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A communications satellite's transponder is the series of interconnected units that form a communications channel between the receiving and the transmitting antennas. [1] It is mainly used in satellite communication to transfer the received signals. A transponder is typically composed of: an input band-limiting device (an input band-pass filter),
In telecommunications, a transponder is a device that, upon receiving a signal, emits a different signal in response. [1] The term is a blend of transmitter and responder . [ 2 ] [ 3 ]
A transponder (short for transmitter-responder [1] and sometimes abbreviated to XPDR, [2] XPNDR, [3] TPDR [4] or TP [5]) is an electronic device that produces a response when it receives a radio-frequency interrogation.
The initial device was passive, powered by the interrogating signal, and was demonstrated in 1971 to the New York Port Authority and other potential users. It consisted of a transponder with 16 bit memory for use as a toll device. The basic Cardullo patent covers the use of radio frequency (RF), sound and light as transmission carriers.
The transponder emits a signal when it is interrogated by the secondary radar. In a transponder based system signals drop off as the inverse square of the distance to the target, instead of the fourth power in primary radars. As a result, effective range is greatly increased for a given power level.
Soon after the introduction of radar, the radio transponder appeared. Transponders are a combination of receiver and transmitter whose operation is automated – upon reception of a particular signal, normally a pulse on a particular frequency, the transponder sends out a pulse in response, typically delayed by some very short time.
These latter systems attempted to get around the problem of reading large numbers of transponders in a read field by using the High Frequency 13.56 MHz RFID methodology that allowed transponders to use anti-collision algorithms to avoid tags interfering with each other's signal during the down-link between transponder and reader.
The transponder acts as an identification tool for aircraft allowing ATC towers to immediately recognize the identity of each plane. They work by recognizing radar frequencies as they interact with the plane. The transponder alerted by the radar responds by sending a signal of its own back to the Tower, which identifies the aircraft.