An Integrated Ring-Based Magnetic-Resonance Near-Field Super-Resolution Sensing Model With Effective Second Mode Suppression

Subwavelength aperture imaging exhibits brilliant applications of electromagnetic probing and imaging with super-resolution; however, its response signal intensity is inversely proportional to the near-field resolution. Magnetic resonance inducing subwavelength aperture has been experimentally demonstrated greatly increasing the response signal level with resonance perturbation. Here, we introduced a novel physical model of magnetic resonance perturbation near-field sensing that demonstrates higher near-field resolution as well as the capability of second resonant mode suppression. According to the odd and even mode theory, the current intensity in the middle of the magnetic resonant ring is the maximum for the fundamental mode, and the minimum for the second mode. In the proposed sensing model, the subwavelength sensing region is positioned in the middle of the magnetic resonant ring and connected with vertical vias, with which the fundamental mode and second mode resonances exhibit the strongest and the weakest interaction between the sensing wave and analyte under test, respectively. In this way, the fundamental resonance sensing demonstrates the highest sensitivity, and the second mode is effectively suppressed. A near-field sensor operating around 6 GHz is realized in multilayer printed circuit board (PCB) technology. Experimental results demonstrate that the sensor achieves an extremely high lateral resolution of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$200~\mu $ </tex-math></inline-formula>m (1/250 of operating wavelength), a response distance of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$400~\mu $ </tex-math></inline-formula>m, and effectively suppresses the second mode sensing, thus confirming the validity of the developed sensor prototype.