Satellite system and method for geolocating a radio frequency transmitter

Abstract

The invention relates to a satellite configured to operate radio frequency (RF) communications from one or more antenna systems. The satellite further comprises a device (200) dedicated to the localization of RF equipment, comprising: - a receiving antenna comprising a plurality N of radiating elements (201) configured to receive an RF signal, - analog means (203, 208) for frequency-division multiplexing the signals received on the N radiating elements, - means for transmitting (210) the multiplexed signals to a ground satellite station. The invention also relates to a complete satellite system further comprising a satellite station and computing means configured to receive the multiplexed signals, demultiplex them, and perform direction finding to determine the position of the RF equipment to be located, and to the associated localization method. Figure for the abstract: Fig. 2

Description

Title of the invention: Satellite system and method for geolocating a radiofrequency transmitter Technical field

[0001] The invention lies in the field of satellite geolocation of radiofrequency (RF) transmitters, and relates more particularly to a system and method for geolocation of a radiofrequency transmitter operated by a system involving a conventional communications satellite. Prior art

[0002] Satellite communications are booming, but are increasingly frequently jammed by radio frequency equipment emitting signals in the frequency band of the communication channel, either involuntarily by equipment linked to other satellites, or deliberately by equipment intended to disrupt satellite communications.

[0003] For the satellite operator, it is useful to know the direction of arrival of the jamming signal, in order to locate the ground equipment at the origin of the interfering emissions, and to take all necessary measures to return the communications system to nominal operation.

[0004] Determining the position of a radiofrequency transmitter from a satellite can be done using a deviation measurement method. This concept, widely used in radars to locate targets, is based on the formation of three beams from three antennas, an array antenna or a specific deviation measurement source: - a sum channel, - two difference channels, in two orthogonal axes, typically the East-West and North-South axes.

[0005] This solution makes it possible to achieve very good location accuracy performance, but over very low angular coverage, of the order of a few tenths of a degree. It is therefore mainly intended for applications such as satellite misalignment compensation, and is not suitable for locating a transmitter over the entire coverage area of ​​a satellite, which is typically around ten degrees.

[0006] Furthermore, this solution is not compatible with the presence of a co-frequency traffic signal (i.e. the simultaneous transmission of a traffic signal and an interfering signal in the same frequency channel) since only the signal of interest must be present.

[0007] Determining the position of radiofrequency transmitters by processing Radio direction finding, which consists of acquiring the same signal from several antennas and / or sensors and then implementing processing to determine the direction of arrival of this signal, is more suitable for locating a jammer over the entire coverage area of ​​a satellite, especially since these processing operations are compatible with co-frequency emissions. However, they require a satellite configured to receive the RF signals emitted by the jammer, transpose them into frequency, digitize them and process them in an on-board computer. While this type of solution is classic, it has the disadvantage of being restrictive in terms of development time and being expensive, because it requires the development, integration and validation of signal conversion / digitization chains and an on-board computer dedicated to the direction finding function. In addition, this solution significantly increases the satellite's consumption.

[0008] Another known solution is to receive the radiofrequency signals on board the satellite, to transpose them into frequency, to digitize them on board, then to send them to the ground for the geolocation processing. The transmission of the signals to the ground can be done for example by using the satellite's telemetry / remote control link. This solution avoids the development of a computer on board the satellite, but still requires the carriage of conversion and digitization chains on board the satellite, which requires a significant amount of time for development, integration and validation, and therefore has a high cost.

[0009] To overcome these drawbacks, one object of the invention is to propose a solution allowing the geolocation of a radiofrequency transmitter from a “conventional” satellite, not requiring the development of equipment specific to the location function. This solution aims to accelerate the development and integration of communication satellites, and to reduce their costs.

