Near Field Focused Planar Antenna With Low Sidelobe And Multiple Focal Points

The antenna generally operates in the far field of the radiation.For some special occasions,it is necessary to gather the energy of the antenna radiation on a particular point in the near field.Near-field-focused antenna research have been studied over a long time.Near-field-focused antenna with high energy density in a specific area can not only be used to improve the detection of medical and industrial detection system and imaging ability,can also be used for access control systems,microwave wireless power transmission system,radio frequency identification system and microwave radio systems.It has the widespread application prospect and the scientific research value.Due to different applications of near-field-focused antenna,the demands for the focal point's characteristics are also different.For example,in the case of microwave hyperthermia applications,it is desired to use the maximum power to heat the cancer tissue without doing harm to healthy tissue.The reason why reducing the side-lobe of focal point in the non-contact microwave induction is that higher side-lobe will have bad influence on its accuracy.The realization of low side-lobe design for near field focusing antenna is an effective way to reduce the influence of side lobes.When the near field focused antenna is used for large area detection,multiple focus points are required to expand coverage or improve position accuracy.In this paper,the near-field-focused array antenna have been studied,embodied in:Firstly,the near-field-focused principles of the planar antenna are analyzed,and the near-field-focused is realized based on the integrated waveguide and the metal circular waveguide.The sub-components of the near-field-focused antenna of the substrate integrated waveguide are analyzed,and the relationship between antenna focal length and focal spot characteristics has been discussed.Finally,the processing and measurement of Ka band substrate integrated waveguide near-field-focused antenna are presented.Based on the previous near-field-focused antenna,the side lobe suppression of the near field focused antenna is further studied.By analyzing the generation principle of the low side lobe and circular polarization in the near field region,the realization method is analyzed.That is,the circular polarization is realized by the multivariate method using the substrate integrated slot antenna,and the required near field side lobe level is achieved by integrated waveguide network with Taylor distribution.The design,fabrication and test results of the Ka band dual circular polarization near-field-focused antenna with low side lobe are presented in the end.Finally,Ka band near-field-focused antenna with multi spot is realized by combining the substrate integrated waveguide modified Rotman lens and the substrate slot antenna array.In order to integrate the Rotman lens as a focused beam forming network,the conventional lens phase shift network is modified to meet the requirements of beam focusing and scanning.When different input ports are excited,the focus can be scanned horizontally.In the end,the design,fabrication and testing results of Ka band substrate integrated focused multi beam antenna based on the modified Rotman lens are presented.