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Toughened glass insulators installed in overhead lines play a key role in maintaining the reliability and safety of power systems. The singular properties of toughened glass make this material particularly suitable for this application on account of its excellent dielectric properties, high mechanical strength and easiness of inspection. If the glass was damaged, it would shatter completely leaving the remaining part of the insulator, called stub, still providing mechanical connection and being easily detectable from the ground by a visual inspection. In this paper, the mechanical reliability of toughened glass insulators is investigated through the analyses of experimental data obtained from laboratory tests. First, the mechanical strength of the toughened glass in insulators and the relationship between its failing load and the geometry of the insulator are investigated by means of a novel analytical approach. Afterwards, the risk of mechanical failure of glass insulators and stubs, with the shell broken off, is analysed. The results show the mechanical reliability of glass insulators for different string configurations and for large and complex systems deployed in 220 kV and 400 kV transmission lines. Finally, the effect of the shattering rate on the reliability is studied under the most adverse conditions.

In this paper, a four port MIMO antenna of compact split ring resonator (SRR) type with high degree of isolation among four ports on the antenna has been proposed for MIMO multiband applications. It is Tribands which operate at frequencies 1.44 GHz (−11 dB), 2.3GHz(−10 dB) and 4.2 GHz (−245 dB) respectively. This proposed MIMO antenna is designed with meander line for better gain and Split Ring Resonator (SRR) in the form of ring for high isolation between the antenna elements. A loaded stub is used to achieve the resonant frequency. The proposed MIMO antenna was simulated with IE3D EM software by Mentor graphics and the features such as impedance view, lower return loss, gain, radiation pattern and VSWR, etc are measured. The proposed antenna has better gain and provides higher isolation between multiple antenna elements.

A liquid metal Filtering Power Divider (FPD) with frequency tuning and controllable number of passbands is proposed in this paper. According to the resonance characteristics of uniform impedance resonator (UIR) and stub loaded resonator (SLR), the structure parameters of the FPD are given. The proposed FPD consists of 4 UIRs, 4 SLRs and the liquid metal adjustable modules. By changing the position and length of liquid metal, different center frequency and passband number can be obtained. Two-passband and three-passband are realized on the same FPD. In the two-passband mode, the center frequency of both passbands can be tuned. In the three-passband mode, there are two tuning modes, which can tune the first two pass bands and the third pass band respectively. The designed FPD innovatively applies liquid metal to the structure and has flexible adjustability. In order to verify the proposed design, a reconfigurable FPD based on liquid metal is fabricated and measured. The measured results are in good agreement with the simulated results.

In this brief, we present a miniaturized spoof surface plasmon polaritons (SPPs) load for planar terahertz (THz) circuit application on thick substrate. The proposed SPP cell consists of a groove-shaped structure integrated with a folded stub. The coupling between the stub and the grooves enlarges the capacitance, reduces the cutoff frequency, and miniaturizes the SPP size. The strong field confinement of the SPP waveguide leads to tremendous insertion loss near the cutoff frequency. Furthermore, due to the low conductivity and high permeability, the SPP structures made of nickel (Ni) metal increase the metallic loss to 40 folds that of the aluminum (Al) case, effectively absorbing the propagating electromagnetic wave. Therefore, the tapered SPP structure made of Ni metal can operate as a load with a compact size of 1.7 λg × 0.23 λg (λg is the guided wavelength at 300 GHz). The reflection coefficient of this compact SPP load is below -20 dB in the 195 -500 GHz band. Finally, this SPP load is utilized in an equal-power two-way Goubau-line divider, with 0.194 λg substrate thickness, operating in 220-325 GHz band. The simulated and experimented results are consistent, indicating that the proposed compact SPP load could serve as a matching load for THz multiple-port circuit application on thick substrate.

A novel quasi-reflectionless bandpass filter (BPF) using double-sided parallel-strip line (DSPSL) is proposed in this letter. It is composed of a BPF and two symmetric absorptive bandstop filters (ABSFs) terminated by a pair of resistors that can dissipate the input untransmitted signal energy. Through detailed analysis, the high characteristic impedance is required for the open-circuited stubs of the ABSFs to enhance the selectivity. This cannot be realized in traditional microstrip designs, but it can be obtained easily by offsetting the DSPSL. Meanwhile, the BPF with T-shaped structure consists of a half-wavelength (λ/2) DSPSL with a centrally-loaded λ/2 stub, which answers for generating two transmission zeros (TZs) to achieve better out-of-band suppression. For demonstration, a prototype is designed, fabricated and measured, and the simulated and measured results with good agreement are presented.

In memory devices, such as solid-state drive, multitopology is used for interfaces where multiple memory packages are connected to a controller using a branched transmission line. Impedance mismatching caused by the branches and unwanted reflection from deactivated packages inevitably degrades signal quality, limiting the data rate of the interface. In this article, a simple stub equalizer is proposed to improve the data rate of the memory interface. An open-ended stub is placed between a transmitter and a receiver, and the length, impedance, and location of the stub line are determined to properly cancel the reflection from other branches. Parameters are optimized based on the peak distortion analysis and an exhaustive search considering both read and write modes. The improvements are validated through eye-diagram simulations.

