Amplitude Resolution Research Articles

CALIBRATION OF THE EXTENDED QUADRIHEDRAL NaI(Tl) SPECTROMETER BY COSMIC MUONS

The results of cosmic muon calibration of the extended quadrihedral NaI(Tl) spectrometer are presented. The signal amplitude and energy resolution of the spectrometer in the direction transverse to the spectrometer axis have complex dependences on the photomultiplier voltage and particle entrance point to the spectrometer. At a photomultiplier divider voltage U = 1150 ± 10 V, the region of uniform signals is observed over ~90% of the spectrometer length, the relative energy resolution is δ ≈ 7%.

Dual-Core Photonic Crystal Fiber-Based Plasmonic RI Sensor in the Visible to Near-IR Operating Band

In this paper, a dual-core photonic crystal fiber (DC-PCF) based surface plasmon resonance (SPR) bio-compatible sensor is proposed for various bio-organic molecules and biochemical analytes refractive index (RI) detection in the visible to near-infrared region (0.5 to $2~\mu \text{m}$ ). Two hexagonal ring lattice with all circular air-holes are used to simplify the sensor structure. To make the practical applications feasible, plasmonic material and analyte sensing layer both are employed at the outer surface of the fiber. Noble plasmonic material gold (Au) having a thickness of 30 nm is used to excite the surface plasmons. A thin layer of titanium oxide (TiO2) having a thickness of 5 nm is also considered as an adhesive layer between the Au and silica glass. The sensor response is investigated using the mode solver based finite element method (FEM). Numerical results indicate that the proposed sensor shows a maximum amplitude sensitivity (AS) of 6829 RIU $^{-1}$ , amplitude resolution (AR) of $5\times 10 ^{-6}$ RIU, maximum wavelength sensitivity (WS) of 28,000 nm/RIU, and wavelength resolution (WR) of $3.57\times 10 ^{-6}$ RIU, using the amplitude and wavelength interrogation methods, respectively. Moreover, a maximum figure of merit (FOM) of 2800 RIU $^{-1}$ is obtained, which is the highest among the reported PCF-SPR sensor. Owing to the promising sensitivity and simple structure, the proposed sensor can be potentially applicable for the detection of biochemical solutions and biological samples.

A Fabry–Perot Interferometer-Based Fiber Optic Dynamic Displacement Sensor With an Analog in-Phase/Quadrature Generator

In this paper, the design details of a low-cost and high resolution Fiber Optic Dynamic Displacement sensor are discussed. The sensor is designed based on the principle of extrinsic Fiber Optic Fabry-Perot Interferometer (FPI). Higher sensitivity is achieved by using a double pass sensor head configuration. To resolve direction ambiguity, quadrature signals are generated by employing Phase Generated Carrier (PGC) demodulation technique. An Analog In-phase/Quadrature phase (I/Q) generator is designed to perform light intensity compensation, carrier mixing, and filtering operations to obtain the quadrature signals. Arctangent algorithm and phase unwrapping algorithms are used to obtain dynamic displacement from the quadrature signals. The sensor is demonstrated to measure non-contact dynamic displacement at a working distance of 5 cm with an amplitude resolution of 12 nm, a precision of 1.4 nm, and a standard deviation of 2%. The sensor is also able to measure multi-frequency dynamic displacements generated by piezo actuators. Potential applications of the sensor include condition monitoring and predictive maintenance in industries.