[0010] To do this, it relies on two elements: - the transmission to the ground of radiofrequency signals received from analog equipment not requiring specific developments, - the implementation on the ground of direction finding processing. Summary of the invention

[0011] To this end, the present invention describes a satellite configured to operate radiofrequency communications from one or more antenna systems. The satellite according to the invention further comprises a device dedicated to the location of RF equipment. It comprises: - a receiving antenna comprising a plurality N of radiating elements configured to receive an RF signal, - analog means of frequency multiplexing of signals received on the N radiating elements, configured to transpose said signals around distinct central frequencies distributed in a given frequency band and to combine them, and - means of transmitting the combined signal to a ground satellite station for the implementation of direction finding processing.

[0012] According to one embodiment of the invention, the analog means for frequency multiplexing the N received signals comprise N analog bandpass filters having substantially identical bandwidths and N analog transposition means configured to transpose said signals so that the difference between two central frequencies of transposed signals is greater than or equal to the bandwidth of the N analog bandpass filters.

[0013] Advantageously, the satellite is configured so that the frequency band in which the frequency multiplexed RF signals are retransmitted is reserved for these retransmissions.

[0014] According to an embodiment of the satellite according to the invention, the number N of radiating elements of the reception antenna of the device dedicated to the location of RF equipment is less than 10.

[0015] The invention also describes a satellite communications system enabling the location of a radiofrequency transmitter comprising a satellite according to the invention, and one or more satellite stations on the ground, the satellite and the stations being configured to together enable the calibration of the system by: - the emission of a calibration signal from a satellite station whose position is known, - the reception of said calibration signal on a plurality of radiating elements, the frequency multiplexing of the calibration signals received on said radiating elements and the retransmission of the frequency multiplexed calibration signals, by the device dedicated to the location of RF equipment of the satellite, - reception, by a satellite station, of frequency multiplexed calibration signals re-transmitted by the satellite, - demultiplexing and digitizing the calibration signals, and implementing goniometry processing on the demultiplexed and digitized calibration signals, in order to calculate: • a direction of arrival of the calibration signal, • a position of the satellite station transmitting the calibration signal, then • a calibration difference between the known position of the satellite station emitting the calibration signal and the position of the station satellite transmitting the calibration signal determined using direction finding processing then to allow together the determination of the position of RF equipment emitting an interfering signal by: - the reception of an RF signal comprising said signal interfering on a plurality of radiating elements, the frequency multiplexing of the RF signals received by said radiating elements and the re-emission of the frequency-multiplexed RF signals, by the device dedicated to the location of RF equipment of the satellite, - reception, by a satellite station, of frequency multiplexed RF signals emitted by the satellite, - demultiplexing and digitizing said RF signals, implementing a direction finding algorithm on the demultiplexed and digitized RF signals so as to determine a direction of arrival of the interfering signal, calculating a position of the RF equipment emitting said interfering signal, and correcting the calculated position by the calibration deviation.

[0016] Finally, the invention relates to a method for determining the position of radiofrequency equipment in a satellite communications system comprising a satellite as described above, and one or more ground satellite stations. The method comprises: - a calibration step of said satellite communications system, by: • a sub-step of transmitting a calibration signal from a satellite station whose position is known, • a sub-step of receiving the calibration signal on a plurality of radiating elements, of frequency multiplexing the calibration signals received on said radiating elements and of re-transmitting the frequency multiplexed calibration signals, by the device dedicated to locating RF equipment of the satellite, • a sub-step of reception, by a satellite station, of the frequency multiplexed calibration signals re-transmitted by the satellite, • a sub-step of demultiplexing and digitizing said calibration signals, and implementing goniometry processing on the demultiplexed and digitized calibration signals, so as to determine a direction of arrival of the calibration signal, a position of the satellite station transmitting the calibration signal, then a calibration difference between the known position of the satellite station transmitting the calibration signal and the position of the satellite station transmitting the calibration signal determined using the goniometry treatments; - one or more steps of determining the position of an RF transmitter emitting an interfering signal, by: • a sub-step of receiving an RF signal comprising said signal interfering on a plurality of radiating elements, of frequency multiplexing of the RF signals received by said radiating elements and of re-transmitting the frequency multiplexed RF signals, by the device dedicated to locating RF equipment of the satellite, • a sub-step of reception, by a satellite station, of the frequency multiplexed RF signals emitted by the satellite, • a sub-step of demultiplexing and digitizing said RF signals, then implementing direction finding processing on the demultiplexed and digitized RF signals so as to determine a direction of arrival of the interfering signal, calculating a position of the radiofrequency equipment emitting said interfering signal, and correcting the calculated position by the calibration difference. Brief description of the drawings

[0017] The invention will be better understood and other characteristics, details and advantages will appear more clearly on reading the following description, given without limitation, and thanks to the appended figures, given by way of example.

