GATE (Graduate Aptitude Test in Engineering) Electronics: Questions 594 - 598 of 1076

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Question 594

Appeared in Year: 2014 (UGC-NET)

Question

MCQ▾

The threshold voltage of a MOSFET can be lowered by (June)

1. Using a thinner gate oxide

2. Reducing the carrier concentration in the substrate

3. Increasing the carrier concentration in the substrate

Of these statements:

Choices

Choice (4)Response

a.

1 and 2 are correct

b.

2 alone is correct

c.

3 alone is correct.

d.

1 and 3 are correct

Question 595

Appeared in Year: 2013 (UGC-NET)

Question

MCQ▾

A semiconductor has ________ temperature co-efficient of resistance (September)

Choices

Choice (4)Response

a.

Positive

b.

One

c.

Negative

d.

Zero

Passage

Read the passage and answer the following five questions:

An antenna is generally a metallic object, often a wire or collection of wires, used to convert high frequency current into electromagnetic waves and vice-versa. Antenna serve either or both of the following two functions, generation or the collection of electromagnetic energy. In a transmitting system, a radio-frequency signal is developed, amplified, modulated and applied to the antenna. The R-F currents flowing through the antenna produce electromagnetic waves which radiate into the atmosphere. In a receiving system, electromagnetic waves “cutting” through the antenna induce alternating currents for use by the receiver.

Efficient operation also requires that the receiving antenna be of the same polarization as the transmitting antenna. Polarization is the direction of the electric field and is therefore, the same as the antennas physical configuration. Thus vertical antenna will transmit vertical polarized light, any antenna having a physical length that is one-half wavelength of the applied frequency is called a Hertz antenna. Hertz antenna are predominantly used with frequencies above 2MHz. usually, at frequencies below 2 MHz, a Marconi type of antenna is used. The Marconi antenna is usually a quarter-wave grounded antenna or any odd multiple of a quarter wavelength.

The Yagi-Uda antenna consists of a driver՚s element and two or more parasitic elements. Yagi-Uda has two parasitic elements, a reflector and a director. This Yagi-Uda antenna provides about 7 dB of power gain with respect to a half wavelength dipole reference. More complex antennas may be circularly polarized both vertically and horizontally polarized waves are radiated with equal power in both. If the powers are unequal the antenna is said to be elliptically polarized.

A horn is an ideal antenna for terminating a waveguide and may be conical, rectangular or sectorial. Wide band antennas either when the transmissions are wide band or when working of narrow channels over a wide frequency range is the major application. Helical antenna, which consists of a loosely wound helix backed up by a metal ground plane. Loop antennas are often used for direction finding. Loops have many shapes and generally consists of a single turn of wire. Disc one is a ground plane antenna evolved from the vertical dipole and having a very similar radiation pattern.

Question 596 (1 of 5 Based on Passage)

Appeared in Year: 2014 (UGC-NET)

Question

MCQ▾

Which of the following antennas is best exerted from a waveguide? (June)

Choices

Choice (4)Response

a.

Biconical

b.

Folded dipole

c.

Disc one

d.

Horn

Question 597 (2 of 5 Based on Passage)

Appeared in Year: 2014 (UGC-NET)

Question

MCQ▾

A helical antenna is used for satellite tracking because of its (June)

Choices

Choice (4)Response

a.

Good front-to-back ratio

b.

Broad band width

c.

Elliptical polarization

d.

Circular polarization

Question 598 (3 of 5 Based on Passage)

Appeared in Year: 2014 (UGC-NET)

Question

MCQ▾

The disc one antenna is (June)

Choices

Choice (4)Response

a.

Useful as a UHF receiving antenna

b.

Used as a radar receiving antenna

c.

Circularly polarized like other circular antennas

d.

A useful direction finding antenna

Developed by: