Motorola Corporation

Other

Richard A Bienz

Lansing M Carson

Terry L Hengl

Marty K Siemon

Estevan Marcial Gonzales

Daniel J Morelli

A method of avoiding the discarding of data in congested data networks includes receiving a data packet sent from a first station ( ) to a first transceiver located in the data network. The data packet is designated to be forwarded to a second station ( ) and the second station or a link, from a second transceiver to the second station, is temporarily busy. In this method the data packet is delayed by forwarding it from the first transceiver to a third transceiver ( ) which is not busy and is forwarded back to the second station at a later time. Since it takes time to forward the data package through one or more other transceivers, the network operates to delay or store the data packet until the second station is no longer too busy.

Data discard avoidance method

A method and apparatus for efficiently tracking satellites includes a geosynchronous satellite (10) for transmitting the ephemeris of non-geosynchronous satellites (20, 30) to a ground terminal (50). The ephemeris is computed by the non-geosynchronous satellites (20, 30) or by other means such as a ground station (60). A ground terminal (50) can quickly acquire a non-geosynchronous satellite (20, 30) by receiving fresh ephemeris data from a geosynchronous satellite (10), determining a location of a non-geosynchronous satellite (20, 30), and orienting an antenna.

Method and apparatus for efficient acquisition and tracking of satellites

A numerically controlled oscillator (11), (NCO), generates an NCO output (114) having a time-averaged frequency proportional to a rational number, even if the number of bits in the binary frequency control numbers (104, 106) is insufficient to represent the fractional part of the rational frequency number precisely. Frequency control numbers (104, 106) alternate between numerically adjacent values proportional to the desired time-averaged rational frequency control number. Frequency control numbers and their duty cycles are calculated for synthesizing a time-averaged rational frequency.

Method and system for rational frequency synthesis using a numerically

A digital single sideband modulator (10) includes a relatively complex CMOS NCO (14) that drives a relatively simple ECL frequency translator (30). The frequency translator (30) outputs a digital signal that is converted to analog by a D/A (44) and then filtered in a bandpass filter (46) having a pass band including a frequency of twice the NCO's clock frequency. The NCO (14) generates a modulated intermediate frequency NCO signal having quadrature components. The frequency translator (30) multiplies real and imaginary components of the NCO signal by real and imaginary components of digitized SIN, COS sampling functions (48, 50). The resulting products are added together. The adding operation is performed by a multiplexer (32), whose selection input is driven at twice the carrier frequency, and the multiplying operations are performed by a selective negation circuit (34), that is driven at the carrier frequency.

Digital single sideband modulator and method

A digital pulse shaping and phase modulation network is used for reducing out-of-band spectral energy. This network is used in conjunction with a NCO (numerically controlled oscillator) which includes a linear phase input port. This circuit converts rectangular data pulses into a user programmed shape. The shape pulses are then modulated onto the carrier via the linear phase port. Depending on the preprogrammed pulse shape, the out-of-band spectral energy is significantly reduced.

Programmable digital pulse shaping phase modulator

There is described an apparatus and method for decoding signals produced by a communication system employing cascading or concatenation of error control codes that contain, for example, short memory convolution codes. A novel inner decoder and method is described which is a modified Viterbi decoder that generates soft decisions by using a subset of the operations performed by a normal, hard decision, Viterbi decoder. Results of simulation tests show that the performance of the novel decoder provides a bit error rate performance that matches the theoretical bit error rate for the various signal to noise ratios, which performance is better than decoders previously available. Several implementations are described and compared.

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Chandler, AZ, United States of America

Richard A Bienz