Radiofrequency module for detecting a user, and corresponding detection method.

Abstract

Radiofrequency module (1) intended to be embedded in a motor vehicle, and comprising: a transmission and reception module (10), comprising an antenna (3) for the transmission of a pulse-modulated radiofrequency signal called transmitted signal (101) and the reception of a received signal (102) returning to the antenna (3), and a detection circuit (2) for carrying out at least one frequency demodulation of the received signal so as to provide signals I(t) and Q(t) corresponding to the in-phase and quadrature-phase components of a frequency-demodulated received signal; a signal extraction module (6), for extracting a first contribution from the frequency-demodulated received signal, corresponding to internal reflections of the transmitted signal (101) inside the antenna (3);and a first signal processing module (7), for receiving said first contribution, and for deducing therefrom information relating to a user presence using a comparison with a predetermined threshold. Figure for the abstract: Fig 1;

Description

Title of the invention: Radiofrequency module for detecting a user, and corresponding detection method. Technical field

[0001] The invention relates to the field of detecting presence around a motor vehicle.

[0002] The presence detection information is intended to be used for controlling, from the outside, a function such as locking and / or unlocking an opening of the vehicle, or opening and / or closing the opening, or any other function to be controlled from outside the vehicle. Previous techniques

[0003] It has become common practice, in recent years, to provide a sensor for the presence of a user's hand, located in the handle of a motor vehicle opening, in particular in a side door handle, front trunk handle or rear trunk handle.

[0004] Such presence sensors are generally capacitive type sensors, the limitations of which are now well known. These include problems of false detection when the sensor is exposed to water.

[0005] Furthermore, radiofrequency type sensors are also known, this time in the field of vehicle access, for the location and / or authentication of a user by exchanging data with a user terminal, such as an on-board access key or card or a smartphone equipped with a dedicated application.

[0006] It is recalled that a radiofrequency signal is an electromagnetic signal comprising a carrier with a frequency of, for example, between 3 kHz and 300 GHz. The frequency of this carrier is generally between 5 and 20 GHz in automotive applications.

[0007] The radiofrequency signal may be pulse-modulated, i.e. amplitude-modulated to form so-called radiofrequency pulses, i.e. whose carrier frequency belongs to the radiofrequency spectrum. The use of this type of signal makes it possible in particular to determine a distance between a target and a signal transmission / reception device.

[0008] Preferably, the pulse-modulated radiofrequency signal is a signal modulated according to the modulation technique known as “UWB”, for “Ultra Wide Band”. This modulation technique is based on the transmission of pulses of very short duration, preferably less than one nanosecond, and over a wide frequency spectrum.

[0009] An objective of the present invention is to provide a device and a method for presence detection, to detect the presence of a user in the immediate vicinity of a motor vehicle, and making it possible to overcome at least some of the disadvantages of capacitive type solutions. Statement of the invention

[0010] The subject of the invention is a radiofrequency module intended to be installed in a motor vehicle, and comprising:

[0011] a transmission and reception module comprising a detection circuit and an antenna, the antenna being configured to carry out the transmission of a pulse-modulated radiofrequency signal called the transmitted signal and the reception of a received signal returning to the antenna, and the detection circuit being configured to carry out at least one frequency demodulation of the received signal so as to provide signals I(t) and Q(t) corresponding respectively to the in-phase and quadrature-phase components of a frequency-demodulated received signal;

[0012] a signal extraction module, configured to extract a first contribution from the frequency-demodulated received signal, said first contribution corresponding to internal reflections of the signal transmitted inside the antenna.

[0013] The radiofrequency module according to further comprises a first signal processing module, configured to receive said first contribution as input, and to deduce therefrom information relating to a user presence using a comparison between an amplitude of a signal relating to said first contribution and a predetermined threshold.

[0014] In particular, the first signal processing module is configured to receive said first contribution as input, and to deduce therefrom information relating to a user presence when at least one predetermined condition is verified, the at least one predetermined condition including the amplitude of a signal corresponding to said first contribution greater than the predetermined threshold.

[0015] We speak of a signal corresponding to said first contribution, to designate said first contribution, or, where appropriate, the signal resulting from filtering operations(s) and / or offset compensation on said first contribution.

