06.16.2011 11:50 AM
Originally featured on BroadcastEngineering.com
Second R&O aims to mitigate space path interference

The FCC June 14 released rules to mitigate space path interference between the 17/24GHz Broadcasting-Satellite Service (BSS) space-to-Earth transmissions and the feeder link receiving antennas of Direct Broadcast Satellite Service (DBS) space stations that operate in the same frequency band.

The rules, adopted in the commission’s Second Report and Order (R&O), establish an off-axis power flux density (pfd) coordination trigger for 17/24GHz BSS space stations.

They also require a minimum orbital separation requirement of 0.2 degrees between 17/24GHz BSS satellites and DBS satellites, and restrain orbital inclination and eccentricity of 17/24GHz BSS satellites. The new commission rules also now require 17/24GHz BSS space station applicants to file predicted and measured transmitting antenna off-axis gain information.

The commission also set up a way for existing holders and pending applicants to file information related to the new rules.

In its Second R&O, the commission laid out the sources of space path interference, which occurs when downlinked 17/24GHz signals are received by the feeder link or telecommand antennas of a close DBS space station.

Several factors contribute to the amount of space path interference, the Second R&O said. They include the specific orientation of the transmitting 17/24GHz BSS space station and its separation from the receiving antenna on DBS space stations; the power level of transmissions from the 17/24GHz BSS space station; and the off-axis gain discrimination of the 17/24GHz BSS space station transmitting antenna and that of the DBS space station antenna.

The commission added that managing space path interference is likely to be even more difficult when the receiving DBS satellite is located within a few tenths of a degree in its orbital location to that of a 17/24GHz space station.

To help avoid harmful interference at DBS receive antennas, the new rules set up an off-axis power flux density (pfd) coordination trigger of -117 dBW/m2/100kHz.

The new pdf applies to any licensed U.S. DBS space station, any foreign DBS space station authorized to provide service in the United States, and any DBS space station proposed in a previously filed application for a U.S. license or U.S. market access, the Second R&O said.

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