A 79-GHz LTCC patch array antenna using a low-loss ceramic tape

This paper presents a 79-GHz microstrip patch array antenna in a low-temperature co-fired ceramics technology. The ceramic tape used has a low loss tangent (0.0013 at 79 GHz), a good shrinkage-control (with zero-shrinkage process), and it also enables a photolithographic process for the outside layers of metallization. To verify the performance of this material system for applications at 79 GHz, an array antenna was designed with a simulated radiation efficiency of 81% (at the antenna feedingpoint). A hybrid feeding-network was chosen for the antenna. On the top layer the microstrip patch antennas were used as the radiating elements (with two layers of ceramic tapes as the substrate). They were connected by the microstrip lines (seriesfeed). A via guard-ring helps to suppress parasitic surface waves due to the thick substrate. A vertically oriented power divider (parallel-feed) keeps the main-beam direction constant in a given frequency bandwidth. The simulated and the measured halfpower beamwidths are 9° and 7° in the E-plane and H-plane, respectively. The measured bandwidth of 10-dB return loss is around 4 GHz. The measured antenna gain (at WR12-flange) is 15.4 dBi. This antenna has a geometry of 28mm×3.2mm00D71.2mm and is suitable for 79GHz middle/short range radar applications.