Ultracompact Dual-Polarized Millimeter-Wave Active Phased Array With Enhanced Isolation and Wide-Angle Scanning Based on 3-D-Folded Radiator

This article presents an ultracompact dual-polarized millimeter-wave (mmWave) active phased array (APA) for terminal applications in the beyond fifth-/sixth-generation (5G/6G) era. A 3-D-folded radiator configuration is employed in the proposed design, achieving an aperture reduction of 37% compared to a conventional patch antenna. Besides, the in-band polarization isolation is enhanced through the introduction of a defected ground structure (DGS). Finally, ball grid array (BGA) packaging technology is adopted to replace bulky connectors, enabling direct and ultracompact integration between the antenna array and active beamforming circuits. This integration strategy reduces the maximum metal layers per board by 43% compared to conventional tile-type designs fabricated using monolithic multilayer PCB, and suppresses parallel-plate waveguide (PPW) mode interference. Experimental results demonstrate that the proposed antenna element can achieve an overlapped bandwidth of 25.5% (23.3–30.1 GHz). The developed APA exhibits a ±60◦ wide-angle beam scanning capability for both polarizations with gain variations below 2.6 dB, and obtains a peak effective isotropic radiated power (EIRP) of 34.7 dBm within the operating band. Error vector magnitude (EVM) below 4.2% is realized in wireless signal transmission experiments using 16/32/64-QAM 400-Mbaud modulated signals. The proposed APA demonstrates significant merits of ultracompact size, high integration, and wide-angle scanning capability, making it a promising candidate for mmWave terminal applications. © 2025 IEEE.