Research On Wideband Multi-Polarization Microstrip Slot Antenna

Wideband multi-polarized antenna can effectively reduce the multipath fading effects,increase the transmission rate and channel capacity.The miniaturized microstrip slot antenna can provide strong support for system integration,cost reduction,and conformal requirements.This dissertation focuses on realizing and improving the broadband and multi-polarization characteristics of the microstrip slot antenna.The main novelty works by the author are summarized as follows:Firstly,an ultra-wideband orthogonal dual-polarization vivaldi-like slot antenna based on 1-wavelength resonance mode is designed and studied.A bidirectional vivaldi slot with closed termination is desiged to expand the antenna bandwidth;the rectangular parasitic patches on the ground increase the equivalent length of the slot,and guide the surface current path to adjust the impedance matching;the stepped microstrip feed lines are connected with the "air bridge" to improve the port isolation.The measured results show that the antenna's impedance bandwidth exceeds 90%,the average port isolation is greater than 32 dB,and the average realized gain is more than 2.6 dBi,achieving good dual-polarization characteristic.Secondly,an ultra-wideband circularly polarized Vivaldi-like crossed slot antenna is designed and studied.Based on the ultra-wideband orthogonal dual-polarization vivaldi-like slot antenna,the circularly polarized radiation is realized by adding lumped capacitances and inductances to adjust the phase difference.Changing the relative positions of the capacitances and inductances,the conversion between left-hand circular polarization and right-hand circular polarization can be achieved.The rectangular parasitic patches work as directors,changing the surface current pathes and greatly broadening the impedance bandwidth and axial ratio bandwidth of the antenna.The antenna prototype was fabricated and measured.Results show that the antenna achieves an impedance bandwidth of 97.01% and an axial ratio bandwidth of 58.94%,and the average realized gain is 2.4 dBic.Meanwhile,the antenna embodies compact size and low profile characteristics.Thirdly,a wideband low profile multi-polarization reconfigurable antenna based on the quasi-cross-shaped slot is studied and designed.Firstly,based on the application background of 5G wireless air interface communication test system,a broadband high-isolation dual-polarization antenna with quasi-cross-shaped coupling slot is designed.The quasi-cross-shaped slot and fork-shaped feedlines are designed to satisfy the high-isolation requirement.The antenna cavity further enhances the realized gain and front-to-back ratio,also improves the mechanical strength.The measure results show that the antenna exhibits good performance in wide impedance bandwidth(20.3%)and high isolation(greater than 40 dB)with the average realized gain of 8.3 dBi.Finally,based on the broadband high-isolation dual-polarization slot antenna,a polarization reconfigurable slot antenna is designed and studied.The antenna polarization modes varies among +45° linear polarization,-45° linear polarization,±45° dual linear polarization,left-hand circular polarization and right-hand circular polarization by placing four pairs of PIN diodes in four different branches of the reconfigurable Wilkinson power divider network,so as to control the excitation amplitude and phase of the slots in different directions.The measure results show that the antenna obtains more than 21.35% linear polarization impedance bandwidth and 17.70% circular polarization impedance bandwidth,and the left-hand circular polarization and right-hand circular polarization axis ratio bandwidths are 16.13% and 16.88%,respectively.The average realized gain of the antenna exceeds 7.6 dBi.Lastly,the polarization reconfigurable antenna array is designed.And simulation results prove that the antenna array has multi-polarization and high integration characteristics.