Angle Modulation Research Articles

Golden Angle Modulation Aided Fractional Spatial Modulation: System Design and Performance Optimization

Golden Angle Modulation Aided Fractional Spatial Modulation: System Design and Performance Optimization

Fast-scanning speed single-photon counting LiDAR based on front focal length modulation.

This Letter presents a method for fast-scanning speed LiDAR based on front focal length modulation in the transmitter, which compensates for the influence of the laser divergence angle on the scanning speed at close range of the long-range LiDAR. According to the thin lens equation for Gaussian beams, the laser divergence angle is affected by the distance from the lens to the object (the waist of the laser beam). The scanning speed of the LiDAR is correlated to the laser divergence angle during LiDAR operation, and the scanning speed can be improved by expanding the laser divergence angle by enlarging the front focal length of the transmitter. Through experimental analysis, the laser dispersion angle modulation of LiDAR can improve the scanning speed under the premise of guaranteeing the target detection performance in close-range detection.

Pretilt angle modulation of liquid crystals based on single crystal rubrene with incorporation of homeotropic polyimides

The alignment control of liquid crystals (LCs) is critical for various practical applications. The pretilt angle modulation of LCs typically requires a mechanical rubbing on substrates to orient the LCs. This study presents a contact-free approach to achieve pretilt angle modulation of LCs. Initially, a single crystal rubrene (SCR) film is deposited on the substrate. Subsequently, a mixture of nematic LCs and homeotropic polyimides (HPIs) is introduced between two SCR substrates via capillary action. During capillary filling, the synergy of capillary flow and the interaction between LCs and SCR ensures specific LC orientation. Subsequently, HPI dopants migrate toward and organize on the SCR through vertical phase separation, enhancing surface hydrophobicity and thereby increasing the pretilt angle of LCs. The pretilt angle of LCs can be continuously adjusted over a wide range from 2° to 90° by varying the HPI concentration. The contact-free process preserves against electrostatic charges, dust contamination, and surface damage typical of rubbed LC cells. This believed to be novel technique shows promise for developing no-bias-bend and bistable bend-splay LC displays.

REDUCTION OF POTENTIAL RADIOLOGICAL RISKS FOR PATIENTS UNDERGOING DIAGNOSTIC EXAMS THROUGH MODIFICATION OF THE X-RAY SPECTRUM

The diagnostic medical practice using X-rays significantly contributes to the collective dose worldwide, where the inherent risk in each examination is proportional to the absorbed dose, which is related to deterministic and stochastic effects of ionizing radiation. Therefore, due to the necessity of optimizing each radiological procedure, this study aimed to reduce the absorbed dose in patients undergoing X-ray examinations by evaluating each parameter that modifies the spectral distribution. The Birch and Marshall method was employed to reconstruct and modify the X-ray spectra based on tube voltage, filtration, tube current, anode angle, and energy fluence modulation. By modifying these parameters, it was possible to reduce the absorbed dose in the patient’s skin by up to 38%. The proposed methodology is feasible for implementation in clinical centers, given the availability of copper filters incorporated into X-ray equipment. Additionally, an alternative technique involving tantalum filters is presented, achieving a reduction in absorbed dose of up to 57%. Thus, with the developed methodology, it is demonstrated that it is possible to reduce radiation doses by modifying spectral distributions, reproducing medical images with a significant reduction in the absorbed dose to the patient, while ensuring quality and safety in X-ray diagnostic procedures.

Golden Angle Modulation Aided Differential OFDM-IM for LEO Satellite Communications

Golden Angle Modulation Aided Differential OFDM-IM for LEO Satellite Communications

Contact Angle Modulation: In Situ Polymer Deposition during Sessile Drop Evaporation.

The drying kinetics of a sessile drop on a solid surface are a widely studied phenomenon because of their relevance to various fields such as coating, printing, medical diagnostics, sensing, and microfluidic technology. Typically, the drop undergoes drying either at a constant contact radius (R) with a decrease in the three-phase contact angle or at a constant contact angle (θ) with a reduction in the radius with time. These two drying modes are referred to as CCR and CCA, respectively. It is not uncommon where both R and θ may decrease during drying, especially in the penultimate stage of drying. In this work, we report a scenario wherein the θ increases while R decreases during the drying process of an aqueous polymer solution on a high surface energy substrate. This behavior is observed across different polymer systems (such as poly(ethylene oxide) and polyvinyl pyrrolidine), varying molecular weights, and polymer concentrations. As the drop dries, the polymer gets deposited at the three-phase contact line, thus reducing the surface energy of the substrate and leading to an increase in the contact angle. The drop responds by attempting to reach a new equilibrium contact angle through slipping. The temporal increase in contact angle follows a power law scaling behavior. This study demonstrates an in situ modulation of contact angle facilitated by evaporation and polymer deposition, showcasing unconventional drying dynamics.

