Dimensional effects of the magnetic film on coplanar transmission line for RF noise suppression

We fabricated the radio frequency (RF) integrated noise suppressor by integration of the various dimensions of the CoNbZr magnetic film on the coplanar transmission line using the microlithography process. The RF noise suppressor was composed of a magnetic film (CoNbZr)/polyimide/Cu transmission line/seed layer (Ti/Cu)/glass substrate. The CoNbZr magnetic films (4πMs: ∼10 kG, H_k: 8.5 Oe, ρ: 120 μΩ cm, freq._FMR: 0.8 GHz) are deposited by RF sputtering. The signal attenuation on the transmission line was estimated by the S-parameters (S₁₁,S₂₁) up to 20 GHz. In case of the 2000-μm-wide, 15-mm-long, and 2-μm-thick magnetic film, the magnitude of the signal attenuation at resonance (dip) point was increased by about -56 dB than that of the coplanar transmission line without the magnetic film. By decreasing the width of the magnetic film from 2000 to 200 μm, the magnitudes of the signal attenuation were similar to each other. However, in the case of the 50-μm-wide magnetic film, the signal was attenuated only a little. These results are deeply related with the width of signal line (50 μm). The eddy current loss was increased as the magnetic film became longer. This implies that signal attenuation over resonance frequency depends on the volume of the magnetic film due to the eddy current loss.