Hisanori Matsumoto

An Experimental Study of Passive UHF RFID System with Longer Communication Range

Radio-frequency identification (RFID) systems are useful for reducing costs in supply chains. The communication range between the reader and the tag is one of the most important points in the application of RFID to supply chain management. We present results of experiments conducted on our passive RFID prototype system that we designed with the aim of increasing the communication range. It uses an intermittent transmission method to reduce the power consumption of the tag IC. Our results show that the power consumption was reduced to about three-quarters by using intermittent transmission with a duty ratio of 40%. Our experimental results indicate that optimization of the transmitting signal is effective for saving power consumption at tag IC and increasing the communication range.

Influence of Underlayer Materials on Preferred Orientations of Sputter-Deposited AlN/Mo Bilayers for Film Bulk Acoustic Wave Resonators

Highly c-axis-oriented aluminum nitride (AlN) films were deposited by reactive rf magnetron sputtering on molybdenum (Mo) films for film bulk acoustic wave resonators (FBARs). We investigated the effect of underlayer materials on the crystalline qualities of AlN/Mo bilayers. AlN/Mo bilayers were sputter-deposited on silicon, silicon dioxide and AlN underlayers under the same sputtering conditions. The results revealed that the AlN underlayer markedly improves Mo film quality, and this greatly affects the orientation of the upper AlN film. By applying the AlN underlayer, we obtained a full width at half maximum of 2.3° from the X-ray diffraction rocking curve of the AlN film grown on a Mo film. We propose that the large surface energy of AlN is the reason the AlN underlayer improves the quality of the Mo films. In the FBAR with the AlN underlayer, a quality factor of 800 and an effective electromechanical coupling coefficient of 5.7% were achieved.

Multilayer Film Piezoelectric Lamb Wave Resonator for Several GHz Applications

We present a film piezoelectric Lamb wave (PLW) resonator based on a newly contrived multilayer film structure for several GHz applications. The multilayer film consists of two piezoelectric AlN layers that are excited by an intermediate electrode layer. Using numerical and experimental methods, we investigated the PLWs characteristics propagating in the multilayer film. Both the simulation and fabrication results indicated that a PLW mode with a phase velocity of above 25000 m/s can be excited in the multilayer film. These results show that our multilayer film structure is suitable for PLW resonators in the GHz range

Variable beamwidth shorted patch antenna array for indoor positioning

Variable beamwidth antennas can optimize the radio coverage of a transmitter for indoor positioning. In this study, we developed a small variable beamwidth antenna array suitable for indoor positioning that is comprised of electrically small shorted patch antennas and is adapted for use with the indoor messaging system (IMES). We did theoretical calculations and experimental measurements to examine the antenna properties. Our results showed that beamwidth variations from 40° to 65° can be obtained and that the boresight gain is adequate for use with IMES transmitters.

Circularly polarized microstrip antenna with an airgap for multi-GNSS applications

We present a new circularly polarized microstrip antenna with an airgap for multiple Global Navigation Satellite System (multi-GNSS) receivers. The airgap structure substantially increases antenna gain and bandwidth. We examined the antenna properties by simulation and measurement. The measured results show the −10 dB bandwidth of 4.9% and the maximum antenna gain above 7.0 dBi over the whole multi-GNSS frequency band. We performed an experiment on receiving satellite signals by a prototype antenna, and confirmed that good CNR values can be obtained over wide elevation angle range of 20 to 90 degree.

Electrically small shorted patch antenna array with switchable radiation patterns for indoor messaging system

A planar antenna array with switchable radiation patterns is presented for an indoor messaging system (IMES) transmitter. The antenna array comprises four electrically small shorted patch antennas, and can switch the radiation patterns between vertical and horizontal modes. The antenna properties were examined by performing theoretical calculations and experiments. A fabricated antenna array on a printed circuit board is as small as 124 mm by 124 mm, and the measurements demonstrate that two radiation patterns of vertical and horizontal modes are obtainable. We believe that the antenna array should improve the usability of the IMES transmitter.

Methods for improving IMES transmitters: Transmission diversity, variable beamwidth antenna, and leaky coaxial cable

IMES is an indoor messaging and positioning system. In the present work, three methods for improving the IMES transmitter are proposed based on the result of a radio acquisition analysis: transmission diversity, a variable beamwidth antenna, and a leaky coaxial cable (LCX). The transmission diversity method increases the possibility of signal acquisition in areas with weak signal. A small-sized variable beamwidth antenna is developed to mitigate the multipath interference in narrow spaces. A field experiment with a LCX in an actual train setup is conducted to verify the effect of the LCX for the positioning of moving vehicles. The evaluation results of the proposed methods suggest their potential to be applied to practical applications.

Development of film bulk acoustic wave resonators based on piezoelectric aluminum nitride

Film bulk acoustic wave resonators (FBARs) have high quality factors (Q) and are smaller than conventional surface acoustic wave devices, so they are particularly suitable for constructing the bandpass filters of mobile phones. This report covers the simulation and fabrication of FBARs consisting of an aluminum nitride (AlN) piezoelectric layer sandwiched between molybdenum (Mo) electrode layers. The simulation was based on Mason’s equivalent circuit model. Other than material Q, the AlN material constants for the FBAR model were those reported by Tsubouchi and Mikoshiba [K. Tsubouchi and N. Mikoshiba, IEEE Trans. Sonics Ultrason. 32, 634–644 (1985)]. The material Q of AlN was assumed to be 1000. Thickness values for the AlN and Mo films were determined by simulation, after which the FBARs were fabricated. Reactive radio‐frequency sputtering and direct‐current sputtering were adopted for deposition of the AlN and Mo films, respectively. In terms of frequency properties, our FBARs achieved Q of 800 and an ...