Noise Rejection Ratio Research Articles

An improved denoising method for [formula omitted]-OTDR signal based on the combination of temporal local GMCC and ICEEMDAN-WT

A noise reduction method based on the combination of improved complete ensemble empirical mode decomposition with adaptive noise and temporal local generalized maximum cross-correlation entropy and wavelet threshold (ICEEMDAN-TLGMCC-WT) is proposed to improve the noise rejection ratio (NRR) of phase-sensitive optical time-domain reflectometer (φ-OTDR) system signals. Firstly, the principle of the proposed ICEEMDAN-TLGMCC-WT denoising method is introduced. On this basis, experiments are carried out to verify the feasibility of the noise reduction algorithm for non-stationary signals. and the results demonstrate that the vibration event can be detected with an improved average NRR of 72.18 dB and a root mean square error (RMSE) 0.017 within 5 km sensing distance by employing the ICEEMDAN-TLGMCC-WT denoising method, which confirm the effectiveness of proposed scheme for the performance improvement of φ-OTDR system.

Parametric noise reduction and construction of performance degradation indexes for low-voltage switchgear appliances

Aiming at the problem that there is a lot of noise in the feature parameter data of low-voltage switchgear, which makes it difficult to extract useful information about the feature parameters and unable to construct the performance degradation index reasonably. This paper proposes a noise reduction method through Relative Entropy (KL) optimized Variational Mode Decomposition (VMD) combined with Non-Local Mean (NLM) and a method of constructing performance degradation indexes for low-voltage switching appliances through Convolutional Autoencoder (CAE). Firstly, the voltage and current signals are collected based on the full-life test platform of low-voltage switchgear, and the subset of feature parameters is extracted. Then, the feature parameters are decomposed into different components by relative entropy optimization VMD and the noise-dominant and effective components are selected based on the correlation. Secondly, NLM denoising is performed on the noise-dominated signal, and the noise-reduced signals are obtained by signal reconstruction. Finally, the construction of performance degradation indexes for multi-type switchgear is completed based on CAE. The final results show that the two noise reduction evaluation indicators including Noise Rejection Ratio (NRR) and trendiness (T), and the three performance degradation evaluation indexes including Goodness of Fit (R), Root Mean Square Error (RMSE), and Mean Absolute Percentage Error (MAPE) all show optimal results, indicating that this paper’s method can better complete the construction of noise reduction and performance degradation indicators for the feature parameters of low-voltage switchgear.

Reconfigurable Low-Power CMOS Amplifier Stages for Broadband Impedance Spectroscopy

In this paper, a fully differential amplifier is proposed in a 1.8 V-0.18 μm CMOS (Complementary Metal-Oxide-Semiconductor) technology, which can accommodate both voltage (V-mode) and current (C-mode) inputs. Post-layout simulation results show a fixed gain amplifier exhibiting a 26 dB (V-mode)/89 dBΩ (C-mode) gain and a programmable gain amplifier featuring a 6–26 dB gain, overall yielding a 26.8–46.4 dB dB (V-mode)/89.6–109.2 dBΩ (C-mode) programmable gain range, with a 100 MHz bandwidth and a power and area consumption of 360.5 µW and 0.0177 mm2, respectively. This amplifier has been designed considering the constraints and specifications (including low voltage, low power, reduced noise and high common mode rejection ratio) for its use in an analogue Lock-in-based Frequency Response Analyser-Impedance Spectroscopy (FRA-IS) device. The proposed design introduces a novel fully differential open-loop structure based on a transconductance–transimpedance (TC-TI) topology for high performance applications with a broad programmable bandwidth. To compare this work, different figures of merit (FoMs) are introduced as well as a comparison table with other simulated and experimental results, reporting an overall better performance in terms of gain, frequency and power-area consumption.

Development of Through-Substrate via Process for Silicon-Based Monolithic Microwave Integrated Circuits SIS Mixer

We designed and fabricated superconducting monolithic microwave integrated circuits (MMICs) at 2 mm wavelengths. Balanced superconductor-insulator-superconductor (SIS) mixers and silicon membrane-based planar orthomode transducers are incorporated into the MMICs, which is used to develop compact heterodyne array receivers for radio astronomical observations. Because of substrate cavity modes, crosstalk between the outputs of balanced mixers was observed at intermediate frequencies, which deteriorated the noise rejection ratio. Three-dimensional electromagnetic simulation proved that the cavity modes can be effectively suppressed by introducing conducting through-substrate vias (TSVs). We have been developing a TSV fabrication process compatible with that for the superconducting MMICs containing silicon membranes by using non-Bosch deep silicon etching and using sputtered Nb films. The fabricated TSVs were characterized by scanning electron microscopy and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i> – <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</i> measurement.

