Device for detecting the movement of a person using microwave waves for a motor vehicle

Abstract

The invention relates to a device (10) for detecting the movement of a person (2) by microwave waves for a motor vehicle (1), said device (10) comprising a radiating impedance module (110) configured to be powered by a DC voltage supply (30) and comprising a detection antenna (112), a MOSFET type transistor (114) and an impedance adapter (116) forming a closed-loop electrical circuit oscillating at the predetermined fixed frequency when said circuit is powered by the voltage supplied by said DC voltage supply (30). Figure for abstract: Figure 2

Description

Title of the invention: Device for detecting the movement of a person using microwave waves for a motor vehicle Technical field

[0001] The present invention relates to the field of automobiles and more particularly concerns a device and a method for detecting the movement of a person by microwave waves for a motor vehicle. Prior art

[0002] In a motor vehicle, it is known to detect the presence of a hand on a handle or a foot near the trunk of the vehicle in order to unlock one or more openings of the vehicle.

[0003] In a first type of known solutions, this presence detection, called "near field", is carried out using a detector generally mounted in the handle or under the trunk. This detector comprises a radar type antenna or a capacitive sensor.

[0004] When a part of the human body, such as a hand or a foot, approaches within a few centimeters of the antenna, for example less than 5 cm, it modifies the impedance of the antenna in the near field and an analog or digital circuit of the detector allows the detection of this modification, synonymous with human presence.

[0005] The range of this detection is however limited to a few centimeters for radiofrequency antennas, in particular to less than 5 centimeters for most radiofrequency antennas. The main disadvantage of this technique is the very limited range for carrying out detection functions such as the intrusion of a person into a vehicle.

[0006] In a second type of known solutions, the presence detection is carried out using a detector implemented by a communication module mounted in the vehicle and using microwave waves, in particular based on a BLE (Bluetooth® Low Energy) or UWB (Ultra Wide Band) type technology.

[0007] In these solutions, presence detection can be carried out in the far field, for example up to 30 meters, but require the use of at least two antennas: a transmitting antenna, which sends waves in the form of pulses, and a receiving antenna, which receives the waves reflected on one or more moving targets in the coverage area.

[0008] The detector determines that the targets are moving by using the time of flight of the signals, which requires complex digital processing and therefore significant processing capacities and high consumption. In addition, the need of multiple antennas makes the solution complex and expensive and increases the risk of radio interference with the near-field hands-free access system because the number of spaces available between each pulse to receive access frames is low. Finally, the standards in force impose limitations in terms of power, which can significantly limit the use of multiple antennas emitting microwave waves or lead to exceeding the radio approval threshold in the communication band, particularly in UWB.

[0009] A simple, reliable and effective solution to at least partially remedy these drawbacks would therefore be advantageous. Statement of the invention

[0010] To this end, the invention firstly relates to a device for detecting the movement of a person by microwave waves for a motor vehicle, said device comprising a radiating impedance module configured to be powered by a DC voltage supply via a switch, said radiating impedance module comprising a detection antenna configured to resonate at a predetermined fixed frequency when said detection antenna is coupled to a resonant module, to emit microwave waves and to receive microwave waves reflected on said person, a MOSFET type transistor and an impedance adapter forming a closed-loop electrical circuit oscillating at the predetermined fixed frequency when said circuit is powered by the voltage supplied by said DC voltage supply, the detection antenna being connected to the gate of the transistor,the impedance adapter being mounted between the gate and the drain of the transistor and being configured to adapt the impedance of the detection antenna to the impedance of the transistor by being powered by the voltage supplied by said DC voltage supply, the source of the transistor being configured to be connected on the one hand to a ground and on the other hand to an electronic control unit, the voltage signal delivered by the source of the transistor being representative of the impedance variations of the radiating impedance module, the impedance being stabilized when the frequency of the waves reflected on the person is equal to the frequency of the waves emitted at the predetermined fixed frequency, reflecting an absence of movement of the person, and variable when the frequency of the waves reflected on the person varies by a frequency difference greater than a threshold relative to the predetermined fixed frequency, reflecting the detection of a movement of the person.

