Passive RF Energy Harvesting Scheme For Wireless Sensor

• US 20120256492A1
• Filed: 03/27/2007
• Published: 10/11/2012
• Est. Priority Date: 03/31/2006
• Status: Active Grant

• Current Assignee: Ollnova Technologies Limited (Atlantic IP Services Limited)
• Original Assignee: Siemens Corporate Research Incorporated (Siemens AG)
• Inventors: Song, Zhen, Sastry, Chellury R.
• Granted Patent: US 8,552,597 B2
• Time in Patent Office: Days
• US Class Current: 307/66
• CPC Class Codes: H02J 1/102 being switching converters H02J1/108, H02J1/12 take precedence
• CPC Class Codes: H02J 50/001 Energy harvesting or scavenging
• CPC Class Codes: H02J 50/27 characterised by the type of receiving antennas, e.g. rectennas
• CPC Class Codes: H02J 50/50 using additional energy repeaters between transmitting devices and receiving devices

Abstract

A radio frequency energy harvester harvests RF energy from the environment. The energy harvester may include a local power source. The energy harvester may have an associated crystal radio antenna that harvests AM radio waves ubiquitously. The radio frequency energy harvested may be stored via a super capacitor. The stored energy may power a self-contained processing unit directly when the level of the energy harvested remains above a threshold level. However, if the energy harvested drops below the threshold level, the processing unit, which may include a radio, may switch to the local power source and/or a low power mode of operation. The low power mode of operation may reduce the amount of processing and/or transmitting by the radio. The processing unit may be part of a network of radios. The energy harvester may supply energy for a variety of applications, including building automation, industrial automation, power generation, and healthcare.

Claims

1. A method of passive radio frequency energy harvesting, the method comprising:

harvesting radio frequency energy using a crystal receiver;

powering a processing unit only, from the radio frequency energy being harvested when the radio frequency energy being harvested or an associated signal is above a threshold level;

generating an interrupt signal to switch the processing unit to a low power mode when the radio frequency energy being harvested falls below the threshold level; and

alternatively powering the processing unit only from an on-board power source when the radio frequency energy being harvested or the associated signal is below the threshold level.

2. The method of claim 1, wherein the crystal receiver employs an antenna that is fabricated from printed circuit board.

3. The method of claim 1, wherein the radio frequency energy harvested or the associated signal is increased by a super capacitor before being used to power the processing unit.

4. The method of claim 1, wherein the on-board power source is a battery or a capacitor.

5. The method of claim 1, wherein the crystal receiver employs a ferrite coil antenna.

6. The method of claim 1, wherein the radio frequency energy is harvested ubiquitously.

7. A method of passive radio frequency energy harvesting, the method comprising:

harvesting radio frequency energy using a crystal receiver;

powering a processing unit only from the radio frequency energy being harvested when the radio frequency energy being harvested or an associated signal is above a threshold level, wherein the processor unit is a self-contained sensor node operable to direct the operation of building equipment to control an environment of a building;

generating an interrupt signal to switch the processing unit to a low power mode when the radio frequency energy being harvested falls below the threshold level; and

alternatively powering the processing unit only from an on-board power source when the radio frequency energy being harvested or the associated signal is below the threshold level.

25. The method of claim 7, wherein the processor unit has power requirements of greater than 10 milliwatts.

8. A method of passive radio frequency energy harvesting, the method comprising:

harvesting radio frequency energy via a crystal receiver; and

storing the radio frequency energy harvested on a super capacitor for subsequent use.

9. The method of claim 8, the method comprising using the radio frequency energy harvested to power a self-contained processing unit.

10. The method of claim 9, the method comprising switching to an on-board power supply if the signal associated with the radio frequency energy harvested falls below a threshold level.

11. The method of claim 9, wherein the self-contained processing unit is implanted internally to a patient and senses a biological characteristic.

12. The method of claim 9, wherein the self-contained processing unit includes a sensor operable to sense an environmental condition and a wireless transmitter operable to transmit a control signal.

13. The method of claim 8, wherein the crystal receiver is fabricated from printed circuit board.

14. A system for passive radio frequency energy harvesting, the system comprising:

a network of radios within a building operable to direct the operation of building equipment to control a building environment of a building; and

at least one radio within the network being a sensor node operable to harvest radio frequency energy via a crystal receiver, the radio frequency energy harvested being used to power the sensor node.

15. The system of claim 14, wherein the crystal receiver is fabricated from printed circuit board.

16. The system of claim 14, wherein the sensor node includes a processor, a sensor, and a wireless radio.

17. The system of claim 14, wherein the sensor node increases a signal associated with the radio frequency energy being harvested via a super capacitor.

18. The system of claim 14, wherein the sensor node monitors a signal associated with the radio frequency energy being harvested and switches operating modes to conserve energy when the signal falls below a threshold level.

19. The system of claim 14, wherein the sensor node is operable to control a piece of building environmental equipment.

20. A computer-readable medium having instructions executable on a computer stored thereon, the instructions comprising:

monitoring for an interrupt signal associated with radio frequency energy harvested being harvested via a crystal receiver, the radio frequency energy being used to at least partially power a sensor node; and

automatically reducing the amount of power being expended by the sensor node if the interrupt signal is detected.

21. The computer-readable medium of claim 20, the instructions comprising

directing heating, cooling, or lighting equipment to automatically alter the building environment of an area of a building.

22. The computer-readable medium of claim 21, the instructions comprising directing pumps, fans, valves, and dampers.

23. The computer-readable medium of claim 20, wherein reducing the amount of power being expended by the sensor node includes reducing the amount of processing performed by a processor associated with the sensor node.

24. The computer-readable medium of claim 20, wherein reducing the amount of power being expended by the sensor node includes reducing the amount of time a radio associated with the sensor node transmits.