CP higher-order mode annular-ring microstrip antenna for mobile satellite communication

A TM₂₁-mode circularly polarized (CP) annular-ring microstrip antenna (ARMSA) is presented. The antenna adopts single-point feeding and has a conical radiation pattern. The CP performance is implemented by a pair of symmetric slits at inside boundary of the annular ring. When the angular spacing between the feeding point and slits are 26.5° and 153.5°, the best CP performance is obtained. The results indicate the antenna has high low-elevation-angle gains and omnidirectional azimuth coverage. At 1.605GHz, the peak gain reaches 4.4dBic at elevation angle of 47°, and in the range of 10°-70°, the gain is above 0dBic. In addition, the impedance bandwidth for S₁₁<; -10dB is 40MHz (2.5%). The characters of the proposed antenna can meet the application of mobile terminals on satellite communication and navigation.