The present study numerically evaluates the behavior of the Simpson Strong-Tie (SST) connection that uses a modified T-stub (the Yield-Link structural fuse) with European sections. This study focuses on 3 topics: a) mesh sensitivity analysis in numerical T-stub connection; b) Investigating behavior of the SST connection containing seismic behavior of specimen, connection and panel zone along with stiffness and strength of the connection; c) investigating solutions for enhancing the connection stiffness without changing the existing geometry of the main connection components. To examine the prequalification of SST connections with European sections, five specimens were built according to the AISC-358 standard. The results indicated that the specimens met the general prequalification requirements. All the specimens exhibited satisfactory seismic behavior; no specimen underwent strength deterioration at a rotation of up to 0.06 rad, and the moment-rotation curves showed incremental trends. The maximum pre-tension of the Yield-Link flange bolts increased the connection stiffness of the specimens by 11–12%, while it had a contribution of below 1% on moment strength improvement. Also, the maximum pre-tension of the Yield-Link flange bolts and the doubler plate reinforcement of the panel zone improved stiffness by 11–14% relative to the specimens without doubler plate reinforcement, while it had an effect of below 1% on the connection moment strength improvement. All the fifteen SST connection specimens of the present study are partially restrained (PR) and Full-strength connections. The results demonstrated that all the fifteen specimens were able to serve as structural fuses. Thus, it can be generally said that the use of the SST connection with European sections in structures is allowed if the requirements of the AISC-358 code are observed.

A compact body-worn circular polarized textile monopole antenna for wearable applications is reported. The proposed antenna is fabricated on a jean fabric providing flexibility, light-weight, and easy integration into human clothes. The overall size of the proposed antenna is 25 × 30 × 1.4 mm3. Circular polarization (CP) is advantageous for on-body communication as it provides features such as multipath immunity, suppressing interferences, and enables better link connectivity between the sensor nodes. The proposed antenna achieves the CP using an asymmetric stepped L-shaped ground plane and through the incorporation of cross-shaped stub in the radiator. The single fed octagonal strip monopole antenna provides good impedance matching over the entire ultra-wide frequency range from 3.09 -11 GHz. Simulation results are in good correlation with the measured results. Axial ratio bandwidth < 3 dB is achieved in the frequency range of 3.4-10 GHz. Gain and efficiency obtained are about 2.3-4.4 dBi and 65-82% at the said frequency range respectively. Structural deformation is performed to analyze the flexibility of the proposed antenna. The simulated SAR values follow the FCC limit making it most suitable for wearable applications.

A novel compact and wideband circularly polarized (CP) crossed dipole antenna is presented. To realize CP radiation, a new design concept of using coupling stub is first illustrated. The coupling stub is equivalent as a combination of a dipole-c and dipole-y. The dipole-c not only couples proper energy from the x-axis arranged driven dipole-x to the orthogonally arranged dipole-y, but also provides quadrature phase delay to the dipole-y. Therefore, CP radiation is realized for the presented configuration. To improve the input impedance caused by the strong coupling, a long narrow strip is incorporated for the enhancement of impedance bandwidth. Based on the design concept, a compact and wideband CP antenna by using the coupling stub and stepped square loop is developed to further increase the operation bandwidth and realize stable radiation. The designed antenna was finally fabricated for performance verification. Both the simulation and measurement show that the developed antenna can have a wide overlapped impedance and AR bandwidth from 1.1 to 1.74 GHz with a compact radiator size. In addition, stable antenna gain and radiation patterns are achieved for wireless communications.

This paper proposes a shared-aperture self-diplexing antenna using the composite parallel-plate waveguide (PPW). The long-straight slots (LSS) etched on the top surface of the PPW are utilized as the common radiation aperture for two operating bands. At the high frequency band, the proposed antenna, excited by the alternative-phase TE10-mode wave, operates as a leaky-wave antenna (LWA). Meanwhile, it serves as a continuous transverse stub (CTS) array antenna when excited by the TEM wave at the low frequency band. Two kinds of feeding networks are adopted to generate the alternative-phase TE10-mode wave and TEM wave, respectively. To verify the proposed method, a millimeter-wave prototype is designed, fabricated and measured. The measured results show that -10 dB fractional bandwidths are 3.42% (76.25-78.9 GHz) and 14.5% (83.2-96.2 GHz), respectively, and the port isolation is higher than 40 dB. Additionally, the peak gains are 27.1 dBi at 78.5 GHz and 25.3 dBi at 90 GHz, respectively. The proposed antenna can be used to develop compact frequency-division system without using duplexers and multi-band wireless systems.

Design procedure of a novel transmission line low‐pass filter is presented. The filter has a flexible rejection response for a prescribed cut‐off frequency and an in‐band ripple factor. It is compact by using a Z‐shaped coupled‐line section, which is loaded with open‐circuited stubs. All of the transmission line elements are identical in electrical length, and the impedances can be calculated by solving certain specific equations according to prescribed in‐band specifications. The simulated results show that the circuit can generate low‐pass responses with third‐, fifth‐, and seventh‐order filtering functions. The filter order depends on the number and position of the loading stubs. For verification, two sample filters with cut‐off frequency of 0.5/0.3 GHz are fabricated using a three‐/five‐layer PCB process, which generate seventh‐order low‐pass filtering responses with good selectivity. The experimental results agree well with the predictions.

