Presence detection method implemented in motor vehicle

Abstract

A presence detection method (100) implemented in a motor vehicle and using a return pulse signal originating from a reflection of an emitted pulse signal on a target, both the return pulse signal and the emitted pulse signal being composed of radio frequency pulses, the presence detection method (100) comprises the following steps: a / generating (101) sampled data (I, Q) relating to the return pulse signal; b / for each of a plurality of successive time intervals ([Delta] Tj), extracting (102) sample data located in said time interval ([Delta] Tj) and associated with a sample time for which a distance from the emission time of the respective pulse of the emitted pulse signal (SE) is less than a predetermined threshold; c / for each of the successive time intervals ([delta] Tj), and by means of the values extracted in step b / , calculating (103) a value of a phase shift ([phi] ([delta] Tj)) between the return pulse signal and the emitted pulse signal; and then d / using the value of the phase shift ([phi] ([delta] Tj)) to identify the presence or absence of the user.

Description

Technical Field

[0001] The present invention relates to the field of motor vehicles and, more particularly, to a presence detection method implemented within a motor vehicle to detect the presence of a user in close proximity to an element such as a door handle. Background Art

[0002] Presence detection devices implemented in motor vehicles are known from the prior art and are based on the use of electrodes coupled with capacitive measurements.

[0003] One drawback of solutions based on capacitive technology is that they can be susceptible to external environmental disturbances (such as raindrops).

[0004] One object of the present invention is to propose a solution that allows implementing presence detection in a motor vehicle that is robust to disturbances such as raindrops, while maintaining reduced bulk and complexity. Summary of the Invention

[0005] This object is achieved with a presence detection method implemented in a motor vehicle and using a return pulse signal resulting from reflection of a transmitted pulse signal on a target, both the return pulse signal and the transmitted pulse signal consisting of radio frequency pulses.

[0006] The presence detection method includes the following steps:

[0007] a / Generate sampling data of return pulse signal;

[0008] b / for each of a plurality of consecutive time intervals, extracting sampling data that is located in the time interval and is associated with a sampling instant for which the distance from the emission instant of the corresponding pulse of the emitted pulse signal is smaller than a predetermined threshold;

[0009] c / for each of the successive said time intervals and with the aid of the value extracted in step b / , calculate the value of the phase shift between the return pulse signal and the transmitted pulse signal; then d / use the value of the phase shift to identify the presence or absence of the user.

[0010] In this context, the term "radio frequency" is associated with a signal whose carrier frequency is between 3 kHz and 300 GHz. Preferably, the carrier frequency is in the present invention between 5 GHz and 20 GHz, more preferably between 5 GHz and 10 GHz.

[0011] In use, the target is, for example, a user's hand.

[0012] The sampling data of the return pulse signal corresponds to, for example, the sampling values of the in-phase component and the quadrature-phase component of the return pulse signal.

[0013] The method according to the present invention may include: a step of transmitting the transmitted pulse signal; and a step of receiving the return pulse signal.

[0014] One of the concepts underlying the present invention is to detect the presence or absence of a user via motion detection: Detection of a motion indicates the presence of a user, and vice versa.

[0015] The motion detection is based on radar technology, which makes it robust to disturbances such as raindrops while keeping the size and complexity reduced.

[0016] In a manner known per se, motion detection by radar technology is based on transmitting a radiofrequency signal in the direction of a reception area and receiving a return signal resulting from reflection of the transmitted radiofrequency signal on at least one target located in the reception area.

[0017] The most economical system is based on a simple time-of-flight calculation: for each of a number of sampling moments, the duration of time taken by the radio frequency signal to travel back and forth between the transceiver and the target is determined. This duration indicates the current distance to the target. However, one disadvantage is that the accuracy in determining the current distance to the target is limited by the sampling frequency. However, this sampling frequency cannot be increased indefinitely without incurring spectral folding boundary conditions (Shannon's criterion). Therefore, a typical sampling frequency value is 1 GHz, i.e. a period of one nanosecond. This corresponds to an accuracy of only 15 cm in determining the current distance to the target. This accuracy is insufficient in the case of presence detection based on whether an action in close proximity to the radar module (i.e. typically less than 10 cm from the radar module) is detected.

