Signal Generation Research Articles

Photonic generation of frequency agile LFM signals for ISAC systems

Photonic generation of frequency agile LFM signals for ISAC systems

Split Probe-Induced Protein Translational Amplification for Nucleic Acid Detection.

Nucleic acid detection is important in a wide range of applications, including disease diagnosis, genetic testing, biotechnological research, environmental monitoring, and forensic science. However, the application of nucleic acid detection in various fields is hindered by the lack of sensitive, accurate, and inexpensive methods. This study introduces a simple approach to enhance the sensitivity for the accurate detection of nucleic acids. Our approach combined a split-probe strategy with in vitro translational amplification of reporter protein for signal generation to detect nucleic acids with high sensitivity and selectivity. This approach enables target-mediated translational amplification of reporter proteins by linking split probes in the presence of a target microRNA (miRNA). In particular, the fluorescence split-probe sensor adopts a reporter protein with various fluorescence wavelength regions, enabling the simultaneous detection of multiple target miRNAs. Moreover, luminescence detection by merely altering the reporter protein sequence can substantially enhance the sensitivity of detection of target miRNAs. Using this system, we analyzed and quantified target miRNAs in the total RNA extracted from cell lines and cell-derived extracellular vesicles with high specificity and accuracy. This split-probe sensor has potential as a powerful tool for the simple, sensitive, and specific detection of various target nucleic acids.

Tunable and Reconfigurable Fundamental, Frequency-Doubled and Dual-Frequency RF Signal Generator

Tunable and Reconfigurable Fundamental, Frequency-Doubled and Dual-Frequency RF Signal Generator

SDN-controlled multi-user NOMA-OFDM VLC system based on a resource allocation algorithm.

We propose a novel, to our knowledge, resource allocation algorithm (RAA) for a multi-user non-orthogonal multiple access orthogonal frequency division multiplexing (NOMA-OFDM) visible light communication (VLC) system. The proposed algorithm considers both the interference between users and their channel diversity. Bit allocation to users in each iteration is based on the ratio between the already allocated number of bits and the demanded number of bits of users, rather than their channel gains. In this way, the inherent issue of prioritizing strong users in a conventional RAA is avoided. We implement a software-defined-network (SDN)-controlled VLC system with real-time signal generation to validate the proposed RAA. The allocation results in the SDN platform are used to configure a FPGA-based transmitter. Experiments of a two-user NOMA-OFDM system with 115-191 Mbit/s throughput show that the system can dynamically react to the change of data demand and channel responses of users. We further demonstrate that the proposed algorithm outperforms conventional RAAs regardless of the data demand, receiving angles, and distances of users.

DESIGN OF MULIFREQUENCY ELECTRICAL IMPEDANCE TOMOGRAPHY (MfEIT) BASED ON ANALOG DISCOVERY TO DETECT BREAST CANCER

This study aims to design Multifrequency Electrical Impedance Tomography (MfEIT) based on Analog Discovery to detect breast cancer. The MfEIT was built from Analog Discovery which can be used as a signal generator, power supply, voltage control and measuring voltage and phase difference. Other complementary modules are Multiplexer, Instrument amplifier, Voltage Constant Current Source (VCCS), and High Pass Filter (HPF). The MfEIT performance test was carried out on a phantom object made of agar with a certain conductivity that represents breast and cancer tissue. The MfEIT performance testing at a frequency of 10 kHz, 40 kHz, and 80 kHz. The reconstruction from both potential and phase difference data, it shown that are in accordance with the phantom condition, both in number, size and position of anomalies. The reconstruction from the voltage data shown fine at all frequencies, but the phase data produces a good reconstruction image when frequencies was less than 80 kHz.

