Data processing device configured to process samples of a radio signal

Abstract

Examples present a method for processing samples of an amplitude modulated or frequency modulated radio signal, the method comprising: applying, for a specific sample of the modulated radio signal, a matrix of complex coefficients adapted to correct a distortion introduced by a communication channel on the specific sample, so as to obtain a specific corrected sample of the modulated radio signal; determining, for the specific corrected sample of the modulated radio signal, a distortion correction error; demodulating the radio signal in order to obtain a demodulated radio signal;anddetermining, for the specific sample of the demodulated radio signal, an attenuation coefficient to be applied from the distortion correction error determined for the specific sample on the modulated radio signal, the attenuation coefficient being proportional to the distortion correction error. Abstract figure: [Fig. 2];

Description

Title of the invention: Data processing device configured to process samples of a radio signal Technical field

[0001] The present disclosure relates to the field of radio signal reception. Prior art

[0002] The reception of a radio signal, insofar as it is a wireless telecommunication, is subject to multipath problems. In this case, the signal received at the receiver is disturbed by signals originating from parasitic reflections of the transmitted signal.

[0003] In the context of frequency or amplitude modulated radio signals, solutions for reducing these disturbances are known and are based on the characteristics of these modulations.

[0004] As regards frequency modulations, the received signal is assumed to be of constant amplitude. Existing solutions for reducing the disturbance of the received signal are therefore based on a comparison of the amplitude variations of the received signal with a determined amplitude variation threshold, and depending on the comparison, a suppression of the signal (generally known as “blanking”).

[0005] As regards amplitude modulations, the received signal is assumed to be of constant frequency. Consequently, existing solutions for reducing the disturbance of the received signal are based on a comparison of the frequency variations of the received signal with a determined frequency variation threshold, and depending on the comparison, a suppression of the signal.

[0006] For these two types of modulation, the solutions therefore consist of comparing the signal to a threshold, whether it is a frequency threshold or an amplitude threshold, and of suppressing the signal according to this comparison.

[0007] It is understood, however, that the threshold value can be difficult to define. Indeed, it is not necessarily because a part of the signal is higher than the set threshold that this part of the signal is not audible to a listener. Removing this part of the signal can therefore be more problematic for the listener than delivering it to him, even if noisy. Furthermore, when it is decided to remove the signal, the question of the signal removal time also arises. Indeed, in a case where the signal does not fall below a defined removal threshold for a time interval of several seconds, let alone several minutes, removing the signal

[0008]

[0009]

[0010]

[0011]

[0012]

[0013]

[0014] during this time interval is not a satisfactory solution for the listener who will no longer have any sound during the time interval. This disclosure improves this situation. Summary In this regard, a method for processing samples of an amplitude-modulated or frequency-modulated radio signal is proposed, the method comprising: - an application, for a specific sample of the modulated radio signal, of a matrix of complex coefficients adapted to correct a distortion introduced by a communication channel on the specific sample, so as to obtain a specific corrected sample of the modulated radio signal; - a determination, for the specific corrected sample of the modulated radio signal, of a distortion correction error; - demodulation of the radio signal in order to obtain a demodulated radio signal; and - a determination, for the specific sample of the demodulated radio signal, of an attenuation coefficient to be applied from the distortion correction error determined for the specific sample on the modulated radio signal, the attenuation coefficient being inversely proportional to the distortion correction error. Optionally, the method further comprises applying the corresponding determined attenuation coefficient to the specific sample of the demodulated radio signal. Optionally, the method further comprises limiting the attenuation coefficient to be applied to the specific sample of the demodulated radio signal so that when the attenuation coefficient to be applied is less than a minimum attenuation coefficient, the attenuation coefficient applied to the specific sample corresponds to the minimum attenuation coefficient. Optionally, the distortion correction error is determined as corresponding to the error to be minimized by a signal equalization algorithm applied to the modulated radio signal. Optionally, the distortion correction error is determined as corresponding to the error to be minimized of a stochastic gradient algorithm applied in order to minimize a cost function of the modulated radio signal equalization algorithm. Optionally, the radio signal is a frequency modulated signal and the distortion correction error is determined to correspond to the error to be minimized by a constant modulus algorithm.