[0018] In order to overcome this limitation, the present invention therefore proposes to use instead the measurement of a phase shift, the variation of which indicates the presence or absence of motion.

[0019] Furthermore, to spatially scale presence detection, the present invention proposes using only data associated with sampling instants whose distance from the emission instant of the corresponding pulse of the transmitted pulse signal is less than a predetermined threshold. The predetermined threshold is a threshold in time units that can be easily converted into a threshold in distance units that defines the maximum range of presence detection. This ensures that presence detection accurately corresponds to the close proximity of the transceiver module that transmits the transmitted pulse signal and receives the return pulse signal.

[0020] Advantageously, step d / comprises the following sub-steps:

[0021] di / calculating, for each of said successive time intervals, the value of the derivative of the phase shift;

[0022] d-ii / performing a comparison between said value of the derivative of the phase shift and limits of at least one predetermined interval;

[0023] d-iii / calculating a final value of the counter for a time window of predetermined width framing a plurality of successive said time intervals, the value obtained by the counter being incremented by at least one unit each time the value of the derivative of the phase shift is within said at least one predetermined interval;

[0024] d-iv / comparing between the final value of the counter and a threshold value of the counter, and generating a high response value or a low response value depending on whether the final value of the counter is less than or greater than the threshold value of the counter;

[0025] dv / successively shifting the time window and re-iterating steps d-iii / and d-iv / so as to construct a response signal formed by a sequence of high response values or low response values; and

[0026] d-vi / Use response signals to identify the presence or absence of a user.

[0027] The value of the derivative of the phase shift characterizes the speed of the target. By comparing the value of the derivative of the phase shift with at least one predetermined interval limit, it is verified whether the movement of the target has the speed characteristic of the expected user action.

[0028] The presence detection based on the analysis of the target's velocity is stabilized by using a wide time window and a counter that increments its value each time the target's movement is considered to have the expected velocity characteristics. This stabilization of the presence detection ensures high robustness against noise and environmental disturbances.

[0029] By sliding the time window over time, a binary response signal is gradually constructed, which takes a high value or a low value depending on whether a stable target movement with a predetermined speed characteristic is detected.

[0030] This response signal is then used to identify the presence of a user. For example, if the response signal jumps from a low value to a high value, information related to presence detection can be generated. Alternatively, information related to presence detection can be generated only if the response signal remains at a high value for a duration greater than a predetermined threshold.

[0031] Preferably, in step di / , the value of the derivative of the phase shift is calculated by means of the difference between the value of the phase shift associated with the time interval considered and the value of the phase shift associated with the immediately preceding time interval.

[0032] Advantageously, the successive time intervals all have the same time width ΔT and follow one another in pairs.

[0033] Preferably, the successive shifts of the step dv / define a series of positions of the time window, said series of positions being distributed in time according to regularly distributed steps.

[0034] The distribution step size of the positions of the time windows is advantageously equal to N*ΔT, where N is an integer greater than or equal to unity.

[0035] Preferably, the width of the time window is between 50 and 200 times the step size of the distribution of the positions of said window.

[0036] The method may further comprise the step of using information about the presence or absence of the user to generate a command for locking or unlocking doors of the vehicle.

[0037] Preferably, the transmitted pulse signal is a UWB signal.

[0038] The present invention also encompasses a system comprising:

[0039] - a radar module comprising an electrical oscillator, at least one radio frequency antenna, at least one mixer, and at least one analog-to-digital converter, and configured to: transmit a transmitted pulse signal; receive a return pulse signal; and generate sampled data related to the return pulse signal; and

[0040] - a computing unit comprising at least one memory and at least one processor, said at least one memory comprising program code instructions which, when executed by said at least one processor, configure said processor to implement step b / and steps following step b / of the method according to the invention.

[0041] The system may further include a door handle having an integrated radar module.

