High-speed Signal Research Articles

Applications of Op-Amp in Automatic Circuit Design

Operational amplifiers (op-amps) are widely used in automatic circuits. It can amplify, filter, sum, integrate and differentiate the voltage, current and power, and it is one of the indispensable key components in modern electronic technology. The paper, through a method of literature review, explores the working principle and usage of operational amplifiers. Initially, the paper introduces the basic concepts and principles of operational amplifiers, laying a theoretical foundation for subsequent analysis. Then, it meticulously analyzes typical applications of operational amplifiers in analog circuit design, including basic amplification circuits, filters, and signal processing circuits. The paper further explores the pivotal role of operational amplifiers in digital circuits, with a focus on the design of digital-to-analog and analog-to-digital conversion circuits. In the section on automatic control circuit design, the paper discusses feedback control systems, the design of PID controllers, and stability analysis. Finally, the paper looks forward to innovative applications of operational amplifiers in modern circuit design, such as power management, high-speed signal amplification, and low-power design. This research aims to provide practical design ideas and references for engineering designers to enhance the automation and intelligence of circuit design.

Designing a filler material to reduce dielectric loss in epoxy-based substrates for high-frequency applications.

In response to the demand for epoxy-based dielectric substrates with low dielectric loss in high-frequency and high-speed signal transmission applications, this study presents a surface-engineered filler material. Utilizing ball-milling, surface-modified aluminum flakes containing organic (stearic acid) and inorganic (aluminum oxide) coatings are developed. Incorporation of the filler into the epoxy matrix results in a significant increase in dielectric permittivity, ε r, by nearly 5 times (from 4.3 to 21.2) and nearly an order of magnitude reduction in dielectric loss, tan δ, (from 0.037 to 0.005) across the 1 to 10 GHz frequency range. Extension of this method to glass fabric-reinforced epoxy-based substrates, resembling widely used FR4 in printed circuit boards, exhibits minimal permittivity variation (4.5-5.4) and considerable reductions in dielectric loss (from 0.04 to 0.01) within the same frequency range. These enhancements are attributed to improved filler dispersion and suppression of electron transport facilitated by double-layer coatings on the flake surface under varying electric fields. The findings highlight the potential of surface-modified aluminum flakes as a promising filler material for high-frequency and high-speed substrate applications requiring low-loss.

Extracting Dispersion Spectrum Directly From the High-Speed Train-Induced Seismic Signal

Extracting Dispersion Spectrum Directly From the High-Speed Train-Induced Seismic Signal

Compact photonic device based on chalcogenide glass loaded lithium niobate on insulator

We propose a hybrid photonic platform based on chalcogenide glass (GeSbSe) integrated with lithium niobate on insulator (LNOI), providing enhanced performance and compactness for integrated photonics. Key photonic components, including grating couplers (GCs), micro-ring resonators, multimode interference (MMI), and the Mach–Zehnder interferometer (MZI), are designed and fabricated on this platform. The micro-ring resonator achieves an intrinsic quality factor of 72,000 and a propagation loss of ∼3 dB/cm. The multimode interference couplers demonstrate minimal excess loss, while the MZI exhibits an extinction ratio exceeding 30 dB over a bandwidth of 50 nm. This hybrid platform, leveraging the unique optical properties of GeSbSe and LNOI, offers scalability and low-loss photonic integrated circuits, with promising applications in high-speed optical communications and signal processing.

Experiment of 2$$\times $$40Gbd PAM8 MISO-FSO system reinforced by high-speed optical signal coupling and precoder-shaped multi-level polar codes

Experiment of 2$$\times $$40Gbd PAM8 MISO-FSO system reinforced by high-speed optical signal coupling and precoder-shaped multi-level polar codes

