S.-X. Gong

A NOVEL IGA-EDSPSO HYBRID ALGORITHM FOR THE SYNTHESIS OF SPARSE ARRAYS

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.

RCS Reduction of Array Antenna by Using Bandstop FSS Reflector

This paper investigates the application of a novel frequency selective surface (FSS) reflector for 4×2 dipole array antenna to reduce radar cross section (RCS) out of operating band. The proposed FSS adopting a regular hexagon quasi-fractal structure has good bandstop characteristic. By replacing the metal reflector with this bandstop FSS sheet, the in-band radiation performance of the proposed array antenna is preserved, while the out-of-band backward RCS is significantly reduced. Due to the good angle stability of the given FSS, the monostatic RCS peaks at oblique angle ( = 60°, ϕ = 0°) are also controlled. The measured results demonstrate the feasibility of antenna RCS reduction by this method.

A Modified PSO for Low Sidelobe Concentric Ring Arrays Synthesis with Multiple Constraints

This paper describes a modified particle swarm optimization (MPSO) for the synthesis of the low sidelobe concentric ring arrays. The MPSO has been utilized to optimize the element placement in a concentric ring array to obtain the lowest peak sidelobe level (PSLL). And here the multiple optimization constraints include the array aperture, the minimum ring spacing and the element spacing in each ring. Unlike standard PSO using fixed corresponding relationship between the optimal variables and their coding, the MPSO utilized the coding resetting of optimal variables to avoid infeasible solution during the optimization process. Also, the proposed approach has reduced the size of the searching area of the PSO by means of indirect description of individual. The simulated results confirming the great efficiency and robustness of this algorithm are provided in this paper.

Compact and Low Coupled Monopole Antennas for MIMO System Applications

A novel compact MIMO antenna with high port isolation is presented in this paper. The designed antenna operates at 2.4 GHz with a bandwidth of 2.37–2.46 GHz. In order to improve the isolation between the ports of the two monopoles, a decoupling network is added into the circuit, and a slot is etched on the ground. Simulated and measured results illustrate that the proposed antenna obtains isolation higher than 35 dB while maintaining good impedance matching. The predicted results are compared with the measured data, and good agreement is found.

A Microstrip Printed Dipole Antenna with UC-EBG Ground for RCS Reduction

In this paper, A S-band microstrip printed dipole antenna with a distorted uniplanar compact-EBG (DUC-EBG) ground plane is proposed and investigated. The simulated and measured results show that the RCS of the microstrip printed dipole antenna with the proposed DUC-EBG ground is much lower than that of the antenna with the conventional metallic ground at frequencies outside the operating band within 1–8 GHz, while its radiation is hardly affected by the proposed DUC-EBG ground in the operating band. Owing to the stop-band property of the proposed DUC-EBG, it can be used as the ground plane of a microstrip printed dipole antenna. During the pass-band, the proposed DUC-EBG can make much more incident wave pass through. Therefore, it can effectively reduce the RCS of microstrip printed dipole antenna outside operating band.

A Novel Low RCS Mobius-Band Monopole Antenna

A novel mobius-band monopole antenna (MBMA) using several metallic via holes, which is based on the concept of topology, is designed to realize radar cross section (RCS) reduction compared to a common printed circular-disc monopole antenna (PCDMA). The characteristic of mobius-band realizes antenna RCS reduction. UWB-related characteristics of the proposed antenna including the return loss and radiation patterns are simulated and experimentally verified. Mobius-band antenna and the reference antenna are both UWB antennas whose RCS performances under different loads are studied and compared. The results show that the proposed antenna has lower RCS than the reference antenna in the whole frequency band while maintaining good radiation performances, which illuminates that MBMA is a good candidate for antennas with or without a requirement of RCS control.

Radiation Pattern Synthesis for Arrays of Conformal Antennas Mounted on an Irregular Curved Surface using Modified Genetic Algorithms

An E-shaped conformal microstrip antenna array mounted on an irregular curved surface which is similar to an aerocraft cavity in shape is developed in this paper. In view of the narrow bandwidth of the microstrip antenna, an E-shaped element is applied instead of the traditional rectangular element. Furthermore, an element structure of uneven thickness is adopted in order to take into account the effects of the carrier on the resonance frequency and bandwidth of the conformal array. Then, an 8-element conformal microstrip antenna array is designed and the radiation pattern is synthesized using the modified genetic algorithms (MGAs). Compared with the standard genetic algorithms (SGAs), MGAs has a much more fast convergence speed and need less computational time to reach the expected value. The result shows that the optimized azimuth radiation pattern is almost omnidirectional and the elevation radiation pattern is concentrated in the horizontal direction. It can be seen that the proposed method of MGAs is an effective means for designing the conformal antenna array on an irregular curved surface.

A Novel Technique for Radar Cross Section Reduction of Printed Antennas

A novel technique for radar cross section (RCS) reduction of printed antennas is proposed in this paper. After analyzing the current distribution on the surface of the printed antenna in working state, the region with small current amplitude is decreased in area. Then the RCS of the antenna would be reduced without effects on the radiation performance. Based on a printed UWB antenna, a modified antenna is presented as an example to validate the novel technique of radar cross section reduction (RCSR). Radiation and scattering characteristics of the modified and reference antennas are simulated and experimentally verified. The results show that the modified antenna has lower RCS than the reference antenna in the whole frequency band while maintaining the same radiation performances, which illuminates that the proposed technique is a good candidate for printed antennas with a requirement of RCS control.

Fast Shadowing Technique for Electrically Large Targets Using Z-Buffer

An improved fast shadowing technique fit for the calculation of electromagnetic field is proposed in this paper based on the shadowing technique of z-buffer in computer graphics. The traditional shadowing algorithm consumes too much time, for it is necessary to judge the shadowing relationship of every two facets. The proposed algorithm combining z-buffer with traditional algorithm falls into the shadowing processing using triangle facet modeling. The problem of great time consumption in shadowing judgment for electrically large targets is well solved through proper subdivision of buffer and localization of judgment within facets in the surrounding buffer elements. The proposed arithmetic has great advantages over the traditional one, especially in its high running speed. This improved technique is tested to be valid in that it remarkably increases the computation speed on the premise of satisfying the precision requirement.

Wide-Band Analysis of On-Platform Antenna Using MoM-PO Combined with Maehly Approximation

An efficient method for wide-band analysis of antennas radiating in the presence of an electrically large conducting platform is proposed. The method is based upon the well known method of moments-physical optics (MoM-PO) hybrid formulation combined with the Maehly approximation. Compared with the asymptotic waveform evaluation (AWE) technique, the major advantage of the Maehly approximation is that it does not require the complex computation concerning dense impedance matrix, and it can be easily implemented into an existing MoM-PO computer code. Numerical results show that the proposed method is superior, in terms of CPU time, to the traditional MoM-PO.