Design of A Low-Profile Compact Quad-Band Frequency Reconfigurable Antenna

A low-profile compact quad-band(4.81/6.21/8.09/11.44 GHz) frequency-reconfigurable antenna with multiple radiation patterns for wireless communications is proposed in this paper. The antenna basically consists of a patch radiator featuring rounded cuts, defected ground with meandered slot and shorting pins, resulting in four frequency bands with different radiation patterns. The antenna possesses a compact volume of $17 \mathrm{~mm} \times 17 \mathrm{~mm} \times 1.5 \mathrm{~mm}$ and exhibits omnidirectional radiations at 4.81/8.09/11.44 GHz and unidirectional radiation at 6.21 GHz. Four varactors on the ground plane are used to tune the lower and lower-middle frequencies. In addition, four additional parasitic patches with varactors are placed around the main radiating patch to tune the upper-middle frequency. The compact quad-band antenna can be potentially used in future wireless communication systems.