Rectangular waveguide usage: Which mode is most commonly used for electromagnetic transmission in standard rectangular waveguides?

Introduction:
Practical rectangular waveguide systems are designed around a single propagating mode over the operating band. Identifying the commonly used mode clarifies why waveguide dimensions are standardized and how bandwidth is chosen.

Given Data / Assumptions:

• Air-filled rectangular waveguide with width a and height b (a > b).
• Desire for single-mode operation to avoid dispersion and mode conversion.
• Standard WR-series waveguides (e.g., WR-90) follow these principles.

Concept / Approach:

The TE10 mode is the dominant (lowest-cutoff) mode in a rectangular waveguide. Waveguide bands are selected so that TE10 propagates well above cutoff while the next higher-order mode remains below cutoff across the band, ensuring single-mode transmission.

Step-by-Step Solution:

Verification / Alternative check:

Waveguide charts and industry catalogues list components specified for TE10 operation; measured patterns and field probes confirm TE10 dominance in common setups.

Why Other Options Are Wrong:

• TE01, TE20, TE11, TM10 either have higher cutoff or are not standard in rectangular guides for mainline transmission.

Common Pitfalls:

Confusing TE11 (dominant in circular waveguides) with rectangular-guide dominance.

Final Answer:

TE10 mode