Question 1

The frequency of oscillation in Gunn diode is given by:

Accepted Answer

The frequency of oscillation in a Gunn diode is given by the formula $f = \frac{v_{dom}}{l_{eff}}$, where $v_{dom}$ is the domain velocity and $l_{eff}$ is the effective length of the device. This corresponds to option A.

Question 2

In Gunn diode oscillator, the Gunn diode is inserted into a waveguide cavity formed by a short circuit termination at one end

Accepted Answer

The Gunn diode oscillator operates by inserting the Gunn diode into a waveguide or resonant cavity, which often includes a short circuit termination at one end to reflect the electromagnetic waves and create the necessary conditions for oscillation.

Question 3

In a Gunn diode oscillator, the electron drift velocity was found to be 107 cm/second and the effective length is 20 microns, then the intrinsic frequency is:

Accepted Answer

The intrinsic frequency of a Gunn diode oscillator is given by the formula f = v / (2 * L), where v is the electron drift velocity and L is the effective length. Substituting the given values, f = 107 cm/s / (2 * 20 * 10^-4 cm) = 5 GHz.

Question 4

The material used to fabricate IMPATT diodes is GaAs since they have the highest efficiency in all aspects.

Accepted Answer

While GaAs is one of the materials used for IMPATT diodes, Silicon is also commonly used, and the highest efficiency depends on the specific application and frequency of operation, not just the material.

Question 5

3 IMPATT DIODES, SCHOTTKY BARRIER DIODES, PIN DIODES

Accepted Answer

IMPATT diodes operate based on avalanche multiplication, where an avalanche breakdown occurs due to the high electric field, leading to a multiplication of charge carriers.

Question 6

To prevent an IMPATT diode from burning, a constant bias source is used to maintain __________  at safe limit.

Accepted Answer

A constant bias source is used to maintain the average current at a safe limit to prevent the IMPATT diode from overheating and burning out.

Question 7

The number of semiconductor layers in IMPATT diode is:

Accepted Answer

The answer of The number of semiconductor layers in IMPATT...

Question 8

The resonant frequency of an IMPATT diode is given by:

Accepted Answer

The resonant frequency of an IMPATT diode is given by $f = \frac{v_d}{2L}$, where $v_d$ is the drift velocity of the charge carriers and $L$ is the length of the drift region.

Question 9

If the length of the intrinsic region in IMPATT diode is 2 µm and the carrier drift velocity are 107 cm/s, then the nominal frequency of the diode is:

Accepted Answer

The nominal frequency (f) of an IMPATT diode can be calculated using the formula f = v / (2 * L), where v is the carrier drift velocity and L is the length of the intrinsic region. Given v = 10^7 cm/s (or 10^8 m/s) and L = 2 µm (or 2 * 10^-6 m), f = 10^8 / (2 * 2 * 10^-6) = 25 GHz.

Question 10

IMPATT diodes employ impact ionization technique which is a noisy mechanism of generating charge carriers.

Accepted Answer

IMPATT diodes indeed use the impact ionization technique to generate charge carriers, which is inherently a noisy process due to the stochastic nature of the ionization events.

Question 11

An essential requirement for the BARITT diode is that the intermediate drift region be completely filled to cause the punch through to occur.

Accepted Answer

The answer of An essential requirement for the BARITT diode...

Question 12

If the RMS peak current in an IMPATT diode is 700 mA and if DC input power is 6 watt, with the load resistance being equal to

Accepted Answer

The answer of If the RMS peak current in an...

Question 13

If the critical field in a Gunn diode oscillator is 3.2 KV/cm and effective length is 20 microns, then the critical voltage is:

Accepted Answer

The critical voltage (Vc) in a Gunn diode oscillator can be calculated using the formula Vc = E * L, where E is the critical field and L is the effective length. Given E = 3.2 KV/cm (or 3200 V/cm) and L = 20 microns (or 20 x 10^-4 cm), Vc = 3200 V/cm * 20 x 10^-4 cm = 6.4 V.

Question 14

The production of power at higher frequencies is much simpler than production of power at low frequencies.

Accepted Answer

Producing power at higher frequencies involves more complex and expensive equipment and processes due to issues like increased energy losses and the need for more precise control mechanisms. Low-frequency power generation, such as 50 or 60 Hz used in most power systems, is simpler and more efficient for large-scale distribution.

Question 15

Microwave tubes are power sources themselves at higher frequencies and can be used independently without any other devices.

Accepted Answer

Microwave tubes, such as klystrons and magnetrons, are indeed used to generate and amplify high-frequency signals, but they require external power sources to operate. They are not power sources themselves.

Question 16

The klystron tube used in a klystron amplifier is a __________type beam amplifier.

Accepted Answer

Klystron tubes are a type of linear beam amplifier, where the electron beam travels in a straight line from the cathode to the collector, interacting with RF fields in cavities along the way to amplify a signal.

Question 17

In crossed field tubes, the electron beam traverses the length of the tube and is parallel to the electric field.

Accepted Answer

In crossed field tubes, the electron beam is perpendicular to both the electric and magnetic fields, not parallel to the electric field.

Question 18

__________    is a single cavity klystron tube that operates as on oscillator by using a reflector electrode after the cavity.

Accepted Answer

The reflex klystron is a type of klystron tube that operates as an oscillator by using a single cavity along with a reflector electrode, which helps in reflecting the electron beam back through the cavity to achieve oscillation.

Question 19

A major disadvantage of klystron amplifier is:

Accepted Answer

Klystron amplifiers are known for their high power gain but have a relatively low bandwidth, which limits their frequency agility and the range of frequencies they can amplify effectively.

Question 20

In a __________oscillator, the RF wave travels along the helix from the collector towards the electron gun.

Accepted Answer

In a backward wave oscillator, the RF wave indeed travels along the helix from the collector towards the electron gun, distinguishing it from other types of oscillators where the wave might travel in the opposite direction.

Quiz 5: Microwave Devices and Their Operation: Gunn Diodes, Impatt Diodes, Klystron Tubes