Large Antenna Structures Research Articles

Development of Space-Borne Antenna Reflector via 3D Printing

The growing necessity of large aperture-based structures for many aerospace applications emphasizes the need to deploy large antenna structures in space. The space antennas should be light in weight and have low stowage volume, with efficient membrane packaging. The concept of additive manufacturing has been introduced to reduce weight as well as cost. In this paper, a comparative study has been done to analyze the advancement made in reducing weight with adequate strength. Based on the study, the main objectives are to develop a 3D-printed spherical reflector model with high specific strength and to assess the consistency of the model's shape. For determining the specific strength, tensile testing is performed on four different infill densities (20%, 40%, 60%, and 80%) with a grid infill pattern. It was observed that the specimen with 80% infill density has the highest tensile strength, 36.56 MPa, which is 23.51% more than 20% infill. However, the specimen with 20% infill density has the highest specific strength of 19.323 GPa/kg among the four specimens, which is approximately 64.64% higher than the 100% infill density. As a result of the testing, the spherical reflector model is 3D printed with 20% infill density, and it was found that the model achieves its shape stability and shape consistency with adequate specific strength.

Angular Displacement Control for Timoshenko Beam by Optimized Traveling Wave Method

The vibration of flexible structures in spacecraft, such as large space deployable reflectors, solar panels and large antenna structure, has a great impact on the normal operation of spacecraft. Accurate vibration control is necessary, and the control of angular displacement is a difficulty of accurate control. In the traditional control method, the mode space control has a good effect on suppressing low-order modes, but there is control overflow. The effect of traveling wave control on low-order modes is worse than the former, but it has the characteristics of broadband control. It can better control high-order modes and reduce control overflow. In view of the advantages and disadvantages of the two control methods, based on Timoshenko beam theory, this paper uses vector mode function to analyze the modal of spacecraft cantilever beam structure, establishes the system dynamic equation, and puts forward an optimized traveling wave control method. As a numerical example, three strategies of independent mode space control, traditional traveling wave control and optimized traveling wave control are used to control the active vibration of beam angle. By comparing the numerical results of the three methods, it can be seen that the optimal control method proposed in this paper not only effectively suppresses the vibration, but also improves the robustness of the system, reflecting good control performance. An innovation of this paper is that the Timoshenko beam model is adopted, which considers the influence of transverse shear deformation and moment of inertia on displacement and improves the accuracy of calculation, which is important for spacecraft accessory structures with high requirements for angle control. Another innovation is that the optimized traveling wave control method is exquisite in mathematical processing and has good results in global and local vibration control, which is not available in other methods.

A review on developments of deployable membrane-based reflector antennas

The gossamer space structures are very large and ultra-lightweight structures. A large aperture-based space structure is highly efficient in capturing signals from a wide coverage area. However, their deployment in space has been a critical challenge to date. Extensive research has been carried out on various types of gossamer structures used for earth exploration and deep space applications. Space antenna, in general, should have a large electrical aperture, be light in weight with small stowage volume, be easily deployable in space, and thermally stable. The antenna consists mainly of a reflector as a major part and a torus for supporting the reflector, electronic control unit, and struts. This paper covers an extensive review of gossamer space structure considering different categories of large deployable antennas. More attention has been given to a large membrane-based antenna having a parabolic reflector. This work includes the study of designs, analyses, and development of prototypes and successful deployment of space structures in orbit. We emphasize understanding the behaviour of thin membrane, their static and dynamic characteristics, wrinkling control, shape control of thin membrane reflector, and recent advances in deployment techniques of large deployable antenna structures.

