| Global Navigation Satellite System(GNSS),as a represent of the top communication,attract much more attention of many countries with the rapid development of communication technology.the antennas of GNSS are mostly made with circular polarized ones,because circular polarized antennas own the characteristic of high precision,strong ability of anti-interference,wide field of application etc.Axial ratio(AR)is one of the most important parameters.The smaller AR,the higher the efficiency to receive the signal from the satellites.Besides,it is supposed to design an antenna to cover different frequency bands in GNSS.Some measured should be taken to restrain the multi-path interference and self-interference.Thus,it is the main points of the article to design a CP antenna with wider band,lower multi-path interference and AR.The main work is listed as follows1.By reading articles at home and abroad,we analyze the present research status of wideband CP antennas,methods to low multi-path interference and AR.Hotpoint at present,problems faced,and the possible research orientation are summarized as well.How to design an antenna that can realize wideband,lower AR and multi-path interference is also provided at last.2.A feeding network with novel structure and excellent performance is proposed firstly.A new closed power divider is introduced to the feeding network to realize the phase difference among four ports range in 90°±5°and the amplitude difference lower than 1dB in the frequency band of 1.1-1.65 GHz.Based on the designed feeding network,we simulated and measured a GNSS antenna which radiates mainly by sectors with corner cuts.The antenna owns the characteristics of a wider 3-dB AR beamwidth,wider band,lower multi-interference.The 3-dB AR beamwdith at 1.175 GHz and 1.575 GHz are 160° and 180° respectively and the operating frequency band(S11<-10dB)covers 1.1-1.8GHz.3.An antenna is proposed with smaller and simpler rectangles as radiators,and a cylinder connected to the circular ground is introduced to reduce the AR and expand the 3-dB AR beamwidth.The GNSS antenna in this chapter with the performance of low AR,stable gain,high return loss,low multi-path interference is simulated and measured.The measured results show the antenna can work at 1.15-1.62 GHz,in which operating band the S11<-14 dB,AR<1dB,gain range in 5.2dBi and 6.5dBi.4.A new radiating structure is designed with the feeding network and a parasitic circular metal is introduced as a top load to balance the gain of RHCP.The coupling between the parasitic circular metal and the triangle metal is used to adjust the match of the antenna,which can reduce the size of the antenna greatly and keep the excellent performance at the same time,the new structure has much more advantages compared with the antenna mentioned in last chapter.Two antennas with different features are designed to apply different environment,antenna 1 owns small size,stable gain,wide and low AR-beamwidth,and high return loss;while the antenna 2,of which the volume size is ?104*15.8mm3,has a much low profile and works well in the GNSS band.The antenna 1has been fabricated and measured partly so far. |
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