A Micropower High-Performance ECG Recording Amplifier

This work introduces a novel micropowered single supply low-noise ECG amplifier that can be used with dry fabric-based paste-less electrodes for ambulatory electrocardiogram monitoring. The study emphasizes the need to include realistic values of source impedance as high as 10 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{M}\Omega $ </tex-math></inline-formula> to assess amplifier performance parameters, such as magnitude response, time-domain response, common-mode input impedance, semiconductor noise, and common mode rejection ratio (CMRR). The effect on these parameters associated with high values of electrode impedance at different input frequencies has been extensively demonstrated in this work. The recommendations and standards published by the International Electrotechnical Commission (IEC) 60601 pertaining to electrocardiographic equipment have been used to evaluate the performance requirements of the amplifier to ensure minimal distortion of the ECG signal. The amplifier attains a minimum common-mode input impedance of 10 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{G}\Omega $ </tex-math></inline-formula> at the input within a frequency range of 0.1–150 Hz. This boosted input impedance is preserved by neutralizing amplifier input capacitance using power supply bootstrapping. The amplifier also maintains a differential gain of 41 dB, the CMRR was measured at 84 dB at mains frequency, and the input referred semiconductor noise was measured at 32- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{V}$ </tex-math></inline-formula> peak-to-peak ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula> Vpp) in a bandwidth of 250 Hz. The power consumption of the amplifier was <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$130 ~\mu \text{W}$ </tex-math></inline-formula> operating from 3.7-V lithium battery and is intended to provide for ECG signals having amplitudes in the range 0.1–10 mV. This small portable amplifier is intended for use in long-term ECG and heart-rate monitoring applications.

ESMD-WSST High-Frequency De-Noising Method for Bridge Dynamic Deflection Using GB-SAR

Ground-based synthetic aperture radar (GB-SAR), as a new non-contact measurement technique, has been widely applied to obtain the dynamic deflection of various bridges without corner reflectors. However, it will cause some high-frequency noise in the obtained dynamic deflection with the low signal-to-noise ratio. To solve this problem, this paper proposes an innovative high-frequency de-noising method combining the wavelet synchro-squeezing transform (WSST) method with the extreme point symmetric mode decomposition (ESMD) method. First, the ESMD method is applied to decompose the observed dynamic deflection signal into a series of intrinsic mode functions (IMFs), and the frequency boundary of the original signal autocorrelation is filtered by the mutual information entropy (MIE) for each IMF pair. Second, the high-frequency IMF components are fused into a high-frequency sub-signal. WSST is performed to remove the influence of noise to reconstruct a new sub-signal. Finally, the de-noised bridge dynamic deflection is reconstructed by the new sub-signal, the remaining IMF components, and the residual curve R. For the simulated signal with 5 dB noise, the signal-to-noise ratio (SNR) after noise reduction is increased to 11.13 dB, and the root-mean-square error (RMSE) is reduced to 0.30 mm. For the on-site experiment for the Wanning Bridge, the noise rejection ratio (NRR) is 5.48 dB, and ratio of the variance root (RVR) is 0.05 mm. The results indicate that the proposed ESMD-WSST method can retain more valid information and has a better noise reduction ability than the ESMD, WSST, and EMD-WSST methods.

The Design of a Low Noise, Multi-Channel Recording System for Use in Implanted Peripheral Nerve Interfaces.

In the development of implantable neural interfaces, the recording of signals from the peripheral nerves is a major challenge. Since the interference from outside the body, other biopotentials, and even random noise can be orders of magnitude larger than the neural signals, a filter network to attenuate the noise and interference is necessary. However, these networks may drastically affect the system performance, especially in recording systems with multiple electrode cuffs (MECs), where a higher number of electrodes leads to complicated circuits. This paper introduces formal analyses of the performance of two commonly used filter networks. To achieve a manageable set of design equations, the state equations of the complete system are simplified. The derived equations help the designer in the task of creating an interface network for specific applications. The noise, crosstalk and common-mode rejection ratio (CMRR) of the recording system are computed as a function of electrode impedance, filter component values and amplifier specifications. The effect of electrode mismatches as an inherent part of any multi-electrode system is also discussed, using measured data taken from a MEC implanted in a sheep. The accuracy of these analyses is then verified by simulations of the complete system. The results indicate good agreement between analytic equations and simulations. This work highlights the critical importance of understanding the effect of interface circuits on the performance of neural recording systems.

