Duplexer is a device which allows sharing a single antenna for receiver operating on a frequency signal and transmitter operating on different frequency.
The task of the duplexer is to coordinate the time sharing of the transmission and reception activities with the least of interaction and degradation of the two radio frequency signals.
Diplexer
Diplexer is like multiplexer. Diplexer is a three-port, frequency-dependent device that used to separate or to combine of different signals from an antenna.
A typical diplexer consists of two fixed tuned band-pass filters that share a common port. The common port and the output of the two filters form the three terminals of the diplexer. Signals applied to the common port are separated in accordance with the pass band frequencies of the filters.
Radio Frequency Duplexer
Radio frequency duplexers’ type consists of surface mount, flat pack, through-hole, plug-in, and waveguide assembly techniques. Most important performance specification needs to be considered when selecting RF duplexers are signal rejection of the receiver over transmission signal and vice versa, insertion loss, and Voltage Standing Wave Ratio (VSWR).