Classification and Selection Guide for Waveguide Flanges

Waveguide flanges are essential mechanical and RF components used to connect waveguide sections or interface waveguides with devices such as antennas, modules, or coaxial transitions. In high-frequency systems—microwave and millimeter-wave applications in particular—the proper selection of flanges ensures reliable transmission, alignment accuracy, and long-term stability. This guide outlines the common types of waveguide flanges and key considerations for selection.

1. Classification by Standard System

A. UG Flanges (United States Government)

• Based on the US military standard MIL-DTL-3922

• Common in aerospace, defense, and industrial systems

• Typical models: UG-387/U, UG-599/U, etc.

• Features: standardized bolt patterns and alignment pin holes

B. UBR / PDR Flanges (Precision Series)

• Used for high-precision applications, including double-ridge waveguides

• Frequently adopted in lab testing, calibration setups, and high-performance systems

• Highly accurate alignment, suitable for repeated mating

C. FBP Flanges (IEC Standard)

• Defined by IEC 60154 standard

• Widely used in Europe and for high-frequency testing

• Models include FBP12, FBP28, FBP90, etc.

• Excellent mechanical accuracy and repeatability

D. EIA Standard Flanges

• Used with larger waveguides (e.g., WR90, WR430) in radar, broadcasting, and satellite systems

• Robust construction for high-power handling

• Features reinforced bolt holes and larger flange sizes

2. Classification by Mechanical Features

A. Flanges with Alignment Pins

• Built-in holes for dowel pins ensure precise positioning

• Ideal for lab setups or field-replaceable modules

• Default in UG and some UBR designs

B. Weldable Flanges

• Designed for direct welding to waveguide tubes

• Applied in vacuum chambers, sealed packages, or compact systems

• Often made from stainless steel or other high-integrity metals

C. Hermetic Flanges

• Used in vacuum or gas-sealed systems

• Designed to meet leak-rate requirements for aerospace or lab environments

• Compatible with vacuum brazing or glass-to-metal sealing

3. Classification by WR Size Compatibility

Each WR (Waveguide Rectangular) size corresponds to a specific set of flange models. Below is a common reference:

🔧 Note: While naming conventions may vary slightly across manufacturers, critical dimensions—bolt hole patterns, guide pin locations, and aperture sizes—must match exactly.

4. Key Selection Considerations

1. WR Size – Always confirm the waveguide standard and size (e.g., WR12, WR15)

2. Flange Standard – Choose based on regional compatibility and system requirements (UG, FBP, UBR)

3. Mechanical Needs – Does it require alignment pins? Is welding needed? Are space constraints present?

4. Environmental Requirements – For outdoor, corrosive, or high-temp conditions, consider gold plating or stainless steel options

5. Application Examples

6. Conclusion

Though small in size, waveguide flanges play a critical role in ensuring RF integrity, mechanical alignment, and system reliability. A proper understanding of flange standards and features enables engineers to build high-performance, low-loss waveguide systems with optimal longevity and serviceability.

If you need further assistance with selecting the appropriate waveguide flange for your design, feel free to contact our engineering support team for customized recommendations.