Metamaterial-Inspired Efficient Electrically Small Antennas

Planar two-dimensional (2D) and volumetric three-dimensional (3D) metamaterial-inspired efficient electrically-small antennas that are easy to design; are easy and inexpensive to build; and are easy to test; are reported, i.e., the EZ antenna systems. The proposed 2D and 3D electrical- and magnetic-based EZ antennas are shown to be naturally matched to a 50 source, i.e., without the introduction of a matching network. It is demonstrated numerically that these EZ antennas have high radiation efficiencies with very good impedance matching between the source and the antenna and, hence, that they have high overall efficiencies. The reported 2D and 3D EZ antenna designs are linearly scalable to a wide range of frequencies and yet maintain their easy-to-build characteristics. Several versions of the 2D EZ antennas were fabricated and tested. The measurement results confirm the performance predictions. The EZ antennas systems may provide attractive alternatives to existing electrically-small antennas.     

Design of broad-band and dual-band antennas comprised of series-fedprinted-strip dipole pairs

The design of antennas consisting of two strip dipoles the arms of which are printed on opposite sides of an electrically thin dielectric substrate and connected through a parallel stripline is presented. The antennas are designed to have broad-band or dual-band capability suitable for application in base stations of wireless communication systems. An important advantage of these antennas is their simple structure, allowing them to be readily manufactured as printed circuits. Broad-band antennas with bandwidths greater than 30% for VSWR ⩽1.5 operating near 2.0 GHz and dual-frequency antennas operating at 0.9 GHz/1.5 GHz and 0.9 GHz/1.8 GHz bands are presented     

Multiple-tuned VLF antennas

Different approaches to feeding two multiple-tuned VLF antennas with regard to antenna performance and tuning are compared. Both antennas may be fed separately, or only one may be fed and the other grounded through a previously tuned coil. The antennas may either be connected or separated at their capacitive ends. The maximum bandwidth-efficiency product of all these arrangements is the same. Connected antenna systems achieve this maximum for all adjustments with in-phase base currents, and the most favorable tuning depends on the efficiency desired. If only one antenna is fed, the tuning procedure is quite simple, because only current magnitudes have to be adjusted. Retuning of the coils in the nonfed upleads is not necessary if changes are small compared with the magnitude of the antennas' coupling reactances. Connected element systems are particularly stable. These properties can be transferred to other multiple-tuned antenna systems of electrically short elements with top capacitances     

A Hybrid Method of Moments?GTD Technique for Computing Electromagnetic Coupling Between Two Monopole Antennas on a Large Cylindrical Surface

The problem of analyzing the electromagnetic interference (EMI) between two electronic systems when their antennas are located on or near large scattering objects is a difficult one. In this paper, a hybrid technique for combining the method of moments with the geometrical theory of diffraction (GTD) is extended to account for the mutual coupling between two monopole antennas on a large circular cylinder by means of curved surface-wave diffraction. The results of this technique are compared to those of an analysis program used by the United States Air Force which predicts electromagnetic coupling between aircraft antennas. The close agreement between the results of these two different analysis techniques serves to validate both computer programs.     

The influence of electromagnetic environment on operation of activearray antennas: analysis and simulation techniques

This paper presents an overview of active array antennas, system-level nonlinear effects in such antennas, and their modeling and simulation techniques. Advantages of active array antennas, in comparison with passive array antennas, are discussed. The influence of nonlinear distortions and interference in active antennas on the overall system performance is considered. Modeling and simulation techniques that can be applied to active array antennas are substantially different from those used for circuits and systems. Analytical and numerical techniques are used for the analysis of active antennas, with the prevailing use of numerical techniques at the present time. Electromagnetic-level and circuit-level simulation techniques are discussed. System-level simulation techniques are considered in detail, with special emphasis on their application to active array antennas. The “instantaneous” quadrature technique is proposed as an effective tool for numerical simulation of active arrays over wide frequency and dynamic ranges in a computationally-effective way     

Perturbations radioélectriques dans le réseau téléphonique local français

High power low and medium frequency broadcasting radio transmitter antennas induce high level perturbing voltages on adjacent local networks. New electronic telephone systems are particularly sensitive to these perturbations. The purpose of this paper is to demonstrate the sensitivity of local networks and subscriber systems to parasitic voltages and to provide solutions for their elimination.     

ESPAR array design for the UHF RFID wireless sensor communication system

In this paper, in order to improve the received signal strength (RSS) and signal quality, three arrays of electronically steerable parasitic array radiator (ESPAR) antennas are suggested for the ultra-high frequency (UHF) radio frequency identification (RFID) communication and sensing system applications. Instead of the single antenna, the array antennas have recently been widely used in many communication systems because of their peak gains, better radiation patterns, and higher radiation efficiency. Also, there are some important issues to use the antenna array like high data rates in wireless communication systems and to better understand the many targets or sensors. In this article, a wireless sensor network (WSN) is being investigated to overcome multipath fading and interference by antenna nulling technology that can be achieved through beam control ESPAR array antennas. The proposed ESPAR array antennas exhibit higher gains like 9.63, 10.2, and 12 dBi and proper radiation patterns from one array to another. Moreover, we investigate the mutual coupling effect on the performance of array antennas with different spacing (0.5λ, 0.75λ, λ) and configurations. It is found that the worst mutual coupling reduced by −28 to −34 dB for 2 × 2 array, −3 to −43 dB for 2 × 3 array, and finally −42 dB to −51 dB due to the antenna spacing from 0.5λ to λ. Thus, these suggested antennas could effectively be applied in the WSN communication systems, internet of things (IoT) networks, and massive wireless and backscatter communication systems.     