[0015] Optionally, the distortion correction error is determined as corresponding to the error to be minimized of a stochastic gradient algorithm applied in order to minimize a cost function of the constant modulus algorithm.

[0016] Optionally, the attenuation coefficient is determined from the following equation:

[0017] E E+ 71(¾)2

[0018] in which G(k) corresponds to the attenuation coefficient to be applied to the sample k of the received signal, ô corresponds to an adjustment gain, VJ(W^) corresponds to the distortion correction error for sample k, and £ corresponds to a constant allowing the impact of the distortion correction error on the attenuation coefficient to be modulated

[0019] Optionally, the distortion correction error VJ(VV\ ) is determined from the following equation:

[0020] vj ( Wk ) 2E {( | y J 2 -1 ) )7¾}

[0021] in which E corresponds to the mathematical expectation, corresponds to the sample k of the modulated radio signal, 5'k corresponds to the sample x£ of the modulated radio signal corrected by the application of the matrix of complex coefficients determined by the constant modulus algorithm, and yk corresponds to the complex conjugate of

[0022] Optionally, the radio signal is an amplitude modulated radio signal and the distortion correction error is determined to correspond to the error to be minimized by a constant phase algorithm.

[0023] The application also relates to a data processing device configured to implement any of the methods presented in the present disclosure.

[0024] The application further relates to a computer program product comprising instructions for implementing any of the methods described in the present disclosure when this program is executed by a processor.

[0025] Finally, the application relates to a non-transitory recording medium readable by a computer on which is recorded a program for implementing any one of the methods described in the present disclosure when this program is executed by a processor. Brief description of the drawings

[0026] Other features, details and advantages will become apparent upon reading the des- detailed description below, and to the analysis of the attached drawings, on which: Fig. 1

[0027] [Fig. 1] represents an example of a data processing device suitable for implementing a method for processing samples of an amplitude-modulated or frequency-modulated radio signal. Fig. 2

[0028] [Fig.2] represents an example of a method for processing samples of an amplitude-modulated or frequency-modulated radio signal. Description of the embodiments

[0029] The present application relates to a method for processing samples of an amplitude-modulated or frequency-modulated radio signal.

[0030] In a manner known to those skilled in the art, a radio signal is a wireless telecommunications signal delivered by a transmitter via a transmission chain and received by recipients, distant from the transmitter, via a reception chain. In particular, the radio signal can be modulated in frequency (FM radio) or in amplitude (AM radio) to be transmitted to its recipients via a communication channel. The communication channel introduces disturbances that the reception chain of the recipients strives to reduce, in particular by removing certain parts of the signal where appropriate.

[0031] The method presented in the present disclosure makes it possible in particular, as a replacement for the suppression of certain parts of the radio signal proposed by the prior art, to apply an attenuation coefficient to at least one specific sample of the radio signal and advantageously to each of the samples of the radio signal. Consequently, no part of the radio signal is suppressed, the received signal is simply attenuated by the attenuation coefficient as a function of the samples of the signal and in particular as a function of an error associated with these samples and determined before the demodulation of the signal as explained in detail below. Therefore, the method presented makes it possible to deliver to the listener a radio signal without discontinuity, more pleasant to listen to than the radio signals delivered by the methods of the prior art which may comprise completely suppressed signal parts.

[0032] The method according to the present disclosure may for example be implemented by a data processing device 10 shown in [Fig.l]. The data processing device may in particular be part of the radio signal reception chain. The data processing device 10 may for example be on board a vehicle.

[0033] As illustrated in [Fig.l], the data processing device 10 comprises a computer 11 adapted to implement the processing described below on the data of the radio signal and a memory 12 storing the code instructions executed by the computer 11. The computer 11 can for example be of the processor, microprocessor, microcontroller, FPGA type, etc. The memory 12 can for example comprise a ROM (Read-Only Memory), a RAM (Random Access Memory), an EEPROM (Electrically Erasable Programmable Read-Only Memory) or any other type of suitable storage means. The memory 12 can for example comprise optical, electronic or magnetic storage means. The memory 12 can in particular store the samples of the radio signal.