A differentially fed dual-mode patch antenna is proposed with wideband common-mode (CM) absorption. The proposed antenna consists of a differential feeding network, common ground plane and the radiation patch with stepped widths. The differential feeding network is formed by adding an absorptive stub at the symmetric plane of balanced microstrip structure to achieve wideband CM absorption. Besides, a T-shaped slot is etched on the ground plane to realize aperture coupling to excite the radiation under TM01 and TM11 modes. Subsequently, the differential parallel feeding technique is employed to design a 2×4 planar array with low cross polarization. As demonstration, the prototypes of the designed differential antenna and array are fabricated and measured. The measured results show that the proposed antenna element and array exhibit the broadened -10 dB impedance bandwidths covering the frequency range of 4.8 GHz to 4.99 GHz, wide CM absorption band with about 70% fractional bandwidth, and low cross polarization below -20 dB. Furthermore, the measured peak realized gains of antenna and planar array are 7.5, and 16.6 dBi, respectively.

In this brief, novel single-layer dual-band bandpass filters (BPFs) with input-/two-port all-frequency absorptive performance are presented. The design consists of a simple coupled-line (CL) based dual-band BPF section and auxiliary dual-band bandstop filter (BSF) sections with resistively terminated absorptive stubs. The dual-band BPF can transmit spectral energy in two operational passbands with good in-band filtering response, while the out-of-band RF-signal energy can be well absorbed by auxiliary BSF sections shunted at input/output ports, which indicates all-frequency absorption from DC. Besides, the impedance of the absorptive stub and the value of the grounded resistor can be independently adjusted to enhance the absorption performance. Furthermore, the operational foundations and explicit design equations are discussed and derived. Good agreements between the simulated and measured results verify the design theory.

This study is aimed at addressing the experimental and theoretical investigation of the compressive behavior of steel reinforced concrete (SRC) composite columns containing steel fibers considering the stirrups’ confinement effects. Variables used to fabricate and evaluate the performance of the steel reinforced fibrous concrete (SRFC) columns include the steel profile shape (both H -shaped and C -shaped), volume fraction of steel fibers ( 0 , 0.75 , and 1.25 % ), and spacing of stirrups ( 40 , 65 , and 130 m m ). In total, 36 short column specimens were fabricated and such parameters as the axial bearing capacity, compressive stress–strain curves, ductility, peak strain and toughness were investigated through the axial compression test. According to the results, the axial bearing capacity of concrete-confined steel columns was affected by the steel shape inside; the axial bearing capacity of H -shaped cross-section columns was more - due to their more confinement - than that of C -shaped ones. Although adding, and increasing the percentage of, steel fibers increased the columns’ axial bearing capacity slightly (up to 6 % ), their ductility and energy absorption improved significantly. Increasing the spacing of stirrups from 40 to 130 m m not only resulted in a 12 % reduction in the axial bearing capacity, but also reduced the contribution of the composite action of both H - and C -shaped profiles by more than 70 % . Finally, as predicting the SRC column strength is important, relationships presented by ACIITG , A S 3600 , C S A - A 23 , E N 1994 , J G J 138 , and N Z S 3101 for the prediction of the axial bearing capacity were thoroughly studied and showed that all had ignored the confinement effects. Considering the latter, this study modified the relationships, corrected the predicted results and compared them with both the experimental results of this study as well as those of other researchers’ which showed a good correlation between the results.

This paper presents an experimental and numerical investigation on the local buckling behaviour of a new built-up Cold-Formed Steel (CFS) homogeneous and hybrid Double-I-Box Column sections (DIBCs and HDIBCs) under axial compression. In total, 24 experimental tests are conducted, out of those 12 tests are on stub columns and the remaining 12 are on short columns. The parameters considered are hybrid ratio (Φh), section’s breadth to depth ratio (B/D) and column height (H). The columns considered in this study are having an overall slenderness (λ) less than 0.20, and the flange plate slenderness (λpf) less than 1.85. Test specimens failed in either of the following three failure modes: local buckling, yielding or by the interaction of both. In all the tested specimens, typical Bottom Zone Local Buckling (BZLB) similar to the shape of Elephant’s Foot is identified. The deformation shape is recognized by expansion (outward buckling) along the major axis and contraction (inward buckling) along the minor axis at the bottom 1/4th height of the columns in opposite faces, followed by the collapse. This kind of failure mode is a clear representation of Poisson’s ratio effect at the ends causing a restraint which then creates a local imperfection under load which leads to a localized failure at bottom zones in the stub and short columns of DIBCs and HDIBCs. BZLB phenomenon is enhanced because of the tubular cross-section geometry, boundary conditions plate element slenderness, overall slenderness of these built-up sections. The ultimate capacities of both the stub and short columns are governed by their strength limits and slenderness. Nonlinear Finite Element Analysis (FEA) is performed on experimental FE models using ABAQUS software and verified against the test results and validated with the actual structural behaviour. Further FEA is performed on 96 ideal parametric FE models considering different material properties and slenderness values. Effect of the intermediate longitudinal stiffener and the influence of edge constraints on axial strengths are also reported. The axial strengths obtained from the experimental tests and FE parametric studies are compared with the predicted results using the Effective Width Method (EWM) as suggested in the Eurocode specifications to access the feasibility of the current design rules, which is found to produce reasonable predictions albeit slightly conservative. It is found that for stub columns with λ 0.1, the experimental values are found to be 1.25 times higher than the predicted values. It is also observed that for columns having λ ≥ 0.1 0.2 with λpf > 1.2 there is a reduction in local buckling resistance of around 2.5% for each increase of λpf by 10%. Hence, it is concluded that the concentric axial compression capacities of DIBCs and HDIBCs subjected to local buckling can be computed as the arithmetic summation of effective strengths of individual channel sections calculated by using the EWM design equations, as recommended in this study. The attained results prove that these sections have a considerable local inelastic reserve strength as specified in North American standards.

