| The Radio Frequency(RF)energy harvesting technology is recycling and reusing electromagnetic energy of low power density distributed in the surrounding space.The RF energy harvesting antenna is the key part of this technology.It captures electromagnetic energy at a specific frequency in the surrounding environment and converts it into direct-current(DC)power by rectifier circuit.We focus on the design of RF energy harvesting antenna and have finished the following work:(1)Based on the multi-band and wide-band requirements of RF energy harvesting,an antenna working in the range of worldwide interoperability for microwave access(Wi MAX)is designed.The multi-chip method and slotting technology are used to realize design goal.The 2.5 GHz band is generated by four semi-circular rings,and a semi-circular radiating patch is added to produce the 3.5 GHz band without changing the total area of the antenna.The 5.2 GHz band is excited by opening a rectangular slot on the ground plate,and a rectangular slot is opened on the ground plate to expand the bandwidth of the antenna in the high frequency band.This can make the antenna improve collection capability of the space electromagnetic wave..(2)Based on the basic theory of microstrip antenna design and the demands of high gain for energy harvesting antennas,an improved antenna is designed by adding a reflector.The electromagnetic band gap structure increases the gain of the antenna and suppress high harmonics.A reflector is placed directly below the antenna to enhance the directivity and gain of the antenna in further.In order to verify the simulation results,the designed antenna was fabricated and measured.The measured results show that the improved electromagnetic band gap antenna can work in the 2.45 GHz band,and the S11can reach below-10d B in the bandwidth range,which has good working characteristics.(3)The high-frequency signal needs to pass through the filter to suppress the harmonic signal,so a low-pass filer was added to realize 2.45 GHz characteristics.It has defected groung structure.Its S11is less than-10d B in the passband range,and S21is lower than-25d B in the stopband,meeting the design requirements.(4)In order to convert the electromagnetic wave energy which is collected by the energy harvesting antenna into DC output for testing,the rectifier circuit should also be applied.Finally,the energy harvesting antenna was tested.The output voltage of RF energy system was measured.The results show that the antenna can harvest a amount of RF energy and convert it into a stable DC output. |
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