Device and method for amplifying a radio-frequency signal, and device for positioning a mobile receiver with a device for amplifying a radio-frequency signal

Abstract

Disclosed is a device for amplifying a radio-frequency signal, said radio-frequency signal comprising a sum of signals of unmodulated pure carrier, said device comprising: - a computing unit comprising computing means and configured to receive as input the radio-frequency signal and determine a compensated radio-frequency signal, said compensated radio-frequency signal being a linear combination of the radio-frequency signal and of a linearisation signal; - a power amplifier being configured to receive as input the compensated radio-frequency signal, amplify the compensated radio-frequency signal and output an amplified radio-frequency signal; - a coupler connected to the output of the power amplifier and configured to sample part of the amplified radio-frequency signal output from the power amplifier, the computing means of the computing unit further being configured to determine amplitudes and / or phases of the signals of pure carrier forming the linearisation signal.

Description

Description Title of the invention: Device and method for amplifying a radio frequency signal, device for positioning a receiving mobile with a radio frequency signal amplification device technical field

[0001] The invention relates to a system and method for amplifying a radio frequency signal. The technical field of the invention is that of radio frequency electronics. The device and method according to the invention are applicable to the amplification of radio frequency signals formed by a sum of unmodulated pure carrier signals. Another object of the invention is a positioning device for a receiving mobile device comprising a device for amplifying a radio frequency signal. Previous technique

[0002] Radio frequency signals formed by unmodulated frequency combs are used today in geolocation systems, multi-frequency radar systems, medical imaging, and spectroscopy. Often, these applications require amplifying the unmodulated frequency combs using radio frequency power amplifiers. These components have a non-linear response, resulting in distortion of the amplified signals and the addition of spurious frequencies—frequencies not present in the radio frequency signal being amplified.

[0003] Spurious frequencies, also called intermodulation products or intermodulation frequencies, are linear combinations of the frequencies forming the original comb or their harmonics. Harmonics of a frequency F1 are multiples of that frequency, such as 2 x F1, 3 x F1, and so on. If the frequency comb is formed by two frequencies, F1 and F2, an example of an intermodulation frequency would be 3 x F1 - 2 x F2. The presence of these spurious signals in the amplified signal is a cause of signal distortion and alters the bandwidth of the transmitted signal. These distortions modify the transmission template by increasing the spectral band occupied by the amplified signal and can lead to violations of certifications such as the European CE conformity certification or the US FCC conformity certification (Federal Communications Commission).It is therefore necessary to minimize these parasitic frequencies in the amplified signal.

[0004] Several power amplifier linearization techniques are known to those skilled in the art. These techniques apply to modulated radio frequency signals and include adaptive linearization to maintain a transmission template. Adaptive linearization relies on measuring the spectrum of the amplified signal and modeling the power amplifier's transfer function. Using a feedback loop, it is then possible to adjust the parameters used in the power amplifier model and modify the amplifier's input signal by the inverse of the modeled transfer function, thereby reducing the amplitude of intermodulation frequencies in the amplified signal.

[0005] However, these methods require multi-variable modeling of the power amplifier's transfer function, making them complex to implement. Currently, no radio frequency amplifier linearization devices exist that do not require modeling of the amplifier's transfer function while also being suitable for unmodulated frequency combs. Summary of the invention

[0006] One aim of the present invention is to at least partially overcome the aforementioned drawbacks.

[0007] In particular, an objective of the present invention is to provide a device for amplifying a radio frequency signal comprising a sum of unmodulated pure carrier signals which acts discretely on each of the intermodulation frequencies present in the amplified radio frequency signal.

[0008] To this end, the invention relates to a device for amplifying a radio frequency signal, said radio frequency signal comprising a sum of unmodulated pure carrier signals of distinct frequencies, said device comprising: - a computing unit comprising computing means and configured to receive as input the radio frequency signal and determine a compensated radio frequency signal, said compensated radio frequency signal being a linear combination of the radio frequency signal and a linearization signal, said linearization signal comprising a sum of unmodulated pure carrier signals of distinct frequencies, the frequencies of the unmodulated pure carrier signals forming the linearization signal being intermodulation frequencies of the unmodulated pure carrier signals included in the radio frequency signal; - a power amplifier, having an input and an output, said power amplifier being configured to receive the compensated radio frequency signal as input, amplify the compensated radio frequency signal and provide an amplified radio frequency signal as output; - a coupler connected to the output of the power amplifier and configured to take a portion of the amplified radio frequency signal at the output of the power amplifier, said coupler being further configured to provide the taken portion of the amplified radio frequency signal to the computing unit; the computing means of the computing unit being further configured to modify, on the basis of the part of the amplified radio frequency signal taken by the coupler, the amplitudes and / or phases of the pure carrier signals forming the linearization signal.

[0009] A sum of unmodulated pure carrier signals is defined as a discrete sum of signals. An unmodulated pure carrier signal is defined as a signal in the form of a continuous, unmodulated wave. For example, a pure sine wave is a pure sinusoid. A radio frequency signal formed by a sum of unmodulated pure carrier signals is also called a frequency comb.

