Design of two-layer six-pole bandpass filter for wireless applications

A new miniaturised microstrip six-pole bandpass filter using a multilayer configuration is proposed. This structure consists of six resonators placed on two stacked layers separated by a common ground plane. In this structure, the mixed coupling between the resonators on the upper layer and those on the lower one is obtained by introducing two identical slots on the common ground plane. To validate this approach, a six-pole bandpass filter prototype was designed, fabricated and measured.