Shuichi Sekine

A 950 MHz rectifier circuit for sensor networks with 10 m-distance

A high-sensitivity rectifier is fabricated in a 0.3 /spl mu/m CMOS technology. The circuit can rectify an RF signal less than the NMOS threshold voltage by using a bias voltage between the gate and the drain terminals of a transistor. The IC achieves a 950 MHz signal rectification over -14 dBm corresponding to 10 m-distance communication and recharges a 1.2 V secondary battery.

A triangular loop antenna mounted adjacent to a lossy Si substrate for millimeter-wave wireless PAN

Millimeter-wave wireless communication is expected to be used for wireless personal area network (WPAN) for which a bit rate of 1Gbps or more is needed. Our goal is the development of an antenna suited to a WPAN terminal. Since a small, low-cost antenna with high radiation efficiency and a high gain in a wide- angle range is required for WPAN, the beam scan becomes unnecessary. In this paper, we propose a novel triangular loop antenna with a simple structure which has a feed point on to a semiconductor substrate.

Novel small structure for low profile antenna by analogy with EBG structure

By using the image theorem, the relation between the reflection phase of an infinite plane and the input impedance of the dipole antenna just above the plane has been discussed. It has been confirmed that the dipole antenna matches with 50 Omega when the reflection phase is around pi/2, and it is similar to the dipole antenna above an EBG structure. We have proposed the novel small structure which enables the dipole antenna to lay in low profile to the ground plane. The proposed structure rotates the reflection phase through a frequency band and the dipole antenna just above the structure matches with 50 Omega when the reflection phase is around pi/2. It is concluded that the periodicity of an EBG structure is NOT indispensable to realize a low profile antenna.

Wideband Characteristic of Dipole Antenna on Mushroom-like EBG Substrate with Narrow Gap

In this paper, we adopted the EBG structure for the antenna substrate to achieve low profile antennas. The thin mushroom-like EBG substrates with narrow gaps were fabricated to limit the area size of the substrate to apply small equipments. The impedance and radiation pattern of a dipole antenna were measured when the antenna was closely located above the EBG substrate. It was confirmed that a dipole antenna located 80 mum above the EBG substrate worked well through wideband. It has been observed that the EBG substrate with the area similar with the footprint of the antenna is enough to obtain a good VSWR. The verification of the operation mechanism and the application to wireless small terminals are future works.

Radiation mechanism of H-shaped antenna using parallel resonance mode

It is required to work in various surrounding environments in order that the small antennas used for mobile terminal and RFID tag are located in the vicinity of various objects including the human body and the metal. H-shaped antenna has been proposed to obtain the characteristics not to be changed by circumference environment. The H-shaped antenna has been designed by adjusting offset position and the ratio between the lengths of parallel elements. As a result of examination about the antenna height (h), the shift of input impedance near the metal was the smallest when h=0.04ε.

Small Artificilal Structure for Low Profile Antenna by Analogy wilth EBG Structure

EBG (electromagnetic bandgap) structures have lately attracted considerable attention both for the surface wave reduction and low profile antennas. One of the most remarkable features of EBG structures is their periodicity. Brillouin pointed out the bandgap phenomena by the periodic structure early in the 20th century. Indeed, the surface wave reduction by EBG structures is explained in the same way as Brillouin did. But there seems to be no discussion on whether the periodicity of an EBG structure is indispensable to realize a low profile antenna. In this paper, we propose a small artificial structure for a low profile antenna, which has a single resonant circuit. And the mechanism explanation of a low profile antenna above a certain class of artificial plane is given.