Radio frequency module for user detection, and corresponding detection method.

Abstract

Radio frequency module (1) intended to be carried in a motor vehicle, and comprising: a transmitting and receiving module (10), including an antenna (3) for transmitting a pulsed-modulated radio frequency signal called the transmitted signal (101) and receiving a received signal (102) returning to the antenna (3), and a detection circuit (2) for performing 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), to receive said first contribution, and to deduce information relating to a user's presence by means of a comparison to a predetermined threshold. Figure for the abstract: Fig 1;

Description

Title of the invention: Radio frequency module for user detection, and corresponding detection method. Technical field

[0001] The invention relates to the field of presence detection in the vicinity of a motor vehicle.

[0002] The presence detection information is intended to be used for controlling, from outside, a function such as locking and / or unlocking a vehicle opening, 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 in recent years to provide a hand presence sensor for a user, located in the handle of a motor vehicle opening, in particular in a side door handle, front trunk or rear trunk handle.

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

[0005] Furthermore, radio frequency type sensors for locating and / or authenticating a user by exchanging data with a user terminal, such as a key or access card on board or a smartphone equipped with a dedicated application, are also known in the field of vehicle access.

[0006] It should be noted that a radio frequency signal is an electromagnetic signal comprising a carrier with a frequency, 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 radio frequency signal can be pulse-modulated, that is, amplitude-modulated to form radio frequency pulses, meaning pulses whose carrier frequency belongs to the radio frequency spectrum. The use of this type of signal makes it possible, in particular, to determine the distance between a target and a signal transmission / reception device.

[0008] Preferably, the pulse-modulated radio frequency signal is a signal modulated using the "UWB" modulation technique, for "Ultra Wide Band". This modulation technique is based on the transmission of very short pulses, preferably less than one nanosecond, and over a wide frequency spectrum.

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

[0010] The invention relates to a radio frequency module intended to be installed in a motor vehicle, and comprising:

[0011] a transmit and receive module comprising a detection circuit and an antenna, the antenna being configured to perform the transmission of a pulse-modulated radio frequency signal called the transmitted signal and the reception of a received signal returning to the antenna, and the detection circuit being configured to perform 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 received signal demodulated in frequency;

[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 emitted inside the antenna.

[0013] The radio frequency module according to further includes a first signal processing module, configured to receive said first contribution as input, and to deduce information relating to a user presence by means of 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 information relating to a user presence when at least one predetermined condition is met, the at least one predetermined condition including the amplitude of a signal corresponding to said first contribution exceeding the predetermined threshold.

[0015] We speak of a signal corresponding to said first contribution, to designate said first contribution, or, where applicable, the signal resulting from filtering operations 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 specific vehicle function, for example, locking and / or unlocking a door, opening and / or closing a door, raising and / or lowering electric windows, etc.

[0018] A user wishing to activate such a function places at least part of their hand against an external surface of the vehicle, in the direction of the antenna. This hand contact with the antenna results in a change in the antenna's impedance, and therefore a change in the impedance matching between the antenna's impedance and the impedance of a detection circuit connected to the antenna.

[0019] The change in impedance matching results in a variation in the amplitude of a portion of the signal received by the detection circuit, corresponding to internal reflections within the antenna. By extracting this portion of the received signal, referred to here as the first contribution of the received signal, and comparing its amplitude to a predetermined threshold, it is thus possible to determine whether or not a hand is against the antenna.

[0020] The invention thus makes it possible to use a radio frequency module as a presence sensor in a very simple way.

[0021] The invention further enables the sharing of resources with a radio frequency module, in particular a UWB module, already present in the vehicle for other functions (for example, for the localization 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 from 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 localization, authentication, and / or gesture detection.

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

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

[0024] Advantageously, the invention thus proposes to replace 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 radio frequency module according to the invention.

[0025] Advantageously, the radio frequency module according to the invention is configured to operate in "radar" mode, the received signal then comprising the reflection of the emitted signal off a target. Alternatively, the radio frequency module according to the invention is configured to operate in "ranging" mode, the received signal including a signal emitted by a terminal in response to the reception of the emitted signal.

