| Microwave power transmission(MPT)technology transfers power from one location to another by microwave beam,which is the key technology of the Solar Power Satellite program,the distributed reconfigurable satellite systems,near space airships and wireless sensor networks.The MPT system in millimeter-wave band has the advantages of compact size,high transferring efficiency and is becoming the research hotpoint worldwide.The rectenna is the key component in a MPT system and is used to capture and covert the microwave energy into DC(Direct-Current)power.The basic design theories and implementation methods of Ka band rectennas are studied in this dissertation.Three main subjects are included.Firstly,the millimeter-wave rectifying circuits are studied.Since the great limitations of the theoretical analysis and the software simulation in millimeter-wave rectifying circuit design,the experimental method is adopted to get the input characteristic of the diode.According to the obtained diode input impedance by the test circuit,two rectifying circuits with parallel and series connections are designed.At the frequency of 35 GHz,the measured maximum rectifying efficiency is higher than 51% when the input power is 19 dBm.Meanwhile,when the input power is 10 dBm,the relative bandwidth with the efficiency higher than 30% is 11.4% and 6.3%,respectively,which exhibit the broadband performance.Secondly,three novel high gain and broadband millimeter-wave antennas operating at 35 GHz are proposed.The SIW(Substrate Integrated Waveguide)resonant cavity around the patch is proposed to improve the gain of the SIW slot coupled patch antenna element and 1.5dB enhancement is obtained.A 2×2 patch array is designed with measured gain of 14.7dBi and relative bandwidth of 18.5%.The circular complementary PRS(Partially Refletive Surfaces)and the loaded SIW are proposed to enhance the gain and bandwidth of the dual-polarized Fabry-Perot millimeter-wave antenna.The common operating bandwidth is 7.1% with the the measured gains of 16.1dBi and 15.1dBi for the two polarizations.By loading the designed zero effective permittivity metamaterial units,the Vivaldi antenna with equal radiation beamwidth,high gain and harmonic supression is proposed.The measured gain is improved to 11.1dBi and the relative bandwidth is 38.6%.Thirdly,based on the designed Ka band antennas and rectifying circuits,two types of rectennas and arrays with series connected diodes operated at 35 GHz are proposed.When the input power density is 10mW/cm~2,the conversion efficiencies of the SIW slot coupled patch rectenna and the metamaterial loaded Vivaldi rectenna elements are 35% and 47%,and the output DC power are 3.5mW and 7.5mW,respectively.The rectenna efficiency is higher than the reported results in the literatures.In addition,the designed 4×4 SIW slot coupled patch rectenna array obtains 14% system conversion efficiency when the distance to the transmit antenna is 5cm. |
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