Structural buildings are vulnerable to many types of damages that can occur through their life period. These damages may cause structure failure or at least decrease its efficiency. Dangerous damages occurring in concrete structures are surface opening cracks or sub-surface cracks. So, the determination of location of these cracks is very important, because the crack location is one of the important factors that affect the degree of danger of the damage. The Rayleigh waves have many advantages, as they can be easily recognized due to the maximum energy of the wave components. So, it was used to determine the crack location in the previous works. In this paper, two different techniques are used to determine the crack location; one of them depends on the healthy case, and the other deals only with the cracked case. Common finite element software (Abaqus) is used to model the numerical simulation, and the experimental test is also performed to verify the obtained numerical results. Good agreement between the simulated and experimental results is obtained by employing both techniques to find the crack location.
In present scenario, this paper intends to demonstrate the practicality of a miniaturized coplanar waveguide fed metamaterial inspired antenna that can be effectively operated at dual bands. A broad-side coupled Split Ring Resonator is used to obtain dual bands with an impedance bandwidth (-10 dB) of 840 MHz (3.00-3.84 GHz) and 310 MHz (5.94-6.25 GHz), which resonates at dual bands, viz., 3.42 GHz and 6.07 GHz. The impedance bandwidth (S11<-10 dB) is 25% for the first band and 5.1% for the second band. The size of the antenna is 31 × 25 × 1.6 mm3 realized on a low-cost FR-4 Epoxy substrate. This antenna can be effectively utilized in worldwide interoperability for microwave access (WiMAX) and wireless access in vehicular environments (WAVE) applications. The prototype of the proposed antenna is fabricated and measured. Simulated and measured results are in agreeing nature. Experimental and simulated analyses of the antenna including parametric and dispersion characteristics are dealt in this communication.
The bandwidth of OAM antennas, which have a great potential for multiple-input multiple-output (MIMO) communication, must be wide enough. Unfortunately, most of researchers only care about the generation and characteristics of vortex beams carrying orbital angular momentum (OAM) but ignore the bandwidth of OAM antennas. To develop OAM antenna suitable for MIMO communication, Vivaldi antenna is used as the element of circular array because of its wide bandwidth. Three compact wideband circular Vivaldi antenna arrays that can generate vortex beams carrying OAM with numbers of modes l=0, -2, +2 are proposed and experimentally validated in this paper. Measured results show that the proposed antennas can radiate vortex beams with different numbers of modes over a frequency range of 2.7-2.9 GHz.
A new type of three-dimensional (3D) Frequency Selective Surfaces (FSS) applied to passive sensing in Structural Health Monitoring (SHM) is presented. Such passive FSS sensors are proposed as an alternative to conventional sensors to eliminate the need of DC/AC power. Moreover, these FSSs are modified in a 3D form to feature enhanced performance compared to conventional FSSs and sensors. More specifically, the proposed 3D FSS is able to control its sensitivity |S21| in either TE or TM incident waves. In this project, incident angle characteristics are evaluated for SHM applications to obtain angular responses of up to 80 degrees. The resonant behavior of the TE-incident wave is shown to be sensitive towards the incident angle and is suitable to be used for monitoring any building tilting and damage. This is due to the significant 3D length changes of the conductor elements. Meanwhile, the TM-incident wave is found to be insensitive towards the incident angle.
novel Ultra-wideband Willis-Sinha Tapered Slot antenna for landmine detection using Ground Penetrating Radar (GPR) system with enhanced gain and directivity is presented. The structure is constructed on a 235x270 mm2 FR4 dielectric substrate. The antenna is fed by a novel tapered coplanar waveguide (CPW) to coplanar stripline (CPS) transition feed. The antenna's impedance bandwidth is extended by adding an antenna arm constructing parabola shape with the antenna element. The antenna has a corrugated structure along the antenna outer edges to improve radiation efficiency and get higher directivity. Also, a mushroom-like circular EBG structure is used in the lower side of the antenna arm to reduce interference and enhance front-to-back ratio (F/B ratio). A partial substrate removal, like circular cylinders inside the substrate, is aligned with the antenna tapered profile to obtain better radiation efficiency and enhance antenna gain. The operational bandwidth of this antenna extends from 0.18 to 6.2 GHz. The minimum return loss reaches 60 dB. The average directivity reaches 12.2 dBi while the gain and radiation efficiency are 11.8 dBi and 92%, respectively with gain enhancement of 195% due to using corrugated structure and air cavities. The front-to-back ratio (F/B ratio) is 23 dB. Also, a size reduction of 48% is achieved due to using extended arm. The antenna performance was simulated and measured. Good agreement was found between numerical and experimental results. The proposed antenna is suitable for various ultra-wideband applications especially in landmine detection. The design of the proposed antenna is given in very simple five design steps.