Active Vibration Control of a Large Space Antenna Structure Using Cable Actuator

A large space antenna structure will inevitably vibrate due to the space thermal environment and maneuver actions of the satellite. Such vibration will last continuously and affect normal function of the antenna. Therefore, a proper vibration control method is vital to keep the shape accuracy of the structure within an acceptable range. The research object of this paper is a large deployable planar phased array antenna that uses cables as active actuators. Research contents include the optimization of actuator position and the design of control law: both of which have considered the unilateral and saturated constraints of the cable actuator. First, the finite element method is used to obtain the modal information of the structure. Then the actuator position optimization method is established by using the controllability principle and the particle swarm optimization algorithm. Second, a piecewise cost function is adopted to design the control law by combining a linear quadratic regulator with a bang–bang regulator. In the numerical simulation, the vibration control process of an antenna structure consisting of 18 lattices is simulated and analyzed. The results prove that the proposed actuator position optimization method and the control law could effectively suppress the vibration and maintain the shape accuracy of the antenna structure.

On-orbit assembly mission planning considering topological constraint and attitude disturbance

This paper investigates the on-orbit assembly mission planning problem of a large space antenna structure. The study is significantly important for the construction of large-scale spatial structures. The flexible connection between the antenna pieces and the topological constraint are taken into consideration. Several innovative approaches are presented to realize the mission planning process. First, the mesh model from the fly net dynamics is adopted and modified to create a mapping between the vibrations of the antenna plate during the assembly process and the assembly path. Second, the geometrical model is developed to implement the topological constraint into the system. Finally, a hybrid method combining the branch-and-bound method and the modified ant colony algorithm is proposed to solve the optimization problem. The simulation results show that the proposed algorithm can efficiently obtain a solution which respects the topological constraint and suppresses the vibration disturbance as much as possible.

Review of Large Spacecraft Deployable Membrane Antenna Structures

The demand for large antennas in future space missions has increasingly stimulated the development of deployable membrane antenna structures owing to their light weight and small stowage volume. However, there is little literature providing a comprehensive review and comparison of different membrane antenna structures. Space-borne membrane antenna structures are mainly classified as either parabolic or planar membrane antenna structures. For parabolic membrane antenna structures, there are five deploying and forming methods, including inflation, inflation-rigidization, elastic ribs driven, Shape Memory Polymer (SMP)-inflation, and electrostatic forming. The development and detailed comparison of these five methods are presented. Then, properties of membrane materials (including polyester film and polyimide film) for parabolic membrane antennas are compared. Additionally, for planar membrane antenna structures, frame shapes have changed from circular to rectangular, and different tensioning systems have emerged successively, including single Miura–Natori, double, and multi-layer tensioning systems. Recent advances in structural configurations, tensioning system design, and dynamic analysis for planar membrane antenna structures are investigated. Finally, future trends for large space membrane antenna structures are pointed out and technical problems are proposed, including design and analysis of membrane structures, materials and processes, membrane packing, surface accuracy stability, and test and verification technology. Through a review of large deployable membrane antenna structures, guidance for space membrane-antenna research and applications is provided.

Analysis and experiment on dynamic stiffness of clearance hinge in large circular truss antenna

Large space structures (LSS) composed of trusses, cables and meshes deployed on orbit, serves as the large antenna for different space missions. Deployable structures which are employed as large space supporting structures of space-borne antennas are widely used in earth observation space missions due to their large stiffness, small folding volume, light weight and easy extensibility. The dynamic research on deployable structures is great importance for the design, analysis, and capacity improvement of such structures. Each LSS contains many joints to combine the substructures, which contain clearance inevitably. The existence of the clearance causes the complicated dynamic characteristics of the LSS. It is necessary to estimate the influence of clearance on the structure. Hinge stiffness is an important factor in determining the dynamic characteristics of articulated structure, this paper will analyze the dynamic characteristics of radial connection part of the plane rotary hinge on large space deployable circular truss antenna structure, the radial kinetic model of hinges is established, the influence of hinge clearance, external excitation and displacement amplitude are discussed. The results indicate that the effect of clearance on the dynamic stiffness of the hinge is significant. On the exciting frequency and natural frequency in the hinge, when the ratio of radial vibration amplitude and the hinge clearance is constant, dynamic stiffness coefficient with the increase of external excitation is reduced. Dynamic stiffness coefficient with the frequency increases with increasing hinge. On the gap size and the hinge vibration amplitude, fixed frequency ratio, with the increase of the gap, the dynamic stiffness coefficient has a decreasing trend with the increase of the amplitude of the hinge, and with the decrease of the gap, the dynamic change of stiffness coefficient is not obvious, when the gap becomes larger, the dynamic stiffness coefficient increases significantly. When the clearance increases, the dynamic stiffness coefficient decreases. The validity of the theoretical calculation is verified by experiments.