[0034] With reference to [Fig.2], an example of a method 100 for processing samples of an amplitude-modulated or frequency-modulated radio signal is presented below.

[0035] The method 100 comprises an operation 110 of applying, for a specific sample of the modulated radio signal, a matrix of complex coefficients adapted to correct a distortion introduced by a communication channel on the specific sample, so as to obtain a specific corrected sample of the modulated radio signal.

[0036] In the reception chains known from the prior art, the application of a matrix of complex coefficients to each sample of the modulated radio signal in order to reduce the disturbances of the communication channel is already carried out. This is a conventional implementation of a channel equalization algorithm (known under the English term "equalization") modifying the frequency response of the radio signal by applying a matrix of complex coefficients of a filter, for example a finite impulse response (FIR) filter, to correct the distortions of the signal introduced by the communication channel.

[0037] In examples in which the radio signal is frequency modulated, an iterative algorithm referred to in the literature as a "constant modulus algorithm", known to those skilled in the art, can be implemented to determine the matrix of complex coefficients suitable for correcting the distortion introduced by the communication channel on the specific sample. More specifically, the principle of frequency modulation ensures that the transmitted radio signal has a constant amplitude. Therefore, constant modulus algorithms have been developed to iteratively determine the real and imaginary parts of the complex coefficients to be applied to the complex vector corresponding to the received FM radio signal, in order to achieve a combination that can attenuate the electromagnetic interference present in the radio signal. FM. The main constraint of these algorithms is to ensure, after calculating the complex coefficients, a substantially constant phase in the filtered radio signal within the reception chain. An example of such an algorithm is described in particular in the French application published under number FR2710221.

[0038] In examples in which the radio signal is amplitude modulated, an iterative algorithm referred to in the literature as a "Constant Phase Algorithm", known to those skilled in the art, may be implemented to determine the matrix of complex coefficients suitable for correcting the distortion introduced by a communication channel on the specific sample. The principle of amplitude modulation ensures that the transmitted radio signal has a constant phase. Therefore, calculation algorithms, referred to as CPA algorithms, have been developed to determine, iteratively, the real and imaginary parts of the complex coefficients to be applied to the complex vector corresponding to the received AM radio signal, with a view to producing a combination making it possible to attenuate the electromagnetic interference present in the FM radio signal.The main constraint of these algorithms is to ensure, after calculation, a substantially constant phase in the filtered radio signal in the reception chain. Such an algorithm is notably described in the French application published under number FR 3067191 and filed by the Applicant.

[0039] As illustrated by [Fig.l], the method 100 comprises an operation 120 of determining, for the specific corrected sample of the modulated radio signal, a distortion correction error. In this case, the signal equalization algorithms, and in particular the constant modulus or constant phase algorithms, apply to determining a matrix of complex coefficients adapted to minimize a cost function reflecting a distortion error of the communication channel. These algorithms are iterative and rely in particular, at each iteration, on a distortion correction error determined at the end of the previous iteration. Indeed, the complex coefficients of the matrix are determined so as to correct the distortion error of the communication channel. However, at each iteration, a distortion correction error remains after the coefficients have been applied.This distortion correction error can thus be used, during the following iteration, in order to modify the complex coefficients of the coefficient matrix to be applied in order to converge towards a minimization of this error.

[0040] As illustrated by [Fig.l], the method 100 comprises an operation 130 of determining the radio signal in order to obtain a demodulated radio signal. Depending on the modulation chosen, the radio signal is demodulated to allow its processing.

[0041] As illustrated by [Fig.l], the method 100 comprises an operation 140 of determining mination, for the specific sample of the demodulated radio signal, of an attenuation coefficient to be applied. The attenuation coefficient is applied from the distortion correction error determined for the specific sample on the modulated radio signal. It is proportional to the distortion correction error determined for the specific sample. In this way, the greater the distortion correction error, the greater the calculated attenuation coefficient, and therefore the more the signal is attenuated. The attenuation coefficient can for example be between 0 and 1.

