Abstract: Methods and apparatus for use in making improved symbol decisions in a demodulator in the presence of distortion in the received signaling. In one implementation, a method includes the steps of: determining a centroid symbol location for a received symbol of a constellation, the centroid symbol location different than an ideal symbol location due to distortion of the received symbol; and adjusting a decision line bounding the received symbol based on the centroid symbol location. In preferred embodiments, the method is implemented in a satellite communication system, which the distortion is a nonlinear distortion and is caused by a high power amplifier at the transmitting terminal and in which bandwidth efficient modulation formats are used to transmit data at a high rate. In some embodiments, centroid symbol locations are used to improve soft decision decoding.

Abstract: An equalizing apparatus includes an equalizer which has a plurality of adjustable tap weights that equalizes a received signal based on values of the adjustable tap weights, a tap weight update calculation unit coupled to the equalizer and which determines tap weight updates for use in adjusting the tap weights during operation of the equalizer, an offset memory that stores one or more tap weight update offset values and a summer coupled to the tap weight update calculation unit and to the offset memory. The summer combines each of the tap weight updates with one of the tap weight update offset values to produce modified tap weight updates which, in turn, are provided to the equalizer to adjust the tap weights.

Abstract: In a system for modulating an RF carrier, the RF carrier is fed through a lowpass filter and phase shifted approximately ?90 degrees. The RF carrier is also fed through a high pass filter and phase shifted approximately +90 degrees. A switch connected to the output of the lowpass filter and connected to the output of the highpass filter, selects and outputs either the ?90 degree phase shifted carrier output from the lowpass filter or the +90 degree phase shifted carrier output from the highpass filter depending on a switching state determined by data bit information received at a data port to produce a BPSK modulated RF carrier. Two such BPSK modulators may be combined using lowpass and highpass filters to form a QPSK modulator. Two such QPSK modulators may be combined with an attenuator to form a QAM modulator.

Abstract: A telecommunication system includes a transmitter configured to modulate a forward link RF carrier with a first set of data; a receiver configured to demodulate a second set of data from a return link RF carrier; an orthomode transducer having two linear ports and a circular waveguide port, where one of the linear ports is connected as an input from the transmitter and another linear port is simultaneously connected as an output to the receiver; an antenna; and a linear-to-circular polarizer connected to the circular waveguide port and connected to the antenna, where the linear-to-circular polarizer is configured so that a first linear polarization at the circular waveguide port results in a first circular polarization at the antenna and a second circular polarization at the antenna results in a second linear polarization at the circular waveguide port.

Abstract: An equalizing apparatus includes an equalizer which has a plurality of adjustable tap weights that equalizes a received signal based on values of the adjustable tap weights, a tap weight update calculation unit coupled to the equalizer and which determines tap weight updates for use in adjusting the tap weights during operation of the equalizer, an offset memory that stores one or more tap weight update offset values and a summer coupled to the tap weight update calculation unit and to the offset memory. The summer combines each of the tap weight updates with one of the tap weight update offset values to produce modified tap weight updates which, in turn, are provided to the equalizer to adjust the tap weights.

Abstract: Methods and apparatus for use in making improved symbol decisions in a demodulator in the presence of distortion in the received signaling. In one implementation, a method includes the steps of: determining a centroid symbol location for a received symbol of a constellation, the centroid symbol location different than an ideal symbol location due to distortion of the received symbol; and adjusting a decision line bounding the received symbol based on the centroid symbol location. In preferred embodiments, the method is implemented in a satellite communication system, which the distortion is a nonlinear distortion and is caused by a high power amplifier at the transmitting terminal and in which bandwidth efficient modulation formats are used to transmit data at a high rate. In some embodiments, centroid symbol locations are used to improve soft decision decoding.

