A rhombic antenna array solution in eWLB package for millimeter-wave applications

A 77-GHz rhombic antenna as well as a rhombic antenna array designed for automotive radar applications are presented in 6×6mm2 and 12×8mm2 embedded wafer level ball grid array (eWLB) packages respectively. For the sake of antenna characterization, a 2×2mm2 monolithic microwave integrated circuit (MMIC) including a 77-GHz transceiver and a frequency multiplier is integrated in the package. The frequency multiplier generates the eighteenth harmonic of its input signal and scales a 4.25-GHz input signal to a 76.5-GHz output signal. This enables the antenna beam pattern characterization using a commercial signal source. As the dimensions of a single-element antenna in package (AiP) hardly exceeds the dimension of the MMIC, an AiP typically suffers from an asymmetric beam pattern and limited gain. This paper proposes a highly directional rhombic antenna array solution with more than 10 dBi gain and a symmetric beam pattern.