阅读说明：本技术 用于机动车的存在检测系统的节能设备和方法 (Energy saving device and method for a presence detection system of a motor vehicle ) 是由 E·塞韦尔 C·韦尼涅 W·瓦萨克 于 2021-06-04 设计创作，主要内容包括：用于机动车的存在检测系统的节能设备和方法。用于检测靠近机动车的用户存在的存在检测系统的设备(1),被配置成：在称为“唤醒”时间间隔(R)的时间间隔期间激活压电元件(230)以稳定压电元件(230),一旦压电元件(230)已经稳定,控制向振荡器(120)的电压供应且向振荡器供应形成当前电压参考的参考电信号,使得收发器电路(10)在称为“传输”时间间隔(E)的时间间隔期间传输信号,在传输时间间隔(E)期间测量源于传输信号的反射信号的频率,测量传输信号的频率以及基于传输信号的频率的测量确定校正参考,允许收发器电路(10)的振荡器(120)在目标频率值处操作。本发明使得可能限制用于检测靠近机动车的用户存在的收发器设备的能耗。(Energy saving device and method for a presence detection system of a motor vehicle. Device (1) of a presence detection system for detecting the presence of a user in proximity to a motor vehicle, configured to: activating the piezoelectric element (230) during a time interval called "wake-up" time interval (R) to stabilize the piezoelectric element (230), once the piezoelectric element (230) has stabilized, controlling the voltage supply to the oscillator (120) and supplying the oscillator with a reference electrical signal forming a current voltage reference, such that the transceiver circuit (10) transmits a signal during a time interval called "transmission" time interval (E), measuring the frequency of a reflected signal originating from the transmitted signal during the transmission time interval (E), measuring the frequency of the transmitted signal and determining a correction reference based on the measurement of the frequency of the transmitted signal, allowing the oscillator (120) of the transceiver circuit (10) to operate at a target frequency value. The invention makes it possible to limit the energy consumption of the transceiver device for detecting the presence of a user close to the motor vehicle.)

1. A device (1) for a presence detection system for detecting the presence of a user close to a motor vehicle, said device (1) being intended to be installed in said vehicle and comprising a microcontroller (20) and a transceiver circuit (10), wherein:

the transceiver circuit (10) comprises an antenna (110) and an oscillator (120), wherein the oscillator (120) is configured to receive a supply voltage and a reference electrical signal and to supply a transmission signal when supplied by the supply voltage, the frequency of the transmission signal being a function of a reference formed by characteristics of the reference electrical signal, and wherein the antenna (110) is configured to transmit said transmission signal from the oscillator (120) so as to form a signal for transmission by the transceiver circuit (10);

the transceiver circuitry (10) is configured to receive via the antenna (110) a reflected signal originating from a signal transmitted by the transceiver circuitry (10);

the microcontroller (20) comprises a control unit (210) and a piezoelectric element (230);

the microcontroller (20) is configured to supply a reference electrical signal to the oscillator (120) and to drive supply of a supply voltage to the oscillator (120) such that the transceiver circuit (10) transmits periodically and during a transmission time interval (E);

and wherein the control unit (210) of the microcontroller (20) is configured to carry out the following steps in this order:

a) activating (E9) the piezoelectric element (230) during a time interval called "wake-up" time interval (R) in order to stabilize said piezoelectric element (230),

b) once the piezoelectric element (230) has stabilized, controlling (E1) the supply of voltage to the oscillator (120) and supplying the oscillator (120) with a reference electrical signal associated with a reference, called current reference, so that the transceiver circuit (10) transmits (E2) a signal during a transmission time interval (E),

c) during the transmission time interval (E):

-measuring (E5) the frequency of the Doppler signal derived from the reflected signal using a stabilized piezoelectric element (230), and

-measuring (E3) the frequency of the transmission signal supplied at the output of the oscillator (120) using a stabilized piezoelectric element (230),

d) using a comparison between the value of the target frequency and the measurement of the frequency of the transmission signal, a correction value of the reference is determined (E4), which makes it possible to reduce the difference between the value of the target frequency and the measurement of the frequency of the transmission signal when the oscillator (120) is supplied with a voltage and receives the corrected reference.

2. The device (1) according to claim 1, wherein the control unit (210) of the microcontroller (20) is configured to use said corrected reference as the current reference during a subsequent transmission time interval (E).

3. Device (1) according to claim 1 or 2, wherein the control unit (210) is configured to implement in step d) the following sub-steps:

-comparing the value of the target frequency with a measure of the frequency of the transmission signal;

-depending on whether the measure of the frequency of the transmitted signal is strictly greater or strictly less than the value of the target frequency, adding or subtracting a delta to or from the current reference in order to obtain said correction value of the reference.

4. The device (1) according to claim 1 or 2, wherein the control unit (210) is configured to implement the following steps in step d):

-determining said correction value of the reference based on pre-recorded data linking the value of the frequency of the transmission signal with the value of the reference supplied to the oscillator (120).

5. The device (1) according to any one of the preceding claims, wherein the piezoelectric element (230) is a quartz clock.

6. Device (1) according to any one of the preceding claims, wherein the duration of the wake-up time interval is between 100 μ s and 10 ms.

