Sensitivity Enhancement of NMR Spectroscopy Receiving Chain Used in Condensed Matter Physics

Petar Kolar; Mihael S. Grbić; Silvio Hrabar

doi:10.3390/s19143064

Sensitivity Enhancement of NMR Spectroscopy Receiving Chain Used in Condensed Matter Physics

Sensors ◽

10.3390/s19143064 ◽

2019 ◽

Vol 19 (14) ◽

pp. 3064 ◽

Cited By ~ 1

Author(s):

Petar Kolar ◽

Mihael S. Grbić ◽

Silvio Hrabar

Keyword(s):

Nmr Spectroscopy ◽

Noise Figure ◽

Condensed Matter ◽

A Priori ◽

Noise Model ◽

Measurement Time ◽

Condensed Matter Physics ◽

Noise Levels ◽

Proposed Model ◽

Optimized Conditions

Assurance of high measuring sensitivity is one of the most challenging issues for any nuclear magnetic resonance (NMR) spectroscopy system. To this end, we propose an accurate noise model of the entire probe-to-spectrometer receiving chain for condensed matter physics, based on the concept of noise figure. The model predicts the propagation of both the signal and noise levels in every component of the NMR spectroscopy receiving chain. Furthermore, it enables identification of the "weakest" component and, therefore, the optimization of the whole system. The most important property of the proposed model is the possibility to find system parameters that reduce the measurement time by an a priori calculation, rather than an a posteriori approach. The model was tested experimentally on several different samples. It was found that the measurement time can still be significantly shortened, down to at least one half of the measurement time, starting from optimized conditions with commercially available components. Thus, the proposed model can be used as a tool for both quantitative analysis of the noise properties and a sensitivity prediction of practical NMR systems in physics and material science.

Download Full-text

Microwave Analysis for Two-Dimensional C-V and Noise Model of AlGaN/GaN MODFET

Advances in Materials Science and Engineering ◽

10.1155/2014/197937 ◽

2014 ◽

Vol 2014 ◽

pp. 1-12 ◽

Cited By ~ 3

Author(s):

Ramnish Kumar ◽

Sandeep K. Arya ◽

Anil Ahlawat

Keyword(s):

Noise Figure ◽

Noise Model ◽

Gate Length ◽

Two Dimensional ◽

High Frequencies ◽

Noise Characteristics ◽

Proposed Model ◽

Dimensional Electron Gas ◽

High Transconductance ◽

Gate Resistance

A new two-dimensional analytical model for the capacitance-voltage and noise characteristics of a AlGaN/GaN MODFET is developed. The two-dimensional electron gas density is calculated as a function of device dimensions. The model includes the spontaneous and polarization effects. The contribution of various capacitances to the performance of the device is shown. The model further predicts the transconductance, drain conductance, and frequency of operation. A high transconductance of 160 mS/mm and a cut-off frequency of 11.6 GHz are obtained for a device of 50 nm gate length. The effect of gate length on the gate length behaviour of the noise coefficientsP,R, andCis also studied. The effect of parasitic source and gate resistance has also been studied to evaluate the minimum noise figure. The excellent agreement with the previously simulated results confirms the validity of the proposed model to optimize the device performance at high frequencies.

Download Full-text

How (and why) to determine NMR spectrometer’s noise figure?

tm - Technisches Messen ◽

10.1515/teme-2020-0043 ◽

2020 ◽

Vol 87 (10) ◽

pp. 614-621

Author(s):

Petar Kolar ◽

Lovro Blažok ◽

Dario Bojanjac

Keyword(s):

Nmr Spectroscopy ◽

Noise Figure ◽

Block Diagram ◽

Control Level ◽

Gain Control ◽

Noise Model ◽

General Tendency ◽

Lower Response ◽

Vector Network Analyzers ◽

Spectroscopy System

AbstractIn the last decade or two, it seems that the trend of technological advance in NMR spectroscopy cannot follow the trend of desire to measure NMR samples with gradually lower response signals. Recently, an accurate noise model, based on the concept of noise figure, of the most sensitive part of the NMR spectroscopy system from the aspect of noise, which is its probe-to-spectrometer receiving chain, was introduced. The main purpose of this model is to optimize the used NMR spectroscopy system and, ultimately, enable measuring NMR samples with even lower response signals than the ones measured today. All the parameters of the NMR spectroscopy system, used in the introduced model, can be easily measured using vector network analyzers and noise figure meters, or can be found in the datasheets of the respective elements, except the spectrometer’s receiving chain noise figure. In this contribution, the process of spectrometer’s receiving chain noise figure measurement, performed using the Twice Power Method, is described. A block diagram representation of the spectrometer’s receiving chain is presented here, as well as its approximative model. The respective noise figure measurement results, which are also presented, explain the general tendency of using the mid-range of the spectrometer’s gain control level when performing the actual NMR measurements.

Download Full-text

Inelastic scattering at surfaces and interfaces

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100143560 ◽

1986 ◽

Vol 44 ◽

pp. 392-393

Author(s):

R. H. Ritchie ◽

A. Howie

Keyword(s):

Inelastic Scattering ◽

Surface Properties ◽

Correlation Energy ◽

Condensed Matter ◽

Charged Particles ◽

Condensed Matter Physics ◽

Optical Phonons ◽

Exchange Correlation ◽

Surfaces And Interfaces ◽

Inelastic Interactions

An important part of condensed matter physics in recent years has involved detailed study of inelastic interactions between swift electrons and condensed matter surfaces. Here we will review some aspects of such interactions.Surface excitations have long been recognized as dominant in determining the exchange-correlation energy of charged particles outside the surface. Properties of surface and bulk polaritons, plasmons and optical phonons in plane-bounded and spherical systems will be discussed from the viewpoint of semiclassical and quantal dielectric theory. Plasmons at interfaces between dissimilar dielectrics and in superlattice configurations will also be considered.

Download Full-text