Pulse or digital communications – Repeaters – Testing
Patent
1989-06-28
1990-10-23
Safourek, Benedict V.
Pulse or digital communications
Repeaters
Testing
455 12, 455 60, 455 63, 342353, 342361, H04B 176, H04B 710
Patent
active
049658093
ABSTRACT:
In a satellite communications system, a rotatable 90.degree. phase shifter and a rotatable 180.degree. phase shifter introduce variable phase shifts to a single pilot signal, which is transmitted to the satellite. Downlink cross-polarization interference cancelling control signals are derived from a beacon signal received from the satellite. A pulse sequence is generated to modulate the amplitude of a carrier to produce an ASK signal as the pilot signal. A correlation calculator provides coarse mode interference cancellation by estimating uplink cross-polarization interference components from the downlink cross-polarization cancelling control signals and adjusting the angle settings of the 90.degree. and 180.degree. phase shifters with the estimated components. The pilot signal is transmitted back to the earth and synchronously detected with the pulse sequence to derive a DC signal which represents an uplink cross-polarization interference. A stepwise tracking controller provides fine mode interference cancellation by stepwisely varying the 90.degree. and 180.degree. phase shifters by predetermined amounts an detecting previous and recent values of the synchronously detected DC signal resulting from the stepwise variations, and repeating the stepwise variations until a difference between the previous and recent values is substantially reduced to a minimum.
REFERENCES:
patent: 4146893 (1979-03-01), Inagaki et al.
patent: 4369519 (1983-01-01), Yuuki et al.
patent: 4857858 (1989-08-01), Tahara
NEC Corporation
Safourek Benedict V.
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