Search Results (803)

This paper presents a compact fractal-based super-wideband multiple-input multiple-output (MIMO) antenna for millimeter-wave (mmWave) 5G new radio (NR) and prospective 6G applications. The MIMO system comprises four Koch fractal monopole elements integrated with a modified shared ground plane. By adopting the second Koch iteration, the antenna achieves enhanced impedance bandwidth and stable radiation behavior compared with lower-order iterations. The elements are arranged in a polarization-diversity configuration within a 30 × 30 mm² footprint on a 0.8 mm-thick Rogers RO4835 substrate (ε_r = 3.5, δ = 0.0025). The proposed design provides an impedance bandwidth exceeding 14 GHz over 26.5–41 GHz, covering key bands at 28, 32, 38, and 40 GHz, while maintaining high inter-element isolation (around 30 dB over the operating range). The optimized ground modification enables a fully connected common ground and suppresses mutual coupling without additional decoupling structures. The antenna achieves 4–6 dBi realized gain with radiation efficiency exceeding 95%. MIMO performance metrics, including the envelope correlation coefficient (ECC), mean effective gain (MEG), and diversity gain (DG), confirm excellent diversity characteristics. The antenna is further evaluated under bending, demonstrating stable matching and isolation for conformal and wearable scenarios, and the concept is extendable to a non-planar 12-port configuration within the same footprint. Measured results agree well with simulations, validating the proposed design for wideband mmWave 5G/6G devices. Full article

Holotrichia parallela is a globally distributed soil-dwelling pest that poses a major threat to peanut cultivation in China. Neuropeptides, as critical signaling molecules, regulate multiple physiological and behavioral processes in insects and represent highly promising targets for pest management. To date, the functional characteristics of neuropeptides in H. parallela remain unreported. In this study, we isolated and cloned one NPF and one NPFR gene, respectively. Bioinformatics analysis revealed that alternative splicing of the NPF gene produces two transcript variants, NPFa (255 bp) and NPFb (369 bp). The NPFR gene spans a length of 1188 bp, encoding 395 amino acids that contain seven α-helical transmembrane domains, indicating that it belongs to the family A G protein-coupled receptor (GPCR) family. Spatiotemporal expression profiles demonstrated that NPF was most abundant in the adult brain, whereas NPFR was highly enriched in the brain and antennae. NPF expression peaked in second-to-third-instar larvae, while NPFR was highly expressed in eggs. Starvation stress significantly upregulated the expression of both genes. RNA interference (RNAi)-mediated silencing of NPF and NPFR significantly reduced food intake, female fecundity, and glycogen content in adults. These findings enhance our understanding of insect neuropeptides signaling networks and support the development of behavior-based pest control strategies. Full article

Wireless links in underground coal mines suffer from severe attenuation, blockage, and limited spatial coverage. To improve link quality under these conditions, we study a simultaneously transmitting and reflecting reconfigurable intelligent surface (STAR-RIS)-assisted system with multiple movable antennas (MAs) installed at the base station (BS) panel. Unlike prior models that assume a continuous movement box, we explicitly account for practical panel constraints: mechanical supports and RF feed lines partition the BS panel into non-overlapping irregular feasible subregions. This turns the BS-side antenna-positioning task into a mixed-integer nonlinear program (MINLP). We formulate a joint optimization problem that couples BS beamforming, STAR-RIS transmission/reflection coefficients, BS-side MA positions, and MA-to-subregion assignment with collision-avoidance constraints. To solve it, we adopt a block coordinate descent (BCD) framework: successive convex approximation (SCA) for beamforming, semidefinite relaxation (SDR)-based updates for STAR-RIS coefficients, and a penalty-based continuous relaxation for MINLP handling. The MA solver further integrates Hungarian initialization, cross-region jump updates, and reassignment corrections to escape poor local subregions. Simulation results in coal mine channel settings show that the proposed method yields a 66.7% sum-rate gain over fixed-antenna baselines and reduces required transmit power by 16.8 dB at the target-rate operating point. Compared with a regular-region BS-MA baseline, the irregular-partition design achieves an additional 5.6 dB power saving, demonstrating the practical value of hardware-aware geometry modeling. Full article

