Abstract: A method of broadcasting digitally encoded information includes the transmission of a plurality of orthogonal frequency division multiplexed sub-carriers. The sub-carriers are modulated by a digitally encoded signal representative of data to be transmitted, with the digitally encoded signal including a plurality of symbols having varying phase and amplitude components. The amplitude modulation can vary between two or more levels. Portions of the digitally encoded signal may be differentially imposed across the sub-carriers. The method also includes receiving the sub-carriers, demodulating the sub-carriers to recover the digitally encoded signal, and decoding the digitally encoded signal.

Abstract: The present invention provides for a receiver addressable AM compatible digital broadcast system and method. The digital broadcast signal includes a plurality of digitally modulated signals and an analog signal. A transmitter useable within the system includes a data combiner for generating an aggregate digital data signal, and a waveform generator for forming the digital broadcast signal. A receiver useable within the system comprises a waveform detector for separating the signals and a data parser for separating the digitally modulated signals. The present invention further provides for a method of selectively transmitting data via a digital broadcast signal. The method includes forming the digital broadcast signal from an analog signal and a plurality of digitally modulated signals, transmitting and receiving the digital broadcast signal.

Abstract: This invention provides a method for reducing peak to average power ratio in a radio frequency signal. The method comprises the steps of modulating a plurality of sub-carriers with a plurality of data symbol vectors to produce a first modulated signal; limiting the magnitude of the first modulated signal to produce a first limited modulated signal; demodulating the first limited modulated signal to recover the constellation points; predistorting the data symbol vectors to provide a minimum magnitude for in-phase and quadrature components thereof to produce predistorted data symbol vectors; modulating the plurality of carriers with the predistorted data symbol vectors to produce a second modulated signal; limiting the magnitude the second modulated signal to produce a second limited modulated signal; and reducing intermodulation products in the second limited modulated signal. Transmitters that perform the method are also included.

Abstract: A beam steering control for a mobile satellite communications antenna, includes an antenna having a steering mechanism; a dynamic rate sensor for producing a signal related to the rate of change of position of a vehicle to which the antenna is mounted; and a control system for controlling the steering mechanism, the control system including a satellite tracking loop, an inertial stabilization loop, a calibration algorithm for dynamically calibrating the rate sensor, and a satellite acquisition algorithm for determining a azimuth angle of the antenna relative to an inertial reference.

Abstract: A high power amplifier (10) includes intelligent independent fault tolerant amplifying modules (11). Each of the modules (11) includes a power amplifier (17) having a plurality of silicon carbide transistor circuits (27-30) coupled in parallel and driven by a silicon carbide transistor circuit (26). The module (11) also includes a dedicated hybrid controller (18) that monitors the operational conditions of the power amplifier (17) and optimizes these operational conditions in order to provide fault isolation and to avoid unwanted failure of the module (11) as a whole.

Abstract: A preamplifier system (10) is provided which amplifies and conditions an input electromagnetic signal for insertion into a high power amplifier. The preamplifier system (10) includes a plurality of cascaded amplifying stages (100a-100d) for incrementally amplifying the input electromagnetic signal, as well as bias control circuitry coupled to the amplifying stages (100a-100d) to electrically bias at least one of those stages into a Class A operational mode and an adjustable phase shift unit (300) coupled to at least one of the amplifying stages (100a-100d) for reversibly shifting the phase of the input electromagnetic signal in accordance with the given high power amplifier's configuration. Each amplifying stage (100a-100d) includes at least one transistor assembly device (110a-110d) having integrally formed therein a plurality of silicon carbide cells coupled one to the other.

Abstract: A hybrid system (18) for control and monitoring of an amplifier (330) is provided. The hybrid control system (18) includes an analog control subsystem (81) and a digital control subsystem (82). The analog control system provides an automatic gain control loop for maintaining the gain of amplifier (330) at a predetermined level. The digital control subsystem (82) monitors a plurality of operating characteristics of amplifier (330) and commands the analog control subsystem (81) to reduce the gain of amplifier (330) responsive to certain predetermined fault conditions. The digital control subsystem (82) shuts down amplifier (330) responsive to other predetermined fault conditions. The digital control subsystem (82) also controls the power-on sequence and power-down sequence for amplifier (330), insuring that the gate bias voltage is first applied or maintained before the drain voltage is applied or removed.