A V-shaped structure for improving the directional properties of the loop antenna

A V-shaped wire-loop antenna with a butterfly-like structure is proposed in this paper. The antenna consists of two identical half-loops inclined at an angle to each other and joined together at the feed point and the point at which they meet the ground plane. The performance of the structure was evaluated analytically for included angles 90°, 120° and 150° between the half-loops. At a frequency at which the lengths of the half-loops making up the antenna are equal to a wavelength, the radiation characteristics were superior to that of a conventional half-loop. The results were verified through measurements for the case where the included angle was 120°. The dominant radiation was in the direction perpendicular to the ground plane and the gain was better by 4.5 dB. The measured 3-dB beamwidth was also narrower, at 60°, compared to 135° in the case of the conventional half-loop.