An omnidirectional dual band antenna system includes a radome and an antenna in the radome. The antenna has a linear array of lower frequency band driven elements, a linear array of higher frequency band driven elements and a linear array of parasitic elements, spaced in parallel planes with the array of higher frequency band driven elements in the middle. The parasitic elements couple to the higher frequency band driven elements and reshape the radiation pattern of the higher frequency band driven elements to correct for distortion caused by the lower frequency band driven elements.
A flat antenna includes a substrate, a first antenna module having a first grounding unit, a first radiating unit, a first feeding unit and a second radiating unit, and a second antenna module having a second grounding unit, a third radiating unit, a second feeding unit and a fourth radiating unit. The second antenna module is disposed abreast with the first antenna module. The first and the second grounding units, and the first and the third radiating units are disposed on a first surface of the substrate. The first and the second feeding units, and the second and the fourth radiating units are disposed on a second surface of the substrate. The first, the second, the third and the fourth radiating units, which have a first, a second, a third and a forth openings respectively, are electrically connected with the first grounding unit, the first feeding unit, the second grounding unit and the second feeding unit.