The concrete-filled wide rectangular steel tubular (CFWRST) column is attracting more and more attention in engineering practice. The aspect ratio of CFWRST section is normally 2.0–3.0, which exceeds the limitation in existing studies, being less than 2.0. The finite element (FE) analysis has been widely used in investigating behavior of the concrete-filled rectangular steel tubular (CFRST) columns, where many parameters need to be calibrated using test results. This paper presents an investigation on behavior of CFWRST stub columns under axial compression using ABAQUS. On the basis of original constitutive model for confined concrete, the constitutive model for simulating CFWRST stub columns is presented, in which the involved parameters are calibrated using existing test results. The proposed model is verified to be suitable for simulating CFWRST stub columns, and it is considered to be capable of well extending the application range of the original model in CFRST columns with large aspect ratios. Subsequently, a total of 330 CFWRST columns are analyzed to investigate the effects of key factors on the behavior of CFWRST stub columns. Finally, based on the analyses, the limitation of width-to-thickness ratio of steel tube in CFWRST stub columns is presented, and solutions are also proposed for the ultimate axial load of CFWRST columns.

This paper explores an original study of bandpass (BP) negative group delay (NGD) robustness applied to the ring-stub passive circuit. The proof of concept (PoC) circuit is constituted by a ring associated with the open-end stub implemented in microstrip technology. An innovative experimental setup of a temperature room containing the NGD PoC connected to a vector network analyzer is described. Then, the electrothermal data of S-parameters are measured by varying the ambient or room temperature range from 20 to 60°C, i.e. 40°C maximal variation. The empirical results of the group delay (GD), transmission and reflection coefficient mappings versus the couple (temperature, frequency) highlight how the temperature affects the BP NGD responses. An innovative electrothermal calibration technique by taking into account the interconnection cable influence is developed. The electrothermal robustness analysis is carried out by variations of the NGD center frequency, cut-off frequencies and value in function of the temperature.

A compact dual-band ram horn-like folded antenna is presented in this work. The antenna is based on a ram horn-like folded strip, asymmetric microstrip feeding (AMF) technique, partial ground, and protruding stub at the ground plane. The dimension of the proposed antenna is 0.11 λ g × 0.17 λ g at 2.3 GHz (10 × 15 mm2). The proposed shape is achieved through the combination of two circular arcs with different radii. The antenna operates at 2.3 GHz and 5.8 GHz with a measured bandwidth of 100 MHz and 820 MHz, a gain of 0.62 dBi and 2.2 dBi, and radiation efficiency of 93.67% and 99.87%, respectively. The prototype of the proposed antenna is fabricated and measured. The measured result shows a good agreement with the simulated result. The parametric study of the proposed antenna is performed and results are presented. Besides, a comparative study between the antennas proposed in this work and the state of the art is performed and presented. The proposed antenna is comparatively small in size than all the recently reported works in the literature while ensuring good radiation characteristics. Therefore, the antenna proposed in this work is a better candidate for future portable sub-6GHz fifth-generation (5G), Advance Long-term Evolution (LTE-A), Worldwide Interoperability for Microwave Access (WiMAX), and Wireless Local Area Network (WLAN) applications.

This letter describes the design of a right-hand circularly polarized planar filtenna (filter + antenna) that can reconfigure its operation between two center frequencies in the Ka-band. The filtenna structure is composed of a four-element array radiator and a reconfigurable bandpass filter, occupying an area of 31 × 14 mm. The circularly polarized array elements are fed by a sequential power divider for an enhanced polarization purity. The filter is based on a ring resonator loaded with a variable open stub. The length of the stub extends through a p-i-n diode switch, resulting in a change of the loaded reactance into the ring, and consequently tuning the filter's operating center frequency from 30.3 to 29 GHz. The proposed low-loss filtenna structure exhibits a reconfigurable fractional bandwidth up to 7.74%, a peak realized gain that can reach up to 11.5 dBic, an axial ratio of less than 1 dB, and a sidelobe level that can go as low as −12 dB. The prototype filtenna is fabricated and tested, where the measured results verify the simulated data. A figure of merit is proposed to highlight the superior performance of the presented Ka-band structure in terms of the polarization, size, reconfiguration ability, and radiation characteristics as proven by the comparison with other works in the literature.

This study presents a unified approach to simulate the behavior of rectangular concrete-filled steel stub columns incorporating high strength and ultra-high strength materials subjected to concentric axial compression. The finite element model is developed based on Abaqus software, which is capable of accounting for geometrical nonlinearity, material plasticity, and interaction between multi-physics. The proposed model incorporates the influences of residual stress for welded-box steel sections and initial imperfection. A novel stress-strain relation of confined concrete is proposed to account for the composite action, which might increase the strength and ductility of infilled concrete under multi-axial compressive conditions. Various verification examples are conducted with wide ranges of geometrical and material properties. The simulation results show that the proposed model can accurately predict the ultimate strength, load-deformation relations, and failure mode of the experimental specimens.

In this paper, a two-port dual-band antenna is designed with high isolation. The beak-shaped radiator and open stubs are used to achieve miniaturization of the antenna. A T-shaped stub is used to i...

