Weak Signal Acquisition Research Articles

High‐Performance Single‐Microplate Perovskite Photodetectors Based on Polyvinyl Alcohol Filled Planar Electrodes for Weak‐Light Imaging and Pixel Integration

AbstractPhotoconductors featuring an individual micro/nano‐crystal as the photoactive channel hold the great promise for next‐generation integrated optoelectronics. Meanwhile, the gain aiming for signal amplification without an extra amplifier, the fast response for fast data transfer, and low dark current for weak signal acquisition are highly desirable in integrated optoelectronics, but are inherent trade‐off in traditional photoconductors. Herein, the study demonstrates a single‐microplate MAPbI3 photoconductor based on polyvinyl alcohol‐filled planar electrodes that can simultaneously achieve excellent performance on these parameters. The superior performance can be attributed to the exquisite design of filling the device channel gap with polyvinyl alcohol. This deep‐work‐function transparent polyvinyl alcohol can not only passivate surface defects of the perovskite microplate by hydrogen bonding, but also form a heterojunction with top perovskites to induce a depleted channel. Resultant single‐microplate photodetectors exhibit exceptional performance characteristics including ultra‐low noise‐equivalent power of 0.19 fW Hz−1/2, high specific detectivity of 3.68 × 1014 Jones, fast response of 3.2 µs, high EQE‐bandwidth over 107 Hz, as well as excellent stability. More importantly, single‐microplate MAPbI3 photoconductors demonstrate ultra‐weak‐light imaging ability surpassing silicon counterparts. Furthermore, the successful integration of their microplate pixels showcases the promising prospect for integrated optoelectronics.

Hybrid Integrated Wearable Patch for Brain EEG-fNIRS Monitoring.

Synchronous monitoring electroencephalogram (EEG) and functional near-infrared spectroscopy (fNIRS) have received significant attention in brain science research for their provision of more information on neuro-loop interactions. There is a need for an integrated hybrid EEG-fNIRS patch to synchronously monitor surface EEG and deep brain fNIRS signals. Here, we developed a hybrid EEG-fNIRS patch capable of acquiring high-quality, co-located EEG and fNIRS signals. This patch is wearable and provides easy cognition and emotion detection, while reducing the spatial interference and signal crosstalk by integration, which leads to high spatial-temporal correspondence and signal quality. The modular design of the EEG-fNIRS acquisition unit and optimized mechanical design enables the patch to obtain EEG and fNIRS signals at the same location and eliminates spatial interference. The EEG pre-amplifier on the electrode side effectively improves the acquisition of weak EEG signals and significantly reduces input noise to 0.9 μVrms, amplitude distortion to less than 2%, and frequency distortion to less than 1%. Detrending, motion correction algorithms, and band-pass filtering were used to remove physiological noise, baseline drift, and motion artifacts from the fNIRS signal. A high fNIRS source switching frequency configuration above 100 Hz improves crosstalk suppression between fNIRS and EEG signals. The Stroop task was carried out to verify its performance; the patch can acquire event-related potentials and hemodynamic information associated with cognition in the prefrontal area.

Enhancement of weak signals by dynamic stochastic resonance in dark-field microscopy imaging

Abstract Enhancing weak signal acquisition is pivotal for bolstering analysis and detection capabilities. Herein, a dynamic stochastic resonance (DSR) algorithm for weak signal amplification that was identified to significantly improve the imaging visibility of dark-field microscopy nanoparticles under low illumination conditions is presented. When further combined with composite filed microscopy, DSR displays signal amplification much more effectively, showing high promise for detection purposes.

Flexible Finger-Shaped Active Dry EEG Electrode With a Configurable Application-Specific Integrated Circuit and Embedded Leadoff Detection

Dealing with the discomfort and complex setting-up of conventional wet electrodes in the electroencephalography (EEG) monitoring for personal daily healthcare, a flexible finger-shaped active dry EEG electrode is developed and tested in this paper. The flexible finger-shaped dry electrodes, made of polydimethylsiloxane (PDMS) and elastic electrically conductive composite (ECC), penetrate through the hair to achieve stable contact with the scalp. To improve the quality of weak signal acquisition, a customized configurable application-specific integrated circuit (ASIC) is integrated using ECC based fabrication process, which amplifies the signal by 100 V/V, detects the lead-off states of electrodes, communicates with the back-end electronic module for configuration and status feedback. The amplifiers have >100 MΩ @ 50 Hz input impedance to match the large interface impedance of dry electrodes. An I2C slave controller with a dedicated wake-up oscillator is introduced for excellent configurability with a reduced number of wires and lower power consumption. Modulus of the proposed electrodes are similar as human tissue, ensuring remarkable user comfort. Besides, the process costs low and mold-casting is suitable for mass production. Over all, the easy-to-use active dry electrode could meet the requirements for daily EEG monitoring.

