Abstract: An opportunistic modem (OM) system receives user data at an input port and transmits a modem output signal at an output port. In one aspect the data is initially transmitted over a first carrier in the modem output signal having a first frequency and bandwidth. Subsequently a second carrier having a second frequency and bandwidth is established, initially used to transmit pilot data, and then the user data is divided between the first and second carriers in the modem output signal. In another aspect the data is initially transmitted over a first and a second carrier in the modem output signal having respective first and second frequencies and bandwidths. Subsequently the second carrier is used to transmit pilot data for a period time. After the period of time the second carrier is de-established. In another aspect establishment and de-establishment of carriers is performed in response to detected interference.

Abstract: An opportunistic modem (OM) system receives user data at an input port and transmits a modem output signal at an output port. In one aspect the data is initially transmitted over a first carrier in the modem output signal having a first frequency and bandwidth. Subsequently a second carrier having a second frequency and bandwidth is established, initially used to transmit pilot data, and then the user data is divided between the first and second carriers in the modem output signal. In another aspect the data is initially transmitted over a first and a second carrier in the modem output signal having respective first and second frequencies and bandwidths. Subsequently the second carrier is used to transmit pilot data for a period time. After the period of time the second carrier is de-established. In another aspect establishment and de-establishment of carriers is performed in response to detected interference.

Abstract: An adaptive interference canceller for canceling an interfering signal corresponding to a delayed, frequency translated, amplitude and phase offset version of a transmitted signal contained in a composite received signal relayed through a relay system such as a satellite transponder. The canceller digitally downconverts the received signal and a local replica of the transmitted signal from IF to baseband, applies a variable delay and frequency compensation to the replica as a coarse delay and frequency correction, and tracks fine delay, amplitude and phase differences using an adaptive finite impulse response filter to generate a cancellation signal corresponding to the delayed and frequency shifted version. A minimum output power process produces an error signal that drives the variable delay and adaptive filter to minimize the power in the signal of interest to maximize cancellation of the interfering signal.

Abstract: An adaptive interference canceller for canceling an interfering signal corresponding to a delayed, frequency translated, amplitude and phase offset version of a transmitted signal contained in a composite received signal relayed through a relay system such as a satellite transponder. The canceller digitally downconverts the received signal and a local replica of the transmitted signal from IF to baseband, applies a variable delay and frequency compensation to the replica as a coarse delay and frequency correction, and tracks fine delay, amplitude and phase differences using an adaptive finite impulse response filter to generate a cancellation signal corresponding to the delayed and frequency shifted version. A minimum output power process produces an error signal that drives the variable delay and adaptive filter to minimize the power in the signal of interest to maximize cancellation of the interfering signal.

Abstract: An adaptive interference canceller for canceling an interfering signal corresponding to a delayed, frequency translated, amplitude and phase offset version of a transmitted signal contained in a composite received signal relayed through a relay system such as a satellite transponder. The canceller digitally downconverts the received signal and a local replica of the transmitted signal from IF to baseband, applies a variable delay and frequency compensation to the replica as a coarse delay and frequency correction, and tracks fine delay, amplitude and phase differences using an adaptive finite impulse response filter to generate a cancellation signal corresponding to the delayed and frequency shifted version. A minimum output power process produces an error signal that drives the variable delay and adaptive filter to minimize the power in the signal of interest to maximize cancellation of the interfering signal.