RF POWER EXTRACTING CIRCUIT AND RELATED TECHNIQUES

• US 20070087719A1
• Filed: 12/11/2006
• Published: 04/19/2007
• Est. Priority Date: 09/17/2004
• Status: Active Grant

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Mandal, Soumyajit, Sarpeshkar, Rahul
• Granted Patent: US 8,045,947 B2
• Time in Patent Office: Days
• US Class Current: 455/299
• CPC Class Codes: H01Q 1/22 by structural association with other equipment or articles
• CPC Class Codes: H01Q 1/2225 used in active tags, i.e. provided with its own power source or in passive tags, i.e. deriving power from RF signal
• CPC Class Codes: H01Q 1/248 provided with an AC/DC converting device, e.g. rectennas
• CPC Class Codes: H01Q 23/00 Antennas with active circuits or circuit elements integrated within them or attached to them
• CPC Class Codes: H01Q 7/00 Loop antennas with a substantially uniform current distribution around the loop and having a directional radiation pattern in a plane perpendicular to the plane of the loop
• CPC Class Codes: H01Q 9/28 Conical, cylindrical, cage, strip, gauze, or like elements having an extended radiating surface; Elements comprising two conical surfaces having collinear axes and adjacent apices and fed by two-conductor transmission lines waveguide horns or mouths H01Q13/00; slot antennas H01Q13/00

Abstract

In one aspect, the invention is a far-field power extraction circuit which includes an integrated antenna and impedance matching portion and a rectifier portion. The antenna and impedance matching portion includes an antenna configured to be responsive to a propagating electromagnetic signal and which provides a resonant response at a resonant frequency. In response to the electromagnetic signal, the antenna provides an electromagnetic output signal at an antenna port. The antenna and impedance matching portion is configured to match an antenna impedance with a remainder of the far-field power extraction circuit including the rectifier portion of the power extraction circuit coupled to the antenna and impedance matching portion. The rectifier is configured to rectify the electromagnetic output signal provided by the antenna to produce a direct current (DC) voltage at an output of the rectifier.

Claims

1. A far-field power extraction circuit comprising:

an antenna configured to receive an electromagnetic signal having a resonant frequency and to match an antenna input impedance with a remainder of the far-field power extraction circuit; and

a rectifier coupled to the antenna, the rectifier being configured to rectify an electromagnetic signal provided thereto by the antenna to produce a direct current (DC) voltage at a rectifier output.

2. The circuit of claim 1 wherein the antenna comprises two resonant loops each coupled to an inductive loop by a corresponding one of a plurality of impedance inverters, each resonant loop having a perimeter of length substantially equal to one-half wavelength at the resonant frequency.

3. The circuit of claim 1 wherein the rectifier comprises at least one circuit element having a nonlinear capacitive characteristic.

4. The circuit of claim 3 wherein the at least one circuit element is a nonlinear capacitor.

5. The circuit of claim 1, further comprising a feedback tuning network coupled between the antenna and a terminal of the rectifier at which a voltage is generated.

6. The circuit of claim 5 wherein the feedback tuning network is coupled between an output terminal of the rectifier and the antenna.

7. The circuit of claim 1 wherein the antenna is provided having a size and shape such that it is resonant at a frequency of about 900 MHz.

8. A far-field power extraction circuit comprising:

an antenna configured to receive an electromagnetic signal; and

a multi-stage rectifier coupled to the antenna, the multi-stage rectifier being configured to rectify an electromagnetic signal provided thereto by the antenna to produce a direct current (DC) voltage at a rectifier output, the multi-stage rectifier comprising N stages, where N>

1,

wherein the multi-stage rectifier comprises at least one circuit element having a nonlinear capacitive characteristic.

9. The circuit of claim 8 wherein a first rectifier stage of the N rectifier stages includes four transistors.

10. The circuit of claim 9 wherein the four transistors comprise two p-type metal-oxide-semiconductor (PMOS) transistors.

11. The circuit of claim 9 wherein the four transistors comprise two n-type metal-oxide-semiconductor (NMOS) transistors.

12. The circuit of claim 9 wherein the four transistors comprises a floating gate transistor.

13. The circuit of claim 8 wherein the at least one circuit element is a nonlinear capacitor.

14. The circuit of claim 8 wherein the antenna is responsive to radio frequency signals having a frequency of about 900 MHz.

15. A far-field power extraction circuit comprising:

an antenna configured to receive an electromagnetic signal, said antenna having a resonant frequency and configured to subsequently match an antenna impedance with a remainder of the far-field power extraction circuit at the resonant frequency; and

a multi-stage rectifier coupled to the antenna, the multi-stage rectifier adapted to receive an electromagnetic signal from the antenna and in response thereto, to produce a direct current (DC) voltage at a rectifier output, the multi-stage rectifier comprising N stages, where N>

1,

wherein the multi-stage rectifier comprises at least one circuit element having a nonlinear capacitance characteristic.

16. The circuit of claim 15 wherein the antenna includes two loops each coupled to an inductive loop by a corresponding one of a plurality of impedance inverters, each loop having a perimeter substantially equal to one-half wavelength at the resonant frequency.

17. The circuit of claim 15 wherein a first rectifier stage of the N rectifier stages includes four transistors.

18. The circuit of claim 17 wherein the four transistors comprise two p-type metal-oxide-semiconductor (PMOS) transistors.

19. The circuit of claim 18 wherein the four transistors comprise two n-type metal-oxide-semiconductor (NMOS) transistors.

20. The circuit of claim 17 wherein the four transistors comprises a floating gate transistor.

21. The circuit of claim 15 wherein the antenna is provided having a size and shape such that it is resonant at a frequency of about 900 MHz.

22. The circuit of claim 15, further comprising a feedback tuning network coupled between the antenna and a terminal of the rectifier at which a voltage is generated.