Wideband and wide stopband superconducting bandpass filter using asymmetric stepped‐impedance resonators connected to open stub

Abstract

A wideband wide stopband filter is designed using asymmetric stepped‐impedance resonators (ASIRs) connected to a large open stub. The capacitive open stub and the parallel‐coupled microstrip line are used to achieve the strong couplings for large fractional bandwidth (FBW). For a wide‐stopband performance, the proposed filter uses ASIRs to improve the high‐order spurious resonant frequency. The first and last resonators of the proposed filter are further optimized to suppress the spurious resonant frequency caused by open stub. The final filter has a 70% FBW centered at 4.87 GHz with 20‐dB‐rejection stopband up to 15.78 GHz (approximately 3.24 f0). The measured insertion loss is less than 0.15 dB and the return loss is better than 17 dB.

Multi‐spurious harmonics suppression in folded hairpin line bandpass filter by meander spur‐line

“…In Table 2, the parameters are f 0 = center frequency (GHz), FBW = Fractional bandwidth (%), IL = Insertion loss (dB), RL = Return loss (dB), SRL = Stopband rejection level (dB), SBW = Stopband bandwidth (GHz), and size in terms of λ g λ g . It has been noted that there has been an improvement in the stopband rejection level for the proposed filters than 5‐7,12‐15,18 . Moreover, an improvement of stopband rejection bandwidth has been obtained for this work compared to References 6,10,12‐14,18.…”

“…However, most of the studies in References 5‐11 have been performed for conventional hairpin‐line filters, acquiring large circuit areas, and hence, their applications become restricted in modern wireless communication systems where compact‐sized filters are essential. Very recently, compact wideband bandpass filters with high selectivity and wide stopband have been proposed in References 12‐15. In Reference 12, a microstrip‐slotline bandpass filter has been designed by cascading two back‐to‐back microstrip‐to‐microstrip vertical transitions and a rejection level of 20.63 dB up to 3.86 f 0 has been reported.…”

“…Accordingly, a wide rejection level of more than 30 dB up to 2.49 f 0 has been obtained. Later, asymmetric stepped impedance resonators cascaded to a large open stub have been incorporated in Reference 14 to design a wideband bandpass filter with 70% FBW and centered at 4.87 GHz, exhibiting 20 dB rejection stopband up to 3.24 f 0 . However, in the modern era, compact narrowband filters with wide stopband and improved skirt characteristics are in great demand.…”

A q uasi‐analytic synthesis methodology for spiral defected microstrip compact bandstop filters

“…Then, optimizations are used to finalize the size and geometry. [22][23][24] In this paper, a relevant design method is investigated to present an efficient analytical well-established design process for spiral DMSs which are extensively used as compact Butterworth bandstop filters. The conventional design processes of spiral DMSs are complicated with many effective variables and are not easily applicable.…”

“…Eventually, the final configuration with specific geometry and response is obtained. Then, optimizations are used to finalize the size and geometry 22‐24 …”