Comparative Study of Feeding Techniques for 3-D Cavity Resonators at 60 GHz

In this paper, various topologies of feeding structures are comparatively evaluated for 60 GHz three dimensional (3D) integrated cavity resonators used in 3D integrated RF modules. Three excitation techniques (slot excitation with a shorting via, slot excitation with a λg/4 open stub, probe excitation) have been evaluated using simulated and measured data. The probe excitation is demonstrated as an attractive option for wideband applications due to its relatively wide bandwidth performance (~1.8%) and the strongest external coupling. The slot excitation with an open stub outperforms the other techniques, exhibiting the lowest insertion loss (~0.84 dB) for a 3dB bandwidth of about 1.5 % centered at 59.2 GHz and has the simplest fabrication. Index Terms –cavity resonators, system-on-package (SOP), low-temperature co-fired ceramic (LTCC), unloaded quality factor (Qu), millimeter-wave (mmW), three dimensional (3D) integration, slot excitation, probe excitation.