Near-field antennas for accumulating energy at a near-field distance with minimal far-field gain
An example non-inductive, resonant near-field antenna includes: (i) a conductive plate having first and second opposing planar surfaces and one or more cutouts extending through the conductive plate from the first surface to the second surface; (ii) an insulator; and (iii) a feed element, separated from the first surface of the conductive plate by the insulator, configured to direct a plurality of RF power transmission signals towards the conductive plate. At least some of the plurality of RF power transmission signals radiate through the cutout(s) and accumulate within a near-field distance of the conductive plate to create at least two distinct zones of accumulated RF energy at each of the cutout(s). Furthermore, the at least two distinct zones of accumulated RF energy at the cutout(s) are defined based, at least in part, on a set of dimensions defining each of the cutout(s) and an arrangement of the cutout(s).
1. A near-field antenna for transmitting radio frequency (RF) power transmission signals, comprising:
a conductive plate having opposing first and second planar surfaces and one or more cutouts extending through the conductive place from the first surface to the second surface;
an insulator; and
a feed element, separated from the first surface of the conductive plate by the insulator, configured to direct a plurality of RF power transmission signals towards the conductive plate,
wherein:
at least some of the RF power transmission signals of the plurality of RF power transmission signals radiate through the one or more cutouts and accumulate within a near-field distance of the conductive plate to create at least two distinct zones of accumulated RF energy at each of the one or more cutouts; and
the at least two distinct zones of accumulated RF energy at each of the one or more cutouts are defined based, at least in part, on: (i) a set of dimensions defining each of the one or more cutouts, and (ii) an arrangement of the one or more cutouts.
2. The near-field antenna of claim 1 , wherein:
a first cutout of the one or more cutouts forms a first meandering line pattern; and
a second cutout of the one or more cutouts forms a second meandering.
3. The near-field antenna of claim 2 , wherein:
a shape of the first meandering line pattern mirrors a shape of the second meandering line pattern;
the first and second meandering line patterns have the same set of dimensions; and
the shape of the first meandering line pattern is rotated with respect to the shape of the second meandering line pattern.
4. The near-field antenna of claim 1 , wherein a respective cutout of the one or more cutouts has a respective length that is at least as large as a wavelength of a respective RF power transmission signal of the plurality of RF power transmission signals.
5. The near-field antenna of claim 4 , wherein:
the respective cutout includes, at least:
a first cutout portion defined in a first direction; and
a second cutout portion defined in a second direction, the second direction being orthogonal to the first direction;
a first of the at least two distinct zones of accumulated RF energy is created at the first cutout portion; and
a second of the at least two distinct zones of accumulated RF energy is created at the second cutout portion.
6. The near-field antenna of claim 1 , wherein the feed element is a component of a patch antenna, where the insulator is disposed between the feed element and the conductive plate.
7. The near-field antenna of claim 1 , wherein the feed element is a component of a patch antenna that is at least partially encapsulated within the insulator.
8. The near-field antenna of claim 1 , wherein the insulator is selected from the group consisting of: a polymer, a fiber reinforced polymer, glass, and air.
9. The near-field antenna of claim 1 , wherein the at least two distinct zones cover at least 80% of a surface area of the second surface of the conductive plate.
10. The near-field antenna of claim 1 , wherein the at least two distinct zones cover at least 90% of the surface area of the second surface of the conductive plate.
11. The near-field antenna of claim 1 , wherein the at least two distinct zones of accumulated RF energy extend no more than 5 millimeters above the second surface of the conductive plate.
12. The near-field antenna of claim 1 , wherein the at least two distinct zones of accumulated RF energy extend no more than 4 millimeters above the second surface of the conductive plate.
13. The near-field antenna of claim 1 , wherein the at least two distinct zones of accumulated RF energy extend no more than 3 millimeters above the second surface of the conductive plate.
14. The near-field antenna of claim 1 , wherein the plurality of RF power transmission signals is transmitted at a frequency selected from the group consisting of: 5.8 GHz, 2.4 GHz, and 900 MHz.
15. The near-field antenna of claim 1 , wherein:
the near-field antenna is a first near-field antenna and is part of a near-field charging pad that also includes a second near-field antenna that is positioned adjacent to the first near-field antenna within the near-field charging pad; and
respective cutouts associated with the second near-field antenna are rotated relative to the one or more cutouts associated with the first near-field antenna.
16. The near-field antenna of claim 1 , wherein the feed element receives the one or more RF power transmission signals from a power amplifier in response to determining that a wireless power receiver is placed within a predetermined distance of the surface.
17. The near-field antenna of claim 16 , wherein the predetermined distance is less than approximately 5 mm away from the surface.
18. The near-field antenna of claim 17 , wherein:
the predetermined distance is monitored by measuring a signal strength level associated with a transmission received by a processor connected to the near-field antenna; and
the signal strength level is associated with a broadcasted signal received from the wireless power receiver.
19. The near-field antenna of claim 1 , further comprising a conductive housing surrounding the feed element and the insulator, wherein
the conductive housing defines an opening at one end of the housing; and
the conductive plate closes the opening.
20. The near-field antenna of claim 19 , wherein the conductive plate is a first conductive plate and the near-field antenna further comprises:
another insulator disposed on the second surface of the first conductive plate; and
a second conductive plate disposed on top of the dielectric layer, the second conductive plate having one or more additional cutouts.