Reflector Antenna Design Research Articles

Design of deployable mesh reflector antenna based on cable-dome tensegrity structure

In large-aperture deployable antennas, such as the AstroMesh antenna, the back-to-back arrangement of double-layer paraboloids can lead to size and weight exceeding the limits of the launch vehicle. To address this, a deployable mesh reflector antenna based on a cable-dome tensegrity structure, composed of tension cables and compression rods, is proposed. The structure and elementary unit of the cable-dome are presented, followed by the introduction of a W-deployable truss to meet the single-layer boundary node-hanging requirements. The geometric parameters and deployment kinematics are analyzed, leading to the optimization and simulation of a 50 m-aperture antenna. Compared to a same-aperture AstroMesh antenna, the cable-dome antenna offers a smaller folded size and weight. Finally, a 2 m-aperture prototype was constructed, and its feasibility verified through deployment experiments and surface accuracy photogrammetry. The proposed cable-dome antenna shows significant potential in large-aperture deployable antenna applications.

Surface accuracy prediction method for mesh reflector antenna considering uncertainty factors in manufacturing process

The cable-net structure of mesh reflector antenna meets the requirement of surface accuracy by optimizing the shape and tension. However, in the process of manufacturing and assembly, there are inevitable random errors and structure gravity, which lead to the displacement of the nodes in surface, the surface accuracy of the antenna decreases after fabrication eventually. It is challenging to analyze the uncertainty factors and the effects on the surface accuracy. Therefore, this paper analyzes the uncertainty factors of the antenna during fabrication and proposes a method to predict the surface accuracy of the antenna after manufacturing and assembly. Firstly, based on the equilibrium equation of the cable-net structure, the mechanism of node displacement induced by uncertainty factors leading to the reduction of surface accuracy is analyzed. Secondly, based on the structure characteristics and manufacturing conditions of the antenna, the uncertainty factors including cable-net manufacturing and assembly errors, cable-truss assembly errors and gravity are analyzed qualitatively and quantitatively, the distributions of the uncertainty factors are given. Thirdly, based on Monte Carlo method, the mean and interval of the surface accuracy of different dimension parameters are predicted, the empirical prediction formulas of the surface accuracy mean and interval are fitted. Finally, the accuracy and effectiveness of the proposed formulas are verified by several numerical simulations and surface accuracy measurement experiments. The prediction method can effectively guide the design and craft of large-aperture mesh reflector antenna.

A Shaped Reflector Antenna Design Approach for Contoured Beam Synthesis With Surface Curvature Constraints

A Shaped Reflector Antenna Design Approach for Contoured Beam Synthesis With Surface Curvature Constraints

Optimal self-stress determination for high-accuracy mesh reflectors design considering the pillow distortion

The pillow distortion is a significant barrier to the high-accuracy design of mesh reflector antennas, which is caused by the compatible deformation between the flexible cable network and the metallic mesh, manifested as the pillow-like distortion of the mesh reflecting surface. The pillow effect deviates the mesh surface from the desired paraboloidal shape leading to the surface error. Unfortunately, current researches usually neglect this effect in the mesh reflector design due to its complicated formulation. Focusing on this phenomenon, this paper proposed an optimal self-stress determination method for high-accuracy mesh reflector design. Firstly, a mechanism model of pillow distortion is proposed based on the cable-membrane constitutive models and coupling relations. The integrated equilibrium equation of the mesh reflector is established and solved by the dynamic relaxation (DR) method, which effectively analyses the influence of the pillow distortion on the mesh reflector. Then, considering the pillow distortion, a high-accuracy design method for the mesh reflector is proposed by optimising the geometrical sizes of the cable network and the metallic mesh combining the DR method with optimisation algorithm. Finally, the proposed method is effectively applied to the design of an eighteen-unit mesh reflector antenna, and the feasibility and effectiveness of the proposed method are demonstrated.

