Research On Miniaturization Of UWB Directional Antenna

With the rapid development of various wireless communication technologies,the antenna design,as an important part of its product development,is facing increasing challenges.The realization of wide bandwidth with more and more limited design space has become a research hotspot.In order to increase the anti-interference ability and effective radiation power of the antenna,the antenna is required its good directivity.In the 1950s,the concept of frequency independent was proposed.It allows the bandwidth of the antenna to be infinitely wide theoretically.Log-periodic antennas and planar spiral antennas are ultra-wideband antennas with frequency independent characteristics.The performance of the two antennas is high over a wide bandwidth.Based on the above research background,this thesis mainly studies the Log-Periodic Dipole Antenna?LPDA?and planar spiral antenna.1.The research on the LPDAAccording to the research on miniaturization technology of LPDA,a planar LPDA with bandwidth of 1GHz¹0GHz is designed.According to the calculation of input impedance,the effects of the design parameters of the bent dipole on the input impedance are analyzed.The variation of antenna performance with miniaturized structural parameters is discussed.Optimized for the miniaturized structure of the antenna,the antenna width is reduced by 25%,and the antenna still has high performance.In the actual measurement,it was found that the welding of the SMA connector and the antenna feed port would cause a lot of interferences,which caused the S₁₁ parameter could not meet the expected standard.Therefore,a balun structure is designed for the antenna.The simulation results show that the balun and the connector have an effect on the radiation of the antenna,but the balun improves the S₁₁ parameter of the antenna.The antenna maintains high performance over the entire bandwidth.2.The research on composite structure spiral antennaAccording to the research on the miniaturization technology of planar spiral antennas,a miniaturized structure combining the bending the antenna arm and loading the metal ring is proposed.This structure further reduces the size of the antenna.The influence of the structural parameters on the antenna performance was analyzed,and the antenna radius was reduced by 28%.In order to achieve unidirectional radiation of the antenna,the reflection cavity of the antenna is studied.Analyzing the variation law of the antenna radiation area with frequency,a multi-layer circular table reflection cavity is designed for the antenna.The antenna will reduce the bandwidth and increase the gain after loading the reflective cavity.Optimizing the structure of the reflective cavity,the antenna achieves unidirectional radiation over a wide bandwidth.