X-Band 6-Bit SiGe BiCMOS Multifunctional Chip With +12 dBm IP1dB and Flat-Gain Response

This brief presents an X-Band 6-bit multifunctional chip, implemented in 0.25- $\mu \text{m}$ SiGe BiCMOS technology. The design achieves +12 dBm of input-referred compression point (IP $_{1dB}$ ) and a flat gain profile, which are critical for the system integration. It consists of a phase shifter (PS), attenuator, and a driver amplifier. The order of the blocks is determined by considering the power handling capability of blocks. The T- and $\Pi $ -type attenuation networks are cascaded to cover 32-dB of range with 0.5 dB steps by favoring reverse-saturated HBTs as bit switches for a lower loss. A vector sum topology realizes the phase control of the multifunctional chip. An interwound transformer and a $2^{nd}$ -order RC poly-phase filter generate I/Q networks with low phase error. The outputs of each 6-bit variable gain amplifiers are summed to obtain the desired phase shift. A cascode amplifier with a series R-C network flattens the gain behavior of the PS and attenuator. The multifunctional chip employs a serial-to-peripheral interface circuit to ease the phase/amplitude control. The measurement results show state-of-the-art performances at X-Band with less than 4°/0.57 dB RMS phase/amplitude errors, respectively. Its insertion loss varies ±0.72 dB over the defined bandwidth. The design achieves a +12 dBm IP1dB while consuming 143.5 mW of power in an area of 3.25 mm2. To the best of authors’ knowledge, the presented work achieves the best amplitude and phase resolution, and the highest linearity performance among similar works in the literature.

Simulations with FADE of the effect of impaired hearing on speech recognition performance cast doubt on the role of spectral resolution

Listeners with hearing impairment show sub-optimal processing of acoustic signals which affects their ability to recognize speech. In this contribution, three effective signal processing deficits are proposed to simulate sensorineural hearing impairment and their effect on simulated speech recognition performance is studied. Psychoacoustic and speech recognition experiments were simulated with the framework for auditory discrimination experiments (FADE). Loss in absolute hearing threshold was modeled as lower level limit, supra-threshold loss in envelope amplitude resolution as multiplicative noise, and reduced spectral resolution was simulated with an increase of the analysis bandwidth. Their effects on the speech recognition performance with the German matrix test in quiet and noise, the audiogram, and tone in (notched) noise detection experiments were systematically examined. The simulations indicate that each psychoacoustic experiment relates to at least one signal processing deficit. This indicates the possibility to determine individual model parameters from the outcome of psychoacoustic experiments. Moreover, absolute hearing thresholds yield the highest effects on simulated speech recognition thresholds, followed by supra-threshold loss in envelope amplitude resolution, and—to a much smaller degree—spectral resolution. A reduced spectral resolution only affected recognition performance in fluctuating masker for normal hearing thresholds, indicating its potential relevance for more complex listening conditions. In contrast to popular interpretations in the literature, the simulations reveal that reduced spectral resolution plays a minor role compared to a reduced envelope amplitude resolution in characterizing supra-threshold hearing loss at least in stationary noise.

Detection of true Gaussian shaped pulses at high count rates

A new true Gaussian digital shaper of detector pulses is analised for applications with soft X-ray spectrometers at the highest count rates. The true Gaussian shaper allows for shaping detector pulses into a symmetrical form which width can be considerably less than the rise time of the input pulses. Therefore, the dead time of the true Gaussian shaper can be noticeably reduced in regards to that of trapezoidal shaper. Less dead time provides a higher count rate of the true Gaussian pulses. The true Gaussian shaper is compared to the standard trapezoidal shaper in terms of count rate, amplitude resolution and biasing the output shaped pulses in a wide range of the input count rates. The maximal output count rate of the true Gaussian shaper has been found to exceed the rate of the trapezoidal shapers in several times. The true Gaussian shaper provides biasing-free measurements of pulse amplitudes with better resolution than that provided by the trapezoidal shapers at high count rates. The tests have been performed by modeling the output signals of silicon drift detector (SDD) H7 VITUS equipped with AXAS-D pre-amplifier developed by KETEK GmbH for measurements of soft X-ray spectra at high count rates.

