Broadside Couplings for High Selectivity Microstrip Filters

Abstract

This paper describes a number of broadside-coupled microstrip structures and their use for the implementation of high-selectivity multilayered filters. The broadside configuration allows for the introduction of cross couplings between nonadjacent resonators. The cross cou- plings can then be used to implement transmission zeros that can significantly increase the selectivity of the filters. Furthermore, the investigation shows that the amount of coupling can be considerably increased if the resonators are broadside coupled, thus easily allowing the implementation of broadband filters. Measured results are shown to agree with predictions, thereby fully Validating the new structures described.