Power harvesting in a passive RFID device
A method of harvesting power in a passive RFID device including a passive biometric authentication engine, including the steps of receiving a command from a powered RFID reader and supplying power extracted from an excitation field of the RFID reader to the biometric authentication engine whilst the RFID reader waits for a response to the command. Responsive to determining that a period that the RFID device has been waiting for a response exceeds a predetermined threshold, and that a process being performed by the biometric authentication engine has not been completed, a request for a wait time extension is sent to the RFID reader to cause it to continue supplying the excitation field.
1. A method for harvesting power in a passive RFID device comprising a passive biometric authentication engine, the method comprising:
receiving, by the RFID device, a command from a powered RFID reader;
receiving, by the RFID device, a non-pulsing continuous radio-frequency excitation field whilst the RFID reader waits for a response to the command;
harvesting, by the RFID device, power from the excitation field;
supplying the power extracted from the excitation field to the biometric authentication engine;
performing a process in the biometric authentication engine, the process being one not required for responding to the command from the RFID reader;
determining a period that the RFID device has been waiting for a response; and
responsive to determining that the period exceeds a predetermined threshold, if the process has not been completed, sending, by the RFID device, a request for a wait time extension to the RFID reader.
2. A method according to claim 1 , wherein the RFID device does not respond to the command whilst the biometric authentication engine is performing the process.
3. A method according to claim 1 , further comprising:
after the biometric authentication engine completes the process, responding by the RFID device to the command.
4. A method according to claim 1 , wherein the steps of determining a period and sending a request for a wait time extension to the RFID reader are repeated until the process is completed and/or a response to the command has been sent.
5. A method according to claim 1 , wherein the period is a time since the command was received or since the last wait time extension request was made.
6. A method according to claim 1 , wherein the process performed by the biometric authentication engine is a biometric enrolment process.
7. A method according to claim 1 , wherein the process performed by the biometric authentication engine is a biometric matching process.
8. A method according to claim 1 , wherein the process requires greater than 5.0 seconds to be completed.
9. A method according to claim 1 , wherein the biometric authentication engine includes a biometric scanner and a processing unit.
10. A method according to claim 9 , wherein the biometric authentication engine is a fingerprint authentication engine and the biometric scanner is a fingerprint scanner.
11. A method according to claim 1 , wherein the RFID device is a proximity integrated circuit card (PICC) and the RFID reader is a proximity coupling device (PCD).
12. A method according to claim 11 , wherein the predetermined threshold is less than a first wait time (FWT) of the PCD.
13. A passive RFID device comprising:
an antenna for receiving a radio-frequency excitation field from an RFID reader and for harvesting power from the excitation field;
a passive biometric authentication engine arranged to receive power harvested by the antenna; and
an RFID device controller arranged to perform a method, comprising:
receiving, by the antenna, a command from a powered RFID reader;
receiving, by the antenna, a substantially continuous radio-frequency excitation field whilst the RFID reader waits for a response to the command;
performing a process in the biometric authentication engine, the process being one not required for responding to the command from the RFID reader;
determining a period that the RFID device has been waiting for a response; and
responsive to determining that the period exceeds a predetermined threshold if the process has not been completed, sending by the antenna a request for a wait time extension to the RFID reader.
14. A passive RFID device according to claim 13 , wherein the RFID controller is configured not to respond to the command whilst the biometric authentication engine is performing a process.
15. A passive RFID device according to claim 13 , wherein the method further comprises:
after the biometric authentication engine completes the process, responding by the RFID device to the command.
16. A passive RFID device according to claim 13 , wherein the steps of determining a period and sending a request for a wait time extension to the RFID reader are repeated until the process is completed and/or a response to the command has been sent.
17. A passive RFID device according to claim 13 , wherein the period is a time since the command was received or since the last wait time extension request was made.
18. A passive RFID device according to claim 13 , wherein the process performed by the biometric authentication engine is a biometric enrolment process.
19. A passive RFID device according to claim 13 , wherein the process performed by the biometric authentication engine is a biometric matching process.
20. A passive RFID device according to claim 13 , wherein the process requires greater than 5.0 seconds to be completed.
21. A passive RFID device according to claim 13 , wherein the biometric authentication engine includes a biometric scanner and a processing unit.
22. A passive RFID device according to claim 21 , wherein the biometric authentication engine is a fingerprint authentication engine and the biometric scanner is a fingerprint scanner.
23. A passive RFID device according to claim 13 , wherein the passive RFID device is a proximity integrated circuit card (PICC) and the RFID reader is a proximity coupling device (PCD).
24. A passive RFID device according to claim 23 , wherein the predetermined threshold is set to be less than a first wait time (FWT) of the PCD.