Low-Power Miniature $K$ -Band Sensors for Dielectric Characterization of Biomaterials

Abstract

This paper presents the design and comparison of three $K$ -band sensing oscillators in the standard 0.25- $\mu \text{m}$ SiGe:C BiCMOS technology featuring an open stub, a shunt stub, and a combination of both. The different stub types are combined with the capacitive and/or inductive elements of the particular oscillator and serve as the sensing elements in the respective setup. The input impedances of the stubs depend on the permittivity of the medium. Therefore, the oscillation frequencies and the output power correspond to the dielectric material under test (MUT). The sensor response to different dielectric properties has been investigated using different compositions of methanol-ethanol solutions. In the conducted experiments, the proposed architectures show a maximum frequency shift of 5% (27.8–26.4 GHz) for a change in permittivity of 2.4 (4.1–6.5) of the MUT. Each of three sensors has a chip area of 0.6 mm2 and consumes less than a 12-mW power. The proposed sensor is a potential component for future low-power frontends to perform minimally invasive investigations of biomaterials.