Antenna Surface Research Articles

All-Dielectric Integrated Meta-Antenna Operating in 6G Terahertz Communication Window.

Efficient transceivers and antennas at terahertz frequencies are leading the development of 6G terahertz communication systems. The antenna design for high-resolution terahertz spatial sensing and communication remains challenging, while emergent metallic metasurface antennas can address this issue but often suffer from low efficiency and complex manufacturing. Here, an all-dielectric integrated meta-antenna operating in 6G terahertz communication window for high-efficiency beam focusing in the sub-wavelength scale is reported. With the antenna surface functionalized by metagrating arrays with asymmetric scattering patterns, the design and optimization methods are demonstrated with a physical size constraint. The highest manipulation and diffraction efficiencies achieve 84.1% and 48.1%. The commercially accessible fabrication method with low cost and easy to implement has been demonstrated for the meta-antenna by photocuring 3D printing. A filamentous focal spot is measured as 0.86λ with a long depth of focus of 25.3λ. Its application for integrated imaging and communication has been demonstrated. The proposed technical roadmap provides a general pathway for creating high-efficiency integrated meta-antennas with great potential in high-resolution 6G terahertz spatial sensing and communication applications.

Electron heating mode in magnetic field diffusion region of microwave discharge ion thruster

In magnetic field design principle of microwave discharge ion thruster, it is universally received that enlarging the magnetic mirror region can confine more electrons to acquire better energy utilization rate, while reducing the magnetic field diffusion region can prevent electrons from losing at wall to reduce the discharge loss. However, recently the integrated simulation proposes a hypothesis that electrons can also be heated in the magnetic field diffusion region when the Child-Langmuir sheath is considered as a constraint condition for electrons. Therefore, herein a magnetic field structure for the magnet array microwave discharge ion thruster is designed to verify the hypothesis, in which the magnetic field diffusion region is located near the screen grid. Then, an integrated simulation is conducted for studying the initial discharge and ion beam extraction stages of the thruster. The simulation results show that in the magnetic field diffusion region, the electron temperature is 4–8 eV when the grid system voltage is not applied, while the electron temperature is 4–12 eV when the the grid system voltage is applied. And the plasma density in the latter case has one order of magnitude higher than that in the former case. It means that electrons are obviously heated in the magnetic field diffusion region when they are confined among the Child-Langmuir sheath, the plasma sheath at antenna surface, and magnetic mirror. This electron heating mode produces more high-energy electrons outside the magnetic mirror region to generate plasma in front of the grid system, which can significantly increase the plasma density and ion beam current density. The result shows that under the conditions of 0.3 sccm (1 sccm = 1 mL/min) xenon gas flow, 1 W input microwave power, 300 V screen grid voltage and –50 V acceleration grid voltage, the ion beam current and its density are 0.47 mA and 0.60 mA/cm<sup>2</sup> for the magnet array microwave discharge ion thruster, while the ion beam current and its density are 1.2 mA and 0.38 mA/cm<sup>2</sup> for the 2-cm microwave discharge ion thruster. The ion beam current density increases by 57.9%. Through the integrated simulation, a new electron heating mode in the magnetic field diffusion region is proved theoretically, which provides a theoretical basis for the magnetic field structure optimization of microwave discharge ion thruster.

Design and accuracy analysis of new cable network topology configuration of umbrella-shaped deployable antenna

To reduce the back-pillow effect of the cable-net antenna and improve the accuracy and error uniformity of the umbrella antenna surface, a new cable-net topology of the umbrella antenna is proposed. Firstly, the cable network segment is divided to obtain a new topological configuration of the umbrella antenna. Secondly, starting from the cable net accuracy calculation method, the Gauss-Legendre integral method is used to calculate the accuracy of the umbrella sky clue network surface method. Finally, the new cab-net configuration is compared and analyzed by example, and it is of great significance to improve the accuracy of the antenna surface and improve the uniformity of error distribution.

Application of high-impedance surfaces for low-profile antennas

The fundamental properties of high-impedance surfaces (Sievenpiper’s structures) in low-profile and miniature antenna design are considered. The analysis of the geometry and electric parameters influence on direction characteristics and input-match is given.

