| The thesis is made on the basis of scientific projects for shell-borne antennas,conformal antennas and dual-band broadbeam circularly polarized(CP)antennas.The notion,application,current situation and development trend of antennas are explained at first.Then the research contents of the thesis are introduced.Finally,the main research achievements of the thesis and the further research are indicated.The thesis mainly include three parts.In the first part,dual-band miniaturized shell-borne antenna working at L band is presented.In the second part,a conformal array antenna for the cone platform is presented.In the third part,a dual-band broadbeam CP cross-dipole antenna is proposed.The main contents of this thesis are as follows:1.According to the project requirements of the shell-borne antenna,the concepts,current situation are introduced.The inverted V-shaped antenna is adopted based on the discussion results of the designing difficulties.Based on the simulated results,a prototype of the proposed antenna is fabricated and measured.The measured results reveal that the antenna has a voltage standing wave ratio(VSWR)of less than 1.8 and gains greater than 5.8 d B within the required operating bandwidth of 1268±10MHz and 1575±1MHz.The radiation patterns at the vertical and horizontal plane are "?" shape and "O" shape,respectively.The measured results are consistent with the simulated results and satisfy the project requirements which prove the effectiveness of the design methods.2.With the requirements of the conformal array antenna for the cone platform,the concepts and the basic theory of the conformal antenna are introduced.The rectangular microstrip antenna and the perturbation method are adopted to achieve the right-handed circularly polarized(RHCP)radiation.The antenna array is fed by a two-level T-shape power divider.The simulated results show that within the required bandwidth from 1573 MHz to 1577 MHz,the antenna has a VSWR of less than 1.7.The radiation patterns are "?" shape at the vertical plane and "O" shape horizontal plane with a value of un-roundness less than 3 d B.The axial ratio(AR)is less than 4d B at the horizontal plane.The simulated results show that the proposed antenna has a reference value in engineering applications.3.According to the antenna requirements of beidou navigation satellite system(BDS)and global positioning system(GPS),the difficulties and design methods of a dual-band broadbeam CP antenna are introduced.The antenna which is composed of two orthogonal dipoles is fed by a feeding network with equal amplitudes and 90° phase shift to obtain the CP characteristics.The feeding network is composed of a Wilkinson power divider and a broadband 90° phase shift.A prototype of the proposed antenna is fabricated and measured based on the simulated results.The measured results show that within the required bandwidth of B1,B2,B3 in BDS and L1,L2 in GPS,the antenna has a VSWR of less than 1.4.The RHCP gains of the antenna are greater than 2.5 d B in the top angle and-3.0 d B in the 20° elevation angle.The measured results show good agreements with the simulated results and meet the project requirements.Accordingly,the validity and feasibility of the design method are proved. |
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