Upgrade of the SND electromagnetic calorimeter

Current status and last results of the Spherical Neutral Detector (SND) calorimeter upgrade are described. The main part of SND detector is a three-layer spherical NaI(Tl) electromagnetic calorimeter (EMC). The total thickness of NaI(Tl) in the calorimeter is 35 cm. The vacuum phototriodes (VPT) are used as photosensitive devices for the calorimeter counters. The quantum efficiency of VPT is about 15%, the average gain is 10, and the light collection efficiency is about 10%. New spectrometric channel of EMC was designed and implemented. It consists of a NaI(Tl) crystal, a vacuum phototriode, a charge-sensitive preamplifier a shaper and digitizing modules. The digitization is performed by 6 ADCs AD9228BCPZ-40 (4 channel, 12 bits, 40 MBPS) and the data go in serial form to the SoC Xilinx Zynq-7000. This SoC is basically a combination of FPGA programmable logic and ARM processor. The special algorithm for signal waveform processing was developed to determine time of flight and amplitude with high time (1 ns) and amplitude (250 keV) resolution. The algorithm is based on the invariability of the signal waveform. The waveform calibration procedures are developed and implemented. Successful data taking run was performed with upgraded EMC in 2019.

Numerical Study of Circularly Slotted Highly Sensitive Plasmonic Biosensor: A Novel Approach

A highly sensitive Photonic Crystal Fiber (PCF) based Surface Plasmon Resonance (SPR) sensor is demonstrated in this paper in the optimized form of circular slotted lattice (CSL) structure. This proposed model performance is numerically scrutinized by using Finite Element Method (FEM) in presence of Perfectly Matched Layer (PML) and Scattering Boundary Condition. Plasmonic material ‘Gold’ which is chemically inert is used in this structure at the outer surface of the slotted area to mitigate fabrication challenge. This model indicates the highest wavelength sensitivity of 16000 nm/RIU using wavelength interrogation, the amplitude sensitivity of 780 RIU−1 by using amplitude interrogation method and the average spectral sensitivity of 6666 nm/RIU, respectively. Besides, this sensor has the potentiality of detecting analytes within Refractive Index (RI) range 1.4 to 1.46 with maximum wavelength resolution of 6.25 × 10−6 RIU and amplitude resolution of 1.28 × 10−6 RIU, respectively and the maximum figure of merits of 400 RIU−1. Moreover, the variation of structural parameters (such as pitch, plasmon layer thickness etc.) and the impact of these changes are also discussed in details. According to the high sensitivity performance, polynomial fit and high Figure of Merit (FOM), this amend structure can be a strong competitor in the field of biosensing.

Patch-Clamp Analysis of the Mitochondrial H+ Leak in Brown and Beige Fat.

Mitochondria convert the chemical energy of metabolic substrates into adenosine triphosphate (ATP) and heat. Although ATP production has become a focal point of research in bioenergetics, mitochondrial thermogenesis is also crucial for energy metabolism. Mitochondria generate heat due to H+ leak across the inner mitochondrial membrane (IMM) which is mediated by mitochondrial uncoupling proteins. The mitochondrial H+ leak was first identified, and studied for many decades, using mitochondrial respiration technique. Unfortunately, this method measures H+ leak indirectly, and its precision is insufficient for the rigorous insight into the mitochondrial function at the molecular level. Direct patch-clamp recording of H+ leak would have a significantly higher amplitude and time resolution, but application of the patch-clamp technique to a small subcellular organelle such as mitochondria has been challenging. We developed a method that facilitates patch-clamp recording from the whole IMM, enabling the direct measurement of small H+ leak currents via uncoupling proteins and thus, providing a rigorous understanding of the molecular mechanisms involved. In this paper we cover the methodology of measuring the H+ leak in mitochondria of specialized thermogenic tissues brown and beige fat.

