Estimation of Noise Suppression in MSL With Co-Zr-Nb Film Considering Impedance Matching

An equivalent electrical circuit of a microstrip line (MSL) with a magnetic film was proposed. The estimation method of its circuit parameters was investigated in order to clarify a design guideline for noise suppression sheet (NSS) which was placed on the traces in electronic devices. First, the effect of the complex permeability of the magnetic film on the circuit parameters was investigated by magnetic circuit analysis of the cross section of the line. Second, an MSL with a Co-Zr-Nb film was designed as a test bench considering the impedance matching in the signal frequency range (below 1 GHz). Then, its transmission coefficients and the conducted noise suppression were estimated. The result shows that impedance matching was successfully maintained below 1 GHz. The estimated transmission coefficients and the conducted noise suppression almost agreed with the measured ones below the effective ferromagnetic resonance (FMR) frequency of the Co-Zr-Nb film. The results indicate that the proposed equivalent circuit has the potential to estimate circuit parameters and transmission characteristics of the MSL with the magnetic film at the circuit design stage. It is also useful to clarify the design guidelines for NSS placed on the traces in electronic devices.