Hybrid of monopole and dipole antennas for concurrent 2.4- and 5-GHz WLAN access point

A novel hybrid of a 2.4-GHz monopole antenna and a 5-GHz dipole antenna is presented to provide concurrent 2.4 and 5 GHz band operation for access-point applications. The two antennas are arranged in a collinear structure and printed on a compact dielectric substrate with dimensions 12 mm times 60 mm. The monopole antenna has a meandered radiating strip and is short-circuited to a small ground plane through a shorting strip. The dipole antenna includes two sub-dipoles at the opposite side of a narrow ground plane and fed by a simple T-junction microstrip-line network. The two antennas are closely set with a distance of 1 mm only, yet good port isolation (S₂₁) well below - 20 dB can be obtained. With a low profile, the proposed design can easily fit into the casing of some standard access points and allow the 2.4 and 5 GHz band signals to be simultaneously received or transmitted with no external diplexer required. Good omnidirectional radiation has been observed too.