13.75 - 14.5GHz Microwave RF Directional Coupler

A directional coupler is a measuring device that can receive the transmission line between the RF source and the load such as signal generators, vector network analyzers and transmitters, used to measure the RF power (forward component) from the RF source to the load, and The power (reflected component) of the RF source reflected back from the load. If the forward and reflected components are measured, the total power, the return loss of the load and the standing wave ratio can be calculated.

(Image source: Digi-Key Electronics) Normally, the power supply is connected to the input port of the switch, and the load is connected to the output or transmission port. The output is the attenuated forward signal. The attenuation value is shown in the schematic diagram of the three-port device principle. In a three-port device, the isolated port is internally terminated; in a four-port device, the output of the port is proportional to the reflected signal. For example, in a four-port configuration, the input port points to the switch port, indicating that it receives a positive component , And the output port is connected to the isolated port, which is used to read the reflected signal. port. However, the port names of various vendors are relatively uniform.

For a three-port device, reverse input and output ports and switch port 3 to become an isolated port. In a four-port device, reverse input and output ports are interchanged and the ports are isolated. exchange.

The output of the supplement is a radio frequency signal. The output of the supplemental and isolated port is usually connected to a vertical or RMS detector and can generate the relevant baseband signal for the forward and reflected power reflections. .

In some cases, the back-to-back connection of two directional replacers can form a dual directional replacer, and the brake minimizes the leakage between the replacement port and the isolation port.