This paper studies the impact of current harmonics on the synchronous reluctance machine's average torque and torque ripple. The electromagnetic model of a general m-phase synchronous reluctance machine which integrates the inductance and current harmonics is developed. This model shows that there exist two mechanisms that generate an average torque with a non-zero average value: the proper contribution of the current harmonics and the interaction between them. This model is then used in the case of a 2-phase synchronous reluctance machine with a common transversally laminated anisotropic rotor. This machine design shows negligible inductance harmonics with respect to its fundamental value. Therefore, it has been found that the interaction between the 3rd and 5th current harmonics generates a torque equivalent to the torque generated by the fundamental current component. A locus of the current harmonic components that deliver a constant torque is determined. Furthermore, we have found that, on this locus, the machine torque ripple decreases significantly. Experimental data validate the developed theoretical work and show that at the same torque, the torque ripple is reduced from 20% to 4%.
New zeroth-order resonators (ZORs) are utilized as parasitic elements to enhance a microstrip antenna's bandwidth. By utilizing mushroom T/L shaped resonators, extra resonances are generated. Then, by merging the resonances of the microstrip antenna and the T/L shaped resonators, a wideband antenna is obtained to cover the 5.15-5.35 GHz wireless local area network (WLAN) band. As the ZORs are embedded in the patch of the microstrip antenna, the usages of the parasitic elements do not increase the antenna size. Moreover, as one ZOR resonance is lower than the microstrip patch resonance, a compact antenna is realized. The patch size is decreased from 0.27λc×0.42λc×0.027λc of the reference microstrip antenna (RMA) to 0.25λc×0.40λc×0.026λc of the proposed ZOR based microstrip antenna, where λc is the wavelength of their corresponding lower cutoff frequencies. The proposed antenna was fabricated and measured. The simulated and measured -10 dB impedance bands of the proposed antenna are 5.06-5.40 GHz and 5.07-5.42 GHz, respectively. And, its bandwidth increases 70% compared to the RMA. The simulated and measured patterns are stable in the whole operating band. The gains of 4.73 dBi and 4.24 dBi are measured at the ZOR modes, and 7.88 dBi is measured at the microstrip patch mode.
This paper considers an ideal planar transformer wherein only the electromagnetic parasitics (stray capacitive and leakage inductance) arising out of the transformer geometry are taken into account, assuming lossless conditions. A suitable electrically equivalent circuit model for the planar transformer is used to analyze its frequency and power transfer characteristics; this model was validated by a three dimensional electromagnetic simulation of the planar transformer structure in FEKO electromagnetic simulation software. The effect of dielectric thickness on the bandwidth of the transformer has been analyzed based on the premise that the inherent stray capacitance and leakage inductance elements would affect the power transfer characteristics of the transformer. It has been found that the dielectric thickness of a planar transformer can be optimized so as to maximize the frequency bandwidth. It is also shown that the bandwidth is found to be sensitive to the thickness of the dielectric beyond the optimum thickness threshold topt. Convenient closed form analytic expressions for the optimum dielectric thickness and the resultant maximum bandwidth are derived and presented. It is argued that these results can be readily used to benefit the design of air-core PCB/Planar transformers.
A compact ultra-wideband (UWB) antenna with simple structure is presented. To achieve UWB performance with a compact size, two open ended rounded inverted L-shaped slots are etched on the square ground plane. Moreover, further bandwidth enhancement is obtained by cutting a bevel on the asymmetrical radiating patch. The antenna is fed by a 50 Ω microstrip line and has a small size of 28 × 28 × 1.6 mm3. The simulation time- and frequency-domain results obtained from HFSS simulator package are verified by experimental measurements. Both simulated and measured results show that the antenna can provide a wide impedance bandwidth of more than 129% from 2.7 to 12.55 GHz with -10-dB reflection coefficient. Besides, it is shown that by introducing several antenna designs, the impedance bandwidth can be enhanced from 58% to 129%. The effects of the key design parameters on the antenna impedance bandwidth are also investigated and discussed. Measured results for the reflection coefficient, far-field radiation patterns, radiation efficiency, gain, and group delay of the designed antenna over the UWB spectrum are presented and discussed. Measured data show good concordance with the numerical results. Also, the fidelity factor is calculated in both E- and H-plane by using CST Microwave Studio. The obtained results in both time- and frequency-domain indicate that the antenna is a good option for UWB applications.
