Directional Coupler Specifications

Directional couplers are designed for various applications, and are typically available in flat-pack, plug-in, connected, and surface mount packages. All units are specifically designed and constructed to meet stringent environmental requirements and are made to ensure control of vital parameters, including input/output return loss and insertion loss.

Designed especially for high power applications, RF directional couplers are able to operate with up to 25 watts of RF input. These reactive devices feature very low insertion loss, and the majority of models feature an internal 50-ohm termination. In such cases, power that is coupled from various power incidents to the output port will be absorbed and won’t be available to the user. However, 4-port models feature both the reflected and incident coupled power available.

Directional couplers are fundamentally meant to make two output signals available by operating on an input. Having said that, when input is applied to an internally terminated coupler’s opposite port, only a single output signal can be produced. Please take a moment to look at our site: directional couplers

Just like with any type of system, or component, there are many specifications that are associated with RF directional couplers:

Coupling Loss – This refers to the amount of power that is lost to port 3 (the coupled port) and to port 4 (the isolated port). With reasonable directivity, the power that is unintentionally transferred to port 4 will be negligible in comparison to that which is intentionally transferred to port 3.

Directivity – This refers to the difference in power level between port 3 and port 4, and is a measure of the independence of the coupled and isolated ports. Since it is not possible to construct a perfect coupler, a certain amount of unintended coupling will exist between all signal paths.

Main line loss – This refers to sensitive loss as a result of heating. This particular value is added to the power reduction that is transferred to the coupled port and isolated port.

Isolation – This refers to the difference in power level between port 1 and port 4.

Applications of Directional Couplers

The traits of these directional couplers enable many signal processing functions, including the following:

  • Measuring reflected and incident power to determine:
  • VSWR
  • Power flow monitoring
  • Signal generator/oscillator leveling
  • Signal sampling
  • Signal injection

Differences Between 3- Versus 4-Port Couplers

A directional coupler is essentially a 4-port network. The auxiliary line and main-line both have 2 ports. The isolated port of a three-port coupler is internally terminated. When all four ports are available, the device is referred to as a “bi-directional coupler.” The directivity of a coupler is heavily influenced by the impedance match that is provided by the isolated port’s termination. High performance is ensured by internally furnishing that termination.