Single-Variable-Input Active Side Lobe Suppression Method for Synthesized Magnetic Field Focusing Technology and its Optimization

Abstract

In this paper, novel method to calculate current distribution, which enables active side lobe suppression of the magnetic flux density in SMF system, is proposed for the first time. The proposed method calculates the current distribution, which enables further side lobe suppression and keeping the resolution at the same time, by changing the target magnetic flux density distribution with only one varying parameter. The proposed calculation method is very intuitive and timeefficient compared to other calculation method, as it only changes one variable to control the side lobe with one step of matrix multiplication. With the finite element method simulation, it is verified that the proposed method can suppress the side lobe with any target Rx point, when the SMF system has 14 coils with size of 10 cm x 10cm, and the synthesis distance is 30 cm. When the field is synthesized at the center, over 90 % of the side lobe was suppressed for maximum case. An FoM was constructed to optimize the system between the resolution increment and the side lobe suppression, and 79 % of the side lobe was suppressed for optimized case, while keeping the resolution increment ratio below 30 %. In addition, it is verified that the method can be also applied to 2-D SMF systems. The experimental results were in good agreement with the simulated results, when the experimental prototype of same condition with simulation was utilized, including a case in which the magnetic field was focused at Rx point other than center. 1 Index Terms—synthesized magnetic field focusing (SMF), side lobe suppression, magnetic field shaping, magnetic induction tomography (MIT)