R-LRBPNet: A Lightweight SAR Image Oriented Ship Detection and Classification Method

Synthetic Aperture Radar (SAR) has the advantage of continuous observation throughout the day and in all weather conditions, and is used in a wide range of military and civil applications. Among these, the detection of ships at sea is an important research topic. Ships in SAR images are characterized by dense alignment, an arbitrary orientation and multiple scales. The existing detection algorithms are unable to solve these problems effectively. To address these issues, A YOLOV8-based oriented ship detection and classification method using SAR imaging with lightweight receptor field feature convolution, bottleneck transformers and a probabilistic intersection-over-union network (R-LRBPNet) is proposed in this paper. First, a CSP bottleneck with two bottleneck transformer (C2fBT) modules based on bottleneck transformers is proposed; this is an improved feature fusion module that integrates the global spatial features of bottleneck transformers and the rich channel features of C2f. This effectively reduces the negative impact of densely arranged scenarios. Second, we propose an angle decoupling module. This module uses probabilistic intersection-over-union (ProbIoU) and distribution focal loss (DFL) methods to compute the rotated intersection-over-union (RIoU), which effectively alleviates the problem of angle regression and the imbalance between angle regression and other regression tasks. Third, the lightweight receptive field feature convolution (LRFConv) is designed to replace the conventional convolution in the neck. This module can dynamically adjust the receptive field according to the target scale and calculate the feature pixel weights based on the input feature map. Through this module, the network can efficiently extract details and important information about ships to improve the classification performance of the ship. We conducted extensive experiments on the complex scene SAR dataset SRSDD and SSDD+. The experimental results show that R-LRBPNet has only 6.8 MB of model memory, which can achieve 78.2% detection accuracy, 64.2% recall, a 70.51 F1-Score and 71.85% mAP on the SRSDD dataset.

ВЛИЯНИЕ ПЕРИОДИЧЕСКОЙ МОДУЛЯЦИИ УГЛА НАНЕСЕНИЯ ВОЛЬФРАМОКСИДНЫХ СЛОЕВ ПРИ МАГНЕТРОННОМ НАПЫЛЕНИИ НА ИХ ЭЛЕКТРИЧЕСКИЕ ХАРАКТЕРИСТИКИ

Submicron tungsten oxide (WO3) layers of 50-250 nm thickness were obtained by magnetron deposition. The resulting films structure was adjusted in the course of magnetron sputtering using a method based on the modulation of electrochromic tungsten oxide (VI) deposition angle developed in our earlier studies. The prepared WO3 layers were used for the manu-facture of electrochromic devices which electrical characteristics were studied by cyclic volt-amper¬ometry using a three-electrode connection scheme. Based on the obtained data, coefficients of Li+ ions diffusion were calculated and found to follow an ex¬treme dependence upon the speed of tungsten oxide deposition angle modulation with a maximum at speed about 1.2 rpm.

Adaptive Angle Module and Radian Regression Method for Rotated Object Detection

Adaptive Angle Module and Radian Regression Method for Rotated Object Detection

Enhancing microstructure and device performance of InGaN quantum dot micro-LEDs through substrate off-cut angle modulation

InGaN quantum dots (QDs) are regarded as a compelling candidate material for the fabrication of high-quality GaN-based micro-LEDs. In this work, to study the impact of a substrate structure on InGaN QDs and QD-based micro-LEDs, GaN-on-sapphire substrates with off-cut angles toward the a-axis of 0.2°, 0.4°, and 0.7° were utilized as templates for the fabrication of InGaN QDs and InGaN QDs-based micro-LEDs. Experimental results show that GaN template with 0.4° off-cut angle exhibits the narrowest terrace width and enables InGaN QDs to be higher and more uniform. The InGaN QD sample grown on 0.4° substrate has a very small wavelength shift of 2.5 nm with temperature increasing and owns the longest photoluminescence peak wavelength implying the highest In content. Furthermore, electroluminescence (EL) spectra demonstrate that QD-based micro-LED array has excellent wavelength stability under various injection currents, and the stability can be improved further on a GaN template with narrower terraces. The results indicate that altering the terrace width of GaN template is a feasible scheme for improving the properties of GaN-based micro-LEDs.

Golden Angle Modulation Aided OFDM-IM for an Arbitrary Number of Subcarriers

Golden Angle Modulation Aided OFDM-IM for an Arbitrary Number of Subcarriers

Research and design of a metasurface with an extended depth of focus in the near field.