Transmit-preprocessing techniques with simplified receivers for the downlink of MISO TDD-CDMA systems

Time-division-duplex code-division multiple-access (TDD-CDMA) systems have recently gained attention with their inclusion in third-generation mobile systems. In this paper, we introduce two optimized transmit preprocessing techniques to reduce multiple access interference in the downlink of TDD-CDMA systems with multiple transmit antennas that are employed at the base station (BS). In these systems, signal preprocessing is performed at the BS, so that a simplified receiver structure that consists of a one-finger correlator can be utilized at the mobile station. Analytic solutions for both of the optimized transmit preprocessing techniques are derived by minimizing the transmit mean square error. Numerical results are also provided, which demonstrate significant performance improvement when compared to the conventional RAKE system and the pre-RAKE maximum ratio combining transmit diversity system. In particular, transmit antennas can be used to increase the system capacity.     

High-rate codes that are linear in space and time

Multiple-antenna systems that operate at high rates require simple yet effective space-time transmission schemes to handle the large traffic volume in real time. At rates of tens of bits per second per hertz, Vertical Bell Labs Layered Space-Time (V-BLAST), where every antenna transmits its own independent substream of data, has been shown to have good performance and simple encoding and decoding. Yet V-BLAST suffers from its inability to work with fewer receive antennas than transmit antennas-this deficiency is especially important for modern cellular systems, where a base station typically has more antennas than the mobile handsets. Furthermore, because V-BLAST transmits independent data streams on its antennas there is no built-in spatial coding to guard against deep fades from any given transmit antenna. On the other hand, there are many previously proposed space-time codes that have good fading resistance and simple decoding, but these codes generally have poor performance at high data rates or with many antennas. We propose a high-rate coding scheme that can handle any configuration of transmit and receive antennas and that subsumes both V-BLAST and many proposed space-time block codes as special cases. The scheme transmits substreams of data in linear combinations over space and time. The codes are designed to optimize the mutual information between the transmitted and received signals. Because of their linear structure, the codes retain the decoding simplicity of V-BLAST, and because of their information-theoretic optimality, they possess many coding advantages. We give examples of the codes and show that their performance is generally superior to earlier proposed methods over a wide range of rates and signal-to-noise ratios (SNRs)     

Monolithic semiconductor antennas for millimeter wave Si and GaAs integrated circuit technologies

It has been reported that the radiation characteristics of semiconductor antennas can be controlled by modulating their conductivity during fabrication and/or operation. This paper describes novel physical layouts integrating these versatile antennas with other components used in the realization of millimeter wave systems. The monolithic integration is discussed for GaAs as well as Si IC technologies.     

Ground antennas in NASA's deep space telecommunications

Ground antennas are the major visible components of NASA's Deep Space Network (DSN). The role, key characteristics, and performance of these antennas in deep-space telecommunications are described. The system analyses and tradeoffs to optimize the overall ground-to-spacecraft link and to define future missions are elaborated from an antenna perspective. Overall performance of receiving systems is compared using the widely accepted G/T figure-of-merit, i.e., net antenna gain divided by the operating system noise temperature. Performance of past, present, and future antennas and receiving systems is discussed, including the planned development of a world-wide network of 34-m diameter beam-waveguide antennas. The need for multifrequency operation, presently in the S- and X-bands, and in the future in the Ka-band, is discussed. The resulting requirements placed on antenna technology are highlighted. Beam-waveguide antenna performance to further improve performance and operational advantages is discussed     

Modeling of fractal antennas

Results on the numerical analysis of the Sierpinski and Koch fractal antennas are presented. It is shown that self-similarity of fractal structures affects electromagnetic properties of antenna structures created on the basis of these fractals. It is demonstrated that the Sierpinski and Koch fractal antennas are multiband structures; therefore, these antennas can be used for the development of radar and telecommunications systems. A technique is proposed for generation of an irregular determinate fractal structure that can be used for the development of a frequency-independent fractal antenna.     

