Navsys Corporation

Litton Systems, Inc.

Teledesic LLC

Alison K Brown

Mark Alan Sturza

John G Mark

James R Stuart

Anthony Robert Matthews

Edward F Tuck

Douglas Gene Lockie

David Palmer Patterson

Moshe L Liron

Vilnis G Grencions

Asu Ram Jha

Amir H Matini

Peter K Brown

John D Norgard

Donald A Ashford

H Beat Wackernagel, Deceased

A digital GPS receiver includes electronics to detect the presence of multipath GPS signals, determine the direction from which they are received at a multi-element GPS phased array antenna, adaptively generate an antenna pattern to provide gain in the direction of the desired GPS satellite signal, and to apply nulls in the direction of the detected GPS multipath signals. This adaptively-generated antenna pattern is applied to the signals received at the elements of the GPS phased array antenna to provide a composite signal to each of the processing channels of the digital GPS receiver, optimized for the particular GPS satellite being tracked by a corresponding channel. The undesirable multipath GPS signals are thereby excised from the inputs to the processing channels of the digital GPS receiver, and the desired direct signal is reinforced, thus enabling tracking loops within the digital GPS receiver to make highly accurate observations of the code and carrier phase using conventional signal processing techniques.

Apparatus and method for minimizing multipath signal errors during tracking of GPS satellite signals

A miniature phased array antenna system employs a substrate having a high dielectric constant. A plurality of antenna elements are located on a surface of the substrate, and a superstrate having a high dielectric constant covers the antenna elements. The dielectric constant, thickness, and shape of the superstrate enable it to act as a dielectric lens for controlling the phase relationship of a signal received by the antenna elements. The design of the superstrate dielectric lens permits a reduction in the physical spacing between the antenna elements while maintaining spatial diversity in phase between signals arriving from different directions. Thus, the antenna array may be significantly smaller than conventional phased array antennas while maintaining a similar phase relationship to that achieved using conventional phased array antennas. Electronic circuitry coupled to each of the plurality of antenna elements applies complex weights to received signals prior to a summation thereof in order to reconstruct a desired signal and to deconstruct an undesired signal. SAW filters employed in the electronic circuitry are temperature controlled to maintain group-delay and phase-offset stability.

Miniature phased array antenna system

The Satellite Communication System disclosed in the specification is a dynamic constellation (C) of satellites (S). The present invention is capable of offering continuous voice, data and video service to customers across the globe on the land, on the sea, or in the air. The preferred embodiment of the invention comprises a low Earth orbit satellite system that includes 40 spacecraft (S) traveling in each of 21 orbital planes at an altitude of 700 km (435 miles). This relatively large number of satellites employed by the preferred embodiment was selected to provide continuous coverage of the Earth's surface at a high minimum mask angle (1230a) of forty degrees. Each of the individual 840 spacecraft (S) functions as an independent sovereign switch of equal rank which knows the position of its neighbors, and independently handles traffic without ground control. The satellites (S) are capable of transporting calls to millions of customers using portable (P), mobile (M) and fixed (F) residential and business terminals, and gateways (G) to public phone networks. The constellation uses the 20 and 30 GHz frequency bands for communications between Earth and the constellation (C), and the 60 GHz band for communicating among the satellites (S). The present invention is designed to support in excess of 2,000,000 simultaneous connections, representing over 20,000,000 users at typical business usage levels, and over 350 billion minutes of use per year. Only a system such as the preferred embodiment, which utilizes 840 satellites at a preferred minimum mask angle of forty degrees, can accomplish these challenging objectives.

Satellite communication system

A low cost tracking system employing satellites of the global positioning system (GPS) is suitable for applications involving radiosondes, sonobuoys, and other objects. The tracking system includes a sensor mounted on each object which digitally samples the GPS satellite signals and records them in a data buffer. The digital samples are then transmitted, at a rate lower than that at which the GPS satellite signals were sampled, over a data telemetry link, interleaved with other telemetry data from the object. The GPS data is processed in a data processing workstation where the position and velocity of the sensor, at the time the data was sampled, is computed. The data buffer in the sensor is periodically refreshed, and the workstation periodically computes the new position and velocity of the sensor. Differential corrections are also provided at the workstation to aid in signal acquisition and to increase the precision of the position fix.

GPS tracking system

A GPS precision approach and landing system for aircraft employs a fixed ground facility and a single satellite navigation receiver on board the aircraft. The fixed ground facility includes a reference receiver that measures differential corrections to the satellite code and carrier measurements and a pseudolite that is employed to transmit these corrections to a broadband GPS receiver on board the aircraft and to provide an additional code and carrier measurement to assist in the navigation solution. The pseudolite signal is broadcast at a frequency offset from the L1 GPS frequency in order to prevent interference with the satellite navigation system. The broadband GPS receiver on board the aircraft is capable of making phase coherent measurements from the GPS satellites, the pseudolite signal, and the GLONASS satellites. These phase coherent measurements are combined to form a precise differential carrier ranging (DCR) solution that is used to provide three-dimensional position guidance of the aircraft throughout a precision approach and landing procedure.

GPS precision approach and landing system for aircraft

A tracking system employing global positioning system (GPS) satellites provides extremely accurate position, velocity, and time information for vehicles or any other animate or inanimate object within any mobile radio communication system or information system, including those operating in high rise urban areas. The tracking system includes a sensor mounted on each object, a communication link, a workstation, and a GPS reference receiver. The sensor operates autonomously following initialization by an external network management facility to sequence through the visible GPS satellites, making pseudo range and delta range or time difference and frequency difference measurements. No navigation functions are performed by the sensor, thereby permitting significant reductions in the cost thereof. The raw satellite measurements, with relevant timing and status information, are provided to the communication link to be relayed periodically back to the workstation. Differential corrections may also be provided at the workstation to increase the accuracy of the object location determination. In normal operation, three satellite measurements are required to compute the location of the object, but for a short time period a minimum of two satellite measurements are acceptable with time, altitude, and map aiding information being provided by the workstation.

Vehicle tracking system employing global positioning system (GPS)

A codeless digital method and apparatus for obtaining measured phase from a plurality of L2 signal transmissions. An intermediate frequency signal is derived by mixing the L2 transmissions with a local oscillator. That signal is hardlimited and employed to terminate the count of a divide-by-32 counter that is clocked by the local oscillator signal and initiated by a signal in synchronization therewith whose frequency is a fraction of the local oscillator. The state of the counter is applied to a four bit latch. The state of the latch, which effectively discards the most significant bit of the count, provides the measured phase of the L2 transmissions from which position can be obtained by reference to the satellite phase and delta range values derived therefrom.

Digital system for codeless phase measurement

A circuit is shown which utilizes signals transmitted from global positioning system satellites to create change in phase signals. The change in phase signals are measured over a predetermined time interval, one second, and stored. The stored signals are applied to a Kalman filter and back to the storage unit so that each one second time interval includes the information from all previous time intervals. This accumulated information is referred to as accumulated Delta-Range information which permits a more rapid determination of position by the circuit.

Enhanced global positioning system Delta-Range processing

The use of a high speed moving average filter is shown to filter high speed errors, including white noise in angle and quantization errors, from the output data of a ring laser gyro while it is being tested. The filtered data permits investigation of the lower speed, random walk in angle error of the gyro being tested. For best results, several moving average filters are connected in series.

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Monument, CO, United States of America

Alison K Brown