In a circular waveguide, which of the following modes is the dominant mode of propagation?

Introduction / Context:
Waveguides support various modes depending on frequency and geometry. The dominant mode is the one with the lowest cutoff frequency that propagates first when frequency increases.

Given Data / Assumptions:

• Waveguide type: circular.
• Mode choices: TE and TM families.

Concept / Approach:

In rectangular waveguides, TE10 is dominant. In circular waveguides, the dominant mode is TE11, as it has the lowest cutoff frequency among supported modes.

Step-by-Step Solution:

Verification / Alternative check:

Standard microwave engineering reference confirms TE11 as dominant mode for circular waveguides.

Why Other Options Are Wrong:

• TE01, TE20, TE21: higher cutoff frequencies.
• TM01: not the dominant one.

Common Pitfalls:

Assuming TE01 or TM01 is dominant due to numbering; in circular waveguides, TE11 is the actual dominant mode.

Final Answer:

TE11