To minimise the profile of Satcom‐on‐the‐Move ground terminals, in this study, a two‐dimensional beam‐scanning continuous transverse stub antenna that is based on a compact linear source generator (LSG) is presented. A periodic anti‐symmetric two‐step (ASTS) structure cascaded with a broadband network is used to construct a single‐layer compact LSG. The concept of a parallel‐plate waveguide polarisation twister is used to design the ASTS unit that acts as a TE10‐to‐transverse electromagnetic wave converter, to which chamfers and T‐type grooves are added to improve the output plane wave performance over the entire frequency band. A prototype array operating in the band 10.95–12.75 GHz is designed, fabricated, and measured, and the experimental results agree well with the simulated ones. A beam‐scanning range of ±61° in elevation is achieved at the central frequency. Although only 29 of 36 slots (ϕ = 0°) contribute to the radiation, the antenna aperture efficiency is still over 60% due to the superior performance of the single‐layer minimised LSG.

This paper presents the methodology of EM-field localization in rectangular waveguide using dual layer metamaterial interface for sampling different soil samples. The prototype design consists of WR229 waveguide in which array of metamaterial unit-cell is loaded. A sample loading cell is created in the waveguide where two MTM array layers are kept at $\lambda _{g}/4$ spacing with respect to coaxial feed probe. The metamaterial unit-cell has two open-ring resonators connected with a short stub, and it helps to create a stronger localized resonance in the waveguide. This enables stronger EM field penetration into the soil sample that is under test. The fabricated device has dual resonance at 2.284 GHz and 3.091 GHz. The dielectric characterization of different dry-soil samples like black soil, silt soil, red soil and sand soil is presented. The applicability of the proposed device is also demonstrated for moisture analysis of soil samples with water content ranging from 2% to 14 %. The proposed device yields lower percentage error in extracting the dielectric constant values of the test soil samples. The on-field measurement of the soil sample which is extracted from different depths of soil surface is also presented and analyzed for dielectric estimation. The proposed device can be used in agriculture field testing application for testing properties of soil like dielectric constant and moisture level.

The mechanical properties of CFRP-confined rectangular concrete-filled stainless steel tube (CFSST) stub columns under axial compression were experimentally studied. A total of 28 specimens (7 groups) were fabricated for the axial compression test to study the influences of length-to-width ratio, CFRP constraint coefficient, and the thickness of stainless steel tube on the axial compression behavior. The specimen failure modes, the stress development of stainless steel tube and CFRP wrap, and the load-strain ratio curves in the loading process were obtained. Meanwhile, the relationship between axial and transverse deformations of each specimen was analyzed through the typical relative load-strain ratio curves. A bearing capacity prediction method was proposed based on the twin-shear strength theory, combining the limit equilibrium state of the CFRP-confined CFSST stub column under axial compression. The prediction method was calibrated by the test data in this study and other literature. The results show that the prediction method is of high accuracy.

In this paper, Monte Carlo Simulation (MCS) and the simplified fourth-moment method based on cubic normal distribution are used to analyze the reliability of bearing capacity formula of concrete-filled steel tubular stub columns (CFST) under axial compression proposed by Ding Faxing, which considers the shape confinement coefficient of steel tube. The influence of different section shapes, different strengths of concrete and steel, two load combinations and different load ratios on the reliability index are considered. The results show: (1) the reliability index of MCS and simplified fourth-moment method are close, and the maximum difference is less than 5%; (2) the reliability of bearing capacity formulas of CFST with different cross sections meet the requirements of target reliability index 3.2; (3) When the ratio of office live load to dead load is 1.0, the lower the steel ratio and the higher the concrete strength, the greater the reliability index.

In this paper three different multi stub antenna arrays at 27–29.5 GHz are designed. The proposed antenna arrays consist of eight single elements. The structure of feeding parts is the same but the radiation elements are different. The feeding network for array is an eight way Wilkinson power divider (WPD). To guarantee the simulation results, one of the proposed structures is fabricated and measured (namely the characteristics of S11, E-, and H-plane patterns) which shows acceptable consistency with measurement results. The simulation results by CST and HFSS show reasonable agreement for reflection coefficient and radiation patterns in the E- and H- planes. The overall size of the proposed antenna in maximum case is 29.5 mm × 52 mm × 0.38 mm (2.8 $${{\varvec{\lambda}}}_{0}$$ λ 0 × 4.86$${{\varvec{\lambda}}}_{0}$$ λ 0 × 0.036$${{\varvec{\lambda}}}_{0}$$ λ 0 ). Moreover, for Specific Absorption Rate (SAR) estimation, a three-layer spherical human head model (skin, skull, and the brain) is placed next to the arrays as the exposure source. The simulation results show that the performance of proposed antennas as low-SAR sources makes them ideal candidates for the safe usage and lack of impact of millimeter waves (mmW) on the human health. In all three cases of SAR simulations the value of SAR1g and SAR10g are below the standard limitations.

