Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60R—VEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISE PROVIDED FOR
  • B60R25/00—Fittings or systems for preventing or indicating unauthorised use or theft of vehicles
  • B60R25/20—Means to switch the anti-theft system on or off
  • B60R25/24—Means to switch the anti-theft system on or off using electronic identifiers containing a code not memorised by the user
  • B60R25/245—Means to switch the anti-theft system on or off using electronic identifiers containing a code not memorised by the user where the antenna reception area plays a role
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B7/00—Radio transmission systems, i.e. using radiation field
  • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
  • H04B7/12—Frequency diversity

Definitions

• the present invention relates to a recognition device intended to control the unlocking of the doors of a vehicle and / or to authorize the starting of a vehicle.
• Radio frequency identification devices comprising a portable transmitter which transmits a coded carrier wave to a receiver.
• a receiver which receives this coded wave and compares the latter to a coded setpoint item of information and which, when the two items of information coincide, produces a locking signal for unlocking the doors of the vehicle.
• Figure 1 illustrates the problem related to the existence of these gray areas.
• the transmitter 1 transmits an identification signal towards the vehicle. Part of the transmitted signal travels the distance Ld indicated by arrow 40 and directly reaches the receiver 2. Another part of the transmitted signal indicated by arrows 50 and 51 reaches the receiver after reflection on obstacles for example the ground 2A which surround the vehicle. The signal thus reflected
• FIG. 1 represents a simplified diagram of the operation of an identification device.
• FIG. 1 we consider the path of a wave 40 which directly reaches the receiver and the path of a wave 50, 51 which is reflected against the ground 2A.
• Part of the wave 40 received directly by the receiver 2 has the form:
• a to A2. ej2 ⁇ Ld / ⁇ o A e
• Ld represents the distance traveled by the transmitted wave between the transmitter 1 and the receiver 2
• ⁇ o is the wavelength of the transmitted wave
• A2 is a function of the wavelength and of the distance traveled by the wave.
• the total wave arriving at the receiver therefore has the form:
• This wave varies as a function of the distance between the user and his vehicle and as a function of the frequency of the carrier wave emitted.
• An object of the present invention is to provide a reliable identification device despite the phase shift caused by the reflection of the waves against obstacles.
• the subject of the invention is an identification device intended to control the unlocking of the doors of a vehicle and / or to authorize the starting of a vehicle comprising a first transmitter which, on command, is capable of sending a first user identification signal on a carrier of a first given frequency (v1) to a receiver characterized in that it comprises a second transmitter capable of transmitting at least a second user identification signal on a carrier of a second frequency (v 2) different from the first frequency so that this second signal can serve as an identifying signal in the shadow areas of non-recognition of the first signal.
• v1 first given frequency
• v 2 second frequency
• the first and second transmitters are formed by a transmission unit comprising means for switching from the first to the second frequency and vice versa,
• these frequency switching means comprise a synthesizer
• the synthesizer includes a frequency divider controlled by a microcontroller and a phase locked loop,
• the first frequency (v1) is a harmonic of the second carrier frequency (v2)
• v1 the first frequency (v1) is substantially equal to 400 Megahertz.
• FIG. 2 represents for two different frequencies of the carrier a diagram of the attenuation of the waves received by the receiver as a function of the distance between the transmitter and the receiver,
• FIG. 3 represents a diagram of “gray areas” around a vehicle as a function of the wavelength of the carrier signal for two different frequencies of the carrier,
• FIG. 4 shows a first embodiment of a receiver according to the invention.
• FIG. 5 represents a second embodiment of a receiver according to the invention.
• FIG. 2 shows a diagram of the attenuation of the waves received by the receiver 2 as a function of the distance between the transmitter 1 and the receiver 2.
• the curves 10 and 20 represented on this diagram are theoretical curves which consider only the superposition of a direct incident wave 40 and a wave having been reflected 51 by the ground 2A (see FIG. 1).
• the receiver 2 receives a multitude of superimposed waves reflected by different obstacles such as the person carrying the receiver, the vehicle body, the walls of a building located nearby ect ...
• the waves reflected by such obstacles have a weaker influence and are therefore neglected later.