[0042] The invention also relates to a computer program product comprising instructions for implementing step b / and steps following step b / of the method according to the invention when the program is executed by a processor. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] 31 Other features and advantages of the present invention will become more apparent on reading the following description. This description is purely illustrative and should be read with reference to the accompanying drawings, in which:

[0044] [ Figure 1 ] Figure 1 The steps of the method according to the invention are illustrated in a schematic manner;

[0045] [ Figure 2 ] Figure 2 A system according to the invention is illustrated in a schematic manner;

[0046] [ Figure 3 ] Figure 3 illustrates in a schematic manner sampled data associated with a return pulse signal;

[0047] [ Figure 4 ] Figure 4 illustrates an example of the evolution of the value of the phase shift between the return pulse signal and the transmitted pulse signal as a function of time;

[0048] [ Figure 5 ] Figure 5 illustrates an example of the evolution of the derivative of the phase shift between the return pulse signal and the transmitted pulse signal as a function of time;

[0049] [ Figure 6 ] Figure 6 illustrates in a schematic manner a time window of predetermined width used in the method according to the invention;

[0050] [ Figure 7 ] Figure 7 An example of the time evolution of a final value of a counter, as well as a threshold value of the counter and a response signal constructed with the aid of the final value of the counter is illustrated. DETAILED DESCRIPTION

[0051] Specific examples of the method 100 and system 200 according to the present invention are described below.

[0052] The method according to the invention is implemented in a motor vehicle and aims to detect the presence of a user in close proximity to an element such as a door handle or a vertical structural pillar (eg a B-pillar).

[0053] exist Figure 2 A system 200 according to the present invention is illustrated in a schematic manner in FIG.

[0054] System 200 includes:

[0055] - Radar module 210; and

[0056] - Calculation unit 220.

[0057] Radar module 210 comprises, in a manner known per se, at least one electrical oscillator, at least one radio frequency antenna, at least one mixer, and at least one analog-to-digital converter.

[0058] It is configured as:

[0059] - transmitting the transmitted pulse signal SE in the direction of a target 208 located outside the vehicle in use;

[0060] - receiving a return pulse signal SR, which corresponds to the reflection (or backscattering) of the transmitted pulse signal SE on the target 208;

[0061] - Implementing in-phase mixing and quadrature-phase mixing between the return pulse signal and the transmitted pulse signal or its carrier, so as to generate data I(t) related to the in-phase component of the return pulse signal SR and data Q(t) related to the quadrature-phase component of the return pulse signal SR; and - Implementing time sampling upstream or downstream of the mixing to provide sampled data related to the return pulse signal SR, here sampled data related to the in-phase component I(t) and the quadrature-phase component Q(t) of the return pulse signal SR.

[0062] In use, radar module 210 is placed, for example, inside a door handle or in a vertical structural pillar (such as a B-pillar).

[0063] The transmitted pulse signal SE is a radio frequency signal, and preferably a radio frequency signal of the UWB type.

[0064] Throughout this document, the term UWB (for "ultra-wide band" in English) or ultra-wideband is associated with radio frequency signals of low energy and large spectral width. In particular, a UWB radio frequency signal is defined by a ratio of bandwidth divided by center frequency being greater than or equal to 20%, or by a bandwidth of 250 MHz or greater.

[0065] The return pulse signal SR comes from the reflection of the transmitted pulse signal on the target. It is therefore also a radio frequency signal, for example of the UWB type, but its characteristics (such as phase, oscillation frequency and amplitude) have been modified due to the interaction with the target.

[0066] The computing unit 220 includes at least one memory and at least one processor, wherein the at least one memory includes program code instructions that, when executed by the at least one processor, configure the processor to implement the steps of the method as described below. The computing unit 220 may be remotely located relative to the radar module 210.

[0067] The computing unit 620 is configured to provide as output information regarding the presence or absence of a user.

[0068] exist Figure 1 A method 100 according to the present invention is illustrated in FIG. It comprises the steps detailed below.

