Concave lens for 2.4 GHz coaxial collinear antenna

The pattern for a COCO (coaxial collinear) antenna is omni-directional in the H-plane. In this paper, a special concave lens at 2.45 GHz is designed to improve the directivity of wire antenna in the H-plane. The lens was implemented and measured by the planar near field system at Da Yeh University. The error of the index of refraction for the designed lens by both simulation and measurement is within 1%. The quadratic phase error on the aperture of the lens in the H-plane is improved from 58.5/spl deg/ to 10.5/spl deg/. The test results are quite in agreement with that of simulation.