Search Results (54)

This paper presents an efficient framework for surrogate modeling and rapid optimization of a dual-band circular patch antenna with a C-shaped slot (DB-CPAC) using multilayer perceptron (MLP) neural networks. Although highly accurate, traditional full-wave electromagnetic simulations are computationally expensive for geometric optimization due to complex slot-induced surface current perturbations. To address this limitation, a hybrid optimization framework based on Latin Hypercube Sampling (LHS) is proposed, combining the developed MLP model with a Method-of-Moments (MoM) simulator. The surrogate model uses an advanced modular architecture consisting of an ensemble of MLP neural networks for regressing center frequencies and classification MLP modules with a softmax output layer to estimate the probabilities of achieving bandwidth and gain targets. All networks are trained using the Levenberg–Marquardt algorithm with early stopping on data generated by a dedicated DB-CPAC_MoM_Sim software package. The proposed LHS-based optimizer employs the surrogate model for rapid global search and targeted local optimization before final MoM verification. Results show that this hybrid approach achieves an order-of-magnitude acceleration of the optimization process compared to conventional MoM methods while maintaining high accuracy. Full article

To improve autonomous path execution of a wheeled mower in standardized orchards, an ROS-based navigation control system integrating dual-antenna RTK-GNSS positioning and heading, an industrial computer, CAN-based drive control, and wireless manual takeover was developed. Parameterized reference paths consisting of straight sections and U-shaped turns were generated for inter-row operation, and an adaptive Pure Pursuit controller was implemented within the ROS framework. Three repeated field trials were conducted on a U-shaped path at a nominal speed of 0.8 m/s, with conventional Pure Pursuit using a fixed 2.0 m look-ahead distance as a reference. The mower completed the planned path under both controller settings. For the adaptive controller, the mean absolute lateral errors in the curved, straight, and overall sections were 0.124, 0.035, and 0.047 m, respectively. The corresponding overall error for PP-2m was 0.115 m. These results support the feasibility of the developed system for RTK-GNSS-guided closed-loop path tracking under the tested standardized-orchard conditions. Full article

EMAT technology for Non Destructive testing is an important method for materials testing in several industries. In EMAT tools, a key issue is the EMAT coils design and implementation. Depending on the type of inspection, the coil type should be selected, and then, its dimensions should be calculated. This paper describes a methodology to select, design and implement EMAT coils based on Lorentz Force for applications such as thickness measurement and crack detection. Unlike previous works that focus on a single coil topology, this study integrates coil selection, dimensional design, COMSOL-based radiation-pattern simulation and experimental validation within a single workflow. Four Lorentz-force coil designs are covered: PCB spiral (CSPCB), 3D-printed spiral (CS3D), PCB meander-line (CMPCB) and 3D-printed meander-line (CM3D). Key design parameters are explicitly addressed: number of turns N, outer and inner radii R and $r_0$, track width w and spacing s for spiral coils, and meander length and inter-trace distance for meander-line coils. Simulation verification is performed in COMSOL Multiphysics by evaluating the von Mises stress along a semicircular path around the coil to obtain the angular radiation pattern. Experimentally, polar radiation patterns are measured at 500 kHz, 1.9 MHz and 4 MHz on a steel specimen, matching the simulation frequencies, with maximum amplitudes of 32.2, 46.4, 47.9 and 10.6 mV for CSPCB, CS3D, CMPCB and CM3D, respectively, showing consistent agreement between simulated and measured lobe shape and directivity. This work also uses an analogy with radio frequency antennas to better understand the operation of coils through the concept of radiation patterns, in this case in solid materials such as steel. Full article

The development of multifunctional and lightweight materials is increasingly shaping the design of next-generation sensing and communication systems for space applications. In CubeSat platforms, severe constraints on mass, volume, and structural complexity motivate the integration of antenna functionalities directly onto load-bearing structures. In this context, printed electronics, particularly inkjet-printed conductive materials, offer new opportunities for creating adaptive, flexible, and structure-integrated devices that support both sensing and communication functionalities. This work investigates the electrical performance of inkjet-printed conductive materials for structure-integrated patch antennas. Two silver-based inks and one carbon-based ink were deposited on fiberglass-reinforced epoxy substrates and electrically characterized over a temperature range from −20 °C to 50 °C, representative of CubeSat operational conditions. The silver-based inks exhibited electrical conductivities in the range of 10⁶ S/m with limited variation (<10%) under thermal cycling, whereas the carbon-based ink remained below 10¹ S/m, even after multilayer deposition, indicating insufficient performance for this application. Based on these results, the best-performing silver ink was selected to fabricate a proof-of-concept patch antenna directly on an S2-glass/epoxy structural substrate. The proposed approach demonstrates the feasibility of integrating conductive inkjet-printed layers onto composite structural substrates intended for future structure-integrated antenna applications in CubeSat platforms, offering a pathway toward mass-efficient, low-profile, and highly integrated communication structures. Full article

