Itt Manufacturing Enterprises, Inc.

Itt Corporation

Lawrence J Doyle

Dennis D McCrady

Howard Scott Forstrom

Peter Cummiskey

Marvin A Epstein

Gene L Cangiani

Pradipta Shome

The position of a non-cooperating emitter is determined by detecting a signal from the emitter at three or more receiver communication devices positioned at different locations. The receiver communication devices determine respective detection times of the emitted signal in respective local time reference frames. To establish a common time reference frame for the emitted signal detections, each receiver communication device exchanges time synchronization signals with a reference communication device. Since any of the receiver communication devices and the reference communication device may be mobile, the signal exchange allows each receiver communication device to accurately determine the signal propagation time between itself and the reference communication device and factor the signal propagation time into an accurate adjustment of the local time reference frame. Using trilateration, the position of the emitter is determined from known positions of the receiver communication devices and the emitted signal detection times from the receiver communication devices.

System for determining position of an emitter

A position location communication system determines the position of a mobile master radio using a round-trip messaging scheme in which the time of arrive (TOA) of ranging signals is accurately determined to yield the range estimates required to calculate the position of the mobile radio. The master radio transmits ranging signals to plural reference radios which respond by transmitting reply ranging signals. Upon reception of the reply ranging signal, the master radio determines the range to the reference radio from the signal propagation time. Any combination of fixed or mobile radios having known positions can be used as the reference radios for another mobile radio in the system. Individual radios do not need to be synchronized to a common time reference, thereby eliminating the need for highly accurate system clocks. Errors in TOA estimates are minimized by performing internal delay calibration, Doppler compensation, leading-edge-of-the-signal curve fitting and frequency diversity techniques.

Method and apparatus for determining the position of a mobile communication device

A new signal format that allows sharing of spectrum with CDMA signals with a minimum amount of mutual interference and a maximum amount of processing gain. The method including the step of coherently frequency hopping a narrow band signal adapted to minimize interference with a main lobe of the CDMA code over the allocated bandwidth. A particular application of this provides a method for enabling a global positioning device adapted to receive an allocated bandwidth to directly acquire a to P(Y) code when an associated C/A signal is effectively jammed.

Hop overlay signal structure for including additional signaling channels in code division multiple access communication and navigation systems

A spread spectrum position location communication system determines the position of a mobile master radio using a round-trip messaging scheme in which the time of arrive (TOA) of ranging messages is accurately determined to yield the range estimates required to calculate the position of the mobile radio via trilateration. The master radio transmits outbound ranging messages to plural reference radios which respond by transmitting reply ranging messages. Upon reception of the reply ranging message, the master radio determines the range to the reference radio from the signal propagation time calculated by subtracting the far-end turn around time from the round-trip elapsed time. Any combination of fixed or mobile radios of known positions can be used as the reference radios for another mobile radio in the system, thereby providing adaptability under varying transmission conditions. The individual radios do not need to be synchronized to a common time reference, thereby eliminating the need for highly accurate system clocks. By performing internal delay calibration, errors caused by difficult-to-predict internal transmitter and receiver delay variations can be minimized. Leading-edge-of-the-signal curve fitting and frequency diversity techniques minimize the effects of multipath interference on TOA estimates.

Methods and apparatus for determining the time of arrival of a signal

Method and apparatus for determining the position of a mobile communication device using low accuracy clocks

A system and a method is disclosed for on board prediction of a trajectory for satellites, which can be implemented on a computer with a limited number of bits. The system includes a compact force model that approximate the forces that the satellite encounters in an earth orbit. The compact force model includes a two body force component, a non-spherical earth gravitational force component, a solar radiation pressure component and a lunar-solar perturbation force component. An adder is coupled to the force model for combining the force components to produce an equation of motion approximating the acceleration of the satellite. An integrator is included for integrating the equation of motion approximating the acceleration of said satellite to produce an equation of motion approximating the displacement of the satellite, wherein the equation of motion approximating the displacement of the satellite is a reference trajectory.

System of on board prediction of trajectories for autonomous navigation

A system and method for maintaining a precise time standard among a system of orbiting satellites is disclosed. In an illustrative embodiment, atomic clock data is circulated among the satellites via RF crosslinks. Each satellite uses the received data as input to a Kalman process which acts to minimize the mean squared error among the satellite clocks to form a set of 'ensemble clocks'. The resulting ensemble clock values are then transmitted to an earth station where an offset between the ensemble clocks and Universal Time is computed. The offset is transmitted from the earth station to the satellites where it is used by the satellites to lock their on-board clocks to Universal Time, thereby creating a corrected system time. The corrected system time is transmitted, via RF crosslinks, to satellites not having operational on-board clocks. The satellites without atomic clocks employ phase locked loops to anchor their clocks to the corrected system time as it is received over the crosslinks.

Growing community of inventors

Hazlet, NJ, United States of America

Lawrence J Doyle