A miniaturized trans-directional (TRD) coupled line coupler comprises series inductors and capacitor loaded coupled lines is proposed in the paper. Series inductors are added to the periodically loaded coupled lines for further miniaturization of volume. A novel equivalent circuit is presented and theoretically analyzed. Test circuits for the miniaturized and conventional 3-dB TRD couplers were designed to operate at 1.6 GHz and fabricated using printed circuit board (PCB) technology. Samples have been measured, and comparisons in terms of volume, schematic simulation results and measurement results between the miniaturized and conventional 3-dB TRD couplers have been made to validate the proposed structure. Results show that the proposed miniaturized TRD coupler achieves a size reduction of 47.6% compared to the conventional TRD coupler with similar performances.

In this article, a compact ultra-wideband (UWB) planar monopole antenna with the triple notched band is proposed. The antenna consists of a semicircular radiating patch and a modified ground plane with two bevels at upper edge. By etching two round shape slots in radiating patch the notch characteristics are achieved at WiMax band (3.3-3.7 GHz) and WLAN band (5.15-5.875 GHz). In order to realize notch band at X-band downlink satellite communication band (7.1-7.76 GHz) a pair of rotated V-shape slot are etched on the ground plane. The measured operating impedance bandwidth of proposed antenna ranges from 2.9 to 10.9 GHz having return loss less than 10 dB with triple notched bands. The proposed antenna exhibits a nearly omnidirectional radiation pattern in the H-plane, and a dipole-like radiation pattern in the E-plane for the ultra-wideband. The effects of each individual slot on band-notch characteristics are also investigated. The measured gain of the proposed triple band notched antenna is relatively stable across the operating frequency band except notched bands and thereby making the proposed antenna suitable for practical UWB applications. Proposed antenna has a compact size of 27x25 mm².

This paper proposes a novel signal processing approach to thermal non-destructive testing by incorporating Gaussian window function onto the linear frequency modulated incident heat flux to achieve better pulse compression properties. The present work highlights a finite element analysis based modeling and simulation technique in order to test the capabilities of the proposed windowing scheme over the conventional frequency modulated thermal wave imaging method. It is shown that by using Gaussian weighted chirp thermal stimulus, high depth resolution can be achieved.

Partial Discharge detection techniques strive to ensure a safe and reliable power network by preventing power failure. In this work, electromagnetic sensing of partial discharge, in air-insulated medium voltage switchgear (Type D24-121114 of Driescher) is considered. The partial discharges are approximated by Gaussian sources. A versatile broadband sensor for detecting two major types of partial discharge was designed and optimized. The antenna has low return loss and high gain over the frequency band of corona discharge, 0.75-0.9 GHz and dry band arching, 1.25-1.4 GHz. The horn antenna is incorporated into the medium voltage switchgear for detecting partial discharges. The analysis of the electromagnetic field distributions generated by partial discharges in switchgear is coupled with the sensing efficiency of the horn antenna. The results indicate a good correlation between the intensity, location and frequency band of partial discharge and their sensing. This study provides the foundation for a dual band detection system of partial discharge in switchgear systems.

A broadband circularly polarized (CP) slot antenna array fed by a coplanar waveguide (CPW) is proposed. A fan-shaped feed line and three L-shaped grounded strips are embedded in the square slot antenna element to enlarge the bandwidth. Simulated results show that the antenna element can obtain a wide impedance bandwidth with -10 dB reflection coefficient covering 1.7-6.3 GHz (about 115% relative bandwidth) and 3 dB axial ratio (AR) bandwidth covering 2.6-5.2 GHz (about 66%). Using four elements with sequential phase feed, the measured impedance bandwidth and axial ratio bandwidth of the antenna array can be enhanced to 105% (1.65-5.35 GHz) and 71.3% (2.3-4.85 GHz), respectively. Good radiation characteristics with the peak gain of 10.8 dBic over the operating band can be obtained.