Heterodyne interferometry at ultra-high frequencies with frequency-offset-locked semiconductor lasers

Modern broadband telecommunications require microelectromechanical filters which mechanically vibrate at ultra-high frequencies up to several gigahertz. Heterodyne interferometers, so-called laser-Doppler vibrometers (LDVs), provide a sensitive and contactless measurement technique for vibrations in such filters, but are limited in GHz heterodyning by the efficiency drop of acousto-optic frequency shifters. Heterodyning by frequency-offset locking of two lasers in an optoelectronic phase-locked loop (OPLL) overcomes this limitation. This is demonstrated with our LDV setup with heterodyning up to via offset locking of two semiconductor lasers at visible wavelength. The experiments show a vibration-amplitude resolution of less than per for frequencies higher than up to . The bandwidth is only limited by our photodetectors. This amplitude resolution already qualifies our LDV for vibration measurement of microelectromechanical filters at ultra-high frequencies. We present a comprehensive model for the vibration-amplitude resolution of a LDV with this technique including the laser linewidths, the OPLL transfer function, and interferometer delays. The experiments with our LDV validate the model predictions from numerical simulations. Finally, we discuss the collapse of the heterodyne carrier at vanishing mutual coherence due to interferometer delays, the transition to shot-noise-limited detection, and provide design recommendations.

Measurement system with real time data converter for conversion of I2S data stream to UDP protocol data

A central goal of systems neuroscience is to simultaneously measure the activities of all achievable neurons in the brain at millisecond resolution in freely moving animals. This paper describes a protocol converter which is part of a measurement acquisition system for multichannel real time recording of brain signals. In practice, in such techniques, a primary consideration of reliability leads to great necessity towards increasing the sampling rate of these signals while simultaneously increasing the resolution of A/D conversion to 24 bits or even to the unprecedented 32 bits per sample. In fact, this was the guiding principle for our team in the present study. By increasing the temporal and amplitude resolution, it is supposed that we get enabled to discover or recognize and identify new signal components which have previously been masked at a “low” temporal and amplitude resolution, and these new signal components, in the future, are likely to contribute to a deeper understanding of the workings of the brain.

Characterization of a precision modular sinewave generator

At the Czech Metrology Institute (CMI) we have developed a precision modular sinewave generator for impedance ratio bridges. The generator was developed to improve previously available designs regarding amplitude and phase accuracy, linearity, absolute stability, stability of the ratio between two outputs and harmonic distortion. It generates up to 7 Vrms in a frequency range from 1 mHz up to 20 kHz, extendable to 100 kHz with small changes to the filters. The amplitude resolution is better than 0.01 μV V−1 of full scale with an output voltage stability of 0.05 μV V−1/30 min and a stability for the ratio between two outputs of 0.02 × 10−6 over several hours. The generator can be powered from internal batteries and is controlled via optically isolated connections. The internal clock and voltage references can be replaced by external ones, optically coupled in the case of the clock. In this paper, we discuss experimental results obtained with the generator used as a signal source in digital impedance bridges with relative combined uncertainties from 10–5 down to 10–8. The generators have been used in a bridge to drive a quantum Hall resistor in the AC regime. The use of a generator with an AC quantum voltmeter will also be discussed. The generator is not only applicable in the field of AC impedance metrology but also for on-site comparisons of AC quantum voltage standards or, in general, where there is a need for precision voltage sources.

Surface plasmon resonance sensor based on photonic crystal fiber with indium tin oxide film

A novel photonic crystal fiber (PCF) sensor composed of an indium tin oxide (ITO) coating on the outer surface based on surface plasmon resonance (PCF-SPR) is designed and investigated. The sensor consists of eight air holes arranged in a rectangular grid as the cladding, the ITO layer as the plasmonic materials, and an annular external channel. The finite element method (FEM) is used to study the sensing performance and effects of different geometric parameters. The sensor can be operated in the near-infrared region (1380–2260 nm) for the analyte refractive index range between 1.26 and 1.38. In addition, the sensor shows a maximum wavelength sensitivity of 35000 nm/RIU and amplitude sensitivity of 1120.73 RIU−1. It has good wavelength and amplitude resolution reaching 2.86 × 10−6 RIU and 8.92 × 10−6 RIU, respectively and is suitable for accurate sensing applications in biomedicine and chemistry.

Planar cascaded triangular hyperlens structures.

