Electromagnetic time reversal focusing of near field waves in metamaterials

Number: 10230167
Published: 2019-03-12
Filed: 2017-09-29
Assignee: DISNEY ENTERPRISES, INC.
Inventors: Sample; Alanson, Chabalko; Matthew
CPC: H01Q15/0086; H01Q19/062; H02J50/27
Verdict: Medium Hardware
Source: Google Patents · FreePatentsOnline

The keeper's note

Electromagnetic time reversal focusing near field waves metamaterials (wireless power, Sample).

Abstract

Selective focusing of electromagnetic energy via the electromagnetic time reversal in the near field of a metamaterial. The disclosure begins with fundamental mathematics, and then is extended to the experimental realm where focusing in space and time of the magnetic fields in the near field of a 1-Dimensional metamaterial is shown. Under time reversal focusing, peak instantaneous fields at receiver locations are at minimum 200% greater than other receivers. The strongly-selective focusing capabilities of the system can be employed to show individual and selective powering of light emitting diodes connected to coil receivers placed in the near field of the metamaterial. The results show the possibility of improving display technologies, near field imaging systems, increasing channel capacity of near field communication systems, and obtaining a greater control of energy delivery in wireless power transfer systems.

Background

BACKGROUND(1) Precise control of electromagnetic energy on a deeply subwavelength scale in the near field regime is a fundamentally challenging problem. Generally, subwavelength scales are defined as length scales smaller than the free space wavelength of an electromagnetic wave oscillating at a given frequency. More specifically, in the RF frequencies used in RFID (nominally 1 GHz, although it covers a range at least as wide as 100 kHz to 10 GHz), the wavelength is in the range of 30 centimeters, so the subwavelength scale includes distances smaller than this. The ability to control and focus energy on a subwavelength scale is necessary for innovation in technologies, for example, such as near field imaging, near field communication (NFC), radio frequency identification (RFID), and wireless power transfer. These examples rely on manipulation of electromagnetic energy on a subwavelength scale, and would benefit greatly from techniques that allow manipulation of this energy on scales that are smaller than a wavelength.(2) Manipulation of electromagnetic (EM) energy in the subwavelength regime is a topic of broad interest to physicists and engineers alike. In the far field regime, a technique used to focus energy (with resolution even below the classical diffraction limit) at a desired point in space and time is known as the electromagnetic time reversal (TR). Electromagnetic time reversal (TR) refers to the invariance of Maxwell's Equations even when time, t, is replaced by it

Claims

1. A method for focusing RF energy, comprising: providing an RF energy source that generates RF electromagnetic energy in a predetermined RF frequency range having a center RF frequency and a corresponding center RF wavelength; providing a metamaterial that has a spatially-periodic characteristic, the metamaterial having a first location therein and a second location therein, wherein the second location is located at a distance from the first location that is less than the center RF wavelength; providing a source port coupled to the RF energy source, the source port positioned adjacent to the first location in the metamaterial; and applying a time-varying RF electromagnetic energy signal with the RF energy source to the source port, wherein the time-varying RF electromagnetic energy signal is a time-reversed version of an impulse response that would be received at one of the first and second locations in response to an impulse of RF electromagnetic energy introduced into the other of the first and second locations. 13. A method for focusing RF energy, comprising: providing an RF energy source that generates RF electromagnetic energy at a predetermined RF frequency range having a center RF frequency and a corresponding center RF wavelength; providing a metamaterial that has a spatially-periodic characteristic, the metamaterial having a first location therein and a second location therein, wherein the second location is located at a distance from the first location that is less than the center RF wavelength; applying an impulse of RF electromagnetic energy into one of the first and second locations; recording an impulse response at the other of the first and second locations in response to the impulse of RF electromagnetic energy; producing a time-reversed time-varying RF-electromagnetic energy signal based on the recorded impulse response; providing a source port coupled to the RF energy source, the source port positioned adjacent to the first location in the metamaterial; and applying to the source port the time-reversed time-varying RF electromagnetic energy signal with the RF energy source. 17. A system, comprising: an RF energy source that generates energy at a predetermined RF frequency range having a center RF frequency and a corresponding center RF wavelength; a metamaterial that has a spatially-periodic characteristic; an RF energy source terminal located at a first location and a first orientation relative to the metamaterial; and an RF energy receiver terminal located at a second location and a second orientation relative to the metamaterial, wherein the second location is located at a distance from the first location that is less than the center RF wavelength; wherein the RF energy source applies a time-varying RF electromagnetic energy signal with the RF energy source to the source port, wherein the time-varying RF electromagnetic energy signal is a time-reversed version of an impulse response that would be received at one of the first and second locations in response to an impulse of RF electromagnetic energy introduced into the other of the first and second locations.