Akihito Noda

Selective Wireless Power Transmission Through High-

2-D waveguide power transmission (2DWPT) can potentially provide a safe and wireless means of electricity transfer. Our goal is to develop a 2DWPT system in which the power is transferred only to special receiver devices and not to other objects. For this purpose, a new high-quality (high-Q) factor receiver coupler is designed, while the Q of other general objects are reduced by a thick insulator layer on the sheet. This contrast in Q enables selective power transmission to the receiver coupler. The coupler forms a flat waveguide-ring resonator together with the insulator layer. Full-wave simulations validate the difference of power extraction between the proposed coupler and flat conductor plate resonators as a standard reference of general objects. The performance of the fabricated coupler is also examined on a large open-edged sheet where a standing wave is generated, as well as on a narrow strip-shaped sheet where the standing wave is eliminated. In the case where eight 50-Ω loaded couplers operate on a 90 cm × 60 cm large waveguide sheet simultaneously, the total microwave transmission efficiency achieved 87.7%.

Q

A compact configuration of a 2.45-GHz microwave to dc power conversion circuit realizing a class-F operation is proposed. In the ideal class-F operation, harmonic power dissipations are eliminated by open and short terminations for the odd and the even harmonics, respectively. The proposed antisymmetric configuration of two single-shunt-diode rectifiers do not need explicit filters for the even harmonics. A design example that contains an impedance matching network at the fundamental frequency and a third-harmonic rejection filter is presented. Simulation results show that it also realizes approximately short terminations for the second and the fourth harmonics. A fabricated circuit achieved 77.9% RF-dc conversion efficiency when 27-dBm power of 2.45-GHz microwave was supplied.

Flat Waveguide-Ring Resonator on 2-D Waveguide Sheet

This paper proposes “2D communication (2DC) tiles” for practical implementation of UWB 2D communication. Each tile is a 50-cm square which is the standard size of carpet tiles. The tiles can be easily connected and the covered area is extendable freely. If the surfaces of the desks, walls and floors have 2DC tiles, wide-band connection to the network is established everywhere in a room. As the most fundamental problem of this system, we examine the physical connection property between the standing waves produced in the tile and a coupler put near the surface. The results in the simulations and the experiments show stable UWB communication based on OFDM is achieved with the proposed system.

Compact class-F RF-DC converter with antisymmetric dual-diode configuration

To meet the ever increasing demand for wireless local area network (WLAN) connectivity, we propose to use the frequency range allocated for ultra-wideband (UWB) radios as an alternative spectral resource for conventional WLAN systems. Since the maximum permitted emission of UWB radios is 50-dB smaller than that of conventional WLAN devices, aerial communication range will be shortened to less than 1 m. To enhance the communication range while reducing the emission, two- dimensional communication (2DC) technology can be used. The low power UWB signals can be transferred along a 2DC-tiled floor with acceptably low loss, and can be received at arbitrary points on the floor of a room. This paper presents a scheme to use the UWB 2DC system for WLAN signal transmission. An adopter device is attached to each of WLAN access point and client station. The adopter upconverts WLANs 2.4-GHz signal to 8- GHz (in UWBs frequency range), and downconverts the received 8-GHz signal to 2.4-GHz. The adopter is connected to the antenna port of the WLAN device, and no other modifications to the circuit, firmware, and software of the WLAN device are needed. The upconverted UWB signal is attenuated to the UWBs permitted emission level before sending. Experimental results demonstrate that the WLAN connection through prototype converters and a 2DC sheet can achieve the same order of throughput as the original 2.4-GHz aerial WLAN connection. Since each converter can choose individual upconversion frequency from the UWBs frequency range, the WLAN devices in the system virtually share the UWBs bandwidth up to 7 GHz, much wider than the 80- MHz bandwidth originally allocated for 2.4-GHz WLAN devices.