Acquisition of Weak BDS Signal in the Lunar Environment

Autonomous navigation using the GNSS has been increasingly used in lunar exploration missions, as it is considered an efficient method for spacecraft to operate without relying on ground facilities. However, so far, only GPS and Galileo have been studied and implemented in lunar missions, whereas the potential of BDS-3 for such missions remains largely unexplored. This paper presents an analysis and evaluation of the navigation service capabilities for spacecraft at lunar altitudes by utilizing existing GNSS satellite resources in orbit. In detail, we investigate the number of GNSS signals received by low lunar orbit (LLO) receivers, as well as the carrier-to-noise ratio (C/N0), Doppler shift, and geometric dilution of precision (GDOP) of the received signal. Additionally, a digital intermediate frequency (IF) signal simulation program to emulate the BDS B1I signal is utilized, which allows to freely set the carrier-to-noise ratio, Doppler shift, and code phase. Based on this framework, we discussed a high-sensitivity BDS B1I signal receiver and validated its performance with simulated signals. We verified the capabilities of coherent integration, non-coherent integration, differential integration, and semi-bit methods to detect weak BDS B1I signals in a lunar environment. The results indicate that the semi-bit coherent differential integration method is still capable of acquiring signals at a C/N0 of 15 dB-Hz and can effectively suppress the navigation data bit sign transition.

Fast GPU based acquisition with minimum loss and downsampling techniques for weak BeiDou SBAS signals

AbstractFor a receiver of the BeiDou Satellite Based Augmentation System (BDSBAS), the acquisition aims to coarsely estimate the pseudo‐code delays and carrier Doppler shifts of the received signals. The use of downsampling techniques to accelerate this acquisition process for weak signals has been an emerging topic. However, the acquisition probabilities of conventional algorithms with downsampling are inadequate and need to be enhanced to prevent excessive false alarms due to degradation of the peak signal‐to‐noise ratios (PSNRs) during acquisition. To improve signal acquisition performance, we introduce an enhancer function before downsampling to achieve the minimum PSNR loss during acquisition. Then, we use graphic processing unit (GPU) functions to speed up the processing loop, matrix multiplication and fast Fourier transform operations. We thus present a fast GPU‐based acquisition method by using minimum loss and downsampling techniques. Our experimental results show the remarkable effectiveness of our method for receiving weak BDSBAS signals as compared to legacy downsampling algorithms. This work seeks not only to solve the current issue of achieving fast acquisition of weak BDSBAS signals but also to inspire creative new ideas that spur further advances in this promising field in the future.

Synchronous capture method of multi-channel weak signal in long-distance communication network

In order to improve the accuracy, efficiency and network throughput of multi-channel weak signal synchronous acquisition in the network, a multi-channel weak signal synchronous acquisition method in remote communication network is designed. Firstly, by analyzing the multi-channel structure of remote communication network, the interference factors of multi-channel weak signal acquisition are determined. The parameter model method is used to estimate the bispectrum of weak signals, complete the multi-channel weak signal extraction of remote communication network, and preprocess the multi-channel weak signals of remote communication network by average filtering method. On this basis, the characteristics of multi-channel weak signals in the remote communication network are judged, and their characteristics are changed through the short time window function in the time domain, and the multi-channel weak signal synchronous catcher in the remote communication network is constructed to realize the synchronous acquisition of multi-channel weak signals in the remote communication network. The experimental results show that this method has high accuracy, short time-consuming and good network throughput. The acquisition accuracy of this method is always maintained at more than 90%.