[0069] Step 101:

[0070] The method according to the present invention first comprises step 101 : generating sampling data related to a return pulse signal SR.

[0071] The sampling preferably has a sampling step size between 0.8 ns and 2 ns (eg, 1 ns).

[0072] exist Figure 3 The sampled data associated with the returned pulse signal is schematically illustrated in FIG. They are in matrix form. One axis of the matrix corresponds to the pulse index k of the transmitted pulse signal. Another axis of the matrix corresponds to the index i of the sampling instant, with the value of the index reset to zero for each new pulse of the transmitted pulse signal. The last axis of the matrix corresponds to the values S(k,i) obtained from the sampled data, each value being associated with a pulse index k of the transmitted pulse signal and a sampling instant index i.

[0073] The value S(k,i) preferably corresponds to the value of the in-phase component I(t) of the return pulse signal SR and the value of the quadrature-phase component Q(t) of the return pulse signal SR.

[0074] The radar module 210 is configured to save the data S(k,i) and then send them in packets to the computing unit 620. At regular intervals ΔT j Send.

[0075] Time interval ΔT j They all have the same time width and follow one another directly. This time width is advantageously between 0.8 ms and 1.2 ms, for example equal to 1 ms.

[0076] Step 102:

[0077] The method then calculates the j The steps include: extracting the time interval ΔT j and are associated with sampling instants for which the distance from the emission instant of the corresponding pulse of the emitted pulse signal SE is smaller than a predetermined threshold value EC1.

[0078] The predetermined threshold value EC1 defines the maximum time interval from the emission instant of a corresponding pulse of the emitted pulse signal SE and thus corresponds to the maximum distance from the radar module 610 beyond which the return pulse signal SR is no longer used.

[0079] For example, the threshold is set to EC1 = 2 ns. This is due to considering only return pulse signals from targets located 30 cm or less from the radar module 610.

[0080] This therefore ensures that in the case of a close proximity presence detection of radar module 6100 only the most relevant data is selected.

[0081] Step 103:

[0082] The method then calculates the jThe steps include: calculating the phase shift φ (ΔT j ) value.

[0083] The phase shift φ(ΔT j ) is obtained with the aid of the value S(k,i) extracted in step 102, and wherein φ(t)=arctan(Q(t) / I(t)).

[0084] Preferably, the values S(k,i) associated with the individual pulses k and possibly the individual sampling instants i are combined in the form of an arithmetic mean for calculating φ(ΔT j ).

[0085] Figure 4 The phase shift φ (ΔT) between the return pulse signal and the transmitted pulse signal is shown as a function of time. j ). The abscissa is time, the ordinate is the angle which varies between -180° and +180°. Figure 4 , the time axis stretches over a duration of approximately 1 second.

[0086] exist Figure 4 Regions with rapid phase shift changes were observed in Figure 4 on the left and right sides in the figure) and a region Z1 with a slow phase shift change (in the middle of the figure).

[0087] Regions with rapid phase shift changes generally correspond to moments at which the detected displacements are relatively random, interfering movements.

[0088] In contrast, zone Z1 generally corresponds to moments at which the target performs relatively regular movements corresponding to approach actions performed by the user in a deliberate manner and indicating the user's presence.

[0089] However, at this stage it is difficult to distinguish the intended approach action from the interfering movements in an accurate manner.

[0090] Step 104:

[0091] The method then calculates the j The steps include: calculating the time derivative of the phase shift dφ(ΔT j ) / dt.

[0092] Preferably:

[0093] dφ(ΔT j ) / dt=(φ(ΔT j )-φ(ΔT j-1)) / ΔT, where ΔT is the time interval ΔT j time width.

[0094] The value ΔT is a constant, and in the method it can be considered that dφ(t) / dt=φ(ΔT k )-φ(ΔT k-1 ).

[0095] In other words, with the time interval ΔT j The value of the derivative of the associated phase shift is considered to be equal to the time interval ΔT considered j The value of the phase shift associated with the immediately preceding time interval ΔT j-1 The difference between the values of the associated phase shifts.

