A wideband omnidirectional planar microstrip antenna for WLAN applications

A novel wideband omnidirectional planar microstrip antenna is designed, fabricated and measured in this paper. The proposed planar array of collinear printed dipoles is composed of a series of sections of microstrip line with their top and bottom conductors transposed at each junction. Without any alteration to the microstrip radiator, the bandwidth of the proposed antenna is broadened by adopting a gap in the endfire direction between two adjacent elements. By tuning the width of the gap, good impedance matching can be obtained with a VSWR 2:1 (S11< −10dB) impedance bandwidth of 380 MHz (15.8%), covering the band range of WLAN (2.40–2.48GHz). The measured gain in the require band is higher than 6.5 dBi. The proposed antenna shows the merits of simple structure and good impedance matching, which are important for practical applications.