diplexer

A diplexer is a passive electronic device that combines or separates two different radio frequency signals, typically operating in different frequency bands. It allows two different signals to share a single transmission line, such as a coaxial cable, without significant interference. This is achieved by routing each signal to its intended destination based on its frequency.

Diplexers are commonly used in telecommunications, satellite television, and amateur radio. For example, in satellite TV systems, a diplexer can be used to combine the horizontal and vertical polarization signals from a satellite dish onto a single cable running into the house. At the receiver, another diplexer separates these signals for the tuner. Similarly, in some cable television systems, diplexers allow different frequency channels to be transmitted over the same cable.

The core principle behind a diplexer's operation is its frequency selectivity. It contains filters that allow signals within a specific frequency range to pass through to one port while blocking signals outside that range. The other port is designed to pass signals from a different, non-overlapping frequency range. This selective filtering ensures that the combined signals do not interfere with each other and that signals are directed to the correct receiver or transmitter. The design of a diplexer depends on the specific frequencies it needs to handle and the desired isolation between the bands.