A Brief Insight of Coaxial Couplers

The RF Directional Coupler is an instrument for measuring or monitoring microwave power consisting of a line section which is inserted in any of the RF-lines. It could be coaxial lines, waveguides, tri-plate lines, wirelines, etc. The line is inserted between a transmitter or generator or amplifier and its load. It allows sampling of microwave energy without moving parts and adjusting. It is a simple and convenient means to do so.

Raditek Directional couplers are used for various applications that involve measurement, power monitoring, etc. A directional coupler can be used for isolating, eliminating or combining signals in microwave signal routing and RF. Coupled, Input, Transmitted and Isolated – are the four ports in a directional coupler.

The distinguishing features of directional couplers can be listed as coupling, insertion loss, mainline and auxiliary line, directivity, power handling capability, bandwidth, frequency sensitivity, etc. There are various types of directional couplers which have different sampling capabilities like coaxial directional coupler, dual directional coupler, Hybrid couplers, Bethe-hole coupler, Multi-hole coupler, etc.

Coaxial Coupler

One of the various types of the directional coupler is a Coaxial Coupler. They are usually used at frequencies ranging from 10 MHz to 40 GHz. They are commonly designed for low Voltage Standing Wave Ratio (VSWR) and insertion loss, high directivity, and flat coupling level.

They are suitable for 49GB systems, and some of its applications include general purpose test and measurement systems. There are two designs in the coaxial directional coupler – single-ended and dual directional.

The design of a single-ended coaxial directional coupler has the general appearance of a section of the coaxial line, with a second parallel section of line with one terminated end. The dual-directional coaxial coupler consists of two single-ended directional couplers connected back-to-back. They are used to allow measurement of forward and reflected power levels.


There is a varied range of applications for directional couplers. It is used as power sampler in measurement systems. It is commonly used for measuring and monitoring microwave power. It is also used for measuring and monitoring of frequency in operating systems.

One can guarantee constant conditions for physical, thermal or chemical process in the load as another application of the directional coupler is to use the signal of the forward wave for the regulation system to keep forward power constant. Directional reflectors can also be used for making use of isolation. In case isolation is high, they combine signals to feed a single line to a receiver.

Raditek couplers can be seen at https://raditek.com/smt-quadhybrid.htm