4 The trigonometric Fourier series of an even function of time does not have the
(A) dc term (B) cosine terms
(C) sin terms (D) odd harmonic terms

Q.5 The power spectral density (psd) of a deterministic signal is given by [()/2] , where f is frequency. The auto correlation function of this signal in the time domain is
(A) A rectangular pulse (B) A delta function
(C) Sine pulse (D) Triangular pulse

Q.6 A 4GHz carrier is DSB-SC modulated by a low pass message signal with maximum frequency of 2MHz. The resultant signal is to be ideally sampled. The minimum frequency of the sampling in train should be
(A) 4MHz (B) 8MHz
(C) 8GHz (D) 8.004GHz

Q.7 The maximum power efficiency of AM modulator is
(A) 25% (B) 50%
(C) 75% (D) 100%

Q.8 1 MHz sinusoidal carrier is amplitude modulated by symmetrical square wave of period 100per sec. which of the following frequency will not be present in the modulated signal?
(A) 990KHz (B) 1010KHz
(C) 1020KHz (D) 1030KHz

Q.9 The probability density function of the envelope of narrowband Gaussian noise is
(A) Poisson (B) Gaussian
(C) Rayleigh (D) Rician

Q.10 The amplitude spectrum of a Gaussian pulse is
(A) Uniform (B) A sine function
(C) Gaussian (D) An impulse function

Q.11 The space charge limited current in a in a thermionic diode is given by
(A) Richardson’s equation (B) Child-Langmuir equation
(C) Plank constant (D) none

Q.12 Schottky effect originates from
(A) Field emission (B) Photo electric emission
(C) Secondary emission (D) none

Q.13 A good ohmic contacts is obtained with
(A) A wide band gap semiconductor (B) A low barrier height
(C) Low doping (D) None

Q.14 The reverse saturation current desity of a schottky diode is
(A) Much larger than that of a pn junction diode
(B) Much less than that of a pn junction diode
(C) Equal to that of a pn junction diode
(D) None

Q.15 The cutin voltage of a si p-n diode is about
(A) 0.6v (B) 0.6mv
(C) 6v (D) None