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This article presents two types of dual-narrowband/ wideband filters using modified coaxial cavities with large frequency ratios. The dual-narrowband/ wideband filters mean two dual-band bandpass filters, one of which is a dual-band wideband filter, and the other is a dual-band narrowband filter. The proposed coaxial resonator in the dual-narrowband filter consists of a pair of disk-loaded coaxial stepped impedance resonator (DLCSIR), which provides a large frequency ratio. The frequency ratio of the first two resonant modes of the DLCSIR can be precisely controlled by adjusting the impedance ratios and dimensions of the loading disk. By contrast, the proposed coaxial resonator in the dual-wideband filter is a rectangular coaxial stepped impedance resonator (RCSIR), which has the merits of miniaturized size, large frequency ratio, and convenience for strong coupling. Finally, two second-order dual-narrowband/ wideband filters with large frequency ratios were designed, fabricated, and measured. The exhibited dual-passband performance of the two filters verifies the proposed concept.

In this paper, a novel dual-wideband balanced bandpass filter (BPF) based on branch-line structure is proposed. For analysis, the equivalent circuits of differential-mode (DM) and common-mode (CM) of the filter are built based on the even- and odd-mode method. With a proper synthesis design of DM bisection, dual passbands with a multi-order filtering response can be obtained. Additionally, three open-circuited stubs are centrally loaded on the CM bisection and six controllable transmission zeros are therefore generated. Thus, two stopbands are formed and then a favorable CM suppression within DM passbands is obtained. For demonstration, a third-order dual-wideband balanced BPF is designed with two passbands operating at 2.54 and 4.62 GHz. Good agreement between the simulated results and measured results is obtained, which verifies the validity of the proposed design method.

A novel triple-mode bandpass filter (BPF) using half-wavelength-resonator-coupled squareloop resonator is developed in this letter. The half wavelength resonator is applied to add an additional path, which increases a pole in the passband and a transmission zero in the stopband. Furthermore, the coupling scheme is used to accurately predict its desired performance. Compared to the conventional square-loop dual-mode filter, higher frequency selectivity and wider bandwidth are achieved. Finally, this filter is designed, fabricated and measured. Good agreement is achieved among the theoretical, simulated and measured results. All of these results validate our design idea. [ABSTRACT FROM AUTHOR]

An ultra compact microstrip wideband bandpass filter (BPF) using a quadmode stubloaded resonator is presented in this letter. The resonant characteristics of the quadmode resonator are explored by adopting odd- and even-mode analysis. The four resonant frequencies of this resonator can be controlled independently. For demonstration purpose, a wideband BPF is designed, fabricated and measured. The measured results are in good agreement with the full-wave simulation results. The realized wideband filter exhibits a 3 dB fractional bandwidth (FBW) of 45% with good in-band filtering performance and sharp out-of-band rejection skirt. [ABSTRACT FROM AUTHOR]

Background Several types of congenital lesions can cause complete or incomplete obstruction of the intestine. Our purpose is to present 3 neonates with dual intestinal type I atresia, i.e., simultaneous obstructive lesions at 2 locations in which the atresia manifested as diaphragmlike tissue. Case presentation All 3 cases were female infants ranging in age from 2 to 14 months. The common symptom in all cases was intermittent persistent vomiting. In some cases the vomitus was bilious, and other symptoms included abdominal distention and delayed meconium passage. Prior surgeries at another hospital were unsuccessful at relieving the symptoms in one case. One case had dual lesions in the colon, one dual lesions in the duodenum, and one atresia at both the distal portion of the ileum and the descending colon. Surgical exploration and removal of the lesions at our hospital was successful in all cases, and the infants were discharged in good condition. Conclusions Type I atresia can manifest as a diaphragm-like tissue obstructing the continuity of gastrointestinal tract, and in rare cases multiple areas may be present. Base on the intermittent nature of the associated symptoms, diagnosis can be difficult and is often delayed. Physicians should be aware of this condition during the work-up of an infant with persistent intermittent vomiting. [ABSTRACT FROM AUTHOR]