Akimasa Okada

Two-dimensional communication technology inspired by robot skin

A two-dimensional communication device proposed in a recent paper is a device in which signals travel freely between arbitrary points in flexible two-dimensional space using two-dimensionally-spread electromagnetic field. The new form of communication solves the wiring problems in various situations. It also has advantages over wireless communication. It consumes less energy for signal transmission, it can provide energy for the connected elements, and the communication capacity is larger because multiple 1D signal chains transmit signals simultaneously. In this paper, we demonstrate examples of high-speed signal transmission through flexible 2D layers with proximity interfaces.

UWB 2D communication tiles

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.

Measuring Myoelectric Potential Patterns Based on Two-Dimensional Signal Transmission Technology

In this paper, we propose a new man-machine interface which measures two-dimensional patterns of myoelectric potentials from a surface of a forearm. Measuring high density 2D patterns of the myoelectric signals makes it possible to predict the movements of ones fingers and forearm before a limb actually moves. The key issue is the wiring to each electrode for realizing such a device that covers whole area of the forearm with high density electrode array. The wires also constrain the motion of the forearm. To solve this problem, we adopt a two dimensional communication (TDC) sheet as a substitution for the individual wires. Electrical power is also supplied through the TDC sheet to each sensor by microwave as well as the signal. Based on this technology, we show that small sensing units without electrical contacts to the TDC sheet can measure the EMG signal free from the common mode noise

Feasibility study on OFDM signal transmission with UWB 2D communication tile

The concept of UWB 2DC tile as a practical implementation of UWB 2DC was proposed in the previous research. In this paper, we evaluate the feasibility of OFDM signal transmission through a two-dimensional communication (2DC) sheet in the high-band of ultra-wide band (UWB). First, we examine the effect of a thick surface insulator put on the sheet that weakens the connection between the 2DC sheet and the device on the surface insulator. Experiments are conducted to clarify the physical property of the connection. Second, we examine signal transmission via the 2DC sheet with a pair of UWB communication devices. Based on the both experimental results, we ensure that OFDM UWB 2DC is feasible with a practical carpet material on the sheet.

Time domain characteristics of multiple UWB 2D communication tiles

In this paper, we analyze time domain characteristics of multiple ultra-wide band (UWB) two-dimensional communication (2DC) tiles. The time domain characteristic, especially a root-mean-square (RMS) delay spread is important to properly design a physical layer protocol. In the tile system, signals propagate twice in a sheet-like communication medium at a source tile (signal transmitter unit) and a sink tile (signal receiver unit) that have the same communication characteristics. The signal propagation path indicates that the delay spread of the entire system can be estimated from one-tile characteristics. In order to clarify the delay property, the tile system is modeled and the delay spread are numerically simulated. The simulation results show that the delay spread of the total signal path is about 1.41 times longer than that of the source tile. As the next step, the delay spread of the multiple tiles are evaluated in experiments, which show consistency between the simulation and the measurements. These results provide the estimation on the RMS delay spread of the multi-tile system.

Massive multiple access wireless LAN using ultra-wideband waveguide floor tiles

The unlicensed band for ultra-wideband (UWB) radio systems, 3.1-10.6 GHz, is an attractive frequency resource for indoor high-speed wireless communications. Recently we have proposed a scheme to use the UWBs frequency range for wireless local area networks (WLANs) using off-the-shelf 2.4-GHz WLAN devices and dedicated frequency converters. The signals converted into the UWBs frequency range are transferred through special floor tiles that guide microwaves with low loss. This demo shows a prototype system consisting of the frequency converters and two-dimensional communication (2DC) tiles.

Evaluation of isolation property of UWB 2DC tile for coexistence with radio signals

In this paper, we evaluate isolation property of an ultra-wide band (UWB) two-dimensional communication (2DC) tile. The UWB 2DC tile is based on 2DC technology and enables a room-size and high-speed network. In 2DC, radio waves are confined in a sheet-like waveguide. An evanescent field is generated above the waveguide and used to establish the connection between the devices with a dedicated coupler. Energy radiated from the waveguide is so small that coexistence between signals in the tile and in the air with little interference in the same room is possible. To evaluate the interference between an over-the-air communication path and an on-tile communication path, the transmittance between an antenna in the air and a feeding coupler on the tile is measured with a vector network analyzer. The measurement is conducted with two typical boundary conditions of the waveguide: a short boundary and an open boundary. The experimental results show that the transmittance is about - 60 dB or less at 600 mm above the tile in each boundary. This value is lower than that of free-space propagation. Therefore, the UWB 2DC tile system can keep the stable and high-speed network even if the same frequency band is shared with in-air UWB communication.