0191-9067/85 $3.00 + .00 Copyright ® 1985 SUNSAT Energy Council THEORETICAL AND EXPERIMENTAL STUDY ON RECTENNA ARRAY FOR MICROWAVE POWER TRANSMISSION SABURO ADACHI and YASUSHI SHIMANUKI Faculty of Engineering Tohoku University Sendai, Japan Abstract — In this paper, we describe a theoretical and experimental study on a rectenna array for microwave power transmission. The conversion efficiency of microwave energy to DC and a spurious radiation of harmonics generated by the rectenna were theoretically investigated. Furthermore, we actually composed the rectenna and measured the conversion efficiency. It was shown that our experimental results agree with the theoretical results. INTRODUCTION A receiving antenna used for microwave power transmission is generally called a rectenna. As an antenna element, various types of antennas have been considered (1,2). In this paper, we deal with a half-wave dipole antenna array above a reflecting plane as a rectenna. This system consists of a large number of rectenna elements, each of which converts the incident microwave energy to DC. Each rectenna element includes a Schottky-barrier diode to rectify microwave energy, an input filter to suppress the spurious radiation of harmonics, and an output filter to pass the DC component only. It is necessary for such rectenna to suppress a spurious radiation of harmonics generated by the diode to a sufficiently low level, and to have a high RF-DC conversion efficiency. It is also important to construct the necessary microwave circuits as compact as possible. For the above reasons, we fabricated the conversion circuits by means of microwave integrated circuit technique. THEORY To estimate the theoretical conversion efficiency from RF energy to DC energy and the spurious radiation of harmonics, each rectenna element is represented by an equivalent circuit. The conversion efficiency and the spurious radiation are obtained numerically by solving the nonlinear circuit equation by the Newton-Raphson iteration method (3). The input impedance of the rectenna element was obtained by assuming an infinite planar half-wave dipole array above a perfectly conducting plane (4). The numerical examples of the conversion efficiency and the spurious radiation of harmonics are shown in Fig. 1 and Fig. 2, respectively.
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