[0011] The invention proposes a detection technique based on a radiating impedance. The stability of this impedance is maintained by the impedance adapter and the MOSFET transistor. The oscillating module plays the role of a stable transmitter / receiver / detector at a given frequency in the absence of movement. The reception of a frequency shifted by a few Hertz by movement in the radiation zone, in the same frequency band, destabilizes its impedance. The destabilization of the impedance generates a variable leakage voltage easily detectable at the output. The invention thus proposes a simple detection strategy not requiring a complex detection algorithm. The single-antenna oscillating loop only comprises analog components, which makes the device simple and inexpensive and limits excessive power consumption compared to other far-field detection solutions. Detection with a single antenna is simple and therefore inexpensive. The detection device according to the invention makes it possible to reduce the intense emission of microwave waves and to comply with the radio approval threshold in the communication band.The use of analog components also makes it possible to limit the processing to the evaluation of a voltage signal, which makes it simple, efficient, reliable and fast, particularly compared to solutions using digital processing circuits. The simple oscillating loop arrangement makes it possible to limit the size of the device to the size of a tag detector for Near Field Communication (NFC). The device according to the invention can operate alone by being coupled to an electronic control unit, but the reduced size of the oscillating loop arrangement also makes it possible to integrate the device into an existing BLE or UWB module, particularly to couple the detection antenna with the communication antenna of such a module.The device according to the invention also makes it possible to define a pre-detection strategy in order to activate other functions such as, for example, the triggering, preferably automatic, of a communication via a communication module, in particular BLE or UWB, or to activate a camera such as, for example, an on-board camera (dash-cam) or for access by facial authentication. The device according to the invention is simple, inexpensive and consumes little energy, which makes it possible to optimize consumption, in particular when the internal management system of the vehicle is in standby mode, for example when the vehicle is parked and locked. Since the variations in impedance are proportional to the movement of the person, the invention also makes it possible to detect the type of movement made by the person, in particular in order to trigger different functions of the vehicle.

[0012] Advantageously, the device is configured to attenuate the power of the detection antenna and / or the voltage signal of the transistor source to predetermined values ​​in order to adjust the detection distance determined by the electronic control unit. It is thus possible to generate a detection bubble inside and / or outside the vehicle. Such a bubble can provide several functions. For example, the bubble can be placed in the center of the vehicle and sized (for example, one meter in diameter) to detect an intrusion into the passenger compartment and trigger an intrusion alarm. For example, the bubble can be sized (e.g., ten meters in diameter) to detect suspicious movement outside the vehicle in parking mode and activate a camera, such as a vehicle dash cam, to film the vehicle's surroundings.

[0013] Preferably, the predetermined fixed frequency is greater than or equal to 2 GHz, preferably 2.45 GHz, for example between 2.45 GHz and 10.6 GHz, in order to use an approved frequency already used on existing smartphone-type equipment operating for example in 4G or 5G or in Ultra Wide Band (UWB).

[0014] In one embodiment, the radiating impedance module comprises an attenuator mounted between the detection antenna and the gate of the transistor, said attenuator being configured to attenuate the power of the detection antenna and / or the voltage signal of the source of the transistor.

[0015] In one embodiment, the radiant impedance module comprises a comparator configured to compare the output voltage of the source of the transistor to a predetermined voltage threshold corresponding to a detection distance. For example, a threshold of 10 mV may correspond to a 1 m area, a threshold of 100 mV may correspond to a 5 m area.

[0016] The resonant module can be integrated into the device or external to the device.

[0017] In one embodiment, the resonant module is a resonant antenna pattern and the coupling between the detection antenna and said resonant antenna pattern is electrical. For example, a resonant circuit placed in front of or next to the detection antenna makes it possible to adjust and optimize the operating frequency.

[0018] In another embodiment, the resonant module is a resonator and the coupling between the detection antenna and said resonant antenna pattern is magnetic. A resonator allows the size of the antenna (radiating impedance) to be reduced while maintaining the detection performance. The resonator improves the detection sensitivity.

[0019] In another embodiment, the resonant module is a vehicle communication antenna, external to the device, for example of the Bluetooth® Low Energy (BLE) or Ultra Wide Band (UWB) type.

[0020] The invention also relates to a motor vehicle comprising a detection device as presented previously and an electronic control unit connected to the source of the transistor and configured to receive the voltage signal delivered by the source of the transistor and to detect movement around the detection device when the value of the voltage of the source of the transistor is greater than a predetermined threshold.

[0021] Preferably, the electronic control unit is configured to detect a gesture from variations in the voltage value of the source of the transistor over a predetermined time interval.

[0022] In one embodiment, the vehicle includes a communication antenna configured to be electromagnetically coupled with the sensing antenna to form a resonator.

