Optimal Waveform Research Articles

A Novel Tracking Algorithm Based on Waveform Selection for Maneuvering Targets in Clutter

The cognition radar utilizes the dynamic waveform configuration to adapt to the environment to improve tracking performance. A novel tracking algorithm based on waveform selection is proposed to address the maneuvering aircraft tracking problem in clutter. Based on the modified current statistical (MCS) model, the modified probabilistic data association filter (MPDAF) is integrated with the square-root cubature Kalman filter (SCKF) to deal with the nonlinear measurement and the clutter. Additionally, the waveform library is established by applying the fractional Fourier transform (FRFT) to a base waveform, and a direct method is proposed to select the optimal waveform to minimize the posterior state error covariance matrix. The simulation results showed that, compared with the filters with the fixed waveform as well as the state-of-the-art algorithms, the proposed algorithm achieved higher estimation precision and lower track loss percentage while maintaining a low computational burden.

Joint Jam Perception and Adaptive Waveform Optimization for Anti-Interrupted Sampling Repeater Jamming

Joint Jam Perception and Adaptive Waveform Optimization for Anti-Interrupted Sampling Repeater Jamming

Phase Retrieval for Radar Constant–Modulus Signal Design Based on the Bacterial Foraging Optimization Algorithm

Optimizing the energy spectrum density (ESD) of a transmitted waveform can improve radar performance. The design of a time–domain constant–modulus signal corresponding to the transmitted waveform ESD is practically important because constant–modulus signals can maximize transmission power and meet the hardware requirements of radar transmitters. Here, we present a time–domain signal design under dual constraints of energy and constant modulus. The mutual information (MI)–based waveform design method is used to design transmitted waveform ESD under the energy constraint. Then, the bacterial foraging optimization algorithm (BFOA) is proposed to design the time–domain constant–modulus signal. We use minimum mean square error (MMSE) in the frequency domain as the cost function. The BFOA monotonously decreases the MMSE with increasing iterations, which makes the ESD of the time–domain constant–modulus signal close to the MI–based optimal waveform ESD. The simulation results indicate that the proposed algorithm has advantages, including insensitivity to initial phases, rapid convergence, smaller MI loss, and MMSE compared with the iterative reconstruction algorithm.

Generation of neutral droplets via waveform optimization for stable electrohydrodynamic drop-on-demand printing

Electrohydrodynamic (EHD) drop-on-demand (DOD) printing is a highly promising additive manufacturing technology, particularly for micro- and nanoscale applications, owing to its exceptional printing resolution. However, a significant challenge for EHD DOD to achieve stable printing is the accumulation of residual charge, particularly on highly insulated substrates where the charge cannot be discharged. A novel voltage-driven waveform is proposed to generate neutral droplets in EHD DOD printing, aiming to completely solve the problem of residual charge accumulation. The proposed voltage-driven waveform consists of two waveforms with opposite polarity and equal amplitude. The waveforms of opposite polarity generate two droplets with opposite charges. Overlapping these two droplets causes the charges to be neutralized, therefore generating neutral droplets. The correctness of the proposed method is verified through simulations and experiments, and the printing parameters were optimized accordingly. Notably, silver nanowires with a line width of 5.3 μm were successfully printed on insulating substrates using this technique, and large-area on-demand patterns were stably printed. This outcome underscores the capability of the proposed high-voltage driving waveform to generate charge-neutral droplets, thereby significantly enhancing the stability of EHD DOD printing and facilitating its implementation in high-resolution manufacturing processes.

High-Performance Multi-Level Grayscale Conversion by Driving Waveform Optimization in Electrowetting Displays.

As a new type of reflective display, electrowetting display (EWD) has excellent dynamic display performance, which is based on polymer coatings. However, there are still some issues which can limit its performance, such as oil backflow and the hysteresis effect which reduces the stability and response speed of EWDs. Therefore, an effective driving waveform was proposed to overcome these drawbacks, which consisted of grayscale conversions between low gray levels and high gray levels. In the driving waveform, to stabilize the EWD at any initial grayscale (low gray levels/high gray levels), an exponential function waveform and an AC signal were used. Then, the grayscale conversion was performed by using an AC signal with a switching voltage to quickly achieve the target grayscale. Finally, another AC signal was used to stabilize the EWD at the target grayscale. A set of driving waveforms in grayscale ranging across four levels was designed using this method. According to the experimental results, oil backflow and the hysteresis effect could be effectively attenuated by the proposed driving waveforms. During conversion, the response speed of EWDs was boosted by at least 9.37% compared to traditional driving waveforms.

