The operating principle of a backward-wave oscillator (BWO) is most similar to which microwave device?

Introduction / Context:
Backward-wave oscillators (BWOs) are microwave sources that generate oscillations by interaction of an electron beam with a slow-wave structure supporting backward-wave propagation (negative group velocity).

Given Data / Assumptions:

• Comparison is about the nature of oscillation and feedback mechanism.
• Reflex klystron is a one-cavity oscillator relying on electron bunching and feedback via transit-time.

Concept / Approach:
Like the reflex klystron, a BWO is an oscillator (not merely an amplifier) that uses an internal feedback mechanism tied to electron transit time and wave interaction. While a BWO uses a slow-wave structure (as in TWTs), its operation is as a self-excited oscillator akin to a reflex klystron rather than a linear amplifier.

Step-by-Step Solution:

Verification / Alternative check:
Microwave textbooks classify BWO as an oscillator often contrasted with reflex klystrons due to negative resistance / feedback mechanisms.

Why Other Options Are Wrong:

Common Pitfalls:

Final Answer: