Electronics & Communication Gate Yearwise 

Electronics and Communication Gate 2017 Set-1 Questions with Answer

Ques 14 GATE 2017 SET-1

In a digital communication system, the overall pulse shape p(t) at the receiver before the sampler has the Fourier transform P(f). If the symbols are transmitted at the rate of 2000 symbols per second. for which of the following cases is the inter symbol interference zero?

A

B

C

D


(b) is the correct answer.

Ques 15 GATE 2017 SET-1

Consider a wireless communication link between a transmitter and a receiver located in free space, with finite and strictly positive capacity. If the effective areas of the transmitter and the receiver antennas, and the distance between them are all doubled, and everything else remains unchanged, the maximum capacity of the wireless link

A

increases by a factor of 2

B

decreases by a factor of 2

C

remains unchanged

D

decreases by a factor of √2


(c) is the correct answer.

Ques 16 GATE 2017 SET-1

An optical fiber is kept along the z direction. The refractive indices for the electric fields along x and y directions in the fiber are nx=1.5000 and ny=1.5001 respectively (nx≠ny due to the imperfection in the fiber cross-section). The free space wavelength of a light wave propagating in the fiber is 1.5μm If the lightwave is circularly polarized at the input of the fiber, the minimum propagation distance after which it becomes linearly polarized. in centimetres, is


(0.375) is the correct answer.

Ques 17 GATE 2017 SET-1

The expression for an electric field in free space is E=E0(δx+δy+j2δz)e-j(ωt-kx+ky), where x, y, z represent the spatial coordinates, t represents time, and ω, k are constants. This electric field

A

does not represent a plane wave.

B

represents a circularly polarized plane wave propagating normal to the z-axis.

C

represents an elliptically polarized plane wave propagating along the x-y plane.

D

represents a linearly polarized plane wave.


(c) is the correct answer.

Ques 18 GATE 2017 SET-1

A half wavelength dipole is kept in the x-y plane and oriented along 45° from the x-axis. Determine the direction of null in the radiation pattern for 0≤φ≤π Here the angle θ (0≤θ≤π) is measured from the z-axis, and the angle φ (0≤φ≤2π) is measured from the x-axis in the x-y plane.

A

θ=90°, φ=45°

B

θ=45°, φ=90°

C

θ=90°, φ=135°

D

θ=45°, φ=135°


(a) is the correct answer.

Ques 19 GATE 2017 SET-1

The voltage of an electromagnetic wave propagating in a coaxial cable with uniform characteristic impedance is V(l)=e-γl+jωt Volts, where l is the distance along the length of the cable in metres, γ=(0.1+j40)m-1 is the complex propagation constant, and ω=2π×109rad/s is the angular frequency. The absolute value of the attenuation in the cable in dB/metre is


(0.8686) is the correct answer.

Ques 20 GATE 2017 SET-1

For the operational amplifier circuit shown, the output saturation voltages are ± 15 V.

The upper and lower threshold voltages for the circuit are, respectively,

A

+5 V and -5 V

B

+7 V and -3 V

C

+3 V and -7 V

D

+3 V and -3 V


(b) is the correct answer.

Ques 21 GATE 2017 SET-1

A good transconductance amplifier should have

A

high input resistance and low output resistance

B

low input resistance and high output resistance

C

high input and output resistances

D

low input and output resistances


(c) is the correct answer.

Ques 22 GATE 2017 SET-1

The Miller effect in the context of a Common Emitter amplifier explains

A

an increase in the low-frequency cutoff frequency

B

an increase in the high-frequency cutoff frequency

C

a decrease in the low-frequency cutoff frequency

D

a decrease in the high-frequency cutoff frequency


(d) is the correct answer.

Ques 23 GATE 2017 SET-1

In the figure shown, the npn transistor acts as a switch. For the input Vin(t) as shown in the figure, the transistor switches between the cut-off and saturation regions of operation, when T is large.

Assume collector-to-emitter voltage at saturation VCE(sat)=0.2V and base-to-emitter voltage VBE=0.7V The minimum value of the common-base current gain (α) of the transistor for the switching should be


(0.9) is the correct answer.

Ques 24 GATE 2017 SET-1

For the circuit shown, assume that the NMOS transistor is in saturation. Its threshold voltage Vtn=1 V and its transconductance parameter μnCox(W/L)=1 mA/V2.

Neglect channel length modulation and body bias effects. Under these conditions, the drain current ID in mA is


(2) is the correct answer.

Ques 25 GATE 2017 SET-1

For the DC analysis of the Common-Emitter amplifier shown, neglect the base current and assume that the emitter and collector currents are equal. Given that VT=25 mV, VBE=0.7 V, and the BJT output resistance r0 is practically infinite. Under these conditions, the midband voltage gain magnitude, Av=|vo/vi| V/V, is


(128) is the correct answer.

Ques 26 GATE 2017 SET-1

The amplifier circuit shown in the figure is implemented using a compensated operational amplifier (op-amp), and has an open-loop voltage gain. A0=105V/V and an open-loop cut-off frequency, fc=8 Hz The voltage gain of the amplifier at 15 kHz. in V/V, is


(44.3) is the correct answer.

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