Aperture-coupled, differentially-fed planar inverted F antenna

A differentially-fed single aperture is used to excite an unsymmetrical antenna contactlessly. The current maximum below the aperture is generated by an odd-mode signal, rather than an open-circuit stub. Simulated and measured 0.9 GHz results, with a planar inverted F antenna, suggest potential applications in mobile communication systems.     

Millimeter-wave antennas

With the continually increasing demand for bandwidth, and the development of components for higher and higher frequencies, millimeter-wave systems are finding numerous applications of a commercial nature rather than being limited to military and scientific applications only. Since active device performance deteriorates with increasing frequency, the performance of the antenna becomes critical as we go higher into the millimeter-wave band. This paper presents a review of some of the recent developments in the field of millimeter-wave antennas. Finally, some details of a specific antenna for imaging are given, illustrating the benefits and challenges of fabricating such antennas.     

FDTD analysis of noise radiation and propagation

The analysis of effects from noise illumination of electrical and electronic systems is complicated by stochastic rather than deterministic variables. An analysis technique is presented for noise propagation, where the noise is modeled as a time series of discrete time impulses with amplitudes computed by a white Gaussian noise simulation. Using the noise source to simulate the drive of an appropriate antenna, the analysis of the radiated noise signal is accomplished through the use of the finite-difference time-domain (FDTD) formulation. The presented technique is verified by a comparison with the results obtained from using the method of moments and a wire antenna radiator. In addition, limitations, stability, and applicability of the presented formulation are discussed     

Radial line planar monopulse antenna

In recent years, mobile satellite communications have been growing rapidly. Monopulse tracking operations for beam pointing to the satellite are often employed for those systems which, in general, require rather severe EIRP and G/T specifications. Thus, the development of a monopulse antenna with a good antenna efficiency is of great interest. A radial line planar monopulse antenna is proposed. An analysis of the probes in a radial line has been carried out which gives an understanding of why the monopulse patterns can be synthesized, and a simple and effective theory is presented about a realization of uniform-aperture field distribution. The antenna has been fabricated and the radiation characteristics have been measured which supports the theory as well as verifies the capability of the antenna for the monopulse tracking operation     

Physical optics and field-strength predictions for wireless systems

Physical optics, or Fresnel-Kirchhoff theory, is often used for studies of particular problems in terrestrial radio-wave propagation. With efficient techniques of numerical integration, it can also be used effectively for routine predictions and for designing terrestrial wireless systems. A computer program of this type has been in use for several years. It is most useful in situations in which the base station (BS) antenna is above local clutter, and over areas large enough that ground cover can be characterized with categories such as "open," "forest," "dense residential," etc., rather than individual buildings. The main calculation is a marching algorithm that simulates diffraction over all the variations in terrain height along radials from the BS. A secondary calculation estimates the additional attenuation due to buildings and trees close to the mobile antenna. This part of the calculation is based on several parameters characterizing the local environment of the mobile antenna. Calculations are slow compared to many traditional methods, but are fast enough for routine use on a PC     

Tradeoffs in the design of a spaceborne scanning pencil beamscatterometer: application to SeaWinds

SeaWinds is a spaceborne wind scatterometer to be flown on the second Japanese Advanced Earth Observing Satellite (ADEOS-II) in 1999. An important international element of NASA's Earth Observing System (EOS), SeaWinds is an advanced follow-on to the NASA scatterometer (NSCAT) on the first ADEOS platform. Unlike previous operational spaceborne scatterometer systems. SeaWinds employs a scanning “pencil-beam” antenna rather than a “fan-beam” antenna, making the instrument more compact and yielding greater ocean coverage. The goals of this paper are twofold. First, the overall SeaWinds functional design and backscatter measurement approach are described, and the relative advantages of the pencil-beam technique are outlined. Second, the unique aspects of measurement accuracy optimization and signal processing for the SeaWinds instrument are discussed. Applying the results of a separate companion paper, ibid., 1997, a technique to significantly improve measurement accuracy by modulating the transmit pulse is described. Trade-offs to optimize the transmit modulation bandwidth are presented     

Antenna systems for broadband wireless access

Broadband wireless access along with evolving mobile Internet and multimedia services are driving the surge of research and development activities for future wireless communication systems. We provide an overview of antenna systems for broadband wireless communications and introduce some of the important issues surrounding them. The approach we use is to first provide a general framework of how antenna systems may be utilized in wireless communication systems and then describe the antenna systems themselves. In particular, we consider antenna systems for the base station, mobile station, and then finally multiple-input multiple-output antenna systems where antenna systems are utilized at both the base and mobile stations     