[0096] Figure 5 An example of the evolution of the derivative of the phase shift according to time is shown. The abscissa axis is time and the ordinate axis is the angle in degrees.

[0097] exist Figure 5 It identifies:

[0098] - a zone 51 in which the value of the derivative of the phase shift varies while remaining close to zero; and

[0099] Two regions 52 in which the value of the derivative of the phase shift assumes high values in absolute terms.

[0100] One of the considerations based on the present invention is that Figure 5 On this basis, it is not directly possible to make a reliable distinction between high phase shift values which are associated with irregular movements of the target and high phase shift values which can be obtained even in the presence of intentional actions performed by the target.

[0101] These high phase shift values obtained even in the presence of intentional motion can be compared to localized but sudden changes in phase ( Figure 4 The localized but sudden change in phase, corresponding to the region 44 in FIG. 4 , is simply related to the fact that the value of the phase shift is modulo 2*π (circular nature of the phase).

[0102] Step 105:

[0103] In the following steps, the derivative of the phase shift dφ(ΔT j The value of )) / dt is compared with limits of at least one predetermined interval.

[0104] Here, at least one predetermined interval includes a lower interval I b and upper interval I h , which together frame the zero value.

[0105] Preferably, the lower interval I band upper interval I h is symmetrical about the zero value of the derivative of the phase shift. This is due to comparing the absolute value of the derivative of the phase shift with at least one predetermined interval of limits.

[0106] The current value of the derivative of the phase shift is in the lower interval I b Middle or upper interval I h The fact that ∝ ∝ ∝ ∝ indicates that the phase shift has a characteristic variation of the intentional action. In other words, the speed of the target is regular and is calibrated between the maximum and minimum characteristic speeds of the intentional action.

[0107] For example, I h Between 0.1° and P, and I b Between -0.1° and -P, where P is between 5° and 30°, for example P=20°.

[0108] Step 106:

[0109] For framing a plurality of said consecutive time intervals ΔT j The final value Cf of the counter is calculated by using a time window 65 of a predetermined width. n , the derivative of each phase shift dφ(ΔT j The value of )) / dt is within at least one predetermined interval I b , I h The value obtained by the counter is incremented by at least one. For a time window of predetermined width, the final value Cf of the counter is calculated. i .

[0110] The calculation of step 106 therefore uses:

[0111] - a counter with a predetermined initial value, preferably a zero value; and

[0112] - a time interval ΔT in the time window 65 j The value of the derivative of each associated phase shift in .

[0113] Each time one of the values of the derivative of the phase shift is within at least a predetermined interval I b , I h In one of the cases, the counter is incremented by at least 1. In the other cases, the value of the counter is not modified.

[0114] Advantageously, the value of the derivative of each phase shift is at least within a predetermined interval I b , I h In one of these cases, the counter is incremented by exactly one.

[0115] In a variation, use:

[0116] - a plurality of intervals which are symmetrical pairwise and increasingly distant from the zero value of the derivative of the phase shift; and

[0117] - an incremental value that gradually increases as the zero value of the derivative of the phase shift is approached.

[0118] It is thus possible to make the value taken by the counter increase more quickly since the displacement of the target is regular.

[0119] As mentioned above, two intervals are used here to frame the zero value. The zero value is excluded in order to avoid incrementing the counter without a target displacement.

[0120] In a variant, a single interval incorporating a zero value is considered. It is then ensured by means of data relating to the amplitude of the return pulse signal that the counter is not incremented in the absence of a displacement of the target.

[0121] Step 107:

[0122] Then the final value of the counter Cf n With the threshold value S of the counter c Compare and calculate the final value of the counter Cf n Is it less than or greater than the counter threshold S C To generate high or low response values R n .

[0123] S C For example, between 10 and 15.

[0124] Step 108:

[0125] The position of the time window is then shifted in time by the value of the shift ΔF. The time window 65 thus forms a sliding window.

[0126] Steps 106 and 107 are then repeated for the new position of the time window.

