A Novel Desensitization Using Resonance Suppressors in Metallic Shielding

Metallic shielding provides a strong coupling path for digital lines to analog traces at resonance, which induces coupling noise in analog components, and thus deteriorates the RF performance. This paper proposes a novel mitigation design that uses a spiral-shaped slot resonator as a resonance suppressor structure inside the metallic shielding. Compared with the conventional solution using a ferrite-based absorbing material, the proposed method not only features cost efficiency and design flexibility, but also provides a high level of suppression at the desired frequency band. Resonant modes are reduced if the surface current distribution of the metallic shielding is perturbed by the suppressor. This study uses half-wavelength slot resonators and miniaturization techniques, so the current is trapped by the suppressor at its resonant frequency, thereby resulting in a weaker resonant mode. The results of simulation and measurement show that coupling noise is reduced by 10 dB with a size of one-tenth wavelength only.