K-Band BiCMOS based near-field biomedical dielectric sensor for Detection of fat and calcium in blood

This paper presents a K-band BiCMOS dielectric biomedical sensor for discrimination of fat and calcium in blood. Open ended microstrip line, referred as open-stub, is used as the sensing element and is embedded in a Colpitts oscillator. The impedance seen by the oscillator core at this node is capacitive and varies with the permittivity of the medium on top of the stub. As the resonant frequency of the oscillator scales in accordance with the capacitance of this stub, the permittivity data is translated into output frequency of the oscillator. The sensor chip was fabricated in standard 0.25 μm SiGe:C BiCMOS technology and has a size of 0.6 mm2, while consuming approx. 15 mW power from a 3.3 V supply. First measurements were performed by detecting concentration of water in glucose solution. Following this, varied concentrations of fat and calcium were measured using water and blood as the host material in binary mixture. This sensor is proposed as a building block for non-invasive investigations and plaque characterization.