Comparison of electronic and optoelectronic signal generation for (sub-)THz communications

Abstract In recent years, the significance of terahertz (THz) and (sub-)THz communications has grown substantially due to its promising trade-off between higher capacity compared to microwave-based communication and better resilience against weather dependent influences (e.g., fog and rain). While electronic and optoelectronic techniques have been extensively explored, each offering distinct advantages and limitations, they have predominantly been demonstrated and discussed as individual experiments, making performance comparison challenging. This paper addresses this gap by systematically benchmarking electronic and optoelectronic signal generation approaches under comparable conditions. Our experiments incorporate various receiver types, revealing that best performance is achieved by combining optoelectronic signal generation techniques at the transmitter in combination with an all-electric intradyne receiver. This results in a remarkable line rate of 200 Gbit/s over a distance of 52 m. To our knowledge, this represents the highest line rate achieved for technically relevant transmission distances for indoor access or outdoor small cell networks.

Sensing method on magnetorheological fluid concentration and in-situ settlement monitoring based on wire wound inductor

Aiming at the limitations of magnetorheological fluid (MRF) settlement monitoring in transparent non-metallic containers, a method of MRF concentration measurement based on a wire wound inductor is proposed in this paper, and with the sensing method, in-situ monitoring of MRF sedimentation inside the damper is fulfilled. The varying local concentration of MRF will lead to the inductance change of the wire wound inductor, which is immersed in the MRF at a specific position, with the settling process. When harmonically excited with a signal generator, the relationship between the output amplitude across the inductor and the MRF concentration can be established. To reveal the settling speed dependence, the monitoring of the MRF settling is carried out with different concentrations and viscosities. It is testified that the proposed method can measure the concentration of MRF effectively, and is qualified with the in-situ monitoring of the MRF settling in a real damper.

Experimental study of the generation and propagation of acoustic emission signals in laser micro welding

Experimental study of the generation and propagation of acoustic emission signals in laser micro welding

S-curve bias optimization of navigation signals based on a pre-distortion method

Abstract Nonideal radio-frequency (RF) emission channels directly affect the quality of navigation signals. In particular, the deviation in the pseudo-range, caused by differences among the RF channels of multiple satellites, can decrease user positioning accuracy. Previous studies have primarily focused on designing pre-distortion filters to improve the performance of non-ideal RF channels in navigation signal generators. However, this study shows that using a pre-distortion filter alone limits the improvement of the S-curve bias because the constant-envelope character is compromised, and the nonlinearity of the high-power amplifier (HPA) becomes more pronounced. Applications that require better accuracy require require a smaller S-curve bias. This study proposes a method to compensate for the nonideal RF channel by using pre-distortion that considers both the nonlinear HPA and nonideal filter characteristics. The proposed method is validated through numerical analysis and simulations. The results show that the proposed method can reduce the S-curve bias across different receiver configurations. This study is a useful reference for improving the quality of navigation signals, particularly in terms of correcting the S-curve bias.

Evaluation of an Infinite-Level Inverter Operation Powered by a DC–DC Converter in Open and Closed Loop

This paper evaluates the open- and closed-loop DC–DC converter operation within a DC coupling multilevel inverter architecture to obtain an infinite-level stepped sinusoidal voltage. Adding a cascade controller to the DC–DC converter should reduce the settling time and increase the number of levels in the output voltage waveform; it could decrease the speed error and phase shift concerning the sinusoidal reference signal. The proposed methodology consists of implementing an experimental multilevel inverter with DC coupling through a single-phase bridge inverter energized from a BUCK converter. Trigger signals for the two converters are obtained from a control circuit based in an ATMEGA644P microcontroller to explore its capabilities in power electronics applications. A digital controller is also implemented to evaluate the operation of the BUCK converter in open and closed loop and observe its influence in the stepped sinusoidal output voltage. The evaluation is performed to energize a resistive load with common output voltage in multilevel inverters, i.e., 3, 5, 7, 11, and infinity levels. Results show that during the design stage, fast dynamic elements, like the storage capacitor, can be used to obtain a minimum THD because the settling time is sufficiently fast, the speed error remains small, and there is no need for a controller. A digital controller requires processing time, and although in theory it can reduce the settling time to a minimum, the processor introduces latency in the control signals generation, producing the opposite effect. Controller complexity of the digital controller must be considered because it increases processing time and influences the efficiency of the closed-loop operation.

