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Inspired by the envision of space solar power satellite, microwave‐based wireless power transfer has been intensively studied. To date, while significant progresses have been achieved, bottlenecks still exist. Among them, the deterioration of the radiofrequency (RF)‐to‐direct current (DC) efficiency due to the variation of incident microwave power is a major problem. It prevents this technology from many practical applications. In this work, based on the dependence between the incident power density and the resistive DC load, we propose a self‐adaptive approach to mitigate this deterioration by introducing a continuous DC load modulation. Experiments based on a complex‐conjugate rectifying surface showed effective improvements of the RF‐to‐DC efficiency for the incident power density varied in a wide range. [ABSTRACT FROM AUTHOR]

A high‐precision differential microwave dielectric sensor system based on a pair of CSRR‐SIW resonators is introduced. The proposed method consists of four parts: the frequency‐sweeping signal source, the balanced sensor based on CSRR‐SIW, the RMS power detector, and the data acquisition system. Without a vector network analyzer (VNA) and other instruments, the electromagnetic properties of materials can be measured conveniently with the proposed method. In this work, two CSRR resonators inside SIW cavities are used as the balanced RF sensing components, one for measurement and the other for reference. In virtue of the electric field concentration effect of the CSRR and the high Q factor of SIW cavity, the proposed sensor achieves high sensitivity to material under test (MUT), with high isolation between the balanced resonators and strong capability of suppressing the electromagnetic interferences from the external environment. The resonating frequency of the balanced microwave resonator under no‐load condition is 1.587 GHz. With balanced sensor configuration, interferences from the external environment and fabrication errors for the single‐resonator‐based system can be filtered out and compensated automatically, and thus high precision of the dielectric constant measurement can be achieved. The experiment results of proposed differential dielectric sensor system validate that the measurement accuracy of the dielectric constant can reach an excellent level with a relative measurement error below 0.1%. [ABSTRACT FROM AUTHOR]