Spaceflight has become more accessible than ever due to increased launch reliability and significant advances in electronics. Among these advancements are small-sized PocketQubes, which are small satellites (5 × 5 × 5 cm for 1P) that can be built using commercial off-the-shelf components. A critical subsystem in these satellites is the communication system, which requires compact and deployable antennas. This work focuses on the design of deployable antennas for TU Delft’s upcoming Delfi-Twin PocketQube mission, operating in the 10 m and 6 m amateur bands. The Shape Memory Alloy (SMA) nitinol was selected as the antenna material due to its favorable mechanical and deployment characteristics. However, its high electrical resistivity limits antenna efficiency. This study investigates multiple conductive coating techniques for nitinol antenna wires, aiming to improve electrical performance while maintaining mechanical flexibility. The coatings are evaluated through electrical resistance measurements and mechanical bending tests. Among them, a DuPont ME164 ink showed the most promising performance, significantly reducing wire resistance compared to bare nitinol while preserving mechanical integrity. These results address a novel conductive coating for efficient SMA-based antennas and demonstrate a valid approach for improving deployable antennas in small-satellite applications. Full article

Terahertz wireless communication offers ultra-high bandwidth, enabling an extremely high data rate for next-generation networks. However, it faces challenges including severe propagation loss and atmospheric absorption, which limits the transmission rate and transmission distance. To address the problem, polarization division multiplexing (PDM) and antenna diversity techniques are utilized in this work to increase system capacity without changing the bandwidth of transmitted signals. Meanwhile, duobinary shaping is used to solve the problem of bandwidth limitation of components in the system, and the final duobinary signals are recovered by maximum likelihood sequence detection (MLSD). A Gaussian mixture model (GMM)-enhanced duobinary unsupervised adaptive convolutional neural network (DB-UACNN) is proposed, to further deal with channel noise. Based on the technologies above, a 2 × 2 multiple-input multiple-output (MIMO) photonic-aided terahertz wireless transmission system at 300 GHz is demonstrated. Experimental results have proved that the signal-to-noise ratio (SNR) gain of duobinary shaping is up to 1.87 dB and 1.70 dB in X-polarization and Y-polarization. The proposed GMM-enhanced DB-UACNN also shows extra SNR gain of up to 2.59 dB and 2.63 dB in X-polarization and Y-polarization, compared to the conventional duobinary filter. The high transmission rate of 100 Gbit/s over the distance of 200 m is finally realized under a 7% hard-decision forward error correction (HD-FEC) threshold. Full article

In recent years, the scientific community has increasingly focused on state-of-the-art techniques, such as MIMO and mmWave transmission, aimed at enhancing the performance of telecommunication channels both quantitatively and qualitatively through various approaches. These efforts often rely on channel models designed to more accurately represent real-world conditions, thereby ensuring that the results are objective and practically applicable. In the present study, we employ one of the most scientifically reliable system- level simulators, Vienna SLS Simulator, to evaluate the performance of a wireless channel that we configure based on the latest standards (3GPP TR 36.873). We take into account the well-known non-symmetrical behavior of mMIMOs, where m stands for microwave MIMOs, in wireless communication systems and analyze the resulting changes in key performance metrics including average cell throughput, average user spectral efficiency and signal-to-interference-plus-noise ratio (SINR). We vary specific parameters such as transmission power, antenna polarization, ratio of indoor to outdoor users, and others with the aim of validating or challenging existing scientific assumptions. Particular attention is given to studying how variations in the aforementioned factors affect channel geometry and spatial uniformity, emphasizing the role of antenna geometry, polarization and user distribution in shaping channel asymmetries in mmWave MU-MIMO systems. Overall, this study provides insights into designing more balanced and efficient wireless systems in realistic urban environments. Full article

