Passive entry and/or passive go system and associated operating method

• US 20070257771A1
• Filed: 04/25/2007
• Published: 11/08/2007
• Est. Priority Date: 04/25/2006
• Status: Active Grant

• Current Assignee: Atmel Corporation (Microchip Technology Incorporated)
• Original Assignee: Atmel Corporation (Microchip Technology Incorporated)
• Inventors: Moser, Daniel, Moser, Helmut
• Granted Patent: US 8,525,672 B2
• Time in Patent Office: Days
• US Class Current: 340/5.610
• CPC Class Codes: B60R 2325/105 Radio frequency identification data [RFID]
• CPC Class Codes: B60R 25/24 using electronic identifiers containing a code not memorised by the user
• CPC Class Codes: G07C 2009/00547 starting ignition
• CPC Class Codes: G07C 9/00309 operated with bidirectional data transmission between data carrier and locks

Abstract

A passive entry and/or passive go system and am associated operating method is provided. According to an embodiment of the invention, the following steps are performed in an electronic key of the passive entry and/or passive go system: generation of a reference input value, supplying the antenna circuit with the reference input value, measurement of the characteristic parameters, while the antenna circuit is supplied with the reference input value, storage of the characteristic parameters, measurement of a first output value of the antenna circuit, and determination of the field strength from the first output value and the characteristic parameters, whereby an effect of the characteristic parameters on the field strength is compensated. Use, for example, in motor vehicles.

Claims

1. A method for operating a passive entry and/or a passive go system, the system having a base station that is provided in a motor vehicle and at least one electronic key assigned to the base station, the method comprising:

generating a carrier signal by the base station;

receiving the carrier signal at least one antenna of an antenna circuit of the electronic key, the antenna circuit generating an output value, which is a function of a field strength of the carrier signal and a function of characteristic parameters of the antenna circuit;

determining, in the electronic key, a distance between the base station and the electronic key based on the field strength; and

operating functions of the system are carried based on the determined distance,

wherein, in the electronic key, the method further comprises;

generating a reference input value;

supplying the antenna circuit with the reference input value;

measuring the characteristic parameters while the antenna circuit is supplied with the reference input value;

storing the characteristic parameters;

measuring a first output value of the antenna circuit; and

determining the field strength from the first output value and the characteristic parameters, wherein an effect of the characteristic parameters on the field strength is compensated.

2. The method according to claim 1, wherein the functions of the system comprise an unlocking, a locking, and/or starting of the motor vehicle as a function of the determined distance.

3. The method according to claim 1, wherein the reference input value is generated in the form of a reference input voltage and/or a reference input current with a predefined reference frequency and reference amplitude, wherein a second output value is measured at an applied reference input value, and wherein the characteristic parameters are determined from the second output value.

4. The method according to claim 3, wherein, to determine the field strength, a quotient is formed from the first output value and the second output value.

5. The method according to claim 3, wherein the reference frequency is set equal to a frequency of the carrier signal.

6. The method according to claim 3, wherein the reference frequency is derived from a frequency of the carrier signal.

7. The method according to claim 1, wherein a distance between the antenna and a transmitting antenna of a transmitter of the carrier signal is determined based on the determined field strength.

8. The method according to claim 7, wherein the field strength is determined at a second antenna and at a third antenna, and a distance between the antennas and a transmitting antenna of a transmitter of the carrier signal is determined from the determined field strengths.

9. The method according to claim 1, wherein the antenna and a transmitting antenna of a transmitter of the carrier signal are coupled mutually.

10. The method according to claim 1, wherein a parallel resonant circuit or a series resonant circuit is formed by the antenna circuit.

11. The method according to claim 1, wherein the frequency of the carrier signal is within a range of 50 KHz to 150 KHz or within a range of 5 MHz to 25 MHz.

18. The method according to claim 8, wherein at least one of the antennas is perpendicular to an adjacent antenna.

12. A passive entry and/or passive go system comprising:

a base station for placement in a motor vehicle;

at least one electronic key, which is assigned to the base station; and

at least one antenna circuit arranged on the electronic key, the electronic key including at least one antenna and an output terminal at which an output value is applied in the form of an output voltage and/or an output current, which is a function of the field strength and a function of characteristic parameters of the antenna circuit,

wherein the electronic key comprises;

a reference input value generating unit for generating a reference input value in the form of a reference input voltage and/or a reference input current with a known reference frequency and reference amplitude and

an activatable switching unit, which is coupled to the antenna circuit and the reference input value generating unit and which supplies the antenna circuit with the reference input value as a function of the activation state or decouples the antenna circuit from the reference input value.

13. The passive entry and/or passive go system according to claim 12, wherein the reference input value generating unit is an oscillator.

14. The passive entry and/or passive go system according to claim 12, wherein the key medium comprises an evaluation unit, which is designed in such a way that it evaluates an output value when a reference input value is not applied and an output value when a reference input value is applied for determining the field strength.

15. The passive entry and/or passive go system according to claim 12, wherein the antenna circuit has an antenna coil and a capacitor, which together form a parallel resonant circuit.

16. The passive entry and/or passive go system according to claim 15, wherein the switching unit has a first switch, which is looped between a terminal of the capacitor and a reference potential, and a second switch, which is looped between the terminal of the capacitor and a terminal of the reference input value generating unit at which the reference input value is applied.

17. The passive entry and/or passive go system according to claim 12, wherein the antenna circuit is designed for mutual coupling with a transmitting antenna of a transmitter of the carrier signal.