[0016] The signal extraction module can also extract a second contribution, distinct from said first contribution, used for at least one other application such as user terminal localization or gesture detection.

[0017] In use, the detection of a user's presence is intended to activate, from outside the vehicle, a determined function of the vehicle, for example locking and / or unlocking an opening, opening and / or closing an opening, lowering and / or raising electric windows, etc.

[0018] A user wishing to activate such a function affixes at least part of the hand against an external surface of the vehicle, in view of the antenna. This presence of the hand against the antenna results in a modification of the impedance of the antenna, and therefore a modification of the impedance adaptation between the impedance of the antenna and the impedance of a detection circuit connected to the antenna.

[0019] The modification of the impedance adaptation results in a variation in the amplitude of a part of the signal received by the detection circuit, corresponding to the internal reflections in the antenna. By extracting this part of the received signal, called here the first contribution of the received signal, and by comparing its amplitude with a predetermined threshold, it is thus possible to determine the presence or absence of a hand against the antenna.

[0020] The invention thus makes it possible to use a radiofrequency module as a presence sensor, and in a very simple manner.

[0021] The invention also makes it possible to pool resources with a radiofrequency module, in particular a UWB module, already present in the vehicle for other functions (for example for the location or authentication of a user by communication with a user terminal as described in the introduction, or for the detection of a gesture by receiving a signal reflected on a target moving relative to the vehicle). In particular, the first contribution of the received signal is used to implement presence detection, while a second contribution of the received signal can be used for location, authentication and / or gesture detection.

[0022] Traditionally, with UWB modules according to the prior art, it is not possible to identify the pressure of a hand and / or a finger on a defined area, as would be possible with a capacitive sensor. This is due to the lack of resolution of the distance measurement (15 cm, for a conventional sampling period of one nanosecond) and the angle measurement (around 5°).

[0023] The invention proposes a solution, based on the exploitation, in an original manner, of a part of the received signal that one usually seeks to filter in order to free oneself from it.

[0024] Advantageously, the invention thus proposes replacing a capacitive type presence sensor with an ultra-wideband sensor already present on the vehicle, and modified to also offer a presence detection function and form a radiofrequency module according to the invention.

[0025] Advantageously, the radiofrequency module according to the invention is configured to operate in “radar” mode, the received signal then comprising the reflection on a target of the transmitted signal. In addition or as a variant, the radiofrequency module according to the invention is configured to operate in “ranging” mode, the received signal then comprising a signal transmitted by a terminal in response to the reception of the signal issued.

[0026] Advantageously: - the transmission and reception module is configured to transmit a transmitted signal consisting of periodic radiofrequency pulses, the received signal consisting of elementary signals received each associated with a respective one of the transmitted radiofrequency pulses, - the transmission and reception module is further configured to carry out time sampling of the received signal or of the signals I(t) and Q(t), so as to obtain sampled data I(ti) and Q(ti) relating to a plurality of time windows, the time windows being distributed over time ranges each associated with a respective one of the elementary signals received and each having as its origin an instant of emission of the corresponding emitted radiofrequency pulse.

[0027] The signal extraction module may be configured to extract said first contribution using a selection of time windows of interest, based on a deviation at the origin between the time windows of interest and the origin of the corresponding time range.

[0028] In a particularly advantageous manner, the signal extraction module is configured to calculate an amplitude of the frequency-demodulated received signal, using the sampled data I(ti) and Q(ti), and to extract the amplitude values ​​relating, for each of said time ranges, to the first sampling window from the origin of said time range.

[0029] Advantageously, the first signal processing module is configured to determine the presence of a user when said amplitude of a signal relating to said first contribution is greater than the predetermined threshold for a duration greater than a predetermined duration threshold.

[0030] The transmitted signal may be an ultra-wideband radio frequency signal.

[0031] In an advantageous embodiment: - the signal extraction module is further configured to extract a second contribution from the frequency-demodulated received signal, said second contribution corresponding to the reflection of the transmitted signal on a target external to the radiofrequency module, or to a secondary signal radiated by a user terminal in response to the reception of the transmitted signal; and - the radiofrequency module further comprises a second signal processing module, configured to receive said second contribution as input and to deduce therefrom at least one piece of information from among a target location, a gesture made by a target, or a user terminal authentication code.

