Sub-THz Polarization-Dependent Beam-Steerable Metasurface Antenna-in-Package for 6G Communication Constructed Using an LTCC Process

In this paper, a polarization-dependent beam-steerable metasurface lens that is integrated with an antenna-in-package (AiP) using a single low-temperature co-fired ceramic (LTCC) process is proposed for sub-terahertz applications. The novelty of this work lies in the codesign of a voltage-controlled oscillator, a stacked patch antenna, and a reactive impedance surface within a compact AiP configuration, all fabricated through a single LTCC process. This integrated design not only simplifies fabrication and reduces interconnect loss but also compensates for bonding-induced mismatches. To overcome the high propagation loss in the W-band, a polarization-sensitive metasurface lens is employed, enabling significant gain enhancement and beam steering based on the antenna’s polarization. Notably, the three types of three- and five-layered unit cells used in this study feature a grid or cross-dipole slot positioned between the single/stacked patch on each outer side. In contrast to the conventional three-metal-layered process that allows for 180° phase coverage to ensure identical thickness, the proposed unit cell achieves full 360° phase coverage with a transmission loss of less than 3 dB. The measured peak gain of the 100 GHz AiP with a baseboard is 8.86 dBi. For the AiP with the metasurface lens, the beams in the boresight, +30°, and +40° directions at 100 GHz under x-axis polarization exhibit peak gains of 17.8, 16.2, and 16.0 dBi, respectively. For y-axis polarization, the beam in the boresight, -30°, and 20° directions achieve peak gains of 17.7, 16.6, and 16.5 dBi, respectively. Overall, the proposed scheme demonstrates promising beam steering for both types of polarization with a single fabrication process for W-band systems.