Method for locating a GNSS interference source, product computer program and associated location device
The method of rotating antennas to measure phase shifts between GNSS signals addresses the challenge of beacon-based interference source location, reducing costs and maintaining accuracy without fixed beacons.
Patent Information
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- THALES SA
- Filing Date
- 2022-03-25
- Publication Date
- 2026-06-26
AI Technical Summary
Existing methods for locating GNSS signal interference sources require fixed beacons, which increase installation and maintenance costs and reduce coverage area, while achieving only moderate accuracy.
A method using rotating antennas to measure phase shifts between GNSS signals, determining the direction of interference by identifying the maximum phase shift alignment without the need for fixed beacons, combined with a localization device and computer program to implement this process.
Accurately locates GNSS interference sources with reduced installation and maintenance costs, maintaining precision by using rotating antennas to determine the alignment direction of the interference source.
Smart Images
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Abstract
Description
Title of the invention: Method for locating a GNSS interference source, product computer program and associated location device
[0001] The present invention relates to a method for locating a GNSS (Global Navigation Satellite Systems) interference source.
[0002] The present invention also relates to a computer program product and a localization device associated with this method.
[0003] More specifically, the technical field of the invention is that of GNSS interference source localization devices based on antenna arrays. These devices are designed to precisely and rapidly determine the position of the interference source in order to eliminate it by appropriate means.
[0004] In the prior art, there already exist many methods for determining the direction of arrival of radio signals, including GNSS signals.
[0005] Among these methods, one example is the technique implemented by so-called ARVA devices (for "Avalanche Victim Search Device") which are used in the mountains to find avalanche victims. An ARVA-type device activated in receive mode indicates roughly the direction of arrival of the signal emitted by a corresponding beacon on the victim. This allows a person who has escaped to quickly find the victim's position under the snow.
[0006] Regarding the determination of the direction of arrival of jamming signals during GNSS navigation, methods using antenna arrays are known. These methods are generally based on the phase shifts between the signals received on the different antennas to find the directions of arrival of the jamming signals. The devices implementing these methods are generally fixed and require the use of several beacons to locate the position of the jamming source by intersecting angular sectors, with ambiguity resolution.
[0007] Precisely locating the position of the source of GNSS signal interference using fixed beacons requires high angular measurement accuracy due to the distance between the beacons. Bringing the beacons closer together generally improves location accuracy but also reduces the coverage area. Increasing the number of beacons is possible, but this raises issues of installation and maintenance costs.
[0008] The present invention aims to overcome these drawbacks and to provide a method for locating the source of GNSS signal interference that does not require a fixed beacon, while remaining relatively accurate. This reduces installation and maintenance costs.
[0009] To this end, the invention relates to a method for locating a source of GNSS interference comprising the following steps:
[0010] - rotating two antennas around a common axis of rotation to form N different respective positions corresponding to different angles of rotation;
[0011] - in each of the N positions, acquisition by each antenna of a GNSS signal including a useful signal and a jamming signal, and calculation of a phase shift between the acquired jamming signals;
[0012] - determining the direction of the interference source using a value maximum of the N calculated phase shifts.
[0013] Thanks to these characteristics, the method according to the invention makes it possible to avoid the use of a fixed beacon while remaining precise. Indeed, the phase shift measured between the two rotating antennas as a function of the angle of rotation describes a curve whose maximum indicates the angle of rotation for which the two antennas are aligned in the direction of the jamming source, without ambiguity regarding the two opposite directions. The invention therefore proposes to use this maximum to determine the direction of the jamming source.
[0014] According to other advantageous aspects of the invention, the method comprises one or more of the following features, taken individually or in all technically possible combinations:
[0015] - the rotation of the two antennas is achieved by a rotating carrier, the antennas being advantageously fixed relative to the carrier;
[0016] - the rotation of the antennas includes one complete turn;
[0017] - the GNSS signal acquired in each position comprises K samples of this signal;
[0018] - the calculation of each phase shift between the acquired jamming signals includes the calculation of a complex cross-correlation coefficient between samples of GNSS signals acquired in the corresponding position;
[0019] - the calculation of each phase shift between the acquired jamming signals is determined by the argument of the complex cross-correlation coefficient;
[0020] - Determining the direction of the interference source includes the determination of an azimuth angle of the interference source in a local frame associated with the two antennas, the azimuth angle being determined in a plane of rotation of the two antennas;
[0021] - the azimuth angle is determined as the angle of rotation of the antennas in the respective position of these antennas corresponding to the maximum value of the N calculated phase shifts;
[0022] - a step of determining a direction of the source of interference in a geographical reference point from said azimuth angle of the jamming source and inertial data characterizing an angular position of the antennas in this geographical reference point;
[0023] - the direction of the interference source is specified by repeating the aforementioned steps of the process starting from a geographical position different from the antennas;
[0024] - said different geographical position is determined in the direction of the source of jamming determined during a previous iteration of said steps of the process.