Extreme cyclic temperature fluctuations (−200 °C to 200 °C) and inherent clearance nonlinearity in deployment hinges severely threaten the on-orbit deployment accuracy and dynamic stability of large variable-geometry spacecraft antennas for geosynchronous Earth orbit applications. However, current modeling approaches suffer from three critical limitations: single-configuration models requiring manual switching, there are inherent geometric nonlinear errors from conventional floating frame formulations, and incomplete thermo-mechanical coupling neglects the temperature effects on contact stiffness and friction. To address these gaps, we propose a unified high-fidelity dynamic model based on the Absolute Nodal Coordinate Formulation (ANCF). This model eliminates geometric errors and mesh mismatch, enables seamless multi-configuration deployment without switching, and fully incorporates temperature-dependent material properties and nonlinear contact forces. An improved Hilber–Hughes–Taylor-$\alpha$ implicit integration algorithm with second-order accuracy and unconditional stability is adopted to solve the strongly nonlinear differential-algebraic equations. Numerical results demonstrate that the proposed model achieves a calculation error below 3% against experimental data, significantly outperforming the traditional floating frame of reference formulation with an error of 15–22%. Non-uniform temperature fields increase thermally induced vibration amplitudes by 32–45%, and every 0.1 increase in the friction coefficient raises the impact force at the clearance hinge by 15–20%. The proposed unified modeling framework provides a solid theoretical basis for deployment stability prediction and the on-orbit control optimization of large variable-geometry spacecraft antennas. Full article

This study explores the miniaturization of the Controlled Reception Pattern Antenna (CRPA) for Global Positioning System (GPS) receivers, addressing the challenge of mutual coupling, which adversely affects antenna performance. In this work, a miniaturized CRPA is designed and manufactured by using Rogers RO3006 substrate. To provide a performance benchmark, a four-element reference CRPA array was also designed with a 0.5 λ inter-element spacing, yielding an overall aperture size of 149.58 mm × 150.24 mm and a worst-case inter-element isolation larger than 14.4 dB. For the miniaturized CRPA, the target inter-element spacing was set to be 0.3 λ. To overcome isolation limitations, several coupling-mitigation techniques were developed and integrated into the miniaturized design. The final configuration consisted of a four-element CRPA, with each element rotated by 90° relative to its neighbor, inter-element slots incorporated into the shared ground-plane, and an individual ground plane segmentation to reduce surface–wave coupling. The proposed miniaturized CRPA achieved an overall footprint of 104.21 mm × 104.55 mm with the worst-case isolation exceeding 18.36 dB, surpassing the isolation performance of the reference array. This work demonstrates that it is possible to realize a compact CRPA with enhanced inter-element isolation by integrating tailored coupling suppression methods. Full article

The large-scale accumulation of coal gangue has created increasing environmental pressure, while its use as aggregate in cementitious materials remains limited by its high water absorption, porous structure and unstable mechanical performance. This study develops a machine learning-assisted multi-objective optimization framework for lightweight shotcrete incorporating surface-pretreated coal gangue aggregates and polyvinyl alcohol fibres. Two pretreatment methods—namely, silica-fume slurry coating (CGACM) and dry adsorption activation (CGACD)—were applied to improve the aggregate surface characteristics. Experimental data on compressive strength, splitting strength and density were used to train backpropagation neural networks and support vector machine and random forest models, with hyperparameters optimized by the Beetle Antennae Search algorithm. The trained models were then coupled with a multi-objective optimization procedure to balance mechanical performance, density, material cost and CO₂ emissions. The results show that surface pretreatment can improve the performance of coal gangue lightweight shotcrete, while the proposed optimization framework can identify mixture designs with balanced strength, reduced density and improved economic and environmental performance. Compared with untreated or non-optimized mixtures, the optimized surface-pretreated mixtures achieved a more favorable trade-off among mechanical, cost and carbon-emission objectives. This study provides a data-driven approach for the sustainable design and practical utilization of coal gangue in lightweight shotcrete. Full article

Diamond nitrogen-vacancy (NV) centers are regarded as promising microwave sensors owing to their excellent magnetic sensitivity, stability, and environmental compatibility. However, traditional confocal test platforms based on diamond NV centers are bulky, which limits their practical applications. In this paper, a fiber-coupled compact NV microwave magnetometer is designed that employs the continuous heterodyne measurement method and a fast Fourier transform to measure multiple microwave fields. We integrated the laser excitation module, microwave antenna module, and fluorescence collection module into a single unit, reducing the volume of the magnetometer to 13 cubic centimeters. By adjusting the frequency and power of the measured microwave signals, the applicability of the device under different frequency and power conditions was verified. Experimental tests show that the microwave magnetometer can simultaneously detect multiple microwave fields with different frequencies and power levels, achieving a frequency resolution on the order of millihertz (mHz) and a microwave detection sensitivity of 0.385 nT/Hz^1/2. These results demonstrate the magnetometer’s multi-microwave-field measurement capability, making it highly promising for applications such as microwave anomaly localization and medical diagnosis. Full article

