A Quad-Band Dual-Sense Circularly-Polarized Square-Ring Antenna for Multi-Functional Wireless Applications

A quad-band dual-sense circularly-polarized (CP) antenna is presented for multi-functional wireless applications. Initially, the corner-fed square-ring radiator is designed with one end open-circuited. The surface currents flow along the circumference of the square-ring, which excite dual-band dual-sense CP radiation with a right-hand circular polarization (RHCP) at one frequency band and a left-hand circular polarization (LHCP) at the other band. Later, a rhombic-shaped slot and an inverted V-shaped parasitic element, used to balance the surface currents in horizontal and vertical directions at the middle and low frequency regions, excite two additional LHCP bands. The proposed antenna is systematically presented through a CP generation principle, a surface current distribution, and parametric analysis. The measured results yield an impedance bandwidth (IBW) of 83.9% (2.33-5.70 GHz) and the 3-dB axial ratio bandwidths (ARBWs) of 7.3% (2.38-2.56 GHz), 9.0% (2.75-3.03 GHz), 3.7% (3.42-3.53 GHz), and 7.1% (5.16-5.54 GHz). The maximum broadside gains achieved within the axial ratio bandwidths are 2.5, 2.9, 3.4, and 2.7 dBi, respectively. Compared to other reported works considering quad-band CP radiation, the proposed antenna achieves a wider ARBW and smaller size. To the best of the author's knowledge, the proposed work is the first paper presenting a planar quad-band dual-sense CP antenna for WLAN (2.5/5.3 GHz), WiMAX (3.5 GHz), and Marine Service (3.0 GHz) wireless applications.