[0042] Finally, in examples, and as illustrated by [Fig. 1], the method 100 may comprise an operation 150 of applying the corresponding determined attenuation coefficient to the specific sample of the demodulated radio signal.

[0043] Consequently, no part of the radio signal is deleted, the received signal is more or less attenuated by the attenuation coefficient depending on the samples of the signal and in particular depending on the distortion correction error associated with these samples. As explained previously, the method presented therefore makes it possible to deliver to the listener a radio signal without discontinuity unlike the radio signals delivered by the methods of the prior art which may comprise completely deleted signal parts. Furthermore, the method proposes to reuse the distortion correction error, already calculated on the signal modulated by the channel equalization algorithm, to modulate this attenuation coefficient, so that the method presented can be implemented without significant modification of the signal reception chain, in particular by using a software block already implemented in this reception chain.

[0044] In examples, the distortion correction error may be determined to correspond to the error to be minimized by a signal equalization algorithm applied to the modulated radio signal. In particular, in these examples, the distortion correction error may be determined to correspond to the error to be minimized by a stochastic gradient algorithm applied to minimize a cost function of the radio signal equalization algorithm.

[0045] In particular examples in which the radio signal is frequency modulated, the distortion correction error may be determined to correspond to the error to be minimized by a constant modulus algorithm. In particular, in these examples, the distortion correction error may be determined to correspond to the error to be minimized by a stochastic gradient algorithm applied to minimize a cost function of the constant modulus algorithm.

[0046] In examples, the cost function to be minimized of a constant modulus algorithm is as follows: P» 47 ! J(w)=Ej(|y / -l))

[0048] in which J(w) corresponds to the cost function, E corresponds to the mathematical expectation, and corresponds to the sample xk of the modulated radio signal corrected by the application of the matrix of complex coefficients determined by the constant modulus algorithm.

[0049] Thus, = wHxk with wH corresponding to the matrix of complex coefficients to be applied to the sample xk of the radio signal.

[0050] This cost function can be minimized by a stochastic gradient algorithm configured to determine the complex coefficient matrix Hï+i of sample k+1 from the following equation: [005i] =

[0052] in which 1 corresponds to the matrix of complex coefficients of the sample k+1, wk corresponds to the matrix of complex coefficients of the sample determined for sample k, VJÇIVJ corresponds to the distortion correction error for sample k, and

[0053] corresponds to a learning rate chosen according to the speed, stability and / or convergence accuracy of the stochastic gradient algorithm.

[0054] In particular, the distortion correction error VJ( Wk ) for sample k can be obtained from the following equation:

[0055] VJ(Wk) = 2£ {(| vj2 - 1) yy]

[0056] in which xk corresponds to the sample k of the modulated radio signal, corresponds to the sample xk of the modulated radio signal corrected by the application of the matrix of complex coefficients determined by the constant modulus algorithm, E corresponds to the mathematical expectation, and yk corresponds to the complex conjugate of

[0057] Thus, in these examples, the attenuation coefficient G(k) of sample k determined from the corresponding distortion correction error V JfHA) can be obtained from the following equation:

[0058] g / ...........,...... / d

[0059] in which G(k) corresponds to the attenuation coefficient to be applied to the sample k of the received signal, 6 corresponds to an adjustment gain, VJ(W^) corresponds to the distortion correction error for sample k, and E corresponds to a constant allowing the impact of the distortion correction error on the attenuation coefficient to be modulated.

[0060] In examples in which the radio signal is amplitude modulated, the distortion correction error may be determined to correspond to the error to be minimized by a constant phase algorithm. In particular, the distortion correction error may be determined to correspond to the error to be minimized by a stochastic gradient algorithm applied to minimize a cost function of the constant phase algorithm.

[0061] In examples, and as illustrated by [Fig.l], the method 100 may comprise an operation 145 of limiting the attenuation coefficient to be applied to the specific sample of the demodulated radio signal so that:

[0062] when the attenuation coefficient to be applied is less than a minimum attenuation coefficient, the attenuation coefficient applied to the specific sample corresponds to the minimum attenuation coefficient. These examples therefore make it possible to limit a minimum value of the attenuation coefficient to avoid excessive attenuation of the signal which could be detrimental to the listener. In examples, the attenuation coefficient can therefore be between the minimum attenuation coefficient and 1.

