A NOVEL PATCH ARRAY ANTENNA WITH WIDEBAND AND DUAL SENSE CIRCULAR POLARIZATION CHARACTERISTICS FOR WIMAX & WLAN APPLICATIONS

A wideband patch array antenna with dual sense circular polarization (CP) is investigated in this paper. Four rotated hexagonal patches are sequentially distributed on the upper surface of substrate 1 to form a patch array. In order to widen impedance bandwidth, an annular feeding network with four rectangular branches is designed. At the bottom of the antenna, two orthogonally placed microstrip baluns are introduced to obtain the characteristics of left-hand circular polarization (LHCP) and righthand circular polarization (RHCP). Meanwhile, four coaxial probes, passing through substrate 2 and substrate 3, are used to transmit the feeding signal between microstrip balun and the annual feeding network. The proposed patch array antenna is fabricated for verifying the feature of wideband and dual circular polarizations. The measured results show that the antenna has an impedance bandwidths of 70.2% (1.72–3.58 GHz) with an axial ratio (AR) bandwidth of 61% (1.85–3.48 GHz) and over 6.2 dBi gain at two ports. Moreover, the measured port isolation remains below −15 dB over the entire impedance bandwidth, and the measured radiation patterns with excellent directionality and symmetry at two ports indicate that the proposed antenna can be used for wireless applications.