A high dynamic weak spread spectrum signal acquisition strategy based on the transfer model

To solve the problem of low Earth orbit (Leo) satellite constellation link spread spectrum signal acquisition in the high dynamic weak environment, this paper proposes a acquisition strategy based on transfer model. In this paper, we analyze the dynamic characteristics of link signal. An improved method of parallel code phase search acquisition based on transfer model acquisition strategy is introduced, the improvement of the proposed acquisition strategy to the traditional acquisition algorithm is illustrated through theoretical analysis. Simulation results verify the superiority of the acquisition strategy based on the transfer model for high dynamic weak signal acquisition.

Development of Special Geomagnetic Data Acquisition System with Low Cost

It is known to all that the wide monitoring of geomagnetic anomalies requires geomagnetic detection equipment to be of low cost, low power, and high stability. On the basis of the weak magnetic signal detection technology, a weak magnetic signal acquisition system with low-cost magnetic data acquisition, data processing, and data analysis is established by using a three-dimensional SEN-R65 magnetic sensor, magnetic signal acquisition chip PNI 11096, and P89C668 chips. Firstly, the hardware of a low-cost geomagnetic data acquisition system is designed, and the corresponding data processing and analysis programs are written. Based on the designed hardware circuit and data processing for functions such as acquisition, transmission, storage, and real-time display of geomagnetic signals, it is found that the developed instrument meets the expectations of the low-cost geomagnetic data acquisition system designed in this paper, indicating that the system is applicable.

A Continuous Data Acquisition System for Three-Component Surface Microseismic Real-Time Monitoring

Surface microseismic monitoring is one of the most critical technologies for monitoring the dynamic subsurface reservoir processes. Due to the weak signals and poor signal-to-noise ratio (SNR), there are two major challenges to monitor the reservoir processes in an accurate and efficient way. One challenge is concerned with weak signals acquisition and how to evaluate the instrument’s abilities to record the microseismic events. The other one is how to realize real-time data monitoring during dynamic processes. Taking these challenges into consideration, a design approach to develop buried sensors consisting of three-component sensors and a low-cost, low-power consumption embedded device for microseismic monitoring data logger with the acquisition, synchronization, record, and transmission functions are presented. The circuits are divided into two printed circuit boards (PCBs). One is for a signal processing circuit, which consists of signal conditioning and analog-to-digital converter (ADC), and the other is for a digital circuit, which consists of the microcontroller and peripherals, including the global navigation satellite system (GNSS), Micro Secure Digital Memory Card (SD card), and Ethernet transceivers. The circuit for signal conditioning and ADC is a combination of a preamplifier, low-pass filter, programmable gain amplifier, and ADC. It has three modes: real-time monitoring, continuous recording, and combination. A software is designed to work in cooperation with the hardware to adjust the working parameters and modes. The self-noise of the data logger is tested in the laboratory, and the monitoring abilities of the data logger are evaluated. Finally, the surface microseismic monitoring system has been tested in the field to evaluate its performance for academic purposes.

Design of a Sampling System for Wide Range nano-current Signal

Space particle radiation will greatly shorten the service life of basic components, resulting in premature failure of aircraft. For newly developed electronic components for space applications, strict anti irradiation performance evaluation must be carried out to master their working characteristics and performance degradation mechanism in space irradiation environment, so as to provide a reliable guarantee for the safe operation of aerospace electronic equipment in orbit. Taking high-voltage power devices such as SiC MOSFET and IGBT as the research object, this paper designs a high-precision weak current signal acquisition and measurement system to continuously monitor its working current under specific track applications, so as to verify the mechanism of space radiation effect and the effectiveness of reinforcement technology. The experimental results show that the system has the advantages of wide range, low noise, high precision and good stability. It can be applied to the experimental verification of high-voltage power devices in various space environments, including space station orbit.

A Highly Integrated and Diminutive Fluorescence Detector for Point-of-Care Testing: Dual Negative Feedback Light-Emitting Diode (LED) Drive and Photoelectric Processing Circuits Design and Implementation.

