Weak Detection Research Articles

Time-frequency high-resolution for weak signal detection using chaotic intermittence

BackgroundA non-linear Liènard-type system based on trigonometric functions is designed and used as a highly sensitive signal detector. Based on the intermittence mechanism presented in some chaotic systems, an adaptive detection array built by five chaotic oscillators is fully tuned and tested. In the array, each oscillator identifies changes in frequency for non-stationary weak signals and gives an estimate of the timing at which intermittence occurred, allowing the representation of a time-frequency spectrogram even when high-level noise is present. MethodsThis work shows that the trigonometric-based system has an asymptotically stable limit cycle centered at the origin through two methods: first under the fixed-point analysis and later by the Melnikov method, which uses a family of periodic orbits. Once the limit cycle is assured, through an iterative method for searching and tuning parameters, the system is configured to drive itself into the route to chaos named intermittence. Then, the new system can be used as a non-stationary signal detector that simultaneously provides high-resolution time-frequency representation. ResultsComputer experiments showed that our trigonometric oscillator when working in the chaotic intermittence regime and configured as an adaptive array, overcomes the SNR threshold present in other second-order non-linear oscillators such as Duffing, Van der Pol, and Van der Pol-Duffing, achieving high detection rates under noisy conditions, and maintaining a relative error of around 1% with -35 dB SNR. ConclusionsOur oscillator provides better sensitivity to small signals as well as noise rejection, in comparison with traditional oscillators. Furthermore, our entire system formed by a Liènard-type five-oscillator array promises to detect low-power signals and their TF reconstruction with a minimum error.

Weak Fault Diagnosis Method of Rolling Bearings Based on Variational Mode Decomposition and a Double-Coupled Duffing Oscillator

Aiming at the problems of the low detection accuracy and difficult identification of the early weak fault signals of rolling bearings, this paper proposes a method for detecting the early weak fault signals of rolling bearings based on a double-coupled Duffing system and VMD. The influence rule of system initial value on the response characteristics of a double-coupled Duffing system is studied, and the basis for its determination is given. The frequency of the built-in power of the system is normalized, and a variance evaluation standard for the output value of the double-coupled Duffing system for weak fault signals detection is established. In order to solve the interference problem of fault monitoring signals, VMD is proposed to pre-process the fault monitoring signals. The weak fault signal detection method proposed in this paper is tested and verified by simulation signals and rolling bearing fault signals. The results show that the method proposed in this paper can detect the weak fault signal with the lowest signal-to-noise ratio reduced by 2.96 dB compared with the traditional Duffing detection system, and it can accurately detect the early weak fault signal of rolling bearings.

High-Performance Solar-Blind p-NiO/n-ZnO/p-Si Ultraviolet Heterojunction Bipolar Phototransistors With High Optical Gain

Ultraviolet (UV) photodetectors (PDs) have attracted significant attention for civil and military applications. Zinc-oxide (ZnO) and nickel-oxide (NiO) have been widely applied in UV-PDs owing to their wide bandgap (3.2–3.8 eV), transparency, excellent optical and electrical properties, and good chemical stability. However, UV signals are generally weak; hence, UV-PDs with high optical gain are essential. In this work, high-performance solar-blind p-NiO/n-ZnO/p-Si heterojunction bipolar phototransistors (HBPTs) were fabricated. The fabricated HBPTs exhibited a high responsivity of 9.4 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> A/W at a wavelength of 280 nm with <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V_CE</i> = –7 V, a high optical gain of 3.96 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> , and a large detectivity of 3 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">13</sup> Jones. In addition, the UV/visible rejection ratio was as high as 880. These behaviors indicate that the prepared HBPTs are good solar-blind photodetectors and suitable for the detection of weak UV signals. However, for <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V_CE</i> value below –7 V, (| <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V_CE</i> | > 7V), the optical gain decreased owing to the punch-through effect. Furthermore, band-diagrams showed that the photogenerated electrons were blocked by the potential barrier at the NiO/ZnO interface (base–emitter junction) owing to a large conduction-band discontinuity (Δ <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E_C</i> ) of 2.7 eV, which resulted in a large optical gain in the prepared HBPTs.

