Array Structural Parameters Research Articles

Direction of Arrival Joint Prediction of Underwater Acoustic Communication Signals Using Faster R-CNN and Frequency–Azimuth Spectrum

Utilizing hydrophone arrays for detecting underwater acoustic communication (UWAC) signals leverages spatial information to enhance detection efficiency and expand the perceptual range. This study redefines the task of UWAC signal detection as an object detection problem within the frequency–azimuth (FRAZ) spectrum. Employing Faster R-CNN as a signal detector, the proposed method facilitates the joint prediction of UWAC signals, including estimates of the number of sources, modulation type, frequency band, and direction of arrival (DOA). The proposed method extracts precise frequency and DOA features of the signals without requiring prior knowledge of the number of signals or frequency bands. Instead, it extracts these features jointly during training and applies them to perform joint predictions during testing. Numerical studies demonstrate that the proposed method consistently outperforms existing techniques across all signal-to-noise ratios (SNRs), particularly excelling in low SNRs. It achieves a detection F1 score of 0.96 at an SNR of −15 dB. We further verified its performance under varying modulation types, numbers of sources, grating lobe interference, strong signal interference, and array structure parameters. Furthermore, the practicality and robustness of our approach were evaluated in lake-based UWAC experiments, and the model trained solely on simulated signals performed competitively in the trials.

Numerical investigations on influence of spacing of tidal current turbine array

In order to maximize the energy extraction potential from the marine resource, the primary task is to improve the power generation efficiency of multi-unit turbine arrays. There are many factors that affect the power generation efficiency of hydro turbine arrays. This paper mainly studies the influence of the effects of array structure parameters on the flow structure of the near-wake flow field and the energy utilization. The numerical simulation results are compared with the experimental data to verify the reliability of the numerical model. The double-row staggered arrangement of the turbine array is selected, and the size of the array structure parameter, the horizontal distance Dx and the vertical distance Dy, is changed to calculate a series of working conditions. The analysis of the results shows that when the horizontal distance Dx is 2.5RD and the vertical distance Dy is 2RD, the energy efficiency of the turbine array will reach the highest.

High-efficient electron collection capability of graded Al compositional GaN nanowire arrays cathode

Based on the purpose of solving the “secondary absorption” of adjacent nanowires and the lateral emission in the GaN nanowire arrays (NWAs) cathode, an exponential-doping and graded Al compositional GaN NWAs photocathode is proposed, which could generate internal electric field to increase the quantum efficiency (QE) of top surface, and the introduction of an external electric field promote the side-emission electrons to shift toward the collecting side. The QE and collection efficiency (CE) of exponential-doping and graded compositional GaN NWAs under different array structure parameters, incident angles and external electric field intensities are analyzed. The results show that although the collection ratio of emitted electrons in the exponential-doping GaN NWAs is higher, the graded Al compositional photocathode with a stronger built-in electric field can obtain better CE under the application of an external electric field, and the peak value can reach 33.2% in a specific structure. External electric field has a more significant effect on the CE of uniform-doping GaN NWAs. The solutions provided in this study can make the GaN NWAs photocathode more suitable for the strict requirements of vacuum electron sources

Arbitrary Microphone Array Optimization Method Based on TDOA for Specific Localization Scenarios.

Various microphone array geometries (e.g., linear, circular, square, cubic, spherical, etc.) have been used to improve the positioning accuracy of sound source localization. However, whether these array structures are optimal for various specific localization scenarios is still a subject of debate. This paper addresses a microphone array optimization method for sound source localization based on TDOA (time difference of arrival). The geometric structure of the microphone array is established in parametric form. A triangulation method with TDOA was used to build the spatial sound source location model, which consists of a group of nonlinear multivariate equations. Through reasonable transformation, the nonlinear multivariate equations can be converted to a group of linear equations that can be approximately solved by the weighted least square method. Then, an optimization model based on particle swarm optimization (PSO) algorithm was constructed to optimize the geometric parameters of the microphone array under different localization scenarios combined with the spatial sound source localization model. In the optimization model, a reasonable fitness evaluation function is established which can comprehensively consider the positioning accuracy and robustness of the microphone array. In order to verify the array optimization method, two specific localization scenarios and two array optimization strategies for each localization scenario were constructed. The optimal array structure parameters were obtained through numerical iteration simulation. The localization performance of the optimal array structures obtained by the method proposed in this paper was compared with the optimal structures proposed in the literature as well as with random array structures. The simulation results show that the optimized array structure gave better positioning accuracy and robustness under both specific localization scenarios. The optimization model proposed could solve the problem of array geometric structure design based on TDOA and could achieve the customization of microphone array structures under different specific localization scenarios.

Terahertz radiation generation and shape control by interaction of array Gaussian laser beams with plasma

In the present paper, a scheme for generation of terahertz (THz) radiation in electron-neutral collisional plasma based on beating of two Gaussian laser array beams has been proposed. It is shown that the efficiency of THz radiation based on the Gaussian laser array beams can be enhanced drastically in comparison with the efficiency of THz radiation based on the Gaussian one. Furthermore, the producing THz radiation by the Gaussian laser array beams, which has an exclusive field profile, is affected by some array structure parameters. It can also be used to overcome the negative consequences of electron neutral collisions in plasma, which may be occurring in the THz radiation generation process. Optimizing the collisional plasma, laser beams and array structure parameters, THz radiation efficiency up to 0.07% can be obtained in our scheme which is about three times greater than the maximum efficiency obtained for standard (single) Gaussian laser beam. Also, considering the electrostatic energy channel in solving the THz wave equation, and reduction of THz radiation efficiency to 0.054%, in this assumption, the ratio between the efficiency of Gaussian laser array beams and standard Gaussian laser beam remained unchanged.

