Coax & Waveguide Interfaces
How coaxial and rectangular waveguide transmission structures differ, and what matters when specifying a waveguide-to-coax transition.
Two different ways to carry RF energy
Coaxial transmission lines use inner and outer conductors and can support a TEM propagation mode over their intended operating range. Rectangular metallic waveguides guide electromagnetic modes with cutoff frequencies. Operating below the intended waveguide mode’s cutoff can prevent useful propagation.
Waveguide selection requires the correct size, band and mode. A part is not necessarily suitable merely because a connector or flange appears to fit.
What a waveguide-to-coax adapter does
An adapter transitions the RF field structure between a coaxial interface and a waveguide. Internal probes or other coupling structures are designed to achieve acceptable impedance matching and transmission performance across the specified band. Exact construction and ratings vary by product.
Specifications to verify
- Waveguide designation and supported frequency band
- Flange type and mechanical alignment
- Coax connector type, orientation and rated frequency
- Insertion loss and return loss or VSWR
- Average and peak RF power, environmental limits and mounting dimensions
Integration considerations
Document the physical orientation of the adapter relative to nearby hardware. Ensure that flange geometry and gasket or joint requirements match the waveguide assembly. For measurements, account for adapter loss and reference-plane changes.
See the waveguide-to-coax adapter guide or browse Impulse WG-to-coax adapters.
Discuss an RF component requirement
Share the frequency, performance, interfaces and quantity you need. Impulse can help evaluate relevant product options; confirm specific ratings against the manufacturer datasheet.
