Conformal Load-bearing Antenna Structure Research Articles

The Effects of Mechanical Loading on Resonant Response of a Conformal Load-Bearing Antenna System.

Glass fibre-reinforced polymer (GFRP) is a suitable substrate material for constructing a Conformal Load-Bearing Antenna Structure (CLAS). The relative permittivity of the CLAS substrate, which determines its resonant frequency, is affected by damage sustained by GFRP. This paper investigates the effects of damage (induced by mechanically loading the substrate) on the resonant response of the CLAS. Decoupling the antenna from the substrate was essential to evaluate the CLAS's true response to the induced damage. This paper details a systematic investigation examining how the frequency response of a "pristine" antenna and a surface-mounted antenna respond to a substrate subjected to quasi-statically induced mechanical damage and cyclic fatigue loading. The results demonstrate that the resonant frequency of the CLAS varies as a function of the substrate's mechanical damage. The prepared CLAS is tolerant to a certain degree of mechanical loading and related damage with its resonant frequency remaining within an acceptable bandwidth.

Conformal Load-Bearing Antenna Structures-Mechanical Loading Considerations.

One of the important functions of antennas is to facilitate wireless communication. The IEEE 802.11 is part of the IEEE802 set of local area network technical standards, and specifies the media access control and physical layer protocols for implementing wireless local area network computer communication. The network physical layer protocol with a centre frequency of 2.4 GHz has a bandwidth of 22 MHz. A conformal load-bearing antenna structure (CLAS) facilitating this communication band that is tuned to 2.4 GHz must remain within this bandwidth. The aim of this paper is to investigate the effects of mechanical loading imposed on a load-bearing patch antenna with respect to its ability to remain within the specified bandwidth. The mechanical loading configurations considered include tensile, biaxial, and twisting. This paper will also report on the response of the antenna patch to the presence of a disbond between the metallised antenna and its substrate, which can arise due to fabrication anomalies and operational usage. This numerical work will assist in the design of experimental testing of the mechanical and electromagnetic properties of an embedded CLAS, which will ultimately be used to inform selection of appropriate regions to place patch antennas on load-bearing deformable surfaces.

Additively Manufactured Conformal Load-Bearing Antenna Structure (CLAS)

Additively Manufactured Conformal Load-Bearing Antenna Structure (CLAS)

Efficient Computation of Real-Time Distorted Conformal Load-Bearing Antenna Structure Under Dynamic Mechanical Load Based on Modal Superposition

Conformal load-bearing antenna structure (CLAS) is an antenna that is integrated into the mechanical structure. It can endure external environmental dynamic loads directly. Deformation of the CLAS resulting from dynamic mechanical load leads to electromagnetic (EM) performance changing in real time. In this paper, an efficient computational method for the EM performance of real-time distorted CLAS is presented. It is based on the modal superposition method. In the electromechanical coupling model of distorted CLAS, the structure deformation is replaced with mode matrix times the modal coordinate vector. The far-field pattern of distorted CLAS is expressed as the combination of the structure-related terms and load-related term by math deduction. For a specific CLAS, the real-time far-field pattern can be obtained only when the dynamic mechanical load is known, and it is needless to get deformation through the structural transient analysis in ANSYS. Furthermore, two simulation experiments are carried out on a CLAS model with a microstrip patch under dynamic mechanical load. The numerical results show that the presented method is efficient and valid compared with the conventional method.

Inversion of Defect’s dimension in the Manufacturing Process of Conformal Load-bearing antenna Structure

Inversion of Defect’s dimension in the Manufacturing Process of Conformal Load-bearing antenna Structure

The diagnosis of manufacturing defects in composite material radome based on antenna's far field data

The conformal load-bearing antenna structure is a new multidisciplinary concept of aircraft structure, in which a microstrip antenna is layered into a composite material structure. For the manufacturing defects in the packaging of the microstrip antenna and the composite material radome, a retrieval method of the defects’ dimension by antenna's far field data has been presented. Two inversion formulas have been derived: one is the inversion from the far field data to the transmission coefficient of the radome; the other is from the transmission coefficient to the dimension of the radome. The combination of the two formulas could realise the inversion from the far field to the defects’ dimension. A 12·5 GHz conformal load-bearing antenna structure with four microstrip antennas is used in the simulation experiment. The results of the simulation show the precision and validity of the retrieval method.

