In microwave practice, a cavity resonator is best described as which of the following?

Introduction / Context:
Cavity resonators are foundational building blocks in microwave engineering, used for filters, oscillators, frequency meters, and high-Q references.

Given Data / Assumptions:

• Context: microwave resonators.
• Materials: good conductors for walls to achieve high Q.
• Fields: standing electromagnetic fields at discrete resonant frequencies.

Concept / Approach:

Metal-walled cavities trap electromagnetic energy by reflecting fields at the boundaries. Boundary conditions quantize field distributions, leading to discrete resonant modes with high quality factors when conductor and dielectric losses are low.

Step-by-Step Solution:

Verification / Alternative check:

Measured S-parameters reveal sharp resonant peaks with narrow bandwidth, characterizing high-Q metal cavities.

Why Other Options Are Wrong:

• Magnetic or purely dielectric walls alone: Not the standard high-Q microwave cavity construction.
• Either (b) or (c): Overgeneralization; typical cavities are metallic.
• Acoustic chamber: Not an RF/microwave device.

Common Pitfalls:

Confusing dielectric resonators (which do exist) with the definition of a metal cavity; mixing acoustic and electromagnetic resonance concepts.

Final Answer:

A hollow metallic enclosure that confines and resonates electromagnetic fields