LOW POWER RADIO FREQUENCY COMMUNICATION

• US 20130265140A1
• Filed: 08/29/2012
• Published: 10/10/2013
• Est. Priority Date: 04/05/2012
• Status: Active Grant

• Current Assignee: Duke University, Ricoh Company Limited
• Original Assignee: Ricoh Company Limited
• Inventors: Gudan, Ken, Chemishkian, Sergey, Hull, Jonathan J., Reynolds, Matthew S.
• Granted Patent: US 9,245,158 B2
• Time in Patent Office: Days
• US Class Current: 340/10.3
• CPC Class Codes: G06K 19/071 the source being a field other than an interrogation field, e.g. WLAN, cellular phone network
• 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 7/10158 methods and means used by the interrogation device for reliably powering the wireless record carriers using an electromagnetic interrogation field
• CPC Class Codes: G06K 7/10207 parameter settings related to power consumption of the interrogator
• CPC Class Codes: H04W 52/0229 where the received signal is a wanted signal
• CPC Class Codes: H04W 52/0245 according to signal strength
• CPC Class Codes: H04W 52/0274 by switching on or off the equipment or parts thereof
• CPC Class Codes: H04W 88/10 adapted for operation in multiple networks, e.g. multi-mode access points
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A method, system and tag for low power radio frequency communication are described. In one embodiment, the RF tag comprises: a radio, an energy harvesting unit operable to convert incident RF energy to direct current (DC), a storage unit to store recovered DC power, one or more sensors for sensing and logging data, and a microcontroller coupled to the energy harvesting and storage units, the one or more sensors and the radio, the microcontroller operable to wake up from a sleep state and cause the radio to communicate, sensed data from at least one of the one or more sensors while powered by energy previously harvested and stored by the energy harvesting and storage unit.

Claims

1. An RF tag for use in a sensor network, the tag comprising:

a radio;

an energy harvesting unit operable to convert incident RF energy to direct current (DC);

a storage unit operable to store recovered DC power;

one or more sensors for sensing and logging data;

a microcontroller coupled to the energy harvesting and storage units, the one or more sensors and the radio, the microcontroller operable to wake up from a sleep state and cause the radio to communicate sensed data from at least one of the one or more sensors while powered by energy previously harvested and stored by the energy harvesting and storage unit.

2. The tag defined in claim 1 wherein the microcontroller is operable to wait in a sleep state until receiving an interrupt that is in response to an RF command sequence, a sensed event, or a user stimulus.

3. The tag defined in claim 2 wherein the RF command sequence comprises a modulated pattern, a specific time domain energy signature, or a specific frequency domain energy signature.

4. The tag defined in claim 1 wherein the microcontroller causes the radio to communicate sensed data in response to the interrupt.

5. The tag defined in claim 1 further comprising:

an antenna; and

a switch coupled to interface the antenna with the radio and the RF energy harvesting and storage unit.

6. The tag defined in claim 1 wherein the microcontroller is operable to wake up when receiving an interrupt, and in response, causes:

data to be sensed by the at least one sensor;

uploading the sensed data to the network; and

waiting to receive an acknowledgement that the sensed data was received.

7. A Wi-Fi communication system comprising:

an access point coupled to provide access to a network;

an RF tag to communicate wirelessly with the access point, the tag comprising

a radio;

an energy harvesting unit operable to convert incident RF energy to direct current (DC);

a storage unit operable to store recovered DC power;

one or more sensors for sensing and logging data; and

a microcontroller coupled to the energy harvesting and storage unit, the one or more sensors and the radio, the microcontroller operable to wake up from a sleep state and cause the radio to communicate with the access point via Wi-Fi to send sensed data to the network from at least one of the one or more sensors while powered by energy previously harvested and stored by the energy harvesting and storage unit.

8. The communication system defined in claim 7 further comprising an interrupt input device coupled to provide an interrupt to the microcontroller.

9. The communication system defined in claim 8 wherein the interrupt input device is associated with a sensor, a timer, or other interrupt-generating source.

10. The communication system defined in claim 8 wherein the microcontroller causes the radio to communicate sensed data in response to the interrupt.

11. The communication system defined in claim 7 wherein the RF tag communicates using as a radio protocol a Wi-Fi standard interface so that it is compatible with existing Wi-Fi systems.

12. The communication system defined in claim 7 further comprising:

an antenna; and

a switch coupled to the antenna with the radio and the RF energy harvesting and storage unit.

13. The communication system defined by claim 12 further comprising an impedance matching circuit coupling the antenna and the switch.

14. The communication system defined in claim 7 wherein the one or more sensors includes one or more of a temperature sensor, a pressure sensor, a humidity sensor, a gas composition sensor, an image sensor, and a position sensor.

15. The communication system defined in claim 7 wherein the microcontroller waits in a sleep state until receiving an interrupt, and in response, causes:

data to be sensed by the at least one sensor;

upload the sensed data to the network; and

wait to receive an acknowledgement that the sensed data was received.

16. The communication system defined in claim 7, wherein the microprocessor logs an error code if timeout occurs while waiting for the acknowledgement, the microprocessor causing the error code to be reported when the tag next wakes up.

17. The communication system defined in claim 7 wherein the microcontroller transitions into a sleep state in response to receiving the acknowledgement.

18. The communication system defined in claim 7 wherein the microcontroller wakes up from a sleep state in response to at least one of a sense interrupt, a timer interrupt, a wake-on-change, or being polled and in response to the sense interrupt causes the at least one sensor to sense and store data, the microcontroller returning to the sleep state without communicating the sensed data at that time.

19. The communication system defined in claim 7 further comprising one or more other RF devices to provide RF energy that is harvested by the harvesting and storage unit of the tag.

20. An RF tag for use in a sensor network, the tag comprising:

a radio;

an energy harvesting unit operable to convert incident RF energy to direct current (DC);

a storage unit operable to store recovered DC power;

one or more sensors for sensing and logging data; and

a microcontroller coupled to the energy harvesting and storage units, the one or more sensors and the radio, the microcontroller operable to wake up from a sleep state and cause the radio to communicate sensed data from at least one of the one or more sensors while powered by energy previously harvested and stored by the energy harvesting and storage unit, and

wherein the microcontroller, responsive to an acknowledgement received via the radio, is operable to re-configure the RF tag based on command information in the acknowledgement.