| Global navigation satellite systems use satellite signals to provide users with high-precision,efficient,safe and reliable positioning,navigation and timing services.Many countries and regions in the world have autonomous satellite navigation and positioning systems.For a country,having its own satellite navigation system not only enhances national defense power,it is also a booster for national economic development.It is the manifestation of comprehensive national strength for a country.For decades,with the rapid development of space technology,wireless communication technologies,and large-scale integration technologies,the development of global navigation satellite systems has reached a new height.In order to improve the accuracy and reliability of navigation and positioning,satellite navigation systems are developing toward the direction of compatibility of multiple systems and multiple modes.Therefore,it is of great practical value and practical significance to study antennas that can operate in multiple satellite navigation system frequency bands.The microstrip antenna has small size,low mass,low profile height and is easy to integrate with the system.It can generate a wide beam in a specific direction.These unique properties make the microstrip antenna the first choice for satellite navigation system antennas.Antennas for multimode satellite navigation systems require that antennas be able to operate in the bands of multiple navigation systems.The frequency range is 1164MHz-1300 MHz and 1559MHz-1610 MHz.Antennas are required to have a wider beam in the upper half plane,generating right-hand circularly polarized radiation.This thesis firstly introduces the basic structure,radiation mechanism and analysis method of the microstrip antenna,and then studies the broadband technology and circular polarization technology of the microstrip antenna.Based on this,three antennas suitable for satellite navigation terminals were designed using commercial electromagnetic simulation software HFSS:1.A coaxial single-feed dual-frequency GPS terminal antenna was designed using a double-layer laminated microstrip radiating patch structure.The upper and lower two-layer patches generate dual-frequency radiation in the L1 and L2 frequency bands of the GPS.Angles is cut form the two-layer square radiation patch to generate micro-wrapped separating elements,which can achieve circularly polarized radiation.The antenna uses a low-temperature co-fired ceramic(LTCC)with a large dielectric constant,which greatly reduces the size of the antenna to meet the miniaturization requirements of the terminal equipment.The simulation analysis results show that the antenna has impedance bandwidths of 20 MHz and 18 MHz,respectively,in the L1 and L2 bands of the GPS.The axial ratio in the working band is less than 4d B.2.A multi-point feed wide-band satellite navigation system antenna with four coaxial probes was designed using a radiating structure of a double layers circular patch.The parameters of the radiating patch were adjusted so that the resonance points of the two patches were close to each other to effectively increase the bandwidth of the antenna,in the interior of the antenna,a circular coupling patch is added on the top of the coaxial probe,and the impedance bandwidth of the antenna is further improved by adopting the electromagnetic coupling feeding method.The four feed probes have equal signal amplitude and phase lag by 90 degrees.The symmetrical structure of the entire antenna greatly improves the circular polarization purity.The simulation results show that the-10 d B impedance bandwidth of the antenna can reach 63.4%(1.12GHz-2.16GHz),and the axial ratio in the frequency band is less than 2.6d B,the circular polarization performance is better,covering the frequency bands of the main global satellite navigation systems.3.Based on the basic PIFA structure,a novel wideband circular polarization printed antenna was designed.Another branch was added above the original radiation branch of the PIFA structure.The structural parameters of the branch were adjusted so that the resonance frequencies of the two branches were close to each other.The purpose of widening the bandwidth is achieved;circular polarization is obtained by adding a linear micro-reel structure at a corner of the triangular ground plane.The working frequency band of the antenna(1.10GHz-1.72GHz)covers the working frequency bands of several satellite navigation systems.The circular polarization performance of the antenna is good.The antenna has a simple structure and a geometric size of less than 95 mm.It is suitable for small-scale terminal equipment of multimode satellite navigation systems. |
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