Computer-algebra systems and electromagnetic problems

This paper presents some computer-algebra systems, and explains how these systems are likely to be relevant in addressing electromagnetic problems. After a historical survey, we discuss the various systems and their features. Some examples are given, with an important bibliography. A listing of Web sites (of interest to the antennas and propagation community) is also given. Finally, we outline how a given problem can be formalized and analyzed using symbolic-algebra systems, and show an example calculation for a conformal-microstrip antenna     

FDTD分析探地雷达天线的辐射特性

探地雷达系统一般采用超宽带短脉冲信号,因而其天线系统必须具有较好的宽带性能。只有几种类型的宽带天线能够用于探地雷达系统中,如电阻加载的蝶形天线、TEM喇叭天线及其变形形式。本文将给出一种新型的探地雷达天线,该天线为置于镜像面上且具有离散指数电阻加载的单偶极子。文中将采用FDTD计算和分析该天线在自由空间和有耗媒质上方时的辐射特性。结果表明,通过选择一定的电阻加载形式,可使天线具有较好的辐射波形,从而能够满足实际探地雷达的需要。最后,通过地下目标散射场的理论结果和实验结果说明了本文所采用方法的正确性。     

UWB天线的宽带化技术及其发展

在现代通信技术中,为了实现通信保密、排除干扰、提高通信效率等,超宽带系统得到了大力发展,然而,在一定程度上却受制于系统中超宽带天线的阻抗带宽。详细介绍了展宽天线阻抗带宽的4种方法,包括渐变阻抗方法、分形几何方法、微带天线开槽方法和非频变结构方法,其中分形几何方法由于其几何结构的自相似性使得其贴片电流分布具有自相似性,从而导致天线的多频点谐振,有效拓展了天线带宽。上述4种天线尽管作用原理互不相同,但在超宽带天线的工程应用中,研究者可将这些方法单独或同时应用于天线结构设计,使得天线既能保持良好的方向性和增益等性能,又能获得较大带宽。     

Exploiting Multipath Diversity in Multiple Antenna OFDM Systems With Spatially Correlated Channels

Multiple antennas are useful in orthogonal frequency division multiplexing (OFDM) systems for providing transmit and receive diversity to overcome fading. Typically, these designs require considerable separation between the antennas. Spatial correlation is introduced when antennas are not well separated, and it often leads to performance degradation in a flat fading environment. However, in frequency selective fading channels with rich multipath diversity, OFDM receivers can overcome this performance degradation due to antenna correlation. This is due to transformation of a highly spatially correlated channel impulse response to a less spatially correlated channel frequency response inherently by an OFDM system in the presence of rich multipath diversity. We illustrate this for a simple receive diversity OFDM system and hence introduce the concept of space sampling at the receiver where antennas are placed relatively close to each other. The minimum separation required between the antennas under such circumstances is derived analytically, and it is shown that even with a separation of only$0.44lambda$, the required spatial correlation in the channel frequency response becomes sufficiently low. Simulated performance results with such spacing for various multiple antenna OFDM systems corroborate the analytical results.     

A discussion on the properties of electrically small self-resonant wire antennas

The performance properties of several electrically small, self-resonant wire antennas are compared as a function of their total wire length, geometry, and effective volume. The radiation properties considered include resonant frequency, radiation resistance, and quality factor (Q). It is shown that the resonant properties of these antennas are directly a function of the antenna's effective height and effective volume, which are established by both total wire length and geometry. When the total wire length and geometry of these antennas are configured such that the antennas exhibit the same effective height and volume, their resonant properties are essentially identical, independent of any differences in their total wire length and geometry. Both computed and measured data are presented to support the comparison of the antennas' resonant properties.     

Why have smart antennas not yet gained traction with wireless network operators?

Many research and development activities have been poured into developing smart antennas for wireless communications systems. Yet despite the promise of increased network capacity and enhanced spectrum utilization, smart antenna systems have largely failed to break into the mainstream cellular networks, as operators have balked at adopting these technologies. This article examines some of the reasons why smart antennas have historically been met with resistance, and suggests that provided some identified obstacles are overcome, the proliferation of certain types of smart antennas is imminent.     

Model Scenarios for Direction-Selective Adaptive Antennas in Cellular Mobile Communication Systems – Scanning the Literature

Intelligent antennas offer the possibility of greatly increasing the capacity of cellular mobile radio systems. We give a comprehensive overview of the literature concerning model scenarios for applications of direction-selective intelligent antennas. Measurement campaigns and simplified models are described that have been derived from these measurements or from physical considerations. Furthermore, directional fading simulators are reviewed which are essential for testing of smart antenna systems.     

Research on planar antennas and arrays: `structures Rayonnantes'

The basic research on radiowave systems dealing with electromagnetism, electronics, and signal processing at the University of Rennes is discussed. The fusion of these different domains occurs for studies concerning systems where radiating structures, active devices and interfaces, and signal processing play a fundamental role and cannot be separated. Different geometries and methods developed for various types of patches, dipoles, and slot antennas, including patch antennas with coaxial or microstrip feeds, printed slot antennas, slot-fed patches, slot-loaded patches, and electromagnetic coupled dipoles and patches, are described. Different kinds of arrays have been designed with active or passive feed networks. The analysis includes mutual-coupling effects, especially when beam steering is considered with small element spacing. Arrays considered include planar phased arrays, planar passive arrays, dual-beam printed antennas, and arrays of microstrip dipoles