[0018] [Fig.l] [Fig.l] represents an example of a satellite transmission system suitable for implementing the invention.

[0019] [Fig.2] [Fig.2] represents an embodiment of a device dedicated to the loca installation of RF equipment on board a satellite so as to implement the invention.

[0020] [Fig.3] [Fig.3] is a block diagram representing the steps of a process for locating radiofrequency equipment according to one embodiment of the invention.

[0021] Identical references may be used in different figures when they designate identical or comparable elements. Description of the embodiments

[0022] [Fig. 1] represents an example of a satellite transmission system suitable for implementing the invention. It comprises a satellite 101 configured to operate radiofrequency communications, such as for example a satellite broadcasting digital television, a telephone satellite, an observation satellite, a satellite for global positioning system (GNSS), or any other type of satellite. The satellite can be either geostationary or moving. It can for example be configured to transmit / receive in the C (from 3.4 GHz to 7.075 GHz), Ku (from 10.70 GHz to 12.75 GHz) and / or Ka (from 20 GHz to 30 GHz) frequency band.

[0023] The satellite 101 is generally controlled by a satellite gateway such as the station 102, through a bidirectional Remote Control and Telemetry (TC / TM) link. It is configured to receive / send data from / to one or more satellite stations, such as the station 102 and / or other ground stations. This configuration corresponds to a state-of-the-art satellite system, configured to operate one or more communications missions, and obvious variations can be made thereto, for example by operating the remote control link and the telemetry link from two different stations.

[0024] The satellite system according to the invention differs from the state of the art in that the satellite 101 is further configured to allow the location of radiofrequency equipment such as the transmitter 103, the emissions of which are likely to disrupt those of the satellite, whether intentionally or unintentionally. This may be, for example, a poorly oriented transmitter belonging to a third-party communications system, a satellite station of the system whose emissions are not controlled, or equipment specifically designed to disrupt the uplink to the satellite (jammer).

[0025] To perform this location function, the satellite comprises, in addition to one or more antenna systems and equipment allowing it to operate its main communications function(s), a device allowing the system to perform a location function for interfering radiofrequency equipment. This device is configured to receive RF signals on a plurality of radiating elements of an array antenna, to frequency multiplex them, then to retransmit them to a ground station in a given frequency band, which may be different from the frequency band of the received signals. A ground station comprising calculation means or connected to equipment 104 comprising calculation means is configured to receive these signals, demultiplex them and implement direction finding processing in order to locate the interfering radiofrequency equipment. In [Fig.l], the ground station responsible for receiving the multiplexed signals is station 102 operating the telemetry link, but any ground station could be able to retrieve these signals and process them.

[0026] When the direction finding processing, and possibly the demultiplexing of the signals, are carried out by calculation means 104 separate from the satellite station 102, the latter is then responsible for digitizing the signals, possibly demultiplexing them, then transmitting them to the equipment 104.

[0027] The top of [Fig.2] represents an embodiment of a device 200 dedicated to a function for locating RF equipment, on board a satellite. It allows the retransmission to a ground station of analog signals received on different radiating elements of an antenna. In the example of [Fig.2], and in a non-limiting manner, the device is configured to be on board a communications satellite for which the uplink is operated in Ku band. In this band may appear the useful traffic signals associated with the main communications mission of the satellite, as well as one or more interfering or jamming signals. The downlink, in which the frequency multiplexed signals are returned, is operated in the Ka band. These two bands are mentioned for illustration purposes only.

