Wireless Power Transfer in the Radiative Near Field

Gowda, Vinay R.; Yurduseven, Okan; Lipworth, Guy; Župan, Tomislav; Reynolds, Matthew S.; Smith, David R.

doi:10.1109/lawp.2016.2542138

Cited by 98 publications

(42 citation statements)

References 9 publications

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“…If the distance between source and receiver is within the Fresnel zone (also termed the "radiating near-field," 2 0 2D d   ), and a line of sight is available, then a high efficiency WPT system can be realized by using a large aperture that acts as a lens, concentrating electromagnetic energy at a focal point where the receiving aperture is positioned 9,10,11 . In this scenario, a method of dynamically creating and moving a focal spot is needed.…”

Section: Introductionmentioning

confidence: 99%

An analysis of beamed wireless power transfer in the Fresnel zone using a dynamic, metasurface aperture

Smith

Gowda

Yurduseven

et al. 2017

Journal of Applied Physics

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Wireless power transfer (WPT) has been an active topic of research, with a number of WPT schemes implemented in the near-field (coupling) and far-field (radiation) regimes. Here, we consider a beamed WPT scheme based on a dynamically reconfigurable source aperture transferring power to receiving devices within the Fresnel (near-zone) region. In this context, the dynamic aperture resembles a reconfigurable lens capable of focusing power to a well-defined spot, whose dimension can be related to a point spread function (PSF). Near-zone focusing can be achieved by generating different amplitude or phase profiles over the aperture, which can be realized using traditional architectures, such as phased arrays. Alternatively, metasurface guided-wave apertures can achieve dynamic focusing, with potentially lower cost implementations. We present an initial tradeoff analysis of the near-zone WPT concept, relating key parameters such as spot size, aperture size, wavelength, focal distance, and availability of sources. We find that approximate design formulas derived from the Gaussian optics approximation provide useful estimates of system performance, including transfer efficiency and coverage volume.The accuracy of these formulas is confirmed using numerical calculations.

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Section: Introductionmentioning

confidence: 99%

An analysis of beamed wireless power transfer in the Fresnel zone using a dynamic, metasurface aperture

Smith

Gowda

Yurduseven

et al. 2017

Journal of Applied Physics

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“…Focusing the aperture radiated wavefront over a focal point can be achieved within the radiative near-field region of a reflecting surface, which is known as the Fresnel region. The distance for the radiative near-field region of a finite size aperture with a size D falls within the following interval [29], [31]:…”

Section: B Near-field Beam-focusingmentioning

confidence: 99%

Intelligent Reflecting Surfaces With Spatial Modulation: An Electromagnetic Perspective

Yurduseven

Assimonis

Matthaiou

2020

IEEE Open J. Commun. Soc.

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Electromagnetic wave control using the concept of a reflecting surface is first studied as a near-field and a far-field problem. Using a secondary source present in a wireless communication environment, such as a backscatter tag, it is possible to leverage the incoming radiation from the source as a reference-wave to synthesize the desired wavefront across the reflecting surface, radiating a field of interest. In this geometry, the phase grating, which is synthesized using an array of sub-wavelength unit cells, is calculated by interacting the incident reference-wave and the desired wavefront, similar to a hologram. When illuminated by the reference-wave, the reflected wavefront from the calculated phase grating is guaranteed to constructively add in the direction of the desired radiation (beam-steering in the far-field) and also focus at the intended depth (beam-focusing in the radiative near-field). Next, leveraging a dynamic modulation mechanism in the context of an intelligent reflective surface (IRS) illuminated by a backscatter tag, we demonstrate that one can selectively focus and defocus at an arbitrarily positioned receiver within the 3D field of view of the reflecting surface. This enables the control of the amplitude of the radiated electric field at the receiver location, paving the way for a spatial modulation mechanism by means of reconfiguring the reflecting surface in a backscattered wireless communication environment. In addition to the phase modification approach on a unit cell level to reconfigure the aperture radiated wavefronts, we finally present a time varying IRS concept making use of a time-delay based approach relying on a delay adjustment between the reflection coefficients of the IRS' unit cell lattices.

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“…The optimum phase sets for the multiple Tx antennas are implemented at each Tx element to focus the beam at the point where the Rx is located. In [29], a focused antenna array with 64 Tx antenna elements and 16 Rx antenna elements were reported for the 5.8 GHz frequency band. The phases for the Tx antenna elements were controlled using different lengths of the transmission lines at the inputs of the antennas.…”

Section: Introductionmentioning

confidence: 99%

LUT-Based Focal Beamforming System Using 2-D Adaptive Sequential Searching Algorithm for Microwave Power Transfer

Bae

Koo

et al. 2020

IEEE Access

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This paper presents a look-up table (LUT)-based focal beamforming system that can effectively transmit RF power up to mid-range distances (≤ 3 m) including when the Rx is in the nearfield zones. The Tx elements control and radiate signals for the Rx even at the near-field zone ensuring the received signals are in-phase. Since the proposed system uses a LUT for storing the phase sets of the signals for the Tx elements, it requires only very simple hardware and a very simple adaptive control algorithm compared to conventional retroreflective method. In order to track the moving Rx, a 2-D adaptive sequential searching algorithm is proposed. The system can find the optimum phase set by sequentially searching the phase sets for a predetermined 2-D area. The LUT of the phase sets are generated using geometric analysis over the entire 2-D area where the Rx could be located. To verify the proposed method, a 5.2 GHz mid-range (≤ 3 m) MPT system composed of a 4×8 Tx array and a 2×3 Rx array was designed and implemented. Using the proposed 2-D adaptive sequential searching algorithm, the optimum phase set for focal beamforming can be quickly found for a given position of the Rx. In our experiments, the results showed an RF power level of 177.8 mW was received at the Rx with a distance of 1 m with a total radiated RF power of 16 W. Since the measured received power levels for various Rx positions agree well with the simulation results, the proposed system was proved to be an excellent candidate for the practical application. INDEX TERMS Microwave power transfer, Look-up table, Focal beamforming, 2-D adaptive sequential searching algorithm.

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Wireless Power Transfer in the Radiative Near Field

Cited by 98 publications

References 9 publications

An analysis of beamed wireless power transfer in the Fresnel zone using a dynamic, metasurface aperture

An analysis of beamed wireless power transfer in the Fresnel zone using a dynamic, metasurface aperture

Intelligent Reflecting Surfaces With Spatial Modulation: An Electromagnetic Perspective

LUT-Based Focal Beamforming System Using 2-D Adaptive Sequential Searching Algorithm for Microwave Power Transfer

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