Research On Broadband Circularly Polarized Rectennas

Microwave power transmission(MPT) technology, which brings a profound impact on human life, has got a lot of attention recently. As the core device of the MPT, the design of rectennas is vital for the development of MPT. Most studies of the rectennas have focused on the linearly polarized rectennas and narrow band rectennas. However, the narrow band rectenna is bandwidth limited, thus restricting its applications; and linearly polarized rectenna needs polarization aligned when receiving electromagnetic waves, thus limiting its placement location. Therefore the design of broadband and circularly polarized rectennas has important significance for the MPT.This thesis introduces the research on broadband circularly polarized rectennas. Two antennas with wideband and good circular polarization characteristics, and a wideband rectifying circuit with higher conversion efficiency, are designed, with which a wideband circularly polarized rectenna with good performance is constituted. The circular polarization bandwidth of the rectenna is from 1.9 GHz to 2.5 GHz, and the conversion efficiency is higher than 43%, up to 63%. The following contents are included in this thesis.The first chapter introduces the background and significance of the rectennas, and the significance and the status of the research on broadband circularly polarized rectennas.The second chapter gives the theoretical knowledge of rectennas, including the basic principles of microstrip antennas, the circular polarization, the filters and the analysis of rectifier diodes.The third chapter presents two broadband circularly polarized antennas. The one is a dual-broadband circularly polarized antenna which is realized with mode analysis, working in the dual-band of 2.00 GHz-2.65 GHz and 5.48 GHz-6.00 GHz, and another is a CPW-fed broadband circularly polarized antenna which is based on the out-field interfering method, with the bandwidth exceeding 1 GHz and the center frequency at 2.35 GHz.The fourth chapter introduces the design of a broadband rectifier circuit. A Schottky diode HSMS8101 and the half-wave rectification are adopted to form the rectifier circuit, which has a wideband microwave rectification function and a best working band of 1.90 GHz-2.50 GHz.Chapter V presents the co-simulation of the antenna and the rectifier circuit, and the two parts are connected to optimize the parameters to achieve good performance.In Chapter VI, the thesis is summarized and the future prospects of the subject are presented.