Abstract: A transmitter (305) for transmitting reverse optical signals in a broadband communications system (300) that includes a converter (320) for digitizing the analog RF signals and a carrier-detect circuit (330) coupled to the converter (320) for detecting when digital RF signals are present at the output of the converter (320). When the carrier-detect circuit (330) detects digital RF signals, the carrier-detect circuit (330) allows the digital RF signals to be transmitted upstream through the broadband communications system (300). A digital network (310) then combines the received digital RF signals with other digital RF signals from additional transmitters (305). The combined digital signals are then provided to a receiver (315) that includes a converter (335) for returning the digital RF signals to analog RF signals and then providing the analog signals to a headend for further processing.

Abstract: A transmitter (305) for transmitting reverse optical signals in a broadband communications system (300) that includes a converter (320) for digitizing the analog RF signals and a carrier-detect circuit (330) coupled to the converter (320) for detecting when digital RF signals are present at the output of the converter (320). When the carrier-detect circuit (330) detects digital RF signals, the carrier-detect circuit (330) allows the digital RF signals to be transmitted upstream through the broadband communications system (300). A digital network (310) then combines the received digital RF signals with other digital RF signals from additional transmitters (305). The combined digital signals are then provided to a receiver (315) that includes a converter (335) for returning the digital RF signals to analog RF signals and then providing the analog signals to a headend for further processing.

Abstract: Apparatus for using a low earth orbit satellite for reverse path communication in a subscription information service delivery system comprises a receiver adapted to receive a subscription information service signal at frequencies exceeding 1 GHz via a first path. Responsive to a poll, the receiver is adapted to transmit a response signal to the poll at frequencies under 1 GHz via a second path to a low earth orbit satellite. The polling request may be transmitted with the subscription information service signal or through the low earth orbit satellite. Preferably, the polling request is addressed and comprises a response message length field. The response comprises a service provider identifier and a subscriber identifier and further, preferably comprises response data encrypted by a key known to the service provider.

Abstract: Diversity combiners for use in satellite and other communication systems. Such combiners are able to accommodate fast and dramatic signal fades and doppler shifts inherent in satellite communications by employing differential and common mode automatic phase control and differential and common mode signal weighting techniques. Phase control takes place in these combiners after signal weighting to decrease differential loop phase detector gradients and noise bandwidth as a function of signal-to-noise imbalance of the channels. An acquisition circuit is provided to deactivate the differential phase control loop when either signal falls below a predetermined level. During times when the faded signal reemerges, the combiner establishes optimal combining with minimum phase discontinuities on the output or phase lock reacquisition disturbances.