A metasurface with an extended depth of focus has broad application prospects in security detection. However, in the near field, the simulation results obtained by using traditional methods to achieve an extended depth of focus have a significant deviation from the preset value. This paper discusses the relationship between the depth of focus and focusing position, and the reason why the simulation results deviate from the preset focus position in the radial modulation method. The angle modulation method is found by a simulation. A more accurate method for an extended depth of focus was proposed by combining the radial modulation method with the quasi-optical path principle. Finally, a polarization-insensitive reflective metasurface element was designed, and elements were arranged to form a polarization-insensitive focus between 150 and 400mm based on the focusing effect settings. The simulation results indicate that the metasurface achieves the same focusing effect between 175 and 425mm when different linear-polarization waves are incident. This focus is greater and more accurate than the radial modulation method under the same conditions, which indicates that the method is superior to the radial modulation method in the near-field region. The simulation verifies the accuracy of the method and shows potential application prospects in fields such as microwave imaging.

A Design of Low-Projection SCMA Codebooks for Ultra-Low Decoding Complexity in Downlink IoT Networks

This paper conceives a novel sparse code multiple access (SCMA) codebook design which is motivated by the strong need for providing ultra-low decoding complexity and good error performance in downlink Internet-of-things (IoT) networks, in which a massive number of low-end and low-cost IoT communication devices are served. By focusing on the typical Rician fading channels, we analyze the pair-wise error probability of superimposed SCMA codewords and then deduce the design metrics for multi-dimensional constellation construction and sparse codebook optimization. For significant reduction of the decoding complexity, we advocate the key idea of projecting the multi-dimensional constellation elements to a few overlapped complex numbers in each dimension, called low projection (LP). An emerging modulation scheme, called golden angle modulation (GAM), is considered for multi-stage LP optimization, where the resultant multi-dimensional constellation is called LP-GAM. Our analysis and simulation results show the superiority of the proposed LP codebooks (LPCBs) including one-shot decoding convergence and excellent error rate performance. In particular, the proposed LPCBs lead to decoding complexity reduction by at least 97% compared to that of the conventional codebooks, whilst owning large minimum Euclidean distance. Some examples of the proposed LPCBs are available at https://github.com/ethanlq/SCMA-codebook.

Controlling charge transport in HgTe topological insulator by dual-electrical modulations

Heterostructure transport properties is investigated theoretically based on two-dimensional planar HgTe/CdTe quantum wells structure by a dual-gate modulations. Two voltage gates is deposited on the top of the heterostructure to create the corresponding electrical modulation potential. The electron transport property is explored by calculating the transmission spectrum by tuning the incidence angle, Fermi energy and electrical modulation potential. It is demonstrated that the transmission probability can be effectively tuned by changing the incidence angle, gate voltage and Fermi energy. Our findings pave the way for possible future applications of topological insulator-based devices.

Boosted sodium ion storage performance in MnO2: Understanding the bond angle-mediated orbital overlap in MnO6 units for fast charge transfer

Symmetric six oxygen-coordinated Mn structural units (MnO6) in MnO2 with small Mn–O orbital overlap hamper electron transfer rates during energy storage. Herein, we report a novel bond angle modulation strategy to manipulate Mn–O orbital overlap in MnO2 through the construction of Mn vacancies (MnO2-VMn), aiming at expediting electron transfer, and thus enhancing energy storage performance. Both experimental and theoretical results disclose that the amplification of Mn–O–Mn bond angles exclusively augments the Mn (dx2-y2)-O (py) orbital overlap and triggers the electron redistribution in MnO2-VMn, inducing an augmented Mn dx2-y2 electron occupation. This heightened presence of active electrons in the Mn dx2-y2 orbital paves the way for accelerating electron transfer and ion transfer in MnO2-VMn. Notably, MnO2-VMn delivers an improved specific capacitance of 425 F g−1 at 1 A g−1 and a superior rate capacity of 265 F g−1 at 20 A g−1. Furthermore, an asymmetric supercapacitor (MnO2-VMn//AC ASC) was fabricated, exhibiting a high energy density of 64.3 Wh kg−1 at a power density of 1000 W kg−1. Furthermore, theoretical insights uncover the profound implications of metal–oxygen–metal bond angle regulation on interatomic orbital overlap modulation. These revelations illuminate pathways for the design of advanced energy storage materials.

