Null‐spot control of magnetic field enabled by manipulating current distribution in metallic loop array

Abstract

Loading a capacitor into a metallic loop allows one to tune the resonance frequency of the induced current on the loop and enhance the current amplitude for the normally incident magnetic field. We show that in an array of variable‐capacitor‐loaded loops, a null spot of the magnetic field generated some distance away can be moved laterally and crossed the array by manipulating current amplitude of each loop via the variable capacitor. We develop an analytic model for expressing the curl of the current source on the loop by using the delta function so that the magnetic field behavior in the vicinity of the array is characterized together with physical insight. Moreover, the control of a null spot is explained by the decomposition of the curl of current sources. The concept of a null‐spot control is crucial for manipulating the kilohertz/megahertz magnetic field. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2891–2895, 2015