A printed collinear antenna with a narrow (10 mm) width showing high-gain omnidirectional radiation is presented. The antenna comprises three half-wavelength elements of one strip dipole, one meandered line, and one straight strip connected in series, and has a total height of only 113.5 mm (about 92% wavelength of the frequency at 2442 MHz) for operation in the 2.4-GHz WLAN band. Due to the meandered line, in which the excited surface current has a phase opposite to that of the strip dipole and straight strip, the destructive radiation in the azimuthal plane for the antenna is suppressed. Conversely, the strip dipole and straight strip are constructive with regard to radiation, which leads to high-gain omnidirectional radiation for the antenna. A prototype showing good omnidirectional radiation (with gain variations less than 1.5 dB in the azimuthal plane) with a high gain level of about 4.4 dBi across the 2.4-GHz WLAN band is presented. (C) 2005 Wiley Periodicals. Inc.