A Double-Layer Shaped-Beam Traveling-Wave Slot Array Based on SIW

A double-layer shaped-beam traveling-wave slot array based on substrate integrated waveguide (SIW) at $X$ -band is presented. The double-layer SIW longitudinal slot-coupled cavity slot is proposed as the array element, which has an improved bandwidth performance due to the double-resonant feature. By using this kind of slots, a planar nonuniformly spaced shaped-beam traveling-wave array is constructed. To achieve the desired distribution for the shaped-beam pattern, an efficient optimization method, with the mutual coupling effect being considered, is proposed to optimize the array structure parameters. Experimental results show that the array achieves good shaped-beam pattern in a 4.8% frequency band and low-loss characteristic.

Library based macro-modeling methodology for Through Silicon Via (TSV) arbitrary arrays

In this paper, a novel library-based macro-modeling technique is developed to extract equivalent RLGC model which is spice compatible for TSV arrays of any size N×M. The built model accounts for Through Silicon Via (TSV) parasitic dependence on the array structural parameters and the frequency dependent properties of the silicon substrate. The developed macro-model constructs an equivalent parasitic matrix that could be used by circuit simulators to estimate the maximum signal frequency as well as noise in the TSV array. The key idea of the macro-model is to partition any given TSV arrays into smaller and fixed-size arrays. Smaller arrays are characterized and their parasitic are stored in the library. Using a divide and conquer technique, the final solution of the TSV array is produced. A detailed comparison of the proposed macro-modeling technique against the parasitic extracted by microwave simulation, for different structures with different sizes, shows a maximum error of 10% and an average error of 5%. Furthermore, the performance of library based macro-modeling is order of magnitude faster than the microwave simulation.

DRAM Yield Analysis and Optimization by a Statistical Design Approach

In this paper the electric yield of DRAM core circuits is investigated by means of a statistical approach that incorporates a hierarchical linear Gaussian model for the DRAM core sensing process and a lognormal distribution model for the DRAM cell leakage. Analytical yield expressions are obtained and found to be dominated by two independent sources-either the lognormal distribution of the cell leakage components or the Gaussian distribution depending on the array structural parameters, parasitic, and the sense amplifier offset voltage. Analytical yield analysis is conducted for several different DRAM architectures and compared to measurements from signal margin analysis and data retention tests. The yield model is found to be very accurate. Thanks to the short computation time, it can be easily applied to the analysis and yield optimization of novel array structures, DRAM cell leakage analysis, sense amplifier offset voltage requirements, and core supply voltage optimization. It also paves the way for the design for yield of other memory circuits.

Scattering Property and Emissivity of a Periodic Pyramid Array Covered With Absorbing Material

Remote sensing systems must be calibrated before use, so the accuracy of calibration source has a significant effect on the property of the whole remote sensing system. In this paper, calibration sources constructed of a periodic metallic pyramid array covered with absorbing material are studied for remote sensing systems working in the microwave band. The scattering properties of this kind of calibration source are first analyzed by the Floquet theory and the spatial harmonic method. Then, the finite-difference time-domain method is used to simulate the calibration source structure to obtain the scattered field and the corresponding differential scattering coefficient. By integrating the scattering coefficient, the emissivity is finally obtained. The relationships between the emissivity and the pyramid array structural parameters, and the electromagnetic parameters of the covering material are given.

The transient scattering mechanism of dipole array with reflector

The transient backscattering mechanisms of a dipole array with reflector have been investigated from different aspects: time-domain, frequency-domain, and combined time-frequency domain, using 4 × 8 dipole arrays with reflector as an example. The data of scattering from the arrays under the incidence of Gaussian pulses are obtained by finite differential time domain method. The influences of the array structural parameters, incident wave parameters, and incident angles on the waveforms, spectrum, and time-frequency representations of the backscattered fields of the arrays are analysed and conclusions are drawn. From these characteristics and conclusions, it is possible to deduce the array structure inversely from the backscattered field.

Optimizing Write Current and Write Power Consumption in Magnetoresistive Random Access Memories by Using Generalized Asteroid Curves

Theoretical expressions for minimizing write current and write power consumption in magnetoresistive random access memories (MRAMs) are presented. The expressions are derived based on a generalized asteroid curve which approximately represents the minimum switching magnetic fields of magnetic tunnel junction (MTJ) memory cells recently developed for smaller write currents and better cell selectivity. The generalized asteroid curve has a shape parameter to fit the curve to the switching characteristics of MTJ cells. The derived expressions contain the shape parameter as well as other cell and array structural parameters, and thus give theoretical limits of the write current and power from physical points of view including MTJ shape.

Design of a multimesa IMPATT diode array optimise for maximum heat dissipation

It is shown that an appreciable increase in the dissipation capabilities of an IMPATT diode, can be achieved by making it in the form of a multimesa array structure on a common substrate, which forms the cathode connection. The anode of each mesa diode, is connected through an integrated gold heatsink to a common large external copper heatsink. A complete thermal analysis is performed by numerical technique from which the full temperature map of this composite device is obtained, as function of time in the heating up transient period, and under steady state operation. The analysis takes into consideration, the nonlinearity introduced by the local temperature dependence of the breakdown voltage of each separate mesa diode in the array, which, in turn, controls the current and heat dissipation distribution across the array. From the maximum temperature and the total power dissipation, the thermal resistance is obtained. The dependence of the thermal properties on various array structural parameters, e.g. the number of mesa diodes or the spacing between them, is evaluated. It is shown that by the use of nonuniform spacing, an almost uniform temperature can be achieved across the array device, thus yielding a minimum thermal resistance. It is also shown that even though an increased intermesa spacing in a uniformly arranged array, involves increased parasitic parallel capacitance, there is an optimum spacing that maximises the power-frequency-reactance product (P2f2X) of the device.