Design and implementation of wireless power transfer device

Abstract. Magnetic coupled resonant radio energy transmission (WPT) technology utilizes the coupling of the magnetic fields of the transmitting and receiving coils and wirelessly transmits energy through electromagnetic induction, greatly expanding the applications of power equipment in special environments. The technology uses the magnetic field coupling between the transmitting coil and the receiving coil to realize the wireless transmission of energy through electromagnetic induction. This method breaks the limitation of traditional wire transmission and greatly expands the application potential of power equipment in various special environments. In this paper, an efficient, stable and long-distance wireless charging device is designed and realized. In order to improve transmission efficiency, two-coil configuration with series-series structure is adopted, and its equivalent circuit model is established by circuit theory and Kirchhoff's law. Therefore, a new radio energy transmission device based on single chip microcomputer is designed, including PWM signal generator, level matching circuit, high frequency inverter circuit and other key parts. Expressions for transmission efficiency and output power are derived from equation analysis and power-on experiments performed on a physical device. In addition, the effects of transmission frequency, load impedance and transmission distance on the performance are investigated.

A Review of Principles, Analytical Methods, and Applications of SEM‐EDS in Cementitious Materials Characterization

AbstractScanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM‐EDS) is an indispensable and versatile technique that provides detailed 2D spatial insights into the microstructure of heterogenous cementitious systems. To foster clear and systematic understanding of SEM‐EDS analysis in advancing research on cementitious materials, the state‐of‐the‐art principles, analytical approaches, and applications of SEM‐EDS analysis in cementitious systems are reviewed. This review aims to assist researchers in selecting the most appropriate strategy for SEM‐EDS analysis to quantify phase assemblage, elucidate environmental interactions, and investigate microstructure evolution in cementitious systems. The fundamental concepts related to equipment, signal generation, acquisition of diverse EDS data are first presented. Subsequently, various analysis approaches, including point analysis, grid analysis, and mapping analysis are discussed. This review then emphasizes the practical significance and potential value of SEM‐EDS analysis in addressing phase quantification challenges pertaining to cementitious systems. It is posited that the SEM‐EDS analysis holds the promise of becoming the characterization backbone for quantitative research on cementitious systems.

Calorimetric Measurements of a High-Power RF Signal

Development of a high-power RF signal meter based on the method of calorimetric measurements, which in some cases is the only possible one is presented. The device is as a system of elements exchanging either energy or information, the operation and interconnection of which ensures the stability of its functioning. The main elements of the device are: a coordinated load and a two-circuit water-air cooling system that convert RF energy first into thermal electrical energy, and then into internal energy of the coolant (working fluid). The measurement and control system provides information display on the monitor and generation of internal control signals. The work focuses on the process of converting electromagnetic energy into internal energy of the coolant, since the matched RF load is integrated into the cooling system and requires special design and technological solutions to ensure efficient operation. A cooling and measurement system has been designed to test the developed RF absorber with a power of up to 5 kW. The parameters of the cooling system were determined based on minimizing the time to achieve thermal equilibrium (time to establish readings) and the set parameters (input temperature no more than 35 °С, temperature difference no more than 40 °С). Based on calculations of the electrodynamic model constructed by the partial domain method, the geometric dimensions were determined at which the voltage standing wave ratio of the load in the operating frequency range (from DC to 1300 MHz) will be the smallest. The article presents the results of designing a high-frequency wattmeter cooled by a liquid (water), examines the thermophysical processes occurring in it and the influence of the presence of a coolant in the cooling circuit.

Study of High-Frequency Pulsating Flow Control Valves

Pulsating flow signals are widely used in the fields of dynamic calibration of flow meters and reliability testing of fluid transmission pipelines. A high-frequency pulsating flow control valve is proposed, its structure and working principle are introduced, and its mathematical model is also established. Finally, an experimental platform is built to experimentally verify the performance of the high-frequency pulsating flow signal generation of this flow control valve prototype. When applying sinusoidal flow signals of 1–25 Hz, the amplitude of the output flow starts to decay after 2 Hz, and the frequency corresponding to the decay to −3 dB is about 23.5 Hz. The experimental results show that the valve can effectively generate unidirectional sinusoidal flow with a maximum amplitude of 25 L/min and a frequency of 23.5 Hz.

