Conduction noise attenuation by iron particles-rubber composites attached on microstrip line

Attenuation of conduction noise through microstrip line attached with high lossy iron flakes-rubber composites has been investigated in gigahertz frequencies. Microstrip line was designed with characteristic impedance of 50 /spl Omega/ and a length corresponding to the center frequency of 3 GHz. Iron flakes were fabricated by mechanical forging of spherical iron powders using an attrition mill. The fabricated microstrip line shows an ideal propagation characteristics of S/sub 11/=- 60 dB and S/sub 21/= 0 dB. Attaching a noise-absorbing sheet on the microstrip line, S/sub 11/ increases to about - 10 dB and S/sub 21/ decreases to -20-- 60 dB, depending on the size of the composite sheet. The calculated power loss is as high as 90% in the frequency range 2-8 GHz. Noise-absorbing characteristics was explained as a function of frequency, sheet size covering the transmission line, and material loss of the composite sheets.