An Ultra-Fast Temporal Talbot Array Illuminator

We propose an all-optical temporal Talbot array illuminator (T-TAI) enabling denoising passive amplification of broadband ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$&gt;$</tex-math></inline-formula> 10 GHz- bandwidth) optical signals. The key element is an ultra-fast temporal phase grating based on cross-phase modulation. Whereas previous implementations of the T-TAI suffer from the bandwidth limitations inherent to electro-optic systems, the all-optical nature of the proposed approach allows to simultaneously realize high amplification factors and sampling rates, which in turn allows for the efficient processing of broadband signals. In our experiments, we demonstrate a (signal bandwidth) × (amplification factor) product exceeding 370 GHz, more than an order of magnitude improvement as compared with previous electro-optic implementations. We show the prospects of the proposed approach through the recovery of noisy high-speed optical waveforms, namely a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\sim$</tex-math></inline-formula> 10 Gbps data signal buried in a much stronger noise background. Additionally, we experimentally demonstrate that the T-TAI samples preserve the full complex information (amplitude and phase) of the incoming signal. The proposed approach should prove useful in multiple fields requiring the detection of weak and noisy broadband signals as well as for other related applications, such as photonics-assisted analog-to-digital conversion.

Building Hyper-Awareness: How to Amplify Weak External Signals for Improved Strategic Agility

Early detection of weak external signals is increasingly critical for strategic agility. While many organizations scan for weak signals, most dismiss them as anomalies, principally due to poor amplification strategies. Several challenges hinder the necessary amplification and sensemaking of weak signals for organizational awareness. This article analyzes 139 proof-of-concept projects with startups and 15 interviews with executives involved in the projects at a leading German mobility corporation, and it reveals four actions to amplify weak external signals, thereby enhancing organizational hyper-awareness. It illustrates the actions with examples and presents the implications for both weak signals and strategic agility management.

Weak signal detection and adaptive synchronous stability of a novel fifth-order memristive circuit system

Weak signal detection and adaptive synchronous stability of a novel fifth-order memristive circuit system

Preface

The 2023 6th International Conference on Mechanical, Electrical, and Material Applications (MEMA 2023) was successfully held in Changsha, China from February 24th to 26th, 2023 (virtual event). This Seminar was the sixth in a series of topical meetings, and the MEMA series of conferences have come to all successful conclusions in Xi’an, Chongqing, and Chengdu from 2018 to 2022. MEMA 2023 was attended by about 150 participants from different countries.For this fourth meeting we chose Changsha to be our Conference Venue and met with our old and new friends again. While the location of the Conference has been changed sometimes, what remained invariant is the aim of these meetings, which is to discuss recent advances and key challenges and explore new perspectives and research directions facing the development of mechanical, electrical, and material applications in a pleasant and friendly atmosphere. At this meeting we had a comprehensive overview of this fascinating field and of future scenarios thanks to the participation of leaders of the most important projects.The Conference presented an outstanding program of papers covering the most recent advances in mechanical, electrical, and material applications, including Mechanical Dynamics, Precision Machinery, Electromagnetic Compatibility, High Voltage and Insulation Technology, Circuits and Systems, Functional Materials, etc.. The papers in this Proceedings published by Journal of Physics: Conference Series-IOP Publishing represent a collection of the invited talks and academic contributions.The Conference Program consisted of four invited speeches presented in the plenary sessions, including four hot topic speeches highlighting the most recent advances in the field, and various oral presentations. The program included a speech by Dejie Yu who is Member of the Standing Committee of the Hunan Provincial CPPCC and Professor in the College of Mechanical & Vehicle Engineering of Hunan University, a speech title with “Research on Weak Fault Signal Detection Method Based on Gradient Acoustic Metamaterials”. Aiming at the problem that weak signal is difficult to detect, an enhanced detection method based on gradient index acoustic metamaterial was proposed. And still a fault signal enhancement detection method based on gradient index acoustic metamaterial was proposed.We would like to thank the participants, especially those who contributed speeches, posters and manuscripts, for making MEMA 2023 such an exciting and memorable conference. We thank the Technical Program Committee for putting together an outstanding Program. Finally, we thank the Local Organizing Committee for their tireless and expert efforts in the organization of MEMA 2023, and all of our colleagues whose friendly and efficient service contributed much to the success of the Conference.The Committee of MEMA 2023List of Committee Member is available in the pdf