In massive multiple-input multiple-output (MIMO) joint communication and sensing (JCAS) systems, hybrid beamforming (HBF) has attracted much attention because it can provide a favorable tradeoff between beamforming gain and hardware cost. However, HBF design in MIMO-JCAS systems is highly challenging. The main reasons are the strong coupling between the analog and digital precoders in joint communication-sensing optimization and the high-dimensional search space caused by large-scale antenna arrays. In this paper, a state-driven adaptive deep-unfolded hybrid beamforming algorithm is proposed for MIMO-JCAS systems. Specifically, the analog precoder update is redesigned in a manifold-based form to better match the geometry of the constant-modulus constraint, while the digital precoder update is enhanced by a learnable gradient-balancing mechanism to alleviate the dynamic imbalance between the communication-rate gradient and the sensing-error gradient. Furthermore, a lightweight state-driven control network is introduced to generate scaling factors for the hyperparameters according to the current iteration state, so that the unfolded model can adapt its update behavior during optimization. Different from conventional deep-unfolded methods with static hyperparameters during inference, the proposed method provides a more effective optimization strategy for the dynamic communication-sensing tradeoff in MIMO-JCAS hybrid beamforming. Simulation results demonstrate the effectiveness of the proposed state-driven adaptive deep-unfolded method. Compared with the conventional deep-unfolded projected gradient ascent (PGA) algorithm with 20 inner iterations, the proposed method improves the joint objective, while achieving faster convergence and stronger robustness. Full article

Large-aperture steerable reflector antennas are pivotal for deep-space exploration and satellite communication, but their high-frequency performance is often compromised by wind-induced structural deformations. This study employs a high-fidelity fluid–structure interaction (FSI) framework, coupling Computational Fluid Dynamics (CFD) and the Finite Element Method (FEM), to investigate the dynamic response of an 18 m Square Kilometre Array (SKA) antenna under transient wind loads. The structural FEM is validated against experimental modal data, ensuring the capture of essential vibration characteristics. We evaluate steady-state wind pressure coefficients ($C_p$) and transient responses under a simulated Davenport wind spectrum across the antenna’s full operational elevation range. Surface accuracy degradation is rigorously quantified using the Root Mean Square Error (RMSE) of the best-fit paraboloid. The results demonstrate a significant correlation between peak deformation and surface error, pinpointing 15° and 90° pitch angles as the most critical configurations for profile degradation due to the “air pocket effect” and asymmetric pressure distributions, respectively. These insights establish a robust theoretical basis for structural optimization and the development of active surface control strategies for next-generation aerospace signal acquisition infrastructure. Full article

Terahertz hot electron bolometer (HEB) mixers, which offer the highest sensitivity in the frequency range above 1.5 THz, are equipped on space observatories to detect the terahertz radiation emitted from the interstellar medium within galaxies. To increase the mapping speed, it is essential to develop large HEB mixer arrays. However, conventional quasi-optical coupling methods, including single large silicon lens approaches and silicon lens array approaches, suffer from the conflict of achieving high filling factor and uniform illumination on the HEB mixer array. This paper reviews the research progress on quasi-optical coupled HEB mixer arrays and proposes an innovative array coupling scheme to overcome the existing limitation. We designed a metasurface beam shaper based on the Gerchberg–Saxton algorithm and COMSOL simulation to transform an incoming Gaussian beam into a flattop beam in the focal plane, thereby forming uniform illumination for an antenna-coupled HEB mixer array. The metasurface is intended primarily for uniform local oscillator (LO) distribution across the array. The simulation of the metasurface beam shaper at 0.6 THz demonstrates a flattop beam with a flat region approximately 3 mm wide, and the intensity across this region varies by only 4.2%. The same simulation is also performed at 1.6 THz, and the flat region is 1.5 mm wide with a 5.5% intensity variation. This work demonstrates the feasibility of using a metasurface to convert a Gaussian beam into a flattop beam at terahertz frequencies as well as a pathway for array-level coupling schemes for HEB mixer arrays with high filling factor and uniform illumination. Full article

A single-band-notched ultra-wideband (UWB) low-sidelobe planar array antenna for millimeter-wave (mmWave) applications is presented. The antenna element employs a planar dipole excited through an H-shaped coupling slot to achieve broadband impedance matching, while a centrally loaded parasitic patch acts as a half-wavelength resonator to generate a controllable notch band. Additional parasitic patches are introduced to recover the high-frequency matching without degrading the notch response. An $8\times 8$ array is then developed using a Taylor-weighted feed network implemented with three classes of 1-to-4 microstrip power dividers. Measured results show that the array operates from 19.0 to 45.0 GHz with $\mathrm{VSWR}<2$, while providing a rejection band from 35.0 to 38.5 GHz. The notch suppresses the realized gain by about 5 dB around 37.0 GHz, the peak gain reaches 20.5 dBi in the passband, and average sidelobe levels better than $-17$ dB are obtained. The proposed design provides a practical approach for combining ultra-wide bandwidth, in-band interference rejection, and low-sidelobe radiation in a compact mmWave planar array. Full article

