Novel Design Approaches to Planar End-Fire Dual-band Circularly Polarized Antennas

In this paper, two design schemes for planar end-fire dual-band circularly polarized antennas (PEDBCPAs) are proposed. In the first scheme, a cavity is first used to achieve dual-band characteristic with vertical polarization, and then a rectangular loop and a planar printed dipole are employed to provide horizontal polarizations at 2.40 GHz and 5.0 GHz. Finally, a dual-band circularly polarized antenna with large frequency ratio is achieved. In another scheme, a single-band planar end-fire circularly polarized antenna is realized by using a cavity and a rectangular loop, and then a smaller inner loop is introduced to realize a dual-band circularly polarized antenna at 2.66 GHz and 2.74 GHz with a small frequency ratio. Both two designs do not introduce the extra phase shift line structure, and realize the PEDBCPAs with large and small frequency ratios.