GENERALIZED DUAL-PLANE MULTICOUPLED LINE FILTERS

This paper describes the general realization of elliptic function narr ow-bandpass filters constructed from two adjacent planes of microstrip quasi-TEM line resonators. This dual-plane configuration allows nonad jacent coupling to be realized through small slots between the planes. Alternate sign coupling is realized by the appropriate positioning of the slot along the resonator length. A model developed from Bethe's s mall-hole coupling theory is used to predict these couplings. Adjacent resonator couplings are modeled using a coupled-line analysis modifie d to characterize the coupling of an inhomogeneous medium. The filter synthesis technique previously developed for waveguide cavity filters can be directly applied in designing a dual-plane filter.