Vibration monitoring of rotating shafts using DIC and compressed sensing

Monitoring vibrations in rotating shafts is essential for diagnosing and detecting mechanical faults. Digital image correlation (DIC), an optical full-field measurement technique, is increasingly employed in experimental mechanics. This study introduces a novel measurement approach that combines DIC with compressed sensing to monitor high-speed rotating shafts accurately. Traditionally, analyzing rotating shafts requires high-speed sampling devices, which increases experimental costs and reduces spatial resolution. To overcome these limitations, a random exposure sampling method was developed to capture speckle images on the shaft surface with a low frame-rate camera. By leveraging compressed sensing and DIC, the method reconstructs high-speed vibration signals from captured images. Step motion experiments demonstrated that the DIC system achieves a measurement accuracy of 10 µm. Experimental validation was conducted using various setups, including low-speed motors, high-speed rotating shafts, and milling machines, demonstrating the effectiveness of the approach. The measurement results of rotating shafts at 1200 rpm and 6000 rpm, compared with those obtained from laser Doppler vibrometry, demonstrated the effectiveness of the method in vibration measurement. Additionally, experiments on a milling machine showed that vibrations reconstructed using compressed sensing closely matched those measured with a high-speed camera. This measurement system shows significant potential for accurately assessing vibrations in high-speed rotating shafts, offering valuable insights for machinery monitoring and fault diagnosis.

Model predictive control for energy efficient AC motor drives: An overview

AbstractState‐of‐the‐art model‐based predictive control techniques for AC motor drives are reviewed in this paper. A plethora of MPC algorithms with vast number of complex ideas has emerged in the last decade and this work makes an attempt to present those concepts in an intuitive, comprehensive and hierarchical manner. More emphasis is laid on finite control set model predictive control (FCS‐MPC) methods, especially predictive torque control (PTC) and predictive current control (PCC) because of their emergence as the prime focus of ongoing research in energy efficient drive control. The main focus of this review is to analyse the most recent work, signpost the future research directions, identify the core challenges and consolidate the ideas into a coherent and concise reference. A comprehensive classification based on actuation signals is presented and reviewed in detail. Then, the important challenges in MPC implementation, such as computational complexity reduction and delay compensation, weighting factor selection for multi‐objective cost functions, steady state performance and ripple reduction, parameter variations/model mismatching and achieving extended prediction horizons, are surveyed and most relevant solutions are reviewed. A detailed analysis of the last five years related work is given at the end and it is concluded that the future course seems to be diverting towards voltage vector selection with optimised phase, magnitude and duty ratios. Computational burden is still one of the main hurdle towards MPC proliferation and adaptation in AC drive control at the industrial level. However, with advent of high speed and cheaper signal processors and development of efficient algorithms, MPC is rapidly becoming the control method of choice for energy‐efficient drive control.

Test study on the impact of high-speed signal transmission based on VPX connectors

Abstract In high-speed digital signal transmission, VPX connectors play a crucial role as an important link for blind plug interconnection, ensuring the quality of high signal transmission. For high-speed circuit signal transmission, in order to ensure the absolute equal length of high-speed signals and avoid crosstalk caused by high-speed signals, this paper proposes a testing method that establishes a high-speed signal transmission link by designing equal-length sector modules and backplane blind plug interconnection through VPX; By using a vector network analyzer to test relevant parameters, we will analyze the differential characteristic impedance of VPX connectors after engagement under different structural tolerances, and obtain the quality of high-speed signal transmission. This testing research method can effectively analyze the main influencing factors of high-speed signal transmission in VPX connectors, and the research results provide effective support for engineering applications.

Tensile Strength Property with PdCo-Cu Multi-Layer Lamination and Heat Treatment of MEMS Probe for Probe Card

Cantilever wire probe card has limited to transport high-speed signal because of long wire but it is suitable for inspecting high-current and high voltage semiconductor such as wide band gap (WBG) power semiconductors.Superior mechanical property of a probe card wire is in demand because it is respectively used wafer inspection with in and out pad on the top surface of the power semiconductor wafer. Therefore, in this study, tensile specimens of micro electro-mechanical systems (MEMS) probe alternatively layered and electroplated with palladium (Pd)-cobalt (Co) alloy layers and copper (Cu) layers. MEMS probe was also measured tensile strength and elongation with multi-lamination and heat treatment conditions. Additionally, fractography of fracture surface after tensile test were analyzed using a scanning electron microscope (SEM). As the number of PdCo-Cu multi-layer increased, 11, 15 and 21 layered specimens showed higher tensile strength and longer elongation than 5 layered specimens because of the increase of laminated interface of PdCo and Cu. 7 layered specimen after isothermal aging had higher tensile strength and longer elongation than before isothermal aging. In 5, 11, 15 and 21 layered specimens, the fracture surfaces of tensile test specimens without aging treatment showed a ductile-brittle mixed fracture mode. Fracture surfaces of 7-layered specimen before and after isothermal aging showed a ductile-brittle mixed fracture mode.

