Experimental Study on a Retrodirective System Utilizing Harmonic Reradiation from Rectenna

Tomohiko MITANI  Shogo KAWASHIMA  Naoki SHINOHARA  

Publication
IEICE TRANSACTIONS on Electronics   Vol.E102-C   No.10   pp.666-672
Publication Date: 2019/10/01
Online ISSN: 1745-1353
DOI: 10.1587/transele.2019MMP0004
Type of Manuscript: Special Section PAPER (Special Section on Microwave and Millimeter-Wave Technologies)
Category: 
Keyword: 
wireless power transfer,  rectenna,  harmonics reradiation,  retrodirective system,  direction-of-arrival estimation,  

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Summary: 
A retrodirective system utilizing harmonic reradiation from a rectenna is developed and verified for long-range wireless power transfer applications, such as low-power or battery-less devices and lightweight aerial vehicles. The second harmonic generated by the rectifying circuit is used instead of a pilot signal, and thus an oscillator for creating the pilot signal is not required. The proposed retrodirective system consists of a 2.45 GHz transmitter with a two-element phased array antenna, a 4.9 GHz direction-of-arrival (DoA) estimation system, a phase control system, and a rectenna. The rectenna, consisting of a half-wave dipole antenna, receives microwave power from the 2.45 GHz transmitter and reradiates the harmonic toward the 4.9 GHz DoA estimation system. The rectenna characteristics and experimental demonstrations of the proposed retrodirective system are described. From measurement results, the dc output power pattern for the developed retrodirective system is in good agreement with that obtained using manual beam steering. The measured DoA estimation errors are within the range of -2.4° to 4.8°.