An inductive linear displacement measurement microsystem realized as a monolithic\nApplication-Specific Integrated Circuit (ASIC) is presented. The system comprises integrated\nmicrotransformers as sensing elements, and analog front-end electronics for signal processing and\ndemodulation, both jointly fabricated in a conventional commercially available four-metal 350-nm\nCMOS process. The key novelty of the presented system is its full integration, straightforward\nfabrication, and ease of application, requiring no external light or magnetic field source. Such\nsystems therefore have the possibility of substituting certain conventional position encoder types.\nThe microtransformers are excited by an AC signal in MHz range. The displacement information\nis modulated into the AC signal by a metal grating scale placed over the microsystem, employing\na differential measurement principle. Homodyne mixing is used for the demodulation of the scale\ndisplacement information, returned by the ASIC as a DC signal in two quadrature channels allowing\nthe determination of linear position of the target scale. The microsystem design, simulations, and\ncharacterization are presented. Various system operating conditions such as frequency, phase, target\nscale material and distance have been experimentally evaluated. The best results have been achieved\nat 4 MHz, demonstrating a linear resolution of 20 �¼m with steel and copper scale, having respective\nsensitivities of 0.71 V/mm and 0.99 V/mm.
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