EP2929369A1 - Method and device for determining the propagation time of a surface acoustic wave filter - Google Patents

Method and device for determining the propagation time of a surface acoustic wave filter

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Publication number
EP2929369A1
EP2929369A1 EP13802628.1A EP13802628A EP2929369A1 EP 2929369 A1 EP2929369 A1 EP 2929369A1 EP 13802628 A EP13802628 A EP 13802628A EP 2929369 A1 EP2929369 A1 EP 2929369A1
Authority
EP
European Patent Office
Prior art keywords
satellite
correlator
channel filter
receiver
correlation peak
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP13802628.1A
Other languages
German (de)
French (fr)
Inventor
Francis Chaminadas
Jean-Christophe Le Liboux
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Safran Electronics and Defense SAS
Original Assignee
Sagem Defense Securite SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Sagem Defense Securite SA filed Critical Sagem Defense Securite SA
Publication of EP2929369A1 publication Critical patent/EP2929369A1/en
Withdrawn legal-status Critical Current

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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)

Abstract

The invention relates to a receiver of a system for positioning by satellite, including: a channel filter (SAW) in which a signal transmitted by satellite and received by the receiver is propagated along a direct path and indirect paths in an odd order; upstream from the channel filter, a tracking loop being controlled by means of a control correlator (C1), the receiver being characterized in that it comprises: an offset register (RD) configured to generate a plurality of local replicas (SR2) of said code, which are offset from one another such as to cover a time window corresponding to twice the uncertainty on an estimate of a propagation time when passing directly through the channel filter, a second correlator (C2) offset relative to the control correlator by a time corresponding to twice said propagation time estimate when passing directly through the channel filter, said second correlator being configured to correlate the code for spreading the signal transmitted by the satellite with said local replicas generated by the offset register, and to detect a correlation peak corresponding to the acquisition of the signal transmitted by the satellite and propagated in the channel filter along a triple indirect path.

Description

PROCEDE ET DISPOSITIF DE DETERMINATION DU TEMPS DE PROPAGATION D'UN FILTRE A ONDES ACOUSTIQUES DE SURFACE  METHOD AND DEVICE FOR DETERMINING THE TIME OF PROPAGATION OF A SURFACE ACOUSTIC WAVE FILTER
DOMAINE DE L'INVENTION FIELD OF THE INVENTION
Le domaine de l'invention est celui des récepteurs de positionnement par satellites GNSS (« Global Navigation Satellite System »). L'invention vise plus précisément à réduire l'erreur pouvant affecter l'information de position délivrée par un tel récepteur en venant évaluer le temps de propagation des signaux satellite au sein du récepteur, et en particulier au sein du filtre de canal d'un tel récepteur.  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.
L'invention est notamment applicable aux récepteurs des signaux transmis par les systèmes GPS (« Global Positioning System »), Glonass, Galileo et autres systèmes analogues de positionnement par satellites. ARRIERE PLAN DE L'INVENTION  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
Un récepteur de positionnement par satellites utilise les signaux émis par une pluralité de satellites en orbite autour de la terre.  A satellite positioning receiver uses signals from a plurality of satellites orbiting the earth.
C'est notamment au travers d'une pluralité de canaux, chacun associé à un satellite que la poursuite d'un satellite (poursuite d'un signal d'un satellite) va être mise en place.  It is in particular through a plurality of channels, each associated with a satellite that the pursuit of a satellite (tracking a signal from a satellite) will be put in place.
Chacun des satellites émet sur une ou plusieurs fréquences données un signal modulé en phase par la combinaison d'un code d'étalement pseudoaléatoire et d'un message de navigation contenant entre autres les éphémérides des satellites (c'est-à-dire les éléments définissant leur orbite et leurs variations en fonction du temps).  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).
Le positionnement par satellites consiste à mesurer le temps de propagation du signal radiofréquence émis par chacun des satellites. Ces temps de propagation multipliés par la vitesse de transmission du signal donnent les distances satellite-récepteur (plus connues par l'homme du métier sous le nom de «pseudo-distances»). Celles-ci associées à la position des satellites calculée grâce aux éphémérides, permettent de calculer la position du récepteur et le décalage de son horloge par rapport à celles des satellites. 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.