[0028] The device 200 dedicated to the location function comprises an array antenna, with or without a parabolic reflector, and a plurality N of radiating elements 201 configured to allow the reception of a signal in a given frequency band, here the Ku band. Each signal can be processed by one or more low-noise amplification and filtering stages 202, in order to reduce the noise present on the received signals.

[0029] The device 200 also comprises analog means 203 for frequency multiplexing of the N signals received. These multiplexing means may for example comprise: - N identical analog transposition means 204, configured to transpose the signals from their frequency band to a common frequency band in the manner of repeaters, for example at a given frequency in the Ka band for their retransmission to the ground, - N identical analog bandpass filters 205, configured to limit to a width BW the bandwidth of the N signals acquired on the radiating elements 201 and to reject the harmonics which may result from the frequency transposition 204, - N analog transposition means 206, configured to transpose the signals of the common frequency band by applying to each of them a single frequency offset so that they are distributed in a given frequency band, preferably in a regular manner. The frequency offset between the signals is such that the difference between two central frequencies of transposed signals is greater than or equal to the bandwidth BW of each of the N analog bandpass filters 205, - a combiner 208 of analog signals with N inputs and one output, configured to sum the N filtered and transposed signals, in order to generate a signal corresponding to the frequency multiplexing of the N signals.

[0030] The analog multiplexing means 203 may also comprise N analog bandpass filters 207, centered around the central frequencies of the transposed signals, so as to reject possible harmonics linked to the frequency transposition 206.

[0031] Equivalently, the analog transposition can be performed in a single step by the analog transposition means 207, in which case the elements 204 and 205 are no longer necessary.

[0032] Other equivalent arrangements are possible and would produce equivalent results, for example by reversing the positions of the filters and transposition means, by adding other analog filters, and / or by performing more signal transposition steps.

[0033] The device 200 dedicated to the location of RF equipment on board the satellite finally comprises a power amplifier 209 and transmission means 210 such as a transmission antenna.

[0034] The bottom of Figure 2 is a frequency representation of the signals retransmitted by the satellite. The abscissa axis represents the frequency, and the ordinate axis the power spectral density (PSD) of the transmitted signals. In this example, the device 200 dedicated to location comprises five radiating elements. Each radiating element receives a signal which comprises a useful signal portion 221 and an interfering signal portion 222. The five signals are filtered and frequency multiplied, so that the signals have equivalent bandwidths BW, and so that each signal has a central frequency 223 at least BW away from that of the other signals. Advantageously, the central frequencies are equally distributed in a given frequency band, the width of which is greater than or equal to N*BW. In [Fig.2], the elements specific to a signal are represented in different gray levels.

[0035] The ground satellite station 102 receiving the multiplexed signals is configured to digitize them, demultiplex them, and implement direction finding processing to determine the direction of arrival of the interfering signal, and consequently the position of the RF transmitter, or to transmit the digitized signals, multiplexed or not, to calculation means 104 configured to determine the position of the RF transmitter. It therefore comprises at least a receiving antenna with one or more radiating elements, one or more low-noise amplifiers associated with one or more bandpass filters, and an analog to digital converter. Digitization can be done: - on the received signal, which includes all the multiplexed signals, either directly on the carrier frequency at which the signal is transmitted, or after transposition around a carrier frequency more suited to its digitization, in which case the multiplexed signals are then separated using digital filters. Americas, or - independently for each of the multiplexed signals, separating them from their carrier frequency using frequency converters and analog filters, then digitizing them separately.

[0036] Thus, the direction finding processing can be implemented on all of the signals acquired by the N radiating elements 201 of the device 200 dedicated to locating the satellite, in order to locate the RF transmitter(s) of interfering signals.

[0037] For this purpose, many direction finding algorithms are known. The most suitable are the so-called "high resolution" processing, such as for example the MUSIC algorithm (English acronym for MULTIPLE Signal Classification), ESPRIT (English acronym for Estimation of Signal Parameter via Rotational Invariance Technique), MinNorm (English acronym for Minimum Norm), which make it possible to determine the direction of arrival of one or more signals acquired by several sensors with very high precision, but all types of multi-source direction finding algorithms are conceivable. For this, the interfering signals can be characterized for example by their bandwidth, their power, their transmission times or frequencies, their waveform, etc. Knowing the position and orientation of the satellite, it is possible to determine the position of the radio equipment at the origin of the interfering signal from the direction of arrival of the signals.