Nonlinear dynamics of large circular annular truss antenna structures subjected to boundary loads

This paper investigates the bifurcation and chaos in breathing vibration of a circular truss antenna that has expanded subjected to heating load. The circular antenna is reducing to a continuum circular cylindrical shell, and considering the loads that come from cable net structure. By using the first order shear deformation theory, geometrical non-linearity strain-displacement relationship and Hamilton’s principle, the nonlinear partial differential equilibrium equation of the system are deduced. Galerkin method is utilized to obtain the nonlinear ordinary differential governing equations of the cylindrical shell under the specific boundary conditions that one generatrix of the cylindrical shell is clamped and both ends of the shell are free. Using Runge-Kutta method for numerical simulation of equivalent cylindrical shell under special boundary condition, the bifurcation diagram of system and the largest Lyapunov exponent curve, three-dimensional bifurcation diagram, time history diagram, phase map and Poincare section can be obtained. The influences of radial line load and in-plane load on vibration characteristics of the continuum circular cylindrical shell are studied.

Near Field Scan Alignment Procedure for Electrically Large Apertures

Computational imaging at microwave frequencies has gained traction due to its potential for obtaining high-quality images with fast acquisition rates. Complex and diverse radiation patterns form the cornerstone of this approach. Electrically large antennas, such as mode-mixing cavities and metamaterial apertures, have proven to be effective platforms for generating such waveforms. Due to the complex nature of these antennas, near field scanning is often required to characterize their radiation patterns. However, accurate knowledge of the produced waveforms’ spatial distribution, with respect to the physical position of the antenna, is imperative. This relies on precise alignment between the antenna and the near field scan stage during the characterization process—a requirement that is especially cumbersome to achieve when operating at high frequencies. We present an effective method to address this problem; by introducing RF markers into the antenna the position of the antenna under test within the near field scanning setup can be obtained directly from the measurements. The proposed method is experimentally verified through comparison with measurements made using optical photogrammetry. The proposed process will find application in the alignment of computational and multistatic imaging systems, commonly used in security screening and threat detection, as well as in tiled electrically large antenna structures.

Analysis of an antenna system design for a synthetic L- and P-band aperture radar

The article presents an analysis of options for designs of the antenna system for a synthetic aperture space radar (SAR), with acceptable performance characteristics in L- and P-bands. At the first stage the analysis of the current state of producing spacecraft with L- and P-band radars that use quite large folding antenna structures is carried out. It is shown that to obtain high performance of SAR in L- and P-band large folding reflectors with the diameter of up to15 meters are used. Further, variants of antenna systems are discussed and compared to determine the best combination in terms of the characteristics obtained and design complexity. An antenna system is proposed in the paper that uses antennae of the Yagi-aerial type as antenna array elements. The possibility of creating a space system consisting of several unified small spacecraft with L- and P-band SAR on board is shown.

Channel capacity investigation of a linear massive MIMO system using spherical wave model in LOS scenarios

Massive multiple-input multiple-output (MIMO) is a key technology for the 5th generation (5G) of wireless communication systems. The traditional plane wave channel model (PWM) is often not suitable for the large antenna structure, and in certain cases should be replaced by the more accurate spherical wave model (SWM). By using the spherical wave characterization method, this paper investigates the channel capacity performance of a linear massive MIMO system in line-of-sight (LOS) scenarios. Two types of access settings, the point to point (PTP) system and multi-user (MU) system, are considered. In the PTP setting, a geometrical optimization is performed to obtain configurations that are able to generate a full rank channel matrix for a linear massive MIMO system, which yields full spatial diversity even in LOS scenarios. Compared with the approximate and commonly applied rank-1 PWM, this is very useful for fixed wireless access and radio relay systems requiring high throughput. For the MU case, we compare the eigenvalue distributions of the LOS channels using the plane wave and spherical wave characterization method, and sum rate results are obtained by Monte Carlo simulations. The results show that MU systems using the more realistic and accurate SWM can achieve a higher sum rate than results from the PWM. This is beneficial and informative when designing massive MIMO wireless networks.

