The Anglet: An E/H-plane Bent, 90-Degree Twisted, TE101/TM110-Mode Singlet Building Block

In this work, a subclass of the singlet building block is defined. Termed the anglet, a waveguide cavity-based structure is demonstrated that combines a bend, a 90-degree polarization rotation, and produces one pole and one transmission zero. The anglet is defined due to its unique ability to be viewed as either a TE101-mode singlet or a TM110-mode singlet based on the users coordinate point of view together with the requirements for the bend direction and polarization rotation. Two types of anglets are demonstrated by simulation and a third-order filter is demonstrated for the incorporation of an anglet in a practical design. Emphasis on its unique capabilities are highlighted due to its nature as a fundamental-mode resonator with evanescent bypass coupling. Furthermore, an accurate approximation for the source-load coupling is described and a prototype filter is fabricated and measured in order to validate the concept

W‐band TE102‐mode filter with doubly loaded E‐plane and H‐plane irises

In this correspondence, high-precision computer numerical control milling is utilised to demonstrate a doubly loaded iris, cross-coupled waveguide bandpass filter for inline operation within the W-band. This sixth-order filter is designed in a stacked H-plane configuration and utilises both E-plane and H-plane doubly loaded irises to maintain the flow of a TE102-mode electromagnetic field. In this configuration, a high rejection level is maintained outside of the passband while a good unloaded quality factor is obtained through the support of larger resonator dimensions. The filter is designed for approximately 2% fractional bandwidth centred at 97.5 GHz and has been fabricated as three brass components. Measurements of the filter agree very well with the simulated results and demonstrate a spurious-free design over the full W-band

Widely Tunable TM-Mode Dielectric Filters With Constant Absolute Bandwidth Using Re-Entrant Caps

This paper reports octave tunable dielectric combline bandpass filters with constant absolute bandwidth (CABW) using a novel re-entrant cap tuning technique. The resonant frequency is tuned by the hollow re-entrant cap penetrating into the filter cavity as an envelope around the dielectric resonator. This mechanism of tuning provides wider tuning capabilities and better spurious performance than the conventional screw-based tuning. Also, the cap tuners can be employed effectively to tune the input-output and inter-resonator couplings simultaneously with the frequency reconfiguration, enabling a CABW over a wide frequency tuning window. For proof of concept purposes, a single widely tunable resonator is presented with octave tuning ratio of 2.64:1, high quality factor from 1705 to 5480, and spurious-free band up to 3.44⋅ f0 . Afterwards, two octave tunable re-entrant cap filters are designed, fabricated, and tested. The first filter is a 78% widely tunable two-pole filter with a CABW of 43.5 ± 12% MHz, low insertion loss equals to 0.28 ± 0.03 dB, and a compact volume of 39 cm 3 . The second design is a four-pole octave tunable bandpass filter from 2.96 GHz to 1.36 GHz with a constant 69 ± 13% MHz bandwidth, low insertion loss better than 0.6 dB, return loss higher than 16 dB, and a compact 62 cm 3 structure. According to our own knowledge, thanks to the proposed tuning mechanism, the presented designs are the first CABW octave tunable high Q waveguide-based filters, having the widest tuning ranges over all similar state-of-the-art-designs

Miniaturized Dual-Band Dual-Mode TM-Mode Dielectric Filter in Planar Configuration

This paper reports a new class of compact inline dual-band bandpass filters using TM-mode dielectric resonators in planar configuration. Thanks to the employment of the dielectric-loaded TM-mode waveguide configuration and the dual-mode TM120 and TM210 resonances, substantial size miniaturization and volume saving (>70%) can be obtained in comparison with conventional waveguide technology. Additionally, the planar topology of the presented concept offers highly desirable advantages for industry and mass production including the ease of manufacturing, assembly, and tuning. Furthermore, the resonating doublets and the nonresonating TM110 mode are effectively utilized to introduce and control both inter-band and outer-band transmission zeros, advantageously increasing the isolation between the two passbands and enhancing the outer-band rejection regions. The general design procedure of the proposed filter is discussed in detail. A three-pole C-band dual-band dual-mode TM-mode dielectric filter is designed, implemented, and measured to validate the proposed configuration

Very Compact Diplexer Based on Dual-Mode Dielectric TM-Mode Resonators

A very compact in-line C-band diplexer is reported in this letter based on dual-mode dielectric TM-mode resonators in planar coupling configuration. In addition to the advantages of substantial volume-saving and easy assembly, the proposed diplexer features high-quality factor, enhanced spurious performance, high-power handling, and efficient tuning process with independent control of each passband. For verification purposes, a C-band diplexer is designed, implemented, and tested. The final assembled diplexer unit has a compact overall volume of 43 × 40 × 15.9 mm 3 . It operates at 4.73 and 5.03 GHz with the same bandwidth of 24 MHz, an insertion loss better than 0.9 dB, and a return loss higher than 21 dB. In addition, a high-power breakdown analysis shows that the introduced diplexer can handle high levels of input power up to 5200 W