Miniaturized biocompatible microstrip antenna using genetic algorithm

Biocompatible antennas are an area of recent research that can facilitate remote communication with medical implants. This paper shows several possible designs of a "waffle-type" antenna created using genetic algorithms (GAs) that are of a size potentially suitable for cardiac pacemakers in the 402-405 MHz MICS band. In addition, methods to constrain the simulation and speed up the convergence of the GA for this type of antenna are explored. Even simple constraints such as fixing the feed and ground locations and encouraging the antenna to grow preferentially in the horizontal direction to take advantage of the longer physical dimensions of a pacemaker in that direction can appreciably improve convergence speed. One exception to this was constraining the patches to be connected together rather than distributed randomly, which caused the system to converge slower rather than faster. Also notable was that when a larger physical size was allowed, the system also converged more quickly despite a sizeable increase in the number of unknowns (subpatches) in the model. Thus, this paper provides a smaller, better matched microstrip antenna for biotelemetry and a choice of GA constraints for designing it.     

On Electromagnetics and Information Theory

Some connections are described between electromagnetic theory and information theory, identifying some unavoidable limitations imposed by the laws of electromagnetism to communication systems. Starting from this result, the role of the degrees of freedom of the field in radiating systems is investigated. Different classes of antennas use the available degrees of freedom in different ways. In particular, a multiple-input multiple-output antenna is a radiating system conveying statistically independent information on more than one degree of freedom of the field. Applications of the theory to antenna synthesis and antenna characterization in complex environments are shown.     

Comparisons of a computer-based propagation prediction tool withexperimental data collected in urban microcellular environments

Engineers designing and installing outdoor and indoor wireless communications systems need effective and practical tools to help them determine base station antenna locations for adequate signal coverage. Computer-based radio propagation prediction tools are now often used in designing these systems. We assess the performance of such a propagation tool based on ray-tracing and advanced computational methods. We have compared its predictions with outdoor experimental data collected in Manhattan and Boston (at 900 MHz and 2 GHz). The comparisons show that the computer-based propagation tool can predict signal strengths in these environments with very good accuracy. The prediction errors are within 6 dB in both mean and standard deviation. This shows that simulations, rather than costly field measurements, can lead to accurate determination of the coverage area for a given system design     

平流层通信及相关技术

蜂窝和个人移动通信系统（ＰＣＳ）需要大量广布的天线塔、基站、有线或微波线路，卫星通信系统地面设施相对较少，但ＧＥＯ系统的用户终端笨重且昂贵，信号时延大；ＭＥＯ和ＬＥＯ卫星相对于地面的快速运动使系统的构成和控制复杂化，并且卫星发射和维护费用高，高空航空平台（ＨＡＡＰ）无线通信系统（即平流层通信）实为折衷方案，本文讨论了此类通信系统的特点和实现的可能性。     

Dual-frequency planar inverted-F antenna

Cellular telephone handsets are now being designed to have dual-mode capabilities. In particular, there is a requirement for internal antennas for GSM and DCS1800 systems. This paper describes a novel planar dual-band inverted-F antenna for cellular handsets, which operates at the 0.9-GHz and 1.8-GHz bands. The dual-band antenna has almost the same size as a conventional inverted-F antenna operating at 0.9 GHz and has an isolation between bands of better than 17 dB. The bandwidths of the antenna are close to those required for the above systems. Good dual-band action is also obtained for other frequency ratios in the range of 1.3-2.4. Studies also show that the dual-band antenna can operate with one or two feeds. A finite-difference time-domain analysis has been shown to give calculated results close to those measured     

Emission Reduction and Capacity Increase in GSM Networks by Single Antenna Interference Cancellation

There is an increasing demand to utilize the frequency spectrum of mobile communication systems most efficiently. This means in particular to GSM networks that the frequency reuse shall be planned as low as possible. In this case the system may become limited by interference rather than coverage. One promising technology for GSM mobiles in interference-limited systems is single antenna interference cancellation (SAIC). This receiver technology allows both for increasing the network capacity and for reducing the base station transmit power. The aim of this paper is to assess the emission reduction as well as the system capacity capabilities when SAIC technology is applied in downlink receivers.     

