What is the difference between a choke flange and a cover flange in waveguide connections?
Waveguide Flange Types
The waveguide flange interface must provide a continuous RF path across the junction between two waveguide sections. Any gap or resistance at the flange face creates a discontinuity that reflects power and generates leakage radiation. The two flange types address this requirement differently.
| Parameter | Standard Rect. | Ridged | Circular |
|---|---|---|---|
| Single-Mode BW | 40% (1.25-1.9 fc) | 50-150% | 26% (1.31:1 ratio) |
| Attenuation | Low | Moderate (3-5x) | Low to very low |
| Power Handling | High (kW-class) | Moderate | High |
| Polarization | Single | Single | Dual (TE11) |
| Cost | Low (commodity) | Medium | High (specialty) |
Frequently Asked Questions
When should I use a choke flange?
Use choke flanges for: field-assembled connections, connections that will be repeatedly assembled and disassembled, outdoor installations exposed to corrosion, applications requiring leak-free joints without gaskets, and any connection where surface flatness cannot be guaranteed to precision standards.
Can I mate two choke flanges together?
Choke-to-choke connections do not work as well as choke-to-cover because the choke groove design assumes a flat metal surface on the mating side. Two choke flanges facing each other create an unpredictable resonant structure in the groove region. Standard practice is always choke-to-cover.
Does the choke flange work across the full waveguide band?
The choke groove is optimized for the center of the waveguide band. Performance degrades slightly at the band edges because the groove depth is no longer exactly λg/4. Across a standard waveguide band (40% bandwidth), the choke flange typically maintains VSWR below 1.05:1, compared to 1.02:1 at the center frequency.