Electromagnetic simulation of complex and electrically large structures in WIPL-D Pro [Application Notes]

This article has demonstrated the application of higher order basis functions, smart reduction of expansion orders, and multilevel fast multipole method in efficient 3-D EM simulation of complex and electrically large structures (from compact multiband antenna for wireless applications to 160 long aircraft scatterer) at a desktop computer.     

Mathcad

Discusses the use of Mathcad software in an electrical engineering course. It is used to solve problems in electromagnetism such as electrostatics, plane wave propagation, antennas and transmission lines     

Active integrated antennas

Even with microwave techniques, however, signal losses in materials and decreased gain and power from solid-state devices become significant obstacles to creating low-cost, high-frequency wireless systems. Perhaps the most dramatic effect occurs when a circuit component becomes a significant fraction of a wavelength. At this point it may begin to function well as an antenna. For microwave and mm-wave signals, this can occur with circuits that are only centimetres in size. With conventional circuit techniques, this radiation may cause drastic signal losses, spurious coupling between circuit elements, and radio interference with other. However, with new techniques, it is possible to create circuits that use these effects to advantage. Known as active integrated antennas, these circuits have sparked interest as possible solutions to problems in designing the next-generation wireless systems. Active integrated antennas are a combination of solid-state devices and circuits with printed antenna structures. They comprise integrated radio-system elements that are fabricated using inexpensive printed-circuit techniques     

Arbitrary wire antenna above lossy half-space: rapid accurate image solution

A simple, approximate, but very rapid and accurate image method is proposed for the analysis of arbitrary wire antennas above a lossy half-space. The reflected field from vertical and horizontal Hertzian dipoles is approximated by the field of a few ‘optimally’ positioned simple elementary sources. The field of images is incorported into the Hallén-type equations for the current distribution, resulting in equations of essentially the same form as those for an isolated antenna. The equations are solved by the point-matching method and polynomial approximation of current along the antenna segments. The results for the impedance and admittance of antennas assembled of vertical, horizontal and/or oblique segments are in excellent agreement with the exact results (obtained from the Sommerfeld theory). The proposed method is conceptually very simple and on average 25 times faster than the exact method, although in some cases it was found to be faster for even two orders of magnitude. This makes it particularly suitable for numerical optimization and CAD of relatively complicated antennas and other wire structures above a lossy half-space. © 1997 John Wiley & Sons, Ltd.     

On Short Antennas Immersed in Two Dielectrics

With the assumption that the customary current distribution and far-field distance approximations apply, this paper develops the far-field expressions for short linear antennas (2h=l相似文献   

虚拟接收天线MIMO系统及其检测

分层空时接收机的空时复用MIMO可以获得容量的线性增长,但是分层空时处理过程需要接收天线的数量必须至少等于或大于发送天线的数量,对于体积很小的移动手机来说设计多根天线是很困难的,从而阻碍了其广泛的发展。提出了空间复用系统中虚拟接收天线的新概念。每个子数据流都进行一定的时间偏移再传输,同时对接收端输出信号过采样,虚拟接收天线就产生了,物理接收天线的数量相应得到减少。     

甚高频全向信标（VOR）/仪表着陆系统（ILS）标准信号源设计

甚高频全向信标/仪表着陆系统标准信号源可用于甚高频全向信标/仪表着陆系统机载设备的检测与维修。本文较详细阐述了该标准信号源的设计原理;简要介绍了标准信号源中采用的目前较为先进DSP技术、锁相式多波段频率合成技术、数字式直接频率合成技术(DDS)等7种技术的应用情况;论述了设计过程中遇到的多种低频调制信号的合成、高精度调制度差值的实现等难点问题的解决方法。文中介绍的标准信号源已经小批量推广应用,其使用技术具有一定的借鉴意义。     

预编码方案多天线超宽带系统误码率性能计算

多天线技术引入超宽带系统是提高传输质量和抗干扰能力、降低误比特率(BER)的有效方法之一。然而,随着天线数目的增加,硬件成本也随之提高。天线选择技术和优化发射功率能降低硬件成本、复杂度及提高系统性能。若已知全部的发射端信道状态信息(CSI),提出了最大比率发射(MRT)技术和发射天线选择(TAS)技术相结合的超宽带系统。基于信道功率增益最大的天线选择准则,系统选择较好的天线子集(MT ,2;MR )工作,并采用 MRT技术优化分配所选择的双天线发射功率。仿真结果表明：结合MRT和 TAS技术的超宽带系统的误比特率性能都得到了明显改善。     

Multiport vector network analyzer measurements

An increasing number of multiport devices, whether they be multiband wireless phone components, backplane balanced transmission lines, or classical devices such as power dividers, are being characterized in the RF, microwave, and millimeter-wave frequency bands. S-parameter measurements are often required, and ordinary vector network analyzer (VNA) measurements must be modified to perform these measurements quickly and accurately. This article explores a number of hardware architectures and calibration procedures for multiport measurements and their impacts on flexibility and uncertainties.     

