The Secretary of State for Defence

Parthus (uk) Limited

Other

Qinetiq Limited

The Secretary of State for Defence in Her Britannic Majesty's Government of the United Kingdom of Great Britain and Northern Ireland

Symmetricom, Inc.

Anthony Richard Pratt

John Ivor Rewbridge Owen

John I R Owen

Christopher James Mather

John Ivor Owen

A method of tracking a plurality of signals from a single satellite comprises receiving a first signal transmitted by a satellite; receiving at least a second signal transmitted by the same satellite; applying a pre-filtering process to determine the cumulative in-phase and quadrature components of the first, second signals, and optionally any further signals; and applying a filtering process to the cumulated in-phase and quadrature components of the first and at least second signals to determine a range and range rate of the satellite; wherein the filtering process comprises applying a Kalman filter. The method results in a determination of the range and range rate from a single satellite with improved signal to noise ratio. The range and range rate so determined may be used, with data from other satellites, to produce a navigational position. The method may be used with each such satellite used in producing the navigational position.

Method and system for satellite signal processing

Techniques for processing a navigation signal are disclosed. In one particular embodiment, the techniques may be realized as a method processing a navigation signal, the method comprising the steps of: receiving, using a receiver, the navigation signal, the navigation signal comprising a carrier signal, a data signal and at least one ranging code modulated by at least one stepped subcarrier modulation signal, the at least one stepped subcarrier modulation signal comprising a number, m, of amplitude levels, where m&#x3e;2, and wherein the amplitude levels have respective magnitudes and durations arranged to influence the power spectrum of the navigation signal is constrained in a predetermined manner, processing the navigation signal to recover the modulated at least one ranging code; and processing the recovered at least one modulated ranging code to recover at least one demodulated ranging code.

Modulation signals for a satellite navigation system

A method of controlling a power spectrum of a navigation transmission signal in a navigation system is provided. The navigation transmission signal comprising a carrier signal, a navigation ranging signal, a data signal, and at least one subcarrier modulation signal. The method comprising modulating the navigation ranging signal with the at least one subcarrier modulation signal, wherein the at least one subcarrier modulation signal comprises a number, m, of amplitude levels, where m&#x3e;2, to produce a modulated ranging signal. The amplitude levels having respective magnitudes and durations arranged to influence the power spectrum of the navigation signal in a predetermined manner. Modulating the carrier with the modulated ranging signal and the data signal to generate the navigation signal.

Techniques for controlling a power spectrum of a navigation transmission signal in a navigation system are disclosed. In one particular embodiment, the techniques may be realized as a method of controlling a power spectrum of a navigation transmission signal in a navigation system, the navigation transmission signal comprising a carrier signal, a ranging code, a data signal, and at least one stepped subcarrier modulation signal. The method may comprise modulating the canier signal by the at least one stepped subcarrier modulation signal, the data signal, and the ranging code to generate the navigation transmission ranging signal, wherein the at least one stepped subcarrier modulation signal may comprise a number, m, of amplitude levels, where m&#x3e;2. The amplitude levels may be arranged to constrain the power spectrum of the navigation transmission signal in a predetermined manner.

Embodiments of the present invention provide a method to produce a modulation signal comprising combining at least two modulation signals, for example, BOCs or derivatives thereof, having portions (chip or a number of chips) thereof with respective relative phases or states ({++,&#x2212;&#x2212;} and {+&#x2212;,&#x2212;+}) selected such that the average of a plurality of said portions at least reduces cross spectral terms of the composite complex spectrum of said at least two modulation signals.

Signals, system, method and apparatus

Embodiments of the present invention provide a method to produce a modulation signal comprising combining at least two modulation signals, for example, BOCs or derivatives thereof, having portions (chip or a number of chips) thereof with respective relative phases or states ({++, &#x2212;&#x2212;} and {+&#x2212;, &#x2212;+}) selected such that the average of a plurality of said portions at least reduces cross spectral terms of the composite complex spectrum of said at least two modulation signals.

In a mobile unit housing a two-way communications subsystem and a satellite positioning system (SPS) receiver subsystem, the communications subsystem includes a training signal generator for generating a training signal mimicing a positioning signal transmitted by a remote SPS transmitter. The training signal is frequency-coupled to a reference frequency source contained within and used by the communications subsystem, which source is, itself, stabilized by means of communication with a remote station, e.g. a base station in a cellular telephone system. In a training sequence, the training signal is activated and coupled into the SPS receiver subsystem, and a replica signal generator for generating a carrier replica signal for position-fixing purposes is controlled so as to bring the carrier replica signal into aliment with the training signal. Information representative of the control setting of the replica signal generator corresponding to such alignment is stored. Subsequently in a searching sequence, the training signal is deactivated and the replica signal generator is set to a setting based on the stored information for acquisition and processing of positioning signals from remote SPS transmitters.

Mobile communication apparatus

Positioning apparatus for use in a moving vehicle includes circuitry arranged to process signals received from GPS satellites, and to provide signals in response thereto from which the position of the apparatus can be calculated at a remote station. The apparatus provides, for each satellite in view, carrier frequency estimation signals, samples of the carrier signals and code tracking signals to a data transmission device, which modulates the signals onto a carrier prior to transmission to the remote station. A carrier loop reconstruction device and a location processor in the remote station cooperate to determine the location of the positioning apparatus. A memory device at the remote station may record the signals received from the vehicle over a period of time, for subsequent carrier loop reconstruction and location determination.

Positioning apparatus and method

Apparatus for receiving ranging signals (e.g. signals from Global Positioning System satellites) has a receiver coupled to a plurality of spaced antennas. The receiver includes a signal combiner which receives, from a processing circuit, signal components individually representative of a characteristic of the received ranging signals (e.g. signal-to-noise ratio) at a respective antenna and weights the said components to produce a range estimate of improved accuracy in difficult reception conditions. In one embodiment receiver includes a common i.f. channel which filters a combination signal representative of all the incoming signals in order substantially to maintain phase coherence between the incoming signals, yielding improvements in carrier phase measurement and discrimination.

Apparatus for receiving ranging signals

Positioning apparatus for use in a moving vehicle includes circuitry arranged to process signals received from GPS satellites, and to provide signals in response thereto from which the position of the apparatus can be calculated at a remote station. The apparatus provides, for each satellite in view, carrier frequency estimation signals, samples of the carrier signals and code tracking signals to a data transmission device, which modulates the signals onto a carrier prior to transmission to the remote station. A carrier loop reconstruction device and a location processor in the remote station co-operate to determine the location of the positioning apparatus. A memory device may record signals received over a period of time, from which mission replay may be performed.

A satellite-based positioning system includes at least one mobile station (,) and a terrestrial station (,), which may be a cellular telephone base station and is arranged to receive ephemeris data from each in-view positioning satellite. The ephemeris data is processed in a processor (,) to provide processed data which defines the satellite orbit in Cartesian form. Processed data is transmitted over a short message service channel to each mobile receiver (,), which includes also a positioning system receiver (,). The mobile receiver (,) is able to determine its position from the processed data and from signals received from positioning satellites with reduced processing, and thus reduced power consumption and/or time, than previous mobile receivers. The terrestrial station (,) may operate as a reference receiver which modifies the processed data to correct for errors in the ephemeris data and/or atmospheric propagation effects and/or the effects of selective availability.

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Rugby, United Kingdom

Anthony Richard Pratt