[0025] The invention also relates to a computer program product comprising software instructions which, when executed by a computer, implement the process as defined above.
[0026] The invention also relates to a device for locating a source of interference, comprising technical means adapted to implement the method as defined above.
[0027] These features and advantages of the invention will become apparent from the following description, given solely by way of non-limiting example, and made with reference to the accompanying drawings, in which:
[0028] - [Fig. 1] [Fig. 1] is a schematic view of a localization device source of interference according to the invention;
[0029] - [Fig.2] [Fig.2] is a flowchart of a localization process according to the invention, the localization method being implemented by the localization device of [Fig. 1]; and
[0030] - [Fig.3] [Fig.4] Figures 3 and 4 are views illustrating the implementation of less certain steps in the localization process of the [Fig.2].
[0031] Fig. 1 illustrates a localization device 10 for a source of interference 12 of GNSS signals.
[0032] The jamming source 12 includes, for example, any electronic device capable of emitting radio signals, known as jamming signals, which prevent normal reception of GNSS signals from a GNSS system 14 by a GNSS receiver. In particular, as is known, the GNSS system 14 consists of several satellites configured to transmit GNSS signals to the ground. The GNSS receiver receives these signals from at least some of the satellites of the GNSS system 14 in order to determine its geographic position. The GNSS system 14 is, for example, the GPS (Global Positioning System) or the GALILEO system, which are known per se.
[0033] In one embodiment, the jamming source 12 is intended to intentionally impair the proper functioning of the GNSS receiver. In another embodiment, the jamming source 12 unintentionally impairs the proper functioning of the GNSS receiver.
[0034] The localization device 10 according to the invention makes it possible to locate the source of interference 12. Once located, the source of interference 12 can be deactivated to restore the proper functioning of the GNSS receiver.
[0035] With reference to [Fig.1], the localization device 10 comprises an input module 21, a processing module 22 and an output module 23. In some cases, the localization device 10 further comprises a GNSS receiver enabling its position to be determined in the absence of interference signals.
[0036] The input module 21 allows the reception of radio signals, in particular GNSS signals, which include useful signals from the GNSS system 14 and jamming signals from the jamming source 12. The input module 21 also allows the transmission of these received signals to the processing module 22.
[0037] To receive GNSS signals, the input module 21 includes an antenna array comprising at least two spaced antennas. In the example in [Fig. 1], two antennas 31 and 32 are shown. In a generic case, the antenna array may include a number of antennas strictly greater than 2.
[0038] As shown in Figure 1, the antennas 31, 32 are arranged on a carrier 35 in the same plane and are spaced from each other in this plane by a distance d. The carrier 35 is advantageously an aircraft, in particular a drone.
[0039] According to the preferred embodiment of the invention, the antennas 31, 32 are fixed relative to the carrier 35. In such a case, the carrier 35 has a rotating carrier capable of implementing a rotation of the plane comprising the antennas 31, 32 around an axis of rotation perpendicular to this plane.
[0040] According to another embodiment, the antennas 31, 32 are mounted on a rotating platform which is capable of rotating relative to the carrier 35. In such a case, the carrier 35 is configured to move in space along, for example, a substantially rectilinear trajectory or presents a fixed carrier.
[0041] The processing module 22 is configured to process the GNSS signals received by the input module 21 in order to determine the direction of the interference source 12, as will be explained in more detail later.
[0042] The processing module 22 may, for example, take the form of one or more software programs stored in memory and executable by one or more processors. Alternatively or in addition, the processing module 22 may take at least partial form of a programmable logic circuit, such as an FPGA (Field-Programmable Gate Array) type circuit.
[0043] In some embodiments, the processing module 22 is further configured to control the operation of the antennas 31, 32 and optionally the carrier 35. For example, the processing module 22 is configured to control the rotation of the antennas 31, 32 as explained previously. According to other embodiments, the control of the carrier 35, and in particular the rotation of the antennas 31, 32, is carried out from a dedicated control module either integrated into the carrier 35 or located remotely from it. Such a control module may also be part of the localization device 10.
[0044] In the example of [Fig. 1], the processing module 22 is embedded in the carrier 35, as is the input module 21. According to another embodiment, the processing module 22 is located away from the carrier 35. In such a case, it is capable of receiving the signals received by the input module 21 by any suitable means.
[0045] The output module 23 is configured to deliver the result of the processing performed by the processing module 22. In particular, the output module 23 is configured to deliver the direction of the jamming source 12 determined by the processing module 22.