This paper presents the parametric study of single square perforated fixed ended LDSS (Lean Duplex Stainless Steel) flat oval section stub columns, by varying the square perforation size, location of perforation along transversely as well as longitudinally, using the Finite element software Abaqus (2009). Based on the Finite element study, a near-linear reduction in ultimate load capacity with perforation size has been observed. The reduction is found to be higher for the stockier cross-sections as compared to slender sections. The percentage drop in ultimate load capacity remains relatively unaffected for larger perforation when the section is slender and located at the flat element. It is seen that, in comparison to the slender section, perforated stocky sections showed a mild drop in ultimate load as the perforation is located toward the corner junction of flat and curve portion from the mid-flat region. Further, in general, it is observed that the reduction in load capacity to be highest when the perforation is located near the mid-height. A design approach based on modified ASDM (Automotive Steel Design Manual) has been proposed to estimate the design capacity of single square perforated flat oval LDSS hollow columns

This letter presents a broadband rectifier that can be applied to harvest ambient radio frequency (RF) energy. The matching network consists of three-stage transmission lines. A cross-shaped match stub of two one-eighth-wavelength transmission lines is proposed to realize efficient and broadband impedance compression. The proposed circuit has been optimized and manufactured, and the measured results show that the rectifier can achieve high RF-to-dc conversion efficiency and broadband characteristics. The simulation and measured results were basically consistent. When the input power is 8 dBm and the terminal load is 1.6 $\text{k}\Omega $ , a bandwidth of 81% (1–2.35 GHz) with an efficiency above 50% and a bandwidth 69% (1–2.05 GHz) with an efficiency above 60% are achieved. The highest conversion efficiency of the test circuit is up to 73.2% at an input power of 8 dBm. Moreover, when the input power changes from 1 to 11 dBm, the efficiency of the rectifier circuit is always above 50%.

A new type of concrete-filled steel tube (CFST) structural member is proposed by replacing the central portion of the infilled concrete with a stone prism. The mechanical behavior of the stone prism encased concrete-filled steel tube (SCFST) members under axial compression was studied through experimental testing. A total of twenty-four stub columns, including eighteen SCFST specimens and six CFST specimens, were subjected to axial compression until failure occurred. The primary parameters considered were the size of the stone prism (s = 75 mm, 100 mm or 125 mm), wall-thickness of the steel tube (t = 6.0 mm, 8.0 mm or 12.0 mm), and concrete strength (fcu = 62.3 MPa or 107.0 MPa). Test results demonstrated the composite actions between the three parts of the member, which significantly enhanced the load-carrying capacity of the SCFST column. The effect of the parameters on the failure mechanism, load-carrying capacity, load versus deformation response, and ductility of the SCFST specimens was researched. Meanwhile, the experimentally obtained axial compressive strength of each SCFST specimen was compared with predicted strengths obtained by adopting the formulae from currently available design codes for conventional CFST columns. These design codes could not precisely predict the load-carrying capacity of SCFST stub columns, and an improved model was proposed.

Classic сoupled-line couplers with a high lateral coupling level by type of directivity are counterdirectional. Restrictions on their synthesis are imposed by the gap between transmission lines, which must be extremely small (tens of microns), the difference in the phase velocities of even and odd modes, which must be compensated and others. This makes it difficult of manufacturing couplers. Described in technical literature сoupled-line couplers with a high lateral coupling level with changed types of directivity are either quite bulky or have small dimensions due to the use of discrete inductors and capacitances, which complicates the technological process with surface mounting when implementing the final device. In this article we propose a compact сoupledline coupler with a high lateral coupling level, which implements power transfer to a single port (0 dB, crossover). The coupler topology uses periodic loops that are located between сoupled-line. The equivalent circuit of the coupled lines was calculated and analyzed for a single periodic stub. This allowed us to determine the necessary parameters and dimensions of the topology. The device is narrow-band (3 GHz ± 5 %), transmission coefficient minus 0.44 dB at the center frequency of 3 GHz, isolation for isolated ports is not less than 35 dB. The proposed compact coupler with a coupling level of 0 dB suits building distribution circuits in which it is necessary to exclude the intersection of transmission lines. The information on the synthesis of the 3 dB co-directional microwave coupler on coupled strip lines with lateral electromagnetic coupling is given. The coupler is characterized by a high isolation level with an isolated port, not less than 40 dB. The imbalance of the amplitudes between the working (through and connected) and the input port is minus (3.4 ± 0.8) dB.

A dual-band antenna with large frequency ratio for microwave and millimeter-wave applications based on the dual-mode coplanar waveguide (CPW) transmission line is investigated in this letter. The dual-mode operation of the transmission line is obtained by introducing a rectangular stub to traditional CPW, which can provide different phase shift in different frequency bands. In the millimeter-wave band, the dual-mode transmission line can support odd mode while it supports even mode in the microwave band. Based on this, the dual-band antenna which operates as monopole antenna in the microwave band and Vivaldi antenna in the millimeter-wave band is realized using the same aperture. Moreover, the radiation structure for monopole in the microwave band is designed to enhance the radiation performance of the antenna in the millimeter-wave band. For verifying, the prototype of the antenna is fabricated on a Rogers 4003 substrate with an overall size of 45 × 20 × 0.508 mm3 and the measured results agree well with the simulated ones.

A novel decoupling network consisting of inter-digital capacitors and a short-circuited stub to improve the isolation of two closely spaced (edge-to-edge separation is 0.013λ0, where λ0 is the reso...

