What are Bidirectional Amplifiers?

A Bi-directional amplifier is a device that supports two-way communications and amplifies the signal in both transmit and receive mode. It consists of a power amplifier (PA) at the transmit end and a low noise amplifier (LNA) at the receive end. In receive mode, this device amplifies a weak input signal and feeds it to the radio. While in transmit mode, it amplifies the signal coming from the radio and transmits it further, extending the range of the signal.

Bi-directional amplifiers are most often used to extend the range of a cellular or radio systems. They are also used for transmitting and receiving radio signals in key applications such as unmanned aerial vehicles (UAV), unmanned ground vehicles, L and S-band radar, military radio, commercial air traffic control, weather and earth observation, satellites and high gain driver power amplifiers.

There are two types of Bi-Directional amplifiers:

Full-duplex Bidirectional Amplifier: A full-duplex bi-directional amplifier can simultaneously perform transmit and receive function. This simultaneous operation is possible by having a separate transmit and receive frequency or by frequency division multiplexing (FDM). This amplifier uses duplex filters to prevent the transmit signal from interfering with the receive channel.

Half-duplex Bidirectional Amplifier: A half-duplex bi-directional amplifier performs either the transmit or receive function at one time. In this amplifier, transmit and the receive function are selected with the help of a switch at the input and output ports, or by the use of intelligent biasing.