An anisotropic metasurface that performs a reflectarray and transmitarray on each side is proposed. The proposed configuration comprises 15 × 15 unit cells that consist of polarization converters and a polarization filter. Two topologies are developed for the unit cells to meet five design goals simultaneously, including reflection magnitude, transmission magnitude, reflection phase difference, transmission phase difference, and polarization conversion ratio. By arranging the two topologies of unit cells according to a required phase distribution, in-phase reflection and transmission are achieved on each side. A prototype is designed, fabricated, and analyzed at 28.0 GHz. The feed is implemented as a quasi-Yagi antenna with gain of 8.0 dBi. When linearly-polarized electromagnetic waves impinge on the top, the proposed metasurface functions as a reflectarray and offers gain of 17.9 dBi. When the feed antenna illuminates the bottom, the proposed metasurface performs a transmitarray and depicts gain of 19.1 dBi. Moreover, when the both sides are arranged with feeds, a unidirectional pattern with power gain of 20.3 dBi is obtained. Such a "twin-feed mode" demonstrates a highly-directed main beam with orthogonal polarization components, which is useful in dual-polarized communications. Thus, the proposed metasurface provides antenna applications with low-cost, low-complexity, and multifunctional wavefront manipulation.INDEX TERMS Anisotropic, directive antennas, electromagnetic metamaterials, focusing, Yagi-Uda antennas.

A fully inkjet-printing technology is applied to antenna-in-package (AiP) and substrate integrated waveguide (SIW) to enhance the performance of three components, including via holes, wire bonding, and flexible antenna arrays. First of all, earlier studies utilize shorting pins for the conductive pathway in high-density AiP and SIW, but this requires an additional procedure to plate the conductor. We propose a mechanical approach to form a cylindrical hole, plating the surface with silver nanoparticles and realizing the equivalent circuit model of the shorting pin. The proposed approach does not require high alignment sensitivity or the precise control of laser power level. Second, fully inkjet-printed wire bonding is proposed for the system on the package. The proposed technique not only reduces the discontinuity but also enables a fabrication without additional assembly. Third, the proposed technique is implemented for antenna development, which shows desirable performance with reduced fabrication complexity. The proposed technology is validated by microstrip lines, SIWs, SIW cavity slots, and flexible 4 × 4 patch arrays fabricated on various substrates including RO 4003C, polyimide, and polyethylene naphthalate. For comparison purposes, conventional approaches using printed circuit boards are also implemented and tested. The results indicate the generality and capability of the proposed technique.

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