Benedikt Schlecker

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

Thanks to its unique ability to deliver information about the structure, spatial distribution, and even dynamics of paramagnetic species, electron spin resonance (ESR) spectroscopy is one of the most powerful analytical techniques in modern life sciences. Recently, the method has gained significant attention as a tool to study oxidative stress, i.e., a state in which the number of reactive oxygen species (ROS) exceeds the physiological antioxidative potential of the cells, which plays an important role in the development of many chronic diseases as well as acute stress conditions.

Single-Cycle-PLL Detection for Real-Time FM-AFM Applications

In this paper we present a novel architecture for phase-locked loop (PLL) based high-speed demodulation of frequency-modulated (FM) atomic force microscopy (AFM) signals. In our approach, we use single-sideband (SSB) frequency upconversion to translate the AFM signal from the position sensitive detector to a fixed intermediate frequency (IF) of 10 MHz. In this way, we fully benefit from the excellent noise performance of PLL-based FM demodulators still avoiding the intrinsic bandwidth limitation of such systems. In addition, the upconversion to a fixed IF renders the PLL demodulator independent of the cantilevers resonance frequency, allowing the system to work with a large range of cantilever frequencies. To investigate if the additional noise introduced by the SSB upconverter degrades the system noise figure we present a model of the AM-to-FM noise conversion in PLLs incorporating a phase-frequency detector. Using this model, we can predict an upper corner frequency for the demodulation bandwidth above which the converted noise from the single-sideband upconverter becomes the dominant noise source and therefore begins to deteriorate the overall system performance. The approach is validated by both electrical and AFM measurements obtained with a PCB-based prototype implementing the proposed demodulator architecture.

PLL-based high-speed demodulation of FM signals for real-time AFM applications

In this paper we present a new architecture for PLL-based high-speed demodulation of frequency-modulated AFM signals. In our approach, we use single-sideband frequency up-conversion to translate the AFM signal from the position sensitive detector to a fixed intermediate frequency of 10 MHz. In this way, we fully benefit from the excellent noise performance of PLL-based FM demodulators still avoiding the intrinsic bandwidth limitation of such systems. Furthermore, the system becomes independent of the cantilevers resonance frequency. To investigate if the additional noise introduced by the single-sideband upconverter degrades the system noise figure we present a model of the AM-to-FM noise conversion in the PLL phase detector. Using this model, we can predict an upper corner frequency for the demodulation bandwidth above which the converted noise from the single-sideband upconverter becomes the dominant noise source and therefore begins to deteriorate the overall system performance. The approach is validated by measured data obtained with a PCB-based prototype implementing the proposed demodulator architecture.

Novel electronics for high-speed FM-AFM in life science applications

In this paper we present a novel system architecture for high-speed FM-AFM electronics. The proposed system consists of a PLL-based FM demodulator preceded by a SSB modulator and driving electronics ensuring a stable self-oscillation of the cantilever. Thanks to the SSB upconverion preceding the FM-demodulator, the system allows for demodulation bandwidths as large as the cantilever resonance frequency, opening up the way to real-time FM-AFM of biological processes. Electrical measurements of a PCB-based prototype verify the proposed architecture.

Integrated Circuit Technology for Next Generation Point-of-Care Spectroscopy Applications

Point-of-care personalized medicine and home diagnostics are emerging topics that can help to master the challenges of aging societies. Magnetic resonance spectroscopy is one of the most promising sensing principles because it enables the detection of proteins, metabolites, and reactive oxygen species, which play crucial roles in a large number of diseases, with high specificity. To provide a self-contained introduction to the topic, this article starts with a description of the basic working principle of magnetic resonance spectroscopy, highlighting the similarities and differences compared to conventional impedance spectroscopy methods. Focusing on the two specific techniques of NMR and ESR spectroscopy, we explain how miniaturized systems co-integrating detectors and the signal processing electronics on a single chip are a key enabler for portable, low-cost spectrometry systems. These systems bear many similarities to conventional communication transceivers and can therefore largely benefit from recent advances in communication circuits as well as entirely new detection principles such as VCObased detection, which are enabled by the use of modern nanometer-scaled integrated circuit technologies. An overview of the current state of the art of such miniaturized magnetic resonance spectrometers is presented, which both highlights the excellent new possibilities associated with these systems and at the same time outlines the current challenges and future research directions in this emerging field of research.