Abstract. In this paper, we present a custom-designed nuclear
magnetic resonance (NMR) platform based on a broadband complementary
metal–oxide–semiconductor (CMOS) NMR-on-a-chip transceiver and a synchronous
reference signal generator, which features arbitrary phase control of the
excitation pulse in combination with phase-coherent detection at a non-zero
intermediate frequency (IF). Moreover, the presented direct digital
synthesis (DDS)-based frequency generator enables a digital temperature
compensation scheme similar to classical field locking without the need for
additional hardware. NMR spectroscopy and relaxometry measurements verify
the functionality of the proposed frequency reference and temperature
compensation scheme as well as the overall state-of-the-art performance of
the presented system.


/pdf/a-portable-nmr-platform-with-arbitrary-phase-control-and-2seot427.pdf

A portable NMR platform with arbitrary phase control and temperature compensation

Imaging has long supported our ability to understand the inner life of plants, their development and response to a dynamic environment. While optical microscopy remains the core tool for imaging, a suite of novel technologies is now beginning to make a significant contribution to visualize plant metabolism. The purpose of this review is to provide the scientific community with an overview of current imaging methods, which rely variously on either nuclear magnetic resonance (NMR), mass spectrometry (MS) or infrared (IR) spectroscopy, and to present some examples of their application in order to illustrate their utility. In addition to providing a description of the basic principles underlying these technologies, the review discusses their various advantages and limitations, reveals the current state-of-the-art and suggests their potential application to experimental practice. Finally, a view is presented as to how the technologies will likely develop, how these developments may encourage the formulation of novel experimental strategies, and how the enormous potential of these technologies can contribute to progress in plant science.

Seeing plants as never before.

In this paper, we present a miniaturized NMR relaxometry system for the point-of-care analysis of body liquids, centered on an NMR-on-a-chip transceiver ASIC and a DDS-based reference frequency generator. The NMR ASIC is fabricated in a 0.13-µm SiGe BiCMOS technology. It co-integrates a low-IF receiver, a power amplifier, and a phase-locked loop on a small footprint of 1100 × 900 µm 2 . The presented system provides an excellent low-field concentration sensitivity of ${v_{{\text{c}},\min }} = 5.4{\text{mM}}/\sqrt {{\text{Hz}}} .$ The reference frequency generator provides an output signal with arbitrarily adjustable phase, enabling classical CPMG experiments as well as its modern adaptations. The system also includes an automatic frequency lock to prevent temperature-induced frequency drifts. Proof-of-concept NMR measurements on reference and biomedical samples demonstrate the excellent performance of the presented system as well as its applicability for future point-of-care analysis.

A chip-based NMR relaxometry system for point-of-care analysis

/pdf/unlocking-the-power-of-nanopores-recent-advances-in-29hc4wvf.pdf

Unlocking the Power of Nanopores: Recent Advances in Biosensing Applications and Analog Front-End

In this paper, we present a chip-based C-band ODNP platform centered around an NMR-on-a-chip transceiver and a printed microwave (MW) Alderman-Grant (AG) coil with a broadband tunable frequency range of 528MHz. The printable ODNP probe is optimized for a high input-power-to-magnetic-field conversion-efficiency, achieving a measured ODNP enhancement factor of -151 at microwave power levels of 33.3dBm corresponding to 2.1W. NMR measurements with and without microwave irradiation verify the functionality and the state-of-the-art performance of the proposed ODNP platform. The wide tuning range of the system allows for indirect measurements of the EPR signal of the DNP agent by sweeping the microwave excitation frequency and recording the resulting NMR signal. This feature can, e.g., be used to detect line broadening of the DNP agent. Moreover, we demonstrate experimentally that the wide tuning range of the new ODNP platform can be used to perform multi-tone microwave excitation for further signal enhancement: Using a 10mM TEMPOL solution, we improved the enhancement by a factor of two. 

A chip-based C-band ODNP platform.

NMR magnets for portable applications using 3D printed materials

In this paper, we present a continuous-time current-mode $\Sigma\triangle$ modulator (CT C-SDM) with finite impulse response (FIR) feedback to increase clock jitter robustness while preserving the anti-aliasing filtering (AAF) property of a CT modulator. The modulator also features a newly proposed DC servo loop (DSL) that extends the modulator’s dynamic range in applications with a large DC bias current. This improvement breaks the intrinsic tradeoff between dynamic range and quantization noise floor of C-SDM for applications which require the digitization of AC currents in the presence of strong DC bias currents. The proposed modulator architecture has been manufactured in 180nm CMOS, and consumes 64mW from a 3. 3V supply. The chip’s measured peak SNR and SNDR are 77 dB and 76.8 dB, respectively. The modulator can accommodate AC signal currents up to 137$\mu \mathrm{A}_{\mathrm{p}\mathrm{p}}$ and features an integrated noise of 6.9 n$\mathrm{A}_{\mathrm{r}\mathrm{m}\mathrm{s}}$ over a 200 kHz bandwidth, corresponding to a noise floor of 15 pA/$\sqrt{\mathrm{H}\mathrm{z}}$. An off-chip implementation of the proposed DSL verifies its positive effect on the modulator’s dynamic range (DR) without deteriorating the modulator’s noise performance and/or stability properties.

A current-mode Σ△ modulator with FIR feedback and DC servo loop for an improved dynamic range

In this paper, we present a widely tunable transimpedance amplifier (TIA) with a dc servo loop and an optional bandwidth extension. All resistors are implemented as multielement pseudo-resistors, which feature high linearity, robustness against process and temperature variations, and a very wide tuning range of more than five decades. While state-of-the-art TIAs are mainly implemented with either resistive or capacitive feedback, the proposed TIA uses a capacitive-resistive feedback network to combine the best of both topologies. The TIA features a noise floor of 0.6 fA/✓Hz at its maximum transimpedance of 150 GΩ and a bandwidth of 2.9 MHz at its minimum transimpedance of 440 kΩ. A subsequent inverting amplifier stage provides an optional pole-zero compensation to extend the TIA's overall bandwidth by a factor of up to 180 or with an absolute limit of 2.3 MHz. An additional dc servo loop, which incorporates a tunable integrator and a tunable dc feedback resistor, can be used to prevent large dc currents from flowing through the main signal path. Its dc transimpedance can be adjusted separately from the ac transimpedance, and the crossover frequency is adjustable over a range of more than five decades. The TIA occupies 0.3 mm2 of chip area and has a power consumption of 40 mW from a 1.8-V supply.

A 440-kOhm to 150-GOhm Tunable Transimpedance Amplifier based on Multi-Element Pseudo-Resistors

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Papers

NMR magnets for portable applications using 3D printed materials

A current-mode Σ△ modulator with FIR feedback and DC servo loop for an improved dynamic range

A 440-kOhm to 150-GOhm Tunable Transimpedance Amplifier based on Multi-Element Pseudo-Resistors