Browse Prior Art Database

Power Control for Satellite Transponder

IP.com Disclosure Number: IPCOM000045125D
Original Publication Date: 1983-Feb-01
Included in the Prior Art Database: 2005-Feb-06
Document File: 3 page(s) / 47K

Publishing Venue

IBM

Related People

Kunzinger, CA: AUTHOR

Abstract

Briefly, this article describes an algorithm for controlling the power and operating point of a satellite transponder in an FDM (frequency division multiplexing) communication system. The uplink attenuation for a given earth station is determined by comparing transmitted power levels and corresponding returned power levels. The transmitted power levels are adjusted to compensate for uplink attenuation. If all earth stations in the system are similarly controlled, the transponder operating point can be maintained in a linear range.

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Power Control for Satellite Transponder

Briefly, this article describes an algorithm for controlling the power and operating point of a satellite transponder in an FDM (frequency division multiplexing) communication system. The uplink attenuation for a given earth station is determined by comparing transmitted power levels and corresponding returned power levels. The transmitted power levels are adjusted to compensate for uplink attenuation. If all earth stations in the system are similarly controlled, the transponder operating point can be maintained in a linear range.

In an FDM satellite system, several independent channels may be in use simultaneously. The amount of power actually delivered to the satellite over each of the channels must be controlled to assure that the satellite always operates in a linear region. If the satellite becomes saturated, inter-modulation distortion in a given channel will distort signals in other channels. The technique described below establishes a transmitted power level at each earth station to limit the total received power at the satellite.

Fig. 1 shows an earth station A which transmits an uplink signal 12 modulated at a given RF level to a geostationary satellite 10. The uplink signal is broadcast by satellite 50 to a remote earth station B and to the earth station A. The signal returned to earth station A is identified as downlink signal 14. The same signal delivered to earth station B is identified as downlink signal 16.

Weather conditions, such as the rainstorm represented in Fig. 1, can attenuate the uplink signal. The downlink signal 14 is further attenuated since it returns through the same environment.

Fig. 2 is a graph of the power "gain" over the channel between earth station A and satellite 10. The terms used in the graph are defined in the list below:
Pta - transmitted power at earth station antenna.

Pra -...