Дуплексер: Принцип работы, история и применение.

A duplexer is an electronic device that allows bi directional (duplex) communication over a single path. In radar and radio communications systems, it isolates the receiver from the transmitter while permitting them to share a common antenna. Most radio repeater systems include a duplexer. Duplexers can be based on frequency (often a waveguide filter), polarization (such as an orthomode transducer), or timing (as is typical in radar).

In radar, a transmit/receive (TR) switch alternately connects the transmitter and receiver to a shared antenna. In the simplest arrangement, the switch consists of a gas discharge tube across the input terminals of the receiver. When the transmitter is active, the resulting high voltage causes the tube to conduct, shorting together the receiver terminals to protect it, while its complementary, the anti transmit/receive (ATR) switch, is a similar discharge tube which decouples the transmitter from the antenna while not operating, to prevent it from wasting received energy.

A hybrid, such as a magic T, may be used as a duplexer by terminating the fourth port in a matched load. This arrangement suffers from the disadvantage that half of the transmitter power is lost in the matched load, while thermal noise in the load is delivered to the receiver.

The first duplexers were invented for use on the electric telegraph and were known as duplex rather than duplexer. They were an early form of the hybrid coil. The telegraph companies were keen to have such a device since the ability to have simultaneous traffic in both directions had the potential to save the cost of thousands of miles of telegraph wire. The first of these devices was designed in 1853 by Julius Wilhelm Gintl of the Austrian State Telegraph. Gintl's design was not very successful. Further attempts were made by Carl Frischen of Hanover with an artificial line to balance the real line as well as by Siemens & Halske, who bought and modified Frischen's design. The first truly successful duplex was designed by Joseph Barker Stearns of Boston in 1872. This was further developed into the quadruplex telegraph by Thomas Edison. The device is estimated to have saved Western Union $500,000 per year in construction of new telegraph lines. The first duplexers for radar, sometimes referred to as Transmit/Receive Switches, were invented by Robert Morris Page and Leo C. Young of the United States Naval Research Laboratory in July 1936.