La vitesse de propagation du signal radiofréquence n'étant pas constante tout le long du trajet parcouru, en particulier dans l'ionosphère, les distances calculées sont faussées en raison de l'allongement du temps de propagation. Pour réduire sensiblement les erreurs affectant les temps de propagation, une correction appelée bi-fréquence doit être effectuée. Celle-ci met à profit la différence des temps de propagation de deux signaux émis par chaque satellite dans deux bandes de fréquence différentes.  Since the speed of propagation of the radiofrequency signal is not constant all along the path traveled, in particular in the ionosphere, the calculated distances are distorted due to the extension of the propagation time. To substantially reduce errors affecting propagation times, a correction called dual frequency must be performed. This takes advantage of the difference in the delay of two signals emitted by each satellite in two different frequency bands.
La différence des temps de propagation mesurés comprend aussi celle des temps de propagation dans le récepteur qui n'est pas nulle en raison du traitement des deux signaux dans deux voies séparées. L'incertitude sur la différence des temps de propagation liés au récepteur, bien que limitée à quelques nanosecondes, se traduit après correction bi-fréquence par des erreurs de localisation de plusieurs mètres. L'incertitude sur cette différence des temps de propagation est liée au fait que ceux-ci ne sont pas constants d'un récepteur à un autre, qu'ils sont dépendants de la température et en outre affectés par le vieillissement du récepteur.  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.
Le contributeur prépondérant au temps de propagation d'un récepteur The most important contributor to the delay of a receiver
GNSS, et donc à l'incertitude sur la différence des temps de propagation, est le filtre de canal. Il s'agit d'un élément indispensable à un récepteur radio pour atténuer fortement tous les signaux parasites hors bande pouvant saturer ce récepteur. Ce filtre est presque toujours un filtre à ondes acoustiques de surface (FOS ou SAW pour « Surface Acoustic Waves ») en raison de ses nombreux avantages : sélectivité, linéarité de phase, encombrement, poids, etc. GNSS, and therefore the uncertainty about the difference in propagation time, is the channel filter. This 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.
Après correction bi-fréquence, l'erreur de position d'un récepteur GNSS utilisant des filtres SAW, peut être significativement réduite si on a une connaissance précise de leurs TP (valeur nominale, évolution en température et vieillissement). After bi-frequency correction, 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).
La solution utilisée actuellement consiste à :  The solution currently used consists of:
- réduire la dispersion du temps de propagation en triant les filtres SAW issus d'un même substrat (« wafer »),  - reduce the dispersion of the propagation time by sorting the SAW filters coming from the same substrate ("wafer"),
- à compenser la dérive du temps de propagation en vieillissement par un nouveau calibrage lors d'une phase de maintien en conditions opérationnelles (MCO).  - To compensate the drift of aging propagation time by a new calibration during a maintenance phase in operational conditions (MCO).
Toutefois malgré le tri en production, il reste nécessaire de prévoir un budget d'erreur significatif (de l'ordre de grandeur de la précision du système GNSS lui-même) afin de pouvoir suivre le comportement en température et dans le temps des filtres SAW.  However, despite the sorting in production, it remains necessary to provide a significant error budget (of the order of magnitude of the precision of the GNSS system itself) in order to be able to monitor the temperature and time behavior of the SAW filters. .
EXPOSÉ DE L'INVENTION STATEMENT OF THE INVENTION
L'invention a pour objectif d'augmenter la précision d'un récepteur GNSS grâce à une meilleure connaissance du temps de propagation du filtre de canal du récepteur.  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.
A cet effet, l'invention propose selon un premier aspect un récepteur d'un système de localisation par satellites, comprenant :  For this purpose, according to a first aspect, the invention proposes a receiver of a satellite positioning system, comprising:
- un filtre de canal comprenant un transducteur d'entrée et un transducteur de sortie, dans lequel la propagation d'un signal émis par un satellite et reçu par le récepteur s'opère selon un trajet direct correspondant à une traversée directe entre les transducteurs d'entrée et de sortie et selon des trajets indirects correspondant à 2n+1 fois le trajet direct du fait de réflexions multiples sur les transducteurs d'entrée et de sortie, n étant un entier supérieur ou égal à 1 ;  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;
- en aval du filtre de canal, une boucle de poursuite pilotée au moyen d'un corrélateur de pilotage centré sur un pic de corrélation entre un code d'étalement du signal émis par le satellite et une réplique locale dudit code générée par le récepteur, downstream of the channel filter, 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,
le récepteur étant caractérisé en ce qu'il comporte : the receiver being characterized in that it comprises:
- un registre à décalage configuré pour générer plusieurs répliques locales dudit code d'étalement décalées les unes des autres de manière à couvrir une fenêtre temporelle correspondant à deux fois l'incertitude sur une estimation du temps de propagation en traversée directe du filtre de canal,  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,
- un second corrélateur décalé du corrélateur de pilotage d'un temps correspondant à deux fois ladite estimation du temps de propagation en traversée directe du filtre de canal, ledit second corrélateur étant configuré pour réaliser la corrélation du code d'étalement du signal émis par le satellite avec lesdites répliques locales générées par le registre à décalage et détecter un pic de corrélation, ledit pic de corrélation correspondant à l'acquisition du signal émis par le satellite soumis à une propagation dans le filtre de canal selon un trajet indirect triple.  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.