[0026] Advantageously: - The transmitting and receiving module is configured to emit a signal consisting of periodic radio frequency pulses, the received signal being composed of elementary received signals each associated with one of the respective emitted radio frequency pulses, - The transmit and receive module is further configured to perform 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 one of the respective elementary signals received and each originating from an instant of emission of the corresponding transmitted radio frequency pulse.

[0027] The signal extraction module can be configured to extract said first contribution using a selection of time windows of interest, based on an offset 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 received frequency-demodulated 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 the amplitude of a signal relating to the first contribution is greater than the predetermined threshold for a duration greater than a predetermined duration threshold.

[0030] The emitted 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 emitted signal on a target external to the radio frequency module, or to a secondary signal radiated by a user terminal in response to the reception of the emitted signal; and - the radio frequency module also includes a second signal processing module, configured to receive said second input and to deduce at least one piece of information from it, such as 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 radio frequency 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 can be arranged so as to extend along an external surface of the motor vehicle, the emission direction of the antenna being directed from the inside of the vehicle to the outside of the vehicle.

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

[0035] a / transmission of a pulse-modulated radio frequency signal forming said emitted signal, and reception of the received signal consisting of elementary received signals each associated with a respective pulse of the emitted 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 received signal demodulated in frequency; c / extraction of a first contribution from the frequency-demodulated received signal, 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 process comprises the following steps: - the received signal or said signals I(t) and Q(t) are time-sampled, 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 one of the respective elementary signals received and each having as its origin an instant of emission of the corresponding emitted radio frequency pulse; - we calculate the amplitude of the received frequency-demodulated signal, using the sampled data I(ti) and Q(ti); and - we extract the amplitude values ​​relating, for each of the said time ranges, to the first sampling window from the origin of said time range. Brief description of the drawings

[0037] Other objects, features and advantages of the invention will become apparent from the following description, given solely by way of non-limiting example and made with reference to the accompanying drawings in which:

[0038] - Figure [Fig. 1] illustrates the main elements of a radio frequency module according to the invention,

[0039] - Figure [Fig.2] is a graph illustrating the signal received by the module radio frequency, when a user's thumb is pressed against and then moved away from a contact area three times with respect to the radio frequency module's antenna,

[0040] - Figure [Fig.3] is a graph illustrating the signal of [Fig.2], after suppression 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 from [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. 1 illustrates a radio frequency module 1 according to the invention.

[0046] In use, the radio frequency module 1 is integrated on 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 radio frequency module 1 is configured to perform presence detection. When it detects the presence of a user, the radio frequency module 1 generates a presence detection signal, which it sends to an auxiliary device configured to activate a given function of the vehicle, in particular a locking and / or unlocking function of a vehicle opening or an opening and / or closing function of the opening and / or a raising and / or lowering function of an electric window of the vehicle.

[0048] Advantageously, in addition to a presence detection function, the radio frequency module 1 also serves to implement communication Bidirectional communication with a user terminal is used for authentication or locating that user terminal. Such a user terminal can be a key, an onboard access card, or a smartphone. Additionally, or alternatively, the radio frequency module 1 can also be used to implement gesture detection for controlling a second function, such as one related to vehicle access.

[0049] The radio frequency module 1 includes a transmitting and receiving module 10, also called a transmitter (“transceiver” in English).

[0050] The transmit and receive module 10 is configured for the transmitting and receiving of UWB signals (English acronym for "Ultra Wide Band", or in French "ultra large bande").

[0051] The transmitting and receiving module 10 includes a detection circuit 2 and an antenna 3.

[0052] Antenna 3 is configured to perform: - the emission of a radio frequency signal 101, from an electrical signal 4 generated at 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 the sake of clarity, the received signal 102 is shown to originate from the environment external to the transmitting and receiving module. However, as detailed below, the received signal 102 also includes a component corresponding to internal reflections on the antenna 3.

[0054] Advantageously, the transmit and receive module 10 also includes an adaptation circuit, not shown, disposed between the antenna 3 and the detection circuit 2. Such an adaptation circuit can be formed by a progressive variation in the thickness of the conductive tracks on a printed circuit board receiving the antenna 3 and the detection circuit 2. In addition or alternatively, such an adaptation circuit can include 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 pulsed signal with a radio frequency 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 perform 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 associated solely with the carrier. In particular, the detection circuit 2 comprises, at least, a separator, a phase-shifting 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 received frequency-demodulated signal.