[0127] The successive shifts of the time window 65 thus gradually build up the response value R n The response signal is formed by the sequence of n and Cf n ) are associated with successive positions of a time window.

[0128] Figure 6 The time window 65 is schematically illustrated for four consecutive positions of a time window of predetermined width. The consecutive positions of the time window are spaced two by two in a regular manner, wherein a time interval ΔF is provided between two consecutive positions of the time window.

[0129] The distribution step size ΔF of the position of the time window is equal to the time interval ΔT consideredj The distribution step length ΔT is equal to or an integer multiple of the distribution step length ΔT.

[0130] Advantageously, the sliding window has a time width Tw which is between 50 and 200 times the distribution step width ΔF of the positions of said window.

[0131] For example, Tw=100 ms, ΔT=ms, and ΔF=1 ms.

[0132] exist Figure 6 In the figure, the horizontal axis is time and the vertical axis is angle. Figure 6 Also shown is a curve 66 which represents in a schematic manner the evolution of the aforementioned phase shift φ(t) as a function of time.

[0133] Advantageously, the steps described above are repeated at least until a value greater than a threshold value S of the counter is obtained. C The final value of the counter Cf n .

[0134] exist Figure 7 It also stated:

[0135] a curve 71 representing the evolution of the final value of the counter as a function of the position taken by the time window and therefore as a function of time in the presence of an intentional approach action indicating the presence of a user;

[0136] - straight line 72, which represents the threshold value S of the counter C The value of

[0137] - curve 73 representing the evolution of the final value of the counter in the presence of interfering movements; and

[0138] - Template 74, which represents the response value R n The response signal is formed by the sequence.

[0139] The template 74 initially takes a low value, indicating that there is no intentional action. Once the curve 71 (the final value of the counter) exceeds the line 72 (the threshold value S of the counter), the C ), it switches to a high value. As soon as the curve 71 (the final value of the counter) returns to the straight line 72 (the threshold value S of the counter) C ) below, it then returns a low value.

[0140] The template 74 is constructed with successive shifts of the time windows.

[0141] Step 109:

[0142] Next, the response value R n The response signal formed by the sequence is used to identify the presence or absence of the user.

[0143] In particular, once the response signal changes from a low value to a high value, information related to the presence of the user may be generated.

[0144] As a variant, information relating to the presence of the user is generated as soon as the response signal changes from a low value to a high value and remains at a high value for a duration greater than or equal to a predetermined threshold.

[0145] In an optional subsequent step, not represented, the information about the user's presence is used to generate a command for locking or unlocking the door leaves of the vehicle (depending on the initial state of the door leaves).

[0146] The steps of the method according to the present invention are thus repeated until the response signal changes from a low value to a high value and then from a high value to a low value. This marks the start and end of a maneuver performed near radar module 210. By using a sliding window, the start and end times of a maneuver can be reliably determined. In particular, the erroneous detection of a series of short maneuvers instead of a single long maneuver is avoided.

[0147] exist Figure 1 , and to facilitate understanding of the invention, the step 108 of shifting the time window is shown after the step 107 of comparing the final value of the counter with the threshold value of the counter. However, in practice, step 108 can be implemented without waiting for the completion of steps 106 and 107 related to the previous position of the time window, i.e., starting the execution of steps 106 and 107 related to the subsequent position of the time window.

[0148] In a variant, the method according to the invention may comprise a preliminary detection step: detecting any movement, switching the drive system 200 from the standby state to the active state. Detection of any movement may be based on a comparison between the amplitude of the return pulse signal and a predetermined amplitude threshold.

[0149] In yet another variant, the sampled data generated in step 101 are corrected for an offset or bias. This offset is related in particular to the delay introduced by the radar module 210 and the ambient noise. This offset can be measured in a preliminary calibration step.

[0150] The above describes the use of phase shift φ(ΔT j ) to identify the presence or absence of a user. However, the present invention is not limited to this example and covers many other variations, such as not using a counter combined with a sliding window.

