Waveguide Coupler
Understanding Waveguide Couplers
Waveguide couplers are essential for power monitoring, signal sampling, and power dividing in waveguide-based systems. Their enclosed metallic structure provides superior directivity and isolation compared to planar couplers.
Waveguide Coupler Types
- Bethe hole: Single coupling aperture. Simple. Narrowband directivity. Coupling determined by hole size.
- Multi-hole (Riblet): Array of holes designed for flat coupling and high directivity over wide bandwidth. The gold standard for broadband waveguide couplers.
- Cross-guide: Two waveguides crossing at right angles with coupling apertures. Compact. Wideband.
- Short-slot hybrid: 3 dB coupler for balanced configurations. Two waveguides sharing a slot in common wall.
Frequently Asked Questions
What is a waveguide coupler?
A waveguide coupler samples a fraction of the signal through coupling apertures between waveguides. Types include Bethe hole (simple), multi-hole (broadband), cross-guide (compact), and short-slot hybrid (3 dB split). Superior directivity vs planar couplers.
What directivity can waveguide couplers achieve?
Multi-hole waveguide couplers achieve > 35-40 dB directivity over full waveguide bandwidth. This is significantly better than microstrip couplers (20-25 dB). High directivity is critical for accurate power monitoring.
When should I use waveguide vs coaxial couplers?
Use waveguide couplers when the system is already in waveguide, at high frequencies (> 18 GHz), for high power, or when maximum directivity is needed. Coaxial couplers are more compact and convenient for system integration below 18 GHz.