Improved TM Dual-Mode Filters With Reduced Fabrication Complexity

This work presents an alternate and improved approach for the design of dual-mode filters that utilize transverse magnetic (TM) and nonresonating modes. The method that is proposed in this work allows for an improvement of the typical TM dual-mode filter design through the reformation of the coupling irises that connect the TM dual-mode cavity to the source/load waveguide ports, where the new interconnection means takes the form of resonate slot-irises. In this manner, a fourth-order quasi-elliptic response can be achieved within a very limited physical geometry and able to cover more than double the usable fractional bandwidth than previously reported. Furthermore, the selectivity and insertion loss of the filter response is significantly improved when compared to the typical single-cavity TM dual-mode filter response that uses coupling irises, while on the comparison of equal-order structures, a reduction in fabrication complexity and improved insertion loss is achieved. A characterization of the dimensional variations and effects of altering one of the source/load port positions in the proposed filter design is investigated in order to demonstrate notable effects on the rejection characteristics and positions of transmission zeros. A presentation on the design theory is given and formulations of various filter responses are examined. The fabrication of an experimental prototype with approximately 7.3% fractional bandwidth (FBW), centered at 90 GHz is conducted using high-precision computer numerical control (CNC) milling in order to demonstrate that the unique simplicity and overall compaction of this method can be easily applied at millimetre-wave frequencies without the need of tuning means. The results which are presented demonstrate highly accurate measurements throughout the W-band range, while an additional Q-factor analysis is provided in order to compare the improved filter scheme with other known design methodologies

Structured-Glass Waveguide Technology for High-Performance Millimetre-Wave Components and Systems

This work presents a novel waveguide medium based on laser-induced structured-glass for the design of high-end millimetre-wave components and systems. The material properties, fabrication process and functional attributes of the structured-glass technology are first described and then applied in order to demonstrate a fourth-order bandpass filter prototype operating within the W-band frequency range, centered around 88 GHz with a narrow fractional bandwidth of 2.3%. The basic filter design, dimensional considerations, and assembly process are discussed in order to outline the fabrication process. The prototype filter, along with its associated feed-line transitions and split-block interface are measured and characterized in the laboratory in order to validate the design approach. The measured response is shown to be exceptionally accurate; the insertion loss is found to be approximately 1.43 dB - 1.97 dB throughout the measured passband with a return loss of better than 22 dB and center-frequency offset of approximately 0.117%. A comparison to existing technologies is discussed in order to highlight the advantages of the proposed medium and to contrast the differences in both manufacture and achievable results for high-end components

Design of Compact Quasi-Elliptic Bandpass Filters Based on Coaxial Inset Resonators

This article reports a novel inset resonator configuration for coaxial filter applications with quasi-elliptic responses. The design and analysis of the inset resonator are discussed in detail and accurately modeled as a capacitively-loaded stepped-impedance half-wavelength resonator featuring more compactness, high quality factor, and enhanced spurious responses in comparison with conventional half-wavelength and combline resonators. Additionally, the operating frequency can be tuned intrinsically through the displacement of the coaxial resonator, eliminating the need for any additional tuning elements and maintaining a stable quality factor. Two quasi-elliptic inset resonator type filters are implemented in planar and longitudinal coupling configurations, respectively. The first takes the form of a folded four-pole 2.93 GHz filter with two symmetrical transmission zeros. The fabricated filter has a compact structure of 29.76 cm3, an insertion loss better than 0.73 dB, a return loss better than 18 dB, and a wide spurious-free band up to 3.5⋅f0 . The second inset-type quasi-elliptic filter is realized in a longitudinal inline arrangement. An example of a 2.53 GHz three-pole filter is presented with a closely-positioned transmission zero, wide spurious-free band ( ≈3⋅f0), and a very compact structure of 55.7×33×33 mm3

Highly Selective Broadband mm-Wave Diplexer Design

This letter presents a novel broadband diplexer design that is capable of achieving highly stringent rejection characteristics though the use of singlets whose interconnecting irises are formulated as resonant slot-irises. The combination of these two resonant-cavity types allows for a unique filtering solution with increased filter order, wide available bandwidth, low geometric complexity and simple milling requirements which can be suitably applied to millimetre-wave and submillimetre-wave applications. A prototype is fabricated for operation in the Wband (75 GHz - 110 GHz) in order to cover a 10% fractional bandwidth in each passband. Measurement of the prototype denotes highly accurate results and exemplifies the use of all resonator and coupling elements in order to support ten poles and four transmission zeros in an elegant diplexer solution

Quantification of Microbial Communities in Subsurface Marine Sediments of the Black Sea and off Namibia

Organic-rich subsurface marine sediments were taken by gravity coring up to a depth of 10 m below seafloor at six stations from the anoxic Black Sea and the Benguela upwelling system off Namibia during the research cruises Meteor 72-5 and 76-1, respectively. The quantitative microbial community composition at various sediment depths was analyzed using total cell counting, catalyzed reporter deposition – fluorescence in situ hybridization (CARD–FISH) and quantitative real-time PCR (Q-PCR). Total cell counts decreased with depths from 109 to 1010 cells/mL at the sediment surface to 107–109 cells/mL below one meter depth. Based on CARD–FISH and Q-PCR analyses overall similar proportions of Bacteria and Archaea were found. The down-core distribution of prokaryotic and eukaryotic small subunit ribosomal RNA genes (16S and 18S rRNA) as well as functional genes involved in different biogeochemical processes was quantified using Q-PCR. Crenarchaeota and the bacterial candidate division JS-1 as well as the classes Anaerolineae and Caldilineae of the phylum Chloroflexi were highly abundant. Less abundant but detectable in most of the samples were Eukarya as well as the metal and sulfate-reducing Geobacteraceae (only in the Benguela upwelling influenced sediments). The functional genes cbbL, encoding for the large subunit of RuBisCO, the genes dsrA and aprA, indicative of sulfate-reducers as well as the mcrA gene of methanogens were detected in the Benguela upwelling and Black Sea sediments. Overall, the high organic carbon content of the sediments goes along with high cell counts and high gene copy numbers, as well as an equal abundance of Bacteria and Archaea