Allowing photons to bear mass, the electric and magnetic fields of a steadily moving charge are not no longer perpendicular to each other, as anticipated from Biot-Savart law. The electric and magnetic fields of such a particle depend on the gauge potentials, φ and A. The orthogonality relations of the particle fields and the direction of motion depend on the mass of the photon. The non-relativistic correction to the particle fields was found to be related to the Lorenz gauge condition. It is shown that the existence of magnetic monopoles inside matter is inevitable when magnetic filed is applied in a conductor. Their existence is a manifestation of the massive nature of the photon inside matter. Neither electric nor magnetic current is separately conserved for photons, but their sum is. Massive photons are found to produce electric and magnetic fields. A force proportional to the square of the current is found to act along the wire, F = 1/2μ₀I², where μ₀ is vacuum permeability.

In this study a new analytical formulation for electromagnetic wave scattering from rough boundaries interfacing inhomogeneous media is presented based on the first-order approximation of the small perturbation method. First, we considered a scattering problem for a single rough boundary embedded in a piecewise continuously layered medium. As a key step, we introduced auxiliary wave propagation problems that are aimed to link reflection and transmission coefficients in the layered media with particular solutions of one-dimensional wave equations at the mean level of the rough interface. This approach enabled us to express the final solution in a closed form avoiding a prior discretization of the inhomogeneous medium. Second, we naturally extended the obtained solution to an arbitrary number of rough interfaces separating continuously layered media. As a validation step, we demonstrated that available solutions in the literature represent special cases of our general solution. Furthermore, we showed that our numerical results agree well with published data. Finally, as a particular special case, we presented a formulation for scattering from inhomogeneous snow-covered sea ice when the dominant scattering occurs at the snow-ice and air-snow interfaces.

This paper presents a novel miniaturized multi-evanescent-mode resonator. The resonator is achieved with a coaxial cavity. This coaxial cavity essentially has a direct short connection at one end and is connected with several lumped capacitances at the other end. The key technology of the resonator is the usage of multiple evanescent-modes of TM (transverse magnetic wave) modes. Due to the combined effects of the evanescent mode and multiple modes, the size of the resonator is greatly reduced. In this paper, the theory of resonator is discussed in detail. To verify the correctness of operation, the resonator is used in experimental measurements conducted to realize a third-order band-pass filter based on SIW (substrate-integrated waveguide) technology. The measured results are found to agree with the theoretical values.

A new design of dual-port monopole-slot-like microstrip active integrated antenna (AIA) is presented and discussed in this paper. The primary designed passive antenna is capable of supporting two different WLAN bands at 2.4-2.84 GHz and 5.15-5.35 GHz due to its dual-port structure. In order to reduce the transmission coefficient between the two ports of antenna a coupling sleeve-arm and an inverted T-shaped slot are utilized on the ground plane of antenna each beneath one of the corresponding feed-lines which act as filtering structures at desirable frequencies. The proposed passive dual-port antenna is integrated with a power amplifier (PA) and a low noise amplifier forming a dual-port microstrip AIA which can be used as a full-duplex transceiver at its operating WLAN frequency bands. The measured results for both passive and active antennas show that the designed antennas have proper radiation characteristics at their desired operation frequencies. The fabricated passive antenna exhibits dual-band performance at 2-3.42 GHz and 4.5-5.6 GHz while the fabricated AIA covers 2.31-2.82 GHz (at PA port) and 4.45-5.5 GHz (at LNA Port) with 13 dB and 9 dB gain level improvement respectively.

