Wireless flywheel synchronization method

• US 5,748,137 A
• Filed: 05/08/1996
• Issued: 05/05/1998
• Est. Priority Date: 05/08/1996
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: d'Hont, Loek
• Primary Examiner(s): Sotomayor, John B.
• Application Number:
  US08/646,881
• Time in Patent Office: 727 Days
• Field of Search: 342/42, 342/44, 342/50, 342/51, 342/31, 342/40, 342/46, 340/825.34, 340/825.54
• US Class Current: 342/42
• CPC Class Codes: G01S 13/76 wherein pulse-type signals are transmitted
• 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 7/10346 the antenna being of the far field type, e.g. HF types or dipoles

Abstract

The invention is an improved method and apparatus for synchronizing wireless communications utilizing a master source (10) for a transmitting a synchronizing pulse to multiple reader modules (20 and 28) each of which has an internal crystal oscillator (22 and 30). The synchronizing pulse periodically resets the interrogation cycle, the power burst and receive cycle, for all of the reader modules (20 and 28). Between pulses, the internal crystal oscillator (22 and 30) is used to run interrogation cycles, and thus functions as a "flywheel" to absorb fluctuations in the synchronizing pulse such as when a particular synchronizing pulse is missed.

Claims

1. A wireless flywheel for synchronizing signal transmissions, comprising:

a master source for periodically transmuting synchronization pulses;

a first reader module having a quartz crystal and a receiver, said first module having a fixed interrogation cycle;

second reader module having a quartz crystal and a receiver, said second module having a different fixed interrogation cycle than said first module; and

wherein said interrogation cycle of said first reader and said interrogation cycle of said second reader is reset upon receipt of a synchronization pulse from said master source resulting in said first reader transmitting interrogation pulses at times other than when the second reader is transmitting interrogation pulses.

2. A wireless flywheel fro synchronizing signal transmissions according to claim 1, further comprising:

a continuous wave generator connected to said master source for transmitting short bursts of continuous wave pulses.

3. A wireless flywheel for synchronizing signal transmissions according to claim 2, wherein said receiver of said first reader module further comprises a continuous wave receiver;

and

wherein said receiver of said second reader module further comprises a continuous wave receiver.

4. A wireless flywheel for synchronizing signal transmissions according to claim 1, wherein said receiver of said first reader module further comprises a DTMF encoder-decoder;

wherein said receiver of said second reader module further comprises a DTMF encoder-decoder; and

wherein said master source transmits synchronizing pulses using DTMF coded tones.

5. A wireless flywheel for synchronizing signal transmissions according to claim 1, wherein said receiver of said first reader module further comprises a digital encoder/decoder;

wherein said receiver of said second reader module further comprises a digital encoder-decoder; and

wherein said master source transmits synchronizing pulses using digitally encoded pulses.

6. A wireless flywheel for synchronizing signal transmissions according to claim 1, wherein said receiver comprises an AM receiver having a low frequency filter sensitive only to said synchronizing pulse.

7. A wireless flywheel method for synchronizing signal transmissions, comprising the steps of:

setting a plurality of fixed time intervals for an interrogation cycle for each of a plurality of reader modules relative to a crystal oscillator internal to said reader module;

transmitting a synchronizing pulse to a plurality of reader modules; and

restarting the interrogation cycle upon detection of the synchronization pulse, thereby resulting in each of said plurality of reader modules transmitting interrogation pulses at different times from each other.

8. A wireless flywheel method for synchronizing signal transmissions according to 7, wherein the step of setting said plurality of reader modules with a fixed time interval for length of power-burst includes setting said fixed time interval to no less than 50 msec.

9. A wireless flywheel method for synchronizing signal transmissions according to claim 7, wherein the step of transmitting a synchronizing pulse to a plurality of reader modules with a fixed time interval for length of receive includes setting said fixed time interval to no less than 50 msec.

10. A wireless flywheel method for synchronizing signal transmissions according to claim 7, wherein the step of transmitting a synchronizing pulse to a plurality of reader modules is repeated at least every 26 seconds.

11. A wireless flywheel method for synchronizing signal transmissions according to claim 10, wherein the step of transmitting a synchronizing pulse to a plurality of reader modules is repeated at least within a range of 5 and 10 seconds.

12. A wireless flywheel method for synchronizing signal transmissions according to claim 7, wherein the step of transmitting a synchronizing pulse to a plurality of reader modules occurs at a frequency other than the operating frequency of said first reader module and said second reader module.

13. A wireless flywheel method for synchronizing signal transmissions according to claim 7, wherein the step of transmitting a synchronizing pulse to a plurality of reader modules occurs at a frequency which is selected from the group consisting of:

approximately 13 MHz, approximately 27 MHz and approximately 40 MHz.

14. A wireless flywheel method for synchronizing signal transmissions according to claim 7, wherein said synchronizing pulse is a CW pulse.