Abstract
In this work, a planar microwave angular displacement sensor featuring concentric and precisely aligned stator and rotor components for accurate angular position measurement is presented. The sensor operates using a dual-band architecture incorporating two concentric loop resonators to enhance angular sensing performance. The structure is realized on two FR-4 printed circuit boards (PCBs), each measuring 40 mm × 40 mm with a thickness of 1.6 mm. The PCBs are arranged such that the conductive layers containing the microstrip patterns face each other, ensuring strong electromagnetic coupling and precise concentric alignment. The rotor consists of a split-ring resonator patterned on the underside of the upper PCB and is placed concentrically within a circular aperture on the top layer. The stator comprises all regions outside the circular apertures on both PCBs. The lower PCB includes a straight microstrip feed line magnetically coupled to a closed-loop primary resonator. The split-ring resonator on the rotor is positioned directly above the primary resonator, facilitating strong mutual coupling. Simulation results indicate resonances at 2.17 GHz and 3.57 GHz, demonstrating dynamic angular sensing capability over a 0° to 90° rotation range. Full-wave electromagnetic simulations reveal absolute angular sensitivities of 0.83 MHz/° and 0.40 MHz/° at the respective resonant frequencies. The findings indicate that the proposed sensor design holds significant potential for industrial applications requiring precise angular displacement measurements.