What is the relationship between waveguide dimensions and operating frequency band?
Waveguide Sizing
The WR designation system simplifies waveguide identification. WR-XX means the broad wall dimension a = XX hundredths of an inch. WR-90 has a = 0.900 inches (22.86 mm). The complete set of standard waveguide sizes covers frequencies from 320 MHz (WR-2300) to 325 GHz (WR-3). Each size provides approximately 40% bandwidth within the single-mode operating range.
| 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) |
- Performance verification: confirm specifications against the application requirements before finalizing the design
- Environmental factors: temperature range, humidity, and vibration affect long-term reliability and parameter drift
- Cost vs. performance: evaluate whether the application demands premium components or standard commercial grades
Frequently Asked Questions
What waveguide do I need for my frequency?
Select the standard waveguide whose operating band includes your frequency. For 10 GHz: WR-90 (8.2-12.4 GHz). For 24 GHz: WR-42 (18-26.5 GHz). For 77 GHz: WR-12 (60-90 GHz) or WR-10 (75-110 GHz). For frequencies at the edge of a band, choose the band that places your frequency near the center for best performance.
Can I use non-standard dimensions?
Yes, but you lose compatibility with standard flanges et components. Non-standard waveguide is used for specific applications: oversized waveguide for reduced loss (at the cost of multi-mode risk), reduced-width for higher cutoff, or double-ridged for extended bandwidth.
What is the IEC waveguide designation?
IEC uses R-designation (R-XX) corresponding to WR sizes. R-100 = WR-90, R-220 = WR-42. The R number is the cutoff frequency of the TE10 mode in hundreds of MHz. Some regions also use EIA or IEC band designations (Ku, K, Ka, V, W, D, G bands).