Space mesh antennas require large-diameter reflectors to achieve aperture surfaces with high gain. To date, many pioneering studies have pursued deployable mechanisms capable of achieving high deployment ratios, primarily focusing on ring and umbrella structures for spaceborne antennas. In this work, a conceptual design of a Deployable Pantograph Rib structure-based parabolic Antenna (De-PaRA) is presented by employing pantograph structures that ensure high stowage efficiency. This approach addresses the shortcomings of conventional space antenna mechanisms. In parallel, this study aims to overcome the structural safety issues that may arise from insufficient axial stiffness of the rib geometry after deployment. To achieve these objectives, superelastic shape memory alloy (SMA) wires were integrated along the antenna ribs to reinforce axial stiffness while maintaining constant inter-rib spacing. Modal analysis demonstrated that SMA wire integration increases the axial stiffness by approximately 2-fold, with eigenfrequency rising from 9.932 to 14.3 Hz. A prototype with a 1.6 m deployed diameter, achieving a volume deployment ratio of 58.8, was quantitatively evaluated through multi-body dynamics simulations and experiments. These results demonstrate reliable deployment operation and mechanical feasibility. Full article

This letter presents a high-gain frequency-controlled beam-scanning antenna specifically designed for through-wall radar (TWR) applications in the W band. The antenna leverages the leaky-wave radiation generated by spoof surface plasmon polaritons (SSPPs) propagating on sinusoidally modulated reactance surfaces (SMRS). Periodically arranged quasi-H-shaped metallic cells are employed to achieve beam scanning. The integration of a flared structure at the apex of the designed SSPP antenna results in a significant gain enhancement, yielding an approximate increase of 10 dB. From 92.8 to 97.6 GHz, the antenna exhibits a reflection coefficient of |S11| < −10 dB, provides a high scanning rate of 4.05°/%, and achieves a realized gain of 20.9 dBi. This design eliminates the necessity for mechanical rotators and phase shifters that are typical in traditional TWR systems, significantly reducing system complexity and cost. A vehicle-mounted W-band TWR system was developed, integrating the designed SSPP antenna and employing linear frequency modulation technology to emit millimeter-wave signals for electronic scanning detection. With an economical and efficient design approach, testing has demonstrated that the system can perform through-wall imaging at a distance of 10 m, both in stationary and in motion conditions. Full article

This study is an initial study for the development of a large truss-type deployable mesh antenna, and it involved the development process of a 1.5 m-scale deployable mesh antenna. The geometric characteristics of the reflector were considered for the initial net design. Based on the antenna’s operating frequency, the L-band, the surface root mean square (RMS) error and focal length/diameter (F/D) ratio of the reflector were calculated. Design requirements for the antenna’s weight, stowed/deployed dimensions, and fundamental frequency were established. The material properties of each component were applied to the design model, and the geometric dimensions were verified to ensure that the weight and stowed/deployed design were fulfilled. The fundamental frequency requirements under stowed/deployed conditions were verified through modal analysis, and the structural deformation of the ring truss was confirmed through load analysis. The reflector antenna was assembled to the ring truss with the net and mesh, according to the assembly procedure. The curvature of the reflector surface was shaped by adjusting the bolt length of the tension control device. Using V-Stars, a specialized surface error measurement device, the surface RMS error requirements for the reflector were confirmed to be satisfied. Finally, the development verification of the antenna was completed by performing repeated deployment and a thermal vacuum test. Full article

This paper proposes a miniaturized design for a terahertz tri-mirror compact antenna test range (CATR) system, composed of a square-aperture paraboloid primary mirror with a side length of 0.2 m and two shaped mirrors with circular apertures of 0.06 m and 0.07 m in diameter. The design first employs the cross-polarization cancelation method based on beam mode expansion to determine the geometric configuration of the system, thereby enabling the structure to exhibit low cross-polarization characteristics. Subsequently, the shaped mirrors, with beamforming and wave-front control capabilities, are synthesized using dynamic ray tracing based on geometric optics (GO) and the dual-paraboloid expansion method. Finally, the strong edge diffraction effects induced by the small-aperture primary mirror are suppressed by optimizing the desired quiet-zone (QZ) field width, adjusting the feed-edge taper, and incorporating rolled-edge structures on the primary mirror. Numerical simulation results indicate that within the 100–500 GHz frequency band, the system’s cross-polarization level is below −40 dB, while the amplitude and phase ripples of the co-polarization in the QZ are, respectively, less than 1.6 dB and 10°, and the QZ usage ratio exceeds 70%. The designed CATR was manufactured and tested. The results show that at 183 GHz and 275 GHz, the measured co-polarization amplitude and phase ripples in the system’s QZ are within 1.8 dB and 15°, respectively. While these values deviate slightly from simulations, they still meet the CATR evaluation criteria, which specify QZ co-polarization amplitude ripple < 2 dB and phase ripple < 20°. The overall physical structure sizes of the system are 0.61 m × 0.2 m × 0.66 m. The proposed miniaturized terahertz tri-mirror CATR design methodology not only enhances the QZ characteristics but also significantly reduces the spatial footprint of the entire system, demonstrating significant potential for practical engineering applications. Full article

