Ridge Waveguide vs. Rectangular Waveguide: Bandwidth, Size, and Loss Consider the statements: The usable bandwidth of a ridge waveguide is greater than that of a standard rectangular waveguide. For a given dominant-mode (TE10) cutoff frequency, a ridge waveguide requires a smaller cross-section than a standard rectangular guide. A ridge waveguide has higher conductor losses than a standard rectangular waveguide. Which statements are correct?

Introduction / Context:
Ridge waveguides insert one or more ridges into a rectangular guide to lower cutoff and extend bandwidth. The trade-offs include fabrication complexity and increased loss due to higher surface currents near the ridges.

Given Data / Assumptions:

• Comparison at the same target dominant-mode (TE10) cutoff frequency.
• Air-filled metallic guides with similar materials and finish.
• Focus on qualitative trends (bandwidth, physical size, conductor loss).

Concept / Approach:

Adding ridges increases the capacitance-like loading across the broad wall, lowering TE10 cutoff. For a given cutoff, the external dimensions can be reduced. The ridges also broaden the single-mode region, giving larger usable bandwidth. However, the narrowed field regions and enhanced surface currents around the ridge edges increase ohmic losses compared with a smooth rectangular guide.

Step-by-Step Solution:

Verification / Alternative check:

Design charts and measured Q values show ridge guides have lower unloaded Q (higher conductor loss) and wider operational band than standard guides.

Why Other Options Are Wrong:

Any option omitting one of the correct statements is incomplete; “All” would imply further claims beyond 1–3 that are not presented here.

Common Pitfalls:

Confusing lowered cutoff with lower attenuation at all frequencies; while cutoff is lower, conductor losses may increase.

Final Answer:

1, 2 and 3 only