Microwave Engineering MCQ || Microwave Engineering Questions and Answers

Answer.4. 1, 2 and 3

Explanation

The various modes of operation of transferred electron device are classified on the basis of time in which various process occurs

τ_t: domain transit time

τ_d: dielectric relaxation time

τ_g: domain growth time

τ_o: the natural period of oscillation

Answer.2. Circulator

Explanation

Faraday Effect: Faraday effect Causes a rotation of the plane of polarization which is linearly proportional to the component of the magnetic field in the direction of propagation.

The angle of rotation = νBd

ν → material component

B → magnetic flux density in the propagation direction

D → path length

Thus Faraday rotation concept is used in both isolator and circulator, but it is most widely used in the circulator.

Answer.2. Higher

Explanation

Traveling wave tubes

• They are high gain, low noise, wideband microwave amplifiers.
• Amplification is done through the interaction between an electron beam and the Radio Frequency RF field.
• Electron beams exchange energy with RF Field over the full length of the tube.
• The necessary condition to ensure interaction between an electron beam and RF field is that both should travel in the same direction with the same velocity but the practical velocity of the electron beam is kept higher due to mutual repulsion between electron beams. Its working principle is based on Velocity Modulation (Bunching of the electron).

Answer.1. Transferred electron device

Explanation

Transferred electron device:-  A Gunn diode, also known as a transferred electron device (TED), is a form of diode, a two-terminal semiconductor electronic component, with negative resistance, used in high-frequency electronics. Its largest use is in electronic oscillators to generate microwaves.

Answer.1. To reduce axial velocity of RF field.

Explanation

Traveling wave tube:

1. A TWT is an electronic amplifier that is used to amplify radio frequency (RF) in the microwave range.
2.  It belongs to a category of linear beam tubes such as klystron.
3. In the case of TWT, the microwave circuit is non-resonant and the wave propagates at the same speed as the electron in the beam.

A helix in TWT plays an important role as a delay line, slowing down the RF signals traveling at a speed of light near the same speed along the tube as the electron beam.

Due to slow down the RF field interaction increase and the attenuator is placed along the RF circuit to prevent the reflected wave from traveling back to the cathode.

Answer.4. Higher Frequency Ranges

Explanation

Rain fade refers primarily to the absorption of a microwave radio frequency (RF) signal by atmospheric rain, snow, or ice, and losses which are especially affecting the frequencies above 11 GHz (Super High-frequency Range).

Answer.3. Traveling wave Tube

Explanation

• Microwave Communication uses a traveling wave tube amplifier to obtain a large gain over a wide bandwidth.
• The two types of microwave transmission are terrestrial and satellite:
• Terrestrial microwave transmissions are sent between two microwave stations on the earth (earth station). It is the most common form of long-distance communication.
• Satellite microwave transmissions involve sending microwave transmissions between two or more earth-based microwave stations and a satellite.

Answer.4. Reflex Klystron

Explanation

A Reflex Klystron is a specialized low-power vacuum tube used to produce oscillations at microwave frequency. Its principle of operation is velocity and current modulation. Klystrons are basically specialized tubes used as amplifiers and oscillators at the microwave frequency range.

Answer.4. UHF, SHF and EHF

Explanation

Microwave range: 300MHz to 300 GHz

UHF range: 300MHz to 3 GHz

SHF range: 3 GHz to 30 GHz

EHF range: 30 GHz to 300 GHz

Answer.1. High

Explanation