This letter presents a millimeter-wave (mmW) continuous transverse stub (CTS) leaky-wave antenna (LWA) with pencil-beam broadside radiation, high scanning-rate, and low sidelobe levels (SLLs) characteristics. A parallel-plate waveguide (PPW) meander delay line is employed to control the phase constant of the proposed LWA. By adjusting the length of the transverse electromagnetic TEM-mode PPW delay line, the phase difference between adjacent radiating elements can be altered, achieving flexible control of scanning-rate. Match stubs close to the radiation slots are utilized to suppress the open stopband, which help enlarge the beam scanning range. A linear source generator excited by multiple ports with amplitude tapering is employed to generate the quasi-TEM wave. Combined with additional amplitude tapering among the CTS radiation slots, low SLLs at both principal planes are realized. Experimental results show that the LWA with 12 radiation elements has a scanning range of −68° to 42° over the frequency range of 26–34 GHz (a scanning-rate of 13.75°/GHz) with SLLs lower than 13.5 dB/16.6 dB and a peak gain of over 22.5 dBi.

This article proposes a novel design of the dual-band antenna pair. Starting from the single-band antenna pair composed of T-shaped monopole and T-shaped slot that are intersected with each other, orthogonal T-monopole and odd-symmetrical slot modes are excited. By adding symmetrical low-pass high-stop filters into the horizontal stub of the T-monopole and high-pass low-stop filters into the gap of the T-slot, an extra mode is introduced for each antenna, producing dual-band operation. Impedance bandwidths and radiation efficiencies of both bands can be adjusted flexibly using the filters. A detailed design guideline is given. The dual-band antenna pair operating at partial N78 (p-N78, 3.4~3.6 GHz) and partial N79 (p-N79, 4.8~4.9 GHz) is with a footprint of $15\times 6$ mm2. The measured results show that the average efficiencies are both −3.4 dB at p-N78/p-N79 for the odd-symmetrical slot and −2.8 dB/−3.7 dB at p-N78/p-N79 for the T-monopole, isolations are better than −16.8 dB at p-N78 and −11.8 dB at p-N79, and ECCs are lower than 0.1 at p-N78 and 0.2 at p-N79. The proposed dual-band antenna pair exhibits great potential to be applied in the fifth-generation (5G) multiple-input multiple-output (MIMO) terminal.

This work proposes the design and implementation of a wearable rectifying filtenna (filtering antenna) which is activated and powered wirelessly, to detect the presence of ethanol solutions. The system is implemented on a Rogers RT/Duroid 5880 substrate ( $\varepsilon _{r} =2.2$ and thickness: 0.508 mm), whose flexibility facilitates the system wearability. The fluid detection is performed by a resonant stub embedding a microfluidic channel on its end, which resonates as an open circuit at 2.45 GHz when the channel is filled with the ethanol solution and undergoes a dramatic shift on its input impedance behavior when the channel is filled with water or when it is empty. The system is powered wirelessly by means of a 2.45-GHz narrowband antenna, and the frequency selection is performed by a second-order open-end coupled-line filter whose one end is loaded with the resonant stub. The filtenna RF signal is transduced by a full-wave rectifier exploiting low-threshold voltage diodes, and fluid detection is read out through different values of dc-output voltages, allowing an immediate response. The system is designed and optimized by means of full-wave/nonlinear co-simulations and the realized prototype is measured to confirm a safe detection of the tested solution.

In this letter, the design of a $C$ -band high-efficiency power amplifier (PA) with a compact harmonic control network (HCN) is presented. Based on the device model, the optimal fundamental and second harmonic load impedance was obtained by load-pull simulation. Then a simply fundamental matching network (FMN) is realized using the simplified real frequency technique (SRFT). To improve efficiency, a compact HCN based on a predesigned FMN is proposed. Besides, the microstrip radial stub (MRS) is used instead of the microstrip open-circuited stub to reduce the loss. A high-efficiency PA working across 6.1–7.2 GHz is simulated and fabricated. Experimental results show that the fabricated PA delivers a saturated output power of 38.2–39.3 dBm with a drain efficiency (DE) of 43%–63.4% in the interested band.

This paper presents a low-profile, high gain, beam-tilted continuous transverse stub (CTS) array antenna at W-band. The antenna compromises 32 radiating slots and is fed by a parallel plate waveguide (PPW) network with a linear source generator. To deflect the outgoing beam, the principle of linear array scanning is adopted to design inverted T-type structure in each stub to introduce wave path difference. PPW network allows the antenna to obtain lower profile compared to other transmission lines. The design procedure, and the antenna characterization are described. The main beam of the antenna is titled 12 degree in H-plane. The simulation and measured results show that this antenna achieves peak gain of 32.4 dB and a 12 degree beam tilt angle at 99GHz. S11 parameters of the antenna is less than -10 dB in a broadband from 96 GHz to 103 GHz. This antenna has an advantage of miniaturization over other high-gain antenna solutions. The promising performance of this proposed CTS antenna reveals the possible candidate for Millimeter wave (MMW) telecommunication applications.

In this paper, a microstrip single feed circular radiating patch loaded with two parasitic stubs to achieve diversity for antenna polarization is presented. The primary antenna is a circular metall...

In this paper a novel fully-textile chipless tag for gesture recognition applications is presented. The proposed tag consists of a microstrip line with transmission zeros controlled by the position of the fingers. This is obtained by associating to each finger an open ended stub that is electrically connected or not to the microstrip line depending on the finger position. A three-finger prototype fabricated by using a non woven conductive fabric and suitable to be integrated into a glove is presented and discussed. The reported results demonstrate the suitability of using the proposed tag for gesture recognition applications.