UWB 2D communication tiles

In this paper we propose a new planar proximity coupler for ultra-wideband (UWB) two-dimensional communication (2DC). In 2DC systems, microwaves are transmitted into and received from a waveguide sheet across the surface by using a dedicated coupler. The coupler, differently from ordinary antennas, transmits microwaves not into the air but into the sheet, and receives them not from the air but from the sheet. The coupler is a circular conductive patch, and an inner smaller circular portion of the patch is removed. The structure is complementary to a circular patch antenna for over-the-air UWB communication. The return loss of a fabricated coupler was less than -5 dB in a frequency range of 3.1-10.6 GHz. The transmittance between two identical couplers laid on a 135 × 68-cm2 anechoic sheet was also evaluated. The measured results indicate that the major signal transmission path was not in the air but through the sheet, as expected.

Wireless LAN on 2-D Communication Tiles Using Ultra-Wideband as an Alternative Spectrum Resource

This paper describes a new type of couplers which has small size and enables power transmission through Two-Dimensional Communication (2DC) Sheet. Our 2DC system allows non-contact power transmission using microwaves. The power transmission capacity is limited because of the risk of human exposure to microwaves. Our goal is supplying 1 W/cm power and satisfying two criteria as follows. First, localized specific absorption rate (SAR) must conform to a regulation based on the International Commission on Non-Ionizing Radiation Protection (ICNIRP) Safety Guidelines. Second, the coupler size should be less than 100 mm in length and width for convenient use. To achieve the goal, we propose coupler which has a capacitive impedance layer on its surface. We verify the validity of the proposal through theoretical analysis of electromagnetic fields in the sheet and coupler. Moreover, a three-dimensional simulation result also supports applicability to real systems. Finally we confirm the feasibility of the new coupler through a verification experiment.

Circular planar coupler for UWB 2-D communication

In this paper we propose a selective wireless power transmission method using a two-dimensional waveguide sheet with a thick insulator layer. The thick insulator layer prevents strong electromagnetic fields induced by general objects put on the sheet. Only a resonant coupler enclosed with a special energy confining structure can extract sufficient power from the sheet. We design a coupler that is enclosed with a multiple-choke structure as an example of realizations. We demonstrate the selectivity through full-wave simulations and experiments. The unwanted power extraction by a planar conductor is less than 2.5%, while the coupler efficiency is 70%.

Power transmission coupler for low leakage 2D-communication sheet

In two-dimensional communication (2DC), devices put on the surface of a two-dimensional waveguide sheet receive microwave power from the sheet through the couplers. This paper clarifies the condition that a resonant object extracts microwave power from the sheet with significant efficiency. A theoretical analysis presents that the higher intensity of electromagnetic field outside the sheet surface is required for the lower surface reactance. That leads to the fact that power extraction from the lower surface reactance inevitably causes the higher power dissipation by the sheet surface resistance. Considering an inequality between the dissipation and the power flowing out of the sheet, we can determine the lower-bound of the surface reactance for efficient power transmission. The minimal surface reactance determines the minimal power leakage ratio and the maximal transmitted power acceptable in terms of electromagnetic compatibility (EMC). In the case of our typical 2DC systems, the lower-bound of the surface reactance and the corresponding leakage ratio are estimated to be 0.32 Ω/sq. and 1.4×10−5, respectively for the 2DC sheet thickness of 2 mm. In the latter part of the paper we design a sheet with the surface reactance of 1.6 Ω/sq. and show an example of couplers applicable to the low reactance sheet.

Selective wireless power transmission through 2D waveguide sheet using strong electromagnetic confinement by choke-enclosed resonant coupler

For applying two-dimensional communication (2DC) technology to the entire floor of a room, the concept of 2DC tile have been proposed. In terms of fabrication, delivery, and implementation, the floor should be covered with multiple pieces of 2DC sheets as small as typical carpet tiles. In this paper, we propose a contactless coupler for signal transmission between adjacent 2DC tiles without any electrical contacts. The simulation and measurement results show that the proposed coupler is sufficiently tolerant of positioning error between a pair of couplers.

The lower-bound of electromagnetic leakage of 2D wireless power transmission

In this paper we propose a room-size ultra-wideband (UWB) wireless communication system for fast data transmission of sensor networks. We use two-dimensional signal transmission (2DST) for wireless communication. In the proposed system, planar waveguide sheet is used as a medium guiding microwave and receiver couplers on the sheet extract microwave across the sheet surface. We design the UWB coupler and demonstrate the validity by numerical simulation. Experimental results show that the fabricated couplers can mediate sufficient power for UWB communication.