A circularly polarized pattern diversity antenna for hemispherical coverage

In this communication, a circularly polarized (CP) antenna is proposed for satellite communication applications. The proposed antenna consists of two parts. One part is in-phase-fed folded monopoles with omnidirectional CP radiation pattern, and the other part is sequential-fed L-shaped monopoles with broadside CP radiation pattern. By combining the two parts as a pattern diversity antenna, upper hemispherical coverage with left-handed circular polarization (LHCP) is achieved in a small volume of 0.38λ x 0.38λ x 0.071λ (λ is the free-space wavelength). A prototype of the proposed antenna operating at 1.575 GHz has been built and tested. The measured overlapping bandwidth for both the two patterns with -10-dB impedance bandwidth and 3-dB axial-ratio (AR) is 6.7% (1.515-1.62 GHz), also with high port isolation. In addition, the AR and gain coverage over the upper hemisphere is discussed in detail.