An Inland Rectenna Using Reflector and Circular Microstrip Antennas KIYOHIKO ITOH, YASUTAKA OWAGA* Summary: A rectenna must have high efficiency for 2.45 GHz to DC conversion, and must suppress re-radiation of higher harmonic microwaves generated by the rectifying diodes. A circular microstrip antenna (CMSA) has an important characteristic to reduce the re-radiation of the higher harmonics. This paper presents an inland rectenna using a reflector and CMSAs. If the primary radiator is placed at an optimum position, we can have the maximum conversion efficiency of the rectifying diodes. We derive several equations which can be used for the optimum design. Moreover, because the reflector is composed of wires, the rectenna passes the sunshine. Thus the SPS system does not effect the environment and human society. Introduction "Rectenna", the earth station terminal in the solar power satellite (SPS) system converts microwave power transmitted from the SPS into a direct current. The rectenna is one of the essential elements in the SPS system. The rectenna must have high efficiency of energy conversion. Also, it must suppress re-radiation of higher harmonic microwaves generated by the rectifying diodes because the higher harmonics may interfere with radio communications and/or may cause hazards to the human body. In this paper, we give an outline of a circular microstrip antenna (CMSA) which has been proposed by the authors, for use as a rectenna. The CMSA in itself reduces the re-radiation of the higher harmonic microwaves. Next we propose the rectenna using a reflector with wires and a primary radiator (receiving area) with CMSAs. We show fundamental expressions which will be useful for designing the rectenna. Since the rectenna passes sunshine, it does not affect the environment and human society. Then we introduce the rectenna in the SPS strawman model which has been discussed by the Institute of Space and Aeronautical Science (ISAS), Japan. We compare the inland rectenna and offshore one, and we show that the inland rectenna has the advantage over the offshore one. Circular Microstrip antenna (CMSA) In other work, a half-wavelength dipole antenna has been investigated for the rectenna. However, the dipole antenna re-radiates a considerable amount of higher harmonic microwaves generated by the rectifying diodes, and a low-pass filter must reduce the higher harmonic components drastically. The authors have proposed the * Faculty of Engineering, Hokkaido University, North 13, West 8, Kita-ku, Sopporo 060 Japan
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