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Recently, the next generation (5-th generation: 5G) mobile communication systems have been actively investigated all over the world. Various systems exist when considering the microwave bands after the introduction of 5G systems. Hence, the propagation characteristics when considering the interference among the systems is very important. In this paper, we compare the characteristics of loss when radio waves propagate from outdoor to indoor (O2I) through a window at 5 GHz band where many IoT devices are expected to be used. In this report, we show O2I penetration loss characteristics at 5 GHz for different incident angles considering not only vertical but horizontal plane.

This paper describes the fabrication process of the MEMS microphones on InP substrates. The process is based on ozone ashing of the photoresist to fabricate a hollow structure. This process was demonstrated to be damage-free, and suitable for integration with HEMTs.