Reflector antenna design in different frequencies using frequency selective surfaces

Reflector antenna design in different frequencies using frequency selective surfaces

Pretension design for mesh reflector antennas with flexible trusses and hinges based on the equilibrium matrix method

In the current pretension design of mesh reflector antennas based on the equilibrium matrix method (EMM), the truss and hinge deformation cannot be accurately captured, which will deteriorate the shape accuracy of the antenna. To solve this problem, this paper proposes a new EMM-based pretension design method. In this method, the rod of the truss is modeled as Euler-Bernoulli beam, and the joint of the hinge is treated as the spring with six degrees of freedom. Based on the beams and springs, the systematic equilibrium equation of the mesh reflector antenna is established considering the flexibility of rods and hinges. Then, the mesh reflector antenna is divided into the inner cable network and boundary cable-truss-hinge assembly. The equilibrium equation of the boundary cable-truss-hinge assembly is solved by the force density method to calculate the truss and hinge deformation. The equilibrium equation of the inner cable network is solved by the EMM to fix all free nodes at desired positions. Combined with the active-set optimization algorithm, the required cable tensions are obtained by taking the mean tension ratio of the cable network as the objective function, thus ensuring high shape accuracy. Lastly, the proposed method is applied to the mesh reflector antenna and verified by ABAQUS.

HERAS: A Modular Matlab Tool Using Physical Optics for the Analysis of Reflector Antennas.

HERAS is a tool developed in Matlab for the analysis of reflector antennas using physical optics (PO) theory. Its graphical user interface (GUI) and source code are freely available for educational and research purposes. It has the necessity of being a flexible tool to provide adaptability to system engineering requirements and can also be of interest to antenna engineers working on the design of reflector antennas. Due to the increasing demand of broadband services, satellite communications systems are becoming highly complex in order to meet connectivity requirements. To fully exploit the benefits of these systems, multidimensional optimisations are crucial, which call for an efficient estimation of the coverage characteristics. Reflector-based solutions are one of the preferred architectures for very high-throughput satellite (VHTS) systems. A detailed description of HERAS is presented in this paper which has been validated with available commercial software packages. In addition, some examples are described in which the tool has been used for the efficient estimation of VHTS systems performance.

Innovative Design of Deployable Mesh Reflector Antennas with Cable Dome Structure

Innovative Design of Deployable Mesh Reflector Antennas with Cable Dome Structure

A convergence framework for optimal transport on the sphere

We consider a PDE approach to numerically solving the optimal transportation problem on the sphere. We focus on both the traditional squared geodesic cost and a logarithmic cost, which arises in the reflector antenna design problem. At each point on the sphere, we replace the surface PDE with a generalized Monge–Ampère type equation posed on the tangent plane using normal coordinates. The resulting nonlinear PDE can then be approximated by any consistent, monotone scheme for generalized Monge–Ampère type equations on the plane. Existing techniques for proving convergence do not immediately apply because the PDE lacks both a comparison principle and a unique solution, which makes it difficult to produce a stable, well-posed scheme. By augmenting the discretization with an additional term that constrains the solution gradient, we obtain a strong form of stability. A modification of the Barles–Souganidis convergence framework then establishes convergence to the mean-zero solution of the original PDE.

Reliability-based design of reflector antennas with integrated structural-electromagnetic analysis using adaptive kriging modeling

Reliability-based design of reflector antennas with integrated structural-electromagnetic analysis using adaptive kriging modeling

A convergent finite difference method for optimal transport on the sphere

We introduce a convergent finite difference method for solving the optimal transportation problem on the sphere. The method applies to both the traditional squared geodesic cost (arising in mesh generation) and a logarithmic cost (arising in the reflector antenna design problem). At each point on the sphere, we replace the surface PDE with a Generated Jacobian equation posed on the local tangent plane using geodesic normal coordinates. The discretization is inspired by recent monotone methods for the Monge-Ampère equation, but requires significant adaptations in order to correctly handle the mix of gradient and Hessian terms appearing inside the nonlinear determinant operator, as well as the singular logarithmic cost function. Numerical results demonstrate the success of this method on a wide range of challenging problems involving both the squared geodesic and the logarithmic cost functions.

A novel, combined reflector antenna design procedure for ultra-wide band planar lens antenna feeds

Feeding structure in a reflector system directly affects radiation characteristics of the antenna. With this research, a design procedure is introduced for high gain reflectors with ultra-wide band (UWB) planar dielectric lens antenna (PDLA) feeds. Traditionally, feed elements for broadband reflector applications require to exhibit frequency stable radiation patterns and phase center positions across a broad frequency band. However, UWB PDLAs have highly directive radiations in one plane and broad fan beams on the other plane. Phase center of a PDLA is almost stable in one plane, whereas apparent phase center variation is observed in the other plane. The phase center in the latter plane is located far behind the antenna and moves significantly with frequency. Although PDLAs have these unfavorable radiation characteristics as reflector feeds, using the introduced, novel procedure, highly directive radiation is achieved in 4–9 GHz frequency band. The illuminated reflector is designed by combining two parabolic reflectors having different and appropriate focal length-to-diameter (F/D) ratios to favor E- and H-plane feed radiations. Simulated results are validated by both ray tracing method and analytic solutions.

