Koichi Yamaoka

Range Finding by Using NRD Guide Pulse Radar Front-End at 60 GHz

An NRD guide pulse radar front-end was fabricated for level sensor applications at 60 GHz. Main emphases were placed on circuit configuration and digital signal processing of multi-reflection for short range detection. Typically, an oscillation power is divided by a junction circuit and is introduced into two parts. One is for transmitter, and the other is for LO wave to construct hetero-dyne detection in receiver and the frequency of the former is up-converted so as to be different from the frequency of the LO wave, and thus, an amplifier is installed in the transmitting side due to low power of the up-converted millimeter-wave. In this paper, we proposed a new circuit configuration, which consists of a Gunn oscillator with two output ports to eliminate a junction circuit, a direct pulse-modulator to obtain a high level transmitting power without an expensive millimeter-wave amplifier, and a filter-based down-converter with an up-converter as a local oscillator. Multi-reflection between the radar front-end and target was removed by introducing an FPGA-based digital signal processing including high-speed counting, memorizing, and averaging. Good range finding was performed because the error was less than 1 % for the distance from 2 m to 40 m

Development of a pin-post insulator with built-in metal oxide varistors for distribution lines

A 6.6 kV pin-post insulator, incorporating ZnO varistors, has been developed in order to reduce line faults caused by direct lightning strikes, thereby reducing and simplifying maintenance work on distribution systems. The developed insulators are interchangeable with conventional pin insulators and can withstand internal fault currents twice upon their failures. The simulated results regarding the response of the developed insulators to direct lightning strikes on an overhead ground wire agreed well with the experimental results. Simulation studies also revealed that installing the developed insulators on every two poles reduces the line-fault rate of present distribution lines in case of direct lightning strikes by 33%, while installing them on every pole reduces the rate by 97.5% or about 1/40 of the original value.