[0046] For example, the direction of the jamming source 12 is given as a heading angle of the jamming source 12 in a geographical coordinate system whose axes are, for example, formed by the North, East, and Vertical directions. According to another embodiment, the direction of the jamming source 12 is given as an angle between the direction of movement of the carrier 35 and the direction of the jamming source 12. In the first case, it is therefore an absolute direction of the jamming source 12, and in the second case, a relative direction.
[0047] The output module 23 is for example adapted to provide the absolute and / or relative direction of the jamming source 12 to an operator and / or to any other system usable for example to control the carrier 35, such as the control module mentioned above.
[0048] Finally, just like the processing module 22, the output module 23 can be carried in the carrier 35 or remotely from it.
[0049] The localization device 10 allows the localization process 100 according to the invention to be implemented, which will henceforth be explained with reference to [Fig.2] showing a flowchart of its steps.
[0050] During an initial step 110, the antennas 31, 32 are rotated around the axis of rotation to form N different respective positions corresponding to different angles of rotation.
[0051] In particular, in the example of Figure 3 illustrating a frame (XAnt, YAnt, ZAnt) linked to the antenna array, antenna 31 is placed at the center of the frame and antenna 32 is initially placed at a distance d from antenna 32 along the OYAnt axis. The plane (XAnt, YAnt) thus corresponds to the plane of rotation of antennas 31, 32 and the axis 0ZAnt to the axis of rotation of antennas 31, 32.
[0052] Advantageously, during this step 110, a complete turn around the OZAnt axis is carried out.
[0053] In each respective position of the antennas 31, 32 during their rotation, the line connecting the centers of the two antennas forms an angle 3° with respect to the OYAnt axis. This angle 3° therefore defines each respective position of the antennas 31, 32 during their rotation and is called the angle of rotation. Given the initial position of the antenna 32, this angle varies from 0° to 360° during a complete rotation.
[0054] The following step 120 is implemented in parallel with step 110.
[0055] During this step 120, in each position, each antenna 31, 32 acquires a GNSS signal comprising, as explained previously, a useful signal and a jamming signal.
[0056] In particular, each GNSS signal is acquired in the form of K samples.
[0057] Thus, denoting the sample k acquired by antenna 31 and s^k) the sample k acquired by antenna 32 in a given position, these samples can be written in the following form:
[0058] s^k) = s1GNSS(k) + s1B(k) S2(k) = S2;g_NSs(^) +s2,b(^) , ' k=LK
[0059] where Sp GNss(k) denotes the useful signal and SpB( k) the jamming signal of the sample k from the corresponding antenna P (p = 1, 2).
[0060] Then, during the same step, the processing module 22 determines a phase shift A (Pesi between the jamming signals acquired in the corresponding position.
[0061] To do this, the processing module 22 first calculates the complex cross-correlation coefficient Rxx of the acquired samples, according to the following expression: 100621 R^, s2) =
[0063] where ( * denotes the complex conjugation operator.
[0064] The cross-correlation coefficient Rxx is a complex number, that is to say a number with a real part Re(Rxx ) and an imaginary part hn(Rxx ).
[0065] The phase shift A between the two jamming signals received on the two antennas is then given by the angle (or argument) of the complex number RXx, that is:
[0066] A (pest=atan2(Im(Rxx), Re(Rxx)).
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[0080] It is therefore clear that during this step 120, a phase shift value A Ç? f is calculated for each of the N positions defined by the rotation angle 6 In the next step 130, the processing module 22 determines the relative direction of the interference source 12 using a maximum value of the N phase shifts A (pes^ calculated. In particular, during this step 130, the processing module 22 determines an azimuth angle AzAnt of the jamming source 12 in the (XAnt, YAnt) plane. According to the invention, this azimuth angle corresponds to the maximum value of the set of phase shifts A(pt) between the two jamming signals determined during the previous step. More specifically, it is clear that the phase shift A (pt between the two jamming signals received by the two antennas 31, 32 is related to the azimuth Azet at the site SÎAnt of the jamming source 12 by the following relation: where 6 corresponds to the path difference between antenna 32 and antenna 31 as shown in [Fig.3] according to which: 6= d» cos^Az^-eAnt) • sin(Si^) and where 2 corresponds to the wavelength of the jamming signal, bq, a phase shift due to the defect of the antennas and analog channels of the electronics, and SÎAnt a site angle calculated with respect to the OZAnt axis. The phase shift A can therefore be written as: △Vest^^C^^Ant-QAnt) * Sin(SiAat) Since the site angle Si^t remains constant during antenna rotation, the last relationship can be written in the following form: A » C • cos ( - 0^ ) + bv, where C is a constant value. In other words, the phase shift A(p) has a sinusoidal curve. Two examples of A(p) curves are shown in Figure 4. In particular, this Figure 4 shows in its left part a sinusoidal curve of A(p) for the site value SiAni = 90° and in its right-left part a sinusoidal curve of A(p) for the site value SiA1A = 30°. In both cases, it is assumed that d = 2 / 3 and bcp = 30°.