[0023] The invention also relates to a method for detecting the movement of a person by microwave waves for a motor vehicle using the detection device as presented above, said method comprising the steps of:

[0024] - emission, by the detection antenna, of hyperfrequency waves resonating at a predetermined fixed frequency,

[0025] - reception of microwave waves reflected on said person,

[0026] - detection, by the electronic control unit, of a movement of said person when the absolute value of the amplitude of the voltage signal measured at the transistor source varies beyond a predetermined amplitude threshold.

[0027] The invention also relates to a computer program product characterized in that it comprises a set of program code instructions which, when executed by one or more processors, configure the processor(s) to implement a method as presented above. Brief description of the drawings

[0028] Other characteristics and advantages of the invention will become apparent from reading the description which follows. This is purely illustrative and must be read in conjunction with the appended drawings in which:

[0029] [Fig-1] [Fig.l] schematically illustrates one embodiment of the vehicle according to the invention.

[0030] [Fig.2] [Fig.2] schematically illustrates an assembly comprising a device according to the invention powered by a voltage supply source and delivering a signal for detecting the movements of a person.

[0031] [Fig.3] [Fig.3] schematically illustrates a first embodiment of the device according to the invention.

[0032] [Fig.4] [Fig.4] schematically illustrates a second embodiment of the device according to the invention.

[0033] [Fig.5] [Fig.5] schematically illustrates a third embodiment of the device according to the invention.

[0034] [Fig.6] [Fig.6] schematically illustrates a fourth embodiment of the device according to the invention.

[0035] [Fig.7] [Fig.7] schematically illustrates a fifth embodiment of the device according to the invention.

[0036] [Fig.8] [Fig.8] schematically illustrates an embodiment of the method according to the invention.

[0037] [Fig.9] [Fig.9] schematically illustrates an example of a voltage signal delivered at the output of the source as a function of time for a given movement. Description of the embodiments

[0038] [Fig.l] schematically illustrates an example of a motor vehicle according to the invention.

[0039] The vehicle 1 comprises a motion detection device 10 according to the invention, an electronic control unit 20 and a direct voltage supply 30.

[0040] Detection device 10

[0041] With reference to [Fig. 2], the device 10 allows the detection of a movement of a person 2 by microwave waves in order, for example, to unlock the openings of the vehicle 1 or trigger a communication, for example with the smartphone of the user of the vehicle 1. The device 10 can be mounted at any location of the vehicle 1 but preferably at the level of a communication module of the vehicle 1 or in the passenger compartment of the vehicle 1.

[0042] The device 10 comprises a radiating impedance module 110 configured to be powered by the direct voltage supply 30, for example 5 V.

[0043] The radiating impedance module 110 comprises a detection antenna 112, a MOSFET type transistor 114 and an impedance adapter 116 forming an electrical loop.

[0044] The detection antenna 112 is configured to emit microwave waves ft by resonating at a predetermined fixed frequency and to receive reflected microwave waves fr on a person 2 located in the coverage of the emitted microwave waves ft, for example between 50 cm and 10 m from the detection antenna 112.

[0045] Transistor 114 is of the MOSFET type and comprises a gate G, a drain D and a source S.

[0046] The detection antenna 112 is connected to the gate G of the transistor 114.

[0047] The impedance adapter 116 is mounted between the gate G and the drain D of the transistor 114 and is configured to match the impedance of the detection antenna 112 to the impedance of the transistor 114 by being powered by the voltage supplied by the DC voltage supply 30.

[0048] The detection antenna 112, the transistor 114 and the impedance adapter 116 form a closed-loop electrical circuit oscillating at the predetermined fixed frequency when said circuit is powered by the voltage supplied by the DC voltage supply 30.

[0049] The device 10 comprises a switch 120 connected between the radiant impedance module 110 and the DC voltage supply 30. This switch 120 is periodically controlled in opening and closing, for example at a refresh rate of 10 Hz (every 100 ms), in order to only power the radiant impedance module 110 intermittently and thus limit the energy consumption of the device 10. The control of the switch 120 is carried out by the electronic control unit 20. The electronic control unit 20 sends a voltage to control the switch 120. For example, if the voltage is 5 volts, the circuit is closed and if it is 0 volts, the circuit is open.

[0050] The source S of the transistor 114 is connected on the one hand to a ground and on the other hand to the electronic control unit 20. The voltage signal S(V) delivered by the source S of the transistor 114 is received by the electronic control unit 20.

[0051] The electronic control unit 20 is configured to determine the variations in the amplitude of the signal S(V) delivered by the source S of the transistor 114.