[0032] Another object of the invention is a motor vehicle comprising a radiofrequency module as described above, the antenna of said module being located in a handle of an opening of the motor vehicle or in a structural side pillar of the motor vehicle, in particular a structural vertical pillar located between a front side door and a rear side door, or behind a decorative element located at the front or rear of the vehicle.

[0033] The antenna may be arranged to extend along an exterior surface of the motor vehicle, the direction of transmission of the antenna being directed from the interior of the vehicle to the exterior of the vehicle.

[0034] Another object of the invention is a presence detection method implemented in a radiofrequency module according to the invention, and comprising the following steps:

[0035] a / transmission of a pulse-modulated radiofrequency signal forming said transmitted signal, and reception of the received signal consisting of received elementary signals each associated with a respective pulse of the transmitted signal, b / frequency demodulation of the received signal, so as to provide signals I(t) and Q(t) corresponding respectively to the in-phase and quadrature-phase components of a frequency-demodulated received signal; c / extraction of a first contribution from the received signal demodulated in frequency, said first contribution corresponding to internal reflections of the signal emitted inside the antenna, d / comparison between the amplitude of a signal relating to said first contribution and a predetermined threshold (SE), and detection of the presence of a user, if said amplitude is greater than the predetermined threshold (SE). Advantageously, the step of detecting the presence of a user is carried out when said amplitude is greater than the predetermined threshold for a duration greater than a predetermined duration threshold.

[0036] Preferably, the method comprises the following steps: - the received signal or said signals I(t) and Q(t) are sampled in time, so as to obtain the sampled data I(ti) and Q(ti) relating to a plurality of time windows, the time windows being distributed over time ranges each associated with a respective one of the elementary signals received and each having as its origin an instant of emission of the corresponding emitted radiofrequency pulse; - we calculate an amplitude of the received signal demodulated in frequency, using the sampled data I(ti) and Q(ti); and - the amplitude values ​​relating, for each of said time ranges, to the first sampling window from the origin of said time range are extracted. Brief description of the drawings

[0037] Other aims, characteristics and advantages of the invention will appear on reading the following description, given solely by way of non-limiting example and made with reference to the appended drawings in which:

[0038] - figure [Fig.l] illustrates the main elements of a radiofrequency module according to the invention,

[0039] - Figure [Fig.2] is a graph illustrating the signal received by the radio module frequency, when a user's thumb comes to rest and then moves away three times from a support area in relation to the antenna of the radiofrequency module,

[0040] - Figure [Fig.3] is a graph illustrating the signal of [Fig.2], after deletion background noise,

[0041] - Figure [Fig.4] is a graph illustrating a portion of the signal illustrated in [Fig.3], associated with a predetermined sampling window index,

[0042] - Figure [Fig.5] is a graph illustrating the signal of [Fig.4], after application of a low-pass filter,

[0043] - Figure [Fig.6] is a graph illustrating the result of the comparison between the signal of [Fig.5] and a predetermined threshold, and

[0044] - figure [Fig.7] illustrates the main steps of a detection method according to the invention. Detailed description

[0045] [Fig.l] illustrates a radiofrequency module 1 according to the invention.

[0046] In use, the radiofrequency module 1 is integrated into a motor vehicle, and located: - in a handle of an opening of the motor vehicle or - in a structural side pillar of the motor vehicle, in particular a structural vertical pillar located between a front side door and a rear side door, or - behind a decorative element located at the front or rear of the vehicle.

[0047] According to the invention, the radiofrequency module 1 is configured to perform presence detection. When it detects the presence of a user, the radiofrequency module 1 generates a presence detection signal, which it sends to an ancillary device configured to activate a given function of the vehicle, in particular a function of locking and / or unlocking an opening of the vehicle or a function of opening and / or closing the opening and / or a function of raising and / or lowering an electric window of the vehicle.