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[0090] As these two examples show, it is clear that the phase shift A m reached is its maximum value when AzAnt = Thus, during this step 130, the processing module 22 analyzes all the pairs { e^k), atp (k)\ 1 Ant v est f k=LN , obtained during the rotation in the previous step and obtains the arrival azimuth Estimated by Azest • Ant Az^t=e(m) m = ammax / { A tp V In order to improve the accuracy of determining the index m of the position of the maximum of the function A(D), in certain embodiments, the modulus is Processing step 22 determines the intersections of the function A (Û) with a value r. median (line Lm in figure 4) which is located halfway between the maximum (line Lmax in figure 4) and the minimum (line Lmin in figure 4). Then, the processing module 22 determines the maximum of the function A (Pesi which is located at the center of the two intersections obtained framing the first estimated position of the maximum. In the next step 140, the processing module 22 determines, if necessary, the direction of the interference source 12 in the geographic coordinate system. To do this, the processing module 140 uses, for example, inertial data characterizing the angular position of the carrier 35 relative to the geographical reference point. For example, the processing module 140 can associate an angular position of the carrier 35 with each value of phase shift A (Pes^ measured during step 120 and then determine the angular position of the carrier 35 corresponding to the maximum value of the phase shifts A (p . Then, the direction of the jamming source 12 in the geographic coordinate system (such as a heading) can be obtained by transforming into the geographic coordinate system the azimuth angles Az^ni and site determined in the previous step. In the preferred embodiment of the invention, at least steps 110 to 130 and advantageously step 140 are repeated to specify the direction of the interference source 12. For example, steps 110 to 140 can be repeated several times from different positions of the carrier 35 and then the direction of the jamming source 12 is specified by cross-referencing the results obtained during these different iterations.
[0091] According to another embodiment, only steps 110 to 130 are repeated several times. In this case, for each subsequent iteration, the carrier 35 is directed in the direction of the jamming source 12 obtained during the previous iteration. It is therefore clear that in this case, only the relative direction of the jamming source 12 with respect to the carrier 35 is necessary. The advantage of this solution is that even if the results of the first iterations are coarse, the carrier 35 will always eventually converge in the correct direction, and the closer it is, the more accurate the results will be.
Claims
Demands
1. A method for locating (100) a source of interference (12) of GNSS signals, comprising the following steps: - rotating (110) two antennas (31, 32) around a common axis of rotation (OZAnt) to form N different respective positions corresponding to different angles of rotation; - in each of the N positions, acquisition (120) by each antenna of a GNSS signal comprising a useful signal and an interference signal, and calculation of a phase shift between the acquired interference signals; - determination (130) of a direction of the source of interference (12) using a maximum value of the N calculated phase shifts; the determination of the direction of the jamming source (12) including the determination of an azimuth angle of the jamming source (12) in a local frame associated with the two antennas (31, 32), the azimuth angle being determined in a plane of rotation of the two antennas (31, 32);the azimuth angle being determined as the angle of rotation of the antennas (31, 32) in the respective position of these antennas (31, 32) corresponding to the maximum value of the N calculated phase shifts.;
2. Method (100) according to claim 1, wherein the rotation of the two antennas (31, 32) is carried out by a rotating carrier (35), the antennas (31, 32) being advantageously fixed relative to the carrier (35).
3. Method (100) according to claim 1 or 2, wherein the rotation of the antennas (31, 32) comprises one complete turn.
4. Method (100) according to any one of the preceding claims, wherein the GNSS signal acquired at each position comprises K samples of that signal.
5. Method (100) according to claim 4, wherein the calculation of each phase shift between the acquired jamming signals includes the calculation of a complex cross-correlation coefficient between the samples of the GNSS signals acquired in the corresponding position.
6. Method (100) according to claim 5, wherein the calculation of each phase shift between the acquired jamming signals is determined by the argument of the complex cross-correlation coefficient.
7. A method (100) according to any one of the preceding claims, further comprising a step (140) of determining a direction of the jamming source (12) in a geographical frame of reference from said azimuth angle of the jamming source (12) and inertial data characterizing an angular position of the antennas (31, 32) in this geographical frame of reference.
8. A method (100) according to any one of the preceding claims, wherein the direction of the jamming source (12) is specified by repeating said steps of the method from a geographical position different from the antennas (31, 32).
9. Method (100) according to claim 8, wherein said different geographical position is determined in the direction of the jamming source (12) determined during a previous iteration of said steps of the method.
10. Product computer program comprising software instructions which, when executed by a computer, implement the method (100) according to any one of the preceding claims.
11. A device for locating (10) a source of interference (12) of GNSS signals, comprising technical means (21, 22, 23) adapted to implement the method (100) according to any one of claims 1 to 9.