RF MEMS technology

Recently, to meet the demands of multimode/multiband functions for the next generation communication systems, RF MEMS technology is being developed for the reconfigurable transceiver system. In this article, RF MEMS devices such as switches, high‐Q inductors, and high‐Q resonators are reviewed for their operating principles and device structures, as well as the reliability and commercial issues. Single pole single throw (SPST)‐type MEMS switches show characteristics superior to solid‐state switches in the aspects of insertion loss, isolation, and linearity. Single pole multithrow (SPMT) switches will enable ultra small‐sized cellular phones, but insertion loss and coupling between channels should be improved. For a high‐Q inductor, out‐of‐plane inductors show improved results, and an inductor with a Q‐factor of 75 at 1GHz has been fabricated by using the internal stress of a MoCr film. The MEMS inductor improves the performance of a voltage controlled oscillator (VCO), but proper hermetic packaging and standard libraries are also necessary for mass production. The MEMS resonator can operate up to 1.4 GHz and can be used as an oscillator for the timing device as well as component of the filter circuit. The SiTime Company recently has started delivery of a product with performance similar to the quartz oscillator, in which they solved the reliability issues by modifying the annealing and vacuum packaging. Copyright © 2007 Institute of Electrical Engineers of Japan© 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Duo triangle-shaped rectangular microstrip-fed patch antennas input and output parameters investigation

Conventional rectangular microstrip-fed patch antennas are initially investigated numerically within the frequency band 2.0 to 2.8 GHz for Wi-Fi applications. In order to enhance the input parameters of the underlying antennas, three prototypes are designed. A split is diagonally loaded on a conventional radiating patch to achieve a duo triangle-shaped microstrip-fed patch antenna in the first step. The conducting ground plane of the conventional and the duo triangle-shaped patches is modified to design the microstrip-fed monopole and duo triangle-shaped monopole antennas in the second and third steps, respectively, within the frequency band of 2.0 to 7.0 GHz. Concepts of voltage and current waves as well as classical electrostatics approach solutions are used to, respectively, investigate the return loss bandwidth and the electric field radiation pattern of the proposed antennas. Numerical simulations show some relevant antenna performances such as a triple-band, a −10-dB return loss bandwidth of 29% , a gain of 7.5 dB, and a calculated half power beam width of 120^° in E-plane.     

FAST SIMULATION OF MICROSTRIP STRUCTURES USING THE FAST MULTIPOLE METHOD

We apply a new method of reducing the computational effort required for solution of the Electric Field Integral Equation used for modelling microstrip structures. The Fast Multipole Method is used to compute the radiation pattern and input impedance of single layer microstrip antennas.     

车载通信系统天线电磁特性的研究

天线是车载通信系统的重要设备,研究天线的电磁特性对提高车载通信系统电磁兼容性能十分重要。基于DSRC通信模型,利用分层建模的方法建立全尺寸逼真汽车模型和鞭状天线模型,应用FMM算法仿真分析天线的反射系数和汽车上不同位置处天线水平增益方向图的变化情况,并研究分析通信环境对车载通信系统天线耦合度的影响。结果表明：仿真模型和算法能够正确模拟干扰因素对车载通信系统天线电磁特性的影响。     

不同场景车载天线电磁特性研究

天线是车载通信系统的重要设备,天线电磁特性的研究对提高车载通信系统电磁兼容性能十分重要,是实现车载通信的基础.根据理论推导和经验公式,分析了城市和高速公路等不同场景下车载天线电磁波传输特点,建立了电磁波传输模型,仿真分析了车载天线电磁特性.仿真结果得出了不同场景下通信距离、车体形态与天线增益的关系;结果表明随着通信距离...     

On the design of multiband transmission functions synthesized by one wave digital lattice structure

In this contribution, the design of multiband transmission functions is considered. Independent and arbitrary number of bands can be designed. Moreover, the whole transmission function is synthesized by one wave digital lattice structure. The approximation process starts by extracting the scattering matrix properties of multiband reference lattice structures. Consequently, the approximation problem reduces to generating a polynomial Q of degree n, which is the degree of the filter. The degree n is depending on the number of the designed bands. Hence, if the number of bands is even, n will be odd, and if the number of bands is odd, n will be even. The polynomial Q will approximate the difference phase function of the two branch polynomials. It is composed of two subpolynomials, one of them is Hurwitz and the other is anti‐Hurwitz. The degrees of these subpolynomials differ by odd number if the number of bands is even and differ by even number if the number of bands is odd. Q is generated according to iterative interpolation and using explicit recursive formulas. After obtaining Q, the two subpolynomials are calculated and the two branch all‐pass functions are constructed. Consequently, the filter is synthesized in the digital frequency domain. The method is applied through an illustrative example. Copyright © 2011 John Wiley & Sons, Ltd.     

