| With the rapid development of composite materials and the demand for lightweight miniaturization of aircrafts,in addition to the design of more conformal antenna components with aircraft to reduce the effect of the air dynamics,to make antenna structures have high load-bearing capacity is needed.In this case,the antenna structures become parts of load-bearing structure in the aircraft,thus the antenna could either transmit the electromagnetic signal or have good mechanical properties,therefore the conformal load-bearing integrated antenna structure is realized.Due to the complexity of electromagnetic circumstances,during the communication process,the signal disturbance and poor signal transmission for mono-frequency usually occur.To solve the above problems,using the circularly polarized and dual-frequency is effective.In the area of loadbearing properties,the three-dimensional orthogonal woven composites have relatively good impact and delamination resistance properties due to the exitance of three sets of yarns in the composites,where Z yarns bind multi-layer warp and weft yarns which aligned orthogonally.The 3D woven structure has good integrity,and the antenna conformal with the structure will keep the electromagnetic properties stable.Base on the above background,in this study,the circularly polarized and dual-frequency antennas based on the three-dimensional orthogonal woven composites were designed and realized through a series of work from simulation to composite forming.The electromagnetic and mechanical properties of the antennas were then tested and analyzed.Since the antenna is a kind of textile antenna,the effects of yarns on the antenna properties were also investigated.This study provides some data base for the development of antennas based on the composites materials in the future.The detailed content of this study is as follows:In the first part,mainly from the theoretical and simulation,the circularly polarized and dualfrequency antennas with the working frequency of 1.9GHz and 2.45 GHz have been designed.Using the classical formula of antenna design,in combination with the theory of circularly polarized antenna and dual-frequency antenna,the circular polarization design was realized in the way that the rectangular patch of circularly polarized antenna was formed by the angle of corner-cutting.The diagonal feeding method was adopted in the rectangular patch of the dual-frequency antenna,so that the vertical edge of the patch is simultaneously designed Finally,the design results of the working frequency,the echo loss,the axle ratio,the bandwidth etc.were obtained by using the electromagnetic simulation software.In the second part of the work,mainly from the practical process,weaving and preparation of three-dimensional orthogonal woven composite antenna were done.Using the three-dimensional orthogonal weaving technology,the radiation element(copper wire),aramid(dielectric substrate)and grounding plate(copper wire)were combined into a whole three-dimensionally woven preform structure.Then the composite antenna was fabricated by vacuum-assisted resin transfer Molding(VARTM)process.The impedance matching and feeding through soldering were done afterwards.In the third part of the work,the electromagnetic testing and structure-electromagnetic response has been investigated.By analyzing the performance difference between the actual test and simulation,the antenna structure was improved and the composite antenna which accords with the design requirements was prepared.At last,the working frequency of the circularly polarized antenna was 1.93 GHz,the return loss S11 was-15.83 dB,the gain value of the bandwidth 7%,the surface gain was 4dB,and the circular polarization effect was realized in some angle range.The operating frequency of the dual-frequency antenna was 1.855 GHz and 2.471 GHz.S11 was-18.67 dB and-20.09 dB respectively,the bandwidth of 6.9% and 11.7%,1.855 GHz and 2.471 GHz respectively to the E-plane gain respectively 4.36 dB and-7.47 dB,H-plane gain was respectively 2.53 dB and-8.01 dB.In the fourth part,the mechanical properties and impact damage of the three-dimensional orthogonal woven composite antennas were studied in this work.The copper content was different in the three kinds of antennas(copper,single-sided copper,double-sided copper-clad antenna).The tensile,bending and impact properties of the three types of antennas were measured to explore the copper wire influence in the conformal load-bearing antenna mechanical properties.The antenna properties after damage were also tested and analyzed.The experimental results showed that although the increase of copper wire content could reduce the overall tensile performance and bending performance of the antenna,the antenna with the local micro-damage deformation,still can work normally.In summary,this paper mainly studies the dual-frequency and circularly polarized antennas based on the three-dimensionally orthogonal woven composites from three aspects including design,weaving preparation and antenna performance.Combining theory and practice,it provides a certain research basis for the development of three-dimensional orthogonal woven circularly polarized and dual-frequency conformal bearing antennas. |