[0048] Advantageously, in addition to a presence detection function, the radiofrequency module 1 also serves to implement bidirectional communication with a user terminal, for the authentication or location of a user terminal. Such a user terminal may be a key or an on-board access card or a smartphone. In addition or as a variant, the radio frequency module 1 is also used to implement gesture detection for controlling a second function associated, for example, with access to the vehicle.

[0049] The radiofrequency module 1 comprises a transmission and reception module 10, also called a transmitter (“transceiver” in English).

[0050] The transmission and reception module 10 is configured for the transmission and reception of UWB signals (English acronym for “Ultra Wide Band”).

[0051] The transmission and reception module 10 comprises a detection circuit 2 and an antenna 3.

[0052] Antenna 3 is configured to perform: - the emission of a radiofrequency signal emitted 101, from an electrical signal 4 generated at the level of the detection circuit 2, and - the reception of a received signal 102, converted into an electrical signal 5 and brought to the detection circuit 2.

[0053] In [Fig. 1], and for reasons of readability of the figure, the received signal 102 has been represented as coming from the environment external to the transmission and reception module. Nevertheless, and as detailed below, the received signal 102 also comprises a component which corresponds to internal reflections on the antenna 3.

[0054] Advantageously, the transmission and reception module 10 also comprises an adaptation circuit, not shown, arranged between the antenna 3 and the detection circuit 2. Such an adaptation circuit can be formed by a progressive variation in a thickness of the conductive tracks on a printed circuit board receiving the antenna 3 and the detection circuit 2. In addition or as a variant, such an adaptation circuit can comprise patterns printed on said printed circuit board and / or passive resistive, capacitive and / or inductive components.

[0055] The detection circuit 2 is configured to combine a pulse signal with a radiofrequency carrier, so as to obtain an electrical signal transmitted to the antenna 3, which transforms it into an electromagnetic signal to form the transmitted signal 101. The detection circuit 2 is further configured to carry out a frequency demodulation of an electrical signal supplied by the antenna and corresponding to the received signal 102, so as to discard the high-frequency information linked to the carrier only. In particular, the detection circuit 2 comprises, at least, a separator, a phase shift element, and two mixers, so as to cause the electrical signal supplied by the antenna and the carrier of the transmitted signal 101 to interfere with each other to provide signals I(t) and Q(t) corresponding respectively to the in-phase and quadrature-phase components of the frequency-demodulated received signal.

[0056] In use, the antenna 3 extends along an outer surface of the bodywork, on the inside of the vehicle, and so that a detection zone extends outside the vehicle. Preferably, a distance between the antenna 3 and said outer surface is less than 5 cm, preferably less than 2 cm.

[0057] The invention proposes to use the antenna 3 to detect a hand and / or a finger of a user, in the immediate vicinity of the antenna. When there is a presence in the immediate vicinity or in direct contact with the antenna 3, the impedance of the antenna 3 is disturbed, which impacts the impedance matching between the antenna 3 and the detection circuit 2, and varies the reflection losses at the level of the antenna 3.

[0058] These reflection losses correspond to a phenomenon called “spill over” in English, during which part of the emitted wave is directly returned to the antenna 3. More precisely, “spill over” is defined as the part of the electrical signal intended to be converted into an emitted electromagnetic signal, by the antenna 3, reflected in the antenna 3 and transformed into an electrical signal considered as coming from a received electromagnetic signal.

[0059] In a conventional design phase of a radiofrequency system, and more particularly an ultra-wideband system, the aim is to minimize the spillover by maximizing the adaptation of the antenna 3 relative to the detection circuit 2 and / or by minimizing the reflection losses in the antenna 3. The aim is to improve the power of the transmitted signal, and above all to avoid blinding the reception path with this spillover, the amplitude of which can be much higher than that corresponding, for example, to a useful signal originating from the reflection of a transmitted signal on a target. In other words, the spillover is considered as noise and removed or minimized by optimizing the antenna 3 or by digital processing.

[0060] In the invention, by contrast, the antenna 3 is advantageously configured to maximize an impedance variation when a finger approaches. This objective is unusual for an antenna design. Furthermore, and as detailed below, the portion of the signal corresponding to the spillover is not filtered, or suppressed in any way whatsoever on reception, but on the contrary used to perform presence detection.

