This paper introduces and validates a compact two-dimensional Electromagnetic Bandgap (EBG) structure for the improvement of signal integrity (SI) and power integrity(PI) by suppressing Simultaneous Switching Noise (SSN). SSN bandwidth can be increased by using the proposed T bridge compact planar structure. The proposed structure is simulated using Ansys HFSS Software. Simulated and measured results by Vector Network Analyzer provide 3.13 GHz to 11.40 GHz frequency bandgap with good mitigation of SSN at -30 dB noise suppression reference. It will almost cover S, C, and X bands from electromagnetic frequency spectrum. This will be useful for satellite and terrestrial communication and radar communication applications. The proposed structure analyzes signal integrity issues using eye diagram in MATLAB and power integrity in HFSS with input impedance respectively. The main purpose of this work is to provide a compact structure to improve signal and power integrity by the suppression of power/ground noise. Comparative study is also performed with the proposed structure and reference board with similar dimensions.
This work proposes a novel probe-fed circular patch antenna which has been fractaled and reconfigured to deliver enhanced performance. The circular ground plane is made defected using Cantor-square fractal geometry which reduces the cross-polarization level by about 12 dB. Further, by appropriate positioning of a PIN diode switch in the ground slot, the fractal Circular Microstrip Patch Antenna (CMPA) is enabled to achieve frequency reconfiguration. A prototype of the proposed antenna is fabricated and tested for the assessment of various parameters. The proposed fractal reconfigurable antenna has a peak gain well above 6 dB, high radiation efficiency, and a maximum bandwidth of about 700 MHz in the X-band (8-12 GHz). The present work aims to focus on the huge potential of fractal reconfigurable antennas in modern dynamic wireless communication systems.
For the sake of decoupling the six-pole radial active magnetic bearing (AMB) with mutual coupling of two degrees of freedom, nonlinear and unstable disturbance, a hybrid active disturbance rejection control strategy based on improved genetic algorithm (HADRC-IGA) is proposed. Firstly, the configuration, magnetic circuit and suspension force model of the six-pole radial AMB are explained and established. Secondly, the HADRC-IGA is designed which is improved on the linear active disturbance rejection control (LADRC). Thirdly, the simulation is carried out, which shows that the capacity of resisting disturbance and the decoupling efficiency of two degrees of freedom of the HADRC-IGA are better than that of conventional LADRC. Finally, the experimental platform is constructed, and the experiments are conducted, which verify the performance of the proposed decoupled control system.
Amorphous alloy transformers (AMDT) have become the mainstream of energy-saving and environmentally friendly distribution transformers, but the problem of environmental pollution caused by their noise has become more prominent. The high magnetostriction of amorphous alloy strip and its sensitivity to stress are the main reasons for the vibration of AMDT core. Accurate calculation of the overall core vibration of transformers is the key issues in transformer noise research. This paper studies the vibration of amorphous alloy transformers under operating conditions, and establishes a three-dimensional magnetic-mechanical coupling model considering the magnetostrictive effect of the power transformer core, and the magnetic field distribution and core vibration displacement of the dry-type transformer under no-load conditions are calculated by finite element method. Combined with experiments, the mechanism of vibration generation of amorphous alloy transformer core is studied, and an iron core vibration prediction calculation based on electromagnetic field coupling analysis is proposed. The research results not only have important academic value for exploring the vibration mechanism and noise suppression mechanism of amorphous alloy transformers, but also have important significance for ensuring their efficient operation.
A novel Variable Inclination Continuous Transverse Stub (VICTS) antenna element and array model is proposed in this paper. The bandwidth and gain of the element are increased by adopting a linear-gradient stub, matching structure and rectangular grating slow-wave structure (SWS). A circular array can be obtained by arranging antenna units of different lengths linearly. The array antenna uses a bow-parabolic box antenna as the line source generator (LSG) and utilizes a double-layer transition waveguide structure to realize the propagation of planar wave. Finally, a wide range of beam scanning in the elevation plane was achieved. The results of the simulation and antenna prototype test are in good agreement. Showing the impedance matching characteristics of the antenna unit and array meets the engineering requirements in the range of 12~16 GHz. The maximum gain of the antenna array is 34.3 dBi, and the maximum 3 dB beamwidth is less than 10°. It is confirmed that the designed antenna has the characteristics of high gain, narrow beam, and low profile, and realizes two-dimensional beam scanning in the range of 6~79° in the elevation plane, which meets the requirements of the Satellite Communications On-the-Move system (SOTM).
