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Abstract A wideband circularly polarized (CP) cross‐dipole antenna with folded ground plane is presented. The antenna consists of an L‐shaped stepped patch as driven elements and four rotated L‐shaped metallic ground strips as parasitic elements. A sequential phase feeding structure is used to provide 90° phase difference, which is composed of a pair of vacant‐quarter printed rings. It is noticed that the four rotated parasitic L‐shaped metallic ground strips and ground plane are directly connected to form a folded ground plane instead of the traditional disconnection between parasitic elements and ground plane. By using these elements, multiple CP resonances can be excited to meet the requirement for the wideband CP radiation. The presented antenna shows outstanding CP feature with a broad axial‐ratio bandwidth (ARBW) of 85.7% (1.3–3.25 GHz) and a wide impedance bandwidth (IBW) of 100% (0.95–2.85 GHz).

A broadband circularly polarized (CP) cross-dipole antenna with multiple modes is proposed. The antenna is composed of two pairs of crossed strip dipoles as driven elements, four square-slot patches, and four corner-truncated patches as parasitic elements. A pair of vacant-quarter printed rings is used as sequential phase feeding structure to generate a CP mode, which connect to crossed strip dipoles. By using these coupled rotated elements, multiple CP modes can be stimulated to satisfy the need of broadband CP radiation. In addition, four shorted square metal columns are also introduced in the antenna design to generate an additional CP resonance. A verified prototype was fabricated and measured in this paper. The measured results demonstrate the proposed antenna features wideband CP characteristics with a wide impedance bandwidth (IBW) of 95.5% (0.92-2.60 GHz) and a broad axial-ratio bandwidth (ARBW) of 94.4% (0.95-2.65 GHz).

A wideband circularly polarized (CP) cross-dipole antenna with parasitic elements is proposed. The proposed antenna consists of a pair of driven crossed strip dipoles, two kinds of parasitic elements (inner and outer parasitic elements), and a pair of vacant-quarter printed rings. The driven crossed strip dipoles can generate a CP mode due to the sequential phases given by the vacant-quarter printed rings. Another CP mode can also be stimulated by placing these parasitic elements to the edge of crossed strip dipoles. By combining with two CP modes of the cross-dipoles, the proposed antenna achieves a wideband CP performance. The measured results indicate that the proposed antenna exhibits wideband CP characteristics with an impedance bandwidth (IBW) of 77.6% (1.11 - 2.52 GHz) and axial-ratio bandwidth (ARBW) of 66% (1.25 - 2.48 GHz). The proposed antenna would be suitable for CP applications in wireless communication systems, such as the global positioning system (GPS; 1.575 GHz) and wireless broadband access service (WiBro; 2.3 - 2.39 GHz).