Analysis of optimum sheet resistance for integrated electromagnetic noise suppressors

This paper discusses the physical nature of the optimum sheet resistance of noise suppression sheets/films based on three-dimensional (3-D) finite-element method (FEM) electromagnetic field simulation. Co-Al-O films with sheet resistance of 10^-1 — 10⁵Ω/square were deposited on top of a micro strip-line. It was revealed that inline loss generation was maximized with the film's sheet resistance of nominally 100 Ω/square, which explains well the earlier experimental results. The ratio of loss generation to the input power reached 0.96 in the experimental results and 0.97 in the simulation results at 6 GHz. A certain balance of eddy current generation and a material resistivity allowed the Co-Al-O film to dissipate the inline noise power effectively. The simulation results also showed that the inline power was not radiated from the Co-Al-O film but was lost in the film. Ferromagnetic resonance losses were found around 1–2 GHz combined with the eddy current losses. These two electric and magnetic losses enhanced total inline loss generation effectively.