[0010] The intermodulation frequency is defined as a frequency obtained by linearly combining the frequencies that make up the radio frequency signal and / or their harmonics. Intermodulation products are defined as unmodulated pure-carrier signals possessing an intermodulation frequency.

[0011] A computing unit is defined as a component comprising computing means such as a microprocessor or a field-programmable gate array (FPGA). The computing unit may also include storage means such as a memory element for storing information such as the frequencies, amplitudes, or phases of the radio frequency signal. The storage means are connected to the computing means.

[0012] A power amplifier is defined as an electronic component configured to receive a radio frequency signal as input and provide an amplified version of the input radio frequency signal as output. The amplifier is configured to amplify the compensated radio frequency signal in order to provide the amplified radio frequency signal.

[0013] A coupler is defined as an electronic component configured to receive an amplified radio frequency signal as input and to extract a portion of that amplified radio frequency signal. The coupler is further configured to supply that extracted portion of the radio frequency signal to the processing unit.

[0014] The device according to one aspect of the invention solves the technical problem of linearizing a power amplifier for frequency comb by using a so-called linearization signal which is also in the form of a frequency comb, the frequencies forming the linearization signal being intermodulation frequencies of the frequencies of the radio frequency signal to be amplified.

[0015] The frequencies included in the linearization signal are, for example, chosen from the intermodulation frequencies appearing in the signal amplified by the power amplifier in the absence of the linearization signal. Alternatively, the intermodulation frequencies included in the delinearization signal can be chosen from the frequencies forming the radio frequency signal and according to a predetermined criterion.

[0016] According to one embodiment, the intermodulation frequencies forming the linearization signal are stored in the computing unit.

[0017] According to one aspect of the invention, the device allows the power amplifier's response to be linearized using a compensated radio frequency signal, the compensated radio frequency signal being formed by a linear combination of the radio frequency signal and the linearization signal. In one embodiment, the compensated radio frequency signal is the sum of the radio frequency signal and the linearization signal.

[0018] In one embodiment, the computing means are configured to modify the phases and / or amplitudes of the pure carrier signals included in the linearization signal so as to minimize a function of the power of the signals having an intermodulation frequency in the portion of the amplified signal taken by the coupler or in the amplified radio frequency signal. The minimized function is, for example, the sum of the powers of the intermodulation products or the maximum power value of the intermodulation products. The computing means are, for example, configured to minimize the power function by applying an optimization method such as a gradient descent method or a Newton-Raphson method.

[0019] The device according to one aspect of the invention then linearizes the power amplifier by determining the phases and / or amplitudes of the unmodulated pure carrier signals forming the linearization signal, so as to minimize the amplitude of the intermodulation products in the amplified radio frequency signal. In one embodiment, the calculation means are configured to reduce the amplitude of the intermodulation products below a predetermined threshold. This predetermined threshold is, for example, a reduction of at least 40 dB in the intermodulation products compared to the amplified radio frequency signal in the absence of the linearization signal.

[0020] In other words, the linearization signal comprises signals with the same frequencies as the intermodulation products in the amplified radio frequency signal in the absence of the linearization signal, but with a phase such that, at the amplifier output (i.e., in the amplified signal), the intermodulation products of the amplified signal in the absence of the linearization signal are in opposite phase to the amplified frequencies of the linearization signal. The result is that the amplitude of the intermodulation products in the amplified signal is significantly reduced.

[0021] In one embodiment, the computing means are configured to modify the phases and / or amplitudes of the signals forming the linearization signal multiple times, so as to obtain the desired reduction of intermodulation products in the amplified radio frequency signal. For example, the computing means are configured to modify the phases and / or amplitudes of an initial linearization signal until the amplitudes of the intermodulation products in the amplified radio frequency signal are reduced below a predetermined threshold. The initial linearization signal is obtained, for example, by randomly selecting the phases and / or amplitudes of the unmodulated pure-carrier signals forming the linearization signal.

[0022] In one embodiment, the computing means are configured to modify the amplitudes and / or phases of the signals forming the linearization signal by applying a gradient descent method. This gradient descent method is applied to all the unmodulated pure-carrier signals forming the linearization signal simultaneously. In another embodiment, the computing means are configured to minimize, by gradient descent, the sum of the powers of the intermodulation products or the maximum value of the intermodulation products in the amplified signal or in the portion of the amplified signal taken by the coupler. Minimization can be achieved by applying an optimization method such as gradient descent to the function to be minimized.The starting point of the gradient descent method can be an initial linearization signal which has measured or predetermined intermodulation frequencies, the phase and / or amplitude of each signal forming the initial linearization signal being chosen randomly.

[0023] Advantageously, when the quantity to be minimized is the maximum power value of the intermodulation products in the amplified radio frequency signal, it is possible to choose the maximum value as the threshold value given by a standard.

[0024] In another embodiment, the computing means are configured to modify the amplitudes and / or phases of the signals forming the linearization signal by applying a Newton-Raphson type optimization method or a confidence region algorithm. The quantity to be minimized in this case can be the sum of the powers of the intermodulation products in the amplified signal or the maximum value of the intermodulation products in the amplified signal.