The demand for large-scale components continues to grow with the development of frontier technologies. Traditionally, these components are machined using machine tools, which are costly and have functional limitations. High-flexibility robots provide a cost-effective solution for machining large-scale components. This research proposes a dual-robot fabrication system for producing a 2.4 m × 4.58 m carbon fiber reinforced polymer (CFRP) antenna reflector. First, the kinematic model of the in-house developed robot was established to compute its theoretical workspace, which was subsequently used to partition the machining regions. Based on laser tracker measurements and theoretical calculations, a method and procedure for calibrating the Tool Center Point and Tool Control Frame of the robot were proposed. Subsequently, the dual-robot fabrication system was configured based on the determined machining regions for each robot. To further improve the figuring accuracy of the system, the support structure and figuring path were investigated and determined. Finally, processing experiments were conducted, and the material removal function for the flexible processing tool was computed to shape the reflector surface. The final results achieved the required surface figure accuracies for areas ≤ φ1750 mm, ≤φ2400 mm, and the whole surface were improved to 13.5 μm RMS, 23.4 μm RMS, and 45.8 μm RMS, respectively. This validates the processing capability and demonstrates the potential application of the dual-robot fabrication system in producing large-scale components with high accuracy. Full article

Over the last decade, large-scale antennas have been developed to enhance precise blue force tracking and improve situational awareness. In general, such large-scale antennas, ranging from 1 to up to 10 m, need a specific mechanism that can reconfigure their shapes and morphologies, resulting in stowing and deploying upon the given environment. In parallel, it must be noted that such deployable mechanisms should accommodate a large aperture diameter while ensuring they are lightweight, robust, and structurally rigid to avoid undesired deformations due to the deployment. With these in mind, this work presents a large frustum-shaped deployable antenna mechanism with a large aperture diameter of 7.5 m. The deployable mechanism is composed of hierarchical bayes the radial direction at 30° intervals. Twelve bayes in total identify the overall morphology of the deployable antenna, which features a dodecagon. Specifically, the bay is composed of three linkage structures: a six-bar linkage mechanism, a V-folding mechanism, and a single pantograph mechanism. As a result of static and dynamic simulations, it is identified that the mechanism achieves an area-to-mass ratio of 5.003 m²/kg and a safety factor of 323.8 upon deployment. Conclusively, this work demonstrates a strong potential of the deployable antenna mechanism, providing high rigidity and large aperture diameter while ensuring high stability in space environments. Full article

The current emphasis in the advancement of space-based synthetic-aperture radar (SAR) is on lightweight payloads under 100 kg with resolutions surpassing 1 m. This focus is directed toward meeting the launch criteria for multiple satellites on a single rocket and cutting costs. This article discusses the creation and progress of a Ku-band SAR payload for the Taijing-4(03) satellite, launched on 23 January 2024 and accompanied by four other satellites. The SAR payload design was customized to meet the demands of a micro-nano satellite platform, resulting in a lightweight, flat design weighing less than 80 kg, seamlessly integrated with the plate-shaped satellite platform. The article also introduces a beam optimization strategy for the phased array SAR antenna, significantly boosting the SAR system’s performance. The SAR payload provides various operating modes like slide-spot, strip, Scan 1, Scan 2, and others, with a maximum achievable resolution exceeding 1 m. Extensive in-orbit testing of the payload produced numerous high-quality SAR images with potential uses in emergency disaster mitigation, safeguarding ecosystems, monitoring forests, managing crops, tracking sea ice, and more. Full article

This paper describes the design and experimental verification of a 6 m parabolic deployable mesh reflector antenna mechanism based on a superelastic shape memory alloy. This antenna mainly consists of a deployable primary reflector with a superelastic shape memory alloy-based hinge mechanism and a fixed-type secondary reflector mast, where a rotary-type holding and release mechanism and deployment speed control system are installed. The main feature of this antenna is the application of a superelastic shape memory alloy to the mechanism, which has the advantages of plastic deformation resistance, high damping, and fatigue resistance. A shape memory alloy is applied to the hinge mechanism of each primary reflector rib and to the rotary-type holding and release mechanism as a deployment mechanism. In addition, a superelastic shape memory alloy wire is applied to the antenna in the circumferential direction to maintain the curvature of the primary reflector. The effectiveness of the proposed mechanism design was verified through repeated deployment tests on models of the superelastic shape memory alloy-based hinge mechanism and the antenna system. Full article