An Ultrasensitive 14-GHz 1.12-mW EPR Spectrometer in 28-nm CMOS

This work presents an integrated sensing platform for clinical electron paramagnetic resonance (EPR) spectroscopy. The sensor core comprises a LC tank the resonance frequency of which matches the radical Larmor frequency and detects its EPR signal via the change of the tank inductance. To achieve high sensitivity, the inductance variation is measured in a self-mixing interferometric fashion with an on-off modulated RF source to attenuate the noise from the source and the readout circuitry. A sensor prototype was fabricated in 28-nm CMOS. It achieved a spin sensitivity of 6.1\times 10^{\mathrm{ 8}} spins/rtHz with only 1.12-mW power consumption, demonstrating over 10\times improvement in terms of power and sensitivity compared with prior arts of similar system complexity.