Perturbation analysis for robust damage detection with application to multifunctional aircraft structures

The most widely known form of multifunctional aircraft structure is smart structures for structural health monitoring (SHM). The aim is to provide automated systems whose purposes are to identify and to characterize possible damage within structures by using a network of actuators and sensors. Unfortunately, environmental and operational variability render many of the proposed damage detection methods difficult to successfully be applied. In this paper, an original robust damage detection approach using output-only vibration data is proposed. It is based on independent component analysis and matrix perturbation analysis, where an analytical threshold is proposed to get rid of statistical assumptions usually performed in damage detection approach. The effectiveness of the proposed SHM method is demonstrated numerically using finite element simulations and experimentally through a conformal load-bearing antenna structure and composite plates instrumented with piezoelectric ceramic materials.

A Novel Inversion Method of Manufacturing Flaws in the Packaging of Conformal Load-Bearing Antenna Structure

Composite material is widely used in the conformal load-bearing antenna structure (CLAS), and the manufacturing flaws in the packaging process of the CLAS will lead to the degradation of its wave-transparent property. For this problem, a novel inverse method of the flaw’s dimension by antenna-radome system’s far field data has been proposed. Two steps are included in the inversion: the first one is the inversion from the far filed data to the transmission coefficient of the CLAS’s radome; the second one is the inversion from the transmission coefficient to the flaw’s dimension. The inversion also has a good potential for the separable multilayer composite material radome. A 12.5 GHz CLAS with microstrip antenna array is used in the simulation, which indicates the effectiveness of the novel inversion method. Finally, the error analysis of the inversion method is presented by numerical simulation; the results is that the inversed error could be less than 10%, if the measurement error of far field data is less than 0.45 dB in amplitude and ±5° in phase.

통신 항법용 다중대역 안테나 내장 스킨구조의 지상시험평가

This paper suggests a test and evaluation procedure of conformal load-bearing antenna structure(CLAS) for high speed military jet application. A log periodic patch type antenna was designed for multi-band communication and navigation antenna. Carbon/Glass fiber reinforced polymer was used as a structure supporting aerodynamic loads and honeycomb layer was used to improve antenna performance. Multi-layers were stacked and cured in a hot temperature oven. Gain, VSWR and polarization pattern of CLAS were measured using anechoic chamber within 0.15~2.0 GHz frequency range. Tension, shear, fatigue and impact load test were performed to evaluate structural strength of CLAS. Antenna performance test after every structural strength test was conducted to check the effect of structural test to antenna performance. After the application of new test and evaluation procedure to validate a new CLAS, a design improvement was found.

복합자성유전체를 이용한 항공기 CLAS 안테나 개발

본 논문에서는 스마트 스킨 기술을 활용한 소형경량 및 광대역 특성을 갖는 항공기용 안테나 내장 스킨 구조(CLAS: Conformal Load bearing Antenna Structure)를 설계하였다. 제안된 CLAS 안테나는 전기적 성능을 만족하기 위해 전도성 매쉬, 외부표피, 복사소자, 내부심재 및 하우징 등으로 구성하였다. 특히, 복사소자의 경우 복합자성유전체와 PCB에 에칭된 방사체로 구성되어 있으며 방사체는 복합자성유전체에 삽입되어 슬롯형 폴디드 대수주기 구조(Folded Log-Periodic)를 갖는다. 제안된 CLAS 안테나는 복합자성유전체에 의해 공진주파수가 낮아지고 임피던스 매칭특성이 향상되었으며 측정 결과, 안테나의 소형경량 및 광대역 특성을 확인하였다. In this paper, a compact and wideband CLAS(Conformal Load bearing Antenna Structure) was studied using smart skin technique. In order to satisfy the electrical performance of the CLAS antenna, the proposed CLAS antenna is composed of conductive mesh, face-sheet, radiator, honeycomb, housing. Especially, radiator is composed of composite magneto-dielectric material and radiating element etched on the PCB (Printed Circuit Board). The radiating element is inserted into the composite magneto-dielectric material and has sloted Folded LP(Log Periodic) structure. By fabricated composite magneto-dielectric, the resonance frequency is decreased and the impedance matching characteristics is improved. We verified that the antenna has wideband characteristics and compact size using the antenna test results.