Quantitative Evaluation of Deformation in High-Speed Magnetic Flux Leakage Signals for Weld Defects in Oil and Gas Pipelines

Complex multiphase flow in oil and gas pipelines raises safety risks. Magnetic flux leakage (MFL) detection effectively identifies pipeline defects. However, the high-speed movement of MFL inspection tools induces motion-induced eddy currents (MIECs), complicating defect recognition and quantification. Most prior research has primarily focused on rectangular defects, leaving a gap in understanding the impact of MIECs on weld defects. This paper proposes the amplitude and shape deformation coefficients to analyze the influence of velocity on various weld defects, including internal reinforcement, lack of penetration, crack, external corrosion, internal corrosion, porosity, and lack of fusion. Utilizing these coefficients, this study examines the influence of the defect size and magnetizer configuration on these velocity-induced effects. The results show that the shape deformation coefficients range from 2.75 to 3.57 for Bx and from −0.13 to −0.3 for By, indicating a significant change in the MFL signal shape at 10 m/s compared to 0 m/s. The amplitude deformation coefficients for lack of penetration, internal corrosion, and porosity range from −0.01 to 0.1 for Bx, and from 0.86 to 0.98 for By, suggesting a decrease in peak-to-peak values. In contrast, other defects exhibit an increase in peak-to-peak values, indicating that the velocity effect may enhance the MFL signal. Also, the defect size and magnetizer configuration can affect the velocity effect on signals. These findings provide essential guidance for quantifying defect sizes and a solid foundation for designing more effective magnetization devices.

Signal processing for enhancing railway communication by integrating deep learning and adaptive equalization techniques.

With the increasing amount of data in railway communication system, the conventional wireless high-frequency communication technology cannot meet the requirements of modern communication and needs to be improved. In order to meet the requirements of high-speed signal processing, a high-speed communication signal processing method based on visible light is developed and studied. This method combines the adaptive equalization algorithm with deep learning and is applied to railway communication signal processing. In this research, the wavelength division multiplexing (WDM) and orthogonal frequency division multiplexing (OFDM) techniques are used, and fuzzy C equalization algorithm is used to softly divide the received signals, reduce signal distortion and interference suppression. The experimental results showed that increasing the step size could reduce the equalization effect, while increasing the modulation parameter will increase the bit error rate. Through deep learning to achieve channel equalization, visible light communication could effectively mitigate multi-path transmission and reflection interference, thereby reducing the bit error rate to the level of 0.0001. Under various signal-to-noise ratios, the system using the channel compensation method achieved the lowest bit error rate. This outcome was achieved by implementing hybrid modulation scheme, including Wavelength division multiplexing (WDM) and direct current-biased optical orthogonal frequency division multiplexing (DCO-OFDM) techniques. It has been proved that this method can effectively reduce the channel distortion when the receiver is moving. This study develops a dependable communication system, which enhances signal recovery, reduces interference, and improves the quality and transmission efficiency of railway communication. The system has practical application value in the field of railway communication signal processing.

Electromagnetic Compatibility Risk Assessment Model for High-Speed Rail On-Board Signaling System

Electromagnetic Compatibility Risk Assessment Model for High-Speed Rail On-Board Signaling System

Wafer-scale fabrication of InGaP-on-insulator for nonlinear and quantum photonic applications

The development of manufacturable and scalable integrated nonlinear photonic materials is driving key technologies in diverse areas, such as high-speed communications, signal processing, sensing, and quantum information. Here, we demonstrate a nonlinear platform—InGaP-on-insulator—optimized for visible-to-telecommunication wavelength χ(2) nonlinear optical processes. In this work, we detail our 100 mm wafer-scale InGaP-on-insulator fabrication process realized via wafer bonding, optical lithography, and dry-etching techniques. The resulting wafers yield 1000 s of components in each fabrication cycle, with initial designs that include chip-to-fiber couplers, 12.5-cm-long nested spiral waveguides, and arrays of microring resonators with free-spectral ranges spanning 400–900 GHz. We demonstrate intrinsic resonator quality factors as high as 324 000 (440 000) for single-resonance (split-resonance) modes near 1550 nm corresponding to 1.56 dB/cm (1.22 dB/cm) propagation loss. We analyze the loss vs waveguide width and resonator radius to establish the operating regime for optimal 775–1550 nm phase matching. By combining the high χ(2) and χ(3) optical nonlinearity of InGaP with wafer-scale fabrication and low propagation loss, these results open promising possibilities for entangled-photon, multi-photon, and squeezed light generation.

