A dual-band circular polarized CPW fed low-profile antenna for WLAN and X-band applications

• A small square shaped CPW asymmetric fed antenna with rectangular patch. • A semicircular disc shaped parasitic element is etched out from the rectangular patch to initiate circular polarization and dual band operation. • On the right side of the ground plane, a dumbbell shaped slot at the bottom and an extended stub at the top corner produces dual circular polarization. • An inverted U-shaped slit inside an inverted L-shaped stub brings CP resonance at the desired lower operating frequency. • Narrow CP response at both the operating frequencies. In this work, a compact asymmetric CPW-fed monopole antenna is designed to operate at dual-band with dual circular polarization. The design comprises a rectangular patch with a semicircular disc-shaped parasitic element to achieve circularly polarized (CP) behavior. Additionally, a vertical notch is incorporated at the bottom left corner of the ground plane to generate a strong horizontal field component. On the left side ground plane, an inverted L-shaped stub is positioned vertically to enable dual-band operation. A dumbbell-shaped slot is etched at the bottom of the right-sided ground plane, and a corner stub extends at the top to support dual CP at both the frequencies. Furthermore, incorporating a U-shaped cut into the inverted L-shaped stub improves the CP resonance at the desired lower operating frequency. The proposed antenna shows an impedance bandwidth (IBW) of 4.38 GHz - 6.22 GHz for the lower band and 7.37 GHz - 11.78 GHz for the higher band, with an axial ratio bandwidth (ARBW) of 5.13 GHz - 5.67 GHz at the lower band and 9.95 GHz - 11.02 GHz at the higher band. The structure is built on an FR4 substrate with a relative permittivity of ε r = 4.4, with an overall dimension of 0.43λ 0 ×0.43λ 0 ×0.02λ 0 , where λ 0 represents the free-space wavelength at 5.2 GHz. This antenna achieves a peak gain of 3.55 dBi at 5.2 GHz and 4.97 dBi at 10.4 GHz, making it suitable for WLAN and X-band applications.