System and method for communicating with multiple transponders

• US 6,535,109 B1
• Filed: 12/01/1998
• Issued: 03/18/2003
• Est. Priority Date: 12/01/1998
• Status: Expired due to Term

• Current Assignee: Integrated Sensor Solutions, Inc. (Texas Instruments, Inc.)
• Original Assignee: Texas Instruments Sensors and Controls Incorporated (Texas Instruments, Inc.)
• Inventors: Mahdavi, Pourang
• Primary Examiner(s): Horabik, Michael
• Assistant Examiner(s): BANGACHON, WILLIAM L
• Application Number:
  US09/203,154
• Time in Patent Office: 1,568 Days
• Field of Search: 340/10.3, 340/2, 340/1, 340/10.33, 340/34, 340/10.32, 340/33, 340/10.34, 340/35, 340/572, 370/445, 342/43
• US Class Current: 340/10.3
• CPC Class Codes: G06K 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer
• CPC Class Codes: G06K 7/10059 transponder driven

Abstract

The object of the invention is a system and method for identifying and communicating with a plurality of transponders which are at the same time in the same interrogation field. The system is based on an interrogator which sends interrogation bursts in a periodical manner, and transponders which send the response back with a random delay related to the end-of-burst event. The system is primarily suitable for passive (no additional power supply) transponders, but can also be used for active transponders.

Claims

1. The method of reading a plurality of transponders comprising:

(a) pulsing of an interrogation field which is sent by a reader generating End Of Burst Signals as a time base;

(b) generating a Request To Send signal consisting of a defined pattern and a random value with a delay after the End Of Burst signals by each of the plurality of transponders;

(c) providing a second End Of Burst signal by the reader after receiving a valid Request To Send signal from one of the plurality of transponders;

(d) transmitting the main data by one of the plurality of transponders; and

(e) detecting collisions at the reader when the Request To Send signals of at least two of the plurality of transponders are sent substantially simultaneously, whereby a valid defined pattern and random value cannot be read by the reader.

2. The method of claim 1 wherein the one transponder enters sleep mode after the data transmission is acknowledged by another End Of Burst Signal from the reader.

3. The method of claim 2 repeating steps (c) and (d) for the remaining transponders of the plurality of transponders.

4. The method of claim 1 further comprising continuing to pulse the interrogation field by the reader following detection of a collision at the reader.

5. The method of claim 1 wherein the interrogation field is pulsed periodically.

6. A system of reading a plurality of transponders comprising:

means for pulsing of an interrogation field which is sent by a reader generating End of Burst Signals as a time base;

means for generating a Request To Send signal consisting of a defined pattern and a random value with a delay after the End of Burst signals by each of the plurality of transponders;

means for providing a second End of Burst signal by the reader after receiving a valid Request To Send signal from one of the plurality of transponders;

means for transmitting the main data by one of the transponders; and

means for detecting collisions at the reader when the Request To Send signals of at least two of the plurality of transponders are sent substantially simultaneously, whereby a valid defined pattern and random value cannot be read by the reader.

7. The system of claim 6 wherein the one transponder enters sleep mode after the data transmission is acknowledged by another End of Burst Signal from the reader.

8. The system of claim 6 wherein the means for pulsing an interrogation field which is sent by a reader continues to pulse the interrogation field after detection of a collision at the reader.

9. The system of claim 6 wherein the interrogation field is pulsed periodically.