This paper proposes a stacked metallization technique to improve the performance of millimeter-wave antennas in packages in terms of antenna gain and the behavior of the
beam pattern. A rhombic antenna and a 77-GHz SiGe transceiver were integrated in a 6 × 6 mm2 embedded wafer level ball grid array package. The surface of the package was stacked with a metallic layer except for a defined area above the antenna. The area is designed to have an unidirectional electromagnetic field distributions and acts as a secondary aperture antenna. The effective isotropic radiated power of the antenna in package with and without stacked metallization was measured over a wide frequency band from 72 GHz to 82 GHz. A comparison of the experimental results demonstrates a significant improvement in the behavior of the beam pattern as well as a 1.5 dB to 6.5 dB gain enhancement over a 10-GHz frequency band.