Analysis and Characterization of Castellated Holes as RF Interconnects for Modular Millimeter-Wave Devices

This paper presents an innovative approach to the use of Castellated Holes or Plated Half Holes (PHH) as transmission elements for high frequency interconnections between printed circuit boards in a frequency range of up to 40 GHz. The basic design was examined using commonly used design parameters for PCB modules with Castellated Holes which were then investigated and subsequently optimized to improve their RF performance, with a particular focus on design considerations according to today’s industrial manufacturing capabilities. Therefore the FEM-based full wave simulation technique was used to compare and optimize the design parameters in the aim to improve the capability of PHHs as low-loss, low-disturbant RF interconnection alternative in modular PCB designs. Based on these results test samples were developed, which were subsequently measured and thus verified the findings of the simulation. To provide a general comparability, this study focused on the S-Parameter to quantify the performance in terms of transmission losses and reflection. With an optimized design feasible results were achieved with a maximum transmission loss of less than 2 dB at the maximum of the desired frequency range and about 1dB at 20 GHz over the entire signal path. These insights make PHHs suitable for seamless integration into modular designs in RF and millimeter-wave applications.