Novel slotted stepped‐impedance resonator and its application to compact and high performance bandpass filter and diplexer design

By etching slots in the low‐impedance section of the conventional stepped‐impedance resonator, a novel slotted stepped‐impedance resonator (SSIR) is proposed. As two examples, a fourth‐order bandpass filter (BPF) operating at 1 GHz with a size of 0.078 λ g × 0.062 λ g and a miniaturized diplexer operating at 0.9/1.57 GHz with a size of 0.054 λ 0 × 0.086 λ 0 are designed based on the proposed SSIR. The fabricated BPF exhibits a high selectivity and a wide −30 dB rejection upper stopband from 1.13 f 0 to 6.52 f 0 , while the fabricated diplexer has up to −60 dB output isolation. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2013.