А rigorous approach to study the fast H-waves which propagate across an infinite double comb array (IDCA) is proposed. It is based on the Floquet theorem combined with the advanced moment method (Galerkin) scheme in which the basis explicitly satisfies the edge conditions at the rectangular wedge. An exhaustive analysis of the regular and singular modes of the IDCA is made. Normalized critical wave numbers and modal fields are investigated in terms of geometrical parameters. Coupling effects between different IDCA modes are found. For the singular modes a new analytical formula for the critical normalized wave numbers is obtained.
In this paper, a novel CPW-fed triple band metamaterial inspired antenna with modified ground plane is presented. The metamaterial inspired structures such as split ring resonator (SRR) and non bianisotropic complementary split ring resonator (NBCSRR) are embeded in this antenna for triple band operation. The proposed antenna with a compact size of 25 x 31.7 x 1.6 mm3 is fabricated and tested. The antenna with good radiation characteristics is suitable for WIMAX, C band and WLAN applications The simulated and measured results are discussed and are in good agreement with each other.
In this paper, we propose a novel architecture of full-duplex millimeter-wave radio-over-fiber (RoF) system based on polarization division multiplexing (PDM) and wavelength division multiplexing (WDM) technology. In our scheme, the light waves for downlink and uplink transmission are provided by the same laser, which realize the source-free base station (BS) and multi-services transfer for next generation wireless access network. Since the uplink optical carrier is Y-polarized light wave which does not bear the downlink signal, no cross-talk from the downlink contaminates the uplink signal. At the BS, it is detected by a high-speed photoelectric diode (PD) to generate a 15 GHz intermediate frequency (IF) and a 63 GHz radio frequency (RF) signal. This reduces the system complexity and cost. The simulation with 2.5 Gbps NRZ signal transmission exhibits good performance both at 15 GHz (Ku-band) and 63 GHz (V-band).
Current phones include more metal than earlier, which deteriorates the performance of antennas. This paper presents the first complete antenna set designed for a modern handset with a full metal back cover. 4G, Wi-Fi, and GPS antennas are integrated into the metallic side frame of the device in a realistic model. The designed antennas are either capacitive coupling elements with reactive loads or slot antennas. Fixed matching circuits are used to improve total efficiency. The passive implementation enables the use of carrier aggregation (CA) to increase the data rates, and includes also the multiple-input multiple-output (MIMO) operation for 4G and Wi-Fi. The designed antennas cover frequency bands 704--960 MHz, 1.56--1.61 GHz, 1.71--2.69 GHz, 2.4--2.484 GHz, and 5.15--5.875 GHz, producing in measurements a good agreement with simulation results.
The output power of antennas is an important factor affecting the radiation performance of umbrella antenna arrays. Considering the power limit of very-low-frequency (VLF) umbrella arrays and the uncontrollable directivity, we propose a novel method for the spatial power-combining (SPC) of VLF umbrella arrays. Using multiple groups of feeders, the problem of phase shifting of the signals can be solved for VLF arrays. In the high-frequency portion of the VLF range (25-30 kHz), this novel method can improve the efficiency of VLF arrays by 26% in the special directivity. A model of a trideco-tower umbrella antenna array is established in the FEKO simulation software. The simulation results show that, compared with the in-phase feeding, the VLF transmitting antenna array forms the main beam in all directions. The array gain of the umbrella phased array in the 0° (180°) beam position is larger than 1.1 dB. The front-to-back ratio of the arrays is 3.7 dB. Compared with the in-phase feed mode, the directivity of the phased array enhances and the efficiency increases markedly. The simulation results demonstrate the effectiveness of the proposed method.
This paper presents designs of novel E-plane spiro meander line uniplanar compact electromagnetic bandgap (E-SMLUC-EBG) and H-plane spiro meander line uniplanar compact electromagnetic bandgap (H-SMLUC-EBG) structures. The proposed EBG has been applied in mutual coupling reduction of a dual-element multiple input multiple output (MIMO) antenna system for WLAN by placing an EBG structure between the radiating antennas. Compact size of EBG helps in reducing the edge to edge distance between Antennas that is 0.14λ0 in this case, and it increases the compactness of integrated circuit. We get 19 dB and 11 dB simulated mutual coupling reduction in E-plane and H-plane respectively at 5.8 GHz. Measured isolation improvement of 20.3 dB for E-plane and 14.7 dB for H-plane has been achieved. This coupling reduction is also confirmed by surface current and correlation coefficient plots. The four-element (2×2) MIMO antenna system with proposed EBG is also simulated.
