A firmware-defined digital direct-sampling NMR spectrometer for condensed matter physics

Abstract

We report on the design and implementation of a new digital, broad-band nuclear magnetic resonance (NMR) spectrometer suitable for probing condensed matter. The spectrometer uses direct sampling in both transmission and reception. It relies on a single, commercially-available signal processing device with a user-accessible field-programmable gate array (FPGA). Its functions are defined exclusively by the FPGA firmware and the application software. Besides allowing for fast replication, flexibility, and extensibility, our software-based solution preserves the option to reuse the components for other projects. The device operates up to 400 MHz without, and up to 800 MHz with undersampling, respectively. Digital down-conversion with ±10 MHz passband is provided on the receiver side. The system supports high repetition rates and has virtually no intrinsic dead time. We describe briefly how the spectrometer integrates into the experimental setup and present test data which demonstrates that its performance is competitive with that of conventional designs.

An FPGA-Based Hardware Platform for the Control of Spin-Based Quantum Systems

“…The AWGs which are used to perform superconductor quantum computing generally have a sampling rate ranging from 1 to 2 GSa/s, and an amplitude resolution within 14-16 bit. Similar hardware designed for NMR spectrometers is presented in [24], and a multichannel pulse generator which has a 5-ns resolution is also implemented. The systems based on cold trapped ions and atoms also require multichannel AWGs and pulse generators to control the quantum state, and DDS modules are applied to generate the control signal [18].…”

MRI-Based Image Signal-to-Noise Ratio Enhancement with Different Receiving Gains in K-Space

“…Signal acquisition research has thus far focused on the maximum signal-to-noise ratio (SNR) at individual amplitude points to prevent saturation under a fixed receiving gain (RG). Several researchers have attempted to improve the SNR by reducing the receiver noise [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 ]. When compared with analog receivers, digital receivers can reduce the noise of nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI), thereby improving the SNR [ 1 , 2 , 3 , 4 ].…”

“…Several researchers have attempted to improve the SNR by reducing the receiver noise [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 ]. When compared with analog receivers, digital receivers can reduce the noise of nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI), thereby improving the SNR [ 1 , 2 , 3 , 4 ]. For conventional MRI digital receivers (3T), analog-to-digital convertors (ADCs) with a conversion rate of 100 MHz are typically used for under-sampling and analog-to-digital signal conversion [ 5 ].…”

“…Because the amplitude of the free induction decay (FID) signal of NMR fluctuates greatly in terms of duration, the method for reducing the receiver noise under a fixed RG proposed in the literature [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 ] leverages the entire resolution of an ADC for the part with a larger amplitude in the signal; however, it does not consider the dynamic range of the signal across the entire period during the quantization process. Although measures have been taken to reduce the sampling noise, the parts of the signal with smaller amplitudes still cannot leverage the full resolution of an ADC [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 11 ], meaning that the maximum possible SNR cannot be achieved. In 2011, Takeda et al proposed a solution, namely, Apodization after Receiver Gain Increment during Ongoing Sequence with Time (APRICOT).…”

Note: Commercial SQUID magnetometer-compatible NMR probe and its application for studying a quantum magnet

“…2 Although NMR is often regarded as a specialized technique requiring costly equipment, recent developments including FPGA(Field Programmable Gate Arrays)-based compact spectrometers and radio processors are lowering the barrier in terms of cost and instrument complexity. 3,4 Another source of large cost is a high-homogeneity superconducting magnet. However, for magnetism research with inhomogeneously broadened spectral lines, the high-homogeneity condition can be substantially relaxed.…”