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As cellular mobile communication systems* markets are expanding worldwide, miniaturization for portable telephones are strongly required. Especially, the RF front end circuit components in the portable tele-phones are required to be much smaller. For this, miniaturization of microwave filters is one of the mean concerns. The coaxial filters have been mainly used, but the miniaturization becomes marginal. The multilayer planar filter, made of ceramics which has high permittivity permits shrinkage of the sizIn the experiment, the bandpass filter is designed using coupled stripline theory and J-inverter theory. And the designed structure is simulated using MDS (Microwave Design System) and IE3D. The filter consists of parallel-coupled striplines less than a quarter-wavelength and several coupling capacitors, and its structure is made up of several layers of Al2O3. A high performance, used for UHF band planar filter has been designed and fabricated in the experiment.
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