Method and apparatus for transfering information from a transponder

• US 5,841,364 A
• Filed: 03/13/1997
• Issued: 11/24/1998
• Est. Priority Date: 10/07/1994
• Status: Expired due to Fees

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Hagl, Andreas, Schuermann, Josef H.
• Primary Examiner(s): Zimmerman, Brian
• Assistant Examiner(s): WILSON JR, WILLIAM HALL
• Application Number:
  US08/816,928
• Time in Patent Office: 621 Days
• Field of Search: 340/825.34, 340/825.54, 340/825.58, 340/825.69, 340/825.71-825.75, 340/572, 331/10, 331/34, 342/42, 342/44, 342/51, 375/303, 375/272, 375/364, 375/278
• US Class Current: 340/10.4
• CPC Class Codes: G06K 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs
• 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

Abstract

A transponder unit (10) includes an N cycle counter (30) and an M cycle counter (28). The N cycle counter (30) has a different cycle value than the M cycle counter (28). During the transmission of information from the transponder unit (10), the duration for data bits having a binary zero value is controlled by the N cycle counter (30). The duration of data bits having a binary one value is controlled by the M cycle counter (28). The use of different cycle values within the N cycle counter (30) and the M cycle counter (28) allows for the transmission of binary one and binary zero data bits having the same bit length despite different frequencies representing the binary one and binary zero bits respectively.

Claims

1. A method of transferring information from a transponder, comprising the steps of;

selecting a first frequency representing data bits of information having a binary zero value;

selecting a second frequency representing data bits of information having a binary one value;

generating a transponder resonant frequency signal having one of the first and second frequencies;

changing a frequency of the transponder resonant frequency signal between the first and second frequencies in response to the data bits of the information in order to transmit the information, the data bits of information having a binary zero value being of a same bit length as the data bits of information having a binary one value;

counting a first number of cycles of the first frequency; and

counting a second number of cycles of the second frequency, the first number of cycles being different than the second number of cycles to achieve the same bit length, each counting step controlling the changing of the transponder resonant frequency signal according to each data bit of information to be transmitted.

2. The method of claim 1, further comprising the step of:

resetting each counting step for each data bit of information transmitted.

3. The method of claim 1, wherein the first number of cycles is greater than the second number of cycles.

4. The method of claim 3, wherein the first number of cycles is twelve and the second number of cycles is eleven.

5. The method of claim 3, wherein the first frequency is 134.2 kHz and the second frequency is 123.0 kHz.

6. A transponder for transferring information, comprising:

a resonant circuit operable to generate a transponder resonant frequency signal, said transmit frequency signal having one of a first frequency and a second frequency, said first frequency representing data bits of information having a binary zero value, said second frequency representing data bits of information having a binary one value;

a control circuit operable to select one of said first and second frequencies for said transponder resonant frequency signal associated with each data bit of information, said control circuit transmitting each data bit of information with a same bit length regardless of which of said first and second frequencies is selected for said transponder resonant frequency signal;

wherein said control circuit includes a first counter circuit associated with said first frequency and a second counter circuit associated with said second frequency, said first counter circuit operable to count down from a first value, said second counter circuit operable to count down from a second value, said first value being different than said second value to achieve said same bit length.

7. The transponder of claim 6, wherein said first and second counter circuits count a number of cycles of said transponder resonant frequency signal according to said first and second values respectively.

8. The transponder of claim 6, wherein said first and second counters are reset for each data bit of information transmitted by said resonant circuit.

9. The transponder of claim 6, wherein said first value is one more than said second value.

10. The transponder of claim 9, wherein said first value is twelve, and said second value is eleven.

11. The transponder of claim 6, wherein said first frequency is 134.2 kHz and said second frequency is 123.0 kHz.

12. A transponder for transmitting information comprising:

a resonant circuit operable to generate a transponder resonant frequency signal said transponder resonant frequency signal having one of a first frequency and a second frequency, said first frequency representing data bits of information having a binary zero value, said second frequency representing data bits of information having a binary one value;

a switch circuit operable to change said transmit frequency of said resonant circuit between said first and second frequencies;

a first counter circuit operable to count a first number of cycles of said transponder resonant frequency signal, said first counter circuit associated with said first frequency;

a second counter circuit operable to count a second number of cycles of said transponder resonant frequency signal, said second counter circuit associated with said second frequency;

a memory circuit operable to store said data bits of information, said memory circuit operable to sequentially transfer each data bit of information in response to one of said first and second counter circuits in order to control said switch circuit, said first and second counter circuits ensuring that each data bit of information is transmitted by said resonant circuit with a same bit length regardless of which of said first and second frequencies is selected for said transponder resonant frequency signal.

13. The transponder of claim 12, further comprising:

reset circuitry operable to initialize said memory circuit, said first counter circuit, and said second counter circuit, said reset circuit operable to reset said first and second counter circuits for each data bit of information to be transmitted by said resonant circuit.

14. The transponder of claim 12, wherein each data bit of information determines which one of said first and second counter circuits controls said switch circuit.

15. The transponder of claim 14, further comprising:

a second switch circuit operable to select one of said first and second counter circuits in response to each data bit of information in order to control sequential transfer of each data bit of information by said memory circuit.