The Study Of Antenna For Multi-Mode Airborne Satellite Navigation System

Satellite navigation system is widely used in various fields with its advantage of global navigation,positioning,timing,and velocity-measuring.At present the global satellite navigation system contains GPS(Global Position System),GLONASS(Global Navigation Satellite System),GALILEO and COMPASS.To solve the problems of coverage gap with single system and low navigation precision,multi-mode cooperation will be the trend for satellite navigation system in future.The antenna used in airborne satellite navigation system is required to cover GPS, GALILEO and COMPASS systems.Its frequency band is 1164～1559MHz,and relative band width is 29%.Its polarization should be RHCP(Right Hand Circular Polarization). Microstrip antenna is a good choice for satellite navigation system,because it has some principal advantages,such as small size,light weight,low profile and so on.But the relative band width of normal microstrip antenna is only about 5%,which obviously cannot satisfy the bandwidth request of the multi-mode cooperation.Therefore,the key points in this paper lie in the studies of the broadband technology of microstrip antennas. Then a novel broadband circularly polarized patch antenna is designed successfully.The proposed antenna is composed of two stacked patches with annular aperture coupled feeding network to achieve wideband characteristics.The simulation and measured results show that the impedance bandwidth for VSWR＜2 is more than 50%,and 3-dB axial ratio bandwidth is 48.6%.A peak gain of around 5dB is obtained in the entire bandwidth.It meets the demands of the multi-mode airborne satellite navigation system.The received signal power sent from satellite is quite weak.So enhancing antenna gain is needed to achieve high efficiency.In addition,to limit the EMI and get high receiving sensitivity,the designed antenna should be null steering in the interfere directions.Hence,array antenna designing is necessary. In this paper,we summarized the basic concept of antenna array,and proposed the digital filter function weighted algorithm for beam control.It includes filter function in digital signal processing.The amplitude and phase controlled function can be achieved by Fourier transforming.Finally,the feasibility of proposed algorithm was verified well in MATLAB.