This paper theoretically describes a new concept of passive contactless concentric magnetic gear, which, unlike the existing ones, does not use any separate modulator structure, and instead, a set of strength modulated permanent magnet pole pieces are introduced on the outer permanent magnet rotor structure. Mathematical analysis shows that stable operation in this proposed system is possible with any specific gear ratio, dependent on the number of pole pieces and on the choice of modulation constant of the pole strength variation. The system described is simpler because of the absence of separate modulator structure. The concept is new, leads to less parts count, and hence deserves consideration due to its simplicity. A simple simulation study result is also included at the end, which confirms the presented theory. The main contribution of the paper is the introduction of a new concept for designing magnetic gears using fewer physical components and showing that it is a viable design and able to produce a tangible toque at a particular gear ratio. In addition, the mathematical theory in the paper leads to interesting new results indicated in the design section of the paper, which have not been seen in the literature known to the author.
An innovative methodology for the design of dual-band microstrip monopole antennas is presented in this work. It leverages on the unconventional modeling of the radiator shape based on the perturbed Minkowski fractal in order to fit arbitrarily-defined resonances. A System-by-Design (SbD) technique is exploited to solve the arising global optimization problem with high computational efficiency. Representative benchmarks are reported to assess the effectiveness, reliability, and efficiency of the proposed synthesis approach.
The computation of the fields scattered by a dielectric sphere illuminated by a plane wave and the evaluation of the resultant optical forces is a classical problem that can be analytically solved using Mie theory. Whereas extending said formulation to arbitrary incident fields does not pose any conceptual difficulty, the actual computation of the scattering coefficients and force components substantially grows in complexity as soon as interactions beyond the electric dipole arise. By formulating an equivalent electromagnetic problem, we derive a set of computationally efficient formulas for the evaluation of scattering and optical forces exerted by arbitrary incident fields upon dielectric spheres in the Mie regime. As opposed to force calculations by direct integration of the Maxwell’s Stress Tensor, the present formulation relies on a set of universal interaction coefficients that do not require any problem-specific integration and can therefore be all precomputed and tabulated. The proposed methods can be easily integrated with the T-Matrix method to calculate forces on non-spherical dielectric objects.
In this paper a multifunctional patch antenna loaded with near zero index refraction metamaterial (NZIM) is presented. This multifunctional antenna operates at 5.8 GHz and provides high gain and beam steering capability. The proposed configuration comprises a patch antenna placed below an NZIM superstrate. The rectangular microstrip antenna is used as a radiation source to demonstrate the performance of this design. The NZIM superstrate, which behaves as an NZIM, based on 9×9 resonating unit cells of split ring resonators (SRRs), allows gathering radiated waves from the antenna and collimating them toward the superstrate's normal direction, which results in gain enhancement. The beam-steering in the E-plane is obtained by slowly tilting the NZIM over the patch antenna. The main characteristics of the antenna placed near the NZIM superstrate are studied numerically and experimentally to successfully demonstrate this dual function feature. It is found experimentally that the gain enhancement of 8 dB with improved directivity and radiation efficiency are obtained in comparison with the antenna without the NZIM metasurface. In addition, we were also able to steer the direction of the main beam just by tilting the NZIM superstrate from -20° to 20° with a gain variation of 5 dB and without changing the whole dimension of the structure.
The study investigates the mathematical background of the method of auxiliary sources (MAS) employed in electromagnetic diffraction. Here, the mathematical formulation is developed for E-polarized plane wave diffraction by perfectly conducting two-dimensional objects of arbitrary smooth shape, and the comparison with an analytical and a numerical approach is provided in the numerical part. The results reveal a quite high accuracy among all methods. The importance of the study is to develop the complete mathematical background of MAS for two-dimensional TM-polarized electromagnetic scattering problems by conducting objects. Different from the method of moments (MoM) and other integral equation approaches in electromagnetic scattering problems, here the integral equation resulting from the boundary condition on the scatterer is solved by expanding the current density as orthonormalized Hankel's function with the argument of the distance between the scatterer actual and auxiliary surfaces. The approach can be summarized by that first the sources are shifted inside the scatterer and second, the boundary condition is employed as the total tangential electric field is zero on the surface and inside the object. Then, such expansion leads to eliminating the singularity problems by shifting the sources from the actual surface.
