In this paper, the fabrication and testing of an integrated passive device (IPD) structure for X-band FMCW radar based on the fan-out wafer-level packaging (FOWLP) process are discussed. First, a transition line structure is added to the IPD structure to increase the upper impedance limit of the substrate, so as to reduce the process implementation difficulty and development cost. Second, the vertical soldered SubMiniature Push-On Micro (SMPM) interfaces testing method is proposed, reducing the testing difficulty of the dual-port structure with the antenna. Finally, the process fabrication as well as testing of the IPD structure are completed. The dimensions of the fabricated structure are 16.983 × 24.099 × 0.56 mm3. Test results show that, with a center frequency of 8.5 GHz, the actual operational bandwidth of the structure reaches 7.66% (8.095-8.74 GHz), with a maximum isolation of 33.9 dB. The bandwidth with isolation greater than 20 dB is 1.76% (8.455-8.605 GHz). The maximum gain at the center frequency is 2.02 dBi. Additionally, experimental uncertainty analysis is performed on different IPD structures, and the measurement results are basically consistent. These results validate the feasibility of the FOWLP process in the miniaturization of X-band FMCW radar antenna and other passive devices.
Keywords: antenna-in-package (AiP); fan-out wafer-level package; integrated passive device; through-mold via; ultra-thin.