Isolation optimization technique for 5G RF cavity

Electromagnetic cavity shielding in RF circuit design is a vital part of electromagnetic compatibility and signal integrity. For 4G frequencies this is relatively easy to achieve as the cavity size tends to be small compared to the wavelength. In 5G technology, where carrier frequencies are in very high frequencies (e.g. 20GHz to 70GHz), practical cavity dimensions are comparable to the wavelength and thus enable multiple cavity resonant modes. This causes challenges to achieve enough isolation between RF circuits and transmission lines. A typical approach to solve this issue would be using RF absorber material in the cavity to improve isolation between RF lines. This article describes a unique method to improve isolation between transmission lines inside a cavity for the 25.7 GHz carrier frequency with 700 MHz bandwidth. The proposed technique applies low cost T-shape screws instead of expensive absorber materials. Simulation model and results are presented here. New method shows that more than 50dB isolation improvement on limited bandwidth is possible.