Novel Surface Design of Deployable Reflector Antenna Based on Polar Scissor Structures

Space-deployable mechanisms can be used as supporting structures for large-diameter antennas in space engineering. This study proposes a novel method for constructing the surface design of space reflector antennas based on polar scissor units. The concurrency and deployability equations of the space scissor unit with definite surface constraints are derived using the rod and vector methods. Constraint equations of the spatial transformation for space n-edge polar scissor units are summarized. A new closed-loop deployable structure, called the polar scissor deployable antenna (PSDA), is designed by combining planar polar scissor units with spatial polar scissor units. The over-constrained problem is solved by releasing the curve constraint that locates at the end-point of the planar scissor mechanism. Kinematics simulation and error analysis are performed. The results show that the PSDA can effectively fit the paraboloid of revolution. Finally, deployment experiments verify the validity and feasibility of the proposed design method, which provides a new idea for the construction of large space-reflector antennas.

Self-foldable origami reflector antenna enabled by shape memory polymer actuation

This paper presents the design, fabrication, and characterization of a self-foldable Active Origami Reflector Antenna (AORA) of parabolic form. Self-folding of the AORA is enabled by smooth uncreased folds composed of shape memory polymer (SMP) composites. Design methods for origami with smooth folds are applied to determine the shape and fold pattern of a planar sheet that can be folded to reach the parabolic antenna shape. A proof-of-concept prototype of the AORA is fabricated and self-folding of the AORA driven by thermal actuation of the SMP composite folds is demonstrated. The far-field electromagnetic (EM) characteristics of the AORA prototype are investigated through numerical simulations and experimental measurements in an anechoic chamber. A design-of-experiment study is conducted to investigate the effects of the antenna shape parameters on its EM characteristics such as far-field antenna gain and beamwidth, and to compare the performance of the AORA to that of equivalent smooth and faceted parabolic reflectors. Applications of the AORA include high-gain directional radio telescopes and satellite telecommunication.

Freeform reflector antenna design method to improve transmission efficiency and control output intensity distribution.

In this paper, a reflector antenna design method is proposed to improve transmission efficiency and control output intensity distribution. Primary and secondary mirrors are constructed segment by segment using a numerical method according to the law of energy conservation, the vector theory of reflection, and Fermat's principle that the optical path length of each ray must be equal. To verify the effectiveness and practicability of this method, an example of an antenna with the prescribed intensity distribution of the output beam is given. The transmission efficiency of the antenna system designed by this method reaches 100% in theory. The effects of output intensity distribution and deviation on transmission efficiency were also analyzed. We believe that the results show that the proposed method is a highly efficient approach to the design of a freeform reflector antenna to improve transmission efficiency and control the output intensity distribution.

Performance Evaluation of a Modified SweepSAR Mode for Quad-Pol Application in SAR Systems

Efficient earth observation using spaceborne synthetic aperture radar (SAR) requires the analysis of high-resolution wide-swath (HRWS) systems, which have a fine resolution and a short revisit time through wide-area observation, and quadrature-polarimetric (quad-pol) systems, which can obtain a quad-pol image and have many applications. The operational method of SAR generally affects system performance involving the system parameters and antenna patterns, and thus analyzing HRWS quad-pol SAR systems is essential to the system design. In this paper, an extension of the modified SweepSAR technique to a quad-pol observation scenario is performed and a comparison to ScanSAR and conventional SweepSAR is provided for a simulated scenario. On the basis of the system requirements, we selected the optimal parameters and designed a reflector antenna suitable for a wide-swath quad-pol SAR system. As a result of comparing the wide-swath quad-pol SAR operation modes, the modified SweepSAR mode demonstrated advantages in terms of system performance, such as the ambiguity ratio and swath width, and reflector antenna design for a spaceborne SAR system.

