Abstract
A low-profile compact tri-band (2.45/3.5/5.8 GHz) reconfigurable antenna with versatile radiation modes is proposed for portable wireless communication in this communication. The characteristic mode analysis method is used to explain the antenna's operating principles and reduces the dimension. The antenna primarily comprises a patch radiator with T-shaped cuts, meander-slot defected ground, and shorting pins, resulting in three frequency bands with different radiation patterns. The antenna features a compact volume of 0.24\lambda _{0} \times 0.24\lambda _{0} \times 0.026\lambda _{0} ( \lambda _{0} is the free-space wavelength of 2.45 GHz) and exhibits omnidirectional radiations at 2.45 and 5.8 GHz and unidirectional radiations at 3.5 GHz. In addition, the operating bands can be tuned by applying different dc biases to the varactors. The antenna is fabricated, and the measured results agree reasonably well with the simulations. The miniaturized tri-band antenna can be potentially used in portable wireless services and intelligent transport devices.