Sequential Circuit Test Generation Using a Symbolic/Genetic Hybrid Approach

Symbolic and genetic techniques are combined in a new approach to sequential circuit test generation that uses circuit decomposition, rather than the algorithmic decomposition used in previous hybrid test generators. Symbolic techniques are used to generate test sequences for the control logic, and genetic algorithms are used to generate sequences for the datapath. The combined sequences provide higher fault coverages than those generated by existing deterministic and GA-based test generators, and execution times are significantly lower in many cases.     

MEMS层叠式微带贴片天线的FDTD分析

将微机电系统(MEMS)技术应用于射频(RF)领域,制作新型的微带天线,是目前的一个重点和热点.文章以Maxwell方程为出发点,应用时域有限差分(FDTD)法对MEMS层叠式微带贴片天线进行精确的分析,给出了经济实用的近似吸收边界条件,找到了一系列精确模拟微带贴片天线、有效减少存储空间和计算量、节约计算时间的方法.     

Modelling and Analysis of Cuk Converter Using Current Injected Equivalent Circuit Approach

The current-injected equivalent-circuit approach has been developed for modelling and analysis of switching dc-dc converters and is very versatile. This approach can also be applied for modelling and analysis of complex converters or cascaded converters. To demonstrate the ability of the current-injected equivalent-circuit approach, the modelling and analysis of a Cuk converter is carried out. A small signal equivalent-circuit model is obtained which represents both input and output properties of the nonlinear converter. The results are presented in the form of linear equivalent-circuit models, as well as transfer functions.     

A Compact Wide-Band Rat-Race Hybrid Using Microstrip Lines

A compact microstrip rat-race hybrid with a 50% bandwidth employing space-filling curves is reported in this letter. The footprint of the proposed design occupies 31% of the area of the conventional similar design. Across the frequency bandwidth, the maximum amplitude unbalance is 0.5 dB, the phase variation is plusmn5^deg , the isolation is better than 25 dB and the return loss is greater than 10 dB. Moreover, the circuit is planar, easy to design, and consists of only one layer without requiring plated thru holes, slots or bonding wires.     

A Broadband Compact Microstrip Rat-Race Hybrid Using a Novel CPW Inverter

A new compact microstrip rat-race hybrid with an octave bandwidth employing a novel frequency-independent coplanar waveguide (CPW) phase inverter is reported in this paper. The 270deg branch of a conventional rat-race is replaced by a -90deg branch, which is realized by a 90deg microstrip line and the CPW phase inverter. A new microstrip-to-CPW transition is introduced for which a lumped-element model is devised to facilitate parameter optimization. The designed transition has an insertion loss less than 0.33 dB across the designed frequency band from 1.5 to 3.5 GHz. The footprint of the proposed design is reduced by 75% and shows almost 60% and 80% enhancements in the 0.5-dB mismatch bandwidth of amplitude and 10deg mismatch bandwidth of phase, respectively, when compared with the conventional implementation. The proposed hybrid can be fabricated using a conventional printed-circuit and plated thru-hole technologies     

微带对数周期天线的FDTD分析

应用FDTD方法分析了一种电磁耦合微带对数周期天线的宽频带特性，通过FFT得到天线的阻抗特性、反射损耗及增益等，其结果对实际设计工作具有指导性意义。     

Parallel Plate Cavity Mode Suppression in Microstrip Circuit Packages Using a Lid of Nails

The suppression of parallel plate and cavity modes in shielded microstrip circuits is presented. To this aim a textured metal lid consisting of periodically located pins known as a bed of nails is employed. The mode suppression has a bandwidth of more than 2:1, and it does not interfere much with the microstrip circuit. Thereby, this mode suppression technique introduces a new advantageous packaging technology for high frequency circuits.      

