Abstract: A method for AM in-band-on-channel (IBOC) digital audio broadcasting (DAB) uses a center channel signal in a central frequency band of an AM radio channel, the center channel signal is modulated by first and second versions of the program material to be transmitted. Sub-carriers in a upper and lower sidebands of the AM radio channel are modulated with addition digitally encoded portions of the program material. The upper sideband lies within a frequency band extending from about +5 k Hz to about +10 kHz from a center frequency of the radio channel and the lower sideband lying within a frequency band extending from about −5 k Hz to about −10 kHz from the center frequency of the radio channel. The center channel signal the upper and lower sideband sub-carriers are transmitted to receivers.

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: 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 broadcasting method encodes program material using convolutional codes having non-puncturable bits and puncturable bits and modulates orthogonal frequency division multiplexed carrier signals with the convolutional codes. The non-puncturable bits are carried by a first group of the carriers and the puncturable bits are carried by a second group of the carriers, where the first group of carrier signals is less susceptible to interference than the second group of carrier signals. The carrier signals are then broadcast to receivers which determine if the carriers in the second group have been corrupted and erase puncturable bits carried by any of the carriers which have been determined to be corrupted. This produces punctured codes which are subsequently decoded to recover the program material.

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.