Generation of a High-Gain Bidirectional Transmit-Reflect-Array Antenna With Asymmetric Beams Using Sparse-Array Method

A high-gain transmit-reflect-array (TRA) antenna with asymmetric bidirectional beams using sparse-array method is presented in this communication. The proposed element consists of three-layer hexagonal-ring-patch (HRP) structure, able to achieve both amplitude (0 or 1) and phase modulation. Based on this kind of element structure, a 125 mm \times \,\, 125 mm square-shaped TRA is designed and fabricated. A 45.3% of the radiation units operate in transmission mode while others in reflection mode. Spatially fed by a conical horn antenna, two well-defined beams are obtained on both sides of the TRA, pointing to the direction of \theta = 0^{\circ } and 170° ( \varphi =0^{\circ } ), respectively. The measured results show a maximum gain of 21.4 dBi with a 1 dB gain bandwidth of 6.7% for the transmitted beam, and a maximum gain of 24.4 dBi with a 1 dB gain bandwidth of 9.3% for the reflected beam. To the authors' best knowledge, it is the first time that the sparse-array method is employed in spatially fed antenna design. The proposed method can conveniently manipulate the pointing directions and beampattern characteristics of the bidirectional beams, providing a promising candidate for bidirectional wireless communication applications.