A Fully Integrated Microplastic Detection SoC with 0.1–3 GHz Bandwidth and 35 dB Dynamic Range for Narrow-Band Notch RF MEMS Sensor System

This paper proposes a fully integrated microplastic (MP) detection system-on-chip (SoC) for RF MEMS sensors with a narrow-band notch point operating in 1.19-1.22 GHz range. This 180-nm CMOS MP detection SoC comprises an LC VCO and an envelope-based readout circuit. The RF MEMS sensor is driven by a high linearity LC VCO, providing an output power of 7.98 dBm at 1.22 GHz, while the LC VCO can maintain near-constant output power levels with small variation of 2.13% between 1.19 GHz and 1.22 GHz. Also, the readout circuit with a high dynamic range (DR) can analyze the resonant frequency shifts of the RF MEMS sensor operating at the range of 0.1-3 GHz. The readout circuit employs a time-based 10-bit current-steering digital-to-analog converter (CS-DAC) with a ramp generation, allowing it to detect the input power as low as -20 dBm while accommodating input power variations with 35 dB DR. The RF MEMS sensor driven by the proposed SoC operates as narrow-band notch filter and resonates at 1.2 GHz depending on MP concentration. When 5 μL of 1% standard polyethylene (PE) dispersion was injected 4, 8, 12 and 16 times, the resonant frequencies were shifted to 0.31 MHz, 0.89 MHz, 1.06 MHz, and 1.17 MHz, respectively.