Discoloration of RF antenna coil surface after long-term operation of J-PARC ion source

In J-PARC (Japan Proton Accelerator Research Complex) center, the continuous operation period of the Radio Frequency (RF) negative hydrogen ion (H−) source equipped with the internal RF antenna coil is extended step by step in these 6–7 years for the goal to supply stable beam during the entire period of J-PARC user operation each year. In 2022, the continuous ion source operation for 4,001 hours (5.5 months) was achieved with 60 mA H− beam current at the ion source exit, 25 Hz repetition, mainly 500 μs beam pulse width, and 25 kW RF power injection. As the lifetime of the RF ion source is mainly limited by the deterioration of the enamel coating on the RF antenna coil, a detailed evaluation of the antenna surface is required to ensure the feasibility of the further extension of the operation period. In the present study, surface discoloration on the RF antenna coil observed after 5 months of operation is investigated by the application of a digital microscope and SEM/EDS analyses. The EDS analyses show that depositions of the sputtered stainless steel elements and the injected cesium are the most possible candidates for impurities on the enamel coating. The dimension measurements of the RF antenna thickness before and after the long-term operation also support the assumption that the discoloration is due to the deposited elements and hence insulation of the RF antenna coil by enamel coating is maintained. Possible mechanisms leading to antenna deterioration starting from element depositions on the antenna coating are also discussed in the summary part of this manuscript.

Thermal field simulation and material parameter optimization for spaceborne annular truss antennas

The operational efficacy of large spaceborne annular truss antennas in orbit is significantly influenced by solar irradiation and alternating Earth shadow. This antenna system periodically encounters diverse extreme environments that impact the precision of the antenna surface performance. Consequently, this study presents an optimized thermal control design and conducts temperature field simulation calculations for such antennas. Initial efforts are directed toward analyzing the variables influencing the antenna structure’s temperature, with specific attention paid to the distinctive compositional characteristics of high-precision antennas. As a subsequent step, orthogonal tests are implemented, facilitating the development of an antenna thermal analysis model. This model assists in the identification of principal variables influencing the antenna’s temperature field. Finally, the antenna’s optimal thermal design is drawn upon the biogeography-based optimization (BBO) algorithm, enabling the derivation of ideal material parameters for the thermal design of the antenna. This methodology offers theoretical guidance for future thermal control design of large spaceborne annular truss antennas.

Review of measurement methods for the main reflection surface of radio telescope antennas

Review of measurement methods for the main reflection surface of radio telescope antennas

Antenna surface measurement by near-field hemispherical scanning and related problems

Antenna surface measurement by near-field hemispherical scanning and related problems

Hybrid cavity-antenna architecture for strong and tunable sideband-selective molecular Raman scattering enhancement.

Plasmon resonances at the surface of metallic antennas allow for extreme enhancement of Raman scattering. Intrinsic to plasmonics, however, is that extreme field confinement lacks precise spectral control, which would hold great promise in shaping the optomechanical interaction between light and molecular vibrations. We demonstrate an experimental platform composed of a plasmonic nanocube-on-mirror antenna coupled to an open, tunable Fabry-Perot microcavity for selective addressing of individual vibrational lines of molecules with strong Raman scattering enhancement. Multiple narrow and intense optical resonances arising from the hybridization of the cavity modes and the plasmonic broad resonance are used to simultaneously enhance the laser pump and the local density of optical states, and are characterized using rigorous modal analysis. The versatile bottom-up fabrication approach permits quantitative comparison with the bare nanocube-on-mirror system, both theoretically and experimentally. This shows that the hybrid system allows for similar SERS enhancement ratios with narrow optical modes, paving the way for dynamical backaction effects in molecular optomechanics.

Dual-wideband radiating surface using interleaved electric and magnetic currents: Underlying physics and experimental verification

Unlike popular multiband antenna array radiation based on either electric or magnetic surface currents, the use of mutually interleaved and tightly coupled electric and magnetic currents results in an aperture-reuse space-efficient multiband radiating surface for highly integrated antenna-frontend architecture and spatial power combining design scenarios. In this work, slot and dipole modes corresponding to magnetic and electric currents are effectively interleaved and excited in a surface to develop a space-efficient dual-wideband aperture-shared radiating surface. In this case, due to an effective reuse of the antenna aperture over both frequency bands, a high aperture-reuse efficiency is achieved. First, we devise a planar magneto-electric (ME)-dipole-alike antenna and analyze it in both the frequency and time domain. The antenna is then studied by the characteristic mode theory and the findings are validated using full-wave simulations. The developed planar ME-dipole-alike antenna is used to realize a dual-wideband radiating surface in which electric and magnetic currents are mutually coupled and interlaced, which is excited by properly oriented and distributed sources on the antenna's surface. Eventually, a highly isolated dual-wideband prototype was developed and fabricated using a cost-effective multi-layer Printed Circuit Board (PCB) process that operates in the Ku-band with both impedance and gain bandwidth of approximately 42% and in the Ka-band with respective impedance and gain bandwidth of 29% and 16.32%.

