A reduced-size two-layer bandpass filter

In this paper, a new design for a reduced-size two-layer bandpass filter is introduced. This filter is built using four resonators placed in two stacked microstrip layers. In this structure, each layer contains two resonators, and the coupling between the resonators in the upper layer and those in the lower one is achieved via two rectangular slots etched in a common ground plane placed between the two layers. Using this design, the size of the proposed filter can be significantly reduced. A design is fabricated and the measured results are described. These measurements demonstrate excellent agreement with the computer-simulated predictions. (C) 2005 Wiley Periodicals, Inc.