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Various publications address the suppression of the undesired mode coupling in laterally bounded conductor-backed coplanar waveguides (CPWs). In this paper, we present an integrated waveguide structure in which this coupling effect of different guided modes is deliberately exploited. Efficient forward coupling at arbitrary levels is achieved between a substrate integrated rectangular waveguide (SIW) and a CPW on its broad wall. Such hybrid integrated couplers combine the SIW's low-loss property with the CPW's flexibility and monolithic microwave integrated circuit compatibility. They are attractive for transitions, six-ports, antenna feeding networks, active antennas, and distributed phase shifters or amplifiers in millimeter-wave applications. The coupling mechanism is studied and a rapid design becomes feasible by use of the provided theory. Two couplers (a 3- and 0-dB version with 4.95- and 9.8-mm-long coupling sections) were designed and fabricated on alumina substrate for operation around 50 GHz. The 3-dB coupler achieves a wide relative bandwidth of 25% at 0.5-dB amplitude imbalance due to the asymmetric coupling structure, whereas the 0-dB coupler (transition) has a 7 % relative bandwidth at less than -0.2-dB coupling loss. Results obtained from millimeter-wave probe measurements on realized prototypes agree well with our theory and simulations. Index Terms--Coplanar wavegnides (CPWs), coupled-mode analysis, millimeter-wave couplers, substrate integrated circuits (SICs), substrate integrated waveguides (SIWs).

The solution‐phase synthesis is one of the most promising strategies for the preparation of well‐defined graphene nanoribbons (GNRs) in large scale. To prepare high quality, defect‐free GNRs, cycloaromatization reactions need to be very efficient, proceed without side reaction and mild enough to accommodate the presence of various functional groups. In this Minireview, we present the latest synthetic approaches for the synthesis of GNRs and related structures, including alkyne benzannulation, photochemical cyclodehydrohalogenation, Mallory and Pd‐ and Ni‐catalyzed reactions. [ABSTRACT FROM AUTHOR]

Novel nanographenes were prepared by a photochemical cyclodehydrochlorination (CDHC) reaction. Chlorinated precursors were irradiated in acetone in the presence of a base or in pure benzene and underwent multiple (up to four) regioselective cyclization reactions to provide rigid π-conjugated molecules. Pure compounds were recovered in good yields by simple filtration at the end of the reaction. The CDHC reaction showed compatibility with both electron-poor and electron-rich substrates, thus allowing the synthesis of pyridine- and thiophene-fused nanographenes. It also enabled the synthesis of sterically hindered contorted π-conjugated molecules without causing full aromatization. A kinetic study showed that the CDHC reaction under the conditions used is a very fast process, and some reactions are completed within minutes. The CDHC reaction thus shows great potential as an alternative to other reactions involving harsher conditions for the preparation of nanographenes. [ABSTRACT FROM AUTHOR]

In this paper, the development of an innovative micro-coaxial line technology is presented and developed for dc-to-millimeter-wave broadband applications. This nondispersive line is fabricated using a simple photoimageable thick-film process. Wave-guiding properties of the developed micro-coaxial line are extracted from 1 to 110 GHz, showing an extremely broadband operation. A single transition from micro-coaxial line to grounded coplanar waveguide is used to cover the entire frequency range available through single vector network analyzer. Passive devices are then demonstrated in the form of a 60 GHz band-pass filter and an 8 dB coupler using vertically coupled lines. Measured results of the demonstrative filter show an excellent agreement with simulated results, which present very good performances with 1.5 dB insertion loss over the frequency band of interest. The broadband coupler exhibits an exceptional multioctave bandwidth (from 20 to 82 GHz) and low loss at 1.5 dB. [ABSTRACT FROM PUBLISHER]

The solution-phase synthesis is one of the most promising strategies for the preparation of well-defined graphene nanoribbons (GNRs) in large scale. To prepare high quality, defect-free GNRs, cycloaromatization reactions need to be very efficient, proceed without side reaction and mild enough to accommodate the presence of various functional groups. In this Minireview, we present the latest synthetic approaches for the synthesis of GNRs and related structures, including alkyne benzannulation, photochemical cyclodehydrohalogenation, Mallory and Pd- and Ni-catalyzed reactions., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Graphene is a zero-gap, semiconducting 2D material that exhibits outstanding charge-transport properties. One way to open a band gap and make graphene useful as a semiconducting material is to confine the electron delocalization in one dimension through the preparation of graphene nanoribbons (GNR). Although several methods have been reported so far, solution-phase, bottom-up synthesis is the most promising in terms of structural precision and large-scale production. Herein, we report the synthesis of a well-defined, helically coiled GNR from a polychlorinated poly(m-phenylene) through a regioselective photochemical cyclodehydrochlorination (CDHC) reaction. The structure of the helical GNR was confirmed by 1 H NMR, FT-IR, XPS, TEM, and Raman spectroscopy. This Riemann surface-like GNR has a band gap of 2.15 eV and is highly emissive in the visible region, both in solution and the solid state., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)