Active Vibration Control for a Large Annular Flexible Structure via a Macro-Fiber Composite Strain Sensor and Voice Coil Actuator

Large annular flexible structures (LAFS) are typical antenna structures for satellites. This structure can significantly increase antenna aperture and effectively improve communication accuracy with minimum addition of mass. LAFS have become mainstream for large aperture antenna structures. However, they have disadvantages, such as low natural frequencies, low damping ratio, and low stiffness. They easily suffer from low frequency, longtime and modal responses. Therefore, the vibration control of LAFS is very important. This study proposes a novel active vibration control method using macro-fiber composite (MFC) as a sensing unit, a voice coil actuator and a PD-fuzzy control algorithm. The MFC sensor can measure a minimum strain of 10-8 m/m. The voice coil actuator generates a displacement and driving force. Based on the feedback signal from the MFC sensor, the PD-fuzzy control algorithm controls the voice coil actuator. A dynamic model of LAFS was established, and its characteristics analyzed. A theoretical model for the voice coil actuator and MFC sensor were established, and the corresponding governing equations derived. An experimental system was set up. The results demonstrated that the novel active vibration control method has good performance. This active vibration control method can control vibration at ultralow frequencies and requires no additional stiffness.

New Conceptual Structure Design for Affordable Space Large Deployable Antenna

In recent and future space applications, affordability is becoming increasingly important, hence new kinds of large deployable mesh reflectors are being considered and used for satellite communications. We propose a new conceptual structure design for large deployable spaceborne antennas based on a folded fixed truss hoop reflector. Through analysis and simulation, this new structure is shown to have good mechanical performance and good electromagnetic performance. By comparing this new design with typical large deployable antenna structures, we show that our folded fixed truss hoop reflector is a potentially good selection for future affordable large deployable antennas in satellite communications.

The ultrastructure of Chlorobaculum tepidum revealed by cryo-electron tomography

Chlorobaculum (Cba) tepidum is a green sulfur bacterium that oxidizes sulfide, elemental sulfur, and thiosulfate for photosynthetic growth. As other anoxygenic green photosynthetic bacteria, Cba tepidum synthesizes bacteriochlorophylls for the assembly of a large light-harvesting antenna structure, the chlorosome. Chlorosomes are sac-like structures that are connected to the reaction centers in the cytoplasmic membrane through the BChl α-containing Fenna–Matthews–Olson protein. Most components of the photosynthetic machinery are known on a biophysical level, however, the structural integration of light harvesting with charge separation is still not fully understood. Despite over two decades of research, gaps in our understanding of cellular architecture exist. Here we present an in-depth analysis of the cellular architecture of the thermophilic photosynthetic green sulfur bacterium of Cba tepidum by cryo-electron tomography. We examined whole hydrated cells grown under different electron donor conditions. Our results reveal the distribution of chlorosomes in 3D in an unperturbed cell, connecting elements between chlorosomes and the cytoplasmic membrane and the distribution of reaction centers in the cytoplasmic membrane.

Transient Analysis of the Thin-Wire Equiangular Spiral Antenna

The study of large antenna structures, compared to the duration of the input pulse times the speed of light, allows a better understanding of the pulse propagation and reflection by the antenna structure. Identifying which part of the antenna geometry contributes to radiation makes it possible to identify the relationship between the radiated field impulse response and the acceleration of charges due to the antenna geometry. To this end, this paper analyzes the thin-wire equiangular spiral antenna from a time-domain perspective and shows the role of the centripetal acceleration on its radiated field. An analytical expression for the time-domain radiated field is also presented with good match with the simulation results. This approach leads to a more complete physical understanding of the radiation process and, thus, to a more guided design process of thin-wire antennas in general.

