Shigeo Kawasaki

This paper presents the fabrication of an Active Integrated Phased Array Antennas (AIPAA) sensor system prototype utilizing Information, Communication & Energy transfer (ICEt) technology. Through the high-density integration of hardware components and software algorithms, this system enables adaptive adjustments in diverse scenarios, leading to optimal system performance. The proposed prototype demonstrates the capability to fulfill sensing, communication, and energy transfer tasks in various environments, including spacecraft exploration and river disaster warning systems. This research represents a significant step towards the development of advanced wireless sensor networks with ICEt technology for multifunctional applications.

We report on the irreversible and reversible resistance changes for γ-ray irradiation in amorphous GeTe thin films with Ag electrodes. The γ-ray irradiation at a dose of 1 kGy irreversibly decreased the DC resistance by two orders of magnitude. The irreversible resistance change was caused by the formation of a conductive region that consisted of Ag-Te compounds. In-situ real-time DC resistance and AC impedance measurements revealed reversible variations in several electrode structures with DC resistances ranging widely from about 10 kΩ to about 5 MΩ. The DC resistance decreased by 2–5% with a time constant of about 3–7 min following the γ-ray irradiation with a dose rate of 0.5–2 kGy/h, and recovered on interruption. The AC impedance measurement was analyzed with a simple equivalent circuit consisting of a parallel RC circuit of the Ag-diffused GeTe matrix, connected serially to the interface resistance. The interface resistance and the capacitance of the matrix exhibited a fast reversible variation, which is explained by trapping and detrapping of carriers in the charged defects formed by the Ag re-diffusion. The resistance of the matrix showed a slow reversible variation with a time constant of 7 min, similar to the DC resistance. The slow reversible variation is attributed to the growth and dissolution of the conductive region caused by the Ag re-diffusion.

© 2020 IEEE. In this letter, a frequency-tunable rectifier in the $C$-band designed by a hybrid semiconductor integrated circuit (HySIC) concept is proposed. A GaAs monolithic microwave integrated circuit (MMIC) and a Si radio frequency integrated circuit (RFIC) were utilized as the HySIC configuration in the rectifier design. For the purpose of initial confirmation of this design validity, the GaAs and Si chips were fabricated and packaged onto the copper tungsten plate with gold plating. As measured results, frequency-tunable range from 3.82 to 4.55 GHz was measured. Maximum radio frequency (RF)-direct current (dc) conversion efficiency and output dc power in the measured power range from-10.0 to 17.8 dBm were 28.7% and 17.3 mW, respectively.

© 2020 IEEE. The 24 GHz communication system was demonstrated with wireless multi-sensors by wirelessly powering at 5.8 GHz. The wireless sensors for health monitoring in a space vehicle work as the sensors of temperature, humidity, acceleration, illuminance, battery voltage and sound in this study. Under output power of 30W from a GaN transmitter, a GaAs rectifier of energy harvester was operated with more than 80% RF-DC conversion efficiency.