The electromagnetic field distributions in the waveguide of a 915 MHz single-mode microwave sintering applicator equipped with a loading pressure system were simulated using a JMAG-Studio program. The disturbance in the magnetic field as well as in electric field was caused by the insertion of the alumina loading pressure system due to reflection effect of alumina. However, the separated magnetic field and electric field maxima can be obtained by adjusting position of the alumina loading pressure system in the waveguide. The simulation results were evaluated by comparison with experimental measurement.

Based on the improvements of both Genetic Algorithm and Particle Swarm Optimization, a novel IGA-edsPSO (Improved Genetic Algorithm-extremum disturbed simple Particle Swarm Optimization) Hybrid algorithm is proposed in this paper. An improved performance of GA is achieved by reducing the array space. By discarding the particle velocity vector in the PSO evolutionary equation, the sPSO (simple PSO) can avoid the problem of slow later convergence velocity and low precision caused by determining the maximal velocity vector factitiously. And the edsPSO can overstep local extremum point more effectively with the help of the extremum disturbed factor. The proposed IGA-edsPSO Hybrid algorithm is used in the design of the sparse arrays with minimum element spacing constraint. Given the array aperture and the number of the array elements, the suppression of the peak sidelobe level (PSLL) with a certain half power beamwidth (HPBW) restriction is implemented with a high efficiency by optimizing the HPBW and PSLL synchronously. The simulation results show that faster convergence velocity (which means less computation time) and lower sidelobe level are obtained using IGA-edsPSO compared to IGA, standard PSO, GA-PSO and GA-sPSO.

Detailed procedure for Green's function derivation of an annular waveguide is presented in this paper for the first time. The proper components of the electromagnetic fields along with their corresponding Green's functions will be derived in a useful and applicable form. Based on the derived Green's functions, proper set of integral equations are derived in a novel general form which their MoM solution will lead to complete slot field distribution in the annular waveguide slot antenna (AWSA). The proposed theory would be found of high value in circuit modelling and array design of such novel antenna structures in the future.

The rigorous numerical formulation for TE-scattering from a conducting wedge with concaved edge is presented and numerical computations for scattered fields are shown. The radial mode matching technique is used to obtain the scattering field in a series form. The accuracy of the present method is checked with existing solutions of a semi-circular channel and sharp wedge, which are special case of the general geometry of a conducting wedge with concaved edge.

A hybrid method is developed to compute the radiation pattern of antennas on large complex three-dimension carriers. The hybrid method involves computing the radiation fields of the antenna in free space with FEM, characterizing the reflection and diffraction of the carrier to the radiation fields with CRE (Complex Ray Expansion) and UTD (Uniform Theory of Diffraction). The ray technique of SBR using traditional hybrid method is employed by CRE. The shortcomings of the SBR, such as great number of ray trace, distortion and partly shadowing of the rays etc., are overcome by the use of CRE, and the time consuming physical-optics-type integration is replaced by the paraxial approximation of the complex rays. A dipole placed on different carriers are taken as the examples to show the validity of the hybrid method, and the radiation patterns computed by the proposed method are in good agreement with those by FEM. By using the proposed method, the computation of the three dimension radiation pattern of an antenna in a large ship is finished by a PC in 1671.20 seconds.

The diffraction by a terminated, semi-infinite parallelplate waveguide with four-layer material loading is rigorously analyzed for the H-polarized plane wave incidence by means of the Wiener-Hopf technique. Introducing the Fourier transform for the unknown scattered field and applying boundary conditions in the transform domain, the problem is formulated in terms of the simultaneous Wiener-Hopf equations. The Wiener-Hopf equations are solved via the factorization and decomposition procedure together with the use of the edge condition leading to exact and approximate solutions. The scattered field inside and outside the waveguide is evaluated by taking the inverse Fourier transform and applying the saddle point method. Numerical examples on the radar cross section (RCS) are presented for various physical parameters, and the backscattering characteristics of the waveguide are discussed.

Fractals contain an infinite number of scaled copies of a starting geometry. Due to this fundamental property, they offer multiband characteristics and can be used for miniaturization of antenna structures. In this paper, electromagnetic transmission through fractal shaped apertures in an infinite conducting screen has been investigated for a number of fractal geometries like Sierpinski gasket, Sierpinski carpet, Koch curve, Hilbert Curve and Minkowski fractal. Equivalence principle and image theory are applied to obtain an operator equation in terms of equivalent surface magnetic current over the aperture surface. The operator equation is then solved using method of moments (MoM) with the aperture surface modeled using triangular patches. Numerical results are presented in terms of transmission coefficient and transmission cross-section for both parallel and perpendicular polarizations of incident plane wave which show the existence of multiple transmission bands.

Based on the broadside-coupled split-ring resonator (BC-SRR), a tunable left-handed metamaterial (LHM) was proposed in this paper. The two rings of BC-SRR are etched on two separate substrates so that the coupling between the two rings can be adjusted by slightly slip one of the two substrates relative to the other one. Thus, the magnetic resonance frequency of the modified BC-SRR can be tuned. By combining the modified BC-SRR (MBC-SRR) with continuous conducting wires, a tunable LHM can be realized. The tunable LHM can realize both rough and minor tunings by minor slips along and perpendicular to the gap direction of BC-SRR, respectively. The proposed tunable LHM has many potential applications in microwave devices.

