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A three-dimensional frequency selective surface (3D-FSS) that provides stability for an angle of incidence and miniaturised unit cell size is presented. The proposed 3D-FSS is easy to fabricate and is implemented using via holes in a multilayer printed circuit board structure. Frequency transmission characteristics for different angles of both TE and TM polarisations are presented through simulations. The proposed structure was fabricated so as to verify the simulation results. The comparisons between the simulation and the measured results show good agreement. The results also show that the proposed 3D-FSS can provide better frequency stability for different incidence angles and polarisations as well as miniaturised unit cell size.

For the realization of bioassay with complex fluidic manipulation and logic operation on lab-on-a-disc platform, we present an active integrated centrifugal microfluidic chip based on the on-board control of wax valves within a multilayer complex chip. The multilayer hybrid structure including a microfluidic layer and a printing circuit board (PCB) layer utilizes the digital logic of electronic system to control the logic of liquid flow in microfluidic layer. The coupling mechanism between both layers is based on heat transfer, namely, the heating resistors in PCB layer are used to melt and open the paraffin wax valves in microfluidic layer. Without the limitation of surface tension-dependent valves, the application of active valve could be freely designed, which can largely extend the ability of integration on microfluidic chip. Many complex functional units including liquid sequential loading and switching of liquid flow are demonstrated. As an application, we also present a multilayer complex chip for plasmid DNA extraction based on our platform. In a word, our active centrifugal microfluidic platform provides a solution for the integration of complex bioassay on rotating disc, which has great potential in the applications of point-of-care diagnostics (POC).

Abstract—Prepregs for electrical purposes are used as an adhesive layer between individual layers in the production of multilayer printed circuit boards. They are materials obtained by impregnating fiberglass with a mixture of modified epoxy resins. The glass transition temperature (Tg) of the cured prepreg is determined by differential scanning calorimetry. This approach is universal, provides for wide boundaries of instrumental parameters, and does not contain numerical values of metrological characteristics. The paper presents a methodology for determining Tg taking into account the requirements of GOST and the conditions of the experiments and an assessment of its metrological characteristics. Cured samples of prepregs of Russian and foreign production were studied. Thermograms were recorded on two samples for each specimen, Tg was calculated based on the glass transition on the second heating curve at a rate of 20°C/min. It is shown that the relative total error of the method is ±4%. Since in some cases the visible glass transition was not recorded on the thermograms of cured prepregs, a linear approximation of the dependence of Tg on high heating rates was done, at which the glass transition is expressed noticeably better to the value of 20°C/min. The control of the correctness of the determination was carried out on samples for which it was possible to reliably determine Tg by the extrapolation and classical experimental-calculation method. It was established that both calculation methods lead to the same results within the limits of the analysis error. The results can be used in determining Tg of prepregs for electrical purposes and incoming inspection of the corresponding products.

This work is devoted to the research of new asymmetry effects in symmetric protective structures with triple modal reservation. We analyzed the structures with different cross-sectional locations of the reference conductor: in the center (unshielded structure), around (shielded structure), at the top and bottom (multilayer printed circuit board), and in the form of side polygons (double-sided printed circuit board). First, a preliminary quasi-static simulation was performed in the range of parameters. It was revealed that in all structures, except for the shielded one (in the form of a cable), the deviations of the output voltage amplitude, bandwidth, and frequency of the first resonance were insignificant, whereas in the shielded structure there were significant deviations in the time and frequency responses. The attenuation of the output voltage in relation to the input for each structure was also estimated. In addition, we performed a parametric optimization of the structures under consideration using a heuristic search, which made it possible to improve their characteristics. Finally, the switching order between the conductors in these structures with the original and optimized parameter sets was investigated in detail. The optimal conductor switching order in the case of a component failure was determined, and the best (according to protective characteristics) parameter configuration for each structure was found.

A composite right/left-handed (CRLH) transmission line (TL) based on a ridge substrate integrated waveguide (RSIW) is proposed and investigated. Its guided wave properties of backward-wave supporting are studied. This CRLH TL is realised by etching an interdigital capacitor on the ridge surface of the original RSIW. The CRLH TL is fabricated on a multilayer printed circuit board. Both the simulated and measured results are presented. Compared with other non-radiative CRLH waveguides proposed before, this RSIW-based CRLH TL has the advantages of miniaturised size, low profile, low cost etc. Besides, unlike other proposed planar CRLH TLs, this closed planar CRLH structure can keep the energy propagating inside so as to avoid energy leakage. Flexible designs can be developed based on this CRLH RSIW in guided-wave and radiated-wave applications.

