Design Of BeiDou Navigation Antenna Based On Metamaterials

BeiDou navigation satellite system（BDS）is a satellite navigation system independently developed by China.With the successful launch of the last Beidou-3 satellite in 2020,BDS has come to an end,and research on its application has become the main task of future development.As one of the most important radio frequency components in BDS receiver/transmitter,the performances of the antenna directly affect the quality of the communication system.In satellite communication systems,circularly polarized antennas are often used to increase the reliability of signal reception.At the same time,it can overcome the influence of Faraday rotation and has a strong ability to resist rain and fog interference.At present,the antenna forms widely used in satellite navigation systems mainly include microstrip antennas and helical antennas.In recent years,there have been more and more research reports on metamaterials.Using the novel properties of metamaterials to design antennas not only brings opportunities to the design of new antennas,but also faces great challenges.In this thesis,the metamaterial circularly polarized antennas used in BDS have been studied,and the following results have been achieved:（1）A right-handed circularly polarized antenna based on Composite Right/Left-Handed（CRLH）Transmission Line is designed to receive navigation signals in the B1（1561 MHz±2.046 MHz）band of BDS.The antenna is a double-arm circular loop antenna composed of two types CRLH transmission line units.The outer ring is composed ofΓ-type elements,the inner ring is composed of I-type elements,and the antenna is fed through a single-point.The measured results show that the antenna can receive right-handed circularly polarization wave,and the|S₁₁|at the operating frequency of 1.561 GHz is approximately-13 dB,with a 3-d B axial ratio lobe width of 114°,a 3-d B axial ratio bandwidth of about 7.4%,and a gain of about 5.61 d Bic,which meet the requirements of BDS for navigation antenna.（2）Based on the metamaterial structure,a dual-band dual-circularly polarized short message communication antenna for BDS is proposed and designed.The antenna is a single-arm planar spiral composed of 16 I-type elements and 17Γ-type elements,and a single-point feeding method is used for the antenna.The CRLH transmission line has negative phase shift constant and positive phase shift constant in different frequency bands,respectively,so was used to realize the characteristics of radiating/receiving left/right handed circularly polarized waves in Beidou L-band/S-band respectively.The measured results show that the antenna radiates a left-handed circularly polarized wave at a frequency of 1.615 GHz with a gain of about 3.6 d Bic,and in the L-band,the bandwidth of|S₁₁|<-10 d B is approximately 8%,and the bandwidth of axial ratio less than 3 d B is about 6%.The antenna receives a right-handed circularly polarized wave at a frequency of 2.492 GHz,the gain is about 4.85 d Bic,and in the S-band,the bandwidth of|S₁₁|<-10 d B is approximately 12%,the bandwidth of axial ratio less than 3 d B is about 5.5%,which meets the requirements of BDS for short message communication antenna.（3）A two-stage cascaded broadband low-noise amplifier（LNA）is designed using Avago’s ATF series p HEMT,and its working frequency band covers the B1-band and the S-band.In order to obtain broadband characteristics,a parallel resistive negative feedback structure is adopted,and a low-Q matching network is selected for the matching network of each stage to obtain broadband characteristics.The measured results show that the operating frequency band of this LNA is 1.5 GHz～2.6 GHz,the noise figure in the operating frequency band is less than 2 dB,and the in-band gain is 30±1 dB,which meet the design requirements.