7. The device (1) according to any one of the preceding claims, wherein the control unit (210) is configured to implement the following steps in an initialization phase (P1) after the device (1) is powered on and before the first transmission time interval (E):

-driving the voltage supply to the oscillator (120) during a time interval called "settling" time interval;

-driving, during a stabilization time interval, stabilization of the transmission signal supplied at the output of the oscillator (120) at the target frequency, and thus determining an initial value of a current reference for stabilizing the oscillator (120) at the target frequency.

8. The device according to any one of claims 1 to 6, wherein the microcontroller (20) is configured to measure a temperature inside the device (1), preferably in the oscillator (120), and to deduce therefrom an initial value of a current reference for stabilizing the oscillator (120) at a target frequency at the measured temperature.

9. The device (1) according to any one of the preceding claims, wherein the microcontroller (20) is configured to modify the ratio between the repetition frequency of the transmission time interval and the repetition frequency of the step of measuring the frequency of the transmission signal (E3), in particular based on the operating mode of the vehicle, so as to avoid that the microcontroller (20) measures the frequency of the transmission signal in each transmission time interval (E).

10. The device (1) as claimed in any of the preceding claims, further comprising a battery (2) and a switch (30), the battery (2) being configured to supply the supply voltage to the oscillator (120), the switch (30) being connected between the battery (2) and the oscillator (120), and the switch (30) being driven by the microcontroller (20) such that the transceiver circuit (10) transmits periodically and during a transmission time interval (E).

11. The device (1) according to any one of the preceding claims, wherein the control unit (210) of the microcontroller (20) is further configured to detect (E7) the presence of a user in front of the device (1) when the frequency of the reflected signal is different from the frequency of the transmitted signal.

12. Device (1) according to any one of the preceding claims, wherein the frequency of the transmission signal is a function of the voltage of a reference electrical signal, said reference thus forming a voltage reference.

13. A motor vehicle comprising at least one device (1) according to any one of the preceding claims.

14. Method for detecting the presence of a user in proximity to a motor vehicle based on a device (1) according to any one of claims 1 to 12, comprising the steps of:

a) during a time interval called "wake-up" time interval (R), the control unit (210) activates the piezoelectric element (230) in order to stabilize said piezoelectric element (230),

b) once the piezoelectric element (230) has stabilized, the microcontroller (20) controls the voltage supply to the oscillator (120) and supplies the oscillator with a reference electrical signal associated with said current reference, so that the transceiver circuit (10) transmits the signal during a transmission time interval (E),

c) during the transmission time interval (E):

-the microcontroller (20) measures the frequency of the Doppler signal derived from the reflected signal, and

-the microcontroller (20) measures the frequency of the transmission signal supplied at the output of the oscillator (120),

d) using a comparison between the value of the target frequency and the measurement of the frequency of the transmission signal, the microcontroller (20) determines a correction value of the reference which makes it possible to reduce the difference between the value of the target frequency and the measurement of the frequency of the transmission signal when the oscillator (120) is supplied with a voltage and receives said corrected reference.

15. A method as claimed in claim 14, characterized in that it further comprises the step of detecting the presence of a user in front of the device (1) when the frequency of the reflected signal differs from the frequency of the transmitted signal.

Technical Field

The present invention relates to the field of automotive vehicles (motor vehicles), and more particularly to an apparatus and method for a presence detection system for detecting the presence of an approaching vehicle. Such a system is particularly intended to allow opening of one or more opening elements (opening elements) of the vehicle, such as the trunk.

Prior Art

In motor vehicles, it is known practice to use sensors for detecting the presence of a user close to the vehicle in order to unlock the door or open the trunk. In the case of doors, the sensor is typically mounted in the handle of the door. In the case of luggage, the sensor is typically mounted underneath the luggage, and the sensor needs to be able to detect the passage of the user's foot in front of the sensor.

One known sensor solution is based on a capacitance measurement that varies with respect to a reference value that characterizes the absence of a user in proximity to the sensor when the user is present. However, this type of sensor, known as a "capacitive" sensor, may prove inaccurate, thereby reducing its effectiveness and its reliability.

To remedy this drawback, another known sensor solution is based on radar ("acronym for radio detection and ranging") technology and consists in transmitting a high-frequency signal having a frequency of, for example, 24 GHz, and in measuring the frequency of the reflected signal. To this end, the sensor includes a microcontroller and transceiver circuitry. The transceiver circuit includes an antenna and an oscillator for transmitting a high frequency signal.

According to the current standard, high frequency signals must be transmitted within a predefined frequency range. In order to avoid that the frequency of the transmitted signal is outside this range, it is known practice in the prior art to use a phase locked loop (or PLL). When the circuit is started and before the signal is transmitted, the oscillator is powered during a time period called the "settling" time period, so that its frequency settles. This stabilization is achieved within the transceiver circuitry using a phase-locked loop. Another known embodiment for ensuring that the transmission is within the desired frequency range is an embodiment of frequency closed loop control using a microcontroller which controls the power supply to the transceiver circuit, measures the frequency using its own quartz oscillator, checks whether the frequency is actually equal to the value of the target frequency, adjusts the transmission frequency of the oscillator of the radar sensor if necessary, and then measures the transmission frequency again for checking purposes. Once this check has been performed, or once the oscillator has been stabilized by the phase locked loop, the microcontroller controls the transceiver circuit so that it continuously transmits a signal, generates the signal using the oscillator and transmits the signal using the antenna. The microcontroller then periodically measures the frequency of the Doppler signal derived from the reflected signal as a function of the frequency shift between the reflected signal and the signal transmitted by the transceiver circuitry. The non-zero frequency shift reflects the presence of a user in close proximity to the sensor. When the frequency of the reflected signal is the same as the frequency of the transmitted signal, this reflects by contrast the absence of movement of the user in front of the sensor. However, continuously transmitting signals proves to be particularly energy-consuming, which presents a significant drawback in motor vehicles.