In this paper, we propose the design of multilayer frequency selective surfaces (FSS) waveguide band-pass filters (WBPF). The WBPFs are designed to operate at two different frequency channels, respectively 71-76 GHz (Rx) and 81-86 GHz (Tx). The cross section surface of the FSS is imposed by the WR12 waveguide rectangular section's dimensions. The WBPFs are inserted symmetrically in a T-junction waveguide to design a compact diplexer. This is a basic component developed for an efficient integration in the future E-band millimeter-wave transceiver. The multilayer FSS structure uses only non-resonant sub-wavelength unit cell elements; metallic patch and slot. To reach high channel isolation (≈ 70 dB) a seven order filter was required. Hence, each filter is composed of 13 capacitive and inductive metallic FSS spaced by 12 ultra-thin dielectric substrate layers. The dielectric material is Rogers Ultralam 3850 (Liquid Crystalline Polymer; LCP circuit material). The filter's overall thickness is < λ/4. The numerical studies have been performed using finite element method simulator (HFSS) and CST Studio Suites Tools. The experimental validation has been also done in the X band frequency by developing a fifth order FSS WBPF. Good agreements between simulated and measured results are obtained.

In literature, heuristic algorithms have been successfully applied to a number of electromagnetic problems. The associated cost functions are commonly linked to full-wave analysis, leading to complexity and high computational expense. Artificial Neural Network is one of the most effective biological inspired techniques. In this article, an efficient surrogate model is trained to replace the full-wave analysis in optimizing the bandwidth of microstrip antenna. The numerical comparison between ANN substitution model and full-wave characterization shows significant improvements in time convergence and computational cost. To verify the robustness of this approach, all these concepts are integrated into a case study represented by a rectangular ring antenna with proximity-coupled feed antenna.

In this paper, the design and analysis of a compact coplanar waveguide-fed ultra wideband pentagon antenna are presented. To achieve ultra wideband performance, two modifications are introduced. The first one is to remove a small fan angle on each side of the ground plan, and the second one is to modify the sharp of the patch in the width. The optimal dimensions can be achieved by a parametric analysis. The antenna design exhibits a very wide operating bandwidth of 16.7 GHz with a return loss better than 10 dB in the frequency range from 4.46 GHz to 21.14 GHz. The gain of the proposed antenna is 6.3 dBi. This antenna configuration will be useful for UWB indoor application as it is easy to fabricate and integrate with RF circuitry. All simulations in this work were carried out by using the electromagnetic software CST.

A wideband unidirectional bowtie antenna with stable radiation patterns is proposed and investigated. It is fed by a wideband microstrip balun, using a coupling triangular structure to induce more balanced currents. Particularly, the corners of the conventional triangular bowtie dipole are rounded to achieve an impedance BW of 106.9% for |S₁₁| ≤ -10 dB ranging from 1.97 GHz to 6.49 GHz. Additionally, a special small circular reflector between the ground plane and the bowtie dipole is used to stabilize the radiation patterns. The antenna achieves a stable gain of around 9.5 dBi with a little variation of 1.4 dBi and unidirectional radiation patterns over the whole operating band.

The tuning of electromagnetically-induced-transparency-like (EIT-like) phenomenon in metamaterials based on microstrip system is investigated. The tunability of EIT-like effect mainly arises from the controllable elements of varactor diodes loading on the ``dark'' resonators of EIT-like metamaterials. The results show that the frequency range of transparency window of our EIT-like metamaterials can be continuously and reversibly adjusted along with the varying external voltages applied on the varactor diodes. Moreover, the transmittance maximum hardly changes with the shift of transparency window. Such tunable EIT-like metamaterials may be applied in tunable slow-wave filters and switch devices.

Optoelectronic devices triggered by a laser flash and operating in linear switching regime allow the generation of short pulses with small time jitters (2 ps typically). An Ultra Wide Band antenna array combining as many of this photoswitches as antennas has the advantage to increase the radiation power on one hand and to offer the agility of the radiation beam on the other hand obtained by time delay of laser illumination. During the step of antenna design, it becomes important to take into account the photoswitch integration in order to increase the peak power and the frequency band of the generated output signal. This paper presents an equivalent model of photoswitch obtained with the transient solver of CST Microwave Studio coupled within CST Design Studio. The second part of this article is dedicated to the integration of a photoswitch even within the antenna.