[0025] According to particular embodiments, the device according to one aspect of the invention has one or more of the following characteristics, taken individually or in all technically possible combinations: - the computing means are configured to determine amplitudes and / or phases of pure carrier signals forming the linearization signal so as to reduce below a predetermined threshold the amplitude of signals having intermodulation frequencies in the amplified radio frequency signal; - The computing means are configured to modify the amplitudes and / or phases of the pure carrier signals forming the linearization signal so as to minimize a function of the power of the signals possessing intermodulation frequencies in the portion of the amplified radio frequency signal taken by the coupler - The computing resources are configured to modify the amplitudes and / or phases of the pure carrier signals forming the linearization signal by applying an optimization method chosen from a group including: gradient descent, Newton-Raphson method, confidence region algorithm; - The device also includes: o a first digital / analog converter configured to provide an analog version of the radio frequency signal from a digital version of the radio frequency signal, said digital version of the radio frequency signal being provided by the computing unit; o a second digital-to-analog converter configured to provide an analog version of the linearization signal from a digital version of the linearization signal, said digital version of the linearization signal being provided by the computing unit; o an analog-to-digital converter connected to the coupler and the computing unit, the analog-to-digital converter being configured to receive as input the portion of the amplified radio frequency signal taken by the coupler and to provide the computing unit with a digital version of the portion of the amplified radio frequency signal taken by the coupler; o a power combiner configured to receive as input the analog version of the radio frequency signal and the analog version of the linearization signal and provide as output an analog version of the compensated radio frequency signal; - the device further includes means for measuring the amplitudes and / or phases of signals having intermodulation frequencies in the amplified radio frequency signal portion taken by the coupler; according to one embodiment these measurement means are included in the calculation unit; - the calculation unit is further configured to determine the intermodulation frequencies of pure carrier signals included in the linearization signal from the radio frequency signal and the amplified radio frequency signal; - the predetermined threshold is a reduction in the amplitudes of signals having intermodulation frequencies of at least 40 dB compared to signals having intermodulation frequencies in a radio frequency signal obtained by amplifying the radio frequency signal in the absence of the linearization signal; - the computing means are configured to modify phases and / or amplitudes of the pure carrier signals forming the linearization signal by gradient descent on all the pure carrier signals forming the linearization signal at the same time.

[0026] Another object of the invention is a transmitting base for a positioning system of a receiving mobile comprising a device for amplifying a radio frequency signal according to one aspect of the invention.

[0027] The invention also relates to a positioning system for a receiving mobile comprising a transmitting base according to one aspect of the invention.

[0028] Another aspect of the invention relates to a method for amplifying a radio frequency signal, said radio frequency signal comprising a sum of unmodulated pure carrier signals of distinct frequencies, said method comprising the following steps: - determination, using a computing unit comprising computing means, of a compensated radio frequency signal, said compensated radio frequency signal being a linear combination of the radio frequency signal and a linearization signal, said linearization signal being a sum of unmodulated pure carrier signals of distinct frequencies, the frequencies of the unmodulated pure carrier signals forming the linearization signal being intermodulation frequencies of the unmodulated pure carrier signals included in the radio frequency signal; - amplification, by a power amplifier, of the compensated radio frequency signal so as to provide an amplified radio frequency signal; - sampling, by a coupler and at the output of the power amplifier, of a portion of the amplified radio frequency signal; - provision of the portion taken from the amplified radio frequency signal to the computing unit; - modification by the computing means of the computing unit and on the basis of the radio frequency signal and the portion of the amplified radio frequency signal of the amplitudes and / or phases of the pure carrier signals forming the linearization signal. In one embodiment, the modification of the amplitudes and / or phases of the pure carrier signals forming the linearization signal is performed so as to minimize a function of the power of the signals possessing intermodulation frequencies in the amplified radio frequency signal or in the portion of the amplified radio frequency signal taken by the coupler. In another embodiment, the minimization of the intermodulation products in the amplified radio frequency signal involves reducing the amplitudes of the intermodulation products below a predetermined threshold.

[0029] According to one embodiment, the process according to the invention further comprises a step of receiving the radio frequency signal by a computing unit.

[0030] The method according to one aspect of the invention makes it possible to linearize the amplification of a radio frequency signal by a power amplifier. The linearization is achieved by reducing the amplitude of the intermodulation products in the amplified signal.

[0031] Thanks to the method according to one aspect of the invention, it is possible to maintain a given radio frequency signal template while increasing its output power from the power amplifier. The method according to one aspect of the invention can therefore be used when it is necessary to amplify a signal formed by a frequency comb while respecting a given transmission template.

[0032] For example, the method according to one aspect of the invention can be used in the context of positioning a receiving mobile relative to a system of frequency comb transmitting antennas, such as that developed by the applicant.

