Dual-Band High-Gain Differentially Fed Circular Patch Antenna Working in TM11 and TM12 Modes

A differentially fed circular patch antenna working in TM
₁₁
and TM
₁₂
modes is proposed for dual-band high-gain and stable radiation patterns. A set of shorting pins are loaded in circular contours underneath the circular patch to substantially increase the resonant frequency of TM
₁₁
mode, and the radiation gain in lower band can be hence effectively enhanced due to the enlarged patch size at resonance. Meanwhile, a narrow slot is introduced to the center of patch, in order to interrupt the out-of-phase current of TM
₁₂
mode on patch for sidelobe reduction. As the electric current distribution on patch is significantly reshaped by the slot, the antennas act like a full-wave dipole in this case, so both high gain and low sidelobe level are realized in upper band. Besides, by properly adjusting the shorting positions of pins and length of slot, the antenna can be well matched in the desired 3.6 and 5.9 GHz wireless local area network bands. Simulated and measured results show that at least 10 dBi realized gain can be obtained in both the lower and upper bands, and the patterns in the two bands show agreeable beamwidths.