Waveguide-to-coaxial adapters are RF adapters used to connect waveguide devices to coaxial components.

What are Coaxial Cables and Waveguides?

Coaxial cables are electrical cables with three or more layers: a conductor material within an insulating layer within a tubular shield. The term coaxial comes from the fact that the two protective layers share the same geometric axis. It is used as a transmission line for radio frequency signals.

Waveguides are structures which guide and direct different types of waves. In the case of electromagnetic waves, waveguides guide their propagation at microwave frequencies and are usually cylindrical or rectangular hollow metal tubes. A waveguide component of a particular dimension is used to propagate electromagnetic waves of a particular frequency. Some waveguides are also used in integrated circuits.

Adapter Composition

Waveguide-to-coaxial adapters are composed of a waveguide component that fits the waveguide tubing and ends with a flange, and a coaxial probe assembly with a coaxial adapter and connection hardware. The coaxial cable adapter is typically tapped through one wall of the waveguide adapter housing. On the bottom of the waveguide housing are a set of tuning screws that are used to adjust the waveguide band coverage while minimizing the voltage standing wave ratio. Some waveguide-to coaxial adapters come without the tuning screws and are factory-tuned to a specific bandwidth configuration.

Classifying Waveguide-to-Coaxial Adapters

Waveguide-to-coaxial RF adapters can be classified based on connector type, flange material, flange type, and flange profile.

  • Connector types come in a large array of different connector types and brands which vary based on size, specifications, and individual product features. The GlobalSpec SpecSearch Database contains listings and information on many of these types.
  • Flange materials include various conductive metals such as silver, copper, brass, bronze, and aluminum.
  • Flange types include a various number of different styles of external or internal ridges.
  • Flange profiles include rectangular, square, or circular shapes based on the application and system design.

Product Specifications

Product specifications to consider when selecting waveguide-to-coaxial adapters include frequency range, maximum input power, voltage standing wave ratio (VSWR), and return loss. The return loss of an adapter is a measurement of the match between the impedance of the adapter and the system impedance. VSWR is a measure of the amount of RF power reflected back to the signal source because of impedance mismatches.  Frequency range and maximum input power are all dependent on the system design for which the adapter is being used.

Applications

Waveguide-to-coaxial adapters are frequently used to provide transmission between microwave devices and a coaxial component such as an attenuator, switch, or coupler. They are commonly used in satellite and terrestrial communications equipment. Adapters are typically constructed of copper alloys, but may also come with stainless steel metallic parts for long life and durability.