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

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

[0058] These losses by reflection 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 electromagnetic signal emitted by the antenna 3, reflected in the antenna 3 and transformed into an electrical signal considered to come from a received electromagnetic signal.

[0059] In a typical design phase of a radio frequency system, and more specifically an ultra-wideband system, the aim is to minimize spillover by maximizing the matching of antenna 3 relative to the detection circuit 2 and / or by minimizing reflection losses in antenna 3. The goal is to improve the power of the transmitted signal, and above all to avoid blinding the receiving channel with this spillover, the amplitude of which can be much higher than that corresponding, for example, to a useful signal resulting from the reflection of a transmitted signal off a target. In other words, spillover is considered noise and is removed or minimized by optimizing antenna 3 or by digital processing.

[0060] In contrast, in the invention, the antenna 3 is advantageously configured to maximize the impedance change 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 during reception, but rather 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), emitted periodically. In reception, the received signal 102 is defined as consisting of a plurality of elementary received signals Rx(k), each relating to one of the respective transmitted radio-frequency pulses Tx(k). The index k, named Here, the first index, or CIR index, accounts for the position of an emitted, or received, pulse in a train of emitted, or received, pulses.

[0063] The received signal 102 is frequency demodulated and time-sampled to obtain sampled data I(ti) and Q(ti). Signals I and Q result respectively from in-phase (signal I) and quadrature-phase (signal Q) mixing of the electrical signal corresponding to the received signal 102 and the carrier of the transmitted signal 101. Time sampling can be performed on the received signal 102 or on signals I and Q. In any case, the sampled data I(ti) and Q(ti) are ultimately obtained. Time sampling is performed using an analog-to-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 distributed over different time ranges. Preferably, each time range is associated with one of the respective elementary received signals Rx(k) and originates at the time of emission of the corresponding emitted pulse Tx(k). For each time range associated with an emitted pulse of index k, successive sampling windows are numbered using a second index i, the value of which reflects a deviation from the origin of the time range under consideration. 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 elementary received signal Rx(k). The second index i is also called the "Tap number".It is related to the time elapsed between the emission of a pulse Tx(k) of the emitted signal, and the detection of a portion of the corresponding received elementary signal Rx(k).

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

[0066] An amplitude of the received frequency-demodulated signal is determined, corresponding to the magnitude of a complex number I+j*Q, and denoted ICIRI. For each time window ti, the amplitude of the received frequency-demodulated 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 and calculated using the elementary received signals Rx(k) and the emitted pulses Tx(k).

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

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

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

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

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

[0072] Initially, the ICIRI signal in Figure [Fig.2] is processed to remove background noise, retaining 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, we extract from the signal of [Fig.3], the signal associated with a second index of predetermined value SI, 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 signal emitted (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 cross-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 offers a The cutoff frequency fc = 10 Hz. An offset (constant) can also be removed to eliminate any environmental influence. The resulting signal is shown in Figure [Fig. 5]. This signal relates to the first contribution, corresponding here to the first filtered contribution offset 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, the presence of a user is considered to have been detected. Otherwise, the presence of a user is considered not to have been 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's presence is determined by comparing the amplitude of said signal relating to the first input with the predetermined threshold SE.

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

[0079] Figure 6 shows the three thumb supports illustrated in Figure 2.

[0080] Reference is again made to Figure [Fig. 1]. The radio frequency module 1 intended to be embedded in a motor vehicle includes the transmission and reception module 10 as described above, a signal extraction module 6 connected at input to the transmission and reception module 10, and at output to a first signal processing module 7. Here, but not limitingly, the signal extraction module 6 is connected at 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 signal emitted 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 which may correspond to the reflection of the signal emitted on a remote object or to a new signal emitted by a user terminal in response to the reception of the emitted signal.

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

[0084] The first signal processing module 7 is configured to determine the 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, including locking and / or unlocking of an opening, or opening and / or closing of said opening, or raising and lowering of an electric window.

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

[0087] The radio frequency module 1 is configured to perform a detection method as described below. The detection method is illustrated in 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 transmit and receive 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 received signal demodulated in frequency;

[0090] Step E3 (implemented at least in part by the extraction module 6, and where applicable 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 emitted 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 assumed that there is detection of a user's presence in the immediate vicinity of the vehicle. If this is not the case, it is assumed that there is no user in the immediate vicinity of the vehicle.

