Rectangular waveguide – Effect of increasing internal air pressure on maximum power handling If the air pressure inside a rectangular waveguide is increased (with all other factors unchanged), how does its maximum RF power-handling capacity change?

Introduction:
Waveguide power handling is limited by RF breakdown of the gas (usually air) at the wall/field maxima. The breakdown threshold depends on pressure and gap according to gas discharge physics (Paschen-like behavior). Pressurizing waveguides (or using SF6) is a standard technique to extend power capacity.

Given Data / Assumptions:

• Same geometry, frequency, and surface finish.
• Gas is air; only internal pressure is increased within safe mechanical limits.
• No condensation or contamination introduced.

Concept / Approach:

Increasing pressure raises the breakdown electric field strength, delaying ionization and arcing. Since maximum power for a given guide mode scales with allowable peak field before breakdown, higher breakdown field translates directly to higher permissible power.

Step-by-Step Solution:

Verification / Alternative check:

High-power radar and broadcast systems routinely use pressurized guides to achieve higher P_max and reduce multipaction/rf arcing.

Why Other Options Are Wrong:

Option A/C contradict observed practice; Option D is too vague; Option E is incorrect because breakdown field is not constant—it varies with pressure and gap.

Common Pitfalls:

Ignoring moisture/contaminants that can lower breakdown in practice; assuming metal loss, not breakdown, always limits power (often breakdown is the primary constraint).

Final Answer:

is increased.