Design And Analysis Of Compact Wideband Directional Antennas

In order to reduce the complexity of the wireless system,the compact wideband antenna is the trend of future development.The compact wideband directional antenna has the characteristics of easy to assembly,easy to measurement,and wide coverage band range.It has important application value and research significance in the field of mobile communication and microwave measurement in small microwave chamber.In this paper,two compact wideband directional antennas are designed,which are a wideband directional antenna with a compact longitudinal size and a wideband directional antenna with a compact horizontal size.The designed wideband directional antenna with a compact longitudinal size consists of an active dipole,a director and a reflector.The active dipole is a combination of a printed slotted electric dipole and a magnetic dipole to increase the impedance bandwidth of the antenna.The director is also a combination of a printed slotted electric dipole and a magnetic dipole,which can suppress the splitting of the beam at high frequency band and improve the impedance matching of the antenna.The elliptic cylindrical reflector can play a role in suppressing the side lobe.The wideband directional antenna with a compact longitudinal size has a operat img bandwidth of 115%(0.75-2.8 GHz),the gain is greater than 5 d Bi,the side lobe level is lower than-10 d B,the front-to-back ratio is greater than 10 d B,and the longitudinal size is 0.155 times the wavelength corresponding to the lowest operating frequency.The designed wideband directional antenna with a compact horizontal size consists of a dielectric rod made of PTFE,a gradient ridged waveguide and a coaxial-ridged waveguide stepped feed structure.The PTFE dielectric rod includes an electromagnetic wave transmission section and a radiation section.The radiation section mainly uses a main mode HE11 mode in a small-circle-sized circular dielectric waveguide to generate a low-sidelobe high gain pattern,and the transmission section of a four-sloped waveguide-dielectric transition structure improves the impedance matching of the antenna.The coaxial-ridged waveguide stepped feed structure uses parallel feed to achieve a wider feed bandwidth and does not increase the antenna's horizontal size.The simulated bandwidth of the wideband directional antenna wi th a compact horizontal size is 75.9%(18-40 GHz),the gain is greater than 10 d Bi,the side lobe level is lower than-10 d B,the front-to-back ratio is greater than 15 d B,and the horizontal size is 0.51 times the wavelength corresponding to the lowest op erating frequency.The measured results show that the bandwidth is 21-37 GHz(55.2%).The above two compact wideband directional radiation antennas were simulated and optimized by CST Microwave Studio? electromagnetic simulation software,and the antennas were fabricated.The Agilent N5227 A vector network analyzer was used to measure the antennas.The measured results showed that the simulated results are in good agreement and the correctness of the des ign is proved.Both antennas have achieved compact structures.Both antennas have achieved compact structures.Among them,the wideband directional antenna with a compact longitudinal size is suitable for the use in the field of mobile communications.The wideband directional antenna with a compact horizontal size is suitable for microwave measurement in small microwave chamber.