A Dual-Band Monopolar Patch Antenna Using Modified Ground Plane For 2.4/5.8-GHz WLAN

A low-profile dual-band monopolar patch antenna with vertically-polarized omnidirectional radiation is presented for 2.4/5.8 GHz wireless local area networks. It is composed of a square ring slot etched on a circular patch, four shorted vias, and a ground plane which are designed to excite TM
01
and TM
02
modes at 2.4 and 5.8 GHz bands, respectively. In order to broaden the lower band, the ground plane is modified by adding four stubs. The final design with overall size of π×(0.4λ)
²
×0.032λ at 2.4 GHz is fabricated and measured. The measurement results show that the antenna achieves impedance matching bandwidths (|S
11
| ≤ -8 dB) of 19.6% (2.3 − 2.8 GHz) and 15.4% (5.45 − 6.36 GHz). At two bands, the omnidirectional radiations are yielded with vertical polarization and uniform radiation at the azimuth plane. The peak realized gain of the low band and high band are about 4.0 dBi and 6.81 dBi, respectively.