Principal component analysis and perturbation theory–based robust damage detection of multifunctional aircraft structure

A fundamental problem in structural damage detection is to define an efficient feature to calculate a damage index. Furthermore, due to perturbations from various sources, we also need to define a rigorous threshold whose overtaking indicates the presence of damages. In this article, we develop a robust damage detection methodology based on principal component analysis. We first present an original damage index based on projection of the separation matrix, and then, we drive a novel adaptive threshold that does not rely on statistical assumptions. This threshold is analytic, and it is based on matrix perturbation theory. The efficiency of the method is illustrated using simulations of a composite smart structure and experimental results performed on a conformal load-bearing antenna structure laboratory test.

Capacitively Fed Cavity-Backed Slot Antenna in Carbon-Fiber Composite Panels

A new form of a conformal load-bearing antenna structure that consists of a cavity-backed slot in a carbon-fiber reinforced polymer (CFRP) panel is presented. The antenna is fed via a coaxial cable and patches that capacitively couple energy into the highly conductive carbon fibers without the requirement to abrade off the nonconductive epoxy resin layer on the surface. Computational simulations, which are validated by experiments, show that this feed configuration is as effective as soldering in a brass slot antenna. Backing the slot with a CFRP cavity enhances gain and front-to-back ratio by 2 and 13 dB, respectively. Gain is increased further by orienting the inner surface ply of the CFRP cavity to the same direction as the local E-field. Finally, the dimensions of the slot and cavity are optimized to minimize the antenna size. The resultant low-profile cavity is 14% of the volume of the original antenna design, but maintains similar gain and resonant frequency.

Fabrication and characterization of microstrip array antennas integrated in the three dimensional orthogonal woven composite

A 3D Integrated Microstrip Antenna (3DIMA) is a new concept for the smart skin structure. In this design concept, a microstrip antenna was woven into the 3D orthogonal woven composite for superior integration and impact resistance to the traditional conformal load-bearing antenna structure. This paper gives the design and fabrication of a three dimensionally integrated microstrip array antenna. The antenna was designed to work in the L band range. For comparison, a single-element patch microstrip antenna integrated into three dimensional composite was also fabricated. The results showed that the simulated and measured return losses were in good agreement for each antenna. By using array configuration, the array antenna showed more concentrating main beam in the radiation pattern and higher gain than the single-element antenna. In the mechanical test comparison, 3DIMA had a significantly lower tensile and bending strengths and somewhat lower tensile and bending moduli than those of the baseline composite due to the lower yield stress and lower tensile modulus of the copper wire. The peel strength of 3DIMA showed as high as 4.016 N/mm, which was much higher than that of the conventional glass fiber/PTFE laminates adhered with copper foil.

Effect of Wire Space and Weaving Pattern on Performance of Microstrip Antennas Integrated in the Three Dimensional Orthogonal Woven Composites

A conformal load-bearing antenna structure (CLAS) combines the antenna into a composite structure such that it can carry the designed load while functioning as an antenna. Novel microstrip antennas woven into the three dimensional orthogonal woven composite were proposed in our previous study. In order to determine the effect of the space between the conductive wires on the antenna performance, different space ratios of 1.7, 2.3 and 4.6 were considered in the design. Simulation results showed that when the space ratio increased, the frequency shift and return loss of the corresponding antenna became larger. And the antenna had relatively good performance when the space ratio reached 1.7. Two types of antennas were designed and fabricated with the ratio of 1.7 and 1 respectively and both of them obtained agreeable results. It was also demonstrated by the experimental that the orthogonal structure patch antenna had similar radiation pattern with the traditional copper foil microstrip antenna. However, the interlaced patch antenna had large back and side lobes in the radiation pattern because the existence of the curvature of copper wires in interlaced coupons lowered the reflective efficiency of the ground.