[0052] The signal S(V) delivered by the source S of the transistor 114 is a voltage signal representative of the impedance variations of the radiating impedance module 110.

[0053] The electronic control unit 20 is configured to determine that the impedance of the radiating impedance module 110 is stabilized or variable from the voltage measured at the source S of the transistor 114. More precisely, the electronic control unit 20 is configured to determine whether the voltage of the source S of the transistor 114 is stable (i.e. substantially constant) or variable (i.e. varies beyond a threshold, in absolute value).

[0054] When the frequency of the reflected microwave waves fr on the person 2 is equal to the frequency of the microwave waves ftémitted at the predetermined fixed frequency, reflecting an absence of movement of the person 2, the voltage of the source S of the transistor 114 is substantially constant, that is to say that the impedance of the radiating impedance module 110 is stabilized.

[0055] On the other hand, when the frequency of the reflected microwave waves fr on the person 2 varies by a frequency difference (in absolute value) greater than a threshold, for example between 5 and 20 Hz, relative to the predetermined fixed frequency, reflecting the movement of a person 2 in the coverage of the detection antenna 110, the voltage of the source S of the transistor 114 varies beyond a threshold and the impedance of the radiating impedance module 110 is variable.

[0056] The electronic control unit 20 comprises a processor capable of implementing a set of instructions making it possible to carry out these functions.

[0057] First embodiment

[0058] In a first embodiment, illustrated in [Fig.3], the vehicle 1 or the device 10 comprises a resonant antenna pattern 40 and the detection antenna 112 is electrically coupled to said resonant antenna pattern 40 to resonate.

[0059] Second embodiment

[0060] In a second embodiment, illustrated in [Fig.4], the vehicle 1 or the device 10 comprises a resonator 45 and the detection antenna 112 is magnetically coupled to said resonator 45 to resonate.

[0061] Third embodiment

[0062] In a third embodiment, illustrated in [Fig. 5], the vehicle 1 comprises a communication antenna 50, for example of the Bluetooth® Low Energy (BLE) or Ultra Wide Band (UWB) type, and the detection antenna 112 is electromagnetically coupled to said communication antenna 50 to resonate. The communication antenna 50 is connected to a communication module 60 to perform functions of the vehicle 1, in particular the detection of the approach of a person 2 and communication with the smartphone, a badge or an unlocking key of the vehicle 1 carried by the person 2, in a manner known per se.

[0063] Fourth embodiment

[0064] In a fourth embodiment, illustrated in [Fig.6], the radiating impedance module 110 comprises a radiofrequency attenuator 118, connected between the detection antenna 112 and the gate G of the transistor 114.

[0065] The radiofrequency attenuator 118 makes it possible to attenuate the signal received from the detection antenna 112, according to a predefined attenuation level which makes it possible to size the detection zone.

[0066] Fifth embodiment

[0067] In a fifth embodiment, illustrated in [Fig.7], the vehicle 1 comprises a comparator 70, connected between the source S of the transistor 114 and the electronic control unit 20.

[0068] The comparator 70 compares the voltage signal supplied by the source S of the transistor 114 with a predetermined voltage threshold corresponding to a predefined detection distance which makes it possible to size the detection zone.

[0069] Example of implementation

[0070] With reference to [Fig.8], in a step E1, the switch 120 is closed to power the electrical loop of the radiating impedance module 110 and the resonant module 40, 45, 50 makes the detection antenna 112 resonate so that said antenna detection 112 emits microwave waves ft resonating at the predetermined fixed frequency, for example 2.45 GHz.

[0071] In the presence of a person 2, the microwave waves emitted ft by the detection antenna 112 are reflected on said person 2 and a portion of these reflected microwave waves fr return to the detection antenna 112 in a step E2.

[0072] In the absence of movement of the person 2 in the field of the detection antenna 112, the reflected microwave waves fr do not modify the impedance of the electrical loop of the radiating impedance module 110 which remains constant, so that the voltage signal S(V) delivered at the output of the source S of the transistor 114 is zero.

[0073] When the person 2 makes a movement, the frequency of the reflected microwave waves fr varies (the signal reflected by a moving target undergoes a frequency shift, called the Doppler effect), which modifies the impedance of the electrical loop of the radiating impedance module 110 and produces a voltage signal S(V) delivered at the output of the source S of the transistor 114, the amplitude of which also varies.

[0074] In a step E3, the electronic control unit 20 detects said movement of said person 2 when the absolute value of the amplitude of the voltage signal S(V) measured at the source S of the transistor 114 varies beyond a predetermined amplitude threshold SAP.

