Compact omnidirectional dual-band dipole antenna with reduced ground plane effect

In this letter, a compact omnidirectional dual-band antenna is designed for wireless local area network applications. The proposed antenna is printed on the two sides of an FR4 substrate that the total dimension is 12 × 46 × 0.5 mm³. A dipole antenna is used to cover the lower operating band (2.45 GHz), while a capacitances-loaded patch generates a higher resonance (5.5 GHz). This antenna has a good impedance matching in the operation band, and the gain is 2.28 and 4.42 dBi in the lower and upper bands, respectively. To address the problem that the performance will drastically decline when the antenna is located on a ground, a quarter wavelength spiral line is employed to decrease the negative effect of the ground. Two proposed dipole antennas, placed on a horizontal ground as a MIMO antenna system, are analyzed with different configurations. The results reveal that the proposed method can effectively reduce the ground plane effect and improve the diversity performance, which has huge potential applications in MIMO system.