28.2 A 14GHz battery-operated point-of-care ESR spectrometer based on a 0.13µm CMOS ASIC

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

“…As a result, the commercially available benchtop ESR spectrometers suffer from a bulky size and weight as well as a large instrument cost, which together prevent many in-field applications for ESR spectroscopy, including e. g. point-of-care ESR spectroscopy. As a potential solution to this problem, in this paper, we will discuss a recently proposed approach [3] towards portable, point-of-care spectroscopy, which at its heart uses voltagecontrolled oscillators (VCOs) as both microwave source to excite the spin ensemble and detect the resulting ESR-induced changes in sample magnetization as a modulation of its oscillation frequency. Moreover, as an extension to the state-ofthe-art in VCO-based ESR sensing, we propose an improved VCO tuning scheme compared to [3], which greatly relaxes the hardware requirements for the overall experimental setup.…”

“…According to the figure, in this setup the sample is contained inside a resonator which in turn is placed inside a large magnetic field to produce the required Zeeman splitting. Then, the ESR experiment is performed by irradiating the sample with a second magnetic field, the socalled B 1 -field, at a fixed frequency, which corresponds to the Larmor frequency ω L of the spins at the resonant field strength, [3] and (c) newly proposed modification of the scheme of (b) to relax the constraints on the DAC producing the sweep and modulation waveforms.…”

“…In contrast, in the VCO-based ESR setup of Fig. 2b, which was recently proposed by our group in [3], the sample is directly placed on top of the tank inductance of an integrated CMOS LC-tank VCO such that the magnetic field generated by the tank inductance produces the resonant magnetic field B 1 , which triggers the ESR transitions. Thereby, the need for a sweepable magnet is removed because the swept-frequency excitation, which is required to operate at a fixed static magnetic field B 0 , can be conveniently produced by a sawtooth waveform applied to the VCO tuning voltage V TUNE .…”

Live demonstration: A VCO-based point-of-care ESR spectrometer

“…In the proposed live demo, we will present an improved version of our portable, battery-operated, point-of-care ESR spectrometer, which was previously presented at ISSCC [2]. At its heart, our system uses a VCO-based ESR detector, which removes many of the abovementioned limitations of conventional ESR setups.…”

“…2 then displays an annotated photograph of the assembled portable spectrometer with detail views of its individual components. As a novelty compare to the system presented in [2], we present a novel VCO tuning scheme, which greatly relaxes the requirements on the digital-to-analog-converter (DAC) driving the VCO tuning ports.…”