[0061] A particularly advantageous implementation of the invention is described below.

[0062] The transmitted pulse signal 101 consists of a succession of pulses Tx(k), transmitted periodically. In reception, the received signal 102 is defined as consisting of a plurality of elementary signals received Rx(k) each relating to a respective one of the transmitted radiofrequency pulses Tx(k). The index k, here called the first index, or CIR index, reflects the place of a transmitted pulse, respectively received, in a train of transmitted pulses, respectively received.

[0063] The received signal 102 is frequency demodulated and time sampled, to obtain sampled data I(ti) and Q(ti). The signals I and Q result respectively from an in-phase mixing (I signal) and a phase quadrature mixing (Q signal) between the electrical signal corresponding to the received signal 102 and the carrier of the transmitted signal 101. The time sampling can be carried out on the received signal 102 or on the I and Q signals. In any case, the sampled data I(ti) and Q(ti) are finally obtained. The time sampling is carried out using an analog-digital converter, with a sampling period corresponding to the width At of the time windows.

[0064] The sampled data I(ti) and Q(ti) thus relate to a plurality of time windows which are distributed over different time ranges. Preferably, each time range is associated with a respective one of the received elementary signals Rx(k) and has as its origin the instant of emission of the corresponding emitted pulse Tx(k). For each time range associated with a emitted pulse of index k, the successive sampling windows are numbered using a second index i, the value of which reflects a difference relative to the instant of origin of the time range considered. Thus, the index i represents an increasing delay between the emission of the emitted pulse Tx(k) of index k and the reception of a portion of the corresponding received elementary signal Rx(k). The second index i is also called “Tap number”.It is linked to the time elapsed between the emission of a pulse Tx(k) of the transmitted signal, and the detection of a portion of the corresponding elementary signal received Rx(k).

[0065] Numbering the sampling window indices i from the instant of emission of a corresponding pulse of the emitted signal, achieves a folding of the time axis (a new origin of the times is defined at each new emission of a radiofrequency pulse Tx(k)).

[0066] An amplitude of the frequency-demodulated received signal is determined, which corresponds to the modulus of a complex number I+j*Q, and which is denoted ICIRI. For each time window ti, the amplitude of the frequency-demodulated received signal, denoted ICIRI, is determined using the data I(ti) and Q(ti). In other words, for each sampling window of each time range, CIR (Channel Impulse Response) signal amplitudes, denoted ICIRI, are determined, which are calculated using the received elementary signals Rx(k) and the transmitted pulses Tx(k).

[0067] The amplitude of the received signal demodulated in frequency is generally represented in the form of a graph as illustrated by figure [Fig.2], in which: - a first horizontal axis reflects the first index k, or CIR index, identifying a given pulse k of the emitted signal; - a second horizontal axis reflects the second time window index i sampling, and representing the time difference, or time t, between the emission of a pulse Tx(k) of the transmitted signal and the reception of a portion of the corresponding received elementary signal Rx(k); and - the vertical axis reflects the amplitude of the received signal demodulated in frequency, noted ICIRI.

[0068] In use, when a part of the hand comes into immediate proximity to the antenna 3 (in practice less than 5 cm between the antenna 3 and said part of the hand), there is a variation in adaptation of the antenna 3 which results in a variation in the amplitude of the “spill over”.

[0069] For each elementary signal received Rx(k), the “spill over”, or internal reflections in the antenna 3, affects the amplitude of the corresponding frequency-demodulated received signal, at the level of the first sampling window (of index i=i0) counted from the emission of the corresponding pulse Tx(k) of the emitted signal. This amplitude variation serves as a signature of the presence of the user, in particular the presence of a hand and / or a finger near the antenna 3.

[0070] Figure [Fig.2] illustrates the approach of a user's thumb to three successive occurrences, which results in three variations 21 of the amplitude of the frequency-demodulated received signal (ICIRI) at i=i0.

[0071] Figures 3 to 6 illustrate the different stages of processing the amplitude of the frequency-demodulated received signal (ICIRI), implemented to carry out presence detection.

