A 94-GHz Dual-Polarized 1-D Series-Fed Phased Array Antenna With Low Sidelobe Level Based on Multilayer Coreless ABF Substrates

This article introduces a 94-GHz dual-polarized 1-D beamforming patch antenna array, specifically designed to achieve low sidelobe levels (SLLs) and an extensive scanning range. The array, in a $4\times 8$ configuration, is capable of 1-D expansion and utilizes Ajinomoto build-up film (ABF) substrates alongside a precision electroplating process. This combination ensures high accuracy and fulfills the miniaturization demands for 94-GHz operations. A notable achievement of this research is the design of a compact power divider using a coupling line with short end, which establishes a large power dividing ratio. This design is pivotal in maintaining consistently low SLLs, typically below −18.2 dB and often below −20 dB, over the $92\sim 96$ -GHz bandwidth within a $1\times 8$ linear array. In addition, the array’s transverse profile is optimized by altering the feeder angle, decreasing the distance between linear arrays to $0.52\lambda _{0}$ , where $\lambda _{0}$ denotes the free-space wavelength at 94 GHz. The proposed $4\times 8$ array design facilitates beam steering up to ±45° without grating lobes. The construction and experiments of the dual-polarized array antenna at 94.0 GHz validate its effectiveness, confirming the achievement of low SLL and extensive scanning capabilities in both polarizations.