Systems, methods, and apparatus for detection of metal objects in a predetermined space

Patent metadata

Field	Value
Publication number	US-9726518-B2
Application number	US-201313791585-A
Country	US
Kind code	B2
Filing date	Mar 8, 2013
Priority date	Jul 13, 2012
Publication date	Aug 8, 2017
Grant date	Aug 8, 2017

Abstract

This disclosure provides systems, methods and apparatus for detecting foreign objects. In one aspect an apparatus for detecting a presence of an object is provided. The apparatus includes a resonant circuit having a resonant frequency. The resonant circuit includes a sense circuit including an electrically conductive structure. The apparatus further includes a coupling circuit coupled to the sense circuit. The apparatus further includes a detection circuit coupled to the sense circuit via the coupling circuit. The detection circuit is configured to detect the presence of the object in response to detecting a difference between a measured characteristic that depends on a frequency at which the resonant circuit is resonating and a corresponding characteristic that depends on the resonant frequency of the resonant circuit. The coupling circuit is configured to reduce a variation of the resonant frequency by the detection circuit in the absence of the object.

First claim

What is claimed is:

1. An apparatus for detecting a presence of an object, the apparatus comprising:
a plurality of resonant sense circuits, each having a resonant frequency, each resonant sense circuit comprising an electrically conductive structure and a coupling circuit configured to determine resonance and an amount of coupling, the electrically conductive structure comprising a loop positioned within a multidimensional loop array;
a multiplexer coupled to the plurality of resonant sense circuits;
at least one capacitor coupled between the plurality of resonant sense circuits and the multiplexer; and
a detection circuit coupled to the multiplexer, the detection circuit configured to detect the presence of the object in response to detecting a difference between a measured characteristic that depends on a frequency at which a resonant sense circuit of the plurality of resonant sense circuits is resonating and a corresponding characteristic that depends on the resonant frequency of the resonant sense circuit.

2. The apparatus of claim 1 , wherein each coupling circuit comprises one of:
a capacitor electrically connected between the electrically conductive structure and the multiplexer, the resonant sense circuit comprising the capacitor and the electrically conductive structure;
at least one capacitor and a coupling loop electrically connected to the multiplexer, the coupling loop inductively coupled to the electrically conductive structure; or
a capacitive voltage divider configured to capacitively couple the multiplexer to the resonant sense circuits.

3. The apparatus of claim 2 , wherein the coupling circuit is configured to reduce a variation of the resonant frequency by the multiplexer in the absence of the object, the capacitor further configured to attenuate electrical signals having frequencies lower than the resonant frequency.

4. The apparatus of claim 2 , wherein each resonant sense circuit comprises an electrically conductive structure, a capacitor electrically connected to the electrically conductive structure, the electrically conductive structure comprising an inductor, and wherein the capacitor and the electrically conductive structure substantially form the resonant circuit and substantially determine the resonant frequency.

5. The apparatus of claim 2 , wherein the capacitive voltage divider comprises a first capacitor and a second capacitor, wherein each resonant sense circuit comprises the first capacitor that is coupled to the electrically conductive structure that comprises an inductor, wherein the first capacitor and the electrically conductive structure substantially form the resonant circuit and substantially determine the resonant frequency, the second capacitor determining an amount of coupling between the resonant sense circuit and the detection circuit.

6. The apparatus of claim 2 , wherein each resonant sense circuit comprises an electrically conductive structure, a capacitor electrically connected to the electrically conductive structure, the electrically conductive structure comprising an inductor, and wherein the capacitor and the electrically conductive structure substantially form the resonant sense circuit and substantially determine the resonant frequency, and wherein the electrically conductive structure is inductively coupled to the multiplexer, determining an amount of coupling between the resonant sense circuit and the detection circuit.

7. The apparatus of claim 1 , wherein the measured characteristic comprises at least one of a measured resonant frequency or a measured quality factor (Q-factor) of the resonant circuit, and wherein the corresponding characteristic is at least one of the resonant frequency or the Q-factor of the resonant circuit.

8. The apparatus of claim 1 , wherein the multiplexer comprises a lead line electrically connected to the coupling circuit, and wherein the coupling circuit is further configured to reduce a variation of the resonant frequency by the lead line in the absence of the object.

9. The apparatus of claim 1 , wherein the plurality of electrically conductive structures comprise a first electrically conductive structure and a second electrically conductive structure, different from the first electrically conductive structure, the second electrically conductive structure configured to wirelessly transmit power via a magnetic field at a level sufficient to power or charge a load.

10. The apparatus of claim 9 , further comprising a transmit circuit configured to apply an alternating current to the second electrically conductive structure at a frequency, wherein the resonant frequency of the resonant circuit is higher than the frequency of the alternating current.

11. The apparatus of claim 9 , wherein the first electrically conductive structure comprises a first loop defining a first plane, wherein the second electrically conductive structure comprises a second loop defining a second plane substantially parallel with the first plane, wherein the first loop is positioned over at least one of an area enclosed by the second loop or overlapping the second loop.

12. The apparatus of claim 11 , wherein the loops of the plurality of sense circuits positioned in the multi-dimensional loop array collectively defining a third plane, and wherein the loops collectively cover at least the area enclosed by the second loop.

13. The apparatus of claim 12 , wherein a diameter of each of the loops of the plurality of resonant sense circuits is substantially equal to or less than ten percent of a diameter of the second loop.

14. The apparatus of claim 12 , wherein a diameter of each of the loops of the plurality of sense circuits is substantially equal to or greater than twice a size of the object.

15. The apparatus of claim 12 , wherein the detection circuit is further configured to detect the presence of the object in response to detecting a difference between respective measured characteristics that depend on frequencies at which each of the resonant sense circuits are resonating and corresponding characteristic that depend on the respective resonant frequencies.

16. The apparatus of claim 1 , wherein the measured characteristic comprises a measured resonant frequency, and wherein the detection circuit is configured to measure an impedance response of the resonant sense circuit over a range of frequencies including the resonant frequency and configured to determine the measured resonant frequency based on the impedance response.

17. The apparatus of claim 1 , wherein the measured characteristic comprises a measured resonant frequency, wherein the detection circuit comprises at least one of:
a swept frequency generator configured to drive the resonant circuit with a signal over a range of frequencies and stopping driving the resonant circuit when resonance is detected to determine the measured resonant frequency;
a pulse generator configured to measure a frequency response of the resonant circuit to determine the measured resonant frequency; or
a pseudo-random noise generator configured to measure the frequency response of the resonant circuit to determine the measured resonant frequency.

18. The apparatus of claim 1 wherein the resonant sense circuit is a first resonant sense circuit, wherein the resonant frequency is a first resonant frequency, wherein the coupling circuit is a first coupling circuit,
wherein the apparatus further comprises a second resonant sense circuit having a second resonant frequency comprising a second electrically conductive structure, the apparatus further comprising a second

Assignees

• Qualcomm Inc

Inventors

• Widmer Hanspeter
• Bittner Markus
• Sieber Lukas
• Fischer Marcel

Classifications

• B60L53/37

  using optical position determination, e.g. using cameras · CPC title

• B60L55/00

  Arrangements for supplying energy stored within a vehicle to a power network, i.e. vehicle-to-grid [V2G] arrangements · CPC title

• B60L53/63

  in response to network capacity · CPC title

• B60L53/30

  Constructional details of charging stations · CPC title

• B60L53/65

  involving identification of vehicles or their battery types · CPC title