High-Speed Signal Optimization at Differential VIAs in Multilayer Printed Circuit Boards

The number of Printed Circuit Board (PCB) layers is continually increasing with the increase in data transmission rates, and the Signal Integrity (SI) of high-speed digital systems cannot be ignored. Introducing Vertical Interconnect Accesses (VIAs) in PCBs can realize the electrical connection between the top layer and the inner layers, however, VIAs represent one of the most important reasons for discontinuity between the PCBs and package. In this paper, a new optimization scheme for a differential VIA stub is proposed, with 3D full-wave numerical simulation used for modeling and simulation. Results show that this scheme optimizes the return loss and insertion loss while making the signal eye diagram more ideal, which can improve the transmission effect of high-speed signals.

Image encoding and recovery based on excited spiking patterns in a VCSEL neuron

We propose and investigate an image encoding and recovery scheme based on an excited 1550-nm vertical-cavity surface-emitting laser (VCSEL). The results show that VCSEL subjected to orthogonal optical injection can exhibit some neuron-like behaviors including injection locking, spiking exciting and inhibition, and damped oscillations. Based on the excited spiking patterns, the image can be encoded into continuous, up to GHz-rate optical spike trains, and then be successfully recovered after adopting a post-processing technique. Additionally, the experimental results are almost identical to that of theoretical simulations, and the image recovery accuracy (IRA) can reach 98.3% in experiment. This proposed image encoding and recovery approach can open a new window for future high-speed all-optical signal processing in the photonic spiking neural networks (PSNN).

Research on high-speed digital optical signal jitter measurement technology based on clock recovery algorithm using eye diagram opening area

With the rapid development of information technology, high-speed digital optical signal transmission technology has become the core of modern communication networks. However, the increase in transmission rates brings challenges such as noise, distortion, and interference, which affect the accuracy of clock recovery. To address these issues, this study proposes a clock recovery algorithm based on the eye diagram opening area to improve the accuracy and efficiency of high-speed digital optical signal jitter measurement. The proposed method extracts clock information from the signal using the opening area and curvature characteristics of the eye diagram for jitter measurement. Experimental results demonstrate that the clock recovery algorithm based on the eye diagram opening area can stably reconstruct the signal eye diagram and obtain jitter parameters under different optical power conditions. At optical powers of −7.2 dBm, −12.2 dBm, and −17.2 dBm, the Q-factors were 8.8, 7.6, and 4.3, respectively, and the RMS jitter values were 12.2 ps, 13.4 ps, and 21.2 ps, respectively. At optical powers of −2.3 dBm, 0.1 dBm, 2.4 dBm, 4.6 dBm, and 6.0 dBm, the Q-factors were 9.1, 9.3, 9.5, 9.7, and 10.0, respectively, and the average jitter values were 8.9 ps, 8.5 ps, 8.0 ps, 7.5 ps, and 7.0 ps. These results indicate that the proposed algorithm performs excellently under low optical power conditions and maintains high recovery accuracy even when jitter increases at higher optical powers. The clock recovery algorithm based on the eye diagram opening area significantly improves the accuracy and stability of high-speed digital optical signal jitter measurement, enriches the theoretical research of clock recovery algorithms, and shows significant advantages in improving signal transmission quality, reducing bit error rate, and enhancing communication link reliability. The research outcomes provide key technical support for the optimization of modern high-speed optical communication systems.

Advancing LWIR FSO communication through high-speed multilevel signals and directly modulated quantum cascade lasers.