[0033] According to particular embodiments, the device according to one aspect of the invention has one or more of the following characteristics, taken individually or in all technically possible combinations: - the amplitudes and / or phases of the pure carrier signals forming the linearization signal are modified so as to reduce below a predetermined threshold the amplitude of the signals having intermodulation frequencies in the amplified radio frequency signal; - the amplitudes and / or phases of the pure carrier signals forming the linearization signal are modified so as to minimize a function of the power of the signals having intermodulation frequencies in the part of the amplified radio frequency signal taken by the coupler; - the process also includes: o a digital / analog conversion of the radio frequency signal; o a digital / analog conversion of the linearization signal; o an analog / digital conversion of the amplified radio frequency signal portion taken by the coupler at the output of the power amplifier; o a linear combination of the analog version of the radio frequency signal and the analog version of the linearization signal to provide an analog version of the compensated radio frequency signal - the process further includes a step of determining the intermodulation frequencies forming the linearization signal from the radio frequency signal and the amplified radio frequency signal; - the step of determining the intermodulation frequencies includes the amplification of the radio frequency signal in the absence of the linearization signal; - the step of determining the intermodulation frequencies including the amplification of the radio frequency signal in the absence of the linearization signal also includes the determination of the phases of an initial linearization signal; - the step of modifying, by the calculation means of the calculation unit and on the basis of the radio frequency signal and the part of the amplified radio frequency signal, the amplitudes and / or phases of the pure carrier signals forming the linearization signal is repeated several times so as to reduce the amplitude of the signals having intermodulation frequencies below said predetermined threshold; - the step of modifying, by the calculation means of the calculation unit and on the basis of the part of the amplified radio frequency signal, the amplitudes and / or phases of the pure carrier signals forming the linearization signal includes a measurement of the amplitudes and / or phases of the signals having intermodulation frequencies in the part of the amplified radio frequency signal taken by the coupler; according to one embodiment, this step is carried out using measurement means included in the calculation means of the calculation unit; - The modification of the phases and / or amplitudes of the pure carrier signals forming the linearization signal is performed by gradient descent on all the pure carrier signals forming the linearization signal simultaneously. - The predetermined threshold is a reduction in the amplitudes of the signals having intermodulation frequencies of at least 40 dB compared to the signals having intermodulation frequencies in a radio frequency signal obtained by amplifying the radio frequency signal in the absence of the linearization signal; Brief description of the drawings

[0034] The invention will be better understood upon reading the following description, given solely by way of example, and with reference to the figures in the appendix in which: - [Fig. 1] shows a diagram of an embodiment of a device for amplifying a radio frequency signal according to one aspect of the invention; - [Fig. 2] shows a flowchart representing an embodiment of a method for amplifying a radio frequency signal according to another aspect of the invention, the method being implemented by the system of Figure 1; - [Fig. 3] shows a graph representing a radio frequency signal amplified by a power amplifier according to the prior art, and - [Fig. 4] shows a graph representing a radio frequency signal amplified by a device according to one aspect of the invention. Description of the implementation methods

[0035] Fig. 1 illustrates an embodiment of a device 1 for amplifying a radio frequency signal. As shown in Fig. 1, the device 1 comprises a computing unit 11 including computing means 11.1. The computing unit 11 is configured to receive a radio frequency signal to be amplified and to determine a compensated radio frequency signal. The solid lines in Fig. 1 indicate connections among the various components of the device 1.

[0036] The computing unit 11, as illustrated in Fig. 1, comprises a first digital-to-analog converter 12 and a second digital-to-analog converter 13. The first digital-to-analog converter 12 is configured to provide an analog version of the radio frequency signal from a digital version of the radio frequency signal. Similarly, the second digital-to-analog converter 13 is configured to provide an analog version of the linearization signal from a digital version of the linearization signal. As illustrated in Fig. 1, the computing unit 11 further comprises a power combiner 14 configured to receive as input the analog version of the radio frequency signal and the analog version of the linearization signal and to provide as output an analog version of the compensated radio frequency signal. In other words, the power combiner 14 and the computing means 11.1 are configured to determine the compensated radio frequency signal as a linear combination of the radio frequency signal and the linearization signal. The computing resources 11.1 can include: an FPGA, a microcontroller, or a GPU (Graphics Processing Unit). One of the advantages of the GPU, in particular, is its ability to parallelize certain calculations, which improves (reduces) the execution time of certain optimization algorithms, such as gradient descent. It can also be a combination of these examples, for example, the combination of an FPGA with a GPU.

[0037] Device 1, as illustrated in Fig. 1, further includes a power amplifier configured to receive the compensated radio frequency signal as input and provide the amplified radio frequency signal as output. Device 1 includes a coupler 16 connected to the output of the power amplifier 15 and configured to take a portion of the amplified radio frequency signal.

[0038] The portion of the amplified signal taken by the coupler 16 is then provided to an analog / digital converter 17 which provides a digital version of the portion of the signal taken to the processing unit 11.

[0039] In one embodiment, the device 1 includes means for measuring the amplitudes and / or phases of signals possessing intermodulation frequencies in the amplified radio frequency signal. Using these measurement means and the processing unit, it is then possible to determine the intermodulation frequencies present in the amplified signal in the absence of the linearization signal. These frequencies are then identified as signals constituting the linearization signal. In another embodiment, the measurement means are further configured to determine the phases of the intermodulation frequencies present in the amplified radio frequency signal in the absence of the linearization signal.