To at least partially remedy this drawback, known practices transmit the signal discontinuously but periodically. The evolution (evolution) of parameters such as the temperature and humidity of the oscillator may modify the transmission frequency of the oscillator and thus the transceiver circuitry. Therefore, in the related art, the frequency of the oscillator of the radar sensor is checked before each signal transmission period and the oscillator of the radar sensor is stabilized. However, the phase of stabilizing the oscillator of the radar sensor and the phase of checking the frequency are particularly energy-consuming. Also in this case, repeating this step therefore means a significant consumption of energy by the sensor.

It is therefore an object of the present invention to at least partially remedy these disadvantages.

Disclosure of Invention

To this end, a first subject of the invention is a device for a presence detection system for detecting the presence of a user in proximity to a motor vehicle, said device being intended to be installed in said vehicle and comprising a microcontroller and a transceiver circuit, wherein:

the transceiver circuitry comprises an antenna and an oscillator, wherein the oscillator is configured to receive a supply voltage and a reference electrical signal and to supply a transmission signal when supplied thereto by the supply voltage, the frequency of the transmission signal being a function of a reference formed by characteristics of the reference electrical signal, and wherein the antenna is configured to transmit said transmission signal from the oscillator so as to form a signal for transmission by the transceiver circuitry;

a transceiver circuit configured to receive, via the antenna, a reflected signal derived from a signal transmitted by the transceiver circuit;

the microcontroller comprises a control unit and a piezoelectric element;

the microcontroller is configured to supply the reference electrical signal to the oscillator and to drive supply of the supply voltage to the oscillator such that the transceiver circuit transmits periodically and during a transmission time interval;

and wherein the control unit of the microcontroller is configured to implement the following steps in this order:

a) the piezoelectric element is activated during a time interval, called "wake-up" time interval, in order to stabilize the piezoelectric element,

b) once the piezoelectric element has stabilized, the voltage supply to the oscillator is controlled and a reference electrical signal associated with a reference, called the current reference, is supplied to the oscillator, so that the transceiver circuit transmits the signal during a transmission time interval,

c) during the transmission time interval:

measuring the frequency of the Doppler signal derived from the reflected signal using a stabilized piezoelectric element, and,

measuring the frequency of the transmission signal supplied at the output of the oscillator using a stabilized piezoelectric element,

d) using a comparison between the value of the target frequency and the measurement of the frequency of the transmission signal, a correction value of the reference is determined, which makes it possible to reduce the difference between the value of the target frequency and the measurement of the frequency of the transmission signal when the oscillator is supplied with a voltage and receives said corrected reference.

In a manner known per se, a Doppler signal represents a signal whose frequency is a function of the difference between the frequency of the reflected signal and the frequency of the signal transmitted by the transceiver circuit. The frequency difference increases with the speed of the target from which the reflected signal is reflected. The target is here formed by the user's leg.

The transceiver circuit and its oscillator are not powered continuously but intermittently and only during transmission time intervals in order to reduce the power consumption of the device according to the invention.

The transceiver circuit may be referred to as a "radar circuit".

The oscillator is configured to receive a supply voltage and a reference electrical signal. Preferably, the supply voltage is a signal that does not change from one transmission time interval to another. In contrast, a reference electrical signal is a signal that can vary from one transmission time interval to another.

The characteristic of the reference electrical signal forming the reference may comprise at least one of: voltage values (peak-to-peak value, average value, absolute value, etc. of the DC voltage), current values (peak-to-peak value, average value, absolute value, etc. of the DC current), output of digital signals, and the like. Thus, the reference may be a voltage reference, or other type of reference that is not a voltage reference, in particular a current reference, or a digital reference, etc.

During the measurement time interval, the frequency of the signal supplied at the output of the oscillator (transmission signal) is substantially equal to the frequency of the signal transmitted by the transceiver circuit, which is why the measurement of one is substantially equal to the measurement of the other.

The corrected reference may then be used as the current reference during a subsequent transmission time interval, preferably during the time interval immediately following the transmission time interval in which the corrected reference is determined. In other words, the oscillator is then controlled using a predetermined reference or current reference (using a measurement of the frequency of the signal supplied at the output of the oscillator) determined in a previous step and in particular during a previous transmission time interval. The invention thus makes it possible to avoid that the transceiver circuit has to perform a frequency check phase before each signal transmission. This therefore greatly reduces the power consumption of the device according to the invention compared to devices from the prior art. In particular, the invention makes it possible to dispense with (disconnect with) systematically using a phase-locked loop at the input of the oscillator to stabilize its frequency to the target frequency before each signal transmission of the transceiver circuit. The invention requires the implementation of a regular measurement of the frequency of the transmitted signal. The frequency of the transmitted signal is measured using a piezoelectric element, which must be stable in frequency beforehand. However, the power consumption of the microcontroller during operation including the piezo element is significantly lower than the power consumption of the transceiver circuit. The piezoelectric element also stabilizes faster than the oscillator. The stabilization of the piezo element required to implement the invention therefore consumes much less energy than the frequency stabilization of the oscillator itself, as is done in the prior art and in phase locked loops. Thus, the total consumption of the device can be significantly reduced, for example by a factor of 30 (the order of 30 times), compared to devices from the prior art based on the use of a phase locked loop before each signal transmission of the transceiver circuitry. Furthermore, according to the invention, the frequency stabilization of the oscillator is based on a frequency measurement step during a transmission time interval, which is carried out during the transmission of the signal for detecting the presence of the user. Therefore, the frequency stabilization of the oscillator does not increase the total signal transmission duration of the oscillator, thereby making it possible to reduce the power consumption of the device compared to the prior art.