Low Noise Balanced Homodyne Detector for Quantum Noise Measurement

The research of quantum noise in the interaction of laser and atoms plays a critical role in quantum optical experiments. The measurement of quantum noise is mainly based on the balanced homodyne detection method. Here, we reported a balanced homodyne detector with low noise, high gain, and high common-mode rejection ratio (CMRR) at the wavelength of 795 nm. By optimizing the selection of components and printed circuit board (PCB) layout, a minimum electronic noise of &#x2212;96.7 dBm is obtained. Over the range of 1 MHz to 5 MHz, we get a flat CMRR above 59 dB and a linear gain regime, which can enable a shot noise measurement with the laser power of <inline-formula> <tex-math notation="LaTeX">$100~\mu \text{w}$ </tex-math></inline-formula>. The developed detector can be used in quantum coherent experiments with a weak probe laser of power down to tens of microwatts.

Bioamplificador de Alta Resolución para Electroencefalografía de Amplio Espectro

En este artículo se presenta el desarrollo de la etapa de hardware de un bioamplificador multicanal, de alta resolución y bajo ruido, diseñado para adquirir 8 canales de las señales de biopotencial emitidas por el cerebro humano. Básicamente es un electroencefalógrafo (EEG) de 8 derivaciones, pero diseñado para captar las señales con ancho de banda ampliado, en comparación con los EEG comunes. Este bioamplificador se realiza con el propósito de adquirir señales de sectores específicos del cerebro, para estudiar patrones de frecuencia superiores a los rangos comúnmente analizados en la electroencefalografía convencional. El producto obtenido está formado por 8 circuitos idénticos acoplados para captar todas las señales con respecto a un electrodo central. Cada circuito consiste en un amplificador diferencial con circuitos de realimentación del voltaje en modo común, que permiten mejorar la relación de rechazo al ruido. Se utilizan circuitos de acoplamiento AC de alta eficiencia para reducción del corrimiento de línea de base sin alterar la señal. Cada derivación tiene ganancia de 10000, para obtener niveles de amplitud en el orden de Volts a partir de las señales captadas en el orden de los micro-Volts. Los resultados preliminares muestran que el sistema funciona eficientemente dentro de un rango de 0.5 a 300 Hz, con niveles de error en la medición de amplitud inferiores al 0.14%.

Active Magnetic-Field Stabilization with Atomic Magnetometer.

A magnetically-quiet environment is important for detecting faint magnetic-field signals or nonmagnetic spin-dependent interactions. Passive magnetic shielding using layers of large magnetic-permeability materials is widely used to reduce the magnetic-field noise. The magnetic-field noise can also be actively monitored with magnetometers and then compensated, acting as a complementary method to the passive shielding. We present here a general model to quantitatively depict and optimize the performance of active magnetic-field stabilization and experimentally verify our model using optically-pumped atomic magnetometers. We experimentally demonstrate a magnetic-field noise rejection ratio of larger than ∼800 at low frequencies and an environment with a magnetic-field noise floor of ∼40 in unshielded Earth’s field. The proposed model provides a general guidance on analyzing and improving the performance of active magnetic-field stabilization with magnetometers. This work offers the possibility of sensitive detections of magnetic-field signals in a variety of unshielded natural environments.

Experimental Study of a Planar-Integrated Dual-Polarization Balanced SIS Mixer

A dual-polarization balanced superconductor–insulator–superconductor mixer operating at $\text{2}\text{ mm}$ wavelength is realized in the form of a monolithic planar integrated circuit. Planar orthomode transducers and local oscillator (LO) couplers are enabled by using silicon membranes that are locally formed on the silicon-on-insulator substrate. The performance of the balanced mixer is experimentally investigated. Over the entire RF band ( $\text{125}\text{--}\text{163}\,\text{GHz}$ ), the balanced mixer shows an LO noise rejection ratio of about $\text{15}\,\text{dB}$ , an overall receiver noise about $\text{40}\,\text{K}$ , and a cross polarization $ . The demonstrated compactness and the performance of the integrated circuit indicate that this approach is feasible in developing heterodyne focal plane arrays.

