Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
  • G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
  • G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
  • G01S19/13—Receivers
  • G01S19/24—Acquisition or tracking or demodulation of signals transmitted by the system
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
  • G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
  • G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
  • G01S19/13—Receivers
  • G01S19/23—Testing, monitoring, correcting or calibrating of receiver elements
  • G01S19/235—Calibration of receiver components
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
  • G01S5/00—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
  • G01S5/02—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using radio waves
  • G01S5/04—Position of source determined by a plurality of spaced direction-finders
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
  • H04B1/69—Spread spectrum techniques
  • H04B1/707—Spread spectrum techniques using direct sequence modulation
  • H04B1/709—Correlator structure
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
  • G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
  • G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
  • G01S19/13—Receivers
  • G01S19/35—Constructional details or hardware or software details of the signal processing chain

Definitions

• the field of the invention is that of GNSS (Global Navigation Satellite System) satellite positioning receivers.
• the aim of the invention is more precisely to reduce the error that can affect the position information delivered by such a receiver by evaluating the propagation time of the satellite signals within the receiver, and in particular within the channel filter of a receiver. such receiver.
• the invention is particularly applicable to receivers of signals transmitted by GPS ("Global Positioning System"), Glonass, Galileo and other similar satellite positioning systems. BACKGROUND OF THE INVENTION
• a satellite positioning receiver uses signals from a plurality of satellites orbiting the earth.
• Each of the satellites transmits on one or more given frequencies a phase-modulated signal by the combination of a pseudo-random spreading code and a navigation message containing, among other things, the ephemerides of the satellites (i.e. defining their orbit and their variations as a function of time).
• Satellite positioning consists of measuring the propagation time of the radiofrequency signal emitted by each of the satellites. These propagation times multiplied by the speed of transmission of the signal give the satellite-receiver distances (more known by those skilled in the art under the name of "pseudo-distances"). These associated with the position of the satellites calculated thanks to the ephemeris, make it possible to calculate the position of the receiver and the offset of its clock compared to those of the satellites.
• the difference in measured propagation times also includes that of the propagation times in the receiver which is not zero due to the processing of the two signals in two separate channels. Uncertainty about the difference in the delays related to the receiver, although limited to a few nanoseconds, is reflected after bi-frequency correction by location errors of several meters. The uncertainty in this difference in propagation time is related to the fact that these are not constant from one receiver to another, that they are temperature dependent and further affected by the aging of the receiver.
• GNSS GNSS
• This filter is an essential element for a radio receiver to greatly attenuate any out-of-band noise signals that can saturate this receiver.
• This filter is almost always a surface acoustic wave (FOS or SAW) filter because of its many advantages: selectivity, phase linearity, size, weight, etc.
• the position error of a GNSS receiver using SAW filters can be significantly reduced if one has a precise knowledge of their TP (nominal value, evolution in temperature and aging).
• the aim of the invention is to increase the accuracy of a GNSS receiver by improving knowledge of the propagation delay of the receiver channel filter.
• the invention proposes a receiver of a satellite positioning system, comprising:
• a channel filter comprising an input transducer and an output transducer, in which the propagation of a signal emitted by a satellite and received by the receiver takes place in a direct path corresponding to a direct crossing between the transducers of the receiver; input and output and along indirect paths corresponding to 2n + 1 times the direct path due to multiple reflections on the input and output transducers, n being an integer greater than or equal to 1;
• a tracking loop controlled by means of a control correlator centered on a correlation peak between a code spreading the signal emitted by the satellite and a local replica of said code generated by the receiver,
• a shift register configured to generate several local replicas of said spreading code offset from each other so as to cover a time window corresponding to twice the uncertainty on an estimate of the propagation time directly traversing the channel filter
• a second correlator offset from the driving correlator of a time corresponding to twice said estimate of the propagation time directly traversing the channel filter said second correlator being configured to perform the correlation of the spreading code of the signal transmitted by the satellite with said local replicas generated by the shift register and detecting a correlation peak, said correlation peak corresponding to the acquisition of the signal transmitted by the satellite subjected to propagation in the channel filter according to a triple indirect path.
• it furthermore comprises a computer configured to calculate a pseudo-distance to the satellite from the correlation peak of the driving correlator and a pseudo-distance to the satellite from the correlation peak of the second correlator, said calculator being furthermore configured to calculating the forward traversal time of the channel filter by halving the difference between said pseudo-distances.