Abstract: The present invention discloses a predistortion modulation system for use in satellite systems. A typical apparatus of the invention includes a predistortion processor for predistorting a digital data source signal to reduce transmission distortion and an adaptive algorithm processor for controlling the predistortion processor according to a received a feedback signal derived from the transmitted data source signal. In further embodiments, the non-linear and linear predistortion is adaptively controlled. The invention is particularly useful in a digital cinema satellite system.

Abstract: An equalizing apparatus includes an equalizer which has a plurality of adjustable tap weights that equalizes a received signal based on values of the adjustable tap weights, a tap weight update calculation unit coupled to the equalizer and which determines tap weight updates for use in adjusting the tap weights during operation of the equalizer, an offset memory that stores one or more tap weight update offset values and a summer coupled to the tap weight update calculation unit and to the offset memory. The summer combines each of the tap weight updates with one of the tap weight update offset values to produce modified tap weight updates which, in turn, are provided to the equalizer to adjust the tap weights.

Abstract: An adaptive quadrature amplitude modulation (“QAM”) decoding system for use in, for example, high speed, bandwidth efficient QAM communication systems includes a circuit that adaptively adjusts gain and voltage bias and provides adaptive equalization feedback based on the same signal used to decode the QAM symbols.

Abstract: A digitally controllable nonlinear pre-equalizer system receiving an input signal and generating an output signal, the system including a splitter for dividing the input signal into a first signal path and a second signal path, an attenuator and a time delay element in the first signal path, the attenuator and the time delay element operable to generate a linear signal, a mixer and a vector modulator in the second signal path, the mixer being responsive to a signal from a digital to analog converter coupled to a processor chip providing a digital signal to the digital to analog converter, the mixer and vector modulator operable to generate a nonlinear signal, and a summer for summing the linear signal and the nonlinear signal to generate the output signal.

Abstract: A digitally controllable nonlinear pre-equalizer system receiving an input signal and generating an output signal, the system including a splitter for dividing the input signal into a first signal path and a second signal path, an attenuator and a time delay element in the first signal path, the attenuator and the time delay element operable to generate a linear signal, a mixer and a vector modulator in the second signal path, the mixer being responsive to a signal from a digital to analog converter coupled to a processor chip providing a digital signal to the digital to analog converter, the mixer and vector modulator operable to generate a nonlinear signal, and a summer for summing the linear signal and the nonlinear signal to generate the output signal.

Abstract: The present invention discloses a predistortion modulation system for use in satellite systems. A typical apparatus of the invention includes a predistortion processor for predistorting a digital data source signal to reduce transmission distortion and an adaptive algorithm processor for controlling the predistortion processor according to a received a feedback signal derived from the transmitted data source signal. In further embodiments, the non-linear and linear predistortion is adaptively controlled. The invention is particularly useful in a digital cinema satellite system.

Abstract: A telecommunication system includes a transmitter configured to modulate a forward link RF carrier with a first set of data; a receiver configured to demodulate a second set of data from a return link RF carrier; an orthomode transducer having two linear ports and a circular waveguide port, where one of the linear ports is connected as an input from the transmitter and another linear port is simultaneously connected as an output to the receiver; an antenna; and a linear-to-circular polarizer connected to the circular waveguide port and connected to the antenna, where the linear-to-circular polarizer is configured so that a first linear polarization at the circular waveguide port results in a first circular polarization at the antenna and a second circular polarization at the antenna results in a second linear polarization at the circular waveguide port.

Abstract: In a system for modulating an RF carrier, the RF carrier is fed through a lowpass filter and phase shifted approximately −90 degrees. The RF carrier is also fed through a high pass filter and phase shifted approximately +90 degrees. A switch connected to the output of the lowpass filter and connected to the output of the highpass filter, selects and outputs either the −90 degree phase shifted carrier output from the lowpass filter or the +90 degree phase shifted carrier output from the highpass filter depending on a switching state determined by data bit information received at a data port to produce a BPSK modulated RF carrier. Two such BPSK modulators may be combined using lowpass and highpass filters to form a QPSK modulator. Two such QPSK modulators may be combined with an attenuator to form a QAM modulator.