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公开(公告)号：EP2002279A1
公开(公告)日：2008-12-17
申请号：EP07732103.2
申请日：2007-03-22
申请人： QinetiQ Limited
IPC分类号： G01S5/06
摘要： A method of compensating for or correcting satellite ephemeris error involves measuring time difference of arrival (TDOA) and frequency difference of arrival (FDOA) for signal replicas received via two satellites (34, 46) from calibration transmitters (42a to 42d) at different geographical locations. An initial satellite ephemeris consisting of position and velocity vectors is used to calculate ephemeris changes yielding estimated TDOA and FDOA values providing a best fit to measured TDOA and FDOA values. This provides estimated changes required to compensate for or to correct errors in the initial satellite ephemeris. The method may be iterated to deal with large ephemeris changes: i.e. the changes obtained in one iteration may be used to correct ephemeris for use as a new initial ephemeris in a following iteration. The method may be used to correct ephemeris errors in one or both satellites, if so a greater number of calibration transmitters EphemCal 1 to EphemCal 10 may be used.
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公开(公告)号：EP1204882A1
公开(公告)日：2002-05-15
申请号：EP00949742.1
申请日：2000-07-31
IPC分类号： G01S1/04
CPC分类号： G01S5/02 , G01S1/026 , G01S1/045 , G01S5/0009 , G01S5/06
摘要： A method of determining the location of an unknown source (10) transmitting a signal to satellite relays (14 and 16) comprises receiving replicas of the signal from the relays at receivers (18). The receivers (18) also transmit and receive reference signals via respective relays (14 and 16). All signals are downconverted, digitised and correlated with one another in pairs using a correlation function including a term which compensates for time varying differential frequency offset (DFO). Compensation for time varying differential time offset or time dilation is achieved by replicating or adding to signal samples and applying phase corrections. This procedure enables a correlation maximum and associated measurement results to be obtained despite the effects of relay satellite motion which mitigate against this. Results are used in a prior art geometrical technique to locate the unknown transmitter.
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4.发明公开
公开(公告)号：EP1299744A1
公开(公告)日：2003-04-09
申请号：EP02706950.9
申请日：2002-03-18
申请人： Qinetiq Limited
发明人： RIDEOUT, Robert, Martin , EDMONDS, Paul, Richard , DUCK, Simon, Robert , HAWORTH, David, Patrick , GRIFFIN, Christopher
IPC分类号： G01S5/06
摘要： A method of locating the source of an unknown signal of varying frequency received by receive antennas (16, 18) via relay satellites (12, 14) involves downconversion of received signals to a first intermediate frequency (IF) and band-limiting the downconverted signals. The band-limited signals are constrained to lie within a prearranged acquisition signal bandwidth by adjustment of local oscillator (LO) downconversion frequency to counteract frequency change in the unknown signal. Downconverted signals are offset in time relative to one another using trial values of differential time offset and their correlation is determined for each trial value to provide actual time offset. Compensation is provided for change in correlation phase angle, which results from signals being downconverted experiencing different LO frequencies during the time interval of the trial offset.
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