Modeling and analysis of a large deployable antenna structure

One kind of large deployable antenna (LDA) structure is proposed by combining a number of basic deployable units in this paper. In order to avoid vibration caused by fast deployment speed of the mechanism, a braking system is used to control the spring-actuated system. Comparisons between the LDA structure and a similar structure used by the large deployable reflector (LDR) indicate that the former has potential for use in antennas with up to 30 m aperture due to its lighter weight. The LDA structure is designed to form a spherical surface found by the least square fitting method so that it can be symmetrical. In this case, the positions of the terminal points in the structure are determined by two principles. A method to calculate the cable network stretched on the LDA structure is developed, which combines the original force density method and the parabolic surface constraint. Genetic algorithm is applied to ensure that each cable reaches a desired tension, which avoids the non-convergence issue effectively. We find that the pattern for the front and rear cable net must be the same when finding the shape of the rear cable net, otherwise anticlastic surface would generate.

MLC-SUMPLE Algorithm for Aligning Antenna Arrays in Deep Space Communication

For reliable reception of weak signals from spacecraft, a large antenna array structure is commonly employed in deep space communication system. The signal correlation is one of the methods used to combine signals from individual antennas. However, because the signal-to-noise ratio (SNR) from individual antennas is comparatively low, the phase offsets derived from the correlation cannot be used directly to align the signals, and some special processing is necessary to take advantage of all the antenna pairs. SUMPLE and matrix-free algorithms are two main approaches that have been analyzed or implemented with the array. Based on existing SUMPLE and matrix-free algorithms, a unified model is proposed and analyzed, and a novel algorithm named MLC-SUMPLE is proposed based on the new model. Theoretical analysis and simulations proved that the new algorithm performs better than existing combining algorithms in both the speed of convergence and steady-state performance.

Placement Optimization of Smart Piezoelectric Rods for Shape Control of Large Cable-Network Antenna Structures

Large cable-network antennas are typical flexible space structures, which will inevitably generate deformations under various disturbances from out space. To avoid the degradation of shape accuracy due to deformations, it is imperative to find effective approaches to implement shape control for such antennas. In this paper, a novel application of smart piezoelectric rods that are mounted in the ring truss supporting structure of the antenna is presented to solve the shape control problem. The control mechanism is to generate displacements in opposite direction to resist primal deformations by using the direct piezoelectric effect of piezoceramic materials. Based on the genetic algorithm, optimal locations of the smart piezoelectric rods used for shape control is analyzed in the study. Numerical results demonstrate that the present shape control approach with appropriate placement of smart piezoelectric rods is feasible and effective.

Shape Prediction of Large Deployable Antenna Structure on Orbit

For the worst-case analysis of a space structure's shape on orbit, various factors such as effects of thermal deformation, aged deterioration, and material hysteresis should be considered. Furthermore, the parameters of each factor have some uncertainty, such as in material properties. Therefore, in shape prediction, the consideration of these various factors and their parameters' uncertainties leads to a combinatorial explosion. To solve this problem, the factors are classified by the mode shape of deformation. If the mode shapes of some factors have high correlation, those factors are categorized in the same group. Within each group, maximum and minimum deformations are analyzed considering the uncertainty in the parameters. Among the groups with low correlation, deformations are evaluated using a combination of the maximum and minimum deformations from each group. As a result, the combinations of factors and parameters are drastically reduced. Such a shape prediction method was applied to a large deployable antenna structure of ASTRO-G. In this study, the performance of this antenna is evaluated using GRASP analysis for the predicted antenna shapes.

Study on dynamic reliability analysis of the structures with multidegree-of-freedom

his paper presents a method of determining the upper and lower bounds of dynamic reliability for the structural system with multidegree-of-freedom by considering the “weakest link”. First, a new computational strategy of dynamic reliability analysis of structural system under stationary random response is submitted. Secondly, a simplification and improvement of the Poisson formula in dynamic reliability computation of the system with single degree of freedom is described. Finally, the method is applied to a large antenna structure to demonstrate the algorithm.