Research On The L-band Miniaturized Circularly Polarized Missile-borne Antenna And Broadband Circularly Polarized Antenna

The research works are made on the basis of specific scientific projects for an L-band missile-borne miniaturized circularly polarized?CP?antenna and a broadband circularly polarized?CP?antenna.Firstly,the notion,application,research background,current situation and development trend of the antennas are introduced.Sencondly,the research contents of the thesis are introduced.Finally,the main research achievements of the thesis and the further research are indicated.The thesis consists of two main parts.An L-band missile-borne antenna achieving properties of miniaturization and CP radiation in the after-body is presented in the first part.Then a broadband CP antenna achieving a wide impedance bandwidth covering the operating bands of GNSS and a good performance of CP radiation is presented in the second part.The main works of the thesis are outlined as follows:Based on the specific project requirement of missile-borne antenna,the difficulties in achieving miniaturization and circularly polarization characteristics are pointed out.Then the design methods of the missile-borne antenna are presented.The substrates and cover-substrates with a high dielectric constant are used to reduce the working frequency of the antenna.Meanwhile,the radiating patch loading with gaps extends the current path to achieve the miniaturization of the antenna.The CP radiation of the antenna is realized by feeding with an unequal distribution network with a 90°phase shifting,which reduces the influences of the platform.The antenna is simulated and optimized by using the ANSOFT High Frequency Simulator?HFSS?.On the basis of the simulated results,a prototype of the antenna is fabricated and measured.Good agreements can be obtained between the simulated and measured results.The overall dimension of the proposed antenna is only24.5×24.5×9.5mm³ and the maximum length of the antenna is less than 0.1?₀,where?₀ is the corresponding free-space wavelength at the center frequency of the working band.The measured results indicate that the proposed antenna achieves good performances including VSWR of less than 2.0,AR of less than 6.2dB and gains of greater than-6.9dB within±20°beam widths while achieving right-hand CP radiation within the required frequency bands,which meet the design requirements.Secondly,a novel wideband CP square-ring microstrip antenna is proposed.By analyzing the project requirements,the difficulties in achieving a wide impedance bandwidth and circularly polarization characteristics are pointed out.Then the design methonds of the antenna are presented.At different frequencies,the working areas of the square-ring microstrip antenna with four shorted L-shape patches are different,which broadens the operating band of the antenna.The CP radiation is achieved by feeding the antenna through a broadband phase shifting network and coupling-feed.The antenna is simulated and optimized by using the ANSOFT High Frequency Simulator?HFSS?.On the basis of the simulated results,a propotype of the antenna is fabricated and measured.Good agreements can be obtained between the simulated and measured results.The overall dimension of the proposed antenna is 160×160×31mm³.The measured results show that the proposed antenna has a waide impedance bandwidth,good circularly polarization characteristics and gains of greater than 5.7dB within the required operating band.