Radio Telescope Surface Measurement via Deep Learning

This paper proposes a new method for accurately measuring the surface deformation of radio telescope antennas based on deep learning. A deep convolutional neural network is used to predict surface deformations by mapping the near-field intensity of the antenna, instead of relying entirely on a physical model. The proposed method could offer precise measurement of surface deformations in real time with only a single image of near-field intensity pattern. To optimize the deep learning model, a preliminary U-net based deep convolutional neural network (DCNN) model was developed based on a large data set generated by an approximate physical model, a partial differential equation (PDE). The network parameters were then fine-tuned using transfer learning with a small data set obtained by high precision numerical simulation. During this process, the fine-tuning layers that achieved optimal performance for the U-net network was studied. The final results show that the proposed method significantly improves the accuracy of antenna surface deformation recovery. Additionally, singular value decomposition (SVD) technology is employed to denoise the intensity image, which facilitates the application of the proposed method to actual deformation measurement.

Path Planning for Conformal Antenna Surface Detection Based on Improved Genetic Algorithm

The conformal antenna is a precision device installed on the wing of an aircraft, and its components are distributed on a curved surface. Quality detection is required after assembly. In solving the path planning problem for conformal antenna surface detection, the traditional genetic algorithm faces problems such as slow convergence and easily falling into a local optimal solution. To solve this problem, an improved genetic algorithm combining the historical optimal population (CHOP-IGA) is proposed. First, the algorithm uses the probability-based four-nearest-neighbor method to construct an initial population. Subsequently, the probabilities of the crossover and mutation operators are dynamically adjusted. Next, the algorithm applies the crossover and mutation operators to the population and performs mutation operations on each individual of the historical optimal population. Then, the fitness value is calculated and the next generation of individuals is selected from the parent, offspring, and historical optimal populations according to the elite selection strategy. Finally, the current best fitness is checked to determine whether updating the historical optimal population is necessary. When the termination condition is satisfied, the algorithm outputs the optimal result. Experiments showed that the algorithm satisfactorily solved the path planning problem for conformal antenna surface detection, with a 48.44% improvement in detection efficiency.

A Low RCS and Array-Insensitive FSS Wideband Radome

In order to further expand the RCS reduction model of the miniature broadband antenna, a four-notch shaped FSS radome insensitive to the number of array elements is designed based on the multi-layered medium Green’s function and the transflective coefficient of the finite radome is derived. The calculated results are in good agreement with the infinite array, showing broadband transmission performance in both C-band and X-band. The electric field distribution and far-field distribution of a finite FSS array are given and the effects of a 5 × 5 array in a V-shaped structure on the surface of a miniature broadband antenna on its gain coefficient and RCS reduction characteristics are calculated numerically. The results show that the designed radome exhibits good array element insensitivity and far-field scattering reduction characteristics and achieves significant in-band and out-of-band RCS accurate reduction under the premise of constant antenna radiation performance. At normal incidence, the single-station RCS in the passband and stopband are as low as −35 dB and −32.66 dB, respectively. The maximum reduction in the transmission band reaches 20.96 dB under oblique incidence and the projection size of the radome decreases with the increase in the bottom angle of the radome but the RSC reduction performance is basically unaffected and can be adjusted flexibly according to actual needs. The above results provide a theoretical basis and technical support for the application of FSS radome in RCS reduction in micro wideband antennas.

Manufacturing Millimeter-Wave Horn Antennas Using 3D Printing and Direct Electrodeposition

