Patent ID: 11914020
Assignee: VITESCO TECHNOLOGIES GMBH
Field: Measurement (Instruments)
Classification: CPC G  B | IPC B  G

Claim 0:
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 so as to receive a supply voltage and a reference electrical signal, and to supply a transmission signal when it is supplied by the supply voltage, with a frequency of the transmission signal that is a function of a reference formed by a feature of the reference electrical signal, and wherein the antenna (110) is configured so as to transmit said transmission signal from the oscillator (120) so as to form a signal that is transmitted by the transceiver circuit (10);
the transceiver circuit (10) is configured so as to receive, via said antenna (110), a reflected signal resulting from the signal transmitted by the transceiver circuit (10);
the microcontroller (20) comprises a control unit (210) and a piezoelectric element (230);
the microcontroller (20) is configured so as to supply the reference electrical signal to the oscillator (120), and to drive the supply of the supply voltage to the oscillator (120) such that the transceiver circuit (10) transmits periodically and during transmission time intervals (E);, and wherein the control unit (210) of the microcontroller (20) is configured so as to implement the following steps, in this order:
a) activate (E9) the piezoelectric element (230) during what is called an “awake” time interval (R), in order to stabilize said piezoelectric element (230),
b) once the piezoelectric element (230) has stabilized, control (E1) the supply of voltage to the oscillator (120) and supply the oscillator (120) with a reference electrical signal associated with what is called a current reference, so that the transceiver circuit (10) transmits (E2) a signal during a transmission time interval (E),
c) during said transmission time interval (E):
using the stabilized piezoelectric element (230), measure (E5) the frequency of a Doppler signal resulting from said reflected signal, and
using the stabilized piezoelectric element (230), measure (E3) the frequency of the transmission signal supplied at the output of the oscillator (120),

d) using a comparison between the value of a target frequency and the measurement of the frequency of the transmission signal, determine (E4) a corrected value of the reference, the corrected value of the reference making it possible to reduce a 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.