A novel compact ultra-wideband (UWB) bandpass filter (BPF) with triple sharply notched bands and wide upper stopband is proposed. The basic UWB BPF is composed of two microstrip interdigital coupled lines and one multiple-mode resonator (MMR). Then, to achieve triple band-notched performance, the proposed triple-mode stepped impedance resonator (TMSIR) is studied and coupled to the interdigital coupled lines of the basic UWB BPF. To validate the design theory, a microstrip UWB BPF with three notched bands respectively centered at 5.2 GHz, 5.8 GHz, and 6.8 GHz is designed and fabricated. Both simulated and experimental results are provided with good agreement.

We present a differential forms inspired discretization for variational finite element analysis of inhomogeneous waveguides. The variational expression of the governing equation involves transverse fields only. The conventional discretization with edge elements yields an unsolvable generalized eigenvalue problem since one of the sparse matrix is singular. Inspired by the differential forms where the Hodge operator transforms 1-forms to 2-forms, we propose to discretize the electric and magnetic field with curl-conforming basis functions on the primal and dual grid, and discretize the magnetic flux density and electric displacement field with the divergence-conforming basis functions on the primal and dual grid, respectively. The resultant eigenvalue problem is well-conditioned and easy to solve. The proposed scheme is validated by several numerical examples.

In this paper, three different compact circular-ring microstrip patch antenna structures have been proposed. These antennas have been analyzed, investigated and optimized using the CST-MW-simulator. The proposed designs are mainly based on the concept of patch shape reconfiguration while its overall dimensions are kept constant. The objective is to design dual and/or triple broadband antennas resonate within the fourth generation band (4G). The presented antennas are simulated and fabricated on cheaper and lossy FR-4 substrate, and their parameters are measured and compared. The obtained results show that the proposed antenna structures resonate within the 4G frequency band. The operating bandwidths have been varied between 270.0 MHz and 1000.0 MHz (about 4% up to 7% of center frequency). In addition, maximum VSWR value of less than 1.5 has been achieved. The obtained results verify the validity and the benefits of reconfiguring the patch shape. Finally, good agreement has been obtained between simulated and measured parameters.

In this paper, the effect of both uniaxial anisotropy in the substrate and air gap layer on the resonant frequency and bandwidth of circular microstrip patch are investigated. The problem is rigorously formulated based on the spectral domain technic in conjunction with Galerkin approach for computing the resonant frequency, half-power bandwidth, and radiation field of a tunable circular patch antenna which is printed on isotropic or uniaxial anisotropic substrate. The TM set of modes issued from the magnetic wall cavity model theory are used to expand the unknown currents on the patch. Resonant frequency shift due to uniaxial anisotropy is firstly investigated for different anisotropy ratio values of substrate. Then, the effect of inclusion of air gap layer inserted between anisotropic substrate and ground plane on the resonance characteristics is also investigated. The results obtained from this approach are in very good agreement with the experimental results available in the literature.

In this paper we proposed a novel classification system to distinguish among elderly subjects with Alzheimer's disease (AD), mild cognitive impairment (MCI), and normal controls (NC). The method employed the magnetic resonance imaging (MRI) data of 178 subjects consisting of 97 NCs, 57 MCIs, and 24 ADs. First, all these three dimensional (3D) MRI images were preprocessed with atlasregistered normalization. Then, gray matter images were extracted and the 3D images were undersampled. Afterwards, principle component analysis was applied for feature extraction. In total, 20 principal components (PC) were extracted from 3D MRI data using singular value decomposition (SVD) algorithm, and 2 PCs were extracted from additional information (consisting of demographics, clinical examination, and derived anatomic volumes) using alternating least squares (ALS). On the basic of the 22 features, we constructed a kernel support vector machine decision tree (kSVM-DT). The error penalty parameter C and kernel parameter σ were determined by Particle Swarm Optimization (PSO). The weights ω and biases b were still obtained by quadratic programming method. 5-fold cross validation was employed to obtain the out-of-sample estimate. The results show that the proposed kSVM-DT achieves 80% classification accuracy, better than 74% of the method without kernel. Besides, the PSO exceeds the random selection method in choosing the parameters of the classifier. The computation time to predict a new patient is only 0.022s.