Certains aspects préférés, mais non limitatifs, de ce récepteur sont les suivants :  Some preferred, but not limiting, aspects of this receptor are:
- il comporte en outre un calculateur configuré pour calculer une pseudo- distance au satellite à partir du pic de corrélation du corrélateur de pilotage et une pseudo-distance au satellite à partir du pic de corrélation du second corrélateur, ledit calculateur étant en outre configuré pour calculer le temps de propagation en traversée directe du filtre de canal en divisant par deux la différence entre lesdites pseudo-distances.  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.
- le corrélateur de pilotage et le second corrélateur intègrent les résultats de corrélation sur une durée d'intégration, la durée d'intégration du second corrélateur étant supérieure à la durée d'intégration du corrélateur de pilotage. 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.
Selon un second aspect, l'invention concerne un procédé de détermination du temps de propagation d'un signal émis par un satellite dans un récepteur d'un système de localisation par satellites, le récepteur comprenant : According to a second aspect, 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:
- un filtre de canal comprenant un transducteur d'entrée et un transducteur de sortie, dans lequel la propagation d'un signal émis par un satellite et reçu par le récepteur s'opère selon un trajet direct correspondant à une traversée directe entre les transducteurs d'entrée et de sortie et selon des trajets indirects correspondant à 2n+1 fois le trajet direct du fait de réflexions multiples sur les transducteurs d'entrée et de sortie, n étant un entier supérieur ou égal à 1 ;  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;
- en aval du filtre de canal, une boucle de poursuite pilotée au moyen d'un corrélateur de pilotage centré sur un pic de corrélation entre un code d'étalement du signal émis par le satellite et une réplique locale dudit code générée par le récepteur,  downstream of the channel filter, 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,
le procédé étant caractérisé par la mise en œuvre des étapes suivantes : the method being characterized by the implementation of the following steps:
- génération de plusieurs répliques locales dudit code d'étalement décalées les unes des autres de manière à couvrir une fenêtre temporelle correspondant à deux fois l'incertitude sur une estimation du temps de propagation en traversée directe du filtre de canal,  generating several local replicas of said spreading code offset from one another so as to cover a time window corresponding to twice the uncertainty on an estimate of the propagation time directly traversing the channel filter,
- corrélation, au moyen d'un second corrélateur décalé du corrélateur de pilotage d'un temps correspondant à deux fois ladite estimation du temps de propagation en traversée directe du filtre de canal, du code d'étalement du signal émis par le satellite avec lesdites répliques locales générées par le registre à décalage et détection d'un pic de corrélation, ledit pic de corrélation correspondant à l'acquisition du signal émis par le satellite soumis à une propagation dans le filtre de canal selon un trajet indirect triple.  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.
BREVE DESCRIPTION DES DESSINS D'autres aspects, buts et avantages de la présente invention apparaîtront mieux à la lecture de la description détaillée suivante de formes de réalisation préférées de celle-ci, donnée à titre d'exemple non limitatif, et faite en référence aux dessins annexés sur lesquels: BRIEF DESCRIPTION OF THE DRAWINGS Other aspects, objects and advantages of the present invention will appear better on reading the following detailed description of preferred embodiments thereof, given by way of non-limiting example, and with reference to the appended drawings in which: :
- la figure 1 est un schéma simplifié d'un filtre à ondes acoustiques de surface ;  FIG. 1 is a simplified diagram of a surface acoustic wave filter;
- la figure 2 illustre la propagation d'un signal selon des trajets simple et triple au sein d'un filtre selon la figure 1 ;  FIG. 2 illustrates the propagation of a signal along single and triple paths in a filter according to FIG. 1;
- la figure 3 est un schéma illustrant un récepteur GNSS conforme à l'invention.  FIG. 3 is a diagram illustrating a GNSS receiver according to the invention.
