A 40-nm CMOS Complex Permittivity Sensing Pixel for Material Characterization at Microwave Frequencies

Journal article (2018)

Authors

G. Vlachogiannakis Electronics - EEMCS
M.A.P. Pertijs Electronic Instrumentation - EEMCS
M. Spirito Electronics - EEMCS
L.C.N. de Vreede Electronics - EEMCS
Research Group
Electronics (EEMCS) (TU Delft)
Copyright: © 2018 G. Vlachogiannakis, M.A.P. Pertijs, M. Spirito, L.C.N. de Vreede
DOI: https://doi.org/10.1109/tmtt.2017.2753228
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Published Date

2018

Language

English

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Faculty

Electrical Engineering, Mathematics and Computer Science

Department

Microelectronics

Research Group

Electronics

Abstract

A compact sensing pixel for the determination of the localized complex permittivity at microwave frequencies is proposed. Implemented in the 40-nm CMOS, the architecture comprises a square patch, interfaced to the material-under-test sample, that provides permittivity-dependent admittance. The patch admittance is read out by embedding the patch in a double-balanced, RF-driven Wheatstone bridge. The bridge is cascaded by a linear, low-intermediate frequency switching downconversion mixer, and is driven by a square wave that allows simultaneous characterization of multiple harmonics, thus increasing measurement speed and extending the frequency range of operation. In order to allow complex permittivity measurement, a calibration procedure has been developed for the sensor. Measurement results of liquids show good agreement with theoretical values, and the measured relative permittivity resolution is better than 0.3 over a 0.1-10-GHz range. The proposed implementation features a measurement speed of 1 ms and occupies an active area of 0.15x0.3 mm², allowing for future compact arrays of multiple sensors that facilitate 2-D dielectric imaging based on permittivity contrast.