Compact Wideband Folded Dipole Antenna With Multi-Resonant Modes

A compact and wideband folded dipole antenna with multi-resonant modes is presented in this paper. Three resonant modes are obtained by using a modified planar folded dipole and its coupled feeding structure. Incorporating with the shorting pins and parasitic patches, multiple resonant modes in the antenna are manipulated, shifted, and then combined for increasing the impedance bandwidth. Using this concept, a prototype of multi-mode folded dipole is designed, fabricated, and measured. The experimental results show that the proposed antenna achieves a bandwidth of 80% from 1.57 GHz to 3.68 GHz, while occupying a compact size of 0.3λ0×0.15λ0×0.05λ0 (λ0 is the wavelength in free space at the lowest operating frequency). Furthermore, a simple and effective design to achieve good omnidirectional radiation performance is developed by placing two proposed folded dipoles back to back. The antenna exhibits a flat gain variation of less than 1.27 dB over a broad bandwidth (82%) in the horizontal plane. Such a compact, wideband, planar antenna is a promising candidate for indoor signal coverage, wireless access points, and micro base stations in 2G/3G/4G/5G and WLAN/WiMAX wireless comminution systems.