Many who are just starting to “fiddle” with electronics and gadgets may not know exactly what a bidirectional coupler is. For those people, here is a basic breakdown of just what such a device is used for.
A bidirectional coupler is essentially just a four-port device where one of the ports is necessarily closed off from the input port. Technically speaking, all bidirectional coupler are networks which operate via a passive reciprocal method.
When it comes to these kinds of couplers, all of the ports will be matched and the signal will lossless. They can come in four different “flavors” known as waveguide, stripline, coax, and microstrip. What the bidirectional coupler is used for is to analyze the incoming and outgoing signals, to ensure they retain their clarity and do not suffer from lossless signal frequency.
So what is technically meant by directional? Well, the coupler is possessed of 4 ports. One of the ports is known as a through port. This is the location in the coupler where the signal actually exists, for the main part. Another of the ports is known as the coupled port. This port is where the portion of the signal lives, where it is measured in decibels. The next port is dubbed the isolated port. This is where the signal is terminated. The fourth port is known as the input port, whereby the signal enters the coupler.
There are also other couplers which can be used although not quite for the same purpose. Some of them go by the names “lumped elements” and “hybrid couplers”. As can be seen here, a bidirectional coupler can be a very handy device to have, especially in regards to operating devices that function or rely on microwaves. Hopefully this article gave you a base of knowledge to work with.