Off-band characteristics of small isolator for portable phones

The off-band attenuation characteristics of lumped element isolators for portable phones has been studied using the developed circuit simulator. The introduction of new parameters, circular-polarization occupation ratio /spl phi/ and ferrite filling factors /spl eta//sub r/, /spl eta//sub t/ along radius and thickness of garnet respectively, enabled us to realize the actual off-band characteristics by simulation. The second peak of attenuation near at 1.5f/sub 0/ reflects the residual inductance L/sub d/ due to /spl phi/ and /spl eta//sub r/. It has become evident that the attenuation pole near at 2f/sub 0/ corresponds to the ferromagnetic resonant frequency.