[0092] Preferably, and as detailed above, the method includes time sampling (implemented on the received signal or on the I and Q signals), in such a way 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. These time windows are distributed over time ranges, each associated with one of the elementary received signals Rx(k) that make up the received signal. Each time window originates at the emission time of the corresponding pulse Tx(k) of the transmitted signal 101. This sampling is advantageously implemented in the frequency demodulation step E2 of the received signal.

[0093] Preferably, and as detailed above, the method includes calculating the amplitude of the received demodulated 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 extraction of the first contribution is then formed by the extraction of 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 includes signal shaping steps for the first contribution, to obtain a smoothed and recalibrated signal whose amplitude is compared to the predetermined threshold SE in step 4. These shaping steps may include low-pass filtering and constant (offset) subtraction operations, as described with reference to Figures 2 to 5. Where 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 include subtracting an offset value, determined based on the mean and standard deviation of the signal values ​​over the considered sampling window and for previous pulses k. 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 considered sampling window and for the previous pulses k. Alternatively, high-pass filtering is performed.

[0097] The method can be refined by imposing a minimum duration during which the obtained amplitude exceeds the threshold SE. In a particular embodiment, once it has been determined that the obtained amplitude exceeds the predetermined threshold SE, it is determined whether the obtained amplitude remains above said predetermined threshold for a period at least equal to a predetermined duration threshold. If so, presence is detected. If not, presence is not detected.

Claims

1. Demands Radio frequency module (1) intended for installation in a motor vehicle, and comprising: a transmitting and receiving module (10) comprising a detection circuit (2) and an antenna (3), the antenna (3) being configured to transmit a pulsed-modulated radio frequency signal called the transmitted signal (101) consisting of periodic radio frequency pulses and to receive a received signal (102) returning to the antenna (3) consisting of elementary received signals each associated with one of the respective transmitted radio frequency pulses, the detection circuit (2) being configured to perform 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 received signal demodulated in frequency; - the transmit and receive module (10) is further configured to perform 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 one of the respective elementary signals received and each originating from an instant of emission of the corresponding emitted radio frequency pulse and -a signal extraction module (6), configured to extract a first contribution from the received frequency-demodulated signal using a selection of time windows of interest, based on an initial deviation between the time windows of interest and the origin of the corresponding time range, said first contribution corresponding to internal reflections of the transmitted signal (101) within the antenna (3), further comprising a first signal processing module (7), configured to receive said first contribution as input, and to deduce therefrom information relating to a user presence by means of a comparison between an amplitude of a signal relating to said first contribution and a predetermined threshold (SE), the radio frequency module being characterized in that the signal extraction module (6) is configured to calculate an amplitude of the received frequency demodulated 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.

2. Radio frequency module (1) according to the preceding claim, 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.

3. Radio frequency module (1) according to any one of claims 1 to 2, wherein the emitted signal (101) is an ultra-wideband radio frequency signal.

4. Radio frequency module (1) according to any one of claims 1 to 3, 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 emitted signal (101) on a target external to the radio frequency module (1), or to a secondary signal radiated by a user terminal in response to the reception of the emitted signal (101); and - the radio frequency module (1) further comprises a second signal processing module (8), 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.

5. Motor vehicle comprising a radio frequency 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 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.

6. A motor vehicle according to claim 5, wherein the antenna (3) is arranged to extend along an external surface of the motor vehicle, the emission direction of the antenna (3) being directed from inside the vehicle to outside the vehicle.

7. A presence detection method implemented in a radio frequency module (1) according to any one of claims 1 to 4, comprising the following steps: transmission of a pulse-modulated radio frequency signal forming said transmitted signal (101), and reception of the received signal (102) consisting of elementary received 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, the received signal (102) or said signals I(t) and Q(t) are time-sampled 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 one of the respective elementary signals received and each originating from an instant of emission of the corresponding emitted radio frequency pulse; - calculation of an amplitude of the received frequency-demodulated signal, using the sampled data I(ti) and Q(ti); and - extraction of the amplitude values ​​relating, for each of said time ranges, to the first sampling window from the origin of said time range. extraction of a first contribution of the received frequency-demodulated signal, said first contribution corresponding to internal reflections of the emitted 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),

8. A detection method according to claim 7, 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.

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