Fukuro Koshiji

Human body communication between fingertip and wrist using stationary and wearable devices

Human body communication (HBC) is expected to become a unique man-machine interface because the transmission path is established only when the user touches the target device. In this study, HBC between a stationary device and a wearable device worn on the wrist was investigated. Transmission characteristics between the devices and electric field around the human body model were calculated by electromagnetic field analysis. The transmission characteristics from the stationary device to the wearable device were about -56 dB, which suggests a stable bidirectional transmission. The S21 decreased more than 30 dB when stationary signal electrode and fingertip were 5 cm apart, indicating that contact is necessary for transmission.

A broadband loop antenna for ultra-wideband radio

In recent years, radio communication using ultra-wideband (UWB) technology has shown great promise for healthcare and medical applications. Antennas for UWB communication, using a frequency band from 3.1 to 10.6 GHz, require suitable wideband characteristics compared with antennas for conventional narrow band wireless communication. Although many UWB antennas have been investigated and developed by several research institutes so far, it is difficult to find a loop type of antenna with broadband characteristics covering UWB frequency band. A loop antenna can be useful and effective component used in wristwatch and bracelet typed devices for the healthcare, because it is easy to build in the bracelet of them. Therefore, it is valuable to study and develop the loop type of the antennas for the wearable devices. In this paper, a loop type of the UWB antenna was proposed and investigated. The Finite Difference Time Domain method was used for the electromagnetic analyses of the antenna characteristics. As a result, the VSWR characteristics of the proposed antenna were less than 2.0 over the UWB frequency band enough in practical use.

Multilayered phantom for input impedance evaluation of human body communication electrodes

This paper presents the input impedance measurement of a human body communication electrode by using newly developed multilayered phantom. Based on the comparison between analysis and measurement values, it was found that the multilayered phantom can be used for accurate evaluation.

Transmission characteristics around human body standing on the electrode located on the floor surface for human body communication

In this study, we focused on the human body communication between an electrode located on the floor surface and a wearable electrode located on the forearm, and their transmission characteristics were investigated. As a result, the transmission characteristics S21 between the electrode on the floor and that on the arm were −61.6 dB and −56.8 dB when the single or dual electrode for the wearable receiver, respectively. We confirmed that the wearable receiver with dual electrode was suitable for the better transmission.

A cross type of unbalanced dipole antenna with the bent type of semicircular and trapezoidal radiating elements

In recent years, radio communication using ultrawideband (UWB) technology has shown great promise for ubiquitous application. We have already investigated and developed the cross type of unbalanced dipole antenna with semicircular and trapezoidal radiating elements, and we have confirmed that the cross type of unbalanced dipole antenna performed with VSWR characteristics less than 2.0 over the UWB frequency band. However, the cross type of unbalanced dipole antenna is too large for the antenna built in mobile equipment. In this paper, we investigated miniaturizing the cross type of unbalanced dipole antenna, and we proposed a miniaturized antenna, a cross type of unbalanced dipole antenna with the bent type of semicircular and trapezoidal radiating elements. As a result, the VSWR characteristics of the proposed antenna was less than 2.0 over the UWB frequency band enough in practical use.

A tapered loop antenna with broadband characteristics for ultra-wideband radio

In recent years, radio communication using ultrawideband (UWB) technology has shown great promise for healthcare and medical applications. Although many UWB antennas have been investigated and developed by several research institutes so far, it is difficult to find a loop type of antenna with broadband characteristics covering UWB frequency band. A loop antenna can be useful and effective component used in wristwatch and bracelet typed devices for the healthcare, because it is easy to build in them. In this paper, a loop type of the UWB antenna was proposed and investigated. The Finite Difference Time Domain method was used for the electromagnetic analyses of the antenna characteristics. As a result, the VSWR characteristics of the proposed antenna were less than 2.0 over the UWB frequency band enough in practical use.

Electromagnetic characteristics of body area network using magnetically-coupled wearable coils worn on bent arm

We have proposed body area networks using magnetic coupling between coils worn on an arm, and confirmed that the transmission characteristics were improved more than 20 dB compared with those of the conventional human body communication using electrodes in contact with the body. However, the arm will be bent with various angles in daily life. In this paper, electromagnetic characteristics such as transmission characteristics between the wearable coils worn on the bent arm and magnetic field distributions around the coils and arm were investigated. As a result, the transmission characteristics were stable and hardly influenced against bending the human arm with various angles, and sufficient biocompatibility with specific absorption rate less than 2 W/kg was confirmed.

Broadband antenna with asymmetrical radiating elements for cognitive radio system

In recent years, cognitive radio system has been receiving particular attention as a promising technology in order to materialize efficient network access. In this paper, heightening upper limit frequency of the wideband antenna for cognitive radio system was investigated by employing three types of the antenna element variations. As a result, the antenna with the VSWR less than 2.0, employing asymmetrical elements, was obtained in the frequency range of 3.1 GHz to 18 GHz. Although the radiation patterns were slightly distorted, it was acceptable in practical use.

Transmission characteritics of short-range wireless communication using magnetically-coupled spiral coils

Recently, Near Field Communication (NFC) technology such as 13.56 MHz band-RFID has drawn a lot of attention as a short-range wireless communication technology for mobile and wearable devices. Although the NFC is a useful wireless communication within a few-centimeter area, it is not so convenient communication technology in the short-range from a few decimeters to meters. In this paper, in order to enhance the conventional NFC, the short-range wireless communication using magnetically-coupled spiral coils was proposed, and its transmission characteristics and magnetic field distributions were investigated. As a result, the transmission characteristics were stable, even if the receiving coil was tilted within 90 degrees to the transmitting one.

Proposal of the cross type of unbalanced dipole antenna with the bent type of semicircular and trapezoidal radiating elements

In recent years, radio communication using ultra-wideband (UWB) technology has shown great promise for ubiquitous application. We have already investigated and developed the cross type of unbalanced dipole antenna with semicircular and trapezoidal radiating elements, and we have confirmed that the cross type of unbalanced dipole antenna performed with VSWR characteristics less than 2.0 over the UWB frequency band. However, the cross type of unbalanced dipole antenna is too large for the antenna built in mobile equipment. In this paper, we investigated miniaturizing the cross type of unbalanced dipole antenna, and we proposed a miniaturized antenna, a cross type of unbalanced dipole antenna with the bent type of semicircular and trapezoidal radiating elements. As a result, the VSWR characteristics of the proposed antenna was less than 2.0 over the UWB frequency band enough in practical use.