Concatenated Alamouti codes using multi-level modulation and symbol mapping diversity technique

A family of space-time block codes (STBCs) for systems with even transmit antennas and any number of receive antennas is proposed. The new codeword matrix is constructed by concatenating Alamouti space-time codes to form a block diagonal matrix, and its dimension is equal to the number of transmit antennas. All Alamouti codes in the same codeword matrix have the same information; thus, full transmit diversity can be achieved over fading channels. To improve the spectral efficiency, multi-level modulations such as multi-quadrature amplitude modulation (M-QAM) are employed. The symbol mapping diversity is then exploited between transmissions of the same information from different antennas to improve the bit error rate (BER) performance. The proposed codes outperform the diagonal algebraic space-time (DAST) codes presented by Damen [Damen et al. IEEE Transactions on Information Theory, 2002, 48(3): 628–636] when they have the same spectral efficiency. Also, they outperform the 1/2-rate codes from complex orthogonal design. Moreover, compared to DAST codes, the proposed codes have a low decoding complexity because we only need to perform linear processing to achieve single-symbol maximum-likelihood (ML) decoding.     

Multiband sound source localization algorithm for directional enhancement in hearing aids

In order to improve speech comprehension for hearing‐impaired patients under complex scenarios, directional enhancement algorithm based on the sound location will be one of the future research directions. A multiband sound localization algorithm based on auditory bionics is proposed in this paper. First, according to the property of cochlear frequency‐division and hearing‐masking characteristic, the sound is divided into multiband signals. Then, the interaural time differences (ITDs) of the sensitive frequency bands are taken as the localization cues. To improve the location precision, the real ITD is extracted based on the Haas effect. Finally, the HRTF (head‐related transfer function) model is used to convert the ITD to the sound position. To improve the robustness of the algorithm, a multiband weighted strategy is adopted. In addition, a parameter adjustment method is proposed to effectively fit the hearing aid. Simulation and scenario experiments show that the algorithm has strong anti‐interference and high location accuracy. Furthermore, it is designed based on the existing algorithms for hearing aids and has low computation, so it is very suitable for hearing aids and other low‐power real‐time devices. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Design and resonant frequency calculation of rectangular microstrip antennas

This study introduces an original theoretical approach for rectangular microstrip antennas analysis and design. The purpose method consists in the coupling between artificial neural networks tool applied to the analysis of rectangular antennas and a tabu search for the optimization. A neural network acting as database will allow to reduce strongly the computation time. This method will be illustrated in four examples. Copyright © 2010 John Wiley & Sons, Ltd.     

Characterization of coupled finlines by generalized transverse resonance method

The conventional transverse resonance method, which has been widely used for the approximate characterization of a number of guiding structures and leaky wave antennas, is formulated in a generalized form. The transverse resonance viewpoint combined with the generalized matrix representation of discontinuities yields a rigorous transverse equivalent circuit of the guiding structure. This technique is used to compute the characteristics of both symmetrical and asymmetrical double slot unilateral finlines in terms of phase constant and characteristic impedance of the dominant as well as higher-order modes. Numerical aspects of this method are discussed. In a double-slot finline structure, a coupled-mode regime is established with the onset of the first higher-order mode in addition to the dominant quasi-TEM mode. Symmetrical structures are simply modelled in terms of even and odd mode characteristics, but a more general coupled-line model, in terms of the C-mode and the II-mode must be applied to asymmetrical coupled finlines.     

A reconfigurable high ultimate rejection inductorless band‐pass filter by the use of N‐path passive mixers

In this paper, a band‐pass filter with a tunable bandwidth and the center frequency is introduced, which employs N‐path and N × M‐path passive mixer structures, for multiband multistandard wireless receivers. The center frequency of the proposed filter is tunable from 0.1 to 1 GHz, while its bandwidth is also adjustable from 6% to 34% of the center frequency at 100 MHz. The passband ripple is reduced by applying a Miller compensation technique, resulting in a worst‐case ripple of only 1.6 dB over the entire tuning range. An additional eight‐path filter is also utilized at the input of the circuit, which highly improves the out‐of‐band rejection of the filter as well as its out‐of‐band linearity. The noise figure and the input return loss are, respectively, better than 5 and 10 dB, and depending on the desired center frequency, the total power consumption of the proposed filter varies from 41 to 70 mW.