Parametric Analysis of an L-Band Deployable Offset Reflector for CubeSats

Thanks to the advances in the miniaturization and improved power consumption efficiency of electronics, computers, cell phone technologies, etc., today's spacecrafts and payloads are reducing their size and increasing their performance. However, not all systems can be reduced, as their dimensions are determined by the laws of physics. This study is focused on the design of an L-band reflector antenna for a CubeSat-based Earth observation mission devoted to measure the surface soil moisture. Two configurations of deployable parabolic reflector antennas and meshes are presented from the mechanical point of view. The electromagnetic analyses including the antenna feeder are also presented. It is found that the regular circular mesh performs slightly better than the irregular one, although requires a more careful manufacturing process.

A wideband beam shaping reflector antenna using model predictive control

A novel method based on model predictive control (MPC) is presented for synthesis and optimization of a wide band reflector antenna with cosecant squared and flat-topped radiation patterns. The proposed system is a doubly curved reflector antenna with nonlinear dynamic equation. This article investigates design and optimization of a double ridged horn reflector antenna operating within the frequency range of 8 to 18 GHz. In order to synthesize the proposed reflector antenna, MPC is used to achieve the desired radiation cosecant pattern. This method utilizes system model and tries to find the best control effort for minimizing the cost function by predicting the future behavior. The system differential equation is comprised of first and second order derivatives, so MPC can be a good solution for synthesis of a doubly reflector antenna. MPC optimizer operates based on state space model, so the proposed system is linearized in the operating range. Maximum error, the average error and side lobe level of this method for the radiation pattern of the proposed wideband antenna respectively are 1.4, 0.9, and −20 dB. Simulation results of the radiation pattern in CST and HFSS software show that the proposed reflector antenna can be used in broadband surveillance radar systems.

A Comprehensive Method of Ambiguity Suppression for Constellation of Geostationary and Low Earth Orbit SAR

ConGalSAR is a novel SAR constellation that has an outstanding performance of revisit and economy. In the system, with the MirrorSAR technology, one geostationary illuminator and several economical low earth orbit transponders work together to achieve a short revisiting interval. Because of the huge difference in the distances of transmitting and receiving, the spatial weighting of the antenna patterns on the ground is quite different, which leads to the deterioration of ambiguity to signal ratio. The multiphase center and digital beamforming antennas can suppress the ambiguity energy; however, they are too expensive and heavy to be equipped on the dozens of transponding nanosatellites. In this article, a comprehensive ambiguity suppression method, including the reflector antenna design and signal processing, is proposed to reduce the ambiguity ratio, which well solves the ambiguity problem under the condition of the low manufacturing costs and lightweight transponders. In terms of the hardware design, the multifeed reflector antenna is applied to the transponder, in which the feeds receive an echo together. Based on this, the low sidelobes beamforming is achieved to well suppress the ambiguity. Meanwhile, the amplitude-modulated chirps are also used here aiming at the residual ambiguity in the large dynamic scene. Through spectral selection and extrapolation processing, range ambiguity energy is suppressed more while preserving the resolution. The digital simulations show that the comprehensive method can realize −20 dB ambiguity ratios at least, which conforms to the ambiguity-to-signal ratio design of ConGaLSAR.

Near-Field Finite-Zone Focused Radiation From Reflector Antenna With Continuously Tapered Ellipsoidal Surface Curvatures

In this paper, a design of reflector antennas to produce near-field focused (NFF) radiation is presented. Instead of focusing the radiation at a single focal point, which results in an ellipsoidal reflector, this new reflector antenna application concept designates a finite zone, especially a finite curved surface, for NFF illumination. This finite zone may consist of several subzones for multi-NFF radiation. The design concept employs equal path lengths of wave propagation from the feed’s phase center toward the focal zone via reflections from the reflector’s surface in a one-to-one correspondence, which results in a confluence of reflection points found from a set of ellipsoidal surfaces. Based on a definition of the mapping mechanism to extract the reflection points to form the reflector, the field can be properly focused in the target zone by the concept of geometric optics (GO). In this paper, the basic theoretical concept is first summarized with a design equation developed for easy implementation. The focus property is demonstrated by a time-domain physical optics (TD-PO) analysis of spherical wave illumination with a transient-step field behavior to show the focusing responses of electromagnetic scattering from the reflector. The focusing characteristics of the frequency domain (FD) are also shown by PO simulation at 20 GHz.