Advantageously, the control unit of the microcontroller is configured to use said corrected reference as the current reference during a subsequent transmission time interval. Preferably, said subsequent transmission time interval comprises at least the transmission time interval immediately following the transmission time interval during which said measurement of the frequency of the transmission signal is effected.

The control unit may be configured to implement the following sub-steps in step d):

-comparing the value of the target frequency with a measure of the frequency of the transmission signal;

-depending on whether the measurement of the frequency of the transmitted signal is strictly greater or strictly less than the value of the target frequency, adding or subtracting an increment to or from the current reference in order to obtain said correction value of the reference.

When the frequency of the transmission signal is strictly greater than (or less than) the value of the target frequency, the increment is added to (or subtracted from) the current reference, or the increment is subtracted from (or added to) the current reference. Advantageously, the microcontroller then comprises a memory storing data comprising the value of the target frequency and the value of said increment.

The value of the increment is advantageously recorded in a preliminary calibration phase.

In addition or as a variant, the control unit may be configured to implement the following steps in step d):

-determining the correction value of the reference based on pre-recorded data linking the value of the frequency of the transmission signal with the value of the reference supplied to the oscillator.

The pre-recorded data may comprise a function and/or a curve and/or a table of values relating the value of the frequency of the transmission signal to the value of a reference supplied to the oscillator.

Advantageously, the microcontroller then comprises a memory storing said pre-recorded data relating the value of the frequency of the transmission signal to the value of the reference supplied to the oscillator.

The pre-recorded data relating the value of the frequency of the transmission signal to the value of the reference supplied to the oscillator are advantageously recorded in a preliminary calibration phase.

Advantageously, the piezoelectric element is a quartz clock, which allows to accurately measure the transmission frequency of the signal.

Preferably, the duration of the wake-up interval is between 100 μ s and 10 ms, preferably between 500 μ s and 5 ms.

Preferably, in an initialization phase after the device is powered on and before a first transmission time interval of the transceiver circuit, the microcontroller is able to supply a voltage to the oscillator during a time interval called "settling" time interval in order to settle said oscillator at a desired transmission frequency (preferably, the target frequency) and thus determine the initial reference value. In particular, the control unit is advantageously configured to implement the following steps in an initialization phase after power-up of the device and before the first transmission time interval:

-driving the voltage supply to the oscillator during a time interval called "settling" time interval;

during a settling time interval, driving the transmission signal supplied at the output of the oscillator to settle at the target frequency, and thus determining an initial value of a current reference for settling the oscillator at the target frequency.

As a variant, the microcontroller can measure the temperature inside the device, preferably in the oscillator, and can select a predetermined reference value (or an initial value of the current reference) in order to stabilize the oscillator in terms of frequency (preferably the target frequency) at the measured temperature. The predetermined value may be listed, for example, in a table stored in a memory area, in particular in a memory area of the microcontroller. In this embodiment, the device according to the invention comprises a temperature sensor, the sensitive element of which is advantageously arranged in the oscillator and configured to supply the measurement signal to the microcontroller.

According to one aspect of the invention, the microcontroller is able to modify the period of the transmission and measurement time intervals, that is to say the ratio between the repetition frequency of the transmission time intervals and the repetition frequency of the step of measuring the frequency of the transmitted signal, in particular on the basis of the operating mode of the vehicle (normal mode or standby mode), in order to avoid the microcontroller measuring the frequency of the signal transmitted in each transmission time interval, thus making it possible to save more energy.

Preferably, the device according to the invention further comprises a battery and a switch, wherein the battery is configured to supply said supply voltage to the oscillator, the switch is connected between the battery and the oscillator, and the switch is driven by the microcontroller such that the transceiver circuit transmits periodically and during a transmission time interval.

Preferably, the control unit of the microcontroller is further configured to detect the presence of a user in front of the device when the frequency of the reflected signal is different from the frequency of the transmitted signal. The detection uses a measurement of the frequency of the Doppler signal. When the frequency of the reflected signal is equal to the frequency of the signal transmitted by the transceiver circuit (and therefore equal to the frequency of the transmitted signal at the output of the oscillator), the frequency of the Doppler signal is zero, which reflects that the object located in front of the device has not moved. It is inferred that there is no user in front of the device. When the frequency of the reflected signal is different from the frequency of the signal transmitted by the transceiver circuit (and thus different from the frequency of the transmitted signal at the output of the oscillator), the frequency of the Doppler signal is non-zero, which reflects the movement of an object, such as a user's foot. Thereby inferring the presence of a user in front of the device.

Preferably, the frequency of the transmission signal is a function of the voltage of the reference electrical signal, said reference thus forming a voltage reference.

