Passive communication device and passive access control system

• US 20050052286A1
• Filed: 06/03/2002
• Published: 03/10/2005
• Est. Priority Date: 06/13/2001
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Perraud, Eric, Burri, Michel, Baylac, Bruno
• Granted Patent: US 7,286,042 B2
• Time in Patent Office: Days
• US Class Current: 340/825.720
• CPC Class Codes: B60C 23/0413 Wireless charging of active radio frequency circuits
• CPC Class Codes: B60C 23/0433 Radio signals
• CPC Class Codes: B60C 23/0461 externally triggered, e.g. by wireless request signal, magnet or manual switch

Abstract

A communication device comprising an internal power source, receiver means for receiving signals transmitted from the base station, and processing means selectively responsive to an interrogation signl received from a base station to generte a data signal fro transmission to the base station. The receiver means comprises a first receiver element and a second receiver element, the first receiver element having lower power consumption than the second receiver element does when energised. At least during a standby state of the device, the internal power source energises the first receiver element so as to detect the presence of a entergised from the internal power source. The first receiver element is responsive to detection of a received signal to trigger an active state of oepration of the communication device in which the internal power source energises the second receiver element so that the second receiver element is selectively responsive to a characteristice of the signal received to actuate the processing means. The invention is applicable to access control systems, especially to cehicle access control systems, and also to tyre pressure monitoring systems.

Claims

1. A passive communication device for a communication system having a base station, the communication device comprising an internal power source, receiver means for receiving signals transmitted from the base station, processing means selectively responsive to an interrogation signal received from the base station by said receiver means to generate a data signal for transmission to the base station, and said communication device being selectively responsive to detection of a signal by said receiver means to enable said internal power source to energise said processing means

characterised in that said receiver means comprises a first receiver element and a second receiver element, said first receiver element having lower power consumption than said second receiver element when energised,

said communication device being arranged so that, at least during a standby state of the device, said internal power source energises said first receiver element so as to detect the presence of a received signal, said second receiver element and said processing means not being energised from said internal power source,

said first receiver element being responsive to detection of a received signal to trigger an active state of operation of said communication device in which said internal power source energises said second receiver element so that said second receiver element is selectively responsive to a characteristic of the signal received to actuate said processing means.

2. A passive communication device as claimed in claim 1, characterised in that said characteristic to which said second receiver element is selectively responsive is a carrier frequency of the signal received, said second receiver element being arranged to actuate said processing means if said carrier frequency is between upper and lower limits.

3. A passive communication device as claimed in claim 2, characterised in that said second receiver element comprises an input receiver element, counter means for counting cycles of the received signal and timing means for defining a time period corresponding to the number of said cycles counted.

4. A passive communication device as claimed in claim 1, characterised in that said processing means comprises demodulator means responsive to a modulation of the received signal, said internal power source being arranged to energise said demodulator means in said active state in response to actuation by said second receiver element.

5. A passive communication device as claimed in claim 1, characterised in that said receiver means comprises reset means for triggering said standby state in the absence of a signal received by said first receiver element and of the transmission of a signal by the communication device.

6. A passive communication device as claimed in claim 5, characterised in that said reset means is responsive to said characteristic of the signal received by said first receiver element being outside upper and lower limits for triggering said standby state.

7. A passive communication device as claimed in claim 1, characterised in that said receiver means comprises antenna means for receiving transmitted signals and switch means for connecting said antenna means with said first receiver element, said switch means being responsive to detection by said first receiver element of a signal received by said antenna means to trigger connection of said antenna means with said second receiver element.

8. A passive communication device as claimed in claim 1, characterised in that said first and second receiver elements present frequency pass bands with upper limits, the upper limit of the frequency pass band of said first receiver element being lower than the upper limit of the frequency pass band of said second receiver element.

9. A passive access control system comprising a passive communication device as claimed in claim 1 and including said base station, said passive communication device and said base station communicating by electromagnetic signals, said passive communication device being included in a portable device and said base station being responsive to said data signal for selectively enabling access for a user of the portable device, characterised in that a carrier frequency of said interrogation signal transmitted by said base station is in the Low Frequency range (30 to 300 kHz) and in that a carrier frequency of said data signal transmitted by said portable device is in the Ultra High Frequency range (300 to 3000 MHz).

10. A passive access control system comprising a passive communication device as claimed in claim 1 and including said base station, characterised in that said communication device is included in a portable device, said base station being responsive to an action of the user of the system to transmit said interrogation signal and being selectively responsive to reception of a corresponding data signal from said communication device selectively to enable access for the user.

11. A tyre pressure monitoring system comprising a passive communication device as claimed in claim 1 and including at least one of said base stations,

characterised in that said base station is mounted on a non-rotating part of said vehicle and said communication device is mounted in a wheel of the vehicle in association with pressure sensing means for providing data to said processing means, said base station transmitting said interrogation signal at intervals of time and being responsive to reception of the corresponding data signal from said communication device to register said data.