Automated weak signal detection and prediction using keyword network clustering and graph convolutional network

Weak signals are rarely identified in the initial stage of growth and appear significant over time, unlike strong signals clearly observed in past trends. Weak signals are important cues that need to be analyzed to rapidly and accurately predict changes in the uncertain future. Researchers have developed various methods for identifying cues that can be significantly used for prediction. However, in many cases, they heavily depend on the opinions of experts or are applicable only to weak signals in specific fields. This study proposes a weak signal detection method that extracts weak signals by selecting significant keywords from literature database and grouping relevant keywords. Furthermore, this study presents a weak signal prediction method for predicting the growth of specific weak signals by investigating and learning the growth of the extracted weak signals over 10 years. To verify the proposed method, we extracted weak signals for 10 years (2001–2010) from SCOPUS publication data from 1996 to 2009 and applied machine learning using a graph convolutional network (GCN) model with the growth data of the extracted weak signals. The results showed that the proposed methods can effectively detect and predict weak signals.

Sb-Based Low-Noise Avalanche Photodiodes

Accurate detection of weak optical signals is a key function for a wide range of applications. A key performance parameter is the receiver signal-to-noise ratio, which depends on the noise of the photodetector and the following electrical circuitry. The circuit noise is typically larger than the noise of photodetectors that do not have internal gain. As a result, a detector that provides signal gain can achieve higher sensitivity. This is accomplished by increasing the photodetector gain until the noise associated with the gain mechanism is comparable to that of the output electrical circuit. For avalanche photodiodes (APDs), the noise that arises from the gain mechanism, impact ionization, increases with gain and depends on the material from which the APD is fabricated. Si APDs have established the state-of-the-art for low-noise gain for the past five decades. Recently, APDs fabricated from two Sb-based III-V compound quaternary materials, AlxIn1-xAsySb1-y and AlxGa1-xAsySb1-y, have achieved noise characteristics comparable to those of Si APDs with the added benefit that they can operate in the short-wave infrared (SWIR) and extended SWIR spectral regions. This paper describes the materials and device characteristics of these APDs and their performance in different spectral regions.

Application of single photon counter module in weak signal detection for RF chip scanning using a quantum near field probe

AbstractDiamond based quantum sensing for on‐chip electromagnetic field imaging is an emerging field. While smaller diamond probes offer higher spatial resolution, their lower fluorescence intensity poses a challenge for the traditional Avalanche Photo Diode. In this work, we propose a tapered fiber diamond probe containing Nitrogen‐vacancy center and utilize a single photon counter module as the detector. A time domain differential pulse sequence is introduced to suppress noise caused by laser intensity fluctuation. By analyzing the relationship between the signal‐to‐noise ratio (SNR) and parameters of differential pulse sequence, we derived the formula of SNR and the basic cycle (), and obtained the optimal SNR in the same measurement time through trade‐off between two different kinds of noise. The technique was applied to a waveguide microstrip filter chip, accurately imaging the current density distribution. Our results have potential applications in on‐chip testing and failure analysis.

Ultrasensitive Modulated Magnetoelectric Sensors and Low-Noise Readout Circuits for DC and Very Low-Frequency Weak Magnetic Signal Detection

Ultrasensitive Modulated Magnetoelectric Sensors and Low-Noise Readout Circuits for DC and Very Low-Frequency Weak Magnetic Signal Detection

Guest Editorial: Polymer electrets and ferroelectrets

Guest Editorial: Polymer electrets and ferroelectrets

Research on feature extraction method of spindle vibration detection of weak signals for rapier loom fault diagnosis in strong noise background

