High-Gain Omnidirectional Transmitarray Antenna

A new omnidirectional transmitarray antenna (TA) is proposed to realize the high gain and high omnidirectionality for millimeter-wave (mmW) applications. The antenna consists of a feeding probe as the source of the TA and an annular receiving/transmitting (Re/Tr) array surrounding the probe. The Re/Tr unit cell is composed of a pair of back-to-back angled dipoles and a delay line. The unit cell utilizes the rotation freedom of the direction of the Tr unit for a 0°/180° phase shift (1 bit), and an additional delay line between the Re and Tr cells for a continuous phase shift between 180°. Then, 1 bit+ Re/Tr unit cells with a continuous phase shift between 0° and 360° are built to form an omnidirectional array. By tuning the phase distribution of the longitudinal cells, the array can compress a wide conical omnidirectional beam from the probe radiator into a high-gain narrow omnidirectional beam in the azimuth plane. Measurement results show that the operating bandwidth of the antenna is 14.2% (from 26.1 to 30.1 GHz), within which the antenna can achieve a high gain of around 8.0 dBi and a stable omnidirectional beam. The design that transplants the concept of TA into a high-gain omnidirectional antenna is proposed for the first time. The proposed omnidirectional TA shows the advantages of remarkable omnidirectionality, broad bandwidth, and low cross-polarization level.