MICROWAVE-TO-dc CONVERSION LOSS OF RECTENNA* SABURO ADACHI and YUZI SATO Faculty of Engineering Tohoku University Aramaki aza Aoba Sendai 980, Japan Abstract — The rectenna used for microwave power transmission must convert the transmitted microwave power into direct current effectively. In this paper, the rectenna which we previously used in experiments is represented by an equivalent circuit taking account of the conduction loss of the lines. We obtain voltages and currents at each point of the circuit. As a result, the characteristics of the conversion efficiency and losses are clarified, and a design guide for a more efficient rectenna is obtained. INTRODUCTION We have previously made a rectenna using the microwave integrated circuit technique (2) and investigated the microwave-to-dc conversion characteristics of the rectenna experimentally as well as theoretically (6), but there have been no detailed reports about rectenna losses. In this paper, the rectenna losses are investigated in more detail, using an equivalent circuit and taking account of conduction loss of lines in order to obtain a designing guide for a more efficient rectenna. 1. LOSS OF RECTENNA The rectenna is composed of the antenna, input filter, diode and output filter. The input and output filters are low-pass filters; the former suppresses the radiation of the harmonics generated at the diode, and the latter makes the current rectified by the diode flat. There have been some previous studies of making filters by distributed transmission lines (3,5) or lumped elements. In this paper, filters are made by lumped elements so that we simulate our previous experiments. The rectenna is represented by an equivalent circuit, as shown in Fig. 1. The section consisting of V, Ra, La shows the equivalent circuit of an infinite half-wave dipole array antenna arranged with 0.6 wavelength intervals and 0.25 wavelength height above a perfectly conducting plane. As diode parameters in the equivalent circuit of diode (1), those of the diode used in our previous experiments (YHP5082-2824) are chosen for numerical examples. The values of resistances RX,R2, . • ,R?> of respective inductor . . .,L^ are chosen by calculating the conduction loss taking account of the length and thickness of the inductor lines. The circuit equations of the equivalent *Presented al the Fourth ISAS Space Energy Symposium, at ISAS, Tokyo, I March, 1985.
RkJQdWJsaXNoZXIy MTU5NjU0Mg==