DESCRIPTION DETAILLEE DE L'INVENTION DETAILED DESCRIPTION OF THE INVENTION
L'invention concerne selon son premier aspect un récepteur GNSS de positionnement par satellites. En référence aux figures 1 et 2, un tel récepteur comporte de manière conventionnelle un filtre de canal, typiquement un filtre à ondes acoustiques de surface SAW (dont auquel il sera par la suite fait référence, à titre d'exemple non limitatif) qui permet de transmettre de manière sélective une onde acoustique entre deux transducteurs TE, Ts gravés sur un substrat de quartz. La conversion électrique-acoustique et vice-versa est obtenue grâce à l'effet piézo-électrique localisé au niveau de transducteurs d'entrée et de sortie TE, Ts. The invention relates, according to its first aspect, to a GNSS satellite positioning receiver. With reference to FIGS. 1 and 2, such 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 .
Comme les transducteurs ne sont pas parfaits, plusieurs trajets de propagation T1 -T3 des ondes acoustiques s'établissent. Ainsi un signal E émis par un satellite et reçu par le récepteur se propage au sein du filtre SAW selon un trajet direct T1 correspondant à une traversée directe entre les transducteurs d'entrée et de sortie TE, Ts, pour fournir un signal de sortie S1. Since the transducers are not perfect, several propagation paths T1 -T3 of the acoustic waves are established. Thus 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.
Du fait de réflexions multiples R1 , R2 sur les transducteurs d'entrée et de sortie TE, Ts (défaut d'adaptation), le signal E se propage selon des trajets indirects correspondant à 2n+1 fois le trajet direct n étant un entier supérieur ou égal à 1. Un trajet triple correspondant à la somme des trajets T1 , T2 et T3 fournit un signal de sortie S3, dont le niveau est plus faible que celui du signal S1 du trajet direct d'un niveau typiquement de l'ordre de 30 dB. Due to multiple reflections R1, R2 on the input and output transducers T E , T s (maladaptation), 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.
L'invention propose de combiner les capacités de mesure temporelle des signaux GNSS avec ce défaut des filtres SAW de formation de signaux issus de trajets indirects afin d'en déterminer le temps de propagation. Comme cela sera décrit plus en détail ci-après, l'invention propose plus précisément une fois un signal satellite poursuivi de déterminer les pseudo-distances de son trajet simple et de son trajet triple, puis de déduire le temps de propagation du filtre SAW en effectuant la différence de ces pseudo-distances et en divisant le résultat par deux. La différence de ces pseudo-distances correspond effectivement au trajet supplémentaire parcouru par le signal S3 du trajet triple, soit T2+T3 comme représenté sur la figure 2.  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. As will be described in more detail below, 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.
Par conception, la forme d'onde des signaux GNSS permet une mesure de leurs temps de propagation entre les satellites qui les émettent et le récepteur qui les reçoit. La porteuse d'un signal satellite GNSS, étalée spectralement par une séquence binaire pseudo-aléatoire, peut être détectée à condition d'effectuer une corrélation avec un signal local à la même fréquence et étalé par la même séquence. De plus, la séquence d'étalement du signal local doit être synchrone de celle du signal satellite reçu. Ces conditions étant réunies, la position du code du signal local, couramment appelée pseudodistance, est l'image du temps de propagation. En se servant des informations du message de navigation d'au minimum quatre satellites, la position du récepteur peut être déterminée à partir des ces pseudo-distances.  By design, 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. In addition, the spreading sequence of the local signal must be synchronous with that of the received satellite signal. These conditions being met, 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.
En référence à la figure 3, le récepteur GNSS comprend de manière conventionnelle en aval du filtre SAW du filtre de canal, une pluralité de canaux de poursuite chacun associé à un satellite, et dans chaque canal une boucle de poursuite pilotée au moyen d'un corrélateur de pilotage C1 centré sur un pic de corrélation entre un code d'étalement du signal émis SSAT par le satellite et une réplique locale dudit code SRI générée au moyen d'un générateur G1 de signal de réplique intégré dans le récepteur. With reference to FIG. 3, 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.