Another subject of the invention is a detection device for detecting the presence of a user close to a motor vehicle, said device being designed to be mounted in said vehicle and comprising a microcontroller and a transceiver circuit, said transceiver circuit comprising an antenna and an oscillator and being able to periodically transmit, during a transmission time interval and via said antenna, a signal at a target frequency from said oscillator and to receive a reflected signal originating from the signal transmitted via said antenna, said microcontroller comprising a control unit and a piezoelectric element, said control unit being able to:

-activating the piezoelectric element during a time interval called "wake-up" time interval in order to stabilize said piezoelectric element,

-once the piezoelectric element has stabilized, controlling the supply of voltage to the oscillator (allowing the oscillator of the transceiver circuit to operate at the value of the target frequency) based on a predetermined voltage reference at the stabilized frequency of the piezoelectric element, so that the transceiver circuit transmits signals during a time interval called "transmission" time interval,

-during the transmission time interval:

-measuring the frequency of a reflected (Doppler) signal originating from the transmitted signal,

-measuring the frequency of the transmission signal,

determining a new voltage reference based on the measurement of the frequency of the transmitted signal, allowing the oscillator of the transceiver circuit to operate at the target frequency value of the signal,

-detecting the presence of a user in front of the device when the frequency of the reflected signal is different from the frequency of the transmitted signal.

The invention also relates to a motor vehicle comprising at least one device as described above.

The invention also relates to a method for detecting the presence of a user in proximity to a motor vehicle based on a device as described above, said method comprising the steps of:

a) during a time interval, called "wake-up" time interval, the control unit activates the piezoelectric element, in order to stabilize it,

b) once the piezoelectric element has stabilized, the microcontroller controls the voltage supply to the oscillator and supplies the oscillator with a reference electrical signal associated with said current reference, so that the transceiver circuit transmits a signal during a transmission time interval,

c) during the transmission time interval:

-the microcontroller measures the frequency of the Doppler signal derived from said reflected signal, and

-the microcontroller measures the frequency of the transmission signal supplied at the output of the oscillator,

d) using a comparison between the value of the target frequency and the measurement of the frequency of the transmission signal, the microcontroller determines a correction value of the reference which makes it possible to reduce the difference between the value of the target frequency and the measurement of the frequency of the transmission signal when the oscillator is supplied with a voltage and receives said corrected reference.

Advantageously, the method according to the invention further comprises the step of detecting the presence of a user in front of the device when the frequency of the reflected signal is different from the frequency of the transmitted signal.

Preferably, the piezoelectric element is a quartz clock.

Also preferably, the duration of the wake-up interval is between 100 μ s and 10 ms, preferably between 500 μ s and 5 ms.

The invention also covers a method for detecting the presence of a user in proximity to a motor vehicle based on a device as described above, said method comprising the steps of:

-the control unit activates the piezoelectric element during a time interval called "wake-up" time interval for stabilizing said piezoelectric element,

-once the piezoelectric element has stabilized, the microcontroller controls the voltage supply to the oscillator based on a predetermined voltage reference at the stabilizing frequency of the piezoelectric element, so that the transceiver circuit transmits signals during a time interval called "transmission" time interval,

-during the transmission time interval:

-the microcontroller measures the frequency of the reflected signal originating from the transmitted signal,

-the microcontroller measures the frequency of the transmission signal,

-based on the measurement of the frequency of the transmitted signal, the microcontroller determines a new voltage reference allowing the oscillator of the transceiver circuit to operate at the target frequency value of the signal,

-detecting the presence of a user in front of the device when the frequency of the reflected signal is different from the frequency of the transmitted signal.

Drawings

Other features and advantages of the present invention will become apparent from a reading of the following description. This description is purely illustrative and should be read with reference to the accompanying drawings, in which:

fig. 1 schematically shows an embodiment of the device according to the invention.

Fig. 2 schematically shows an example of the operation of the device according to the invention.

Fig. 3 schematically shows an embodiment of the method according to the invention.

Detailed Description

The device according to the invention is intended to be installed in a motor vehicle in order to detect the presence of a user close to the vehicle, in particular the presence of the user's feet or hands.

Fig. 1 shows an embodiment of a device 1 according to the invention. The device 1 comprises a transceiver circuit 10 and a microcontroller 20, both powered by a battery 2 of the vehicle, and a switch 30 connected between the battery 2 and the transceiver circuit 10 and controllable by the microcontroller 20 so as to supply or not supply electric energy to said transceiver circuit 10.

Transceiver circuit 10

The transceiver circuit 10 includes an antenna 110 and an oscillator 120.

The transceiver circuit 10 is capable of periodically transmitting a signal of a predetermined frequency from the oscillator 120 and via the antenna 110 during a time interval referred to as a "transmission" time interval, and receiving a reflected signal derived from the signal transmitted via the antenna 110. To this end, the oscillator 120 is configured to receive the supply voltage from the battery 2 when the switch 30 is closed, and is configured not to receive any supply voltage when the switch 30 is open. Furthermore, the oscillator 120 is configured such that its oscillation frequency is driven using a reference electrical signal supplied by the microcontroller 20. In particular, the oscillation frequency of the oscillator 120, and therefore the frequency of the transmission signal supplied at the output of the oscillator 120, is a function of a reference formed by the characteristics of the reference electrical signal. In the following, but not by way of limitation, the reference is a voltage reference (DC voltage, taken at a fixed value during the transmission time interval considered) formed by the absolute value of the voltage of the reference electrical signal. The oscillator 120 may for example be designed to operate at a target frequency of 24.2 GHz for civil radar applications in a manner known per se. The output of the oscillator is connected to an antenna 110 for transmission of signals by the transceiver circuit 10.