• the driving correlator and the second correlator integrate the correlation results over an integration period, the duration of integration of the second correlator being greater than the integration time of the driving correlator.
• the invention relates to a method for determining the propagation time of a signal transmitted by a satellite in a receiver of a satellite tracking system, the receiver comprising:
• a channel filter comprising an input transducer and an output transducer, in which the propagation of a signal emitted by a satellite and received by the receiver takes place in a direct path corresponding to a direct crossing between the transducers of the receiver; input and output and along indirect paths corresponding to 2n + 1 times the direct path due to multiple reflections on the input and output transducers, n being an integer greater than or equal to 1;
• a tracking loop controlled by means of a control correlator centered on a correlation peak between a spreading code of the signal transmitted by the satellite and a local replica of said code generated by the receiver,
• correlation by means of a second correlator offset from the driving correlator by a time corresponding to twice said estimate of the propagation time through the channel filter, of the spreading code of the signal transmitted by the satellite with said local replicas generated by the shift register and detecting a correlation peak, said correlation peak corresponding to the acquisition of the signal transmitted by the satellite subjected to propagation in the channel filter according to a triple indirect path.
• FIG. 1 is a simplified diagram of a surface acoustic wave filter
• FIG. 2 illustrates the propagation of a signal along single and triple paths in a filter according to FIG. 1;
• FIG. 3 is a diagram illustrating a GNSS receiver according to the invention.
• the invention relates, according to its first aspect, to a GNSS satellite positioning receiver.
• a receiver conventionally comprises a channel filter, typically a SAW surface acoustic wave filter (of which reference will be made thereafter, by way of non-limiting example) which allows to selectively transmit an acoustic wave between two transducers T E , T s etched on a quartz substrate.
• the electrical-acoustic conversion and vice versa is obtained thanks to the localized piezoelectric effect at input and output transducers T E , T s .
• a signal E emitted by a satellite and received by the receiver propagates within the SAW filter according to a direct path T1 corresponding to a direct crossing between the input and output transducers T E , T s , to provide a signal of output S1.
• the signal E propagates along indirect paths corresponding to 2n + 1 times the direct path n being a upper integer or equal to 1.
• a triple path corresponding to the sum of the paths T1, T2 and T3 provides an output signal S3, the level of which is lower than that of the signal S1 of the direct path of a level typically of the order of 30 dB.
• the invention proposes to combine the temporal measurement capabilities of the GNSS signals with this defect of the signal formation SAW filters derived from indirect paths in order to determine their propagation time.
• the invention proposes more precisely once a satellite signal continued to determine the pseudo-distances of its single path and its triple path, and then to deduce the propagation delay of the SAW filter in making the difference of these pseudo-distances and dividing the result by two.
• the difference of these pseudo-distances corresponds effectively to the additional path traveled by the signal S3 of the triple path, ie T2 + T3 as represented in FIG.
• the waveform of the GNSS signals allows a measurement of their propagation times between the satellites that transmit them and the receiver that receives them.
• the carrier of a GNSS satellite signal spectrally spread by a pseudo-random bit sequence, can be detected provided that it correlates with a local signal at the same frequency and spread by the same sequence.
• the spreading sequence of the local signal must be synchronous with that of the received satellite signal.
• the position of the local signal code commonly called pseudodistance, is the image of the propagation time. Using the navigation message information of at least four satellites, the position of the receiver can be determined from these pseudo-distances.
• the GNSS receiver conventionally comprises, downstream of the SAW filter of the channel filter, a plurality of tracking channels each associated with a satellite, and in each channel a tracking loop controlled by means of a control correlator C1 centered on a correlation peak between a spreading code of the signal transmitted S S AT by the satellite and a local replica of said generated SRI code by means of a replica signal generator G1 integrated in the receiver.
• each tracking channel comprises three correlators, fed by a point replica of the spreading code ("Prompt” correlator), shifted in advance from D / 2 chip of the spreading code (correlator said " Early ”) and shifted by D / 2 chip late (correlator called” Late ").
• the code tracking loop continuously maintains the "Prompt” correlator on the correlation peak by slaving the generation of the code replica to the "zero" of the "Early” feature function less "Late”.
• the "Prompt" correlator is referred to as the steering correlator.
• the tracking loop of a channel thus makes it possible to continue the signal of the simple path and to deduce, by means of a computer C represented here as also responsible for controlling the tracking loop, the pseudorange at the satellite corresponding to its simple path in the SAW filter.
• the GNSS receiver during the tracking of the satellite signal (single path), the GNSS receiver according to the invention, via a channel allocator, positions a second channel at the same frequency as the tracking channel in order to find the signal of the triple trip.
• the GNSS receiver more precisely comprises a second replica generator G2 supplying a shift register RD configured to generate several local replicas of said spreading code shifted from each other so as to cover a time window corresponding to twice the time. uncertainty, typically of the order of +/- 10 ns, on an estimation of the propagation time through the channel filter.
