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In this paper, a broadband achromatic focusing metasurface design scheme based on the equivalent circuit theory and optimized by a deep learning method is proposed. The designed metasurface element consists of multilayer metal rings and a grounding layer, and the phase modulation effect of achromatic aberration in a wide frequency range is realized by precisely controlling the distance between the layers. The preparation of this complex structure is realized by using additive manufacturing technology, which effectively overcomes the limitations of traditional printed circuit board technology in manufacturing complex structures. To further improve the design efficiency, deep conditional generative adversarial network is introduced in this paper to quickly determine the structural parameters and realize the inverse design, which significantly improves the efficiency and accuracy of the metasurface structure design. The experimental results show that the metasurface possesses good focusing performance in the 17 to 35 GHz band with an effective bandwidth utilization of 69.2 %. The design method proposed in this study combines artificial intelligence and additive manufacturing technology, which provides new design ideas for applications in the fields of communication, optics and wireless energy transmission. 

This letter proposes an angle-multiplexed multifocal method for designing a 2-D beam-scanning transmitarray (TA). The angle-multiplexed method is commonly used to generate orbital angular momentum (OAM) multiplexing. The multifocal phase distribution is calculated using the angle-multiplexed and bifocal methods to achieve higher gain enhancement and 2-D beam-scanning with a low scan loss without optimization. The additive manufacturing technology is used to fabricate a 3-D transmission line component. In the terahertz band, the transmitting and receiving (Tx-Rx) unit cell impedance matching can be affected by the Pancharatnam–Berry (P-B) method, and a 3-D coaxial line is introduced to tackle this problem. For proof of concept, the prototype was fabricated. Feeded by a WR-06 waveguide probe, the proposed TA achieves a gain enhancement of 16.3 dB and ±30° 2-D beam-scanning, simulated and measured 3 dB gain bandwidths of 19.6% and 16.3%, and the measured axial ratio bandwidth of 30.7%.