Use of a subcarrier in an organic semiconductor radio frequency identification system

• US 7,068,169 B2
• Filed: 06/05/2003
• Issued: 06/27/2006
• Est. Priority Date: 06/05/2003
• Status: Expired due to Fees

• Current Assignee: Motorola Solutions, Inc.
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Rakers, Patrick L., Collins, Timothy J.
• Primary Examiner(s): Lee, Benjamin C.
• Assistant Examiner(s): TANG, SON M
• Application Number:
  US10/455,208
• Publication Number:
  US 20040246134A1
• Time in Patent Office: 1,118 Days
• Field of Search: 340/572.4, 340/10.1
• US Class Current: 340/572.1
• 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: H04L 27/38 Demodulator circuits; Receiver circuits

Abstract

A radio frequency identification system comprising a radio reader circuit operable to emit a radio frequency carrier signal modulated with a subcarrier, which has a subcarrier modulation rate. The radio frequency identification tag circuit is operable to extract the subcarrier from the emitted radio frequency carrier signal and the extracted subcarrier then functions as a clock, which operates to assist in the transfer of a modulated backscattered signal to the radio frequency identification reader circuit. The radio frequency identification reader circuit decodes the modulated backscattered signal and the data encoded in the radio frequency identification tag circuit is obtained.

Claims

1. A radio frequency identification system comprising:

a radio frequency identification reader circuit operable to emit a radio frequency carrier signal modulated with a subcarrier having a subcarrier modulation rate; and

a radio frequency identification tag circuit comprising a field effect transistor formed from an organic semiconductor material that extracts the subcarrier from the emitted radio frequency carrier signal, wherein the subcarrier modulation rate is equal to or less than the switching rate of the field effect transistor and the extracted subcarrier functions as a clock operable to assist in the transfer of a modulated backscattered signal to the radio frequency identification reader circuit and wherein the modulated backscattered signal is decoded by the radio frequency identification reader circuit to obtain data encoded in the radio frequency identification tag circuit.

2. The system of claim 1, wherein the radio frequency carrier signal is amplitude modulated to impress the subcarrier upon the radio frequency carrier signal.

3. The system of claim 1, wherein the radio frequency carrier signal is phase modulated to impress the subcarrier upon the radio frequency carrier signal.

4. The system of claim 1, wherein the radio frequency carrier signal is frequency modulated to impress the subcarrier upon the radio frequency carrier signal.

5. The system of claim 1, wherein the modulated backscattered signal is transferred to the radio frequency identification reader circuit from the radio frequency identification tag circuit by inductive coupling.

6. The system of claim 1, wherein the modulated backscattered signal is transferred to the radio frequency identification reader circuit from the radio frequency identification tag circuit by capacitive coupling.

7. A method of operating a radio frequency identification system, comprising:

emitting from a radio frequency identification reader a radio frequency carrier signal modulated by a subcarrier having a subcarrier modulation rate;

extracting the subcarrier from the emitted radio frequency carrier signal by a first portion of a radio frequency identification tag circuit comprising a field effect transistor formed from an organic semiconductor material to obtain a clock signal, wherein the subcarrier modulation rate is equal to or less than the switching rate of the field effect transistor;

extracting data stored on a second portion of the radio frequency identification tag circuit by synchronizing the clock signal to the stored data; and

transmitting the extracted data to the radio frequency identification reader from the radio frequency identification tag circuit on a modulated backscattered signal.

8. The method of claim 7, further comprising:

sending the modulated backscattered signal to the radio frequency identification reader from the radio frequency identification tag circuit by capacitive coupling of the backscattered modulation signal.

9. The method of claim 8, further comprising:

sharing a capacitive coupling portion of the radio frequency identification tag circuit between the first portion of the radio frequency identification tag circuit and the second portion of the radio frequency identification tag circuit.

10. The method of claim 7, further comprising:

sending the modulated backscattered signal to the radio frequency identification reader from the radio frequency identification tag circuit by inductive coupling of the modulated backscattered signal.

11. The method of claim 10, further comprising:

sharing an inductive coupling portion of the radio frequency identification tag circuit between a first portion of the radio frequency identification tag circuit and the second portion of the radio frequency identification tag circuit.

12. The method of claim 7, further comprising:

using the clock signal to set a timing for the modulated backscattered signal to transit the extracted data to the radio frequency identification reader.

13. A radio frequency identification system, comprising:

means for emitting a subcarrier modulated radio frequency carrier signal from a radio frequency identification reader circuit, the subcarrier having a subcarrier modulation rate;

means for extracting the subcarrier from the emitted radio frequency carrier signal at a radio frequency identification tag circuit comprising a field effect transistor formed from an organic semiconductor material to obtain a clock signal, wherein the subcarrier modulation rate is equal to or less than the switching rate of the field effect transistor;

means for extracting data stored in the radio frequency identification tag circuit by synchronizing the clock signal to the stored data; and

means for transmitting the extracted data to the radio frequency identification reader from the radio frequency identification tag circuit.

14. A radio frequency identification tag, comprising:

a first circuit comprising a field effect transistor formed from an organic semiconductor material operable to receive a subcarrier modulated radio frequency carrier signal the subcarrier having a subcarrier modulation rate equal to or less than the switching rate of the field effect transistor, wherein the first circuit is operable to extract the subcarrier from the received subcarrier modulated radio frequency carrier signal emitted from a radio frequency identification reader, and wherein the extracted subcarrier is a clock signal; and

a second circuit operable to utilize the clock signal to extract data stored on the radio frequency identification tag by synchronizing the clock signal to the stored data, wherein the first circuit and the second circuit are in electrical communication.

15. The tag of claim 14, wherein the second circuit comprises an organic semiconductor material.

16. The tag of claim 14, wherein the clock signal has a clock rate that is equal to the subcarrier modulation rate.

17. The tag of claim 14, wherein the second circuit uses the clock signal to set a timing for a modulated backscattered signal, wherein the modulated backscattered signal transmits the extracted data.

18. A radio frequency identification tag circuit, comprising:

means for receiving a subcarrier modulated radio frequency carrier signal emitted from a radio frequency identification reader, the subcarrier having a subcarrier modulation rate;

means comprising a field effect transistor formed from an organic semiconductor material for extracting the subcarrier from the received subcarrier modulated radio frequency carrier signal to obtain a clock signal, wherein the subcarrier modulation rate is equal to or less than the switching rate of the field effect transistor;

means for extracting data stored in the radio frequency identification tag circuit by synchronizing the clock signal to the stored data; and

means for transmitting the extracted data to the radio frequency identification reader from the radio frequency identification tag circuit.