En réalité, tel que connu, chaque canal de poursuite comprend trois corrélateurs, alimentés par une réplique ponctuelle du code d'étalement (corrélateur dit « Prompt »), décalée en avance de D/2 chip du code d'étalement (corrélateur dit « Early ») et décalée de D/2 chip en retard (corrélateur dit « Late »). La boucle de poursuite du code maintient en permanence le corrélateur « Prompt » sur le pic de corrélation en asservissant la génération de la réplique du code sur le « zéro » de la fonction caractéristique « Early » moins « Late ». Dans le cadre de la présente description, le corrélateur «Prompt » est désigné par le terme de corrélateur de pilotage.  In reality, as is known, 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". In the context of this description, the "Prompt" correlator is referred to as the steering correlator.
La boucle de poursuite d'un canal permet ainsi de poursuivre le signal du trajet simple et de déduire, au moyen d'un calculateur C ici représenté comme également chargé d'assurer le pilotage de la boucle de poursuite, la pseudodistance au satellite correspondant à son trajet simple dans le filtre SAW.  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.
Selon l'invention, lors de la poursuite du signal satellite (trajet simple), le récepteur GNSS selon l'invention, via un allocateur de canal, positionne un deuxième canal à la même fréquence que le canal de poursuite afin de trouver le signal du trajet triple.  According to the invention, 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.
Le récepteur GNSS selon l'invention comporte plus précisément un second générateur de réplique G2 alimentant un registre à décalage RD configuré pour générer plusieurs répliques locales dudit code d'étalement décalées les unes des autres de manière à couvrir une fenêtre temporelle correspondant à deux fois l'incertitude, typiquement de l'ordre de +/- 10 ns, sur une estimation du temps de propagation en traversée directe du filtre de canal.  The GNSS receiver according to the invention 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.
Le récepteur GNSS comporte en outre un second corrélateur C2 décalé du corrélateur de pilotage d'un temps correspondant à deux fois ladite estimation du temps de propagation en traversée directe du filtre de canal, ledit second corrélateur étant configuré pour réaliser la corrélation du code d'étalement du signal émis par le satellite avec lesdites répliques locales générées par le registre à décalage et détecter un pic de corrélation, ledit pic de corrélation correspondant à l'acquisition du signal émis par le satellite soumis à une propagation dans le filtre de canal selon un trajet indirect triple. 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.
Ainsi, pour trouver le signal du trajet triple, on vient explorer les cases temporelles adjacentes au décalage du second corrélateur C2 (décalé du corrélateur de pilotage C1 d'un temps correspondant à une estimation de deux fois le temps de propagation en traversée directe), ces cases temporelles couvrant deux fois l'incertitude sur cette estimation.  Thus, in order to find the signal of the triple 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.
Le calculateur C est également configuré pour calculer la pseudo-distance au satellite correspondant à son trajet triple dans le filtre SAW à partir du pic de corrélation du second corrélateur C2. Le calculateur C est en outre configuré pour calculer le temps de propagation en traversée directe du filtre de canal en divisant par deux la différence entre la pseudo-distance au satellite correspondant à son trajet simple et la pseudo-distance au satellite correspondant à son trajet triple.  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. .
La connaissance précise de ce temps de propagation permet d'améliorer significativement la précision en temps et position d'un récepteur GNSS. Une précision métrique est ainsi atteignable en code P bi-fréquence.  The precise knowledge of this propagation time makes it possible to significantly improve the accuracy in time and position of a GNSS receiver. A metric accuracy is thus attainable in dual-frequency P code.
De manière connue, le corrélateur de pilotage C1 et le second corrélateur C2 intègrent les résultats de corrélation sur une durée d'intégration. Pour permettre une détection adéquate du signal du trajet triple qui est de puissance plus faible que le signal du trajet simple, la durée d'intégration du second corrélateur est supérieure à la durée d'intégration du corrélateur de pilotage. A titre d'exemple la durée d'intégration du second corrélateur est de l'ordre de la seconde lorsque celle du corrélateur de pilotage est de l'ordre de la milliseconde. On a décrit dans ce qui précède la réalisation d'une mesure du temps de propagation du filtre SAW pour un canal de poursuite associé à un satellite. Cette mesure peut bien entendu être utilisée pour les différents canaux de poursuite alimentés par le même filtre SAW. In a known manner, the driving correlator C1 and the second correlator C2 integrate the correlation results over an integration period. To allow adequate detection of the triple path signal which is of lower power than the single path signal, the integration time of the second correlator is greater than the integration time of the driving correlator. By way of example, 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. In the foregoing, it has been described that a measurement of the delay of the SAW filter for a tracking channel associated with a satellite is carried out. This measurement can of course be used for the different tracking channels powered by the same SAW filter.
