A Wideband MNG- TL Planar Microstrip Antenna for WLAN Applications

A novel wideband planar microstrip antenna with stable omnidirectional radiation characteristics is proposed. The antenna is composed of a series of sections of microstrip line distributed on top and bottom layers alternately. Periodical capacitive loading is realized by dividing the microstrip radiators into many disconnected strips with gradient length, which works as the artificial mu-negative (MNG) transmission line (TL). The MNG-TL has a unique property to support a zero propagation constant, thus resulting a more consistent current distribution on the TL. An Impedance bandwidth of 31.90% is achieved, and good horizontally omnidirectional radiation performance is realized while the realized gain of more than 3dBi is obtained in the whole wideband. Thus, the proposed antenna is good candidate for 5-GHz wireless local area network applications.