When you are building power relays for communications equipment, you need a coupler to sample and analyze the power flowing through the system. Choosing the right one can impact which direction you can monitor, inflow and outflow, as well as how much signal loss there is in the equipment. To find the right coupler for your needs, it is important to look at the direction or directions each one is designed for as well as which of the ports are connected.
Direction
The direction power flows through your couplers determines whether you are sampling the forward-wave, into the system, or backward-wave, out from it. Some directional couplers are designed to monitor both flows, but others will need to be physically turned to sample the reverse power. If you only need to measure the power flow in one direction, then simpler couplers will usually suffice, but multi-directional units with complicated designs can have the least amount of signal loss.
Connected Ports
There are three or four ports for your coupler which allow power to flow through the system in one direction, taking up two ports, while sampling the flow in either one or two directions with the remaining ports. The loads on your coupler’s connected ports can affect how well the power flows are monitored and how much signal is lost in the system. Most couplers will have ideal load ranges listed in the product description and it is a good idea to choose one where your expected loads land in the middle of the range.
Choosing the right directional power coupler for your communications system can become highly technical when you get into specifics of directions sampled, port loads and signal loss. It is a good idea to start by determining whether you need to monitor forward-wave, backward-wave or both and choose how many connected ports and which load range you need from the remaining options.