The novelty of this work is laboratory formulation of environmentally friendly, water-based silver inks adapted for screen printing. The challenge was also to elaborate inks that can withstand temperatures as high as 900 °C. Indeed, when printed on ceramic substrate, they were sintered at these high temperatures. These inks can replace conductive silver pastes present in the market, today, and containing irritant solvents such as terpineol and other aromatic solvents. Besides, screen printing is considered as an additive technique, thus allowing reducing wastes. Furthermore, only with 72.5% silver, considered as low content compared to commercial inks (≥75%), prepared inks presented good electrical resistivity, 23 nΩ m, close to that of bulk silver resistivity, 16 nΩ m. Formulation of silver inks with spherical particles, 2–3 μm mean diameter, was performed. The aim of the study was to determine silver content effect on pastes rheological behaviour, lines properties (width, thickness and roughness) and electrical properties. Therefore, rheological behaviour of inks was studied; in particular, Casson and Bingham models were applied in order to determine the yield stress. Viscosity evolution as a function of shear rate was also determined. Besides, the thixotropic behaviour of inks was highlighted. Inks were then screen printed on alumina sintered substrates and cured at different temperatures during 15 min. Topography measurements were performed. Line resistivity as small as 35 nΩ m was measured on cured lines. These inks, printed on ceramic tapes, can be used to print microwave transmission lines, for which resistivities lower than 1 mΩ m are requested.

Numerical analysis and design of millimeter-wave (mmWave) slot-coupled microstrip 90° hybrid couplers employing circular ring patches, which is operating between 18 and 40 GHz frequency range for K-Band and Ka-Band radar applications, is presented in this paper. The proposed design uses multilayer printed circuit board (PCB) technology that allows having a compact and broad bandwidth coupler. The proposed couplers use broadside coupling between microstrip patches at the top and the bottom layers via an elliptical-shaped slot in the common ground plane (mid-layer). The design uses circular ring shaped broadside coupled patches and an elliptical-shaped slot created in a common ground plane between two identical dielectric substrates. The 3 dB coupler prototype has been fabricated on two 0.127 mm thick Rogers Duroid RT5880 substrates. The circuit occupies the dimensions of less than 5 mm × 5 mm without the extension that is required to insert the connectors. Extensive parametric studies are performed to address the effect of varying the coupler parameters on the coupling values, return losses, isolations, transmission magnitudes and phases through the operational frequency bandwidth. A 3 dB/90° hybrid coupler prototype is fabricated and then tested experimentally using Agilent E8364B PNA Network Analyzer. The simulation and experimental results show a good performance in terms of bandwidth, which covers the entire desired frequency range. In addition, detailed design for different coupling values of the proposed coupler is presented in this paper. The proposed coupler can achieve different coupling values range from 3 up to 9 dB that can be used for switched beam antenna array systems.

A new alternative of tailoring the dielectric characteristics of a BaTiO3-based ceramic is established in this study. The ceramic dielectrics were made by either two or three constituents having a composition of (Ba0.96Ca0.04)(Ti1.0−xZrxMn0.01)O3 (BCTZ), where x ranges from 0 to 0.22, and sintered with Ni inner electrodes at 1300°C for 4 h in a reducing atmosphere. Both alternative stacking, i.e., layer-by-layer of different compositions, and bulk stacking configurations were prepared by screen-printing, resulting in a composite dielectric of different characteristics. It is obtained that the Curie temperature (Tc) of the BCTZ ceramics decreases with an increase of Zr in the dielectrics, i.e., −8°C per mole of Zr. In addition, the stacking configuration, the proportion and the number of constituents in the composite materials control the dielectric characteristics of the multilayer ceramic capacitors. On the basis of the principles outlined, a multilayer ceramic dielectric having k-value in excess of 8000 with the X7R specification (−55 ∼ +125°C, ±15%), which consists of two BCTZ ceramics with Curie temperatures of −20 and 100°C, was successfully developed.