An RF Duplexer is an electronic device used in RF communications transceiver circuits to allow sharing of the same antenna. This is important because transmitters are high power large signal devices, and receivers are extremely sensitive small signal devices. Without a duplexer to isolate the receiver and transmitter with low insertion loss for the antenna to the receiver, the transmitter overloads and most often damages a receiver if they share the same antenna. Duplexers are available in different types. RF switches can alternatively connect, transmit or receiver to the antenna in a time multiplexing arrangement. Circulators are electromagnetic three or four-port devices that only allow current to flow in one direction due to ferromagnetic effects in a ferrite material. Some materials (like garnets) can be used as optical circulators. Orthomode transducers are waveguide devices that use microwave RF signal polarization to keep signals separate. They are used in terrestrial microwave and VSAT applications. Frequency duplexers are highly selective filters that allow a signal to flow through from the antenna to the receiver at the receive frequency, but present a very high impedance to the transmitter frequency. This highly selective filter must do this so as to not cause an unacceptable reduction in sensitivity through losses in the antenna to the receiver path. Read more Read less