Additive manufacturing has undergone huge development in recent years. It has become commonplace both for the hobbyist community and industry, with important applications in several domains (e.g. biomedical, aerospace and automotive). Its main strength lies in the fact that custom parts can be quickly prototyped and manufactured, regardless of their complexity. However, many of the 3D printing techniques still have limitations in terms of strength, materials, production speed and overall usability. One of the main limitations is that most techniques utilize polymers, which are intrinsically non-conductive. This limits their use in electronics and telecommunication applications.Meanwhile, a lot of equipment used in telecommunications, such as antennas, tuners, waveguides, etc. remain very expensive due to complex and time-intensive manufacturing techniques. This leads to high prices, long lead times and limitations in the complexity of the geometries. The main goal of this research is to develop a fast and cost-effective method to produce conductive structures using additive manufacturing, more specifically fused deposition modeling (FDM) 3D printing. A special focus is put on horn antennas for microwave applications, as this application is very demanding on both the accuracy of the geometry and the conductivity of the structure.The approach in this work mainly consists of two steps: optimizing the plating conditions on flat test samples and extending this knowledge to the three-dimensional horn antenna. The chosen material is a PLA-based polymer with carbon black as an additive, which provides the polymer with some electrical conductivity (factor ~107 lower than copper). This conductivity is too low for any meaningful application but allows for the use of electrodeposition of copper directly onto the polymer to increase the conductivity. By focusing on reducing the distance from the electrical contact to the surface to be plated and by tuning the deposition parameters, high-quality uniform copper deposition is obtained on test samples. The achieved results outperform the current state-of-the-art in this field.The knowledge acquired from the test samples is then applied to the horn antenna. To this end a conductive antenna holder is developed. The antenna holder serves to keep the potential as constant as possible over the entire antenna surface in order to promote homogeneous deposition. It also aligns the electrodes, keeping the distance between electrodes as constant as possible and preventing short circuits. This method results in good partial coverage and again produces better results than can be found in the literature. However, direct deposition of a nicely uniform layer over the entire surface remains very challenging. An indirect electrodeposition method using conductive silver paint is used to produce the final version of the printed horn antenna.Measurements in an anechoic chamber demonstrate that the copper-coated version of the printed antenna has similar radiation performance as a commercial counterpart. An exponential horn antenna is made with decent performance, demonstrating the ease of production of more complexly shaped antennas. Our antennas can be produced within a couple of hours at a fraction of the price of commercial counterparts ($3 instead of $500-1500). This opens up new possibilities to quickly validate simulation results of new antenna designs. Further research focuses on the use of electroless plating to obtain more homogeneous copper deposition on three-dimensional structures, as well as extending our methodologies to more complex geometries.

Low-Profile Dual-Polarized Antenna Integrated with Horn and Vivaldi Antenna in Millimeter-Wave Band

In this paper, a dual-polarized antenna based on a substrate-integrated waveguide (SIW) horn antenna and Vivaldi antenna is proposed. The horizontal polarization (HP) is achieved by using the H-plane SIW horn antenna, while the vertical polarization (VP) is realized by a typical Vivaldi antenna etched on the surface of the SIW horn antenna. In front of the horn aperture, a dielectric lens is designed to optimize impedance matching and enhance directivity. Different feeding structures of the two polarizations are used to enhance the isolation between the two ports. The measured results demonstrate a 20.04–25.5 GHz (23.97%) overlapped dual-polarized impedance bandwidth, and the measured maximum gains of the HP and VP are 5.2 dBi and 8.2 dBi, respectively. A good isolation of 35 dB within the operating band is realized. The proposed dual-polarized antenna meets the demand to transmit and receive signals in two polarization directions simultaneously for wireless communication well.

CubeSat-Based Observations of Lunar Ice Water Using a 183 GHz Horn Antenna: Design and Optimization

Technological advancements have revolutionized the space industry, facilitating deep space exploration using CubeSats. One objective is to locate potential life-support elements, such as water, on extraterrestrial planets. Water possesses a distinct spectral signature at 183 GHz, useful in remote sensing and environmental monitoring applications. Detecting this signature provides crucial information about water and ice presence and distribution on celestial bodies, aiding future exploration and colonization efforts. Mostly in space remote sensing uses corrugated horn antennae due to high gain and radiation patterns but fabrication of corrugated antenna is very challenging or even impossible in some cases. To ease this challenge, in our research we propose ideas to transform a corrugated horn antenna into a smooth-walled design by using MATLAB Cubic smoothing Splines algorithms. We compare simulation results between smooth-walled and corrugated antennas, and we can see some improvements in insertion losses, Voltage Standing Wave ratio (VSWR), and gain. We also manufactured this 183 GHz antenna using a commercially available 3D printer by utilizing Acrylonitrile Butadiene Styrene (ABS) material. The antenna surface was then coated with a thin layer of copper using conductive paint. In the end, we practically evaluate smooth-walled antenna functionality and compare it with the theriacal results. Validating the antenna’s functionality proposes a cost-effective and accessible production method to be used in a CubeSat engineering model or university students’ project.

