Tri-band planar monopole antenna with two circularly polarised bandwidths for WiMAX applications

摘要

A tri-band planar monopole antenna with one linearly polarised band, two circularly polarised bands, and bidirectional radiation patterns is presented in this study. The antenna consists of a monopole with seven arms etched on the top side of a FR4 substrate, and a slitted ground plane on the bottom side. Measured results show that the antenna has aS₁₁<−10 dB impedance bandwidth of 9.7% (2.05–2.26 GHz) for the lower band, 11.3% (3.41–3.82 GHz) for the middle band, and 60.2% (4.89–9.11 GHz) for the upper band. The circular polarisation (CP) is radiated within the middle (left hand CP) and the upper (right hand CP) bands, and the measured broadside 3 dB axial ratio bandwidths are 4.9% (3.53–3.71 GHz) and 58.6% GHz (4.69–8.58 GHz), respectively. The proposed antenna has a total size of 25 × 35 × 1.6 mm^{3and can be employed for the 2.1 GHz UMTS, whereas the CP bands can be used for the 3.5/5.5 GHz WiMAX, 5.5 GHz Wi-Fi, and 5.2/5.8 GHz WLAN applications.}