Yongpin Chen

A Novel Band-Notched Elliptical Ring Monopole Antenna with a Coplanar Parasitic Elliptical Patch for UWB Applications

A novel band-notched ultra wide-band antenna with a coplanar parasitic elliptical patch in an elliptical ring is presented in this paper. Printed on a dielectric substrate of FR4 with relative permittivity of 4.4 and fed by a 50Ω microstrip line, the proposed monopole antenna demonstrate a 10 dB return loss bandwidth of 2.91–11.91 GHz, with a band-notched at 5.15–5.98 GHz band and good radiation patterns. The proposed antenna is utilize the coplanar parasitic elliptical patch to reject the frequency band (5.15–5.85 GHz) limited by IEEE802.11a and HIPERLAN/2. The parameters which affect the performance of the antenna in terms of its frequency domain characteristics are investigated in this paper.

Modeling of Gan Hemt by Using an Improved K-Nearest Neighbors Algorithm

A novel black-box modeling method for field effect transistor (FET) based on an improved K-Nearest Neighbors algorithm is proposed in this paper. K-Nearest Neighbors algorithm, which has simple algorithm structure and high accuracy, has shown great potential in regression application. A Taylor series expansion method is employed in nonlinear elements modeling of FET to improve the physical meaning of black-box model. A GaN HEMT power device is used to demonstrate the proposed method. And the experimentation shows that the calculated results using improved K-Nearest Neighbors algorithm based model fit the measurement results well.

Analysis of scattering of composite cylinder structure using multilevel fast inhomogeneous plane wave algorithm

Scattering of composite cylinder structures containing both conductor and dielectric material plays an important role in the analysis of the radar cross sections (RCS) of complex targets. A fast algorithm, namely the multilevel fast inhomogeneous plane wave algorithm (MLFIPWA) (Bin Hu et al., Radio Science, vol.34, no.4, p.759-72, 1999) is implemented to solve this problem. It is based on the volume-surface integral equation (VSIE). Traditionally, the integral equation is discretized by MoM, and O(N/sup 2/) computational complexity is needed when an iterative method, such as conjugate gradient (CG), is used. The fast multipole method (FMM) (Lu, C.C. and Chew, W.C., IEE Proc.-H, vol.140, no.6, 1993) is applied to accelerate the matrix-vector multiplication, and achieves O(N/sup 3/2/). The FIPWA, based on a different expansion of Greens function compared to FMM, is also proposed for this purpose, and it achieves O(N/sup 4/3/); both attain O(NlogN) if a multilevel strategy is applied. Compared to MLFMM, the MLFIPWA can be easily expanded to solve the scattering of targets in an inhomogeneous environment. The method is accurate and efficient.

Compact Notch Filters Using Vertically-Coupled Meander Stub Resonators

In this paper, novel notch filters with compact size are proposed using two types (type I and type II) of vertically-coupled meander stub resonators. The new filter design methodology is derived from the concept of high impedance wire. This design methodology incorporates embedded meander λ/4 stub resonators. They are adopted as quasi-lumped-circuit elements for realizing compact size; vertical coupling is introduced to obtain a transmission zero. Lucid equivalent circuit models are given for both analysis and initial design. The center frequency, rejection bandwidth and level can be easily controlled by the stub parameters. To verify the design concept, two notch filters examples are designed and fabricated employing three cascaded types I and II stub resonators, respectively. Good insertion loss, sharp notch performance and compact size are achieved as demonstrated in both simulation and experiment.

A novel implementation of IEDG-based DDM for solving electromagnetic scattering from large and complex PEC objects

ABSTRACT A novel implementation of the integral equation discontinuous Galerkin (IEDG)-based domain decomposition method (DDM), named as the IEDG-DDM, is developed for the efficient analysis of electromagnetic scattering from large and complex perfect electrically conducting (PEC) objects. Due to the nature of the IEDG scheme, the proposed DDM is nonconformal and nonoverlapping. Therefore, each sub-domain can be meshed independently according to the local geometrical feature, leading to a flexible discretization and a minimum number of unknowns. Different from the IEDG formulation in the skew-symmetric interior penalty DDM, the current continuity at the sub-domain boundaries is enforced through a properly defined interior penalty term, where the error energy from the electric potential is minimized. Consequently, the troublesome implementation of the stabilization term, which requires complex geometrical operations to find the intersection of edges in a nonconformal mesh, can be totally avoided. The proposed DDM results in an effective nonoverlapping domain decomposition preconditioner and a fast convergence of Krylov sub-space iterative solvers can be achieved. This method can be easily applied to curved sub-domain boundaries or curvilinear discretizations. Numerical examples are presented to demonstrate the accuracy and efficiency of the proposed method.

