MIcrowave Lab_C section_S1

An isolator in a microwave circuit is primarily used to:

• Amplify the signal

• Prevent signal reflection back to the source

• Split power equally

• Measure impedance

Answer explanation

An isolator in a microwave circuit is designed to prevent signal reflection back to the source, ensuring that signals flow in one direction and minimizing interference, which is crucial for maintaining signal integrity.

Which type of Tee junction allows power to flow in only one direction from the main waveguide?

• E Plane Tee

• H Plane Tee

• Magic Tee

• Rat race coupler

Answer explanation

The Magic Tee allows power to flow in only one direction from the main waveguide, making it unique among the options. In contrast, E Plane Tee and H Plane Tee allow bidirectional flow, while Rat race couplers are used for different applications.

Which of the following is a key advantage of a horn antenna?

• High power amplification

• Wide bandwidth and low VSWR

• Compact size

• Low cost

Answer explanation

A key advantage of a horn antenna is its wide bandwidth and low Voltage Standing Wave Ratio (VSWR), which allows for efficient signal transmission across a range of frequencies, making it ideal for various applications.

In microwave filters, what does a lowpass filter do?

• Blocks all frequencies

• Allows a specific range of frequencies to pass

• Attenuates low frequencies only

• Allows a low frequencies to pass

Answer explanation

A lowpass filter allows low frequencies to pass through while attenuating higher frequencies. This means it effectively permits signals below a certain cutoff frequency, making 'Allows a low frequencies to pass' the correct choice.

What does VSWR (Voltage Standing Wave Ratio) indicate in a microwave system?

• Power amplification

• Impedance mismatch

• Frequency stability

• Signal attenuation

Answer explanation

VSWR indicates the level of impedance mismatch in a microwave system. A high VSWR means that there is significant reflection of the signal due to this mismatch, which can lead to inefficiencies in power transfer.

What is the typical frequency range of X-band waveguides?

• 4000–8000 MHz

• 8000MHz - 12000 MHz

• 12–18 GHz

• 18–26 GHz

Answer explanation

The X-band typically ranges from 8,000 MHz to 12,000 MHz (or 8–12 GHz). This makes the correct choice 8000MHz - 12000 MHz, as it accurately reflects the standard frequency range for X-band waveguides.

Which of the following are characteristics of a reflex klystron?
(Select all that apply)

• It operates as an oscillator

• It has multiple resonant cavities

• It uses velocity modulation

• It is used for high-power amplification

Answer explanation

A reflex klystron operates as an oscillator and uses velocity modulation to generate microwave signals. It does not have multiple resonant cavities or is primarily used for high-power amplification.

Which of the following are properties of a microwave isolator?
(Select all that apply)

• Allows signal transmission in one direction

• Absorbs power in the reverse direction

• Increases signal gain

• Uses ferrite material

Answer explanation

A microwave isolator allows signal transmission in one direction, absorbs power in the reverse direction, and uses ferrite material to achieve these functions. It does not increase signal gain.

Which of the following are true about X-band waveguides?
(Select all that apply)

• They support TE10 as the dominant mode

• They are used in weather radar

• They have lower loss than coaxial cables at X-band frequencies

• They can propagate TEM mode

Answer explanation

X-band waveguides support TE10 as the dominant mode, are commonly used in weather radar, and have lower loss than coaxial cables at these frequencies. They cannot propagate TEM mode, which is why that option is incorrect.

The inner dimensions of an X-band WR-90 waveguide are approximately:

• 0.9 x 0.4 inches

• 1.0 x 0.5 inches

• 0.75 x 0.375 inches

• 1.122 x 0.497 inches

Answer explanation

The WR-90 waveguide has standard inner dimensions of approximately 0.9 x 0.4 inches, making this the correct choice. The other options do not match the typical specifications for this waveguide.