[0038] All types of additional processing intended to improve the quality of the transmitted signals can advantageously be implemented to correct the transformations seen by the signal during its transmission between the interfering equipment, the satellite and the ground receiving satellite station, such as for example satellite pointing errors, the Doppler effect, variations in the transfer function as a function of frequency, compensation for amplifier non-linearities, compensation for frequency deviations, time synchronization shifts, etc. These compensations make it possible to improve the quality of the signals processed by the direction finding algorithm, and therefore the precision of the location function.

[0039] The device 200 dedicated to location on board the satellite 101 is completely analog, which allows it to be implemented without requiring development, integration and testing of an on-board computer specifically dedicated to the location function. However, the analog equipment of the device necessarily has imperfections that affect the quality of the location, which is why a preliminary calibration phase is necessary to guarantee the performance of the location function of the system. Indeed, in the absence of calibration, the imperfections of the equipment crossed by the signals during their processing in the satellite, or the inaccuracies in the orientation of the satellite are likely to generate positioning errors that can range up to several degrees of difference.

[0040] The calibration of the system is done by the emission of a specific signal from a ground station whose position is known precisely (georeferenced or obtained using a satellite positioning device such as a GNSS receiver (English acronym for Global Navigation Satellite Systems, or geolocation and navigation by a satellite system)). The signal can for example be an AWG type signal (English acronym for Arbitrary Waveform Generator), spread across an entire analysis band, but any type of signal can be used provided that it has good autocorrelation properties. The satellite 101 retransmits to a satellite station of the system the signals received by the radiating elements of its device 200 dedicated to location, after having frequency multiplexed them.The ground station 102, possibly connected to remote computing means 104, is configured to digitize and demultiplex the received signals, and implement direction finding processing in order to locate the ground station transmitting the calibration signal. The error between the known position of the ground station transmitting the calibration signal and its position determined using the location function constitutes the correction to be made to the next position measurements.

[0041] The calibration can be carried out only once, at the start of operation of the satellite or each time the location function is implemented by the satellite system. It can advantageously be renewed regularly in order to adapt to variations in the characteristics of the device 200 on board the satellite. Successive measurements can be carried out in order to average the calibration deviation to reduce any measurement errors linked, for example, to white noise or propagation.

[0042] The satellite system according to the invention allows the precise location of radiofrequency equipment based on two principles: - a device 200 on board the satellite 101 allowing the acquisition of a radiofrequency signal on several radiating elements, - the transmission of signals acquired on the radiating elements of the satellite to a ground station 102 for the implementation of direction finding processing.

[0043] This solution addresses the problem posed insofar as it is not necessary to develop specific equipment on board to digitize the signals received and integrate the processing necessary for the location function. Indeed, the only equipment necessary on board the satellite is known analog equipment operating conventional functions requiring no particular hardware development and no software development. In this case, it is a series of analog repeaters arranged in parallel, the target frequency of which allows the frequency multiplexing of the signals when their outputs are connected to a signal combiner. The development plan for such a solution is therefore extremely short and inexpensive because it considerably reduces the design, validation and qualification stages of the system, which makes it compatible with the short schedules generally required for traditional telecommunications systems, with low development costs.