基于时域有限差分法的微带天线分析

微带天线具有许多优点,在许多领域得到广泛应用。为精确设计微带天线,需了解描述天线性能的电参数。介绍了一种数值分析方法——时域有限差分法（FDTD）,从Maxwell旋度方程出发推导FDTD差分格式计算过程,总结出分析电磁问题的一般步骤,并采用FDTD分析了一款典型的微带天线。和电磁仿真软件XFDTD仿真结果相比较,可以看出FDTD计算结果与软件仿真结果吻合得很好。     

Speeding Up PEEC Partial Inductance Computations Using a QR-Based Algorithm

The partial element equivalent circuit (PEEC) approach has been used in different forms for the computation of equivalent circuit elements for quasi-static and full-wave electromagnetic models. In this paper, we focus on the topic of large scale inductance computations. For many problems as part of PEEC modeling, partial inductances need to be computed to model interactions between a large numbers of objects. These computations can be very time and memory consuming. To date, several techniques have been devised to reduce the memory and time required to compute the partial inductance entities, as well as the time required to use them in a circuit analysis compute step. Some of the existing methods use hierarchical compression while some others are based on issues like properties of the inverse of the partial inductance matrix. However, because of inherent limitations, most of these methods are less suitable for PEEC applications. In this paper, we present an approach which is based on the compression of the partial inductance matrix utilizing the QR decomposition of the far coefficients submatrices. The QR-decomposed form is represented as a compressed SPICE-compatible circuit. This yields an efficient and mathematically consistent approach for reducing the storage and time requirements     

含集总元件的微带电路FDTD仿真

从Maxwell旋度方程出发,根据集总元件的伏安特性,推导了电阻、电容、电感、二极管、三极管等基本微波电路元件的单网格和多网格FDTD模型。单网格模型是不论集总元件的形状和大小都只占据一个网格的处理方法;多网格模型则是根据集总元件的实际形状和大小将元件跨接在多个网格上,显然这种处理方法更符合实际情况。最后仿真了一个由单个元件组成的简单微带电路——上限限幅器。仿真结果与理论结果吻合得很好,证明了仿真结果的正确性。     

微带功放电路的调测与检修

微带功放电路的用途十分广泛,无论是调频电视波段,还是微波传输波段,抑或是通信波段都要用到它。本文从广电通信技术工作需要出发,详细地论述了微带功放电路的调测与检修方法。     

Computer-Oriented Synthesis of Optimum Circuit Pattern of 3-dB Hybrid Ring by the Planar Circuit Approach

A fully computer-oriented synthesis of the optimum circuit pattern of a 3-dB hybrid ring based upon the planar circuit concept is described. In the synthesis process, the contour-integral method, and Powell's method are used for the circuit analysis, the optimization, respectively. The synthesized optimum patterns are given in normalized curves, parameters which can directly be used in practical circuit design. The validity of the theory is confirmed by experiment. It is shown both theoretically, experimentally that the planar circuit approach can, not only prevent the deterioration of the hybrid characteristics due to the widening of the circuit, but bring forth hybrid characteristics somewhat better than the distributed constant model. It is also shown that the obtained optimized characteristics can further be improved by addition of simple external circuits.     

Hybrid MFIE/FDTD method for analysis of metallic enclosures with slots

A method for the analysis of the electromagnetic field inside metallic enclosures with apertures is presented. The model is based on a time domain hybrid approach method, characterised by the combination of the finite difference in time domain (FDTD), and the method of moments in time domain (MoMTD) that solves a magnetic field integral equation (MFIE).     

