System and method for synchronization of data streams

• US 20070090924A1
• Filed: 10/20/2005
• Published: 04/26/2007
• Est. Priority Date: 10/20/2005
• Status: Active Grant

• Current Assignee: Ademco Inc. (Resideo Technologies, Inc.)
• Original Assignee: Honeywell International Inc.
• Inventors: Davis, Michael
• Granted Patent: US 7,772,963 B2
• Time in Patent Office: Days
• US Class Current: 340/10.1
• CPC Class Codes: H04L 67/12 specially adapted for proprietary or special-purpose networking environments, e.g. medical networks, sensor networks, networks in vehicles or remote metering networks
• CPC Class Codes: H04L 69/324 in the data link layer [OSI layer 2], e.g. HDLC

Abstract

A method of and system for acquiring data by a data reader from a transponder, such as in an RF proximity access card system, in which the data from the transponder does not require a preamble, framing bits or the like to denote the beginning of the data sequence. A radio frequency signal is continuously transmitted by the card reader to generate a radio frequency field. Once a transponder (such as one embedded in an access control card) enters the RF field, then response data is generated by the transponder and received by the card reader. The transmission of the radio frequency signal by the card reader is temporarily stopped on detection of the response data from the transponder, and then reinitiated by the card reader after it stops receiving response data from the transponder in order to regenerate the radio frequency field. The response data subsequently received from the transponder in the radio frequency field is then stored in memory. Since termination of the RF field will cause the transponder to transmit the response data sequence from the beginning once the RF field is reinitiated, the response data thusly received is known to have started from the beginning of the sequence, eliminating the need for a preamble or other type of framing bits.

Claims

1. A method of acquiring data by a data reader comprising the steps of:

transmitting a radio frequency signal to generate a radio frequency field;

receiving response data from a transponder in the radio frequency field;

terminating transmission of the radio frequency signal on detection of receiving said response data;

detecting termination of receipt of response data;

reinitiating transmission of the radio frequency signal to regenerate the radio frequency field on detection of termination of receipt of response data;

receiving subsequent response data from the transponder in the radio frequency field; and

storing the received subsequent response data in memory.

2. The method of claim 1 further comprising the step of terminating the regeneration of the radio frequency field after a predetermined amount of response data is received.

3. The method of claim 1 further comprising the step of terminating the regeneration of the radio frequency field after a predetermined amount of time has elapsed.

4. The method of claim 1 further comprising the steps of:

retrieving the received subsequent response data from memory; and

transmitting the retrieved subsequent response data on an associated data bus.

5. A data reading device comprising:

a radio frequency signal transmitter;

a radio frequency signal receiver; and

processing circuitry interconnected with the radio frequency signal transmitter and the radio frequency signal receiver, said processing circuitry adapted to;

cause the radio frequency signal transmitter to transmit a radio frequency signal to generate a radio frequency field;

detect that the radio frequency receiver has received response data from a transponder in the radio frequency field;

terminate transmission of the radio frequency signal on detection of receiving said response data;

detect termination of receipt of response data;

reinitiate transmission of the radio frequency signal to regenerate the radio frequency field on detection of termination of receipt of response data;

detect that the radio frequency receiver has received subsequent response data from the transponder in the radio frequency field; and

store the received subsequent response data in an associated memory.

6. The data reading device of claim 5, wherein said processing circuitry is further adapted to terminate the regeneration of the radio frequency field after a predetermined amount of response data is received.

7. The data reading device of claim 5, wherein said processing circuitry is further adapted to terminate the regeneration of the radio frequency field after a predetermined amount of time has elapsed.

8. The data reading device of claim 5, wherein said processing circuitry is further adapted to

retrieve the received subsequent response data from memory;

and

transmit the retrieved subsequent response data on an associated data bus.

9. An RF proximity access system comprising:

a) a data reading device comprising;

a radio frequency signal transmitter;

a radio frequency signal receiver; and

processing circuitry interconnected with the radio frequency signal transmitter and the radio frequency signal receiver, said processing circuitry adapted to;

cause the radio frequency signal transmitter to transmit a radio frequency signal to generate a radio frequency field;

detect that the radio frequency receiver has received response data from a transponder in the radio frequency field;

terminate transmission of the radio frequency signal on detection of receiving said response data;

detect termination of receipt of response data;

reinitiate transmission of the radio frequency signal to regenerate the radio frequency field on detection of termination of receipt of response data;

detect that the radio frequency receiver has received subsequent response data from the transponder in the radio frequency field; and

store the received subsequent response data in an associated memory; and

b) a plurality of access cards, each of said access cards comprising a transponder comprising;

means for receiving a radio frequency signal transmitted from the data reading device; and

means for transmitting response data to the data reading device uniquely identifying the access card amongst the plurality of access cards.

10. The RF proximity access system of claim 9, wherein said processing circuitry is further adapted to terminate the regeneration of the radio frequency field after a predetermined amount of response data is received.

11. The RF proximity access system of claim 9, wherein said processing circuitry is further adapted to terminate the regeneration of the radio frequency field after a predetermined amount of time has elapsed.

12. The RF proximity access system of claim 9, wherein said processing circuitry is further adapted to

retrieve the received subsequent response data from memory;

and

transmit the retrieved subsequent response data on an associated data bus.