Research On Key Technology Of Non-in Vasive Electromagnetic Focusing In Organism

Non-invasive medical methods can reduce pain for patients,and the use of electromagnetic focusing technology can achieve non-invasive medical operations,which has great significance in the field of biomedicine.However,there are some problems and challenges regarding electromagnetic focusing in non-invasive non-uniform media.Firstly,the widely used circular electromagnetic focusing phased array has a high production cost,and it is also difficult to calculate the initial phase of each unit during use.Secondly,using a phased array requires modulating the phase of each antenna in the array,which is more complex to operate.The third reason is that the electromagnetic environment inside the organism is complex,and the electromagnetic properties of the medium are very irregular,which brings considerable trouble to calculate the initial phase of the antenna unit.In order to explore these issues,this paper studied electromagnetic focusing technology,combining knowledge of transmission array theory and phased array theory with time inversion theory.The research mainly includes the following parts:Firstly,most studies tend to use phased arrays with circular or conformal structures to achieve electromagnetic focusing within organisms.In fact,the production method of planar phased arrays is relatively simple and the use process is also more convenient.This paper also compares the electromagnetic focusing effect of planar structured phased arrays with that of annular structured phased arrays.The HPR of annular structured phased arrays is reduced by 20%compared to planar structured phased arrays.This not only demonstrates that the electromagnetic focusing ability of annular structured phased arrays is superior to that of planar structured phased arrays,but also verifies that even using planar structured phased arrays can achieve better electromagnetic focusing effects.Secondly,research at home and abroad mainly uses phased arrays to achieve electromagnetic focusing within organisms,requiring modulation of the initial phase of each antenna in the phased array,which is relatively complex to operate.In fact,the metasurface transmission array can also achieve the focusing of electromagnetic waves at specific positions by modulating their phase.This paper independently designed a three-layer rotating arm ten thousand shaped transmission unit,which has good transmittance and phase adjustment ability at operating frequency.And the transmission unit was also used for array formation,achieving electromagnetic focusing with adjustable target focus.It has been proven that the metasurface transmission array can achieve a certain degree of electromagnetic focusing effect.Finally,due to the complex distribution of media within the organism during actual operation,it will bring huge computational costs to the calculation of the initial phase of each unit.To solve this problem,this paper also combines time inversion algorithm with phased array theory to achieve electromagnetic focusing with smaller computational complexity and better results.In addition,this article focuses on the research of basic theories,deeply analyzing the relevant theories of electromagnetic focusing,and briefly analyzing the basic principles of phased arrays and their impact on the electromagnetic focusing effect.At the same time,the principle of the metasurface transmission array was also explored,and a calculation method was provided for the compensation amount of the phase of each unit.In addition,there is an introduction to the basic theory of time inversion and a brief explanation of the evaluation method of electromagnetic focusing effect.The main innovative points include:A three-layer rotating arm ten thousand shaped transmission unit has been proposed,and electromagnetic focusing based on the transmission metasurface array has been achieved through array formation.The simulation results show that the transmission unit can achieve phase compensation of 340° while meeting the requirement of a transmittance higher than-2dB,and the formation of a transmission metasurface array also achieves electromagnetic focusing.The use of time reversal algorithm optimized the phase calculation method,achieved electromagnetic focusing under non-uniform conditions,and improved the electromagnetic focusing performance of the phased array.The simulation results show that the optimized electromagnetic focusing system reduces the focal deviation by about 28%.