Planar-ports hyperlens structures made of two or four cascaded triangular cuts of planar periodic structures are presented. The hyperlenses are capable of converting electromagnetic evanescent fields to propagating waves, featuring subwavelength resolution and image magnification. One of the two proposed structures features parallel input and output ports. The proposed structures improve the phase and amplitude unbalances, magnification, and resolution of previous planar hyperlenses. Compared to several previous cylindrical hyperlens structures, the proposed structures show competitive or better features. One of the best designs of the proposed structures offers a magnification of 3.86, a resolution of 45 nm, $\lambda /{8}$λ/8 at the free space wavelength of 365 nm, optical modulation, a measure of image contrast of 0.286, and amplitude unbalance, a measure of image quality of 0.08, the smallest among all previous structures. Detailed comparative data of performance are provided. Although the magnification of the proposed planar structures is somewhat smaller than some of the previous cylindrical ones, the performance of the proposed hyperlenses is better or competitive with respect to resolution and image quality.

Electrode-Free Nanopore Sensing by Diffusioptophysiology (DOP)

A wide variety of single molecules can be identified by nanopore sensing. However, all reported nanopore sensing applications result from the same measurement configuration adapted from electrophysiology. Electrophysiology measurements, which provide a superior temporal (∼10 µs) and amplitude resolution (<0.1 pA), satisfy the need of single channel recording based applications but are disadvantageous in the throughput. Though urgently needed in nanopore sequencing and drug screening, simultaneous readout from 1 million channels has not been achieved without a significant sacrifice in the cost or the size of the device.

Soft x-ray tomography measurements in the Wendelstein 7-X stellarator

The soft x-ray tomography diagnostic in the stellarator Wendelstein 7-X consists of twenty pinhole cameras, up–down symmetrically arranged in a poloidal, triangular cross-section of the plasma vessel. The x-ray emissivity is measured with 16 bit amplitude resolution at 2 MHz sampling rate along 360 lines-of-sight by silicon photodiode arrays. In the recent operation campaign data acquisition (DAQ) has been working reliable for the conducted plasma pulse lengths <1 min, however the DAQ system are ready for the foreseen 30 min plasma pulse lengths of upcoming campaigns. The bandwidth of the preamplifiers is ≈200 kHz and the sensitive energy range is approximately 1–12 keV. The measurements indicate the up–down symmetric emissivity distribution in the triangular poloidal cross-section. First tomographic reconstructions of different magnetic field configurations are consistent with the theoretically calculated flux surface topology.

High sensitivity hollow core circular shaped PCF surface plasmonic biosensor employing silver coat: A numerical design and analysis with external sensing approach

This article numerically offers and analyses a hollow core circular shaped photonic crystal fiber-based surface plasmon resonance (CH-PCF-SPR) biosensor. The biosensor sensitivity is analyzed with applying a mode solver built finite element method (FEM) incorporating multi-physics software “COMSOL”. A nano film of silver is coated as sensing layer on the external surface for easy sensing and more practical realization. The biosensor unveils the highest wavelength sensitivity valued 21000 nm/RIU and amplitude sensitivity valued 2456 RIU−1, and corresponding wavelength resolution of 4.76 × 10−6 RIU and amplitude resolution of 4.07 × 10−6 RIU, respectively, using wavelength interrogation technique (WIT) and technique of amplitude interrogation (AIT), in detecting effective refractive index range 1.33 RIU and 1.42 RIU. Besides, the consequence of changing structural parameters like – pitch, diameter of air hole, various plasmonic metals and silver (Ag) layer thickness are also resulted in results section. The sensitivity of the offered sensor is analyzed to examine the means of spectral loss depth, resolution and amplitude sensitivity. In arrears to the modest scheme, highly sensitive and resolution nature, the offered design can be precisely applied in detection of bio molecular analytes

An approach for attenuation-compensating multidimensional constant-Q viscoacoustic reverse time migration