The salient individual properties of BaFe12O19, MWCNT, and PANI show promise in exhibiting excellent electromagnetic interference (EMI) shielding when they are combined. This research work focuses on developing a composite consisting of all three materials through a simple polymerization process and then evaluating its potential EMI shielding behaviour through electromagnetic measurements. The composite formation was morphologically and structurally verified through XRD, FTIR and FESEM measurements. The presence of main functional groups characteristic to PANI in the composite samples as shown by its FTIR spectra indicates its successful preparation through this method while FESEM micrographs show the random distribution of the composite constituents. The composite is conductive in nature with values reaching as high as 12.43 S/m for the composite with the highest MWCNT wt% (BPM_1_3_25). Electromagnetic measurements done at the X-band show promising EMI shielding behaviour in all prepared composites. The overall highest SEA values are shown by sample BPM_1_3_25 with a minimum shielding value of 65 dB throughout the whole frequency band, far exceeding that of pure MWCNT.
This paper illustrates how inverse source problems are aected by certain symmetry and support priors concerning the source space. The study is developed for a prototype conguration where the field radiated by square integrable strip sources is observed in far-zone. Three symmetry priors are considered: the source is a priori known to be a real or Hermitian or even (resp. odd) function. Instead, as spatial priors we assume that the source support consists of a single or multiple disjoint domains. The role of the aforementioned priors is assessed against some metrics commonly used to characterise inverse source problems such as the number of degrees of freedom, the point-spread function and the ``information content'' measured through the Kolmogorov entropy.
A MIMO/Diversity antenna with triple notch characteristics is proposed in this article. The proposed antenna has triple notches in the WiMAX band (3.3-3.6 GHz), WLAN band (5-6 GHz), and X-band satellite communication (7.2-8.4 GHz) band. Defected Ground Compact Electromagnetic Band Gap (DG-CEBG) is a design used to accomplish band notches. Defected ground planes are utilised so as to achieve compactness in conventional EBG structures. The proposed WiMAX band, WLAN band, and X-band satellite communication band DG-CEBG structures show a compactness of around 46%, 50%, and 48%, respectively, over a conventional EBG structure. In these structures, decoupling strips and a slotted ground plane are used to enhance the isolation between two closely spaced UWB monopoles. The individual monopoles are 90° angularly separated with a stepped structure which helps to reduce mutual coupling and also contributes towards impedance matching by increasing the current path length. |S21| or mutual coupling is found to be less than 15 dB over the whole UWB frequency range. The Envelope Correlation Coefficient (≤0.5) is within the acceptable limits over the whole UWB frequency range. Notched frequency depends on the parameters of DG-CEBG structures; when there is a change in these parameters notch frequency is also changed. A low cost FR-4 substrate with thickness (h) = 1.6 mm, permittivity (ɛ) = 4.4 and loss tangent (δ) = 0.02 is used for the proposed antenna, and it has a compact size of 58×45×1.6 mm3.
A novel design of Meandered Coplanar waveguide (CPW) fed CSRR loaded multiband antenna is presented in this paper. A compact triple band antenna is designed by etching CSRR slots on the radiating element. The proposed antenna shows good performance at all resonant frequencies. The simulation results are discussed and compared with the measured ones. The effects of CSRR loading on the radiating element are explained. Parametric studies are carried out and explained in detail. The proposed antenna is fabricated and measured, and the results are compared with the simulated ones. CSRR permittivity characteristics are explained to validate the results. The proposed antenna can be used for C-band, Wireless Local Area Network (WLAN) and International Telecommunications Union (ITU) applications.
Matching networks for dual-band power amplifiers typically rely on complex, non-general techniques, which either use switches or result in large and lossy matching networks. In this work, mathematical optimization is employed to design the matching networks for multi-band power amplifiers. The theory of continuous modes is utilized together with accurate models for the device package to define the required impedance terminations theoretically thus allowing mathematical optimization to be used for the design. This technique depends on neither the network architecture nor the number of frequency bands. Therefore, simple and compact multi-band matching networks can be achieved. As proof of concept, a triple-band amplifier at 0.8, 1.8, and 2.4 GHz has been designed using the proposed method. The fabricated amplifier demonstrates maximum power added efficiencies of 70%, 60%, and 58% and output powers of 40 dBm, 41 dBm and 40 dBm for the three frequency bands, respectively. The presented design approach is highly suitable for the next generation of wireless systems.