Small planar monopole antenna with a shorted parasitic inverted-L wire for wireless communications in the 2.4-, 5.2-, and 5.8-GHz bands

A low-profile planar monopole antenna with a shorted parasitic inverted-L wire fed using a microstrip feedline for wireless communications in the wireless local-area network (WLAN) bands is studied. The driven monopole element and shorted parasitic wire can separately control the operating frequencies of two excited resonant modes, which cover the 2.4-, 5.2-, and 5.8-GHz WLAN bands. This antenna design is not only suitable as a monopole antenna but also as a diversity antenna for 2.4-, 5.2-, and 5.8-GHz band operations. The lower mode of the proposed antenna has an impedance bandwidth (2:1 VSWR) of about 188 MHz (2313-2501 MHz), which covers the required bandwidth for 2.4 GHz WLAN band (2400-2484 MHz); on the other band, the upper mode has a bandwidth of about 2843 MHz (3930-6773 MHz) covering the HIPERLAN band (5150-5350 MHz) and 5.8-GHz WLAN band (5725-5852 MHz). For frequencies across the three operating bands, the proposed antenna shows similar monopole-like radiation patterns, and good antenna gain across the operating bands is obtained. Details of the design considerations for the proposed antenna are described, and the experimental results of the antenna performances obtained are presented and discussed.