[0072] Firstly, the ICIRI signal in figure [Fig.2] is processed so as to remove background noise, to keep only the dynamic part of the signal corresponding to the effect of the three thumb presses. The resulting signal is illustrated in figure [Fig.3],

[0073] In a second step, the signal associated with a second index of predetermined value SI is extracted from the signal in [Fig.3], with here SI=i0 the index of the first sampling windows as defined above.

[0074] In other words, a first contribution corresponding to the internal reflections of the transmitted signal (101) inside the antenna (3) is extracted from the frequency-demodulated received signal.

[0075] The resulting signal is illustrated in figure [Fig.4]. It corresponds to a sectional view of figure [Fig.3], along a plane located at i=i0.

[0076] The extracted signal, or first contribution, is then filtered using a low-pass filter, to achieve smoothing. The low-pass filter advantageously has a cut-off frequency fc=10Hz. An offset (constant) can also be removed, in order to remove any contribution linked to the environment. The resulting signal is illustrated in figure [Fig.5]. This is a signal relating to said first contribution, corresponding here to the first contribution filtered and shifted by a constant amplitude value.

[0077] The amplitude of this signal is then compared to a predetermined threshold value SE. If the amplitude is greater than the threshold SE, it is considered that the presence of a user is detected. Otherwise, it is considered that the presence of a user is not detected. This comparison step can correspond to the formation of a signal as illustrated in figure [Fig.6], taking a first value (here the high value) when the amplitude is greater than the threshold SE and a second value (here the low value) when the amplitude is less than or equal to the threshold SE. In other words, information relating to a user presence is determined using a comparison between an amplitude of said signal relating to the first contribution and the predetermined threshold SE.

[0078] In variants, the signal relating to the first contribution simply corresponds to the first filtered contribution but without shifting by a constant amplitude value. In still other variants, the signal relating to the first contribution corresponds directly to the first contribution (without filtering or shifting by a constant amplitude value).

[0079] In [Fig.6] we find the three thumb supports illustrated in [Fig.2].

[0080] We refer again to figure [Fig.l]. The radiofrequency module 1 intended to be embedded in a motor vehicle comprises the transmission and reception module 10 as described above, a signal extraction module 6 connected at the input to the transmission and reception module 10, and at the output to a first signal processing module 7. Here, but in a non-limiting manner, the signal extraction module 6 is connected at the output, in addition, to a second signal processing module 8.

[0081] The signal extraction module 6 is configured so as to extract, on a signal obtained using the received signal 102, said first contribution corresponding to the internal reflection of the transmitted signal 101 in the antenna 3.

[0082] Here, and advantageously, the signal extraction module 6 is further configured so as to extract, on said signal obtained using the received signal 102, a second contribution distinct from the first contribution, corresponding to the remainder of the received signal and able to correspond to the reflection of the signal emitted on a distant object or to a new signal emitted by a user terminal in response to the reception of the signal emitted.

[0083] The second signal processing module 8 is configured here so as to receive said second contribution as input, and to deduce therefrom information on terminal location, or terminal authentication, or user gesture recognition. An on-board access management system of the vehicle, not shown, can receive said information and control in response at least one access function to the vehicle, in particular locking or unlocking the opening, or opening or closing said opening.

[0084] The first signal processing module 7 is configured to determine a presence of a user in the immediate vicinity of the vehicle, using said first contribution extracted by the signal extraction module 6 as detailed above.

[0085] Advantageously, the first signal processing module 7 is connected to a management system which uses presence information provided by the first signal processing module 7 to control at least one function of the vehicle, in particular locking and / or unlocking of an opening, or opening and / or closing of said opening, or lowering and / or raising of an electric window.

[0086] The invention also covers a motor vehicle equipped with at least one opening such as a door, and a radiofrequency module 1 as described above.

