Miniaturized bandpass filter using coupled stacked LC resonators in an organic build-up substrate

In this paper, very small stacked LC resonator structures in an organic build-up substrate and their coupling and excitation techniques are presented to design bandpass filters for 3.5 GHz WiMAX applications. Using multilayer stacked LC resonator structures can greatly reduce the required size of a bandpass filter. In addition, the structures can generate multiple transmission zeros to enhance rolloff rates or desired stopband attenuation for the designed bandpass filters. This paper also develops a simple technique of etching a rectangular C-shaped slot in the bottom ground plane to flexibly adjust the transmission-zero frequencies without changing the size and shape of the designed bandpass filters.