Evaluation of triple-layer EMWS for internal and external EMI shielding on paired 6-GHz LNA package modules

High-speed, highly sensitive devices are packaged in a shielded module against EMI. However, the highly reflective metals used to shield external incident EM power cause internal EMI through multiple reflections, and densely packed devices such as high-gain amplifiers and signal generators, as well as impedance mismatching in PCB design, radiate undesired EM power. In this study, the internal EMI was analyzed using in-situ measurements with paired 6 GHz-band 30 dB SiGe LNA modules incorporated in an ADC mold package. The measured S-parameter transmission coefficient, \((\rm{S_{21}})\), revealed an extraordinary phenomenon due to resonant oscillation caused by multiple reflections of the radiated EM power from the LNA output, and \((\rm{S_{21}})\) fluctuations caused by radiated EM power from another LNA. The resonant oscillation frequency depended on the mechanical dimensions of the ADC package and on the metal lid reflectivity. The resonant oscillation phenomenon was theoretically analyzed using equations for the signal power and phase changes through multiple reflection passes. The authors designed a triple-layer EMWS/M/EMWS sheet with EM wave shielding (EMWS) and metal, and experimentally confirmed its complete effectiveness in shielding both internal and external EMI.