• the GNSS receiver further comprises a second correlator C2 shifted from the driving correlator by a time corresponding to twice said estimate of the propagation time directly traversing the channel filter, said second correlator being configured to correlate the spreading code of the signal transmitted by the satellite with said local replicas generated by the shift register and to detect a correlation peak, said correlation peak corresponding to the acquisition of the signal transmitted by the satellite subjected to propagation in the channel filter in a triple indirect path.
• the time slots adjacent to the offset of the second correlator C2 (shifted from the driving correlator C1 by a time corresponding to an estimate of twice the propagation time through the direct traverse) are explored. These time slots covering twice the uncertainty on this estimate.
• the computer C is also configured to calculate the pseudo-distance to the satellite corresponding to its triple path in the SAW filter from the correlation peak of the second correlator C2.
• the calculator C is furthermore configured to calculate the forward traversal time of the channel filter by dividing by two the difference between the pseudo-distance to the satellite corresponding to its single path and the pseudo-distance to the satellite corresponding to its triple path. .
• the driving correlator C1 and the second correlator C2 integrate the correlation results over an integration period.
• the integration time of the second correlator is greater than the integration time of the driving correlator.
• the duration of integration of the second correlator is of the order of one second when that of the driving correlator is of the order of one millisecond.
• this measurement is to be performed for each of the GNSS bands used (L1, L2, L5 GPS, E1, E5, E5 in GALILEO).
• the invention thus makes it possible to carry out a satellite signal from one antenna to the other in a continuous manner.
• the tracking of the satellite signal can also be switched from one antenna to another, such a switch finding particular application for rotating carriers (rocket, missile for example).
• the invention is also advantageous in that the triple path measurement is done under conditions identical to those of the operational requirement (antenna connected, visibility of satellites ). It does not require any external measurement means, and also makes it possible to overcome the constraint of returning to the factory for periodic calibration.
• the invention also allows a continuous measurement in real time of the propagation time of the channel filter, thus enabling a real-time correction of the pseudo-distances measurements which are tainted with errors related to the uncertainty over time. of propagation within the channel filter.
• the continuous measurement makes it possible in particular to take into account the temperature drifts, for example when the receiver starts cold and then heats up.
• the real-time realization of the measurement makes it possible not to have to interrupt the reception of the GNSS signals.
• the invention is not limited to a GNSS receiver, but also extends to a method for determining the time of propagation of a signal transmitted by a satellite in a receiver of a satellite tracking system, the receiver comprising:
• a channel filter comprising an input transducer and an output transducer, in which the propagation of a signal emitted by a satellite and received by the receiver takes place in a direct path corresponding to a direct crossing between the transducers of the receiver; input and output and along indirect paths corresponding to 2n + 1 times the direct path due to multiple reflections on the input and output transducers, n being an integer greater than or equal to 1;
• a tracking loop controlled by means of a control correlator centered on a correlation peak between a spreading code of the signal transmitted by the satellite and a local replica (SRI) of said code generated by the receiver,
• correlation by means of a second correlator offset from the driving correlator by a time corresponding to twice said estimate of the propagation time through the channel filter, of the spreading code of the signal transmitted by the satellite with said local replicas generated by the shift register and detecting a correlation peak, said correlation peak corresponding to the acquisition of the signal transmitted by the satellite subjected to propagation in the channel filter according to a triple indirect path.
• This method typically implements a step of continuous calculation and in real time of a pseudo-distance to the satellite from the correlation peak of the driving correlator, a pseudo-distance to the satellite from the peak of correlating the second correlator, and the direct crossing time of the channel filter by dividing by two the difference between said pseudo-distances.
• It may furthermore comprise a step of correcting said pseudorange to the satellite calculated from the correlation peak of the driving correlator taking into account said propagation time through the channel filter.

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• Engineering & Computer Science (AREA)
• Radar, Positioning & Navigation (AREA)
• Remote Sensing (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Computer Networks & Wireless Communication (AREA)
• Signal Processing (AREA)
• Position Fixing By Use Of Radio Waves (AREA)

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• 2012
  • 2012-12-10 FR FR1203343A patent/FR2999298B1/fr active Active
• 2013
  • 2013-12-10 WO PCT/EP2013/076028 patent/WO2014090773A1/fr active Application Filing
  • 2013-12-10 EP EP13802628.1A patent/EP2929369A1/fr not_active Withdrawn
  • 2013-12-10 RU RU2015127825A patent/RU2015127825A/ru not_active Application Discontinuation
  • 2013-12-10 US US14/647,815 patent/US20150293204A1/en not_active Abandoned
  • 2013-12-10 CN CN201380060999.2A patent/CN104956238A/zh active Pending

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