[0040] In one embodiment, the device 1 further comprises means for measuring the amplitudes and / or phases of signals possessing intermodulation frequencies in the portion of the amplified radio frequency signal taken by the coupler 16. Using these measurement means and the calculation means of the processing unit, it is then possible to modify the amplitudes and / or phases of the linearization signal to minimize a function of the power of the intermodulation products in the portion of the amplified radio frequency signal taken by the coupler 16. This minimization significantly reduces the presence of intermodulation products in the amplified radio frequency signal. It is then possible to maintain the waveform of the amplified radio frequency signal. According to one embodiment, these means of measurement are included in the calculation unit 11.

[0041] According to another embodiment, the intermodulation frequencies of the signals forming the linearization signal are determined directly by the computing unit 11. For example, these intermodulation frequencies can be stored in a memory element included in the computing unit.

[0042] The computing means 11.1 of the computing unit are configured to modify, based on the portion of the amplified radio frequency signal taken by the coupler 16, the amplitudes and / or phases of the pure carrier signals forming the linearization signal. This makes it possible to reduce the amplitude of the intermodulation products in the amplified radio frequency signal and to obtain a linear amplification device for radio frequency combs.

[0043] According to one embodiment, the computing means are configured to modify the phases and / or amplitudes of the radio frequency signals by applying a gradient descent type method on a function of the power of the intermodulation products in the amplified signal portion taken by the coupler.

[0044] In this case, the gradient descent method can be applied starting from an initial linearization signal. The initial linearization signal is, for example, a frequency comb containing the frequencies of the intermodulation products with randomly chosen amplitudes and phases. In this case, the gradient descent method is applied to a multivariate function whose variables are the amplitudes and phases of the unmodulated pure-carrier signals forming the linearization signal. This optimization step is then performed on all variables simultaneously.

[0045] Alternatively, the modification of the phases and / or amplitudes of the unmodulated pure carrier signals forming the linearization signal is carried out using the Newton-Raphson method.

[0046] Fig. 2 schematically illustrates one embodiment of a radio frequency signal amplification method 100 according to one aspect of the invention. The method 100 is implemented using device 1 according to another aspect of the invention.

[0047] As illustrated in Fig. 2, the method 100 according to one aspect of the invention comprises a step 101 for receiving a radio frequency signal. According to the embodiment illustrated in Fig. 2, the method 100 further comprises a step 102 for determining the frequencies of the pure carrier signals included in a linearization signal. The linearization signal is a sum of unmodulated pure carrier signals of distinct frequencies, these frequencies being the intermodulation product frequencies of the pure carrier signals forming the radio frequency signal.

[0048] In one embodiment, step 102 involves analyzing an amplified radio frequency signal in the absence of the linearization signal to determine the intermodulation products that will form the linearization signal. In another embodiment of step 102, the frequencies of the pure-carrier signals forming the linearization signal are predetermined and stored in a memory element within the processing unit.

[0049] The process 100 further includes a step 103 of determining a compensated radio frequency signal as a linear combination of the radio frequency signal and the linearization signal.

[0050] According to one embodiment, the radio frequency signal is converted to analog during a digital / analog conversion step 104. Similarly, the linearization signal is converted to analog during a digital / analog conversion step 105.

[0051] According to one embodiment, the process 100 further includes a step 105.1 of linear combination of the analog version of the radio frequency signal and the analog version of the linearization signal, so as to obtain an analog version of the compensated radio frequency signal.

[0052] The compensated radio frequency signal is then amplified by a power amplifier in an amplification step 106, so as to provide an amplified radio frequency signal. A portion of the amplified radio frequency signal is taken by a coupler in a sampling step 107 and converted to digital in an analog-to-digital conversion step 108.

[0053] The amplified radio frequency signal sample taken during step 107 and digitized during step 108 is then provided to the computing unit during step 109.

[0054] According to the embodiment illustrated in Fig. 2, the processing unit can then implement a step 110 of modifying the amplitudes and / or phases of the pure carrier signals forming the linearization signal so as to minimize the amplitude of the intermodulation products in the amplified radio frequency signal. In one embodiment, the minimization includes reducing the amplitudes below a predetermined threshold.

[0055] In one embodiment, the predetermined threshold is a reduction in the amplitude of the intermodulation products of at least 40 dB compared to the amplified signal in the absence of the linearization signal. According to this embodiment, the modification step 110 is repeated several times until the reduction of the intermodulation products falls below the predetermined threshold.

[0056] According to one embodiment, modification step 110 includes the implementation of a gradient descent method. In this case, the gradient descent method is performed starting from an initial linearization signal on a multivariate function whose variables are the amplitudes and phases of the pure carrier signals forming the linearization signal. This allows the linearization signal to be optimized over all intermodulation products simultaneously and the output of the power amplifier to be linearized.

[0057] According to one embodiment, the initial linearization signal comprises a sum of carrier signals having frequencies equal to the intermodulation frequencies and with phases and amplitudes chosen randomly.

[0058] According to another embodiment of step 108, the modification of the phases and / or amplitudes of the pure carrier signals forming the linearization signal includes the implementation of a Newton-Raphson type method.

