Compact ultra-wideband circularly polarized CPW-fed monopole antenna

This paper presents a coplanar waveguide (CPW) -fed quadrilateral-shaped compact planar monopole antenna for ultra-wideband (UWB) application. The fractional axial ratio bandwidth (ARBW) of the antenna for circular polarization (CP) is 56.64% (5.91–10.58 GHz) and its fractional impedance matching bandwidth (IMBW) is 137.1% (3.1–17.5 GHz), which are realized by designing a quadrilateral-shaped monopole with an asymmetric ground plane. The proposed antenna structure is simple and compact; hence its design is efficient, and it has an impedance matching (S11) in UWB band with embedded wideband circular polarization. The gain of the antenna varies between 3.33 and 8.9 dBi. Furthermore, its application for designing the linear array and planar array of 1 × 2 and 2 × 2 antenna elements are presented. The gain improves to 5.1–9 dBi for 1 × 2 array elements and to 9–11.2 dBi for 2 × 2 array with UWB IMBW. Simulated and experimental results are presented to validate the antenna design and are shown to be in good agreement.