[0044] The solution can be adapted to any telecommunications satellite, since it is carried out using an additional device 200 specific to the location function. Indeed, the use for location purposes of the antennas ensuring the other functions of the satellite is generally not possible: - when the satellite is equipped with a conventional reflector satellite antenna, with a single radiating element, it is not possible to implement direction finding processing because the direction of arrival information extracted by direction finding is carried by the phase shift between the signals received from different channels constituting the antenna network, - when the satellite has an array antenna, the implementation of the invention could be possible. However, the minimum gain performance required to ensure the link budgets means that these antennas have a very large number of radiating elements (typically around fifty or more). This high number results from the need to obtain a sufficient antenna surface, and from the limitation of the size of the radiating elements taking into account the array lobes. The implementation of direction finding processing on all of these radiating elements to ensure the location function would be suboptimal because the frequency multiplexing of the signals received on each of the radiating elements would use a significant bandwidth following the frequency multiplexing implemented. The implementation of the location function on a sub-part of these radiating elements would make it possible to limit the consumed band.However, antennas are adapted according to the specifications specific to their function. Different specifications for communication functions (directivity, signal-to-interference ratio C / I, isolation, etc.) and location functions (number of interferers to be located, angular precision, etc.) generally result in different optimal definitions of the antennas, particularly with regard to the network mesh. As a result, the performance of a location function resulting from direction finding processing implemented on acquisitions made by a communications antenna would be suboptimal.

[0045] Introducing on the satellite an antenna device 200 specific to the location function makes it possible to adapt their number, size, shape and position of the radiating elements to the coverage sought for the localization function, so as to present sufficient gain on this coverage without generating ambiguities in the direction of arrival (a phenomenon close to network lobes for beamforming). The number of radiating elements depends on the number of transmitters to be located. An order of magnitude consists of using twice as many radiating elements as transmitters to be located simultaneously, which is why it must be greater than 2, and is typically less than 10, and advantageously less than or equal to 6.

[0046] The additional device 200 has only a small additional cost in terms of payload on the satellite since the number of radiating elements of the antenna of the device dedicated to the location function can be very reduced.

[0047] Multiplexing signals in the frequency domain has a bandwidth cost proportional to the number of radiating elements used by the device 200, since the bandwidth required for the localization function is at least N*BW. However, frequency multiplexing is preferred to time multiplexing because time multiplexing should be performed: - either the implementation of delay lines on each of the channels on board the satellite, which results in a cost in terms of surface area and mass, - either the acquisition of signals on the different elements at different times, which is not compatible with the requirements of direction finding algorithms.

[0048] Furthermore, the downstream frequency band is generally higher than the upstream, with more bandwidth availability, which is advantageous for frequency division multiplexing.

[0049] Another advantage of the proposed solution lies in its flexibility and scalability: the direction finding processing is implemented on the ground, which eliminates all integration constraints, implementation complexity, consumption problems and cost. In addition, updates to the processing software are significantly easier on the ground than in a computer on board the satellite.

[0050] The invention therefore relates to a satellite having a device 200 dedicated to location as described above, as well as to a system comprising a satellite 101 according to the invention and one or more ground stations 102. The ground stations and the satellite are configured to together enable the calibration of the system by: - ​​the emission of a calibration signal from a satellite station whose position is known, - reception of the calibration signal on a plurality of radiating elements, frequency multiplexing of the calibration signals received on said radiating elements and retransmission of the frequency multiplexed calibration signals, by the device dedicated to the location of RF equipment from the satellite, - reception, by the satellite station at the origin of the transmission of the calibration signal or by another satellite station 102 on the ground, of the frequency multiplexed calibration signals retransmitted by the satellite, - the digitization and demultiplexing of these signals, and the implementation of goniometry processing on the demultiplexed and digitized calibration signals, so as to determine a direction of arrival of the calibration signal, by the ground station having received the signals, possibly associated with calculation means 104 to which it is connected. This direction of arrival is then used to determine the location of the station transmitting the calibration signal by associating it with the position and orientation of the satellite, then a calibration difference between the known position of the satellite station transmitting the calibration signal and the position determined by the goniometry processing is measured.