Direct Measurement of High-Gain and Complementary Charge-Steering Amplifiers

This brief presents direct measurement of two novel dynamic amplifiers utilizing the “charge-steering” topology. Employing a delayed clocking scheme, a four-stage charge-steering amplifier achieves the highest gain of any reported charge-steering topology. A complementary charge-steering amplifier exploits both charging and discharging cycles to double the throughput while reducing power consumption by 22%. Fabricated in 180-nm technology, this brief presents, for the first time, direct measurement results of charge-steering amplifiers, including gain, noise, linearity, common-mode response, and power supply rejection ratio.

Partial Discharge Feature Extraction Based on Ensemble Empirical Mode Decomposition and Sample Entropy

Partial Discharge (PD) pattern recognition plays an important part in electrical equipment fault diagnosis and maintenance. Feature extraction could greatly affect recognition results. Traditional PD feature extraction methods suffer from high-dimension calculation and signal attenuation. In this study, a novel feature extraction method based on Ensemble Empirical Mode Decomposition (EEMD) and Sample Entropy (SamEn) is proposed. In order to reduce the influence of noise, a wavelet method is applied to PD de-noising. Noise Rejection Ratio (NRR) and Mean Square Error (MSE) are adopted as the de-noising indexes. With EEMD, the de-noised signal is decomposed into a finite number of Intrinsic Mode Functions (IMFs). The IMFs, which contain the dominant information of PD, are selected using a correlation coefficient method. From that, the SamEn of selected IMFs are extracted as PD features. Finally, a Relevance Vector Machine (RVM) is utilized for pattern recognition using the features extracted. Experimental results demonstrate that the proposed method combines excellent properties of both EEMD and SamEn. The recognition results are encouraging with satisfactory accuracy.

Performance Enhancement of Quench Detection System for the KSTAR Superconducting Pulse Coils

Since the first plasma was achieved in 2008, the quench detection system for the Korea Superconducting Advanced Tokamak Research (KSTAR) coils has been successfully operated. Simple bridge circuits and cowound voltage sensors were used for the first quench detectors. In order to enhance the reliability and stability of the quench detection especially for the pulse coils such as the KSTAR CS coil, a couple of schemes to actively reject inductive voltages have been added and tested. They have focused on rejecting as much inductive voltages as possible and increasing the noise rejection ratio (NRR) because the inductive voltage noise is a main factor to disturb the stable quench detection. One scheme is to use the voltage difference between two balanced bridge voltages or two voltages of cowound voltage sensors, where each voltage is the voltage across each of two coils having the same electrical currents and structurally symmetry. The other is to use the voltage difference between the measured voltage and the calculated voltage. With the additional schemes, inductive voltages were reduced so that the NRR could substantially increase up to 20 000. In this paper, the upgraded quench detection system was described for the KSTAR PF1 coil and the performance results were presented together with experimental data in the 2016 KSTAR campaign.

Polarizers, optical bridges, and Sagnac interferometers for nanoradian polarization rotation measurements.

The ability to measure nanoradian polarization rotations, θF, in the photon shot noise limit is investigated for partially crossed polarizers (PCP), a static Sagnac interferometer, and an optical bridge, each of which can in principle be used in this limit with near equivalent figures-of-merit (FOM). In practice a bridge to PCP/Sagnac source noise rejection ratio of 1/4θF2 enables the bridge to operate in the photon shot noise limit even at high light intensities. The superior performance of the bridge is illustrated via the measurement of a 3 nrad rotation arising from an axial magnetic field of 0.9 nT applied to a terbium gallium garnet. While the Sagnac is functionally equivalent to the PCP in terms of the FOM, unlike the PCP it is able to discriminate between rotations with different time (T) and parity (P) symmetries. The Sagnac geometry implemented here is similar to that used elsewhere to detect non-reciprocal (T¯P) rotations like those due to the Faraday effect. Using a Jones' matrix approach, novel Sagnac geometries uniquely sensitive to non-reciprocal TP¯ (e.g. magneto-electric or magneto-chiral) rotations, as well as to reciprocal rotations (e.g. due to linear birefringence, TP, or to chirality, TP¯) are proposed.