[0059] Figure 3 illustrates a radio frequency signal of the frequency comb type amplified using a state-of-the-art power amplifier. As shown in Figure 4, the amplified signal has the original comb frequencies, F1 and F2, but also exhibits several spurious frequencies or intermodulation products (I1, I2, I3, I4, I5, and I6). The presence of these intermodulation products alters the transmission pattern and may render the amplified radio frequency signal non-compliant with transmission standards.

[0060] Fig. 4 illustrates the same frequency comb F1, F2 amplified using the device according to the invention. In this case, the intermodulation products are greatly reduced, demonstrating the effectiveness of the device and the method according to the invention. Positioning system for a receiving mobile

[0061] Another object of the present invention is a positioning system for a receiving mobile device, said positioning system comprising a device 1 for amplifying a radio frequency signal according to one aspect of the invention. The applicant has developed a positioning system such as that disclosed in patent application EP4323789A1.

[0062] An object of the present invention is a positioning system for at least one receiving mobile, the system comprising, in addition to the mobile, at least two fixed transmitting bases, each transmitting base being configured to emit radio frequency signals, the transmitting bases being synchronized with each other to emit their respective signals, the receiving mobile being configured to receive and process said radio frequency signals and to deduce its position by calculating the time-of-flight difference(s) between the receiving mobile and the transmitting bases, the receiving mobile comprising means for storing position data of the fixed transmitting bases,

[0063] in which each transmitting base is configured to emit a sum of at least two unmodulated pure carrier signals of distinct frequencies, each pure carrier signal being in the form of an unmodulated sustained wave, preferably sinusoidal;

[0064] and the receiving mobile device further includes: - means for measuring, for each given signal frequency and for each respective transmitting base, the phase of the signal consisting of the different signals originating from said base and exhibiting said frequency; and - computing means connected to the measurement means and storage means, and configured to: to apply, for each transmitting base, a high-resolution spectral analysis method such as a Fourier transform on a signal consisting of the different phases and measured amplitudes of the radio frequency signals from said base; to determine, for each transmitting base, from the high-resolution spectral analysis calculated for said base, a time of flight between the receiving mobile and said base; o calculate at least one difference in flight time between the mobile and two transmitting bases, said difference being calculated as the difference between the flight times determined for said bases; o determine the position of the receiving mobile, from the calculated difference in flight time(s) and the position data of the transmitting bases, in which at least one of the transmitting bases includes a device 1 for amplifying a radio frequency signal according to one aspect of the invention, the sum of at least two unmodulated pure carrier signals of distinct frequencies emitted by said transmitting base being a radio frequency signal amplified using the device 1 for amplifying a radio frequency signal. Another object of the present invention is a transmitting base configured to emit a sum of at least two unmodulated pure carrier signals of distinct frequencies, each pure carrier signal being in the form of an unmodulated continuous wave, preferably sinusoidal, the sum of at least two unmodulated pure carrier signals of distinct frequencies emitted by said transmitting base being a radio frequency signal amplified using the device 1 for radio frequency signal amplification.

[0065] The system's use of pure carrier signals in the form of unmodulated sustained waves limits spectral occupancy, thus ensuring very high system sensitivity by minimizing the equivalent noise band. Such signals exhibit minimal spectral occupancy. This results in a mobile receiver positioning system with a long range and low operating cost, functioning equally well outdoors and indoors, and enabling the mobile device itself to position itself precisely.Such an approach, based on the emission of sums of signals with a pure, unmodulated carrier, is not used in prior art positioning and radiolocation systems, particularly because of multipath propagation (rebounds of the transmitted signal arriving at the receiving mobile with a time delay), which is difficult to distinguish from the original line-of-sight signal when such a signal is a continuous, unmodulated wave. The use by the system according to the invention of a high-resolution spectral analysis applied to a signal consisting of the different measured phases and amplitudes of the radio frequency signals allows the receiving mobile to discriminate the reflections of the main signal and thus measure flight times (between the mobile and the base stations) free from multipath errors.Unlike some prior art positioning systems, which apply a Fourier transform to a time-domain signal, the positioning system according to the invention applies a high-resolution spectral analysis to a signal composed of phases and amplitudes of signals at different frequencies. This approach allows the receiving mobile device to distinguish the reflections of the main signal, the latter being the first to arrive at the receiving mobile device (the reflections arriving subsequently). Furthermore, the transmitting bases of the positioning system according to the invention do not transmit any modulated data, unlike many prior art systems. This reduces spectral occupancy and therefore the cost and complexity of the system.

[0066] Advantageously, for each transmitting base station, the frequency difference between the minimum and maximum frequencies of the pure-carrier signals emitted by that base station is greater than 50 MHz. This allows for a reduction in the resolution of the high-resolution spectral analysis, and therefore for improved localization accuracy, typically less than 1 m. The reduced resolution of the Fourier transform then improves the separation or discrimination between the line-of-sight signal from a transmitting base station and the various signal bounces (multipath) on the other. Indeed, such separation or discrimination is possible provided that the resolution of the Fourier transform is sufficiently fine, more precisely, provided that it is less than the time interval separating the main signal (line-of-sight) from the considered bounce.The positioning system according to the invention makes it possible to obtain a location accuracy for the receiving mobile of less than 1 m, even inside buildings or in urban environments, and this without resorting to GPS or GNSS type signals (from the English Global Navigation Satellite System).

