A Compact Circularly Polarized Patch Antenna with Series Sequential-Phase Feed Network

A compact circularly polarized (CP) patch antenna with Series Sequential-Phase feed network is proposed in this paper. The antenna structure is mainly composed of a square patch, an array of parasitic metal plates symmetrically positioned around the patch, and a series sequential-phase (SP) feed network as feeding structure. A series SP feeding network provides four signals of equal magnitude and quadrature phase for proposed antenna. The parasitic element provides greater freedom for impedance matching of the antenna. The overall size of the antenna is 0.57 λ × 0.57 λ × 0.071 λ (λ is the free-space wavelength at the lowest frequency). The impedance bandwidth for S11 < -10 dB reaches 36.71% (1.49 - 2.16 GHz), and the axial ratio bandwidth for axial ratio < 3 dB reaches 13% (1.58 - 1.80 GHz). The peak gain of the antenna reached 7.56 dBic.