Design and Research of Intelligent Assembly and Welding Equipment for Three-Dimensional Circuit

The processing of the three-dimensional circuit on the surface of conformal antennas is mainly performed via manual processing. At present, there is no automatic intelligent equipment for the processing of a similar small-sized circuit with variable curvature in China. Therefore, a high-precision, automated, full-process manufacturing method for three-dimensional circuits with flexible surfaces on conformal antennas of radar equipment has been proposed to improve processing quality and manufacturing efficiency. The processing relationship between solder paste spraying, resistor mounting, and laser welding in the flexible three-dimensional circuit manufacturing process was analyzed. The structure of the new conformal antenna three-dimensional circuit intelligent manufacturing equipment was determined, and simulation verification of the three-dimensional circuit processing was performed using Vericut. The optimal processing parameters were selected based on solid experiments. This method meets the electronic assembly requirements of radar equipment and fills the domestic gap.

Pattern-Division Multiplexing for Multi-User Continuous-Aperture MIMO

In recent years, thanks to the advances in meta-materials, the concept of continuous-aperture MIMO (CAP-MIMO) is reinvestigated to achieve improved communication performance with limited antenna apertures. Unlike the classical MIMO composed of discrete antennas, CAP-MIMO has a quasi-continuous antenna surface, which is expected to generate any current distribution (i.e., pattern) and induce controllable spatial electromagnetic (EM) waves. In this way, the information is directly modulated on the EM waves, which makes it promising to approach the ultimate capacity of finite apertures. The pattern design is the key factor to determine the communication performance of CAP-MIMO, but it has not been well studied in the literature. In this paper, we develop pattern-division multiplexing (PDM) to design the patterns for CAP-MIMO. Specifically, we first study and model a typical multi-user CAP-MIMO system, which allows us to formulate the sum-rate maximization problem. Then, we develop a general PDM technique to transform the design of the continuous pattern functions to the design of their projection lengths on finite orthogonal bases, which can overcome the challenge of functional programming. Utilizing PDM, we further propose a block coordinate descent (BCD) based pattern design scheme to solve the formulated sum-rate maximization problem. Simulation results show that, the sum-rate achieved by the proposed scheme is higher than that achieved by benchmark schemes, which demonstrates the effectiveness of the developed PDM for CAP-MIMO.

A Novel Method for Creating a Glass Insulation Layer on the Copper Antenna Surface

A method of generating glass insulation on copper antenna surfaces under low-temperature conditions was developed and validated. The method is not only capable of firing insulation layers on copper surfaces at temperatures below 1000 °C but is also suitable for both curved copper wires and flat copper sheets. In this method, a silicon dioxide (SiO2) based powder is mixed with water at a certain specific gravity to prepare a low-temperature glaze. The oxygen-free copper is polished, annealed, and pickled before being impregnated and glazed. After the glaze on the surface of the oxygen-free copper has dried, the sintering is carried out in an argon atmosphere. The resulting glass insulation layer has a high bond strength to the copper surface and few impurities. The present results are expected to provide useful attempts and examples of solving the problem of inter-turn insulation and sputtering on copper antenna surfaces, and they show the broad application prospects of this method.

An Integrated Structure Analysis Method of Active Surface Antenna by Using the Simplified Actuator

The main surface of a large reflector antenna is composed of thousands of panels, which are inevitably deformed under natural load, leading to a great deterioration of electrical performance of the antenna. The active surface technique is an effective method to compensate antenna deformation error and has been widely used. The actuator is a complex component, it has not been established in the antenna structure analysis model, which limits the theoretical analysis ability of the active surface technology. To solve this problem, an integrated structure analysis method of active surface antenna by using the simplified actuator is proposed. First, according to the supporting characteristics and adjusting function of the actuator, the complex actuator is simplified a simple structure of support beams, support truss and adjustment beam. Second, the finite element model of the active surface antenna including the simplified actuator is established. Then, the relationship between the adjustment value (load) of adjustment beam and the deformation of the antenna structure is deduced, and the integrated analysis method for realizing the active adjustment of panels is established. Finally, the model and adjustment analysis method of the active surface antenna in this paper is applied to an 8 m antenna, and satisfactory structural analysis results are obtained, which shows the effectiveness and universality of the method, and provides a reference for the modeling and adjustment analysis of the active surface antenna.