[0067] In a preferred mode, each pure-carrier signal emitted by a transmitting base station has a frequency in the very high frequency band, specifically in the range of 30 MHz to 300 MHz. This provides the best compromise between signal penetration inside buildings, minimizing multipath propagation, and the size of the transmitting and receiving antennas. Furthermore, the use of such signals significantly reduces the bandwidth required. The very high frequency band also offers a wide range of options for using pure sinusoidal signals.

[0068] Preferably, fixed transmitting bases are configured to transmit the same number of unmodulated pure carrier signals.

[0069] Advantageously, the fixed transmitting bases are configured to transmit their sums of unmodulated pure carrier signals with a frequency shift, with a predetermined frequency shift between two successive transmitting bases. This allows the receiving mobile device to distinguish the sums of unmodulated pure carrier signals from each of the transmitting bases.

[0070] Preferably, the frequency offset is in the range of 100 Hz to 1 kHz. Such a frequency offset allows sums of unmodulated pure carrier signals to be easily separated by the receiving mobile device, while remaining within the same frequency channel (with a frequency bandwidth of 12.5 kHz, in the very high frequency band). This limits the number of frequency channels occupied, and consequently reduces the system implementation cost.

[0071] According to a particular technical feature of the invention, the fixed transmitting bases are antennas, preferably antennas distributed such that the distance between two adjacent antennas is greater than or equal to 1 km.

[0072] According to another particular technical feature of the invention, the receiving mobile is a chip or an electronic card or even a mobile communication device such as a mobile phone.

[0073] Preferably, each fixed transmitting base is configured to synchronize the unmodulated pure carrier signals emitted by the base with each other.

[0074] By using device 1 to amplify a radio frequency signal in at least one of the positioning system's transmitting bases, it is possible to increase the system's range while maintaining the same transmission frequency. Another advantage of using device 1 to amplify a radio frequency signal in at least one of the positioning system's transmitting bases is the ability to use less linear amplifiers with improved efficiency (resulting in lower losses and reduced heat dissipation). In this case, device 1, according to one aspect of the invention, ensures the amplifier's linearity through signal compensation or predistortion. Method for positioning a receiving mobile

[0075] Another object of the invention is a method for positioning a receiving mobile, implemented by a positioning system according to one aspect of the invention comprising, in addition to the mobile, at least two fixed transmitting bases, at least one of the transmitting bases comprising a device 1 for amplifying a radio frequency signal, each transmitting base being configured to emit radio frequency signals, the transmitting bases being synchronized with each other to emit their respective signals, the receiving mobile comprising means for measuring signal phases, data storage means, and computing means connected to the measurement means and the storage means, the method comprising an initial step of transmitting position data from the fixed transmitting bases to the storage means of the receiving mobile, in which the process further comprises the following steps: - an emission, by each of the transmitting bases, of a sum of at least two unmodulated pure carrier signals of distinct frequencies, each pure carrier signal being in the form of an unmodulated sustained wave, preferably sinusoidal; - reception, by the receiving mobile device, of radio frequency signals from the transmitting bases; - a measurement, by the receiving mobile, for each given signal frequency and for each respective transmitting base, of the phase and amplitude of the signal made up of the different signals from said base and presenting said frequency; - an application, by the receiving mobile and for each transmitting base, of a high-resolution spectral analysis, such as a Fourier transform, on a signal consisting of the different phases and amplitudes measured of the radio frequency signals received from said base; - a determination, by the receiving mobile and for each transmitting base, from the high-resolution spectral analysis calculated for said base, of a time of flight between the receiving mobile and said base; - a calculation, by the receiving mobile, of at least one difference in flight time between the mobile and two transmitting bases, said difference being calculated as the difference between the flight times determined for said bases; - a determination, by the receiving mobile, of its position from the calculated difference(s) in flight time(s) and the position data of the transmitting bases, in which at least one of the sums of at least two unmodulated pure carrier signals of distinct frequencies emitted by one of the transmitting bases is a signal amplified using method 100 according to one aspect of the invention.

Claims

Demands

1. Device (1) for amplifying a radio frequency signal, said radio frequency signal comprising a sum of unmodulated pure carrier signals of distinct frequencies, said device (1) comprising: - a computing unit (11) comprising computing means (11.1) and configured to receive as input the radio frequency signal and determine a compensated radio frequency signal, said compensated radio frequency signal being a linear combination of the radio frequency signal and a linearization signal, said linearization signal comprising a sum of unmodulated pure carrier signals of distinct frequencies, the frequencies of the unmodulated pure carrier signals forming the linearization signal being intermodulation frequencies of the unmodulated pure carrier signals included in the radio frequency signal; - a power amplifier (15), having an input and an output, said power amplifier being configured to receive the compensated radio frequency signal as input, amplify the compensated radio frequency signal and provide an amplified radio frequency signal as output; - a coupler (16) connected to the output of the power amplifier (15) and configured to take a portion of the amplified radio frequency signal at the output of the power amplifier (15), said coupler being further configured to provide the portion taken from the amplified radio frequency signal to the computing unit; the computing means (11.1) of the computing unit (11) being further configured to modify, on the basis of the part of the amplified radio frequency signal taken by the coupler (16), amplitudes and / or phases of the pure carrier signals forming the linearization signal.