As an important detection tool in biochemistry, fluorescence detection has wide applications. Quantitative detection can be achieved by detecting fluorescence signals excited by excitation light at a specific wavelength range. Therefore, the key to fluorescence detection is the stable control of the excitation light and the accurate acquisition of weak photoelectric signals. Moreover, to improve portability and instantaneity, devices are developing in miniaturization and integration. As the core of such devices, fluorescence detectors should also have these features. Under this circumstance, we designed a highly integrated and diminutive fluorescence detector and focused on its excitation light driving and photoelectric signal processing. A current–light dual negative feedback light-emitting diode (LED) driving circuit was proposed to obtain constant current and luminance. In addition, a silicon photodiode (PD) was used to receive and convert the fluorescence signal to an electric signal. Then, amplifying, filtering, and analog-to-digital (A/D) converting were applied to make the detection of weak fluorescence signals possible. The test results showed that the designed circuit has wonderful performance, and the detector shows good linearity (R2 = 0.9967) and sensitivity (LOD = 0.077 nM) in the detection of fluorescein sodium solution. Finally, a real-time fluorescence polymerase chain reaction (real-time PCR) of Legionella pneumophila was carried out on a homemade platform equipped with this detector, indicating that the detector met the requirements of real-time PCR detection.

A High Dynamic Weak Spread Spectrum Signal Acquisition Strategy Based on Iterative Local Search

To solve the acquisition problem of the satellite-ground microwave link ranging of the China Space Station, iterative local search (ILS) is proposed. In this paper, an iterative-local-search-based acquisition strategy is presented, and a Doppler frequency and code phase transfer model is designed, which can accomplish acquisition by multiple rounds of two-dimensional search. The adaptability of the ILS improved traditional acquisition algorithm to a high dynamic and low signal-to-noise ratio (SNR) environment can be significantly improved without relying on prior information. For the classical parallel code phase acquisition algorithm, the performance of the ILS acquisition strategy was experimentally evaluated for high dynamic weak signals, and the results demonstrated the superiority of the proposed strategy. The computational complexity of the ILS improved parallel code phase acquisition algorithm was greatly reduced. The sensitivity of the parallel code phase acquisition algorithm improved by the ILS strategy to the acquisition of weak signals in a dynamic environment was significantly improved.

Design of Adaptive Filter for Weak Signal Acquisition System

In order to solve the contradiction between the accuracy of weak signal acquisition and the limited frequency band, a weak signal acquisition system based on adaptive filter is designed in this paper. According to the change of the signal frequency, the proposed adaptive filter based on the technology of hardware adjustable narrowband filtering decides the frequency of the input signal, realizes the narrowband filtering and the large dynamic variation of specific frequency signal. And the high precision acquisition of weak signal can be obtained through the processing of filtering technologies under complex noise conditions, which includes adaptive frequency search, digital low-pass filtering, adaptive adjustment, etc. Finally, the test experiment of the designed filter has been implemented, and the experimental results show that the adaptive filter of the weak signal acquisition system can meet the design requirements and show high performance of data acquisition for weak signal.

Mathematical Analysis and Micro-Spacing Implementation of Acoustic Sensor Based on Bio-Inspired Intermembrane Bridge Structure.

A biomimetic study on the auditory localization mechanism of Ormia ochracea was performed to improve the localization ability of small acoustic systems. We also present a microscale implementation of an acoustic localization device inspired by the auditory organ of the parasitic O. ochracea. The device consists of a pair of circular membranes coupled together with an elastic beam. The coupling serves to amplify the difference in magnitude and phase between the two membranes’ responses as the incident angle of the sound changes, allowing directional information to be deduced from the coupled device response. The research results show that the intermembrane bridge structure improves the sound source localization and directional weak acoustic signal acquisition of sound detectors. The recognition rate of the phase difference and amplitude ratio was greatly improved. The theoretical resolution of the incident angle of the sound source can reach 2° at a phase difference recognition rate of 5°. The sound source’s optimal identification frequency range for the coupling device based on the intermembrane bridge bionic structure is 300 Hz to 1500 Hz.

A 3D hydrodynamic flow-focusing device for cell sorting

Optical-based microfluidic cell sorting has become increasingly attractive for applications in life and environmental sciences due to its ability of sophisticated cell handling in flow. The majority of these microfluidic cell sorting devices employ two-dimensional fluid flow control strategies, which lack the ability to manipulate the position of cells arbitrarily for precise optical detection, therefore resulting in reduced sorting accuracy and purity. Although three-dimensional (3D) hydrodynamic devices have better flow-focusing characteristics, most lack the flexibility to arbitrarily position the sample flow in each direction. Thus, there have been very few studies using 3D hydrodynamic flow focusing for sorting. Herein, we designed a 3D hydrodynamic focusing sorting platform based on independent sheath flow-focusing and pressure-actuated switching. This design offers many advantages in terms of reliable acquisition of weak Raman signals due to the ability to precisely control the speed and position of samples in 3D. With a proof-of-concept demonstration, we show this 3D hydrodynamic focusing-based sorting device has the potential to reach a high degree of accuracy for Raman activated sorting.

