Single-sided magnetic-field generation based on transformation optics with a multilayer coil structure

We propose a transformation-optics-based method for generating a single-sided time-varying magnetic field. In this method, an inhomogeneous anisotropic medium exhibiting a spatially asymmetric response is constructed and effectively emulated by a distribution of current density, which can independently generate a single-sided time-varying magnetic field. Guided by this approach, we design a single-port-fed multilayer structure consisting of stacked variable-pitch planar spiral coils interconnected in series, eliminating the need for high-permeability materials or Halbach-array-based configurations. A six-layer prototype is fabricated and experimentally characterized at 1 MHz. The measured magnetic flux density on the working side closely matches simulations, while the field on the opposite side is suppressed to near zero, validating the feasibility of the proposed method and demonstrating its potential for active metamaterials with simplified architectures and low magnetic-field leakage, which do not rely on high-permeability magnetic materials.