Patterning of Subwavelength Magnetic Fields Along a Line by Means of Spatial Spectrum: Design and Implementation

Spatial shaping of magnetic fields at low frequencies has various applications in biophysics such as magnetic drug targeting, magnetic innervation, and hyperthermia. In this letter, for a given arbitrary one-dimensional magnetic pattern, the spatial spectrum is calculated by Fourier series. It is shown that a set of regularly spaced coils realizes a controlled sinusoidal base pattern, that is, a typical spatial mode, along a target line parallel to axis of the coil array. Hence, multimode sets were employed simultaneously to synthesize the fundamental spectra of the desired pattern. In a specific mode, each coil's center and radius are specified by the corresponding spectrum, while the current is proportional to the Fourier coefficients. Every coil set was fabricated on a thin dual-layer printed circuit board and then mounted on each other. An excellent agreement between the analytical solution and experiment results was obtained using the five modes of the spectrum. The proposed setup is simple to realize, electronically reconfigurable, and allows for fast analysis.