Low Power Compact Size Complex Permittivity Sensor for Biomedical Applications in 22nm FDSOI CMOS Technology

This paper presents a compact, low-power, complex permittivity sensor design in 22nm FDSOI CMOS technology. The design allows for measuring both the real and imaginary parts of the permittivity of the material under test that is exposed to the sensor. The sensor is integrated into the resonant tank of an oscillator circuit, where the output results are frequency-dependent oscillator frequency and output power. To convert the frequency information to DC voltage, a frequency discriminator consisting of a RC polyphase filter, a voltage-driven double-balanced passive mixer, and an operational amplifier acting as buffer and active low-pass filter are used. The functionality of the sensor is demonstrated by placing a small piece of fat tissue on top of the resonant tank. The chip has a miniature size and occupies only $0.56\ \text{mm}^{2}$ area. It consumes 6.4 mW of power from a 0.8 V supply which is much lower compared to the state-of-the-art.