Artificial dielectric filter suitable for base-stations

An artificial dielectric is a material made artificially in which arranged metal strips work as molecules in a crystal. The artificial dielectric has characteristics which are not in usual dielectric, such as an extraordinary high dielectric constant and anisotropy. This characteristic was used and applied to bandpass filter. High dielectric constant is effective in filter miniaturization, and anisotropy contributes to spurious suppression. Although input and output direct-connected coupling is impossible for usual dielectric resonator, it is possible for artificial dielectric resonator comprising metal strips. Based on these results, experimental bandpass filters were designed and fabricated. The filters showed very good performances with small performance variation. Thus, it was confirmed that a small-sized filter with high selectivity is realizable using an artificial dielectric. Moreover, a possibility for drastic cost reduction of base-station filters can be expected by such a packaged production from a large-sized multilayer circuit board.