Acceleration of Augmented EFIE Using Multilevel Complex Source Beam Method

The computation of the augmented electric field integral equation (A-EFIE) is accelerated by using the multilevel complex source beam (MLCSB) method. As an effective solution of the low-frequency problem, A-EFIE includes both current and charge as unknowns to avoid the imbalance between the vector potentials and the scalar potentials in the conventional EFIE. However, dense impedance submatrices are involved in the A-EFIE system, and the computational cost becomes extremely high for problems with a large number of unknowns. As an exact solution to Maxwell’s equations, the complex source beam (CSB) method can be well tailored for A-EFIE to accelerate the matrix-vector products in an iterative solver. Different from the commonly used multilevel fast multipole algorithm (MLFMA), the CSB method is free from the problem of low-frequency breakdown. In our implementation, the expansion operators of CSB are first derived for the vector potentials and the scalar potentials. Consequently, the aggregation and disaggregation operators are introduced to form a multilevel algorithm to reduce the computational complexity. The accuracy and efficiency of the proposed method are discussed in detail through a variety of numerical examples. It is observed that the numerical error of the MLCSB-AEFIE keeps constant for a broad frequency range, indicating the good stability and scalability of the proposed method.

A Novel JMCFIE-DDM for Analysis of EM Scattering and Radiation by Composite Objects

In this letter, a new integral equation domain decomposition method (IE-DDM) using electric and magnetic current combined-field integral equation (JMCFIE) is proposed for efficient electromagnetic analysis of composite objects. This method provides a flexible way to decompose a complex composite domain into several easily solvable nonoverlapping subdomains. In order to obtain a good approximation of the global solution, both electric and magnetic field interactions are considered at the subdomain interfaces, in addition to the traditional Robin-type transmission conditions. In this manner, the unphysical reflections at subdomain interfaces can be further suppressed. It is shown that the condition of the new JMCFIE-DDM system is much improved in this new implementation. Accuracy and efficiency of the proposed method are demonstrated through several numerical experiments.

IE-DDM with a novel multiple-grid p-FFT for analyzing multiscale structures in half space

We present an integral equation domain decomposition method accelerated by a novel multiple-grid precorrected fast Fourier transform (MG-p-FFT) for the efficient analysis of multiscale structures in a half space. Based on the philosophy of DDM, the original computational domain is partitioned into several non-overlapping sub-domains. By employing non-conformal discretizations to each domain boundaries, combined field integral equation with half-space dyadic Green’s function is proposed for each individual sub-domain. Subsequently, the MG-p-FFT with auxiliary Cartesian grids with different size, order, location, and spacing, is adopted in each sub-domain independently to account for the self-interactions. Here, the proposed MG-p-FFT scheme outperforms the existing single-grid p-FFT scheme for multiscale problems by reducing the computational time and memory consumption. The proposed method can also be viewed as an effective preconditioning scheme for multiscale problems in a half space. The validity and advantages of the proposed method are illustrated by several representative numerical examples.

Fast Analysis of Electromagnetic Scattering From Conducting Objects Buried Under a Lossy Ground

Electromagnetic scattering from conducting objects is investigated for the applications of underground detection. The air-soil composite is modeled by a classical half space where the dyadic Greens function can be defined and formulated. The electric field integral equation (EFIE) is employed to guarantee the accuracy and robustness of the analysis for arbitrarily shaped scatterers. The internal resonance of EFIE is first studied under typical working conditions (frequencies, soil water contents, etc.). It is shown that this spurious resonance is much alleviated due to loss of the soil. Next, the unbounded and ill-posed spectrum of the EFIE operator is remedied by a novel localized half-space Calderón preconditioner by further exploring the lossy nature of the background. Such preconditioning is extremely useful for objects containing multiscale features. Finally, the half-space multilevel fast multipole algorithm based on real-image approximation is adopted to accelerate the computation for electrically large scatterers. Several examples in the applications of subsurface sensing are demonstrated to validate the efficiency and accuracy of this method.

P-FFT Accelerated EFIE with a Novel Diagonal Perturbed ILUT Preconditioner for Electromagnetic Scattering by Conducting Objects in Half Space

A highly efficient and robust scheme is proposed for analyzing electromagnetic scattering from electrically large arbitrary shaped conductors in a half space. This scheme is based on the electric field integral equation (EFIE) with a half-space Green’s function. The precorrected fast Fourier transform (p-FFT) is first extended to a half space for general three-dimensional scattering problems. A novel enhanced dual threshold incomplete LU factorization (ILUT) is then constructed as an effective preconditioner to improve the convergence of the half-space EFIE. Inspired by the idea of the improved electric field integral operator (IEFIO), the geometrical-optics current/principle value term of the magnetic field integral equation is used as a physical perturbation to stabilize the traditional ILUT perconditioning matrix. The high accuracy of EFIE is maintained, yet good calculating efficiency comparable to the combined field integral equation (CFIE) can be achieved. Furthermore, this approach can be applied to arbitrary geometrical structures including open surfaces and requires no extra types of Sommerfeld integrals needed in the half-space CFIE. Numerical examples are presented to demonstrate the high performance of the proposed solver among several other approaches in typical half-space problems.