[0051] The system equipment is also configured to together allow the determination of the position of an RF radiofrequency equipment 103 at the origin of an interfering signal by: - the acquisition of an RF signal comprising the signal interfering on a plurality of radiating elements, the frequency multiplexing of the RF signals received on said radiating elements and the retransmission of the frequency multiplexed RF signals, by the device dedicated to the location of RF equipment of the satellite, - reception, by a satellite station 102, of frequency multiplexed RF signals emitted by the satellite, - the demultiplexing and digitization of said RF signals, by the satellite station 102 or the calculation means 104 to which it is connected, the implementation of direction finding processing on the demultiplexed and digitized RF signals to determine a direction of arrival of the interfering signal, the calculation of a position of the interfering equipment 103 using the direction of arrival of the interfering signal, the position of the satellite 101 and its orientation, and the correction of this position by the calibration deviation calculated during the calibration phase.

[0052] The invention also relates to a method for determining the position of RF equipment in a satellite system according to the invention.

[0053] [Fig. 3] is a block diagram of the steps of a location method in a satellite system according to the invention. It is implemented in a satellite communications system comprising a satellite such as satellite 101, integrating a device 200 for acquiring a signal on a plurality of radiating elements, then re transmit to a ground station for the implementation of direction finding processing. The method includes: - a step 301 of calibration of the satellite communications system. This step includes: • a sub-step 302 of transmitting a calibration signal from a satellite station whose position is known, • a sub-step 303 of receiving the calibration signal on a plurality of radiating elements, of frequency multiplexing the calibration signals received on said radiating elements and of re-transmitting the frequency multiplexed calibration signals, by the device dedicated to locating RF equipment of the satellite, • a sub-step 304 of receiving, by a satellite station, the frequency multiplexed calibration signals re-transmitted by the satellite, • a sub-step 305, carried out by the satellite station having received the signals and / or a processing device to which the signals are transmitted, of demultiplexing and digitizing said calibration signals, and of implementing goniometry processing on the demultiplexed and digitized calibration signals, so as to determine a direction of arrival of the calibration signal, to calculate a position of the satellite station transmitting the calibration signal using the direction of arrival, the positioning and the orientation of the satellite, then to calculate a calibration difference between the known position of the satellite station transmitting the calibration signal and the position of the satellite station transmitting the calibration signal determined using the goniometry processing.

[0054] The method according to one embodiment of the invention also comprises one or more steps 310 of determining the position of an RF transmitter emitting an interfering signal. This step comprises: • a sub-step 311 of receiving an RF signal comprising the signal interfering on a plurality of radiating elements, of frequency multiplexing of the RF signals received by said radiating elements and of retransmission of the frequency multiplexed RF signals, by the device dedicated to the location of RF equipment of the satellite, • a sub-step 312 of reception, by a satellite station, of the frequency multiplexed RF signals emitted by the satellite, • a sub-step 313 of demultiplexing and digitizing said RF signals, of implementing a direction finding algorithm on the demultiplexed RF signals triplexed and digitized so as to determine a direction of arrival of the interfering signal, to calculate a position of the radiofrequency equipment emitting said interfering signal, and to correct the calculated position by the calibration deviation, implemented by the satellite station and / or the calculation means to which it is connected.

Claims

Claims

1. Satellite (101) configured to operate radiofrequency, RF, communications from one or more antenna systems, characterized in that it further comprises a device (200) dedicated to the location of RF equipment, said device dedicated to the location of RF equipment comprising: - a receiving antenna comprising a plurality N of radiating elements (201) configured to receive an RF signal, - analog means (203, 208) for frequency multiplexing the N RF signals received on the N radiating elements, configured to transpose said N RF signals received on the N radiating elements around distinct central frequencies distributed in a given frequency band and to combine them, - means for transmitting (210) the N frequency-multiplexed RF signals to a ground satellite station for implementing direction finding processing.

2. Satellite according to claim 1, in which the analog means for frequency multiplexing the N RF signals received on the N radiating elements comprise N analog bandpass filters having substantially identical passbands (BW) (205, 207) and N analog transposition means (204, 206) configured to transpose said signals so that the difference between two central frequencies of transposed signals is greater than or equal to the passband (BW) of the N analog bandpass filters.

3. Satellite according to one of the preceding claims, configured so that the frequency band in which the N frequency-multiplexed RF signals are retransmitted is reserved for these retransmissions.