Fault diagnosis of rapier loom is an inevitable requirement to meet the demand of intelligent manufacturing. Facing the strong noise interference caused by complex working environment, accurate and reliable vibration signal detection of blade loom spindle is the key to realize the rapier loom fault diagnosis. This paper proposes a method to extract the spindle vibration signal of the rapier loom by Adaptive Piecewise Hybrid Stochastic Resonance (APHSR) after the Improved Complete Ensemble Empirical Mode Decomposition with Adaptive Noise (ICEEMDAN). Firstly, ICEEMDAN is used to pre-process the weak vibration signal containing noise, decompose the signal into multiple IMF components and display the high and low frequency signal characteristics of the original signal. Then, the energy density method and the correlation coefficient method are used to remove high and low noise, respectively, to filter the optimal IMF components, and then the signal containing valid information is reconstructed. Finally, the reconstructed signal is input to APHSR for noise-assisted enhancement after scale transformation to restore the faint vibration signal feature frequencies and achieve effective feature extraction. Through the simulation experiment and the engineering fault experiment analysis, comparing ICEEMDAN-APHSR with CEEMDAN-SR, ICEEMDAN-SR, CEEMDAN-APHSR methods. The difference between the spectrum amplitude, the spectrum amplitude and the maximum noise and the maximum signal to noise ratio (SNR) of the fault feature frequency of the rapier loom spindle bearing increased by 3.3668 dB,1.7205 dB,2.3952 dB, respectively. The results show that ICEEMDAN-APHSR method can accurately extract the fault feature frequency of the spindle bearing of rapier loom, and effectively solves the problem of extracting the weak vibration signal feature of rapier loom in the background of strong noise. This method is beneficial to the future research of rapier loom fault diagnosis, and is of great significance to promote the maintenance of loom equipment and production safety and quality.

Low-Voltage Operated High DC Gain Amplification Stage Based on Large-Area Manufacturable Amorphous Oxide Semiconductor Thin-Film Transistor

The industry-standard amorphous metal–oxide–semiconductor (AOS) thin-film transistor (TFT) technology is demonstrated for making low-voltage high intrinsic gain devices. It is revealed by the technology computer-aided design (TCAD) simulation that, without need of making Schottky barrier contacts, large output resistance and high intrinsic gain can be achieved in a subthreshold regime for AOS TFTs. It is further proved by the measurement results with the fabricated AOS TFT from a Gen-4.5 manufacturing line. A simple single-stage zero- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit{V}_{\text{GS}}$</tex-math> </inline-formula> load amplifier is implemented as a proof of concept, achieving a voltage gain larger than 50 for weak signal detection at a supply voltage of 5 V.

An adaptive stochastic resonance detection method based on a fast artificial fish swarm algorithm

A new stochastic resonance method that is based on a fast artificial fish swarm algorithm has been proposed in an effort to address the adaptive parameter-induced stochastic resonance for weak signal detection’s slow convergence time. The target evaluation function for the system is the output signal-to-noise ratio. The method of scale transformation and amplitude compression is used to pre-process the high frequency and large parameter signals. To achieve fast adaptive detection that applies to weak communication signals, the stochastic resonance system’s characteristics are used to constrain the optimization iteration rules.According to the simulation results, the fast artificial fish swarm method has significantly better optimization efficiency and achieves the same optimization results as the basic artificial fish swarm algorithm while reducing convergence time by 74.89%.

Neuronal morphology and network properties modulate signal propagation in multi-layer feedforward network

The propagation and detection of weak signals play a vital role in the central nervous system's information processing. In this paper, a biophysical two-compartment model is adopted to investigate how the neuronal morphology and network properties modulate signal propagation in a multi-layer feedforward network (FFN). The numerical simulation results show that neurons with larger dendrites have higher firing rates and better responses to weak signals. Similarly, the output layer of FFN constructed by larger-dendrite neurons also exhibits better responses. A suitable chaotic current is necessary for the propagation of weak signals. Excessively strong or weak chaotic current leads to propagation failure. Sparse connection and weak synaptic strength optimize the responses of the output layer, which is consistent with real biological networks observed in the brain. It is found that weak signal propagation in FFN is highly correlated with the regulation of firing rate. Our results may provide novel insights into the modeling of complex networks and network function implementation.