This paper presents a systematic qualification process for an electronic beam-steering antenna assembly for a low-Earth orbit (LEO) communication satellite. The transmitting/receiving antenna for the LEO communication satellite is based on a cavity-backed slot radiator, which has improved radiation efficiency and low mutual coupling compared to conventional PCB patch structures. In order to verify the electrical performance and reliability of the manual soldering process in a tightly spaced array structure with narrow element spacing and densely connected multi-channel RF modules, a reduced model was designed and fabricated and qualification tests were conducted under launch and on-orbit environments. The integration equipment was developed to ensure precise mechanical alignment and integration/disassembly between the radiating element arrays of the transmitting and receiving antenna modules and the RF modules, thereby establishing a manufacturability strategy for the antenna module and RF integrated module, which comprise a large array structure. Finally, the qualification tests of the transmitting and receiving antenna were performed to evaluate the structural and thermal stability considering the launch and orbital environments. The systematic qualification process proposed in this paper can be used in the development of the antenna system of the communication satellite. Full article

Metallic nanoantennas are promising structures for enhancing energy transfer in high-intensity laser–matter interactions, especially in nanoplasmonic-assisted fusion. Under ultrashort laser pulses, they generate strong localized fields, modify ionization dynamics, and significantly affect charge acceleration in dense media. In this work, we present a comprehensive particle-in-cell (PIC) study of gold nanoantennas of various geometries—dipoles, planar crosses, three-dimensional crosses, and Yagi-inspired planar structures—irradiated by near-infrared femtosecond pulses at intensities at a range of ~4 × 10¹⁷–4 × 10¹⁸ W/cm². The antenna structures are embedded in a dense hydrogen-rich medium, allowing us to follow electron emission, gold ionization, and proton acceleration self-consistently. Crossed and Yagi-type geometries exhibit more robust resonant behavior than dipoles, with higher field localization and greatly reduced sensitivity to incident polarization. The proton energies increase to ~200 keV at 4 × 10¹⁷ W/cm², and saturate around ~300 keV at a higher intensity >~4 × 10¹⁸ W/cm², dependent on the geometry. This happens largely due to a rapid loss of conduction electrons from the gold structures. Our results highlight Yagi-based and cross-based nanoantennas as promising resonant dopes for laser-driven energy coupling and point toward optimized multi-arm architectures for future nanofusion-target engineering applications. Full article

This paper introduces a compact MIMO antenna system designed for WLAN applications, offering dual polarization, strong isolation, and pattern diversity. The system includes two orthogonally positioned inverted-F antenna (IFA) elements operating in the 2.4 GHz WLAN band. To achieve polarization diversity, each element is designed and excited with a perpendicular feed. An L-shaped metallic parasitic element is placed close to the antennas to significantly reduce mutual coupling and enhance isolation. The antenna’s layout is straightforward and planar, making it easy to fabricate without requiring complex manufacturing steps. A prototype of the design was built and tested, and the experimental results show good agreement with simulated data. The fabricated antenna achieves a wide operating bandwidth from around 2.2 to 2.7 GHz and exhibits excellent port isolation, with S₂₁ better than −30 dB at 2.4 GHz. The proposed antenna with L-parasitic provides an efficiency of around −0.53 dB (89%) and a peak gain of 3.3 dBi at 2.4 GHz. Further, it offers an exceptionally low envelope correlation coefficient (ECC), approximately 0.0004, and diversity gain of nearly 10 dB, ensuring robust diversity and MIMO performance. These characteristics make the proposed design a promising option for use in low-profile modern WLAN MIMO systems. Full article

A hybrid DC–RF inductively coupled plasma (ICP) driven by a single-turn internal antenna was experimentally investigated to quantify magnetic confinement effects in low-pressure argon discharges. Superposition of a dc current on the RF antenna generated an azimuthal magnetic field that modified electron transport and reduced cross-field diffusion in the near-antenna region. Spatially resolved measurements of plasma density, electron temperature, plasma potential, and magnetic-field components were obtained using Langmuir, emissive, and B-dot probes. Increasing the dc current enhanced electron confinement and increased the plasma density by up to an order of magnitude at low RF power, together with improved radial and axial uniformity. A semi-empirical diffusion model incorporating electron-temperature-dependent ambipolar transport reproduced the measured ion-density distributions, ni(R,Z), within ±15%. The results support the interpretation that the discharge behaviour is governed by the coupled effects of localized magnetic confinement and inductive power deposition, and show that hybrid DC–RF excitation provides an effective route to denser and more spatially extended plasmas under low-pressure conditions. Full article