Efficient Analysis of Phased Arrays of Microstrip Patches Using a Hybrid Generalized Forward Backward Method/Green's Function Technique With a DFT Based Acceleration Algorithm

A hybrid method based on the combination of generalized forward backward method (GFBM) and Green's function for the grounded dielectric slab together with the acceleration of the combination via a discrete Fourier transform (DFT) based algorithm is developed for the efficient and accurate analysis of electromagnetic radiation/scattering from electrically large, irregularly contoured two-dimensional arrays consisting of finite number of probe-fed microstrip patches. In this method, unknown current coefficients corresponding to a single patch are first solved by a conventional Galerkin type hybrid method of moments (MoM)/Green's function technique that uses the grounded dielectric slab's Green's function. Because the current distribution on the microstrip patch can be expanded using an arbitrary number of subsectional basis functions, the patch can have any shape. The solution for the array currents is then found through GFBM, where it sweeps the current computation element by element. The computational complexity of this method, which is originally ( being the total number of unknowns) for each iteration, is reduced to using a DFT based acceleration algorithm making use of the fact that array elements are identical and the array is periodic. Numerical results in the form of array current distribution are given for various sized arrays of probe-fed microstrip patches with elliptical and/or circular boundaries, and are compared with the conventional MoM results to illustrate the efficiency and accuracy of the method.     

Optimizing the Gain and Directivity of a Microstrip Antenna with Metamaterial Structures by Using Artificial Neural Network Approach

Wireless Personal Communications - The daily rapid malware growth and spread has enforced the security community of antivirus companies to introduce cloud computing technology to their existing...     

Ultra-Wideband (UWB) Bandpass Filters With Hybrid Microstrip/Slotline Structures

A novel ultra-wideband (UWB) bandpass filter is presented using back-to-back microstrip-slotline transition and triple-mode slotline resonator. A uniform slotline resonator is constructed with a length of one full wavelength at the central frequency. Two microstrip feed lines are then placed above the slotline resonator to make up a back-to-back microstrip-slotline transition, where two intersection points are equally located at one quarter-wavelength away from two short-ends. By properly stretching the microstrip line lengths, an ultra-wide passband is constituted with the lower/upper cut-off edges dominated by the first/third resonant modes.By forming a W-shaped slotline resonator, introducing a cross coupling and cascading two lowpass filters, two UWB bandpass filters with improved out-of-band performances are designed, fabricated and measured. Measured results achieve a 2.56-to-10.90 GHz or 124% passband with return loss >12.04 dB, group delay variation <0.58 ns, sharpened rejection skirts and extended upper-stopband.     

High-Field Magnetic Resonance Imaging With Reduced Field/Tissue RF Artefacts—A Modeling Study Using Hybrid MoM/FEM and FDTD Technique

Due to complex field/tissue interactions, high-field magnetic resonance (MR) images suffer significant image distortions that result in compromised diagnostic quality. A new method that attempts to remove these distortions is proposed in this paper and is based on the use of transceiver-phased arrays. The proposed system uses, in the examples presented herein, a shielded four-element transceive-phased array head coil and involves performing two separate scans of the same slice with each scan using different excitations during transmission. By optimizing the amplitudes and phases for each scan, antipodal signal profiles can be obtained, and by combining both the images together, the image distortion can be reduced several fold. A combined hybrid method of moments (MoM)/finite element method (FEM) and finite-difference time-domain (FDTD) technique is proposed and used to elucidate the concept of the new method and to accurately evaluate the electromagnetic field (EMF) in a human head model. In addition, the proposed method is used in conjunction with the generalized auto-calibrating partially parallel acquisitions (GRAPPA) reconstruction technique to enable rapid imaging of the two scans. Simulation results reported herein for 11-T (470-MHz) brain imaging applications show that the new method with GRAPPA reconstruction theoretically results in improved image quality and that the proposed combined hybrid MoM/FEM and FDTD technique is suitable for high-field magnetic resonance imaging (MRI) numerical analysis     

Upper Bound Calculations on Capacitance of Microstrip Line Using Variational Method and Spectral Domain Approach

In this paper, the authors have employed an analytical approach based on the Fourier transformation and variational techniques in terms of the surface potential of the dielecric sheet to find the upper bounds of the microstrip line capacitance. It is hoped that our work will complement that of Yamashita et al., who calculated the lower bounds dealing with the charge density on the surface of the conductor strip, in estimating the margins of error in calculation.