Motorola Corporation

General Dynamics Decision Systems, Inc.

Roger Charles Hart

George Jeffrey Geier

Thomas Michael King

Joel Lloyd Gross

Yilin Zhao

Jeffrey Scott Moffett

Gaylin David Brenchley

George Arthur Schauer

Daniel Eric Bishop

A system for synchronizing a clock includes a phase-locked loop (PLL) circuit that generates or receives ( ) timing errors that are based on timing information from multiple timing sources. Gain blocks ( ) weight ( ) the timing errors, which are then combined ( ) into a loop time error. A loop integrator ( ) integrates ( ) the loop time error to produce an input used to adjust ( ) an oscillator frequency. A corresponding oscillator clock signal is fed back ( ) to one or more phase detectors ( ), which receive ( ) timing reference signals and generate timing errors. When a timing errors indicates that a problem exists with a timing source, the impact of the problematic timing source is reduced ( ), or oscillator frequency adjustments are suspended ( ). When used on a satellite ( ), at least one of the timing errors can be based on times of transmit and times of arrival of time messages exchanged between the satellite and its neighbors ( ).

Apparatus and method for synchronizing a clock using a phase-locked loop circuit

A method of determining the position of a satellite in a near geosynchronous orbit includes receiving at least one main lobe signal from an antenna on a first GPS satellite. A GPS signal, including GPS time and Doppler, is received from a pseudolite positioned on the Earth and an approximate position of each of a plurality of second GPS satellites is determined from an onboard almanac. Side lobe signals and accompanying noise are received from antennas on the plurality of second GPS satellites. The GPS signal and known sequential data bits are used for sorting or integrating the side lobe signals from the accompanying noise and the position of the satellite in a near geosynchronous orbit is determined using the one or more main lobe signals and the sorted side lobe signals.

Method and apparatus for accurately determining the position of satellites in geosynchronous orbits

A cellular network protocol which minimizes the required data flow between the cellular infrastructure and each mobile handset supporting a GPS based positioning capability is taught. Four specific innovations are introduced which together minimize the number of bits required to be transferred to each handset: a method for reducing or removing the requirement for GPS ephemeris updates to each mobile; a method for compression of the differential correction broadcast message; a method for controlling the rate at which the network updates each handset's ephemeris based on an ephemeris age limit; and, finally, a method which each mobile can use to determine when an ephemeris update is needed, based on an accuracy prediction and a threshold which is unique to each mobile.

Method and apparatus for assisted GPS protocol

A method and apparatus for maintaining the integrity of spacecraft based time and position using GPS (11) is disclosed. A GPS receiver is provided with a Receiver Autonomous Integrity Monitor (RAIM) processor (12) and a Kalman filter (14). GPS signals are received from at least four GPS satellites and processed in the GPS receiver to provide time and position information. Periodically, an extended fault vector is formed in the Kalman filter with propagated open-loop position and velocity measurements. The extended fault vector is used to isolate and remove failing GPS satellites.

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Gilbert, AZ, United States of America

Roger Charles Hart