Design of a High Precision Data Acquisition System of Weak Signal

In order to solve the problem of high precision acquisition of weak signals, a high accurately weak signal acquisition system has been designed in this paper. According to the proposed design requirements of the data acquisition system, the hardware acquisition circuit and the drive circuit as well as the processing of the upper computer are divided into modules. As the central work of this paper, the hardware and software of the drive modules are designed with specific flowcharts are given. And the designs of the system were debugged, analyzed and tested through experiment tests, and the high precision data acquisition of 0.5V DC signal has been obtained with specific datum are provided. The effectiveness of the proposed design to data acquisition of weak signal has been validated by the experimental results, and this design could be used in engineering projects.

Structure and Performance Analysis of Signal Acquisition and Doppler Tracking in LEO Augmented GNSS Receiver.

Due to the low signal power, the Global Navigation Satellite System (GNSS) signal is vulnerable to interference and even cannot be captured or tracked in harsh environments. As an alternative, the Low Earth Orbit (LEO) satellite has been widely used in the navigation field due to the advantages of low cost and strong signals. It is becoming a significant component of the new combined navigation system with GNSS. The combination of an LEO Doppler signal and GNSS observables can improve the positioning accuracy and high-precision positioning convergence time of the GNSS receiver. However, the GNSS signal receiving capability cannot be improved from this data fusion level. We propose a novel assisted structure where GNSS signal acquisition and Doppler tracking are assisted by LEO Doppler positioning. The receiver uses the LEO signal to achieve Doppler positioning firstly. Then, the coarse position with the GNSS navigation messages received from LEO, as well as the estimated clock information, is used to assist in the acquisition and tracking of GNSS. In this way, the GNSS receiver’s sensitivity can get the benefit from this integrated system. The paper presents the structure of the assisted receiver and analyzes the assisted GNSS signal acquisition and carrier tracking performance in detail. Simulation experiments of this assisted structure are carried out to verify its superiority of acquisition and tracking sensitivity in comparison with standalone GNSS receivers. Theoretical analysis and experimental results show that the proposed acquisition method can achieve 90% detection probability at a carrier-to-noise ratio (C/N0) of 15 dB-Hz, which is about 8 dB higher than the conventional acquisition method without assistance; the proposed tracking method can track weak signals of 5 dB-Hz, which is about 4 dB higher than the conventional method. Therefore, this novel LEO-assisted receiver has significantly improved weak signal acquisition and tracking sensitivity.

Study on chaotic oscillator‐based algorithm for weak GLONASS signal acquisition

SummaryAccording to the characteristics of the chaotic oscillator in detecting weak signals, an algorithm based on Duffing chaotic oscillator array was proposed for acquisition of weak GLONASS signals. By means of GLONASS intermediate frequency and Duffing chaotic oscillator models, Lyapunov exponent is adopted to judge the critical condition of phase track and decide whether GLONASS signals exist or not by the change of the critical condition, and numeric iteration procedure is used to calculate the exponent. Finally, the performance of algorithm is simulated using GLONASS intermediate frequency data. The results indicate that acquisition algorithm can satisfy the need of object positioning in low signal‐to‐noise ratio environment.

A Large Doppler Weak Direct Spread Signal Acquisition Algorithm and Optimization Method

For satellite receivers, on the one hand, large Doppler frequency will cause accumulation loss for a long-term accumulation acquisition algorithm, which leads to the problem of correlation peak broadening; on the other hand, searching within a larger Doppler uncertainty range will consume more logic resources. Thus, this paper first analyses the impact of large Doppler frequency on coherent accumulation and non-coherent accumulation based on the traditional Double Block Zero Padding (DBZP) algorithm. Secondly, an improved DBZP algorithm is designed in combination with the Keystone transform of the transform domain, and simplify the variable-scale DFT to reduce the amount of calculation. Then, the key parameters of the algorithm are extracted to establish the optimization objective function, the algorithm parameters are optimized through genetic algorithm without reducing the performance of the algorithm. Finally, the simulation verifies that the optimized and improved DBZP algorithm can effectively solve the problem of code phase walking.