On notera que dans le cas d'une réception multi-constellations, cette mesure est à effectuer pour chacune des bandes GNSS utilisées (L1 , L2, L5 en GPS ; E1 , E5, E5 en GALILEO).  It should be noted that in the case of a multi-constellation reception, this measurement is to be performed for each of the GNSS bands used (L1, L2, L5 GPS, E1, E5, E5 in GALILEO).
On notera que dans le cas d'une réception sur plusieurs antennes, cette mesure est à effectuer pour chaque chaîne de réception associée à une antenne. L'invention permet ainsi de réaliser la poursuite d'un signal satellite d'une antenne à l'autre de manière continue. La poursuite du signal satellite peut en outre être commutée d'une antenne à l'autre, une telle commutation trouvant notamment application pour les porteurs tournants (fusée, missile par exemple).  Note that in the case of reception on several antennas, this measurement is to be made for each reception chain associated with an antenna. 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).
On relèvera que l'invention s'avère également avantageuse en ce que la mesure de trajet triple se fait dans des conditions identiques à celles du besoin opérationnel (antenne connectée, visibilité des satellites...). Elle ne nécessite aucun moyen de mesure externe, et permet en outre de s'affranchir de la contrainte d'un retour en usine pour calibrage périodique.  It will be noted that 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.
L'invention permet par ailleurs une mesure en continu et en temps réel du temps de propagation du filtre de canal, permettant ainsi une correction en temps réel des mesures de pseudo-distances qui sont entachées d'erreurs liées à l'incertitude sur le temps de propagation au sein du filtre de canal. La mesure en continu permet en particulier de prendre en compte les dérives de température, par exemple lorsque le récepteur démarre à froid puis s'échauffe. La réalisation en temps réel de la mesure permet de ne pas avoir à interrompre la réception des signaux GNSS.  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.
On aura compris que l'invention n'est pas limitée à un récepteur GNSS, mais s'étend également à un procédé de détermination du temps de propagation d'un signal émis par un satellite dans un récepteur d'un système de localisation par satellites, le récepteur comprenant : It will be understood that 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:
- un filtre de canal comprenant un transducteur d'entrée et un transducteur de sortie, dans lequel la propagation d'un signal émis par un satellite et reçu par le récepteur s'opère selon un trajet direct correspondant à une traversée directe entre les transducteurs d'entrée et de sortie et selon des trajets indirects correspondant à 2n+1 fois le trajet direct du fait de réflexions multiples sur les transducteurs d'entrée et de sortie, n étant un entier supérieur ou égal à 1 ;  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;
- en aval du filtre de canal, une boucle de poursuite pilotée au moyen d'un corrélateur de pilotage centré sur un pic de corrélation entre un code d'étalement du signal émis par le satellite et une réplique locale (SRI ) dudit code générée par le récepteur,  downstream of the channel filter, 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,
le procédé étant caractérisé par la mise en œuvre des étapes suivantes : the method being characterized by the implementation of the following steps:
- génération de plusieurs répliques locales dudit code d'étalement décalées les unes des autres de manière à couvrir une fenêtre temporelle correspondant à deux fois l'incertitude sur une estimation du temps de propagation en traversée directe du filtre de canal,  generating several local replicas of said spreading code offset from one another so as to cover a time window corresponding to twice the uncertainty on an estimate of the propagation time directly traversing the channel filter,
- corrélation, au moyen d'un second corrélateur décalé du corrélateur de pilotage d'un temps correspondant à deux fois ladite estimation du temps de propagation en traversée directe du filtre de canal, du code d'étalement du signal émis par le satellite avec lesdites répliques locales générées par le registre à décalage et détection d'un pic de corrélation, ledit pic de corrélation correspondant à l'acquisition du signal émis par le satellite soumis à une propagation dans le filtre de canal selon un trajet indirect triple.  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.