Fabrication and impact performance of three-dimensionally integrated microstrip antennaswith microstrip and coaxial feeding

A conformal load-bearing antenna structure (CLAS) combines the antenna into acomposite structure such that it can carry the designed load while functioning asan antenna. In this paper, two types of new 3D integrated microstrip antennas(3DIMAs) with different feeding methods are designed to work at the radarL-band. Different from the conventional CLAS, the radiating patch and theground plane of the 3DIMA are both composed of woven conductive wires andare bonded into the 3D composite physically by Z-yarns, greatly improving thedamage tolerance of the antenna. The return loss of the coaxial-fed antenna is−13.15 dB with a resonant frequency of 1.872 GHz, while that of the microstrip-fed antenna is−31.50 dB with a resonant frequency of 1.33 GHz. Both of the 3DIMAs have similar radiationpatterns to that of the traditionally designed microstrip antenna. In addition, anexperimental investigation of the impact response of the coaxial-fed 3DIMA was carried outand the results showed the radiation pattern had almost no change even when the antennareceived an impact energy of 15 J, exhibiting superior impact resistance to that of aconventional microstrip antenna.

Design and fabrication of microstrip antennas integrated in three dimensional orthogonal woven composites

During the last 10 years, there has been considerable interest in the development of conformal load-bearing antenna structure (CLAS) for communication and aerospace applications. CLAS combines the antenna into a composite structure such that it can carry the designed load while functioning as an antenna. In this paper, a 3D integrated microstrip antenna (3DIMA) was designed and fabricated. The input return loss and radiation pattern of the antennas were simulated using a computer aided design tool (HFSS) and also measured experimentally. The swept input return loss curve in the range of 1–2 GHz of the 3DIMA showed a return loss of −13.15 dB at the resonant frequency of 1.872 GHz with a voltage standing wave ratio (VSWR) of 1.56; the radiation pattern has a maximum at 180° and agrees well with the simulation results, indicating that 3DIMA can be an effective approach for a CLAS.

Analysis and optimal design of smart skin structures for buckling and free vibration

Analysis and optimal design of the smart skin, i.e., the conformal load-bearing antenna structure for buckling and free vibration are studied. The smart skin is modeled as an asymmetric composite sandwich structure which consists of different materials. In order to act as antennas or radars, a dielectric layer is embedded on the middle surface of the sandwich structure. The formulation of the smart skin model is based on the first-order shear deformation plate theory, and numerical results are obtained by the finite element method using a four-node plate element with five degrees of freedom at each node. The buckling and vibration behaviors of the smart skin are investigated with the variation of the aspect ratio, Honeycomb core thickness, area of dielectric layer and fiber angle of face sheet. Furthermore, to maximize the buckling load and the natural frequency of the smart skin, the optimal design is performed using a simple genetic algorithm.

Compressive Deformation Analysis of Smart Skin Structure Embedded with Round Shape Antenna

In this paper, a smart skin, i.e. a conformal load-bearing antenna structure, which is a multi-layer sandwich structure composed of carbon/epoxy, glass/epoxy and dielectric material, designs, analyses, fabrications and tests are conducted. Mechanical properties of each structural layer of the designed smart skin are obtained from experimental tests. Tests and analyses are conducted to study the deformation behavior of the smart skin under compressive loads. The measured data are compared with the numerical results from geometrically linear/nonlinear finite element analyses. Numerical prediction for the buckling load of the smart skin agreed well with the experimental data.

Parametric Study on Compression Deformation Behavior of Conformal Load-Bearing Smart Skin Antenna Structure

In this paper, a simple conformal load-bearing antenna structure smart skin with a multi-layer sandwich structure composed of carbon/epoxy, glass/epoxy, and a dielectric polymer was designed and fabricated. The mechanical properties of each material in the designed smart skin were obtained from experiments. Tests and analyses were conducted to study the behavior of the smart skin under compressive loads. The designed smart skin failed due to buckling before compression failure. The stresses of each layer and the first failed layer of the smart skin were predicted using MSC/NASTRAN. The finite element model was verified by comparing the numerical results from geometrical linear/nonlinear analyses with the measured data. The numerically predicted structural behavior of the smart skin agreed well with the experimental data. The results showed that the carbon/epoxy layer took charge of most of the compressive load, and the first failure occurred in the dielectric layer while the other layers remained safe. A numerical model was used to obtain design data from the parametric study. The effect of changing the design variables on the buckling and compressive behavior of the smart skin was also investigated. As a result, it was confirmed that the transverse shear moduli of the honeycomb core had a serious impact on the buckling load of the smart skin when the shear deformation was considerable.