Claims

1. A presence detection method (100) implemented in a motor vehicle and using a return pulse signal (SR) resulting from the reflection of a transmitted pulse signal (SE) on a target (208), wherein both the return pulse signal and the transmitted pulse signal consist of radio frequency pulses, the presence detection method (100) comprising the following steps: a / generating (101) sampled data (I, Q) associated with the return pulse signal (SR); b / For multiple consecutive time intervals (ΔT j ), extract (102) the time interval (ΔT j ) and associated with a sampling instant for which the spacing from the emission instant of the corresponding pulse of the emitted pulse signal (SE) is smaller than a predetermined threshold; c / for the consecutive time intervals (ΔT j ) and, with the help of the values extracted in step b / , calculate (103) the phase shift (φ(ΔT) between the return pulse signal and the transmitted pulse signal j ))'s value; Then d / Use phase shift (φ(ΔT j )) value to identify whether the user exists, step d / includes the following sub-steps: di / for the consecutive time intervals (ΔT j ), calculate the derivative of the phase shift (dφ(ΔT j )) / dt) value; d-ii / derivative of phase shift (dφ(ΔT j )) / dt) and at least one predetermined interval (I b , I h ) boundaries (105); d-iii / For framing a plurality of successive said time intervals (ΔT j ) of a predetermined width, calculate (106) the final value of the counter (Cf n ), the derivative of each phase shift (dφ(ΔT j The value of )) / dt) is within the at least one predetermined interval (I b , I h ), the value obtained by the counter is incremented by at least one; d-iv / final value of the counter (Cf n ) is compared (107) with the threshold value (72) of the counter, and the final value (Cf n ) is less than or greater than the threshold of the counter to generate a high response value or a low response value (R n ); dv / successively shifts the time window (65) (108) and reiterates steps d-iii / and d-iv / so as to construct a window consisting of high or low response values (R n ) a response signal (74) formed by a sequence; as well as d-vi / uses (109) the response signal (74) to identify the presence or absence of the user.

2. The method (100) according to claim 1, characterized in that In step di / , with the aid of the time interval considered (ΔT j ) associated phase shift (φ(ΔT j )) and the value of the immediately preceding time interval (ΔT j-1 ) associated phase shift (φ(ΔT j-1 )) to calculate the derivative of the phase shift (dφ(ΔT j )) / dt) value.

3. The method (100) according to claim 1 or 2, characterized in that The time intervals between successive j ) all have the same time width ΔT and follow one after another.

4. The method (100) according to claim 3, characterized in that Successive shifts of the step dv / define a series of positions of the time window (65) distributed in time according to regularly distributed step sizes (ΔF).

5. The method (100) according to claim 4, characterized in that The distribution step size (ΔF) of the positions of the time window (65) is equal to N*ΔT, where N is an integer greater than or equal to unity.

6. The method (100) according to claim 4 or 5, characterized in that The width of the time window (Tw) is between 50 and 200 times the step size of the distribution of the positions of the window (ΔF).

7. The method according to any one of claims 1 to 6, characterized in that The method further comprises the step of using the information about the presence or absence of the user to generate a command for locking or unlocking the doors of the vehicle.

8. The method (100) according to any one of claims 1 to 7, characterized in that The transmitted impulse signal (SE) is a UWB signal.

9. A system (200), comprising: - a radar module (210) comprising an electrical oscillator, at least one radio frequency antenna, at least one mixer and at least one analog-to-digital converter, and configured to: transmit a transmitted pulse signal; Receive return pulse signal; and generating sampling data related to the return pulse signal (SR); and - a computing unit (220) comprising at least one memory and at least one processor, the at least one memory comprising program code instructions which, when executed by the at least one processor, configure the processor to implement step b / and steps following step b / of the method (100) according to any one of claims 1 to 8.

10. The system (200) of claim 9, further comprising a door handle, the door handle being integrated with the radar module (210).

11. A computer program product comprising instructions for implementing step b / and steps subsequent to step b / of the method (100) according to any one of claims 1 to 8 when the program is executed by a processor.

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