[0075] Preferably, the electronic control unit 20 analyzes the variations in the amplitude of the voltage signal S(V) received and determines the gesture performed by the person in a step E4.

[0076] [Fig.9] illustrates an example of a voltage signal S(V) as a function of time t for a movement made by person 2. During the movement, P2, P3, respectively, show a positive frequency shift when the hand approaches the detection antenna 112, and a negative shift when it moves away. P1 and P4 represent distant points where the signal is attenuated.

[0077] The invention makes it possible to detect the movements of a person 2 in a simple, inexpensive, rapid and efficient manner by detecting the change in impedance of the radiating impedance module 110.

Claims

1.

2.

3. Claims Device (10) for detecting the movement of a person (2) by microwave waves for a motor vehicle (1), said device (10) comprising a radiating impedance module (110) configured to be powered by a DC voltage supply (30) via a switch (120), said radiating impedance module (110) comprising a detection antenna (112) configured to resonate at a predetermined fixed frequency when said detection antenna (112) is coupled to a resonant module (40, 50), to emit microwave waves and to receive microwave waves reflected on said person (2), a MOSFET type transistor (114) and an impedance adapter (116) forming a closed-loop electrical circuit oscillating at the predetermined fixed frequency when said circuit is powered by the voltage supplied by said DC voltage supply (30), the detection antenna (112) being connected to the gate (G) of the transistor (114),the impedance adapter (116) being mounted between the gate (G) and the drain (D) of the transistor (114) and being configured to adapt the impedance of the detection antenna (112) to the impedance of the transistor (114) by being powered by the voltage supplied by said direct voltage supply (30), the source (S) of the transistor (114) being configured to be connected on the one hand to a ground and on the other hand to an electronic control unit (20), the voltage signal (S(V)) delivered by the source (S) of the transistor (114) being representative of the impedance variations of the radiating impedance module (110), the impedance being stabilized when the frequency of the waves reflected on the person (2) is equal to the frequency of the waves emitted at the predetermined fixed frequency, reflecting an absence of movement of the person (2),and variable when the frequency of the waves reflected on the person (2) varies by a frequency difference greater than a threshold compared to the predetermined fixed frequency, reflecting the detection of a movement of the person (2)., The device (10) of claim 1, wherein the predetermined fixed frequency is greater than or equal to 2.45 GHz. A device (10) according to any preceding claim, wherein the radiating impedance module (110) comprises an attenuator mounted between the detection antenna (112) and the gate (G) of the transistor (114), said attenuator being configured to attenuate the power of the detection antenna (112) and / or the voltage signal (S(V)) of the source (S) of the transistor (114).

4. Device (10) according to any one of the preceding claims, wherein the radiating impedance module (110) comprises a comparator (70) configured to compare the output voltage of the source (S) of the transistor (114) to a predetermined voltage threshold corresponding to a detection distance.

5. A device (10) according to any preceding claim, wherein the resonant module is a resonant antenna pattern (40) and the coupling between the sensing antenna (112) and said resonant antenna pattern (40) is electrical.

6. Device (10) according to any one of claims 1 to 4, wherein the resonant module is a resonator (45) and the coupling between the detection antenna (112) and said resonator (45) is magnetic.

7. Device (10) according to any one of claims 1 to 4 in which the resonant module is a communication antenna (50) of the vehicle (1), external to the device (10), for example of the BLE or UWB type.

8. Motor vehicle (1) comprising a detection device (10) according to any one of the preceding claims and an electronic control unit (20) connected to the source (S) of the transistor (114) and configured to receive the voltage signal (S(V)) delivered by the source (S) of the transistor (114) and to detect movement around the device (10) when the value of the voltage of the source (S) of the transistor (114) is greater than a predetermined threshold.

9. Vehicle (1) according to the preceding claim, in which the electronic control unit (20) is configured to detect a gesture from variations in the voltage value of the source (S) of the transistor (114) over a predetermined time interval.

10. Method for detecting the movement of a person (2) by microwave waves for a motor vehicle (1) using the detection device (10) according to any one of claims 1 to 7, said method comprising the steps of: - emission (El), by the detection antenna (112), of microwave waves resonating at a predetermined fixed frequency, - reception (E2) of the microwave waves reflected on said person (2), - detection (E3), by the electronic control unit (20), of a movement of said person (2) when the absolute value of the amplitude of the voltage signal (S(V)) measured at the source (S) of the transistor (114) varies beyond a predetermined amplitude threshold (SAP).

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