The Design Of Multi-Mode Global Navigation Satellite System Antenna

The Global Navigation Satellite Systems are popular with people in their daily life, therefore many countries have set up to build their own navigation systems. Until now, American and Russian have finished the construction of navigation systems, they have used the systems for many years. Beidou I navigation system of China has been built up and Beidou II or Compass is under construction now. Europe is in their way of developing the Galileo system. Up to year2020, there will be four navigation systems:GPS (American)/GLONASS (Russian) /Galileo (Europe)/Compass(China). All the four systems can work respectively, however, the sole system has the defects of low precision, lack of integrate, reliability and continuity. Due to the orbits of the satellite are different, if the four GNSS systems were combined together, the terminal can receive more satellites, therefore the precision and reliability can improve greatly, especially in the case of urban canyon and jungle when the signals are attenuated seriously. So multi-mode navigation is a trend, and the chipsets for multi-mode terminals have always appeared in the market. There is a urge demand of the multi-mode antennas for the navigation systems.The working frequency of the four GNSS systems range from1163.72 MHz～1605.375 MHz, and the signals from the navigation satellites are all right hand circularly polarized. In this article, two circularly polarized antennas and their feed network are investigated. The first one is two-feed, and the second one is four-feed. The other parts of the two antennas are same. By introducing air layer, parasitic patch and adopting stacked structure, the circularly polarized bandwidth is enlarged effectively. For the two feeding method, the feed network is composed of a Wilkinson power divider and Composite Right/Left-Handed Transmission Line. For the other antenna, four feeding method is adopted for suppressing the higher modes and increasing the 3dB axial ratio (AR) bandwidth. A broadband phase shifter with 0°,90°,180°,270°are analysised and designed. For the four feeding method, simulated results show that the-10dB impedance bandwidth is up to 51.6%, which can cover the whole GNSS frequency.