• Curve 10 represents the attenuation received by the receiver when the transmitted wave has a given frequency (v1).
• v1 the curve 10 of the attenuation of the wave which has a frequency (v1) has minima 11, 12, 13 at distances of approximately 4.5, 10.5 and 16 meters.
• a receiver 2 having for example a sensitivity of - 62 decibelmiliwatt (dBm) cannot detect the sending of an identification signal when the user is at 9.5 meters or at 16 meters, ie at a distance corresponding to at least 11 or 12. The identification device will therefore present gray areas of non-recognition of the user for these distances.
• the curve 20 in FIG. 2 also represents the attenuation of a wave emitted at a frequency (v2) different from the first frequency (v1). In this example, it is double the frequency (v1).
• the attenuation curve 20 has minima 21, 22, 23 at distances of 3.5, 8.5 and 14 meters and the Applicant has observed that the distances for which the phenomenon of attenuation of the wave is observed are different according to the frequency used. The position of the shadow zones of non-recognition of a user is therefore a function of the frequency used.
• an identification device which comprises a second transmitter which transmits an identification signal on a carrier of a second frequency (v2) different from the first frequency so that this second signal can serve as an identifying signal in the zones of non-recognition of the first signal.
• the Applicant had the idea of transmitting the identification signal at two different carrier frequencies.
• the gray areas being linked to the frequency, they therefore appear in different places, and this as a function of the frequency considered.
• the other frequency is preferably chosen so as to present a maximum of fields at this same distance. The radio range around the vehicle is not affected. Everything then passes to the user as if there was no gray area.
• the first frequency (v1) is substantially equal to
• the second frequency is equal to 800 MHz.
• the second frequency (v2) is equal to a harmonic of the first frequency (v1) and in particular an even harmonic.
• Figure 3 shows schematically the gray areas around the vehicle.
• the hatched areas 41 represent the shadow areas of non-recognition of the signal sent at the frequency (v1).
• the circled areas 42 represent the shadow areas of non-recognition of the signal sent at the frequency (v2).
• the geographic position of these waves is a function of the frequency used.
• the first frequency (v1) is different from the frequency (v2), these zones do not overlap. Thanks to the present invention, even if the user is in one of these zones, the receiver recognizes at least one of the two identification signals transmitted.
• the identification device according to the present invention is more reliable.
• the identification device comprises two independent transmitters 30, 31 cooperating with associated receivers arranged in the vehicle.
• the first transmitter 30 and its associated receiver operate at the frequency (v1).
• the second transmitter 31 and its associated receiver operate at the frequency of (v2).
• these transmitters 30, 31 can transmit an identification signal one after the other, offset or simultaneously. It is also possible to provide that the second signal is only sent if the user presses the transmitter's control button a second time.
• the first and the second transmitter 30, 31 are formed by a single transmission unit comprising means for switching from the first to the second frequency and vice versa.
• FIG. 5 represents an exemplary embodiment of a receiver 2 according to this second embodiment.
• This receiver consists of a synthesizer 39 connected to an amplifier 33 and an antenna 32.
• the synthesizer comprises a phase locked loop 36 (PLL) connected to a frequency divider 38.
• PLL phase locked loop
• the phase locked loop as well as the divider frequency are both controlled by a microcontroller 37.
• the use of a synthesizer allows to switch relatively quickly from a first frequency (v1) to a second frequency (v2).
• the identification device according to the present invention can also be used in so-called “hands-free” devices without actuation of a remote control unit.

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• Engineering & Computer Science (AREA)
• Computer Networks & Wireless Communication (AREA)
• Signal Processing (AREA)
• Mechanical Engineering (AREA)
• Lock And Its Accessories (AREA)

Applications Claiming Priority (3)

Publications (1)

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ID=8861126

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Family Cites Families (8)

• 2001
  • 2001-03-12 FR FR0103484A patent/FR2821961B1/fr not_active Expired - Fee Related
• 2002
  • 2002-03-11 US US10/471,357 patent/US7064457B2/en not_active Expired - Fee Related
  • 2002-03-11 EP EP02727395A patent/EP1387919A1/fr not_active Withdrawn
  • 2002-03-11 WO PCT/EP2002/002654 patent/WO2002072987A1/fr not_active Application Discontinuation
  • 2002-03-11 JP JP2002572222A patent/JP2004524461A/ja active Pending

Non-Patent Citations (1)

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