A Portable Wideband CMOS NMR Spectrometer for Multinuclear

Abstract

We present a small wideband CMOS nuclear mag- netic resonance (NMR) spectrometer capable of multinuclear molecular fingerprinting (molecular structure determination). The spectrometer combines a small permanent magnet and a wideband digitally assisted CMOS radio frequency (RF) transceiver integrated circuit (IC) that operates in the RF frequency range from 1 to 100 MHz. This small, thus broadly deployable, NMR system can find applications in online, on-site, or on-demand multinuclear molecular fingerprinting. Concretely, the wideband spectrometer performs NMR spectroscopy with nuclear spins from 1H, 19F, and 2H with a spectral resolution down to 0.07 ppm to determine structures of molecules containing these nuclear spins; it can also perform NMR with the nuclear overhauser effect (NOE), which is an important modality that further enhances the capability for molecular fingerprinting (we demonstrate the NOE by reading the 19F NMR signal that is enhanced via heteronuclear magnetization transfer from 1H spins). The wideband operation of the CMOS RF transceiver IC is made possible by integrating a delay-locked loop (DLL) with a broad locking range. The RF receiver (RX) part of the IC achieves an input-referred noise less than 1.2 nV/ √Hz across the entire bandwidth of 1–100 MHz, while the RF transmitter (TX) part employs a digital power amplifier.