Optimal Design Of Near-field Shaping Antenna Array

With the growing up of the near field communication system,the non-contact microwave detection system and the life detection system,more and more attention has been paid to the antenna array working in the near-field.In this paper,three typical near-field shaping antenna arrays are designed with the near-field array antenna as the research object.In the optimization process,multiple dipole antennas used as auxiliary receiving antenna arrays are placed in the region where radiations need to be strengthened.The optimal excitation distributions of the driving signals of transmitting antenna array are achieved if the power transmission efficiency between the transmitting and receiving system is maximized.The main research includes:1.Firstly,a 6 elements beam-forming antenna array for smart shelf applications with center frequency at 922.5 MHz is designed and fabricated.Both the simulation and measurement show that a uniform electrical field distributions occurs in 170mm above the array.On this basis,a circularly-polarized beam-forming antenna operating at 922.5 MHz is designed.This design proposes with circularly-polarized microstrip antenna as antenna element.The simulation shows that the uniform electric field in the near field area above the array 170mm has been able to fully cover-the antenna array.2.Finally,a multi-point wireless power transmission system with 12-element monopole antenna is designed at 2.45 GHz.In order to satisfy the configuration of multi-target wireless power transmission systems in various shapes,a voltage control circuit is designed to provide an appropriate excitation distribution for printed monopole antenna array.Three design examples are presented to validate the method,in which the multi targets are shaped into a square,a circle and a eapital letter L,respectively.The experimental results proved that the quadrilateral printed monopole antenna array can achieve multi-point concurrent wireless power transmission.