Abstract-An Improved Differential Evolution (IDE) algorithm is proposed for optimization problems. With the novel mutant operation adopting sub-optimal individual, the convergence of Differential Evolution (DE) algorithm is accelerated without increasing the risk of premature. Five typical test functions are minimized using DE and IDE algorithms, and the results show the superior performance of IDE algorithm. Furthermore, the algorithm is applied to pattern synthesis of two antenna arrays. Broad nulls are formed in radiation pattern of a linear array to suppress broad-band interferences. In a microstrip patch array, the sidelobe level of array is decreased about 12.9 dB and the mainlobe can scan to the desired angle.

In this article, an extended particle swarm optimization (EPSO) algorithm is proposed for designing conformal phased arrays. On the basis of traditional particle swarm optimization (PSO), novel velocity updating mechanism, new exceeding boundary control operator, and global best perturbation are introduced in EPSO to overcome the drawbacks of PSO. To validate the efficiency of the proposed algorithm, both the classical test functions and the scenarios concerning a 1 Â 9-element cylindrical conformal phased array and a 3 Â 9(27)-element cylindrical conformal array with flat-top shaped-beam pattern are presented. Simulation results show that the proposed method is superior to genetic algorithm (GA) and PSO when applied to both the classical test functions and the practical problems of conformal antenna array synthesis.

Abstract-A new method called Expanded Cholesky Method (ECM)is proposed in this paper. The method can be used to decompose sparse symmetric non-positive-definite finite element (FEM) matrices. There are some advantages of the ECM, such as low storage, simplicity and easy parallelization. Based on the method, multifrontal (MF) algorithm is applied in non-positive-definite FEM computation. Numerical results show that the hybrid ECM/MF algorithm is stable and effective. In comparison with Generalized Minimal Residual Method (GMRES) in FEM electromagnetic computation, hybrid ECM/MF technology has distinct advantages in precision. The proposed method can be used to calculate a class of non-positivedefinite electromagnetic problems.

A dual-plane resonant cell wideband bandpass filter is proposed and designed on substrate integrated waveguide (SIW) cavities using U-shape slots and H-shape fractal defected ground structure (DGS). The U-shape slots etched on the top meta layer of the SIW cavity are used to constitute a multiple-mode resonator and the H-shape fractal DGS etched on the bottom metal layer can greatly improve the filter performance while keeping the overall size of the filter circuit to be much compact. The proposed filter can lead to a size reduction of approximately one-third compared with the traditional SIW filters only using U-shape slots on the top metal plate of the SIW cavity. The filter has been fabricated and experimentally measured. The measured data are in good agreement with the simulated results. The measured 3 dB bandwidth is from 7.15 to 11.25 GHz, representing a fractional bandwidth of 44.6% at a center frequency of 9.2 GHz. Within the passband, the measured return loss performance is quite good (below 222dB), and the insertion loss is measured to be 1.05 dB, including the loss from two SMA connectors.

We present a new bandpass filter by combining an isosceles right‐triangle substrate integrated waveguide (SIW) cavity with a complementary split ring resonator (CSRR) together. The first and second modes of the SIW cavity are used to form a desirable passband with the help of a perturbation metallic via‐hole. We introduce a CSRR at the ground plate of the SIW cavity to produce two controllable transmission zeros at the upper stopband, which improve the upper stopband characteristic greatly. Moreover, at the lower stopband, we make use of a pair of T‐shape stub‐loaded resonators to generate a transmission zero, and thus improve the out‐of‐band rejection greatly. To validate our design scheme, a filter sample has been fabricated and measured. The measured results and simulation ones are in good agreements. The filters show advantages of compactness, sharp stopband rejection, high frequency‐selectivity, and controllable passband and transmission zeros.