| The research works are made with scientific projects. The design methods of the airborne antennas and antenna distribution are discussed in this dissertation.In the dissertation, the major works can be divided into two parts:several airborne antennas used for aeroplane wireless system are proposed in the first part, which includes biconical antennas with specific beam, broadband low profile microstrip antennas, circularly polarized antennas with stable phase center and array antennas with low sidelobe. The distribution of antenna system on the small airborne platform is studied in the second part. The author’s major contributions are outlined as follows:1. An optimization design method for antennas is proposed by combining particle swarm optimization (PSO) with standard software FEKO (PSO/FEKO). Antennas with complicated structures can be optimized using the proposed method without causing overlap problem in FEKO. The optimization procedure of the PSO/FEKO method can be suspended and resumed at spare time, which makes it possible to design complicated antennas in an effective, convenient and flexible manner.2. In the design of a biconical antenna with specific beam, a beam designing method based on meandered mother-lines is proposed. The PSO/FEKO method is adopted to optimize the structural parameters. By optimizing the structural parameters with the PSG/FEKO method, gain values of the biconical antenna for Ku-band application are greater than ldBi in the rang of0°～360°in the azimuth and0°～360°in the elevation.3. The broadband low-profile microstrip antenna is designed. With a U-shaped parasitic patch, a broadband microstrip antenna based on a thin substrate of1mm is designed using the modified GPSO/FEKO method. The measured results show that the bandwidth of the optimized antenna is2.33times as large as that of the rectangle microstrip antennas.4. Circular polarized microstrip antennas with stable phase center are investigated and implemented. It has been theoretically proved that a circular microstrip antenna, which is excited by a triple-feeding with equal amplitudes and120°phase shifts, can obtain circularly polarized radiation characteristics. Applying the least square method, the formulas of the apparent phase center (two dimensional) for arbitrary section in phase patterns are presented, and the results illustrate that the triple-fed circular polarized microstrip antennas can achieve stable phase center. Then, using a broadband phase shifting network based on composite right/left-hand transmission line (CRLH TL), the microstrip antenna with stable phase center can provide a3-dB axial ratio bandwidth of47.88%.5. Excellent array antennas with narrow beam and low sidelobe are designed. The feeding amplitude distributions of the array antenna are optimized by the GPSO algorithm. The printed dipole array antenna with narrow beam and low sidelobe is designed and fabricated. The measured results show that the proposed antenna can meet the requirements for engineering applications. Based on the method of parameter extracting, the waveguide slot array is designed. The simulated patterns, which agree well with the optimized ones, can satisfy the designing requirements.6. Applications of the FEKO/GPSO method in optimizing arrangement of antennas in small aircraft platforms are investigated. The pre-layout of the antenna system is arranged according to the engineering requirements and the design principle for electromagnetic compatibility (EMC) of antennas. The locations of the antennas in local areas are optimized by the FEKO/GPSO method. The measured results of airborne antenna EMC agree well with the simulated ones, which show the practicability and effectiveness of this method. |
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