Combined‐harmonics wireless power transfer system

AbstractA technique for wireless power transfer (WPT) efficiency improvement by a proper design of the excitation waveform is presented. This improvement is obtained on the one hand by a combined‐harmonics excitation, and on the other hand by exploiting multiple‐resonance coupled resonators. In contrast to wireless communications, there is no constraint on the linearity of the transmitter and receiver in a WPT system. Therefore, the impact of the excitation waveform on the power transfer efficiency with the help of an analytical model is investigated. An optimum excitation waveform is determined to maximise the power transfer efficiency. Thereafter, the authors concentrate on designing a multiple‐resonance coupled resonator system that is consistent with the determined excitation waveform. This work introduces a non‐uniform spiral resonator for controlling the self‐resonant frequencies, which is consistent with the required excitation waveform. The performance of the designed coupled resonators is then evaluated using a 3D finite‐element method and experiments. The numerical simulation and experimental results are in good agreement, verifying the validity of our design.

Preparation of Bose-Einstein condensate of dysprosium atoms based on demagnetization cooling

In magnetic atomic gases, the dipolar relaxation process couples the system spin and kinetic degrees of freedom. When the average kinetic energy is significantly lower than the Zeeman splitting, the atoms predominantly occupy the lowest Zeeman state. As the Zeeman splitting approaches the average kinetic energy, some atoms transfer to adjacent Zeeman states through dipolar relaxation, converting kinetic energy into Zeeman energy. By utilizing optical pumping, atoms transferred to higher spin states can be repumped to the ground state, thereby achieving a continuous cooling cycle and effectively lowering the system’s temperature. As the energy removed in a single cooling cycle is much larger than the energy of scattered photons, this demagnetization cooling scheme significantly enhances cooling effciency and reduces atomic loss. In this work, we establish state-coupled equations that incorporate dipolar relaxation and optical pumping to analyze the demagnetization cooling process, modeling the evolution of atom number and temperature during the cooling of <inline-formula><tex-math id="M1">\begin{document}$^{164}{\text{Dy}}$\end{document}</tex-math></inline-formula> atoms. We develop a strategy to generate an optimal magnetic field waveform by maximizing the demagnetization rate. Based on this strategy, we investigate the influence of crucial experimental parameters on demagnetization cooling and determine their specific ranges for producing large atom number of BEC, including the optical dipole trap frequency, as well as the intensity and polarization purity of the optical pumping light. The results indicate that demagnetization cooling enables the direct preparation of a large number of dysprosium BEC with sub-second timescales, reducing the cooling time by an order of magnitude compared to conventional methods for dysprosium atoms. Furthermore, it could achieve a cooling effciency of <inline-formula><tex-math id="M2">\begin{document}$\chi \approx 44.92$\end{document}</tex-math></inline-formula>, an order of magnitude higher than that of traditional evaporative cooling.

Optimum Waveform Selection for Target State Estimation in the Joint Radar-Communication System

Optimum Waveform Selection for Target State Estimation in the Joint Radar-Communication System

JSMWO: Joint Radar Spectrum Management and Waveform Optimization Strategy for Maneuvering Target Tracking in Congested Spectrum Environment

JSMWO: Joint Radar Spectrum Management and Waveform Optimization Strategy for Maneuvering Target Tracking in Congested Spectrum Environment

Let It GUWO: Waveform Optimization for Angular Blanking and Robustification in a MIMO Dual-Functional Radar-Communication System

Let It GUWO: Waveform Optimization for Angular Blanking and Robustification in a MIMO Dual-Functional Radar-Communication System

Target-Oriented SAR Complementary Waveform Optimization for SCR Improvement

Target-Oriented SAR Complementary Waveform Optimization for SCR Improvement

HSD-WO:A Hybrid Stochastic-Deterministic Waveform Optimization Method for Joint Tracking and Anti-Interference

HSD-WO:A Hybrid Stochastic-Deterministic Waveform Optimization Method for Joint Tracking and Anti-Interference

FastPtx: a versatile toolbox for rapid, joint design of pTx RF and gradient pulses using Pytorch's autodifferentiation.

With modern optimization methods, free optimization of parallel transmit pulses together with their gradient waveforms can be performed on-line within a short time. A toolbox which uses PyTorch's autodifferentiation for simultaneous optimization of RF and gradient waveforms is presented and its performance is evaluated. MR measurements were performed on a 9.4T MRI scanner using a 3D saturated single-shot turboFlash sequence for [Formula: see text] mapping. RF pulse simulation and optimization were done using a Python toolbox and a dedicated server. An RF- and Gradient pulse design toolbox was developed, including a cost function to balance different metrics and respect hardware and regulatory limits. Pulse performance was evaluated in GRE and MPRAGE imaging. Pulses for non-selective and for slab-selective excitation were designed. Universal pulses for non-selective excitation reduced the flip angle error to an NRMSE of (12.3±1.7)% relative to the targeted flip angle in simulations, compared to (42.0±1.4)% in CP mode. The tailored pulses performed best, resulting in a narrow flip angle distribution with NRMSE of (8.2±1.0)%. The tailored pulses could be created in only 66s, making it feasible to design them during an experiment. A 90° pulse was designed as preparation pulse for a satTFL sequence and achieved a NRMSE of 7.1%. We showed that both MPRAGE and GRE imaging benefited from the pTx pulses created with our toolbox. The pTx pulse design toolbox can freely optimize gradient and pTx RF waveforms in a short time. This allows for tailoring high-quality pulses in just over a minute.