[0087] The radiofrequency module 1 is configured to carry out a detection method as described below. The detection method is illustrated by the figure [Fig.7] and comprises the following steps:

[0088] Step El (implemented by the transmission and reception module 10): transmission of the transmitted signal (101), and reception of the corresponding received signal (102);

[0089] Step E2 (implemented by the detection circuit 2 of the transmission and reception module 10): frequency demodulation of the received signal, so as to provide the signals I(t) and Q(t) as described above, corresponding respectively to the in-phase and quadrature-phase components of a frequency-demodulated received signal;

[0090] Step E3 (implemented at least in part by the extraction module 6, and where appropriate also in part by the detection circuit 2): extraction of a first contribution from the frequency-demodulated received signal, said first contribution corresponding to internal reflections of the transmitted signal (101) inside the antenna (3),

[0091] Step E4 (implemented by the first signal processing module 7): comparison between the amplitude of a signal relating to said first contribution and the predetermined threshold SE. If the amplitude of said signal is greater than the predetermined threshold SE, it is considered that there is a detection of the presence of a user in the immediate vicinity of the vehicle. If this is not the case, it is considered that there is no user in the immediate vicinity of the vehicle.

[0092] Preferably, and as detailed above, the method comprises time sampling (implemented on the received signal or on the signals I and Q), so as to obtain sampled data I(ti) and Q(ti) as described above. The sampled data I(ti) and Q(ti) relate to a plurality of time windows. Said time windows are distributed over time ranges each associated with one of the received elementary signals Rx(k) forming the received signal. The time windows each have as their origin the instant of emission of the pulse corresponding Tx(k) of the transmitted signal 101. This sampling is advantageously implemented in step E2 of frequency demodulation of the received signal.

[0093] Preferably, and as detailed above, the method comprises a calculation of the amplitude of the demodulated received signal, using the sampled data I(ti) and Q(ti). Advantageously, this amplitude, denoted ICIRI, is equal to the modulus of a complex number I+j*Q. This amplitude calculation can be part of step E3 or E2.

[0094] Step E3 of extracting the first contribution is then formed by extracting the ICIRI amplitude values ​​relating, for each of said time ranges, to the first sampling window from the origin of said time range.

[0095] The method advantageously comprises steps of shaping the signal forming said first contribution, to obtain a smoothed and realigned signal whose amplitude is compared to the predetermined threshold SE during step 4. These shaping steps may comprise low-pass filtering and constant subtraction (offset) operations, as described with reference to FIGS. 2 to 5. When they exist, they are implemented by the signal extraction module 6 and / or by the first signal processing module 7.

[0096] These signal shaping steps may also comprise subtracting an offset value, determined as a function of the mean and standard deviation of the signal values ​​over the sampling window in question and for previous k pulses. When the standard deviation value becomes greater than a predetermined threshold value, the offset value is updated with the mean of the signal values ​​over the sampling window in question and for the previous k pulses. Alternatively, high-pass filtering is performed.

[0097] The method can be refined by imposing a minimum duration during which said amplitude obtained is greater than the threshold SE. In a particular embodiment, when it has been determined that the amplitude obtained is greater than the predetermined threshold SE, it is determined whether the amplitude obtained remains greater than said predetermined threshold for a duration at least equal to a predetermined threshold. If this is the case, there is presence detection. If this is not the case, there is no presence detection.

Claims

Claims

1. Radiofrequency module (1) intended to be embedded in a motor vehicle, and comprising: a transmission and reception module (10) comprising a detection circuit (2) and an antenna (3), the antenna (3) being configured to carry out the transmission of a pulse-modulated radiofrequency signal called transmitted signal (101) and the reception of a received signal (102) returning to the antenna (3), and the detection circuit (2) being configured to carry out at least one frequency demodulation of the received signal so as to provide signals I(t) and Q(t) corresponding respectively to the in-phase and quadrature-phase components of a frequency-demodulated received signal;a signal extraction module (6), configured to extract a first contribution from the frequency-demodulated received signal, said first contribution corresponding to internal reflections of the transmitted signal (101) inside the antenna (3), characterized in that it further comprises a first signal processing module (7), configured to receive said first contribution as input, and to deduce therefrom information relating to a user presence using a comparison between an amplitude of a signal relating to said first contribution and a predetermined threshold (SE).;

2. Radiofrequency module (1) according to claim 1, wherein: - the transmission and reception module (10) is configured to transmit a transmitted signal (101) consisting of periodic radiofrequency pulses, the received signal (102) being composed of elementary signals received each associated with a respective one of the transmitted radiofrequency pulses, - the transmission and reception module (10) is further configured to carry out a time sampling of the received signal (102) or of the signals I(t) and Q(t), so as to obtain sampled data I(ti) and Q(ti) relating to a plurality of time windows, the time windows being distributed over time ranges each associated with a respective one of the received elementary signals and each having as its origin an instant of emission of the corresponding transmitted radiofrequency pulse.

