EMI reduction from airflow aperture arrays using dual-perforated screens and loss

Airflow perforations in shielding enclosures can act as apertures facilitat ing the coupling from internal sources to external electromagnetic interfer ence (EMI), This EMI radiation for single- and dual-screen configurations w as studied herein experimentally and with finite-difference time-domain (FD TD) modeling. A general EMI reduction of more than 20 dB was achieved for d ual-perforated screens spaced 1 cm apart when compared to EMI for a single perforated screen. However, in the dual-screen case, the space between the screens can act as a thin cavity, which, in turn, can lead to significant r adiation at distinct angles. Damping the resonances by loading the space be tween the screens with lossy material mitigates this problem and achieves m ore than 20-dB reduction over a single screen.