A Single Stage Photovoltaic Solar Pumping System based on the Three Phase Multilevel Inverter

This paper presents a study of a single-stage DC-AC converter for a solar water pumping application. The topology was based on solar panels connected to a new structure of a three-phase multilevel inverter through DC-bus capacitors. The inverter offers simplicity, requires fewer components compared to conventional ones, and provides optimal voltage and current waveforms with reduced harmonics, eliminating the need for filters. The applied control technique aimed to stabilize the input DC-bus voltage, extract the maximum power using a simple MPPT algorithm, and enhance the efficiency of the water pump through scalar V/f control, regardless of weather changes. A simulation was conducted using the PSIM software, considering a variable daily climate scenario. The results obtained demonstrate the efficiency of the system in extracting energy with optimal torque and current for the pump compared to a classic design based on a three-phase H-bridge inverter.

Numerical investigation on the performance enhancement of PEMFC with gradient sinusoidal-wave fins in cathode channel

As the cathode channel structure plays significant effects on the performance of the proton exchange membrane fuel cell (PEMFC), in this work, a 3D multi-phase model of PEMFC is established and effects of cathode channel structure (conventional channel, normal sinusoidal-wave fins and gradient sinusoidal-wave fins) on the performance of PEMFC are numerically investigated. Results indicate that the PEMFC with gradient sinusoidal-wave fins in cathode channel can achieve higher power density and more uniform membrane current density. This is due to that the gas velocity in cathode channel with gradient sinusoidal-wave fins is significantly increased, leading to better oxygen transport and liquid water removal. Furthermore, effects of the geometrical parameters of gradient sinusoidal-wave fins on the electricity generation performance, membrane current density, and mass fraction of oxygen and liquid water of PEMFC are analyzed and discussed. It is found that the optimum waveform depth growth rate and wavelength of the gradient sinusoidal-wave fins is 0.035 and 2.5 mm, respectively. At 0.5 V, the maximum power density of the PEMFC with gradient sinusoidal-wave fins is 5.3% higher than that of the PEMFC with conventional channel.

Practical Waveform-to-Energy Harvesting Model and Transmit Waveform Optimization for RF Wireless Power Transfer Systems

The received radio-frequency (RF) power in far-field RF wireless power transfer (WPT)—with or without simultaneous information transfer—is minuscule due to large propagation loss in wireless media. In such scenarios, adapting to the receiver characteristics by transmit waveform optimization is essential for maximizing the harvested direct current (dc) and, thus, the end-to-end efficiency of an RF WPT system. The receiver efficiency in RF WPT is governed by the RF-to-dc efficiency of the rectifier as well as the impedance mismatch at the antenna and load. In this article, we study the receiver efficiency for any fixed load and, subsequently, present a novel rectifier model that relates the average harvested dc power to the distribution, that is, the histogram, of the instantaneous power levels of the RF signal’s envelope over time. The proposed waveform-to-energy harvesting (EH) model enables us to anticipate the average harvested dc power for any waveform, including communication signals as well, given the knowledge of the power-level distribution. Consequently, we conduct rigorous waveform optimization to maximize the average harvested dc power and determine the digital baseband signal at the transmitter that does so, namely prove that a pulsed tone at appropriate frequency is optimal for RF WPT. We present a multiband test-bed for determining the receiver efficiency for any digital baseband waveform. The efficacy of the proposed model is corroborated through experiments as well as simulations, which confirm that it is operational as well as accurate in practice and that single-sine pulses yield higher efficiency than basic multisine waveforms, while a pulsed phase shift keying (PSK) is preferable for simultaneous wireless information and power transfer (SWIPT).

