A Wideband Low-Power LC-DCO-Based Complex Dielectric Spectroscopy System in 0.18-mu m CMOS

作者：Elkholy Mohamed^*; Entesari Kamran

来源：IEEE Transactions on Microwave Theory and Techniques, 2017, 65(11): 4461-4474.

DOI：10.1109/TMTT.2017.2691765

• Amplitude-locked loop (ALL)
• biomedical sensors
• chemical sensors
• complex permittivity
• digitally controlled oscillators (DCOs)
• integrating analog-to-digital converter (ADC)
• spectroscopy

A low-power integrated LC-oscillator-based broadband dielectric spectroscopy (BDS) system is presented. The real relative permittivity epsilon(r)' is measured as a shift in the oscillator frequency using an on-chip frequency-to-digital converter. The imaginary relative permittivity epsilon(r)'' increases the losses of the oscillator tank which mandates a higher dc biasing current to preserve the same oscillation amplitude. An amplitude-locked loop is used to fix the amplitude and linearize the relation between the oscillator bias current and epsilon(r)''. The proposed BDS system employs a sensing oscillator and a reference oscillator where correlated double sampling is used to mitigate the impact of flicker noise, temperature variations, and frequency drifts. A prototype is implemented in 0.18-mu m CMOS process with a total chip area of 6.24 mm(2) to operate in 1-6-GHz range using three dual bands LC oscillators. The total power consumption ranges from 10 to 24 mW depending on the operating frequency. The sensor measures complex permittivity within 2% accuracy for the real part epsilon(r)' and 5% for the imaginary part epsilon(r)''. The achieved standard deviation in the air is 2.1 ppm for frequency reading and 110 ppm for current reading.

• 出版日期2017-11