An inverted FL antenna for dual-frequency operation

An inverted FL antenna (InvFLA) is analyzed to obtain dual-frequency operation at 2.45 and 5.2 GHz (wireless LAN system frequencies). The InvFLA is composed of inverted FL elements, a parasitic element, and a ground plate, where these lie in the same plane, i.e., the structure is a card-type structure having a co-planar ground plate. The antenna height above the ground plate is very small: 5.5 mm = 0.045 wavelength at 2.45 GHz. The analysis shows that the InvFLA has a 4.1 % bandwidth around 2.45 GHz and a 31.8% bandwidth around 5.2 GHz, both for a VSWR = 2 criterion. The gain is calculated to be 0.9 dBi at 2.45 GHz and 1.7 dBi at 5.2 GHz, with a small gain variation in each of the VSWR bands.