Upstream frequency control for DOCSIS based satellite systems
First Claim
1. A method for minimizing frequency error of satellite modems at a satellite gateway, comprising:
- locking downstream baud rate and elements controlling upstream frequency to a master frequency reference;
sending upstream satellite frequency offset information to satellite modems;
enabling each satellite modem to lock each satellite modem'"'"'s master oscillator to a recovered baud rate; and
enabling each satellite modem to calculate an upstream frequency offset, wherein said upstream frequency offset is compensated for by shifting a center frequency of each of said satellite modems.
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Abstract
A system and method for minimizing the frequency error of satellite modem signals at a satellite gateway. The gateway downstream baud (symbol) clock and the elements that control the upstream frequency (i.e., local oscillators in the conversion chain, A/D sample clocks) are locked to a common frequency reference. The gateway sends upstream satellite frequency offset information, such as satellite ephemeris data from which to calculate Doppler offset, to the satellite modem. The satellite modem locks the frequency of the satellite modems master oscillator to the recovered baud rate using a frequency locked loop. The satellite modem uses its master oscillator as the carrier reference for the upstream frequency up conversion. The satellite modem uses or calculates the upstream satellite frequency offset and compensates for this offset by shifting its center frequency.
47 Citations
5 Claims
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1. A method for minimizing frequency error of satellite modems at a satellite gateway, comprising:
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locking downstream baud rate and elements controlling upstream frequency to a master frequency reference;
sending upstream satellite frequency offset information to satellite modems;
enabling each satellite modem to lock each satellite modem'"'"'s master oscillator to a recovered baud rate; and
enabling each satellite modem to calculate an upstream frequency offset, wherein said upstream frequency offset is compensated for by shifting a center frequency of each of said satellite modems. - View Dependent Claims (2, 3, 4, 5)
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Specification