In this example and advantageously, the transceiver circuit 10 further comprises a switch 115 connected between the output of the oscillator 120 and the antenna 110 and controllable by the microcontroller 20.

Here and advantageously, the transceiver circuit 10 further comprises a connection to a microcontroller20 and the microcontroller 20 measures the frequency of the transmission signal at the output of the oscillator by means of this frequency divider 130. The frequency divider 130 makes it possible to reduce the measured value of the frequency of the transmission signal supplied by the oscillator in order to bring this value into the range that the microcontroller can use numerically. In this example, and without limitation, frequency divider 130 divides the transmission frequency by 2²⁰ = 1048576. Transceiver circuit 10 also includes circuitry, not shown, that is configured to receive the reflected signal received by antenna 110 and to communicate the signal to microcontroller 20.

Microcontroller 20

The microcontroller 20 makes it possible to control the transceiver circuit 10 and comprises a control unit 210, a memory area 220 and a piezo element 230.

The control unit 210 is able to activate the piezo-element 230 during a time interval called "wake-up" time interval in order to stabilize said piezo-element 230. Preferably, the wake-up interval is between 0.1 and 1 ms in duration. Piezoelectric element 230 serves as a clock for frequency measurement by microcontroller 20.

Once the piezoelectric element has stabilized, the control unit 210 is able to control the voltage supply to the oscillator 120 (here via closing the switch 30) and supply the oscillator with a reference electrical signal. The characteristic of the reference electrical signal, here an absolute voltage value, forms the predetermined reference, here the predetermined voltage reference. The predetermined voltage reference advantageously allows the oscillator 120 to operate at a target frequency value of the signal to be transmitted. In practice, the conditions of use (in particular the temperature of the oscillator 120) may cause a frequency drift of the signal transmitted by the oscillator, in the case of a constant value of the voltage reference. For clarity, a definition of a current voltage reference representing the voltage reference delivered to the oscillator 120 at a given time is therefore given. The current voltage reference allows the oscillator 120 to operate at a target frequency value for the signal to be transmitted under initial use conditions. After a certain period of use of the device 1, the current voltage reference no longer allows the oscillator 120 to operate exactly at the target frequency value of the signal to be transmitted, due to a change in the use conditions of the device 1. The oscillator 120 then operates at a slightly offset value relative to the target frequency, e.g., greater or less than the target frequency. As such, the supply of the voltage to the oscillator 120 allows for the transmission of signals via the antenna 110 during a time interval referred to as a "transmission" time interval.

In this preferred example, the piezoelectric element 230 is in the form of a quartz clock, which makes it possible to oscillate very accurately at the desired frequency value, thus making it possible to measure the desired frequency value, in particular the frequency of the transmission signal at the output of the oscillator 120.

The control unit 210 is capable of measuring the frequency of the Doppler signal originating from the reflected signal during the transmission time interval. Measuring the frequency of Doppler signals in the context of detecting the presence of a user in front of a vehicle is a well known technique and will not be described further herein. It can be stated simply that the Doppler signal is formed using a multiplier (multiplier) which on the one hand receives the frequency at the inputAnd on the other hand receives the frequency supplied at the output of the oscillator 120And a signal is supplied at an output, one of the components of the signal being at a frequencyTo (3). The component forming the Doppler signal is isolated using a frequency filter. The device 1 has various elements, not shown, which allow said measurement of the Doppler signal, in particular said multiplier, and a coupler, which is arranged at the output of the oscillator 120 and is able to direct a large part of the signal to the antenna 110 and a small part of the signal to the multiplier.

In parallel, during this same transmission time interval, the control unit 210 is also able to measure the frequency of the signal transmitted by the antenna 110 and determine a new reference (here a new voltage reference) based on the frequency of the transmission signal thus measured, allowing the oscillator 120 to operate at the target frequency in the next transmission. In practice, the control unit measures the frequency of the signal at the output of the oscillator 120 upstream of the antenna 110, it being understood that when the switch 115 is closed, the frequency of the signal transmitted by the antenna is substantially equal to the frequency of the signal transmitted by the oscillator 120. The new reference value may be referred to as a "corrected value of reference". This is the value of the reference that allows the oscillator to operate at the value of the target frequency under the current usage conditions.

Advantageously, a counter (not shown) may be used to measure the frequency of the transmitted signal, the counter being driven by the control unit 210 and being electrically connected to the frequency divider 130, for example. The counter uses the piezoelectric element 230 as a clock. According to the invention, the piezo element 230 should therefore be stable in frequency before the measurement of the frequency of the transmission signal.

The value of the predetermined reference may have been determined in a previous transmission time interval or in any previous transmission time interval. Next, the obtained new reference is used as a reference in the subsequent transmission time interval. Preferably, the new value of the reference is determined periodically, e.g. every 3 or 4 transmission time intervals.

In an initialization phase after power-up of the device 1 and before a first transmission time interval of the transceiver circuit 10, the microcontroller 20 may be able to supply a voltage to the oscillator 120 and a reference electrical signal thereto during a time interval called "settling" time interval in order to settle said oscillator at a desired transmission frequency (here called target frequency) and thus determine an initial reference value.

