A novel compact dual-wideband BPF with multiple transmission zeros and super wide upper stopband

• Published in: International journal of electronics 2013-05, Vol.100 (5), p.718-726
• Main Authors: Mirzaee, Milad, Nosrati, Mehdi
• Format: Article
• Language: English
• Subjects: bandpass filter; Bandwidth; Bandwidths; Circuits; Design engineering; dual-wideband; Electric currents; Electronics; Impedance; L-shaped transmission line; Mathematical models; Resonators; wide stopband; Wideband
• ISSN: 0020-7217; 1362-3060
• DOI: 10.1080/00207217.2012.720949

In this article, a novel miniaturised dual-wideband bandpass filter (DWB-BPF) based on two different resonators including a quasi-spiral loaded multiple-mode resonator (QSL-MMR) and L-shaped transmission line (LS-TL) is presented. At the first step, in order to design a single wideband BPF filter with controllable transmission zeros near the centre frequency, the open circuit impedance parameter of quasi-spiral loaded resonator Z 21 is determined in terms of ABCD matrix. Then an equivalent circuit model of the proposed structure is derived and the impedance characteristic and electrical length of LS-TLs to achieve a DWB-BPF with excellent selectivity are calculated through even- and odd-mode analysis. The proposed filter possesses both compact and simple structure as well as two wide passbands with fractional bandwidth (FBW) of 70% and 22.8% for its first and second passbands, respectively. The proposed technique creates two transmission zeros at the lower and upper stopbands of each passband resulting in a very sharp roll-off accompanied by a wide stopband. Notably, the circuit size is reduced and the bandwidth is enhanced in comparison with its conventional counterparts. The theoretical performance of the filter is verified by the experimental one where a good agreement is reported between them.