[0063] The present disclosure further provides a computer program product comprising instructions for implementing any of the methods described in this document when this program is executed by a processor.

[0064] Finally, the present disclosure provides a non-transitory computer-readable recording medium on which is recorded a program for implementing any of the methods described herein when this program is executed by a processor.

[0065] The method according to the present disclosure therefore makes it possible to modulate the attenuation applied to at least one sample and advantageously to each sample of the radio signal as a function of the distortion correction error calculated during the equalization algorithm. It is therefore no longer necessary to define signal suppression threshold values ​​and the question of the signal suppression time no longer arises. Consequently, the method presented makes it possible to deliver to the listener a radio signal without discontinuity, unlike the radio signals delivered by the methods of the prior art which may comprise completely suppressed signal parts.

Claims

Claims

1. Method for processing samples of an amplitude-modulated or frequency-modulated radio signal, the method comprising: - equalization by application (110), for a specific sample of the modulated radio signal, of a matrix of complex coefficients adapted to correct a distortion introduced by a communication channel on the specific sample, so as to obtain a specific corrected sample of the modulated radio signal; - determination (120), before demodulation of the modulated radio signal and for the specific corrected sample of the modulated radio signal, of a distortion correction error; - demodulation (130) of the radio signal in order to obtain a demodulated radio signal;- a determination (140), for the specific sample of the demodulated radio signal, of an attenuation coefficient to be applied from the distortion correction error determined for the specific sample on the modulated radio signal, the attenuation coefficient being such that the greater the distortion correction error, the greater the attenuation applied by the attenuation coefficient, - an application (150) of the corresponding determined attenuation coefficient on the specific sample of the demodulated radio signal.;

2. Method according to any one of the preceding claims, further comprising: - a limit (145) of the attenuation coefficient to be applied to the specific sample of the demodulated radio signal so that when the attenuation coefficient to be applied is less than a minimum attenuation coefficient, the attenuation coefficient applied to the specific sample corresponds to the minimum attenuation coefficient.

3. A method according to any preceding claim, wherein the distortion correction error is determined to correspond to the error to be minimized by a signal equalization algorithm applied to the modulated radio signal.

4. Method according to the preceding claim, in which the distortion correction error is determined as corresponding to the error to be minimized of a stochastic gradient algorithm applied in order to minimize a cost function of the modulated radio signal equalization algorithm.

5. A method according to any preceding claim, wherein: - the radio signal is a frequency modulated signal; and - the distortion correction error is determined as corresponding to the error to be minimized by a constant modulus algorithm.

6. Method according to the preceding claim, in which: - the distortion correction error is determined as corresponding to the error to be minimized of a stochastic gradient algorithm applied in order to minimize a cost function of the constant modulus algorithm.

7. Method according to any one of claims 5 or 6, in which the attenuation coefficient is determined from the following equation: JXôf— \ / \£+VW / in which G(k) corresponds to the attenuation coefficient to be applied to sample k of the received signal, ô corresponds to an adjustment gain, VJ(W*) corresponds to the distortion correction error for sample k, and E corresponds to a constant making it possible to modulate the impact of the distortion correction error on the attenuation coefficient.

8. Method according to the preceding claim, in which the distortion correction error VJ(W^) is determined from the following equation: VJ( Wt) =2E{(|yJ2-1)¾¾) in which E corresponds to the mathematical expectation, xk corresponds to the sample k of the modulated radio signal, corresponds to the sample xk of the modulated radio signal corrected by the application of the matrix of complex coefficients determined by the constant modulus algorithm, and yk corresponds to the complex conjugate of

9. A method according to any one of claims 1 to 4, wherein: - the radio signal is an amplitude modulated signal; and - the distortion correction error is determined as corresponding to the error to be minimized by a constant phase algorithm.

10. A data processing device (10) configured to carry out any one of the methods according to claims 1 to 9.

Images