A compact ultra-wideband (UWB) monopole antenna with four-band-notched characteristics is introduced in this paper. The proposed antenna can achieve four-band rejection at 3.4, 5.5, 8 and 11 GHz with desired bandwidths only using one novel structure called nested complementary split-ring resonator (CSRR) which is etched inside the ground plane. This method used to obtain four-band-notched characteristics is firstly proposed in this paper. The antenna has a small dimension of 35*27mm². The VSWR and radiation patterns of the fabricated antenna are presented, which prove that the designed antenna is a good candidate for various UWB applications.

In this paper, we present an efficient hybrid spatial-spectral formulation of the method of moment (MoM) in conjunction with the Mixed-Potential Integral Equation (MPIE) for planar circuit analysis. This method is based on the decomposition of the Green's functions in two parts: quasi-static in the near field region and the dynamic contribution in the far field region. Using this decomposition of Green's functions, the method of moment matrix entries can be reduced and expressed to a sum of two integrals. The first one is expressed in the spatial field and corresponds to the quasi-static contribution. It is analytically evaluated after a development in Taylor series of the exponential terms in the function to integrate. The integrals expressed in the spectral field and corresponds to the dynamic part have the advantage of being calculated on a finite range and this independently of the choice of the basis and test functions. The integrals expressed in the spectral field are performed by using numerical integration. It is also demonstrated that this hybrid method has accelerated the matrix fill in time by using a Fast Fourier Transform (FFT) algorithm. In order to validate the proposed method, numerical results are presented.

A novel printed monopole antenna for ultra-wideband (UWB) applications is presented, which is composed of wide slot and Y-shaped microstrip feed line with a pair of inverted-L-shaped notches. The prototype with an overall size of 26 mm × 30 mm × 2 mm achieves good impedance matching, constant gain, stable radiation patterns, and a relative impedance bandwidth of 110.6% is achieved, which covers 3.09-10.74 GHz.

A thermal analysis and structure of a ridge single mode waveguide with a metal heater are presented. The steady-state temperature increases linearly and the thermal response becomes slower at the same power consumption, when the under-etched depth in the lower cladding increases. When the upper cladding thickness decreases, the thermal response becomes faster. This shows that a thinner upper cladding and a deeper etching are preferred to achieve a faster thermal response and lower power consumption, respectively. The numerical simulation also shows the power consumption of the present ridge waveguide is almost third of that for conventional one and the response time is half of that of the conventional one.

Models based on fuzzy inference systems (FISs) for calculating the resonant frequency of rectangular microstrip antennas (MSAs) with thin and thick substrates are presented. Two types of FIS models, Mamdani FIS model and Sugeno FIS model, are used to compute the resonant frequency. The parameters of FIS models are determined by using various optimization algorithms. The resonant frequency results predicted by FIS models are in very good agreement with the experimental results available in the literature. When the performances of FIS models are compared with each other, the best result is obtained from the Sugeno FIS model trained by the leastsquares algorithm.

In this paper, frequency selective surfaces (FSSs) are analyzed and designed. The analytical procedure is based on method of moments (MoM). The generalized minimal residual recursive method combined with fast Fourier transform (GMRESR-FFT) is utilized to accelerate the solution of the matrix equation. Our numerical results show that the GMRESR-FFT method can converge at least 3 times faster than the generalized minimal residual fast Fourier transform method (GMRES-FFT). In this paper, the cross dipoles are first used to design the FSS filter with a passband at 300 GHz and a stopband at 450 GHz, and then the Jerusalem cross slots are utilized to avoid grating lobes and improve the bandwidth of FSS. Numerical results demonstrate the validity and efficiency of the presented method.

This paper introduces a planar μ-negative (MNG) metamaterial structure, called double-sided split ring resonator (DSRR), which combines the features of a conventional SRR and a broadside-coupled SRR (BC-SRR) to obtain much better miniaturization at microwave frequencies for a given physical cell size. In this study, electromagnetic transmission characteristics of DSRR, BC-SRR and conventional SRR are investigated in a comparative manner for varying values of substrate parameters which are thickness, the real part of relative permittivity and dielectric loss tangent. Simulation results have shown that magnetic resonance patterns of all these three structures are affected in a similar way from variations in permittivity and in loss tangent. However, changes in substrate thickness affect their resonance characteristics quite differently: In response to decreasing substrate thickness, resonance frequency of the SRR increases slowly while the bandwidth and the depth of its resonance curve do not change much. For the DSRR and BCSRR structures, on the other hand, resonance frequency, half power bandwidth and the depth of resonance curve strongly decrease with decreasing substrate thickness. Among these three structures, all having the same unit cell dimensions, the newly suggested DSRR is found to reach the lowest resonance frequency, hence the smallest electrical size, which is a highly desired property not only for more effective medium approximation but also for miniaturization in RF design. The BC-SRR, on the other hand, provides the largest resonance bandwidth which is almost three times of the resonance bandwidth of the SRR. The bandwidth of the DSRR approaches to that of the BC-SRR as the planar separation between its inner and outer rings increases.