Ce procédé met typiquement en œuvre une étape de calcul en continu et en temps réel d'une pseudo-distance au satellite à partir du pic de corrélation du corrélateur de pilotage, d'une pseudo-distance au satellite à partir du pic de corrélation du second corrélateur, et du temps de propagation en traversée directe du filtre de canal par division par deux de la différence entre lesdites pseudo-distances. 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.
Il peut par ailleurs comprendre une étape de correction de ladite pseudo- distance au satellite calculée à partir du pic de corrélation du corrélateur de pilotage prenant en compte ledit temps de propagation en traversée directe du filtre de canal.  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.

Claims

REVENDICATIONS
Récepteur d'un système de localisation par satellites, comprenant : Receiver for a satellite positioning system, comprising:
- un filtre de canal (SAW) comprenant un transducteur d'entrée (TE) et un transducteur de sortie (Ts), dans lequel la propagation d'un signal émis par un satellite et reçu par le récepteur s'opère selon un trajet direct correspondant à une traversée directe entre les transducteurs d'entrée et de sortie et selon des trajets indirects correspondant à 2n+1 fois le trajet direct du fait de réflexions multiples sur les transducteurs d'entrée et de sortie, n étant un entier supérieur ou égal à 1 ; - a channel filter (SAW) comprising an input transducer (T E ) and an output transducer (T s ), in which the propagation of a signal transmitted by a satellite and received by the receiver takes place according to a direct path corresponding to a direct crossing between the input and output transducers and according to indirect paths corresponding to 2n+1 times the direct path due to multiple reflections on the input and output transducers, n being a higher integer or equal to 1;
- en aval du filtre de canal, une boucle de poursuite pilotée au moyen d'un corrélateur de pilotage (C1 ) centré sur un pic de corrélation entre un code d'étalement du signal émis par le satellite et une réplique locale (SRI ) dudit code générée par le récepteur, - downstream of the channel filter, a tracking loop controlled by means of a control correlator (C1) 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,
le récepteur étant caractérisé en ce qu'il comporte : the receiver being characterized in that it comprises:
- un registre à décalage (RD) configuré pour générer plusieurs répliques locales (SR2) dudit code d'étalement décalées les unes des autres de manière à couvrir une fenêtre temporelle correspondant à deux fois l'incertitude sur une estimation du temps de propagation en traversée directe du filtre de canal, - a shift register (RD) configured to generate several local replicas (S R2 ) 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 in direct crossing of the channel filter,
- un second corrélateur (C2) décalé du corrélateur de pilotage d'un temps correspondant à deux fois ladite estimation du temps de propagation en traversée directe du filtre de canal, ledit second corrélateur étant configuré pour réaliser la corrélation du code d'étalement du signal émis par le satellite avec lesdites répliques locales générées par le registre à décalage et détecter un pic de corrélation, ledit pic de corrélation correspondant à l'acquisition du signal émis par le satellite soumis à une propagation dans le filtre de canal selon un trajet indirect triple. - a second correlator (C2) offset from the control correlator by a time corresponding to twice said estimate of the propagation time directly crossing the channel filter, said second correlator being configured to carry out the correlation of the signal spreading code transmitted by the satellite with said local replicas generated by the shift register and 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 along a triple indirect path .
2. Récepteur selon la revendication 1 , comprenant en outre un calculateur (C) configuré pour calculer une pseudo-distance au satellite à partir du pic de corrélation du corrélateur de pilotage et une pseudo-distance au satellite à partir du pic de corrélation du second corrélateur, ledit calculateur étant en outre configuré pour calculer le temps de propagation en traversée directe du filtre de canal en divisant par deux la différence entre lesdites pseudodistances. 2. Receiver according to claim 1, further comprising a calculator (C) configured to calculate a pseudo-distance to the satellite from the correlation peak of the control correlator and a pseudo-distance to the satellite from the correlation peak of the second correlator, said calculator being further configured to calculate the propagation time in direct crossing of the channel filter by dividing by two the difference between said pseudodistances.
3. Récepteur selon l'une des revendications précédentes, dans lequel le corrélateur de pilotage (C1 ) et le second corrélateur (C2) intègrent les résultats de corrélation sur une durée d'intégration, la durée d'intégration du second corrélateur étant supérieure à la durée d'intégration du corrélateur de pilotage3. Receiver according to one of the preceding claims, in which the control correlator (C1) and the second correlator (C2) integrate the correlation results over an integration duration, the integration duration of the second correlator being greater than the integration duration of the control correlator
4. Récepteur selon l'une des revendications précédentes, dans lequel le filtre de canal est un filtre à ondes acoustiques de surface. 4. Receiver according to one of the preceding claims, wherein the channel filter is a surface acoustic wave filter.
