Miniaturized bandpass filter with high selectivity and wide stopband using dual-layer structure

Summary form only given, as follows. A bandpass filter with high selectivity and wide stopband is proposed using the dual-layer scheme. The hybrid microstrip/DGS cell is introduced to obtain center resonance with two close transmission zeros. Based on the cells, an interdigital-coupled scheme is employed to achieve strong passband enhancement with high selectivity. To extend the stopband bandwidth, the defected microstrip structure is proposed. The filter operated at f0 of 2.6 GHz exhibits excellent selectivity (i.e., an attenuation slope with 420.9 dB/GHz and 484.9 dB/GHz in both passband edges) and wide stopband up to 3.75 f0.