Abstract
There are mainly three issues for Near-Field Focusing (NFF) using an antenna array. First, it is required to know the distribution of the near electric field in 3D space for each antenna element. In general, a huge amount of data is required to express the near-field for each antenna element in a 3D space with high resolution. Second, in the trade-off relationship between efficiency and accuracy for NFF, we require to solve the optimization problem in which energy can be concentrated to the focal point. Solving optimization problems with near-field represented by huge amounts of data is very inefficient. Third, accurate NFF must be performed by reflecting the mutual coupling phenomenon between antennas. In this paper, there are three key ideas to overcome the issues in the NFF by improving both accuracy and efficiency. The first is the extraction of the infinitesimal dipole model (IDM) using the active element pattern. This makes it possible to obtain a mathematical model of the antenna that perfectly reflects the mutual coupling effect. The second is the acquisition of near-field data to an adaptive resolution grid with appropriate resolution using the extracted IDM. This re-radiated near-field data has both accuracy and efficiency by maintaining high resolution only for a focal point. The third is an efficient optimization method for a desired focal area with an arbitrary elliptical shape using convex optimization. Through simulations for the verification, 4 types of grids with various resolutions are used to the same NFF problem. The computational time of the proposed method in optimization for the NFF could be reduced to 8% with a similar focal shift compared to a type of the finest resolution. In addition, the accuracy of the electromagnetic analysis of the proposed method was verified through comparative verification with the MoM results.
Highlights
Near-field focusing (NFF) antennas have been actively applied to various fields [1]
In this paper, the three issues of near-field focusing (NFF) mentioned above are clearly resolved through the proposed NFF technique
The problem of data acquisition of the near-field mentioned as the first problem was clearly solved in the form of using an infinitesimal dipole model (IDM)
Summary
Near-field focusing (NFF) antennas have been actively applied to various fields [1]. The near-field pattern can be controlled by adjusting the excitation coefficients (amplitudes and phases) in order to make the electromagnetic (EM) fields of the antenna elements be constructive each other at a specific position called ‘focal point’, the near-field can be regarded as ‘focused’ Diverse optimization algorithms such as the phase conjugate [6], [19]–[22], least square method [23], compressive sensing [24], [25], and convex optimization [25]–[27] have been verified that can be used to synthesize near-field for the various cases as well as far-field synthesis problems. There is no limit in the resolution of near-field data, and we can apply the adaptive resolution in dealing with the near-field data which has more dense observation points near the focal point It can maximize the optimization efficiency with maintaining the high accuracy of the proposed NFF approach.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