3. Radio frequency module (1) according to claim 2, wherein the signal extraction module (6) is configured to extract said first contribution using a selection of time windows of interest, based on a deviation at the origin between the time windows of interest and the origin of the corresponding time range.

4. Radio frequency module (1) according to claim 3, wherein the signal extraction module (6) is configured to calculate an amplitude of the frequency-demodulated received signal, using the sampled data I(ti) and Q(ti), and to extract the amplitude values ​​relating, for each of said time ranges, to the first sampling window from the origin of said time range.

5. Radiofrequency module (1) according to any one of claims 1 to 4, characterized in that the first signal processing module (7) is configured to determine the presence of a user when said amplitude of a signal relating to said first contribution is greater than the predetermined threshold (SE) for a duration greater than a predetermined duration threshold.

6. Radio frequency module (1) according to any one of claims 1 to 5, wherein the transmitted signal (101) is an ultra wideband radio frequency signal.

7. Radiofrequency module (1) according to any one of claims 1 to 6, characterized in that: - the signal extraction module (6) is further configured to extract a second contribution from the frequency-demodulated received signal, said second contribution corresponding to the reflection of the transmitted signal (101) on a target external to the radiofrequency module (1), or to a secondary signal radiated by a user terminal in response to the reception of the transmitted signal (101); and - the radiofrequency module (1) further comprises a second signal processing module (8), configured to receive as input said second contribution and to deduce therefrom at least one piece of information from among a target location, a gesture performed by a target, or a user terminal authentication code.

8. Motor vehicle comprising a radiofrequency module according to any one of the preceding claims, the antenna (3) of said module being located in a handle of an opening of the motor vehicle or in a structural lateral pillar of the motor vehicle, in particular a structural vertical pillar located between a front side door and a rear side door, or behind a decorative element located at the front or rear of the vehicle.

9. A motor vehicle according to claim 8, wherein the antenna (3) is arranged to extend along an exterior surface of the motor vehicle, the direction of emission of the antenna (3) being directed from the interior of the vehicle to the exterior of the vehicle.

10. Presence detection method implemented in a radiofrequency module (1) according to any one of claims 1 to 9, comprising the following steps: transmission of a pulse-modulated radiofrequency signal forming said transmitted signal (101), and reception of the received signal (102) consisting of received elementary signals each associated with a respective pulse of the transmitted signal (101), frequency demodulation of the received signal, so as to provide signals I(t) and Q(t) corresponding respectively to the in-phase and quadrature-phase components of a frequency-demodulated received signal;extraction of a first contribution from the received frequency-demodulated signal, said first contribution corresponding to internal reflections of the transmitted signal (101) inside the antenna (3), comparison between the amplitude of a signal relating to said first contribution and a predetermined threshold (SE), and detection of the presence of a user, if said amplitude is greater than the predetermined threshold (SE).;

11. Detection method according to claim 10, wherein the step of detecting the presence of a user is carried out when said amplitude is greater than the predetermined threshold (SE) for a duration greater than a predetermined duration threshold.

12. Detection method according to any one of claims 10 or 11, wherein: - the received signal (102) or said signals I(t) and Q(t) are sampled in time, so as to obtain the sampled data I(ti) and Q(ti) relating to a plurality of time windows, the time windows being distributed over time ranges each associated with a respective one of the elementary signals received and each having as its origin an instant of emission of the corresponding emitted radiofrequency pulse; - an amplitude of the frequency-demodulated received signal is calculated, at using the sampled data I(ti) and Q(ti); and - the amplitude values ​​relating, for each of said time ranges, to the first sampling window from the origin of said time range are extracted.

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