4. Satellite according to one of the preceding claims, in which the number N of radiating elements (201) of the receiving antenna of the device (200) dedicated to the location of RF equipment is less than 10

5. IV. Satellite communications system enabling the location of a radiofrequency transmitter, characterized in that it comprises a satellite (101) according to one of claims 1 to 4, and one or more ground satellite stations (102), configured to together allow the calibration of the system by: - the emission of a calibration signal from a satellite station (102) whose position is known, - the reception of said calibration signal on a plurality of radiating elements (201), the frequency multiplexing (203) of the calibration signals received on said plurality of radiating elements and the retransmission (210) of the frequency multiplexed calibration signals, by the device (200) dedicated to the location of RF equipment of the satellite, - reception, by a satellite station (102), of the frequency multiplexed calibration signals retransmitted by the satellite (101), - demultiplexing and digitizing said calibration signals, and implementing direction finding processing on the demultiplexed and digitized calibration signals, so as to determine a direction of arrival of the calibration signal, a position of the satellite station emitting the calibration signal, then a calibration difference between the known position of the satellite station (102) emitting the calibration signal and the position of the satellite station (102) emitting the calibration signal determined using the direction finding processing; then to allow together the determination of the position of an RF equipment (103) emitting an interfering signal by: - receiving an RF signal comprising said interference signal on a plurality of radiating elements (201), frequency multiplexing (203) of the RF signals received on said plurality of radiating elements and retransmitting (210) the frequency multiplexed RF signals, by the device (200) dedicated to locating RF equipment of the satellite, - reception, by a satellite station (102), of the frequency multiplexed RF signals emitted by the device (200) dedicated to the location of RF equipment of the satellite (101), - the demultiplexing and digitization of said mul- RF signals frequency-diplexed, implementing a direction-finding algorithm on the demultiplexed and digitized RF signals so as to determine a direction of arrival of the interfering signal, calculating a position of the RF equipment (103) emitting said interfering signal, and correcting the calculated position by the calibration deviation.

6. Method for determining the position of radiofrequency equipment (103) in a satellite communications system comprising a satellite (101) according to one of claims 1 to 4, and one or more satellite stations (102) on the ground, characterized in that it comprises: - a step (301) of calibrating said satellite communications system, by: • a sub-step (302) of transmitting a calibration signal from a satellite station (102) whose position is known, • a sub-step (303) of receiving the calibration signal on a plurality of radiating elements (201), of frequency multiplexing (203) of the calibration signals received on said plurality of radiating elements and of re-transmission (210) of the frequency multiplexed calibration signals, by the device (200) dedicated to the location of RF equipment of the satellite, • a sub-step (304) of reception, by a satellite station (102), of the frequency multiplexed calibration signals retransmitted by the satellite (101), • a sub-step (305) of demultiplexing and digitizing said calibration signals, and of implementing goniometry processing on the demultiplexed and digitized calibration signals, so as to determine a direction of arrival of the calibration signal, a position of the satellite station (102) emitting the calibration signal, then a calibration difference between the known position of the satellite station (102) emitting the calibration signal and the position of the satellite station (102) emitting the calibration signal determined using direction finding processing; one or more steps (310) of determining the position of an RF transmitter (103) emitting an interfering signal, by: • a sub-step (311) of receiving an RF signal comprising said interfering signal on a plurality of radiating elements (201), of frequency multiplexing (203) of the RF signals received on said plurality of radiating elements and of re-transmission (210) of the frequency multiplexed RF signals, by the device (200) dedicated to the location of RF equipment of the satellite, • a sub-step (312) of reception, by a satellite station (102), of the frequency multiplexed RF signals emitted by the device (200) dedicated to the location of RF equipment of the satellite, • a sub-step (313) of demultiplexing and digitizing said frequency-multiplexed RF signals, then implementing direction finding processing on the demultiplexed and digitized RF signals so as to determine a direction of arrival of the interfering signal, calculating a position of the radiofrequency equipment (103) emitting said interfering signal, and correcting the calculated position by the calibration difference.

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