Method for the real-time determination of a time delay between stations in a radiolocation/radionavigation system
AssigneeCentre National D'Etudes Spatiales
InventorJean-Luc Issler
Life of this patent
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Abstract
According to the invention, each station emits a pseudo-noise code and slaves the time at which its code is retransmitted by the satellite to a reference. The difference between the times at which codes are received in a particular station then corresponds to the time difference between the stations. Each station accesses it directly in real time.
Claims5
Process for determining the time variation between several stations (Si), (Sj) in a radio-positioning-navigation system in real time, this system also comprising a satellite (G) equipped with a repeater, this process being characterized by the fact that it comprises the following operations:
- a) at least one pseudo-noise code (PNi) specific to each station (Si) is produced in the station (Si), the codes (PNi), (PNj) transmitted by two different stations (Si), (Sj) being orthogonal;
- b) the code (PNi) specific to each station (Si) is transmitted from this station at a transmission time (te)i identified with respect to a time reference (Hi) specific to this station (Si);
- c) the various codes (PNi) transmitted by the various stations (Si) are received in the satellite (G) and are retransmitted to the said stations (Si);
- d) each code retransmitted by the satellite (G) is received in each station (Si) and the reception time (tr)i of the (PNi) code specific to the station (Si) is determined with respect to the time reference (Hi) of the station (Si);
- e) in each station (Si), the transmission time (te)i of the code specific to this station is shifted until the half-sum ((te)i+(tr)i)/2 of the transmission time (te)i and reception time (tr)i of the code (PNi) specific to the station (Si) or the quantity (te)i-D/c or (tr)i-D/c, where D is the known distance between this station and the satellite and c is the speed of light, coincides with a reference time (tref)i defined with respect to the time reference (Hi) of this station (Si);
- f) in an arbitrary station (Si), the reception time (tr)j of the code originating from another station (Sj) is measured;
- g) in this station (Si), the difference between the reception time (tr)i of the code (PNi) specific to this station (Si), and the reception time (tr)ji of the code (PNj) specific to the said other station (Sj) is then determined, this difference ((tr)i-(tr)ji) then giving the difference (.DELTA.Tij) between the time references (Hi), (Hj) of the station concerned (Si) and the other station (Sj), in real time.
Dependencies are inferred from the claim text.