As a variant, the microcontroller 20 may be able to measure an initial temperature inside the device 1, preferably in the oscillator 120, and deduce therefrom an initial reference value for stabilizing the oscillator 120 in frequency at the desired transmission frequency (herein referred to as target frequency) at the measured temperature. This variant advantageously uses a table stored in a memory, linking the reference value and the temperature value, for the operation of the oscillator 120 at the target frequency. The memory is, for example, a memory area 220 of the microcontroller 20 or an added memory not shown. In one embodiment, the microcontroller 20 is able to modify the time period of the transmission and measurement time intervals, in particular based on the operating mode of the vehicle (normal mode or standby mode), in order to avoid the microcontroller 20 measuring the frequency of the signal transmitted in each transmission time interval, thereby making it possible to save more energy. In particular, the transmission time period of the signal of the transceiver circuit (via the oscillator 120 and the antenna 110) and the measurement time period of the frequency of the signal transmitted by the transceiver circuit may be adapted based on the changes of temperature and humidity. For example, if the temperature and humidity do not change or change only slightly and/or if the vehicle is in a standby mode, the microcontroller 20 may increase the transmission time period (that is, decrease the repetition frequency of the transmission time interval) and also not measure the frequency of the signal transmitted in each transmission. In contrast, if the temperature and humidity change rapidly and/or if the vehicle is in a normal operating mode, the microcontroller may reduce the transmission time period (that is, increase the repetition frequency of the transmission time interval) and also measure the frequency of the signal transmitted in each transmission.

The control unit 210 is configured to measure the frequency of the Doppler signal obtained from the signal transmitted by the transceiver circuit 10 and reflected (or backscattered) from the user (e.g. his moving foot). Preferably, the control unit 210 is then able to detect the presence of a user in front of the device 1 when the frequency of the reflected signal is different from the frequency of the transmitted signal (non-zero frequency of the Doppler signal). As a variant, the presence detection is implemented in an added device.

To perform all these functions, microcontroller 20 is able to implement a list of instructions stored in its memory area 220.

Implementation of

The invention will now be described in terms of its implementation with reference to fig. 2 and 3. Fig. 2 shows an example of the operation of the device 1, wherein the top graph shows the evolution of the current intensity consumed by the device 1, the middle graph shows the periodic transmission time interval E of the transceiver circuit 10 and the bottom graph shows the initialization phase P1 and the measurement phase P2, including the periodic standby V, wake-up R and measurement M time intervals (of the time period T).

First, when the device 1 starts up, the microcontroller performs an initialization phase P1 in which it opens the switch 115 (in order to prevent the signal at the output of the oscillator 120 from being transmitted to the antenna 110), closes the switch 30 (in order to supply the oscillator 120 with a voltage), and then applies a reference electrical signal forming a reference at the input of the oscillator 120. During this initialization phase P1, microcontroller 20 searches for the value of the reference required for oscillator 120 to transmit at the target frequency. The target frequency lies within a frequency range authorized by the standard and has a value of, for example, 24.2 GHz. In doing so, the oscillator 120 will need to be stable in frequency during the non-zero time interval. In order to stabilize the oscillator 120 so that the signal transmitted (by the oscillator 120 and hence by the transceiver circuit 10) is at the desired target frequency, the microcontroller 20 adjusts the reference at the input of the oscillator 120 by trial and error or by closed loop control if required. Here, the reference is formed by a voltage, but is not limited thereto. As a variant, it may be formed by any characteristic of the electrical signal, for example its current, other than its voltage. Once the oscillator 120 has stabilized, the microcontroller 20 records in its memory area 220 the reference defined at the input of the oscillator as a starting or initial reference. The microcontroller 20 may then optionally close the switch 115 in order to check the effect of the connection to the antenna 110 on the frequency of the oscillator 120 and refine the initial reference value even more. In particular, the frequency of the oscillator 120 may be particularly influenced by the connection of the antenna 110 to said oscillator 120. It should be noted that in the initialization phase P1, there is no transmission of signals of the transceiver circuit 10 (or only at the end of the initialization phase P1, once the frequency of the oscillator 120 has stabilized and when the switch 115 is closed). In particular, in this phase of searching for an initial reference, the transmission frequency may be outside the authorized range. However, during this initialization phase P1 (switch 30 closed), power is still supplied to the transceiver circuit 10.

Once the initialization phase P1 is over, the device 1 operates in a phase called the "measurement" phase P2. This measurement phase P2 will be repeated periodically. In step E1 of the measurement phase P2, the microcontroller 20 first closes the switch 115, keeps the switch 30 closed, and applies at the input of the oscillator 120 the starting reference determined during the initialization phase P1. The oscillator 120 is thus directly operable. In particular, it then directly transmits a signal oscillating substantially at the target frequency, for which it is calibrated beforehand in an initialization phase P1. When the usage conditions, such as temperature and/or humidity, have not changed since the initialization phase P1, the signal transmitted by the oscillator 120 oscillates precisely at the target frequency. As a variant, the use conditions may have changed since the initialization phase P1. In this case, the reference defined in the initialization phase P1 no longer corresponds to the transmission at the target frequency, and the signal transmitted by the oscillator 120 oscillates at a frequency different from said target frequency. Once the start reference has been applied at the input of the oscillator 120, the transceiver circuit 10 transmits a signal via the antenna 110 during a first time interval, referred to as the "transmission" time interval E, in step E2. One function of the signals transmitted by transceiver circuitry 110 is to detect nearby users. The signal transmitted by the transceiver circuit 10 corresponds to the signal supplied by the oscillator 120 and then transmitted by the antenna 110. Thus, the signal oscillates at substantially the same frequency as the oscillator and switch 115 is closed.

