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transponder (TP)

Transponders, a made-up word from transmitter and responder, are used in high-frequency transmission systems with satellites, in terrestrialsystems, in RFID and in optical networks. They are used for frequency or wavelength conversion from one frequency or one wavelength

to another.

Transponders in satellite transmission

In satellite transmission

, satellite transponders perform all the message processing of the signals. They receive the uplink signal from the earth (14 GHz), transform it into a lower frequency of 11 GHz to 12 GHz, amplify it and send it back to earth as a downlink signal. The bandwidths at which transponders operate depend on the satellite transmission and range up to 72 MHz

. Common bandwidths are 26 MHz, 30 MHz, 33 MHz and 36 MHz.Satellite transponders are divided into transparent and regenerative transponders. In the transparent transponders, the frequency is converted and the signal is amplified. The regenerative transponders have all the functions of the transparent transponders, in addition they work with a regenerator with which the signal is also regenerated, they have on-board processing (OBP) for demodulation, signal conditioning and remodulation. With the regenerative approach, noise can be reduced, the transmission quality of the channel can be improved, and multiple single channel per carrier

(SCPC) or TDMA channels can be combined into one TDM downlink channel

Net bit rates at the different transponder bandwidths in DVB-S

Net bit rates at the different transponder bandwidths in DVB-S

The gain of satellite transponders ranges from 100 dB to 120 dB, and the transmit power can be as high as 100 W. Communications satellites typically have twenty or more transponders. In order for the transponders to make the best use of the available frequency bands and transmit as many television channels as possible within them, the carrier frequencies are radiated in different polarizations

: Horizontal and vertical as well as left and right circular

Transponders in RFID technology

In RFID, the contactless data carrier is the transponder. It consists of a coupling element, depending on the RFID frequencies an antenna coil or a dipole antenna and a microprocessor. The transponder, which is located in the RFID tag, does not have its own power supply in passive RFID systems, but obtains its supply voltage from the electromagnetic fields emitted by the RFID readers. It is passive and is only activated within a certain operating distance of a reader.

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Englisch: transponder - TP
Updated at: 10.11.2013
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Translations: DE