天线时延标定在卫星导航技术中的应用

卫星导航系统通过信号传播时延的测量来实现定位、导航和授时,信号传播时延测量计算需要已知天线时延,天线时延标定准确度是影响系统服务精度的关键因素。叙述了卫星导航系统中天线时延的定义及通常测量方法,提出了2种利用卫星导航系统自身测距能力的天线时延标定方法,介绍了天线相位中心测量方法,并给出了卫星导航系统应用中的天线相位中心点坐标的归算方法。     

Antenna Array Structures Effect on Water-Filling Capacity of Indoor NLOS MIMO Channel

1 Introduction Digital communication using MI MO has recently e-merged as one of the most significant technical break-throughs in modern wireless communications .Foschini ,Telatar and others saythat the capacity can beincreasedlinearly with the mini mum antenna numbers of thetransmitter and receiver if the scattering environment isrich and there is no correlation between the antennapairs at the transmitter and the receiver[1 ~2]. Toachieve these capacities coding techniques such asBLAST an…     

On the efficiency and radiation patterns of mismatched shaped Cassegrainian antenna systems

Calculations are carried out with regard to the aperture illumination efficiency, spillover efficiency, and blockage efficiency of a shaped Cassegrainian antenna system whose feed pattern is not similar to that for which the antenna was designed. It appears that a maximum overall efficiency may be expected for antenna systems with a feed pattern having a slightly narrower beamwidth than those for which the systems were originally designed. It is further proved that the radiation pattern of mismatched systems is very unfavorable in the case of the beamwidth of the feed pattern being wider than the beamwidth of the feed pattern for which the system was designed. This is due to overillumination of the edges.     

目前临床医用微波辐射器的缺陷与改进方向的研究

利用蛋清凝固热图实验和漏能功率仪测量，分析了不同的医用微波辐射器的能量分布，指出单极子天线根部辐射能量较大，顶部较弱，不适宜作为医用微波体内辐射器，而实验显示螺旋型天线在靠近顶部时是最强的，辐射能量集中而有效，实验结果和多例临床应用证明：螺旋型天线稳定、高效、安全，在临床上用有着广泛的应用前景，建议螺旋型天线代替单极子天线作为研究方向。     

一种具有双阻带特性的超宽带单极子天线设计

为克服无线通信中系统间的相互干扰,采用频带抑制技术设计了一种具有双阻带特性的超宽带单极子天线。首先采用共面波导进行馈电,辐射贴片和共面波导均为阶梯结构,使其在2.9～12GHz频带内电压驻波比小于2;其次在辐射贴片上分别引入C形和倒U形槽谐振结构,使其在3.3～3.9GHz和5.1～5.9GHz的频带内电压驻波比大于2;最后通过仿真与测量,验证该天线实现了良好的频带抑制功能。     

Multipath-rejecting GPS antennas

Multipath interference limits the speed and accuracy of determining position by differential Global Positioning System (DGPS) techniques. A geodetic surveyor for example, requires multipath interference rejection of about 36+20log₁₀sinϵ dB, where ϵ is the elevation angle of the satellite being observed. Signal processing in a GPS receiver cannot satisfy this requirement. A receiving antenna is required that can sufficiently reject signals arriving from below the horizon. Available antennas have inadequate rejection, and brute-force methods of improving them, e.g., by enlarging their ground-planes, are impractical. A compact, ground-planeless, dual-band GPS antenna with improved multipath rejection has been designed and field-tested. This antenna resembles a vertical post rather than a horizontal platter; within its 0.1-m diameter, 0.4-m tall randome is a vertical array of turnstile elements. In field tests, a three-element array antenna rejected multipath better than a 0.5-m diameter ground-plane antenna by an average of 5 dB. A five-element array antenna appears superior to a 0.9-m diameter ground-plane antenna     

Ka波段旋转关节的设计

旋转关节是天线馈电系统中的重要器件。从理论入手,阐述了一种Ka波段单通道旋转关节的设计方法,在理论设计的基础上经过计算机仿真进行参数优化,得到最佳值,并以此数据为参考设计出此旋转关节实物。对这个实物旋转关节作了大量调试试验工作,测试结果与仿真结果基本一致。驻波的频率特性符合切比雪夫函数规律,良好的驻波比特性,因此这种旋转关节在天线馈电系统中有着广阔的应用。