An ultrahigh sensitivity acoustic sensor system for weak signal detection based on an ultrahigh-Q CaF2 resonator

Acoustic sensors with ultrahigh sensitivity, broadband response, and high resolution are essential for high-precision nondestructive weak signal detection technology. In this paper, based on the size effect of an ultrahigh-quality (Q) calcium fluoride (CaF2) resonator, a weak acoustic signal is detected by the dispersive response regime in which an acoustic, elastic wave modulates the geometry and is converted to a resonance frequency shift. Through the structural design of the resonator, the sensitivity reaches 11.54 V/Pa at 10 kHz in the experiment. To our knowledge, the result is higher than that of other optical resonator acoustic sensors. We further detected a weak signal as low as 9.4 µPa/Hz1/2, which greatly improved the detection resolution. With a good directionality of 36.4 dB and a broadband frequency response range of 20 Hz–20 kHz, the CaF2 resonator acoustic sensing system can not only acquire and reconstruct speech signals over a long distance but also accurately identify and separate multiple voices in noisy environments. This system shows high performance in weak sound detection, sound source localization, sleep monitoring, and many other voice interaction applications.

Dielectric modulation strategy of carbon nanotube field effect transistors based pressure sensor: towards precise monitoring of human pulse

Continuous monitoring of arterial pulse has great significance for detecting the early onset of cardiovascular disease and assessing health status, while needs pressure sensors with high sensitivity and signal-to-noise ratio (SNR) to accurately capture more health information concealed in pulse waves. Field effect transistors (FETs) combined with the piezoelectric film is an ultrahigh sensitive pressure sensor category, especially when the FET works in the subthreshold regime, where the signal enhancement effect on the piezoelectric response is the most effective. However, controlling the work regime of FET needs extra external bias assistance which will interfere with the piezoelectric response signal and complicate the test system thus making the scheme difficult to implement. Here, we described a gate dielectric modulation strategy to match the subthreshold region of the FET with the piezoelectric output voltage without external gate bias, finally enhancing the sensitivity of the pressure sensor. A carbon nanotube field effect transistor and polyvinylidene fluoride (PVDF) together form the pressure sensor with a high sensitivity of 7 × 10−1 kPa−1 for a pressure range of 0.038–0.467 kPa and 6.86 × 10−2 kPa−1 for a pressure range of 0.467–15.5 kPa, SNR, and the ability to continuously monitor pulse in real-time. Additionally, the sensor enables high-resolution detection of weak pulse signals under large static pressure.

Stabilizing Frequency of a Diode Laser to a Reference Transition of Molecular Iodine through Modulation Transfer Spectroscopy

We report the frequency stabilization of an external cavity diode laser (ECDL) to a reference molecular iodine (I2) transition at 13,531.18 cm−1 (739.03382 nm). Using the Modulation Transfer Spectroscopy (MTS) method for the highly sensitive detection of weak absorption signals, the Doppler-free absorption peaks of I2 corresponding to the hot band transition R(78) (1–11) are resolved. The ECDL’s frequency is stabilized with respect to one of the lines lying within the reference absorption band. For this, the iodine vapor cell is heated to 450 °C and the corresponding circularly polarized pump and probe beam powers are maintained at 10 mW and 1 mW, respectively, to avoid power broadening. The short (100 ms) and long-term (50 h) linewidths of the frequency stabilized laser are measured to be 0.75(3) MHz and 0.5(2) MHz, respectively, whereas the natural linewidth of the specific I2-transitions lie within a range of tens of MHz.

Multi-fold high-order cumulants based CFAR detector for radar weak target detection

As an important detection means, radar is widely used in target monitoring field. However, due to the small radar cross section (RCS) of stealthy or small target and the complex detection environment, the target echo signal is usually submerged in the environmental clutter. Then the target detection based on Pulse-Doppler radar shows the characteristics of weak signal detection. In this paper, the multi-fold high-order cumulant (HOC) on the radar range-Doppler (R-D) map is proposed to elevate the detection performance of the weak target signal, which can effectively eliminate the noise. Then the processed signal is sent to the CFAR detector to estimate the targets' range and velocity. Although HOC has been used in radar signal detection, the detection algorithm was mainly done on the processed signal after one-fold HOC. We propose a construction method of multi-fold HOC using a set of delay vectors to further eliminate residual noise after one-fold HOC processing. Our proposed multi-fold HOC can be seen as a data preprocessing method, which can also be applied to other detection algorithm to further improve its detection performance. Simulation results show that the proposed multi-fold HOC based CFAR algorithm can greatly reduce SNR required for signal detection, and has an advantage in radar weak signal detection.