Low-noise integrated balanced SIS mixer for 787–950 GHz

We developed a low-noise, compact, balanced superconductor–insulator–superconductor (SIS) mixer, operating in the 787–950 GHz radio frequency range. A waveguide mixer block was designed to integrate all the key components, such as a radio frequency (RF) 90° hybrid coupler, two identical SIS mixer chips, bias-tees, and an intermediate frequency power-combiner. The RF waveguide 90° hybrid coupler consists of branch lines with wide slots optimized by numerical simulation, for ease of fabrication. The balanced mixer was installed into a cartridge type receiver, originally developed for the Atacama Large Millimeter/submillimeter Array Band 10 (787–950 GHz). The receiver demonstrated double sideband noise temperatures of approximately 200 K for most of the band, without any correction for loss in front of the receiver. The local oscillator noise rejection ratio was estimated to be more than 15 dB within the measured frequency range.

Characterization of a simultaneous dual-species atom interferometer for a quantum test of the weak equivalence principle

We present here the performance of a simultaneous dual-species matter-wave accelerometer for measuring the differential acceleration between two different atomic species ($^{87}$Rb and $^{85}$Rb). We study the expression and the extraction of the differential phase from the interferometer output. The differential accelerometer reaches a short-term sensitivity of $1.23\times10^{-7}g/\sqrt{Hz}$ limited by the detection noise and a resolution of $2\times10^{-9}g$ after 11000 s, the highest reported thus far with a dual-species atom interferometer to our knowledge. Thanks to the simultaneous measurement, such resolution levels can still be achieved even with vibration levels up to $3\times10^{-3}g$, corresponding to a common-mode vibration noise rejection ratio of 94 dB (rejection factor of 50 000). These results prove the ability of such atom sensors for realizing a quantum based test of the weak equivalence principle (WEP) at a level of $\eta\sim10^{-9}$ even with high vibration levels and a compact sensor.

Proportional-scanning-phase method to suppress the vibrational noise in nonisotope dual-atom-interferometer-based weak-equivalence-principle-test experiments

Vibrational noise is one of the most important noises that limits the performance of the nonisotopes atom-interferometers (AIs) -based weak-equivalence-principle (WEP) -test experiment. By analyzing the vibration-induced phases, we find that, although the induced phases are not completely common, their ratio is always a constant at every experimental data point, which is not fully utilized in the traditional elliptic curve-fitting method. From this point, we propose a strategy that can greatly suppress the vibration-induced phase noise by stabilizing the Raman laser frequencies at high precision and controlling the scanning-phase ratio. The noise rejection ratio can be as high as ${10}^{15}$ with arbitrary dual-species AIs. Our method provides a Lissajous curve, and the shape of the curve indicates the breakdown of the weak-equivalence-principle signal. Then we manage to derive an estimator for the differential phase of the Lissajous curve. This strategy could be helpful in extending the candidates of atomic species for high-precision AIs-based WEP-test experiments.

Analysis of single photon detector based on the reflection of coaxial cables

In this paper are analyzed the characteristics of the single photon detector (SPD) with using coaxial cables as reflection lines to cancel transient spikes noises, particularly,the characteristics of variations in bias voltage of the avalanche photodiode (APD) and output signal. Based on the theoretical analyses,the principle of the timing relation between single photon pulses and the two gate pluses is discussed. Also, the condition and the effect of transient spikes cancellation are achieved. And the minimal detecting period is obtained. Finally,we conduct some experiments to verify our theory. In our experiment,the noise rejection ratio is 25.1dB. The results accord with our theory satisfactorily. Our results will be helpful in designing and optimizing single photon detectors.

New Curvature-Compensation Technique for CMOS Bandgap Reference With Sub-1-V Operation

A new sub-1-V curvature-compensated CMOS bandgap reference, which utilizes the temperature-dependent currents generated from the parasitic n-p-n and p-n-p bipolar junction transistor devices in the CMOS process, is presented. The new proposed sub-1-V curvature-compensated CMOS bandgap reference has been successfully verified in a standard 0.25-mum CMOS process. The experimental results have confirmed that, with the minimum supply voltage of 0.9 V, the output reference voltage at 536 mV has a temperature coefficient of 19.5 ppm/degC from 0 degC to 100 degC. With a 0.9-V supply voltage, the measured power noise rejection ratio is -25.5 dB at 10 kHz