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| Fixed-frequency beam-steerable leaky-wave microstrip antenna |
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| Interconnect traffic tracking |
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| Mobile system and mobile management system |
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Reduction of time to first fix in an SATPS receiver
| Details |
Inventors: Loomis, Peter V. W.; Eschenbach, Ralph; Braisted, Paul; Lau, Chung;
Assignee: Trimble Navigation Ltd. (Sunnyvale, CA)
Primary Examiner: Issing; Gregory C.
Assistant Examiner:
Attorney, Agent or Firm: Schipper; John
A method for fast acquisition, in as little as 6-15 seconds, of signals from a satellite in a Satellite Positioning System (SATPS), such as GPS or GLONASS, that does not require permanent storage of satellite ephemeris information at an SATPS ground station. This SATPS signal acquisition method can be used whenever the "new" station initially powers up or has lost lock on one or more SATPS signals that must be (re)acquired. A reference SATPS station provides the new SATPS station with an estimated reference station location and ephemeris information for one or more identified SATPS satellites visible from the reference station. The new station receives and uses this information to establish carrier frequency ranges to search for the identified SATPS satellite, by limiting the search to a reduced frequency range based upon estimated Doppler shift of SATPS signals received from this satellite. The actual frequency shift may differ from the estimated Doppler shift, due in part to errors in a frequency source used by the new station. When a first SATPS satellite signal is acquired and locked onto by the new station, the error in the new station frequency source is estimated, and the frequency range for searching for an SATPS signal from another satellite is reduced. Acquisition of additional SATPS satellite signals occurs more quickly. This system also allows the use of less accurate timing sources for the new stations. A new station need not store ephemeris information for the SATPS satellites but may call upon and use the ephemeris information available at the reference station. |
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DETAILED DESCRIPTION The invention focuses on initial acquisition (at the time of power-up), reacquisition (after loss of lock) and identification of visible SATPS satellites by an SATPS station that includes an SATPS signal antenna and SATPS receiver/processor.
Receipt of differential SATPS signals from another already-operative SATPS (reference) station allows the "new" SATPS station that is searching for satellite lock to reduce the Time To First Fix by as much as an order of magnitude, allows use of less expensive timing sources, and allows receipt and storage by the new station of ephemerides and almanac data that will be needed later.
This allows quicker acquisition of the visible SATPS satellites upon (re) acquisition of satellite lock.
In one embodiment, the method includes the steps of: (1) receiving differential SATPS ("DSATPS") correction information (optional) and selected satellite ephemerides, almanac, ionosphere and/or time information from a nearby SATPS reference station, whose location coordinates are known with high accuracy, where the (optional) DSATPS information may include the pseudorange corrections and/or other relevant code phase or carrier phase attributes and satellite index of each SATPS satellite that is visible from the reference station (referred to as an SATPS "reference/visible" satellite); (2) determining the reference/visible satellites that are visible from the new SATPS station (referred to as an the "new station/visible" satellites); (3) establishing a selected number of one or more SATPS receiver/processor channels to receive and process SATPS signals from at least one reference/visible satellite; (4) stepping through the SATPS signal attributes for at least one reference/visible satellite to acquire and lock onto the SATPS signals from at least one of these SATPS satellites; (5) as soon as at least one SATPS satellite signal is acquired, narrowing the frequency tuning range of all the other tuning channels to a smaller frequency range, based upon an estimated frequency source error and Doppler shift frequency for at least one additional satellite; and (6) using this smaller frequency range to more quickly acquire and lock onto additional SATPS satellite signals, if needed
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Cell Phones 