Nested phase modulators for millimeter optical wave signal generation

Nested phase modulators for millimeter optical wave signal generation

Engineering the Functional Expansion of Microneedles.

Microneedles (MNs), composed of an array of micro-sized needles and a supporting base, have transcended their initial use to replace hypodermic needles in drug delivery and fluid collection, advancing toward multifunctional platforms. In this review, four major areas are summarized in interdisciplinary engineering approaches combined with MNs technology. First, electronics engineering, the most extensively researched field, enables applications in biomonitoring, electrical stimulation, and closed-loop theranostics through the generation, transmission, and transformation of electrical signals. Second, in electromagnetic engineering, the responsiveness of electromagnetic induction offers prospects for remote and programmable therapeutic applications. Third, photonic engineering endows MNs with novel functionalities, such as waveguiding and photonic manipulation to enhance optical therapeutic capabilities and facilitate the visualization of disease progression and treatment processes. Lastly, it reviewed the role of mechanical engineering in conferring shape adaptability and programmable motion features necessary for various MNs applications. This review focuses on the functionalities that emerge from the intersection of MNs with complementary engineering technologies, aiming to inspire further research and innovation in microneedle technology for biomedical applications.

Turning four-wave mixing on and off in elliptically birefringent fibers via narrow frequency detuning.

Controlling four-wave mixing (FWM) is vital for several applications, including fiber optical communication, optical signal processing, optical amplification, and frequency generation. This paper presents a novel, to our knowledge, approach to control unidirectional FWM in elliptically birefringent fibers. By leveraging the frequency-dependent polarization eigenmodes of these fibers and detuning the optical frequency of one of the pump fields by a few megahertz, we can turn the FWM interaction on and off, thus controlling the generation of signal and idler fields. Moreover, this approach allows us to turn off the FWM interaction at any desired frequency, enabling all-optical switching and narrowband filtering applications.

Improved EMAT Sensor Design for Enhanced Ultrasonic Signal Detection in Steel Wire Ropes

This study is focused on optimizing electromagnetic acoustic transducer (EMAT) sensors for enhanced ultrasonic guided wave signal generation in steel cables using CAD and modern manufacturing to enable contactless ultrasonic signal transmission and reception. A lab test rig with advanced measurement and data processing was set up to test the sensors’ ability to detect cable damage, like wire breaks and abrasion, while also examining the effect of potential disruptors such as rope soiling. Machine learning algorithms were applied to improve the damage detection accuracy, leading to significant advancements in magnetostrictive measurement methods and providing a new standard for future development in this area. The use of the Vision Transformer Masked Autoencoder Architecture (ViTMAE) and generative pre-training has shown that reliable damage detection is possible despite the considerable signal fluctuations caused by rope movement.

Simultaneous Dual-Band Frequency-Agile Microwave Signal Generation With a Dual Loop Fourier Domain Mode Locked Optoelectronic Oscillator

Simultaneous Dual-Band Frequency-Agile Microwave Signal Generation With a Dual Loop Fourier Domain Mode Locked Optoelectronic Oscillator

Injected phase change seismic source construction and monitoring experiment

Scientific assessment of the transport channels and distribution of oil, gas, water, and other fluids is the key to enhancing oil and gas production capacity and ensuring the safe and efficient development of mineral resources. Traditional microseismic monitoring has been suffering from limitations such as ambiguous attribute characteristics of the seismic source and low signal-to-noise ratios of the data, leading to poor location accuracy and large uncertainties. We develop a phase change seismic source monitoring method that allows for a detailed characterization of the spatial distribution of subsurface fluid transport by accurately locating the equivalent seismic source within supportive fractures. A phase change seismic source is developed and constructed based on the phase change material, enabling control over phase change temperature, source energy, and source scale through the principle of phase change energy storage. The source introduces an active approach to seismic signal generation, diverging from the conventional passive method reliant on rock rupture. Then, 3D homogeneous models are constructed for ground monitoring and in-well monitoring using impulse source propagation theory. The numerical simulation of the wavefield uses the finite-difference method, and the equivalence of discrete sources is confirmed using the Pearson correlation function. The reliability of the monitoring method is verified through a seismic monitoring experiment and comprehensive feasibility analysis.