2. Device (1) according to the preceding claim wherein the computing means (11.1) are configured to modify amplitudes and / or phases of pure carrier signals included in the linearization signal so as to minimize a function of the power of the signals having intermodulation frequencies in the portion of the amplified radio frequency signal taken by the coupler.

3. Device (1) according to any one of the preceding claims further comprising: - a first digital / analog converter (12) configured to provide an analog version of the radio frequency signal from a digital version of the radio frequency signal, said digital version of the radio frequency signal being provided by the computing unit (11); - a second digital / analog converter (13) configured to provide an analog version of the linearization signal from a digital version of the linearization signal, said digital version of the linearization signal being provided by the computing unit (11); - an analog / digital converter (17) connected to the coupler (16) and to the calculation unit (11), the analog / digital converter (17) being configured to receive as input the part of the amplified radio frequency signal taken by the coupler (16) and to provide the calculation unit (11) with a digital version of the part of the amplified radio frequency signal taken by the coupler (16); - a power combiner (14) configured to receive as input the analog version of the radio frequency signal and the analog version of the linearization signal and provide as output an analog version of the compensated radio frequency signal.

4. Device (1) according to any one of the preceding claims further comprising means for measuring the amplitudes and / or phases of signals having intermodulation frequencies in the portion of the amplified radio frequency signal taken by the coupler (16).

5. Device (1) according to any one of the preceding claims wherein the computing unit (11) is further configured to determine the frequencies of the pure carrier signals included in the linearization signal from the radio frequency signal and the amplified radio frequency signal.

6. Device (1) according to any one of the preceding claims wherein the computing means are configured to modify phases and / or amplitudes of the pure carrier signals forming the gradient descent linearization signal on all the pure carrier signals forming the linearization signal at once.

7. Transmitting base for a positioning system for a receiving mobile comprising the device according to any one of claims 1 to 6.

8. Positioning system for a receiving mobile comprising a transmitting base according to the preceding claim.

9. A method (100) for amplifying a radio frequency signal, said radio frequency signal comprising a sum of unmodulated pure carrier signals of distinct frequencies, said method comprising the following steps: - Determination (103), using a computing unit comprising computing means, of a compensated radio frequency signal, said compensated radio frequency signal being a linear combination of the radio frequency signal and a linearization signal, said linearization signal being a sum of unmodulated pure carrier signals of distinct frequencies, the frequencies of the unmodulated pure carrier signals forming the linearization signal being intermodulation frequencies of the unmodulated pure carrier signals included in the radio frequency signal; - amplification (106), by a power amplifier, of the compensated radio frequency signal so as to provide an amplified radio frequency signal; - sampling (107), by a coupler and at the output of the power amplifier, of a part of the amplified radio frequency signal; - supply (109) of the portion taken from the amplified radio frequency signal to the computing unit; - modification (110) by the calculation means of the calculation unit and on the basis of the part of the amplified radio frequency signal of the amplitudes and / or phases of the pure carrier signals forming the linearization signal.

10. A method (100) according to the preceding claim wherein, during the modification step (110), the amplitudes and / or phases of the pure carrier signals forming the linearization signal are modified so as to minimize a function of the power of the signals having intermodulation frequencies in the portion of the amplified radio frequency signal taken by the coupler.

11. A method (100) according to claim 9 or claim 10 further comprising: - A digital / analog conversion of the radio frequency signal (104); - A digital / analog conversion of the linearization signal (105); - An analog / digital conversion (108) of the amplified radio frequency signal portion taken by the coupler at the output of the power amplifier. - A linear combination (105.1) of the analog version of the radio frequency signal and the analog version of the linearization signal to provide an analog version of the compensated radio frequency signal.

12. Method (100) according to any one of claims 9 to 11 further comprising a step of determining the frequencies of the pure carrier signals included in the linearization signal (102) from the radio frequency signal and the amplified radio frequency signal.

13. Method (100) according to the preceding claim wherein the intermodulation frequency determination step (102) includes radio frequency signal amplification in the absence of the linearization signal.

14. A method (100) according to any one of claims 9 to 13 in which the modification step (110), by the computing means of the computing unit and on the basis of the portion of the amplified radio frequency signal, of the amplitudes and / or phases of the pure carrier signals included in the linearization signal comprises a measurement of the amplitudes and / or phases of the signals having intermodulation frequencies in the portion of the amplified radio frequency signal taken by the coupler.

15. A method (100) according to the preceding claim in which the modification (110) of the phases and / or amplitudes of the pure carrier signals included in the linearization signal is carried out by gradient descent on all the pure carrier signals forming the linearization signal at once.

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