Abstract: A system and method for restricting access to a satellite repeater transponder (100) utilizes a pseudo-random noise generator (102) to automatically modulate a local oscillator (18) about a nominal frequency during frequency translation within the satellite transponder. The carrier signals of authorized user terminals (106) will be modulated with a matching or inverse noise waveform produced by a pseudo-random noise generator (114), so that the noise signal modulated onto the carrier signal will only be cancelled out in authorized transmissions. Thus, an unauthorized user terminal will be unable to recover the baseband signal due to insufficient carrier to noise ratio in the expanded bandwidth created by the pseudo-random frequency modulation in the satellite repeater.

Abstract: A system and method for determining the location of a source of interference for a communications satellite. The system has an antenna array located on the earth facing panel of the communications satellite. The method and system determine the direction of a source of interference relative to the satellite's own coordinate system. The angle of arrival of the interference signal is determined with respect to the horizontal and vertical baselines of the coordinate system and by comparing the outputs of the appropriate antennas in the antenna array.

Abstract: The new signal amplifiers dynamically adjust based on the signal's power level. When used on multi-beam satellites, increased signal power indicates an increase in traffic on the channel. The power level of the input signal is sensed and converted to a DC signal, which is applied to a control terminal of a power supply that regulates DC power supplied to the amplifier. During periods of increased traffic, an increase in system power is allocated to the channel. By monitoring traffic on a plurality of channels, available onboard power is allocated based upon the relative channel requirements. The sensed power of multiple channels is summed and scaled to determine the power requirement of the channel relative to the other channels. A command voltage received from a ground station may be switched in place of the summed voltage to allow amplification levels to be controlled from the ground station.

Abstract: A method and system for determining an actual location of a sense antenna associated with a phased array communications satellite. A plurality of calibration carrier signals are transmitted at known frequencies. Each of the plurality of calibration carrier signals are received at a second frequency and compared with each of the plurality of transmitted calibration carrier signals. The actual location of the sense antenna is determined based on the comparison between the known frequency and the second frequency. The phased array communications satellite then broadcasts communication signals based on the actual location of the sense antenna rather than a desired location of the sense antenna.

Abstract: In a satellite transponder architecture employing digital signal processing, a power monitor samples the data stream of carrier frequency samples on board the transponder and computes a power level for each of the carriers. This provides accurate and high frequency resolution power measurements within the communications link. These measurements are useful for computing critical transponder characteristics such as the effective isotropic radiated power (EIRP), receiver sensitivity, uplink sensitivity, operating points and, in a system using a phased array antenna, the total and component powers for each beam. The power monitor eliminates problems associated with external measurement methods, and improves the overall accuracy and reliability.

Abstract: The operating point of a nonlinear amplifier is determined by injecting a known test signal into the communication channel and measuring the gain of the amplified test signal. Each amplifier is characterized by a small signal gain curve that relates the gain of the test signal to the input power of the amplifier. In the amplifier's nonlinear range, the gain uniquely determines the input power level of the amplifier, which in turn uniquely determines the operating point of the amplifier. The invention is particularly applicable to satellite transponder architectures that employ "burst" transmission schemes and phased array antennas.

Abstract: An array antenna system (40) has a plurality of radiators (44) for generating a set of beams (48), wherein axes of the beams are spaced apart from each other allowing the respective beams to illuminate separate areas of the earth or other receiving region. A sequence of positional offsets (52) is applied to the set of beams by either mechanically (108) moving the radiators to redirect the beams, or by introducing a phase or time-delay taper (84) to the phase shifters (80) or delay lines of a beam former (38) for each of the beams. The succession of positional offsets redirects the beams along a path offset from a central location (50) of each beam, and passing between the sites of adjacent beams. This provides for improved uniformity of illumination of the receiving region.

Abstract: A management system and calibration method for use with a phased array antenna that increases its robustness to component changes or failures. The present invention employs a system level measurement of amplitude and phase, conducted during nodal operation, to determine on an element by element basis, the tracking performance of individual chains that for the antennas. This amplitude and phase information is employed to compensate the each chain for the measured error. The present system and method measures the amplitude and phase of individual element chains utilizing probe carriers. The required correction coefficients for each chain is determined from the measured amplitude and phase data, and each individual element chain is individually compensated to remedy the amplitude and phase errors. The present system and method generates a probe carrier that is applied to each element chain along with normal communication signal waveforms.

Abstract: The invention is a relay communications system which uses a single reference frequency signal generator to produce a plurality of precisely frequency synchronized code division multiple access radio frequency signals. A transmitter transmits the synchronized signals to a remote satellite based retransmitter which includes a slave oscillator precisely synchronized to the reference signal generator for down-linking the multiple radio frequency signals to a common radio frequency with all of the down-linked signals being in precise phase synchronism. The relative phase of the down-linked signals can be preserved or altered and the signals combined and amplified by a high-power amplifier operating in the saturation mode. The output from the high power amplifier is applied to a beamforming network to form an overlapping beam signal comprised of multiple code division multiple access information signals.

Abstract: Linearity and efficiency of a radio frequency multi-stage power amplification device 10 are increased by employing two tuned circuits 16 and 18 in the driver stage 12 and two tuned circuits 22 and 24 in the high power stage 14. After selecting elements of tuned circuits 22 and 24 in order to optimize the high power stage 14 for efficiency, linearity, and power output, elements are selected for tuned circuits 16 and 18 in order to cause the intermodulation output components associated with the driver state 12 to have a 180.degree. phase angle relative to the intermodulation output components associated with the high power stage 14. This phase angle relationship will cause the intermodulation output component products from the driver 12 and high power stages 14 to cancel.

Abstract: Frequency bands in spot beams received by a satellite transponder are selectively routed to transmitted spot beams. The total band width from each spot beam receiver is divided among a plurality of independently adjustable variable bandpass filters, and the outputs from the selected bandpass filters at each receiver are combined at the spot beam transmitters so that each downlink spectrum is made up of a frequency multiplex of selected bands from each uplink spot beam.