This paper presents a new coplanar waveguide (CPW)-fed circularly polarized square slot antenna (CPSSA). The proposed antenna uses an inverted Z-shaped feedline protruded from the signal line of the feeding CPW. Circularly polarized (CP) radiation can be achieved by adequately inserting the arc-shaped grounded strip into the upper right corner of the square slot. The widened vertical tuning stub on the L-shaped grounded strip can improve impedance matching and axial ratio (AR) performance. The measured results indicate that the 10 dB impedance bandwidth is 620 MHz (652-1272 MHz), and the 3 dB axial ratio bandwidth is 320 MHz (840-1160 MHz), which has a broadband characteristic. In the range of the universal UHF RFID band, the measured peak gain is about 4.4 dBi. The proposed CPSSA uses low-cost FR4 material as the dielectric substrate. The overall size of the antenna is 119 × 119 × 0.5 mm3. The proposed antenna has a simple structure, easy processing, good performance, wide operating bandwidth, and dual circular polarization characteristic. It can be applied to the universal UHF RFID handheld reader environment.

In this paper, a circular antenna with a 3-D printed substrate is introduced to achieve a multiband behavior. The circular antenna is matched using a key-shaped stub located on the perimeter of the designed antenna. The 3-DP circular antenna adopted the apollonian gasket technique to perform the multi-circular cuttings in the Polylactic Acid (PLA) substrate as an innovative technique to obtain quintuple bands. The proposed antenna is designed to operate for Bluetooth, WLAN, WiMAX, and other wireless applications in S-band and C-band. The designed antenna has a compact size of 61.1 × 43.6 × 1 mm3. The prototype of the suggested 3-D printed antenna is fabricated and measured to confirm the simulation results. A good agreement is evident between simulation and experimental results which validates the design concept.

In this paper a dual E–shaped patch (ESP) antenna is proposed to enhance the wider impedance bandwidth to be use for wireless communications in 5G applications. The proposed dual ESP antenna performance analysis is carried out with stub in this work. The proposed ESP antenna with stub achieving reflection coefficient below -10 dB for obtained multiple resonant bands. The dual ESP antenna operates at 5.7 GHz,10.1 GHz,15.1 GHz,19.4 GHz and 22.4 GHz obtain reflection coefficient of −44.32 dB, −27.43 dB, −17.0 dB, −50.85 dB and −18.07 dB respectively. The proposed antenna with stub achieves impedance bandwidth of (4.28 GHz–24.06 GHz) with 139.37% enhancement resonate at 19.77 GHz operating frequency. The radiation patterns, current distributions and gain plots are observed at five resonant bands. The simulated results are matched well with the measured results.

A novel composite structural member, UHPC-encased concrete-filled steel tubular (UC-CFST) column, is proposed in this study to address the shortcomings of the ordinary concrete-encased CFST (OC-CFST) columns. A total of 22 specimens subjected to axial compression loading were tested, including nine UC-CFST stub columns, nine OC-CFST stub columns, and four CFST stub columns. The experimental results showed that the encasing UHPC of UC-CFST columns was less damaged than the encasing ordinary concrete of OC-CFST columns and did not spall when the UHPC was crushed. The UC-CFST stub columns reached their ultimate load-bearing capacity when the encasing UHPC attained the peak compressive strain, which was much greater than that of the OC-CFST stub columns. Compared to the OC-CFST stub columns, the ultimate load-bearing capacity of UC-CFST stub columns improved markedly by 75%–289% and the compressive stiffness increased by 22%–49%, while the ductility decreased by about 50% on average. Furthermore, increasing the area ratio of the encased CFST in the UC-CFST stub columns was unfavorable for the compressive stiffness and load-ultimate bearing capacity. Finally, by comparing the different calculation methods for ultimate load-bearing capacity of OC-CFST columns recommended by Chinese standard CECS 188, American standard AISC 360, Japanese standard AIJ-SRC, and European standard Eurocode 4, it was found that the calculation methods applicable to OC-CFST columns would underestimate the ultimate load-bearing capacity of UC-CFST columns to varying degrees. Thus, a modified calculation formula based on the CECS 188 standard was proposed for accurate prediction of the ultimate load-bearing capacity of the UC-CFST stub columns.

This communication presents a compact quarter-mode substrate integrated waveguide (QMSIW) cavity-backed self-diplexing tunable antenna. An open-ended slot is used to split the circular half-mode SIW (HMSIW) cavity resonator into two QMSIW cavity resonators. A varactor diode-loaded stub is added with each QMSIW resonator to achieve miniaturization and resonant frequency tuning. The miniaturization and tunability technique is demonstrated in a stand-alone QMSIW resonator and also in a QMSIW based self-diplexing antenna. The antenna is simulated, optimized, and subjected to practical testing inside a rectangular device. The device is treated as a quasi-receiver/transmitter, which consists of electronic circuitry and the proposed antenna. The resonant frequencies can be independently tuned by changing the values of the varactor diodes connected with each resonator. The simulated and measured results confirm that the proposed antenna can be tuned from 3.77 to 4.59 and from 4.96 to 6.1 GHz in the lower and higher frequency bands, respectively. The isolation between the two resonators in both bands is always better than 21 dB. The measured gains vary from 4.85 to 5.87 and 4.87 to 6.5 dBi in the lower and higher frequency bands, respectively. The proposed design shows stable and unidirectional radiation patterns in all tuning cases in both bands. The proposed self-diplexing tunable antenna is a competitive choice in compact and spectral-efficient radio frequency (RF) front ends where tuning is necessary for the efficient use of the frequency spectrum.