Dual‐band circularly polarized microstrip antenna

Abstract

ABSTRACT A design for dual‐band circularly polarized microstrip antennas with different radiation patterns is described. The design is based on a stacked patch antenna composed of an upper circular patch and a lower ring patch. For the higher operation band, the two patches are simultaneously resonant at the TM 21 mode and the stacked patch antenna can produce a conical radiation pattern. As for the lower operation band, only the upper patch is resonant at its fundamental mode and a broadside radiation pattern is obtained. To allow the two radiation patterns to be with circular polarization, 90° hybrid couplers are used to excite the patch antennas at the two operation bands. A prototype designed at the GPS and WLAN bands is constructed. The experimental results demonstrate that the prototype operated at each frequency band has a 3dB‐axial‐ratio bandwidth of more than 15%. Simulation performed with HFSS also validates the measured results. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:404–408, 2017