On the Innovation, Design, Construction, and Experiments of OMEGA-Based SSPS Prototype: The Sun-Chasing Project

This study systematically introduces the development of the world’s first full-link and full-system ground demonstration and verification system for the OMEGA space solar power satellite (SSPS). First, the OMEGA 2.0 innovation design was proposed. Second, field-coupling theoretical models of sunlight concentration, photoelectric conversion, and transmitting antennas were established, and a systematic optimization design method was proposed. Third, a beam waveform optimization methodology considering both a high beam collection efficiency and a circular stepped beam shape was proposed. Fourth, a control strategy was developed to control the condenser pointing toward the sun while maintaining the transmitting antenna toward the rectenna. Fifth, a high-efficiency heat radiator design method based on bionics and topology optimization was proposed. Sixth, a method for improving the rectenna array’s reception, rectification, and direct current (DC) power synthesis efficiencies is presented. Seventh, high-precision measurement technology for high-accuracy beam-pointing control was developed. Eighth, a smart mechanical structure was designed and developed. Finally, the developed SSPS ground demonstration and verification system has the capacity for sun tracking, a high concentration ratio, photoelectric conversion, microwave conversion and emission, microwave reception, and rectification, and thus satisfactory results were obtained.

Optimal waveform for fast synchronization of airfoil wakes

We obtain an optimal actuation waveform for fast synchronization of periodic airfoil wakes through the phase reduction approach. Using the phase reduction approach for periodic wake flows, the spatial sensitivity fields with respect to the phase of the vortex shedding are obtained. The phase sensitivity fields can uncover the synchronization properties in the presence of periodic actuation. This study seeks a periodic actuation waveform using phase-based analysis to minimize the time for synchronization to modify the wake shedding frequency of NACA0012 airfoil wakes. This fast synchronization waveform is obtained theoretically from the phase sensitivity function by casting an optimization problem. The obtained optimal actuation waveform becomes increasingly non-sinusoidal for higher angles of attack. Actuation based on the obtained waveform achieves rapid synchronization within as low as two vortex shedding cycles irrespective of the forcing frequency, whereas traditional sinusoidal actuation requires ${O}(10)$ shedding cycles. Further, we analyse the influence of actuation frequency on the vortex shedding and the aerodynamic coefficients using force-element analysis. The present analysis provides an efficient way to modify the vortex lock-on properties in a transient manner with applications to fluid–structure interactions and unsteady flow control.

Model-based optimal action selection for Dyna-Q reverberation suppression cognitive sonar

The Doppler shift of low-speed targets is frequently disturbed by the reverberation Doppler spread clutter under the shallow sea. The clutter is generated by underwater scatterers, which increases the difficulty of Doppler estimation. To solve this problem, a reverberation target resolution function based on the Doppler spread clutter statistical model is proposed in this paper. Through the width of reverberation Doppler clutter, this function adjusts the waveform parameters by determining whether the target is discriminable. In addition, the reverberation Doppler spread clutter is time-spatial varying and affected by grazing angle, waves, wind speed, fish and other effects. Thus, the sonar waveform parameters need to be adjusted constantly. Therefore, this paper combines the cognitive sonar based on reinforcement learning with the reverberation target resolution function to evaluate different waveforms in different environments. Consequently, the sonar can adjust the waveform parameters in real-time and obtain the optimal waveform in different environments. Meanwhile, in this paper, the action selection strategy of Dyna-Q reinforcement learning is optimized, and the model-based maximum action selection Dyna-Q algorithm (Dyna-Q-Max-Action) is proposed. Compared with the traditional Dyna-Q and Q-learning algorithms, the proposed algorithm needs fewer episodes. Finally, numerical simulation verified the effectiveness of the proposed algorithm.

A Novel MIMO Radar Orthogonal Waveform Design Algorithm Based on the Multi-Objective Improved Archimedes Optimization Algorithm

Realization and enhancement of detection techniques for multiple-input–multiple-output (MIMO) radar systems require polyphase code sequences with excellent orthogonality characteristics. Therefore, orthogonal waveform design is the key to realizing MIMO radar. Conventional orthogonal waveform design methods fail to ensure acceptable orthogonal characteristics by individually optimizing the autocorrelation sidelobe peak level and the cross-correlation sidelobe peak level. In this basis, the multi-objective Archimedes optimization algorithm (MOIAOA) is proposed for orthogonal waveform optimization while simultaneously minimizing the total autocorrelation sidelobe peak energy and total cross-correlation peak energy. A novel optimal individual selection method is proposed to select those individuals that best match the weight vectors and lead the evolution of these individuals to their respective neighborhoods. Then, new exploration and development phases are introduced to improve the algorithm’s ability to increase its convergence speed and accuracy. Subsequently, novel incentive functions are formulated based on distinct evolutionary phases, followed by the introduction of a novel environmental selection method aimed at comprehensively enhancing the algorithm’s convergence and distribution. Finally, a weight updating method based on the shape of the frontier surface is proposed to dynamically correct the shape of the overall frontier, further enhancing the overall distribution. The results of experiments on the orthogonal waveform design show that the multi-objective improved Archimedes optimization algorithm (MOIAOA) achieves superior orthogonality, yielding lower total autocorrelation sidelobe peak energy and total cross-correlation peak energy than three established methods.