Simulation of wave propagation in a constant-[Formula: see text] viscoacoustic medium is an important problem, for instance, within [Formula: see text]-compensated reverse time migration (RTM). Processes of attenuation and dispersion influence all aspects of seismic wave propagation, degrading the resolution of migrated images. To improve the image resolution, we have developed a new approach for the numerical solution of the viscoacoustic wave equation in the time domain and we developed an associated viscoacoustic RTM ([Formula: see text]-RTM) method. The main feature of the [Formula: see text]-RTM approach is compensation of attenuation effects in seismic images during migration by separation of amplitude attenuation and phase dispersion terms. Because of this separation, we are able to compensate the amplitude loss effect in isolation, the phase dispersion effect in isolation, or both effects concurrently. In the [Formula: see text]-RTM implementation, an attenuation-compensated operator is constructed by reversing the sign of the amplitude attenuation and a regularized viscoacoustic wave equation is invoked to eliminate high-frequency instabilities. The scheme is tested on a layered model and a modified acoustic Marmousi velocity model. We validate and examine the response of this approach by using it within an RTM scheme adjusted to compensate for attenuation. The amplitude loss in the wavefield at the source and receivers due to attenuation can be recovered by applying compensation operators on the measured receiver wavefield. Our 2D and 3D numerical tests focus on the amplitude recovery and resolution of the [Formula: see text]-RTM images as well as the interface locations. Improvements in all three of these features beneath highly attenuative layers are evident.

High performance dual core D-shape PCF-SPR sensor modeling employing gold coat

In this paper, an enhanced performance of dual core D-shape photonic crystal fiber utilizing surface plasmon resonance (DD-PCF-SPR) based sensor is numerically proposed and analyzed. The thickness of gold and pitch parameter are optimized to 30 nm and 1.9 um, respectively, which ensures superior sensor performance. It is revealed; at optimized geometrical parameter, the offered sensor displays a supreme wavelength sensitivity of 8000 nm/RIU, wavelength resolution of 1.25 × 10−5 RIU, a supreme amplitude sensitivity of 700 RIU−1, amplitude resolution 1.7857 × 10−5 RIU and a figure of merit (FoM) of 138 RIU−1 due to the analyte refractive index changing from 1.47 RIU to 1.48 RIU. The identifying features are investigated using modal analysis based finite element method (FEM) incorporating COMSOL commercial software. Finally, a relative review is executed comparing amplitude sensitivity, resolution and wavelength sensitivity of the offered sensor with previously reported sensors. As high sensitivity, simple structure, and tremendous linear polynomial characteristics, the offered sensor will be a talented candidate for the detection of various biochemical and biological samples (DNA, mRNA, proteins, sugar).

Parsimonious Seismic Tomography with Poisson Voronoi Projections: Methodology and Validation

AbstractIll‐posed seismic inverse problems are often solved using Tikhonov‐type regularization, that is, incorporation of damping and smoothing to obtain stable results. This typically results in overly smooth models, poor amplitude resolution, and a difficult choice between plausible models. Recognizing that the average of parameters can be better constrained than individual parameters, we propose a seismic tomography method that stabilizes the inverse problem by projecting the original high‐dimension model space onto random low‐dimension subspaces and then infers the high‐dimensional solution from combinations of such subspaces. The subspaces are formed by functions constant in Poisson Voronoi cells, which can be viewed as the mean of parameters near a certain location. The low‐dimensional problems are better constrained, and image reconstruction of the subspaces does not require explicit regularization. Moreover, the low‐dimension subspaces can be recovered by subsets of the whole dataset, which increases efficiency and offers opportunities to mitigate uneven sampling of the model space. The final (high‐dimension) model is then obtained from the low‐dimension images in different subspaces either by solving another normal equation or simply by averaging the low‐dimension images. Importantly, model uncertainty can be obtained directly from images in different subspaces. Synthetic tests show that our method outperforms conventional methods both in terms of geometry and amplitude recovery. The application to southern California plate boundary region also validates the robustness of our method by imaging geologically consistent features as well as strong along‐strike variations of San Jacinto fault that are not clearly seen using conventional methods.