A study of the impact of mutual coupling effects in a co-located multiple input multiple output (MIMO) radar system is presented. Predicted and measured results corroborate that the active reflection coecient (ARC) and beampatterns are impacted by the excitation of each sub-array, the geometric configuration, and their polarization. A uniform linear array (ULA) and a uniform planar array (UPA) layouts are considered. The excitations used in the study are linear frequency modulation (LFM) and Doppler division multiple access (DDMA). A thorough analysis is presented to understand the effects these parameters have on the ARC and on the beampatterns of the radar system.
In this paper, a polarization-insensitive and dual-band Electromagnetic Induced Transparency-Like (EIT-Like) metamaterial is proposed, which is made of a cross-shaped graphene structure. Due to the mutual coupling between intralayer and interlayer, two high transmission windows can be obtained in different frequency bands. The sensibilities located at the two transmission peaks are calculated as 0.385 THz/RIU and 0.979 THz/RIU respectively. In addition, the maximum group index of 174.5 is obtained. By adjusting the Fermi level of graphene, the transmission and group index could be modulated independently. The characteristics make the proposed metamaterials possess the potential as a tool for biological detection, slow light technology, and filters in THz region.
This manuscript refers to the electromagnetic scattering problem involving plane waves at skew incidence with respect to the edge of a right-angled metallic wedge having one face coated by a double negative metamaterial sheet. Its presence in the propagation scenario is properly accounted at high frequencies by considering the geometrical optics response of the structure and the diffraction contribution arising from the edge of the wedge. In particular, the reflection coefficients related to the coated surface are determined for both the polarizations by using the equivalent transmission line circuit, whereas the diffraction coefficients are obtained by applying the uniform asymptotic physical optics approach. This last is based on electric and magnetic equivalent surface currents under the physical optics approximation and permits to evaluate the diffraction contribution in the context of the uniform geometrical theory of diffraction. The resulting approximate solution is characterized by the same simplicity of use of the heuristic solutions and provides reliable field values as confirmed by the numerical tests carried out by a full-wave commercial software.
A novel ultra-broadband Polarization Rotation (PR) Reflective Surface (PRRS) is presented, which can reflect the linearly polarized incident wave in orthogonal polarization state. The proposed PRRS consists of a periodic array of double split ring patches printed on a substrate, which is backed by a metallic ground. A PRRS composed of circular split ring units can realize polarization rotation in two wide frequency bands. When two circular split rings with gradual radii are arranged concentrically, an ultra-broadband polarized rotation will be obtained. This paper explains the mechanism of polarization rotation and the mechanism of Radar Cross Section (RCS) reduction and studies the influence of structural parameters on the polarization rotation frequency band. Simulation results show that a 101.6% PR bandwidth is achieved. Meanwhile, by arranging the unit cells of the PRRS in four orthogonal directions, the monostatic RCS reduction band ranges from 8 GHz to 21.8 GHz (or 92.6%) for arbitrary polarization of the incident wave.
Flat band systems have attracted considerable interest in different branches of physics, providing a flexible platform for exploring the fundamental properties of flat bands. Flat band states in the continuum (FBICs) can be derived from a one-dimensional lattice loaded with electromagnetically induced transparency (EIT) medium. The appearance of the strong slow light phenomena has been found under the conditions of EIT and flat band. Flat bands provide a key ingredient in designing dispersionless wave excitations. Different from the conventional flat band states, the FBIC is delocalized state and has robustness, providing us an efficient way to achieve large delay slow light. These results may provide inspiration for exploring fundamental phenomena arising from FBICs.
