On The Design Of Broadband GNSS Antennas With Stable Phase Center

As we know,many applications for Global Navigation Satellite System(GNSS)require high-precision positioning.In order to realize this goal,high-performance GNSS antennas are indispensable.Therefore,design of wideband circularly polarized(CP)antennas,which yield stable phase center within wideband and wide beamwidth simultaneously,is an urgent issue for high-performance GNSS.This thesis focuses on wideband CP antennas with stable phase center for high-performance GNSS terminals,besides,beamwidth widening technology and miniaturization technology are studied as well.The research contents include:1.The simulation method of phase center and its stability.Based on High Frequency Structure Simulator(HFSS),an effective method aiming at computing antenna mean phase center(MPC)and phase center variation(PCV)has been presented.By studying the MPC and PCV of dipole antenna,we verify the effectiveness of the proposed simulation method.Besides,based on the phase response of dipole,design principle to realize stable antenna phase center has been proposed.2.The design of wideband microstrip CP antennas with stable phase center based on crossed-slot structure.A crossed-slot antenna has been proposed where each slot can be treated as a magnetic dipole.By optimizing the position and geometry parameters of the offset feeding structure,wideband stable phase center for this antenna is obtained,as well as wideband CP performance.The measurement results demonstrate that,the-10-dB impedance bandwidth(IBW)and 3-dB axial ratio bandwidth(ARBW)range from 1.03-2.0 GHz.The simulated phase response demonstrates that,over the whole GNSS bands,phase center deviation(PCD)retains below 4.3 mm and phase center variation(PCV)above 10°elevation keeps below 5°(viz.,3.6 mm).3.The design of wideband CP antennas with wide beamwidth and stable phase center based on crossed-dipole structure.To challenge wide beamwidth and stable phase center over wide bandwidth,a novel center-fed crossed-dipole CP antenna is proposed.By adding the parasitic metallic plates on the reflector,wideband CP performance,wide beamwidth,and stable phase center are realized simultaneously.Based on current path,monopole pattern,and monopole phase pattern,antenna mechanism is studied in detail.The measurement results demonstrate that,the-10-dB IBW and 3-dB ARBW range from 1.1-1.88 GHz.The simulated phase response demonstrates that,over the whole GNSS bands,PCD retains below 1.1 mm and PCV above 100°elevation keeps below 3°(viz.,2.1 mm).4.The study on antenna miniaturization based on fragment structure.This thesis challenges the design of miniaturized GNSS antenna with stable phase center based on fragment structure and MOEA/D combined with genetic operators(MOEA/D-GO).The simulated results demonstrate that,antenna size is reduced by 15 mm compared to the crossed-dipole antenna,whereas,the-10-dB IBW and 3-dB ARBW range from 1.1-1.73 GHz,covering the whole GNSS bands.Besides,over the whole GNSS bands,PCD retains below 1.2 mm and PCV above 10°elevation keeps below 3°(viz.,2.1 mm).