Design of Dual-Mode Arc-Shaped Dipole Arrays for Indoor Base-Station Applications

In this letter, two novel designs of dual-mode beam-steerable antenna arrays using arc-shaped dipoles are proposed for indoor base-station applications. To obtain the optimal distribution of excitations for each array, its gain and front-to-back ratio are optimized by using the method of maximum power transmission efficiency. The first design operates at 2.45 GHz and consists of a circular ring reflector and four arc-shaped dipoles, with the electrical length of one dipole arm being 1/4 wavelength. It can switch between omnidirectional mode and directional mode, and has 360° beam scanning capability in azimuth when operating in the directional mode. The realized omnidirectional gain of the first design is 1.5 dBi, and its peak gain and front-to-back ratio in the directional mode are 7.4 dBi and 15.5 dB, respectively. The second design also operates at 2.45 GHz, composed of two circular ring reflectors and eight arc-shaped dipoles distributed in two substrates, separated by a foam layer. Compared with the first design, it has a higher omnidirectional gain of 2.9 dBi and more uniform gain distribution in azimuth in the directional mode, with a peak gain of 8.4 dBi and a front-to-back ratio of 12.5 dB.