Oriented Object Detection in Remote Sensing Using an Enhanced Feature Pyramid Network

Object detection in remote sensing images is a critical task within the field of remote sensing image interpretation and analysis, serving as a fundamental foundation for military surveillance and traffic guidance. Recently, although many object detection algorithms have been improved to adapt to the characteristics of remote sensing images and have achieved good performance, most of them still use horizontal bounding boxes, which struggle to accurately mark targets with multiple angles and dense arrangements in remote sensing images. We propose an oriented bounding box optical remote sensing image object detection method based on an enhanced feature pyramid, and add an attention module to suppress background noise. To begin with, we incorporate an angle prediction module that accurately locates the detection target. Subsequently, we design an enhanced feature pyramid network, utilizing deformable convolutions and feature fusion modules to enhance the feature information of rotating targets and improve the expressive capacity of features at all levels. The proposed algorithm in this paper performs well on the public DOTA dataset and HRSC2016 dataset, compared with other object detection methods, and the detection accuracy AP values of most object categories are improved by at least three percentage points. The results show that our method can accurately locate densely arranged and dynamically oriented targets, significantly reducing the risk of missing detections, and achieving higher levels of target detection accuracy.

The Beta‐Pochhammer and its application to arbitrary threshold phase error probability of a vector in Gaussian noise

This paper develops a calculus around a new β‐Pochhammer symbol of two variables, (a,b)m,n based on the Beta weighting . The approach is a natural rising factorial formulation that offers a new way to express hypergeometric functions of two variables. The results are implemented to solve the problem of finding the phase error probability of a vector perturbed by Gaussian noise with an arbitrary phase threshold in closed form for the first time, in terms of the incomplete confluent hypergeometric function 1ℱ1. This has been an unresolved problem in angle modulation dating back to the 1950s. Closed‐form solutions are developed around the lower and upper incomplete Humbert second Φ2 confluent hypergeometric function of two variables using the new incomplete β‐Pochhammer calculus.

A unified bit-to-symbol mapping for generalized constellation modulation

Gray mapping is a well-known way to improve the performance of regular constellation modulation, but it is challenging to be applied directly for irregular alternative. To address this issue, in this paper, a unified bit-to-symbol mapping method is designed for generalized constellation modulation (i.e., regular and irregular shaping). The objective of the proposed approach is to minimize the average bit error probability by reducing the hamming distance (HD) of symbols with larger values of pairwise error probability. Simulation results show that the conventional constellation modulation(i.e., phase shift keying and quadrature amplitude modulation (QAM) with the proposed mapping rule yield the same performance as that of classical gray mapping. Moreover, the recently developed golden angle modulation (GAM) with the proposed mapping method is capable of providing around 1 dB gain over the conventional mapping counterpart and offers comparable performance to QAM with Gray mapping.

Axisymmetrical resonance modes in an electrowetting optical lens.

Electrowetting-based adaptive optics are of great interest for applications ranging from confocal microscopy to LIDAR, but the impact of low-frequency mechanical vibration on these devices remains to be studied. We present a simple theoretical model for predicting the resonance modes induced on the liquid interface in conjunction with a numerical simulation. We experimentally confirm the resonance frequencies by contact angle modulation. They are found to be in excellent agreement with the roots of the zero-order Bessel functions of the first kind. Next, we experimentally verify that external axial vibration of an electrowetting lens filled with density mismatched liquids ( = 250 kg/m3) will exhibit observable Bessel modes on the liquid-liquid interface. An electrowetting lens filled with density matched liquids ( = 4 kg/m3) is robust to external axial vibration and is shown to be useful in mitigating the effect of vibrations in an optical system.

Double Fano sensing mechanism of waveguide coupled surface plasma

Based on the optical properties of waveguide-coupled surface plasmon resonance, a sensor of surface plasmon coupled waveguide resonance with double discrete states generated by the upper and lower waveguide structures combined with prisms and Au films, respectively, is proposed. In this paper, the sensing structure is studied numerically and analytically, and the transmission characteristics of surface equipartition excitations are analyzed and elaborated in-depth in combination with the reflection angle spectrum, as well as the generation and evolution mechanism of dual Fano resonance at different incidence angles at fixed wavelengths. The structural model of Fano resonance sensing based on angle modulation is established, and the sensing characteristics are analyzed to produce electromagnetic field enhancement at low-angle Fano. The mathematical model between structural parameters and spectral performance is established using back propagation (BP) neural network, and the particle swarm optimization (PSO) algorithm is used to find the input structural parameters corresponding to the optimal performance, The results show that the quality factor of resonance (FOM) and sensitivity is significantly improved; When it is used in the field of biosensing, the response curves of Fano with different angles of high and low to concentration are quite different, thus realizing high precision detection of different concentrations of solutions and reflecting excellent sensing performance.