This study investigates the potential of long-wave infrared (LWIR) free-space optical (FSO) transmission using multilevel signals to achieve high spectral efficiency. The FSO transmission system includes a directly modulated-quantum cascade laser (DM-QCL) operating at 9.1 µm and a mercury cadmium telluride (MCT) detector. The laser operated at the temperature settings of 15°C and 20°C. The experiment was conducted over a distance of 1 m and in a lab as a controlled environment. We conduct small-signal characterization of the system, including the DM-QCL chip and MCT detector, evaluating the end-to-end response of both components and all associated electrical elements. For large-signal characterization, we employ a range of modulation formats, including non-return-to-zero on-off keying (NRZ-OOK), 4-level pulse amplitude modulation (PAM4), and 6-level PAM (PAM6), with the objective of optimizing both the bit rate and spectral efficiency of the FSO transmission by applying pre- and post-processing equalization. At 15°C, the studied LWIR FSO system achieves net bitrates of 15 Gbps with an NRZ-OOK signal and 16.9 Gbps with PAM4, both below the 6.25% overhead hard decision-forward error correction (6.25%-OH HD-FEC) limit, and 10 Gbps NRZ-OOK below the 2.7% overhead Reed-Solomon RS(528,514) pre-FEC (KR-FEC limit). At 20°C, we obtained net bitrates of 14.1 Gbps with NRZ-OOK, 16.9 Gbps with PAM4, and 16.4 Gbps with PAM6. Furthermore, we evaluate the BER performance as a function of the decision feedback equalization (DFE) tap number to explore the role of equalization in enhancing signal fidelity and reducing errors in FSO transmission. Our findings accentuate the competitive potential of DM-QCL and MCT detector-based FSO transceivers with digital equalization for the next generation of FSO communication systems.

Dual-band hybrid fiber-wireless delivery system for high-speed data communications in CRAN based on polarization multiplexing with switching capabilities

This work presents a Radio-over-Fiber architecture for Cloud Radio Access Networks (CRAN) based on polarization division multiplexing for delivering up-converted high-speed data signals using a single laser-photodetector pair and free of polarization tracking devices. This system enables the allocation of data signals in two different bands defined as low-frequency (5–25 GHz) and high-frequency (55–65 GHz) millimeter waves (mmWave). Polarization multiplexing ensures minimal crosstalk when data signals are photonically up-converted while providing all-optical inter-band switching capabilities. Proof-of-concept experiments have been performed by simultaneously transmitting NRZ and multi-carrier modulated (Discrete Multitone - DMT) data signals over a radio-over-fiber link consisting of 1 km of standard optical fiber and radio transmission in the 7.5 GHz (wired) and 60 GHz (wireless) bands, respectively, with an estimated potential total throughput of at least 7.5 Gbps when considering the transmission of NRZ signals in these mmWave carriers. Results exhibit a BER below the FEC limit of 3.8 × 10−3 in all cases analyzed when the received optical power at the remote radio head (RRH) is above −4 dBm. The reduced number of components and versatility of this implementation provide a cost-effective solution for delivering and switching high-speed data signals in RF fronthaul for future 5G/6G communications.

Polyphenylene oxide/SiO2 composites: Towards ultra-low dielectric loss and high thermal conductivity of microwave substrates

With the rapid development of electronic information industry has raised the requirements for the performance of electronic components. Therefore, it is essential to research dielectric substrate materials with excellent dielectric properties and good thermal conductivity at high frequencies. This study introduced vinyl trimethoxysilane (VTMS) surface-functionalized silicon dioxide (SiO2) into the polyphenylene oxide/styrene–butadiene–styrene/triallyl isocyanurate (PST) composite resin to prepare PST/V-SiO2 composite. The microwave composite substrates for high-speed signal propagation were prepared through a process involving scraping coating and hot pressing. The study investigated the impact of varying amounts of V-SiO2 on the dielectric property, thermal stability, and thermal conductivity of the composites. The microwave composite substrates exhibit excellent dielectric properties and good thermal conductivity. When the V-SiO2 content is 80 wt%, the dielectric loss is 1.8 × 10-3 with a low dielectric constant (≤3.23@10 GHz). Furthermore, the PST/V-SiO2 composite displays higher thermal conductivity (0.735 W/(m·K)) and low moisture absorption. This research provides a novel strategy to develop microwave composite substrates with low dielectric loss and high thermal conductivity.

Binary Adder, Subtractor and Parity Checker Based on Optical Logic Gates

We propose schemes for binary adder, subtractor and parity checker using optical logic gates. These schemes could be useful for calculations using optical systems. Utilizing optical logic gates, we can achieve functions of binary adder, subtractor and parity checker of high-speed optical signals. Due to two-photon absorption in the wetting layer, quantum dot-semiconductor optical amplifier Mach-Zehnder interferometer (QD-SOA-MZI) can work as high data rate optical logic gates. The simulated result supports the idea that it is possible to realize all-optical binary adder, subtractor and parity checker at high optical signal rates.