During the transmission of the signal by the transceiver circuit 10, the control unit 210 of the microcontroller 20 measures the frequency of the signal transmitted by the transceiver circuit 10 in step E3. In practice, the measurement is performed on the signal transmitted by the oscillator 120 via the frequency divider 130. The frequency divider 130 reduces the frequency of the signal transmitted by the oscillator 120 to a value that can be measured within the microcontroller 20. The frequency measurement uses the counter of the microcontroller 20 and a clock, here formed by the piezo element 230.

In step E4, microcontroller 20 determines a correction value for the reference, also referred to as a new reference or "real-time" reference. The real-time reference is determined based on measurements of the frequency of the transmitted signal. If the oscillator 120 is supplied with the real-time reference, it will allow the oscillator 120 of the transceiver circuit 10 to operate close to at the exact value of the target frequency. Thus, if oscillator 120 is supplied with the real-time reference, it will allow oscillator 120 to operate close to the exact value at the target frequency in the subsequent transmission time interval. The real-time reference is stored in the memory area 220.

In practice, the real-time reference may be obtained simply by comparing the target frequency with the frequency measured in step E3. If the target frequency is greater than the frequency measured in step E3, the increment is added to the current reference (i.e., the reference applied at the input of the oscillator during said step E3) or subtracted from the current reference. In contrast, if the target frequency is less than the frequency measured in step E3, an increment is subtracted from or added to the current reference. Advantageously, the value of the increment is determined in a preliminary calibration step. This solution does not always allow operation exactly at the target frequency, however, it does avoid the accumulation of excessive frequency drift over time (buildup). It is thus ensured that the oscillator 120 always transmits in the desired frequency band.

As a variant, the real-time reference may be obtained using a table and/or a curve and/or a function linking the value of the frequency of the signal transmitted by the oscillator 120 (or the transceiver circuit) with the value of the reference at the input of the oscillator. The data used (tables and/or curves and/or functions of values) are advantageously determined in a preliminary calibration step.

During this transmission time interval E, in parallel with steps E3 and E4, the control unit 210 of the microcontroller 20 also measures in step E5 the frequency of the Doppler signal obtained using the reflected signal.

At the end of the transmission time interval E, and in step E6, the microcontroller 20 stops supplying voltage to the oscillator 120, so that it stops operating and the transceiver circuit 10 stops transmitting signals, thus saving the vehicle's electrical energy. To this end, microcontroller 20 drives the opening of switch 30 and the opening of switch 115. It also stops sending references to the input of oscillator 120.

In an optional step E7, the control unit 210 detects the presence of a user in proximity to the device 1. The detection is based on detecting the difference between the frequency of the reflected signal and the frequency of the signal transmitted by the transceiver circuit (Doppler effect), which is synonymous with the movement of a nearby user, for example the passage of a foot. When the control unit 210 detects the presence of a user close to the device 1, it activates a function of the vehicle, such as for example unlocking an opening element in which the device 1 is installed.

Upon completion of step E6 and possibly E7, microcontroller 20 puts itself in a standby state during a standby interval V in which it consumes little power.

In step E8, the control unit 210 of the microcontroller 20 wakes up just before the beginning of the subsequent transmission time interval E. Then, in step E9, it controls the supply of voltage to the piezoelectric element 230 during a time interval called the "wake up" time interval R, allowing the piezoelectric element 230 to stabilize, with the switch 115 and the switch 30 still open.

At the end of this wake-up time interval R, and in step E10, the control unit 210 closes the switch 30 and the switch 115, so that a signal is transmitted by the transceiver circuit 10 during the new transmission time interval E.

The microcontroller 20 then runs steps E3 to E10 again periodically, as long as the device 1 is operable in each transmission time interval E using the previously defined reference (defined in the initialization phase, in particular for the first transmission time interval, or defined in the previous transmission time interval and stored (remembered) in a memory, in particular the transmission time interval immediately preceding the transmission time interval under consideration).

It should be noted that, as a variant, steps E3 and E4 may not be implemented systematically in each transmission time interval E, but in a more temporally spaced manner. In particular, if the temperature and humidity levels vary very slowly or do not vary, it may be advantageous to keep the same reference for a plurality of consecutive transmission time intervals E, in order to avoid measuring the frequency of the transmission signal and calculating a new real-time reference in each transmission time interval E, thus saving power.

It should also be noted that the device 1 can operate during normal operation of the vehicle (the electrical system of the vehicle is activated, for example the engine is started) and during operation in a standby mode of the vehicle (the electrical system of the vehicle is in standby mode, the engine is off).

The invention is not limited to the examples described above and also covers many variants, including in particular:

a variant in which the oscillator is not controlled by the absolute value of the voltage of the reference electrical signal, but by any other characteristic of said signal, such as the absolute current value, the average current or voltage value, etc.;

in a variant, without the switch 115, the initialization phase can be implemented in the following environment: temporarily authorizing transmission at a sufficiently low power outside of the authorized band;

a variant in which the actuation of the switch 30 is replaced by the actuation of the battery itself;

-a variant wherein the step of detecting a user is performed outside the microcontroller using Doppler frequency measurements or the like supplied by the microcontroller.