Cheng Liao

Analysis of the numerical error for time domain MEI absorbing boundary condition

The measured equation of invariance (MEI) method is applied widely in the numerical simulation of the EM scattering problems. The paper discussed the reflection errors of time domain MEI-ABC, and compared with other truncating boundary conditions. The results shown that, by applying the time domain MEI-ABC, the accuracy of the MEI-ABC is higher than other methods for the case of truncating boundary near to the source. It is proved that the time domain MEI-ABC is an effective method of high accuracy and is less time consuming to treat the problems of EM radiation.

Acceleration of Time-Domain Finite Element Method (TD-FEM) Using Graphics Processor Units (GPU)

The time-domain finite element method is used extensively in areas of microwave engineering. However, TD-FEM runs too slow for some simulations to be practical, especially when run on standard personal computers. The propriety of hardware for the acceleration of TD-FEM computations has been investigated. It is well known that the key of TD-FEM is matrix operation. There always be an obstacle that the speedup of dense matrices operations in Graphics Processor Units fields. This situation will be improved in next generation. Even though the presence of the obstacle, the standard consumer Graphics Processor Units (GPUs) can be used to accelerate TD-FEM simulations by a factor of close to two yet, relative to an Intel CPU of similar technology generation. With OpenGL as the Application Programming Interface (API), a standard commercial graphics card has been programmed to solve a 2-D electromagnetic radiation problem.

Combination-optimization method for ultra-wide band TEM horn antenna array using micro-genetic algorithm

Finite-difference time-domain method (FDTD) and micro-genetic algorithm (MGA) are combined to optimize time- domain ultra-wide band (UWB) transverse electromagnetic (TEM) horn antenna array. Firstly, FDTD was applied to obtain the time-domain information of elementary antenna. According to principle of superposition, the antenna array could be primarily optimized using MGA without regard to mutual coupling effect. Secondly, the whole antenna array was simulated by FDTD. The first optimal results then acted as the known knowledge to reduce the searching range of MGA and the antenna array was optimized for the second time. Hence, the optimization speed can be greatly accelerated by using combination-optimization method described above while mutual coupling effect is taken into account. As an example, a 4-element UWB planar TEM horn antenna array was optimized to show the validity. The results confirmed it and the computational time decreased by 48.6%.

Numerical analysis and simulation of high power microwave pulses propagation in the atmosphere using FDTD method

An appropriate numerical scheme based on the finite-difference time-domain (FDTD) method is firstly presented for high power microwave (HPM) pulses propagating through the atmosphere, which solves numerically Maxwells equations and Boltzmanns equation self-consistently. The derived difference scheme can be solved by time stepping. Especially, a novel method is presented that the variables coupled each other in the difference equations are solved by the binary linear equations before the time stepping. The propagation problems of HPM pulses in air breakdown environment are investigated and analyzed, and the feasibility and validity of the new numerical scheme is demonstrated.

Monostatic microwave imaging of arbitrary convex PEC cylinder

Monostatic approach to 2D microwave imaging is proposed, in which the global optimization method is served as solver and the signal pre-processing is used to estimate the sparse size of unknown object and to determine the range of parameters for optimization method. By comparing efficiency of MGA with that of GA Two test examples are presented and the optimized results are briefly discussed.

Comparison Study on Single-layered and Double-layered Differential Symmetric Circular Spiral Inductors

Based on the Ansoft 3D electromagnetic field software HFSS and the typical lumped equivalent-circuit model of spiral inductors on silicon (SIOS) for RF integrated circuits (RFICs), the comparison study of single-layered and double-layered differential symmetric circular spiral inductors has been given. The numerical analyses showed that the former can give better results of quality factor (QF) and self-resonant frequency (SRF) and the L value of the former can satisfied the nH level requirements where the Q factor obtains its highest value. Experimental results showed that the former can gives a 50.5% increase for the maximum Q value and 164.5% increase for the SRF whereas the latter can supply over 3 times larger L value. The simulation results have good agreements with the theoretical analyses. At last the design guidelines were given according to the simulation and experimental results.

Application of micro-genetic algorithm (MGA) to monostatic microwave local imaging of PEC cylinder

In order to improve the method of the microwave imaging based on numerical optimizations, the single-illumination single-view (SISV) approach is proposed and the optimization is realized by means of the micro-genetic algorithm (MGA). In our simulations the resonance frequency of PEC object is obtained in terms of FFT, and then the range of the parameters used in the MGA can be determined automatically

Monostatic microwave local imaging of PEC cylinder based on genetic algorithm

In this paper, a single-illumination single-view approach to microwave imaging based on genetic algorithm (GA) is proposed, the aim is to get the PEC local shape information. The nonlinear inverse scattering problem is recast in an optimization problem. For speeding GA convergence, the coarse shape information of the PEC object obtained from the scattering signal is being provided as the searching range of GA. The processing procedure of the approach is described and local images of reconstructed square cylinders are reported.

Researchment and design of CMOS low noise amplifier in UHF band

To overcome difficulties among power, noise figure(NF) and match in the design of low-noise amplifier(LNA), a novel approach that can realize effective compromise among them is presented through analyzing the cascade LNA configuration. Under the premise that power can be accepted, the new approach can be achieved by adopting series inductors in input port, adding capacitors between gate and source nodes and appending series inductor-resistance to the output port. Experimental results show that, with the proposed approach, a 0.18 mum CMOS LNA at 2.4 GHz could provide a maximum NF of 0.46 dB, a minimum power gain of 22 dB in 3 dB bandwidth, input and output VSWRs which are better than 1.12, the output P1dB power of 1.07 dBm and 25.02 mW whole power consume. Theory analysis agrees well with the simulation results.

Investigations on linear coupling function of UWB pulse into computer case

In this paper, we studied linear coupling function of the ultra-wide-band (UWB) pulse coupled to the computer case with different kinds of slots, apertures and hole arrays by the finite-difference time-domain (FDTD) method combined with fast Fourier transform (FFT) method.