Roke Manor Research Limited

Robert John Weedon

Timothy John Quilter

Keith Roland Stribley

Bryan Stephen Rickett

James Joseph Fisher

Christopher Nigel Smith

David Sherry

Adam Alexander Baker

Simon John Atkinson

Philip Edward Roy Galloway

A multilateration system and method includes a plurality of receiver stations for receiving signals from an aircraft, and a controller that derives the position of the aircraft by applying a multilateration process to outputs from the receiver stations. For this purpose, the controller determines the altitude of the aircraft and selects a multilateration process that is to be used for position determination, based on the determined altitude.

Multilateration system and method

In a multilateration system receivers are grouped into two groups. The first group is used to determine a position of a signal source, for example, an aircraft equipped with a SAR transponder. From the determined position, predicted time of arrival values are produced for the second group receivers. These are compared with the actual time of arrival values for the signals arriving at the second group receivers. A difference is determined and then the variation of that difference is determined as the aircraft travels in its track. The groupings are then varied and further variations determined. When the minimum variation is determined an alert is given that the second group has a receiver which is operating with a larger than desirable group time delay.

Apparatus and method for determining receiver performance in a multilateration system

A method is provided for controlling a clock for use in a frequency source. In the method a time bias is determined by determining the Accumulated Doppler Range of a signal source at different time intervals. The drift of a local clock is determined by determining the difference between the different time intervals and the clock may then be corrected. Apparatus is also provided and the invention has particular application to a multilateration system.

Method and apparatus for controlling a frequency source

A method of determining the position of a target comprising the steps of: providing a transmitter or a plurality of transmitters to transmit a signal to the target, providing a receiver or a plurality of receivers to receive signals reflected from said target. Determining the time of arrival information of said reflected signal at the or each receiver; using information pertaining to the position of the or each receiver and/or the or each transmitter and with the information obtained determining the target position. Preferably the signal includes a modulated or coded portion unique to the transmitter; and said signal portion is associated with the or each particular transmitter by virtue of said signal portion. The signal maybe a mobile phone transmission, DAB, digital TV, digital Radio or digital satellite transmissions.

Method of determining the position of a target using transmitters of opportunity

Method and apparatus for providing accurately synchronized timing signals at mutually distant locations employs a GPS or similar receiver at each location. These receivers are interconnected by a communications network, and exchange data over the network to agree a common timing reference.

Time and frequency synchronizations of equipment at different locations

A time interval measurement system for the timing between events occurring at two spaced apart locations comprising at each location a dual frequency Global Positioning System (GPS) receiver having operatively associated with it a GPS antenna, wherein both the GPS receiver and the antenna are dual frequency (L , L ) and the former is capable of both Coarse Acquisition (C/A) Code and carrier phase measurements, an accurate frequency reference source giving local time, a data-logger for logging the GPS data, a Time Interval Counter (TIC) means is used to measure the time of a local event relative to the local time and further comprising a central processor system (CPS) and a communication system via which the logged GPS data and time interval data are received at the CPS from each location, the CPS being arranged to derive a time-offset figure, in accordance with a predetermined algorithm which is indicative of the difference between times as measured in dependence upon the frequency reference sources at the two locations.

Timing systems

A time offset measurement system for the timing of events at spaced apart locations comprising at each location, a dual frequency Global Positioning System (GPS) receiver having operatively associated with it a GPS antenna, wherein both the GPS receiver and the antenna are dual frequency (L , L ), and the former is capable of both Coarse Acquisition (C/A) Code and carrier phase measurements, a frequency reference source giving local time, a data-logger for logging GPS data, a Time Interval Counter (TIC) used to measure the time of a local event as defined by the frequency reference source relative to time as determined based on on GPS data and further comprising a central processor system (CPS), and a communication system via which the logged GPS data and time interval data, are received at the CPS from each location, the CPS being arranged to derive in accordance with a predetermined algorithm, for each pair of sites a primary time-offset figure based on a direct signal path between the sites, and a secondary time-offset figure based on at least one indirect signal path between the sites, wherein confidence that correct system operation is obtained is indicated based upon correspondence between the primary and secondary time-offset figures.

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Romsey, United Kingdom

Robert John Weedon