Question 1

An apparatus whose theory of operation is based upon motion of electrons under the influence of combined E field and H field is known as a(n):&#10;A) TWT oscillator.&#10;B) Gunn oscillator.&#10;C) Magnetron oscillator.&#10;D) Klystron oscillator.

Accepted Answer

Magnetron oscillators operate based on the motion of electrons influenced by both electric (E) and magnetic (H) fields. This combined field interaction is essential for their operation, which is utilized in applications like radar systems and microwave ovens.

Question 2

The purpose of the low-loss dielectric material (radome) used to cover the dish is:&#10;A) for protection.&#10;B) for maintenance of internal pressure.&#10;C) to improve performance.&#10;D) A and B

Accepted Answer

The low-loss dielectric material (radome) is used to protect the dish and maintain internal pressure, ensuring the dish operates effectively in various environmental conditions.

Question 3

Parametric amplifiers that have pump frequencies that are double the signal frequency are operating in the:&#10;A) quantum mode&#10;B) nondegenerate mode.&#10;C) superconductive mode.&#10;D) degenerate mode.

Accepted Answer

Parametric amplifiers operating with pump frequencies that are double the signal frequency are said to be in the degenerate mode. This is because the signal and idler frequencies (in this case, the same as the signal frequency) are degenerate, meaning they are equal or very close to each other, which is a specific condition under which these amplifiers operate efficiently.

Question 4

Which of the following is not an application of a ferrite?&#10;A) isolator&#10;B) oscillator&#10;C) attenuator&#10;D) Faraday rotation

Accepted Answer

Ferrites are magnetic materials that are not typically used in oscillators. Oscillators generate and maintain a continuous wave of a specific frequency, and while ferrites are used in various RF and microwave applications due to their magnetic properties, they are not directly used to generate oscillations. Instead, ferrites are commonly used in isolators, attenuators, and for exploiting the Faraday rotation effect, among other applications.

Question 5

Which of the following is similar to an IMPATT diode?&#10;A) TRAPATT diode&#10;B) Baritt diode&#10;C) Gunn diode&#10;D) tunnel diode

Accepted Answer

Both IMPATT and TRAPATT diodes are used in microwave applications and operate based on the avalanche breakdown phenomenon.

Question 6

Degenerate mode parametric amplifiers operate with pump frequencies:&#10;A) two times the signal frequency.&#10;B) other than two times signal frequency.&#10;C) equal to zero.&#10;D) same as signal frequency.

Accepted Answer

Degenerate mode parametric amplifiers operate with pump frequencies that are exactly twice the signal frequency, which is a characteristic of their operation.

Question 7

Above 5 GHz, which device offers greater performance?&#10;A) silicon FETs&#10;B) GaAs FETs&#10;C) bipolars&#10;D) none of the above

Accepted Answer

GaAs FETs offer greater performance above 5 GHz due to their higher electron mobility compared to silicon-based devices, which allows for faster signal processing and higher frequencies of operation.

Question 8

Calculate the power gain of a microwave dish antenna with a 6 meter mouth diameter when used at 5 GHz.&#10;A) 47.8 dB&#10;B) 27.8 dB&#10;C) 55.6 dB&#10;D) 95.6 dB

Accepted Answer

The power gain $G$ of a microwave dish antenna can be calculated using the formula $G = (\pi d / \lambda)^2$, where $d$ is the diameter of the dish and $\lambda$ is the wavelength of the signal. The wavelength $\lambda$ can be found from the frequency $f$ using the relation $\lambda = c / f$, where $c$ is the speed of light ($3 \times 10^8$ m/s). For a frequency of 5 GHz ($5 \times 10^9$ Hz), $\lambda = 3 \times 10^8 / 5 \times 10^9 = 0.06$ meters. Substituting $d = 6$ meters and $\lambda = 0.06$ meters into the gain formula gives $G = (\pi \times 6 / 0.06)^2$. This results in a numerical gain, which when converted to decibels (dB) using $10 \log_{10}(G)$, gives approximately 47.8 dB.

Question 9

Which microwave oscillator is becoming obsolete due to its large size and the complex, costly sources of dc required for its operation?&#10;A) Klystron oscillator&#10;B) Gunn oscillator&#10;C) a traveling wave tube oscillator (TWT)&#10;D) Magnetron oscillator

Accepted Answer

Klystron oscillators are becoming obsolete because they are large in size and require complex and costly DC power sources for operation.

Question 10

Which of the following is also known as a backward-wave oscillator (BWO)?&#10;A) Klystron oscillator.&#10;B) Magnetron oscillator.&#10;C) TWT oscillator.&#10;D) Gunn oscillator.

Accepted Answer

The backward-wave oscillator (BWO) is also known as a traveling-wave tube (TWT) oscillator. It operates on the principle of electron beam interaction with a slow electromagnetic wave, making it distinct from other microwave oscillators.

Question 11

The model of a RF capacitor shows that the capacitor is:&#10;A) resistive&#10;B) inductive&#10;C) capacitive&#10;D) all of the above

Accepted Answer

The answer of The model of a RF capacitor shows...

Question 12

What material is most useful in the design of masers for low-noise microwave amplification?&#10;A) ruby&#10;B) manganese&#10;C) gallium arsendide&#10;D) ammonia

Accepted Answer

The answer of What material is most useful in the...

Question 13

Which of the following is not a vacuum tube?&#10;A) Gunn oscillator&#10;B) Klystron oscillator&#10;C) Magnetron oscillator&#10;D) traveling wave tube (TWT) oscillator&#10;E) all of the above

Accepted Answer

The answer of Which of the following is not a...

Question 14

A transphasor is:&#10;A) an optical switch.&#10;B) a fiber optic amplifier.&#10;C) a type of maser.&#10;D) all of the above.

Accepted Answer

The answer of A transphasor is:&#10;A) an optical switch.&#10;B) a...

Question 15

A microwave semiconductor that is typically used as T/R switches in RF transceivers operating above 100 MHz is the:&#10;A) Gunn diode.&#10;B) IMPATT diode.&#10;C) GaAs FET transistor.&#10;D) P-I-N diode.

Accepted Answer

The answer of A microwave semiconductor that is typically used...

Question 16

Which microwave oscillator is widely used in microwave ovens?&#10;A) Magnetron oscillator&#10;B) Gunn oscillator&#10;C) a traveling wave tube oscillator (TWT)&#10;D) Klystron oscillator

Accepted Answer

The answer of Which microwave oscillator is widely used in...

Question 17

Why are microwave antennas characterized by high gain and high directivity?&#10;A) because there is no need for omnidirectional antennas since all microwave links are point-to-point&#10;B) microwave transmitters are very limited in their output power&#10;C) since device noise is greater at these frequencies, receivers require larger input signals.&#10;D) because of the short wavelengths involved, the physical sizes required are enough for designs not practical at lower frequencies.&#10;E) all of the above

Accepted Answer

The answer of Why are microwave antennas characterized by high...

Question 18

Special ferrites that are typically used as RF chokes are called:&#10;A) isolators.&#10;B) beads.&#10;C) yigs.&#10;D) circulators.

Accepted Answer

The answer of Special ferrites that are typically used as...

Deck 16: Microwaves and Lasers