| Microstrip antenna is an important member in antenna family for its excellent antenna performance, and because of its easy conformal and good stealth performance compared with other antenna structures, microstrip antenna does not take up space so that it does not affect aircraft aerodynamics. With the development of intelligent structure and intelligent material, intelligent technology has been widely used, and embedded technology is one of the major technologies in intelligent structure. Embedded technology can integrate three-dimensional orthogonal woven-reinforced composites with microstrip antenna structure, which not only does not destroy the antenna performance and composite structure performance, but also improves the mechanical properties of antenna and overcomes the influence of high-speed craft aerodynamic performance of the traditional prominent antenna structure and delamination of laminated conformal bearing antenna structure because of its excellent mechanical performance, it also satisfies the requirements for antenna mechanical properties and antenna performance of the high-speed aircraft in our country, and plays a very important role in the field of aerospace and military reconnaissance fields. Embedded technology can also integrate textile fabric with microstrip antenna structure, which is called new type of textile structural antenna, it can keep excellent electromagnetic performance, and has good conformal characteristics, which is of great significance to militarily and civilian applications.This paper mainly investigated the electromagnetic properties of three-dimensional orthogonal woven conformal load-bearing microstrip antenna array and flexible microstrip antenna and antenna array respectively. The high frequency simulation software (Ansoft HFSS) was used to establish antenna model, and the four-element conformal load-bearing microstrip antenna array, one-element flexible microstrip antenna, the two-element flexible microstrip antenna array and four-element flexible microstrip antenna array which can work in L wave band (1-2GHz) with resonant frequency of 1.5 GHz were designed and fabricated. During the process of fabrication, the woven conductive wire such as copper wire has an effect on the mechanical properties of three-dimensional orthogonal woven conformal bearing microstrip antenna array, tensile property and bending property of vinyl composite (without copper wire) and antenna substrate (with cooper wire) were tested respectively, and a comparison was made between them. The research contents are as follows:(1) Compared with the simulated results of four-element conformal load-bearing microstrip antenna array, the measured resonant frequency was 1.79GHz, band width was 10.08%, VSWR (Voltage Standing Wave Ratio) was 1.16, gain was 0.49dB due to the dimension error, covered resin, void in the substrate and test condition. It was proved that this kind of antenna array can work well in L wave band. Besides, the analysis based on antenna parameters which influence the antenna performance provided the basis for the improvement and application of this kind of antenna.(2) The normalized tensile strength and modulus (normalize means the mechanical properties index divided by fiber volume fraction in the corresponding direction, similarly hereinafter) of vinyl composite were 1615.27MPa and 91.75GPa respectively, which were 30.61% and 13.83% higher than that of vinyl antenna substrate respectively. The normalized bending strength and modulus of vinyl composites were 2340.02MPa and 78.26GPa respectively, which were 971.15MPa and 3.68% higher than that of vinyl antenna substrate respectively. A comparison was made between vinyl composite and vinyl antenna substrate, although the tensile properties and bending properties of vinyl composite were better than that of vinyl antenna substrate, the difference was that vinyl antenna substrate contains copper wire network, which had significant influence on the tensile and bending properties of antenna substrate. In future work, finer copper wire can be woven into the antenna substrate so that the influence of copper wire network to mechanical propertied of antenna substrate can be reduced based on the analysis in this paper.(3) The performance index of one-element flexible microstrip antenna basically met the design requirements in planar condition. The measured resonant frequency was 1.7GHz, band width was 3.56%, VSWR was 1.47, gain in E-plane field and H-plane field were 2.25dB and 2.4ldB respectively. Cylindrical curvature radius had no significance influence on antenna resonant frequency, return loss, VSWR, bandwidth and radiation pattern. With the decrease of curvature radius, the gain showed the downward trend. When curvature radius was less than one wavelength of 171mm, gain both in E palne field and H-plane field were influenced a lot. This kind of antenna showed good stability of antenna properties, which provided the experimental basis for the research of flexible microstrip antenna array.(4) The performance index of two-element flexible microstrip antenna basically met the design requirements in planar condition. The measured resonant frequency was 1.5GHz, band width was 3.32%, VSWR was 1.15, gain in E-plane field and H-plane field were 6.15dB and 6.45dB respectively. The measured radiation pattern agreed well with the simulated radiation pattern. The measured results and simulated results were identical. Cylindrical curvature radius had no significance influence on antenna resonant frequency, return loss, VSWR, bandwidth and radiation pattern. With the decrease of curvature radius, the gain in E-plane field showed the downward trend, while gain in H-plane field showed no obvious discipline. The properties of the antenna were stable, which provided the experimental basis for the research of four-element flexible microstrip antenna array.(5) The performance index of four-element flexible microstrip antenna basically met the design requirements. The measured resonant frequency was 1.5GHz, band width was 7.93%, VSWR was 1.10. The maximum value can be obtained at 34°and 0°in E-plane field and H-plane field respectively. Gain in E-plane field and H-plane field were 7.34dB and 6.73dB respectively when the frequency was 1.5GHz. Cylindrical curvature radius had no significance influence on antenna resonant frequency, return loss, VSWR, bandwidth, radiation pattern and gain. With the changes of curvature radius, the antenna properties were stable. The proper range of cylindrical curvature radius can be chosen according to the practical applications, and this kind of antenna also provided the reference for the research and application in complicated curved surface of multielement flexible microstrip antenna. |
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