Ling-Lu Chen

DESIGN OF AN ULTRA-WIDEBAND POWER DIVIDER VIA THE COARSE-GRAINED PARALLEL MICRO- GENETIC ALGORITHM

An ultra-wideband (UWB) power divider is designed in this paper. The UWB performance of this power divider is obtained by using a tapered microstrip line that consists of exponential and elliptic sections. The coarse grained parallel micro-genetic algorithm (PMGA) and CST Microwave Studio are combined to achieve an automated parallel design process. The method is applied to optimize the UWB power divider. The optimized power divider is fabricated and measured. The measured results show relatively low insertion loss, good return loss, and high isolation between the output ports across the whole UWB (3.1{10.6GHz).

A Hybrid Method Based on Differential Evolution and Continuous Ant Colony Optimization and its Application on Wideband Antenna Design

An evolutionary learning algorithm based on difierential evolution strategy (DES) and continuous ant colony optimization (CACO) for wideband antenna design is proposed. The advantages of this hybrid method are demonstrated with several mathematical functions and a linear array pattern synthesis. This method is applied to design an E-shaped wideband patch antenna, which achieves the impedance bandwidth 4:8 » 6:53GHz. We compare the hybrid method with the traditional DES and CACO optimization algorithms, and the advantage of this hybrid method over the DES and the CACO is also demonstrated.

HYBRID-SURROGATE-MODEL-BASED EFFICIENT GLOBAL OPTIMIZATION FOR HIGH-DIMENSIONAL ANTENNA DESIGN

E-cient global optimization has been extensively used in problems with expensive cost functions. However, this method is not suitable for high-dimensional problems. In this paper, the radial basis function network is introduced into the e-cient global optimization, to avoid local optima and achieve a fast convergence for high-dimensional optimization. Our algorithm is applied to a 12-dimensional optimization of a transmitting antenna. Compared to the genetic-algorithm-based e-cient global optimization and the difierential evolution strategy, our algorithm converges to the global optimal value more e-ciently.

A novel ultra-wideband knife-shape TEM horn antenna design for transient application

As is well known, more pulse energy is distributed in the relatively low frequency range than that in the high frequency range for a short pulse excitation. However, its difficult to obtain a well low-frequency performance for the relatively limited spatial volume of antenna. Besides, the conventional knife-shape TEM horn antenna introduces some fluctuations in the main lobe radiation pattern over the center frequencies. In this paper, a new method is proposed to improve the aforementioned defects. A novel ultra-wideband(UWB) knife-shape TEM horn antenna is designed, which has simple construction, relatively small size and perfect performance for transient application. The simulation results show that the improved knife-shape TEM horn antenna structure exhibits low VSWR as well as good radiation pattern over 120 MHz −1250 MHz frequency band.

THE FINE-GRAINED PARALLEL MICRO-GENETIC ALGORITHM AND ITS APPLICATION TO BROADBAND CONICAL CORRUGATED-HORN ANTENNA

The flne-grained parallel micro-genetic algorithm (FGP- MGA) is developed to solve antenna design problems. The synthesis of uniformly exited unequally spaced array is presented. Comparison with the micro-genetic algorithm (MGA) has been carried out. It is seen that the FGPMGA signiflcantly outperforms MGA, in terms of both the convergence rate and exploration ability. The FGPMGA can also reduce the optimization time. Then the FGPMGA and the body of revolution flnite-difierence time-domain (BOR-FDTD) are combined to achieve an automated design process for conical corrugated-horn antenna. Numerical simulation results show that the horn antenna has good impedance matching (the VSWR is less than 1.5), stable beamwidth and gain, as well as good rotation symmetry patterns over the whole band 8»13GHz.

Amplification of electromagnetic waves by time reversal mirror in a leaky reverberation chamber

In this paper, the influential factors on focusing amplitude of electromagnetic waves by time reversal mirror in a leaky reverberation chamber have been analyzed. Taguchis method is combined with the finite difference time domain method to optimize the location of single time reversal mirror in the chamber. The optimization results indicate that higher focusing amplitude of time-reversed electromagnetic waves can be achieved via longer recording time and proper position of time reversal mirror in chamber. In the study of time reversal mirror array, it is shown that the increase of the time reversal mirror elements is contributory to the amplification of time-reversed waves, but the combined efficiency deteriorates.

A TIME-DOMAIN APPROACH FOR THE FAST DESIGN OF REFLECTOR IMPULSE-RADIATING ANTENNAS

It is di-cult to determine the feed radiation center and F/D of the re∞ector impulse-radiating antenna (IRA) in frequency- domain, due to its ultra-wideband (UWB) property. This paper presents an e-cient approach to design the re∞ector IRAs, via evaluating the transient radiation patterns (TRPs) of the feed for some given difierent radiation centers. Only one time-domain simulation for the feed is needed in this method. Comparing with the global optimization algorithms, our method is fast and reliable in the design of the re∞ector IRAs.

Design and simulation of an ultra-wideband parabolic antenna with three-source based on time reversal method

A novel application of the time reversal technique for multi-source reflector antenna design is proposed in this paper. The focus of a shaped reflector and the time sequence of its feeds can be determined by time reversal method, exploiting its spatial-temporal focusing property. Then a designed three-source parabolic antenna was simulated by the FDTD. The radiation properties show that the designed antenna can lead higher peak value of electric field which is 238% compared to a standard parabolic antenna with one-source and same aperture. It means time reversal method for designing multi-source antenna is effective, and can realize the spatial power combination in the far field.

A study of parallel FDTD for simulating large-scale TEM horn antenna array

Parallel computation technique is an effective way to solve large-scale electromagnetic problems. This paper writes the program of parallel FDTD based on the JASMIN framework. The parallel FDTD program was used for simulating the time-domain far field property of the electric dipole source and a single TEM horn antenna. Numerical results show that the program is correct and efficient. Two large-scale arrays of TEM horn antenna were simulated. Their near-field and far-field results were given. The two examples provide a solution for studying large-scale antenna array and show that the program has the ability to solve large-scale electromagnetic problems.

Quasi-Gregory Antenna for Subnanosecond Impulse Radiation

A quasi-Gregory antenna was designed for subnanosecond impulse radiation. It consists of an ellipsoidal feed, a mirror plane, and a paraboloidal reflector. The second focal point (F2) of the ellipsoidal dish can be regarded as the radiation center of the feed because electromagnetic waves launched from the first focal point of the ellipsoidal dish (F1) are in phase when arriving at point F2, according to geometric optics. The equivalent radiation angle at point F2 is a spherical sector; therefore, it can be designed to geometrically cover the paraboloidal reflector precisely. Gaussian pulses with widths of 200 and 330 ps are used to test the performance of this proposed impulse-radiating antenna (IRA). The 3-dB beamwidth of this proposed IRA with a 1.5 m aperture diameter for the paraboloidal reflector is less than ±3° in the H-plane and less than ±5° in the E-plane. Compared to some existing IRAs, this quasi-Gregory antenna is also suitable for radiating pulses in the subnanosecond regime.