The linear sampling method (LSM) is a very popular method for determining the boundary of an object from the scattered field. However, there are instances where LSM provides the convex hull of the boundary rather than the true boundary. There are two common generalizations to LSM: the Generalized Linear Sampling Method (GLSM) and the Multipoles-based Linear Sampling Method (MLSM). In this paper, the ability of GLSM and MLSM to overcome some of the deficiencies of LSM are investigated. It is found that GLSM may be ideal for imaging thin features of scatterers and that MLSM can provide an improvement over LSM in a more general sense. GLSM may also require user input to adjust the indicator function whereas MLSM does not appear to rely as much on indicator function adjustments for adequate results.
Uncertainty analysis is one of the hot research issues in the field of computational electromagnetics in the past five years. The Method of Moments is a non-embedded uncertainty analysis method with relatively high computational efficiency, and has the unique advantage of not being affected by the ``curse of dimensionality''. However, when the nonlinearity between the simulation input and output is large, the accuracy of the Method of Moments is not ideal, which severely limits its application in the field of computational electromagnetics. In this paper, an improved strategy based on the central clustering algorithm is proposed to improve the expected value prediction results of the Method of Moments, thereby improving the accuracy of the overall uncertainty analysis. At the same time, the co-simulation technology of MATLAB software and COMSOL software is completed, then the accuracy and computational efficiency of the proposed algorithm in this paper are quantitatively verified. In this case, the clustering Method of Moments is effectively popularized in commercial electromagnetic simulation software.
A high-performance photonic crystal fibre-based alcohol biosensor is introduced for the selective test analytes: propanol, butanol, and pentanol operating at wavelengths ranging from 0.8 to 2.0 µm. The performance of the proposed sensor with the architecture of octagonal-shaped cladding air holes in two rings surrounding a single infiltrated hexagonal core hole produces high relative sensitivities, low confinement losses, small effective areas, and high nonlinear coefficients. At the optimal 1.4 µm wavelength, propanol, butanol, and pentanol assessed relative sensitivities of 93.10%, 93.95%, and 94.70%, respectively, and confinement losses of 6.38 × 10-10 dB/m for propanol, 2.12 × 10-10 dB/m for butanol and 1.04 × 10-10 dB/m for pentanol. Moreover, the nonlinear coefficients achieved results of 2446 W-1km-1 for propanol, 2703 W-1km-1 for butanol, and 2869 W-1km-1 for pentanol, at the optimum wavelength. These outstanding results of optical properties prove the potential and capabilities for practical sensing and optical communication applications.
As a noninvasive imaging technique for the interior of objects, Electrical Impedance Tomography (EIT) is widely used in many fields of biomedicine. Sparse reconstruction algorithms have made major breakthroughs in the field of image reconstruction in recent years. The K-SVD algorithm is an adaptive dictionary signal sparse representation algorithm, which could improve the reconstruction accuracy. However, the parameters in the K-SVD algorithm are fixed, which cannot match all the measurement data of EIT very well. Moreover, the K-SVD algorithm adopts a greedy algorithm in the sparse coding stage, which has high computational complexity. In this study, an electrical impedance sparse imaging method based on DK-SVD (deep k-singular value decomposition) was designed. It provides the corresponding optimal model parameters for each set of measurement data through the method of multi-layer perceptron (MLP) network training, thereby improving the imaging quality. At the same time, the iterative soft threshold algorithm (ISTA) is used in the sparse coding stage to improve the convergence speed. The reconstruction results show that compared with the K-SVD algorithm and Total Variation (TV) algorithm, the reconstruction error of the DK-SVD method is smaller, and the irregular and sharp inclusions can be accurately reconstructed. Image artifacts are also greatly reduced.
A novel quad-band bandpass filter (BPF) consisting of two deformed W-shaped microstrip Stepped-Impedance Resonators (SIRs) with different dimensions is proposed. The W-shaped SIRs are miniaturized from E-shaped SIRs, and each one of the SIRs generates two passbands, and thus four passbands centered at 3.18 GHz, 4.51 GHz, 5.46 GHz, and 8.43 GHz with fractional bandwidth of 6.7%, 9.1%, 8.4%, and 8.2% were obtained. Compared with the basic SIR structures and E-shaped structures, the effective area of the miniaturized SIR is reduced by more than 60% and 20%, respectively. The operating frequency bands can be determined by switching the diodes that are connected to the cross coupling lines of the two SIRs. The improved design can be used for 5G and other applications.