VCO-based ESR-on-a-chip as a tool for low-cost, high-sensitivity point-of-care diagnostics

Abstract

In this paper, we discuss the use of electron spin resonance (ESR) spectroscopy as a tool for future point-of-care diagnostic applications. Additionally, we present a new ESR sensor ASIC with an improved VCO tuning scheme as an extension to our previously presented portable, VCO-based ESR spectrometer. By using two VCO tuning voltages with widely different VCO gains, the proposed tuning scheme greatly relaxes the requirements on the digital-to-analog converter (DAC). This is because in the previous scheme a single DAC had to be used to generate both the tuning signals for the wide frequency sweep and the small frequency modulation signals at the same time. In contrast, in the new scheme two DACs with optimized dynamic ranges can be used, reducing the AM-to-FM-conversion noise in the varactor to optimize the overall system sensitivity.