5. Procédé de détermination du temps de propagation d'un signal émis par un satellite dans un récepteur d'un système de localisation par satellites, le récepteur comprenant : 5. Method for determining the propagation time of a signal transmitted by a satellite in a receiver of a satellite localization system, the receiver comprising:
- un filtre de canal (SAW) comprenant un transducteur d'entrée et un transducteur de sortie, dans lequel la propagation d'un signal émis par un satellite et reçu par le récepteur s'opère selon un trajet direct correspondant à une traversée directe entre les transducteurs d'entrée et de sortie et selon des trajets indirects correspondant à 2n+1 fois le trajet direct du fait de réflexions multiples sur les transducteurs d'entrée et de sortie, n étant un entier supérieur ou égal à 1 ; - a channel filter (SAW) comprising an input transducer and an output transducer, in which the propagation of a signal transmitted by a satellite and received by the receiver takes place along a direct path corresponding to a direct crossing between the input and output transducers 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;
- en aval du filtre de canal, une boucle de poursuite pilotée au moyen d'un corrélateur de pilotage (C1 ) centré sur un pic de corrélation entre un code d'étalement du signal émis par le satellite et une réplique locale (SRI ) dudit code générée par le récepteur, - downstream of the channel filter, a tracking loop controlled by means of a control correlator (C1) centered on a correlation peak between a code spreading the signal transmitted by the satellite and a local replica (SRI) of said code generated by the receiver,
le procédé étant caractérisé par la mise en œuvre des étapes suivantes : the process being characterized by the implementation of the following steps:
- génération de plusieurs répliques locales (SR2) dudit code d'étalement décalées les unes des autres de manière à couvrir une fenêtre temporelle correspondant à deux fois l'incertitude sur une estimation du temps de propagation en traversée directe du filtre de canal, - generation of several local replicas (SR2) 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 crossing the channel filter,
- corrélation, au moyen d'un second corrélateur (C2) décalé du corrélateur de pilotage d'un temps correspondant à deux fois ladite estimation du temps de propagation en traversée directe du filtre de canal, du code d'étalement du signal émis par le satellite avec lesdites répliques locales générées par le registre à décalage et détection d'un pic de corrélation, ledit pic de corrélation correspondant à l'acquisition du signal émis par le satellite soumis à une propagation dans le filtre de canal selon un trajet indirect triple. - correlation, by means of a second correlator (C2) offset from the control correlator by a time corresponding to twice said estimate of the propagation time directly crossing the channel filter, of the spreading code of the signal transmitted by the satellite with said local replicas generated by the shift register and detection of a correlation peak, said correlation peak corresponding to the acquisition of the signal transmitted by the satellite subjected to propagation in the channel filter along a triple indirect path.
6. Procédé selon la revendication précédente, comprenant en outre une étape de calcul en continu et en temps réel d'une pseudo-distance au satellite à partir du pic de corrélation du corrélateur de pilotage, d'une pseudo-distance au satellite à partir du pic de corrélation du second corrélateur, et du temps de propagation en traversée directe du filtre de canal par division par deux de la différence entre lesdites pseudo-distances. 6. Method according to the preceding claim, further comprising a step of calculating continuously and in real time a pseudo-distance to the satellite from the correlation peak of the control correlator, a pseudo-distance to the satellite from of the correlation peak of the second correlator, and of the propagation time in direct crossing of the channel filter by dividing by two the difference between said pseudo-distances.
7. Procédé selon la revendication précédente, comprenant en outre une étape de correction de ladite pseudo-distance au satellite calculée à partir du pic de corrélation du corrélateur de pilotage prenant en compte ledit temps de propagation en traversée directe du filtre de canal. 7. Method according to the preceding claim, further comprising a step of correcting said pseudo-distance to the satellite calculated from the correlation peak of the control correlator taking into account said propagation time in direct crossing of the channel filter.
EP13802628.1A 2012-12-10 2013-12-10 Method and device for determining the propagation time of a surface acoustic wave filter Withdrawn EP2929369A1 (en)

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