The plane wave diffraction by a terminated, semi-infinite parallel-plate waveguide with four-layer material loading is rigorously analyzed using the Wiener-Hopf technique. Introducing the Fourier transform for the unknown scattered field and applying boundary conditions in the transform domain, the problem is formulated in terms of the simultaneous Wiener-Hopf equations satisfied by the unknown spectral functions. The Wiener-Hopf equations are solved via the factorization and decomposition procedure leading to the exact solution. The scattered field in the real space is evaluated by taking the inverse Fourier transform and using the saddle point method. Representative numerical examples of the radar cross section (RCS) are presented, and the far-field scattering characteristics of the waveguide are investigated in detail.

This paper presents an improvement of the calculation of the magnetic field components created by ring permanent magnets. The three-dimensional approach taken is based on the Coulombian Model. Moreover, the magnetic field components are calculated without using the vector potential or the scalar potential. It is noted that all the expressions given in this paper take into account the magnetic pole volume density for ring permanent magnets radially magnetized. We show that this volume density must be taken into account for calculating precisely the magnetic field components in the near-field or the far-field. Then, this paper presents the component switch theorem that can be used between infinite parallelepiped magnets whose cross-section is a square. This theorem implies that the magnetic field components created by an infinite parallelepiped magnet can be deducted from the ones created by the same parallelepiped magnet with a perpendicular magnetization. Then, we discuss the validity of this theorem for axisymmetric problems (ring permanent magnets). Indeed, axisymmetric problems dealing with ring permanent magnets are often treated with a 2D approach. The results presented in this paper clearly show that the two-dimensional studies dealing with the optimization of ring permanent magnet dimensions cannot be treated with the same precisions as 3D studies.

Light extraction efficiency of light-emitting diodes (LEDs) based on various photonic crystal (PhC) structures was investigated in this study. By using the plane wave method and the finite element method, the influence of several factors on the enhancement of light extraction was discussed, including lattice type, density of states from a photonic band diagram, ratio of cylinder radius and lattice constant, and thickness of a photonic crystal pattern. Some rules are given for the practical implementation of an optimized PhC-based LED with higher light extraction efficiency. In the simulation results, the maximum enhancement of the extraction efficiency could be found to be by a factor of approximately 2.8 for the optimized Archimedean tiling pattern in the LED device emitting at the center wavelength of 530 nm. However, with the use of optimized PhC structures, the square and triangular lattices reveal enhancements of ~1.7 and ~1.5, respectively. The extraction efficiency of the Archimedean PhC LED is much greater than that of the regular lattice PhC LED.

This paper presents a rhombic patch monopole antenna applied with a technique of fractal geometry. The antenna has multiband operation in that the generator model, which is an initial model to create a fractal rhombic patch monopole, is inserted at each center side of a rhombic patch monopole antenna. Especially, a modified ground plane has been employed to improve input impedance bandwidth and high frequency radiation performance. The proposed antenna is designed and implemented to effectively support personal communication system (PCS 1.85-1.99 GHz), universal mobile telecommunication system (UMTS 1.92-2.17 GHz), wireless local area network (WLAN), which usually operate in the 2.4 GHz (2.4-2.484 GHz) and 5.2/5.8 GHz (5.15-5.35 GHz/5.725-5.825 GHz) bands, mobile worldwide interoperability for microwave access (Mobile WiMAX), and WiMAX, which operate in the 2.3/2.5 GHz (2.305-2.360 GHz/2.5-2.69 GHz) and 5.5 GHz (5.25-5.85 GHz) bands. The radiation patterns of the proposed antennas are still similarly to an omnidirectional radiation pattern. The properties of the antenna such as return losses, radiation patterns and gain are determined via numerical simulation and measurement.

The effects of the surface slopes joint probability density, the shadowing function, the skewness of sea waves and the curvature of the surface on the backscattering from the ocean surface are discussed and an improved two-scale model modified by these four aspects is used to calculate the backscattering coefficient of the dynamic ocean surface. In order to deal with the surface skewness driven by wind, a new complementary term derived from the small perturbation method is included in the improved model, in which the Fourier transform of the third-order cumulant function, surface bispectrum, is employed. On this basis, with the oceanic whitecap coverage taken into account, a composite model for predicting the ocean surface backscattering coefficient is constructed tentatively, which incorporates the volume scattering into the total one. Finally, with the vector radiative transfer (VRT) theory employed, numerical illustrations are carried out for the backscattering coefficients versus wind speed, incidence angle and azimuth angle, respectively. The predictions of the composite model are verified in Ku- and Ka-bands through the comparison of numerical results with many sets of measured data and the aircraft measurement experiment carried out in ZHOUSHAN sea area also supports this model.