基于优化多带复小波变换的MC-CDMA/TDD下行链路分析

提出一种基于优化多带复小波变换的MC-CDMA系统,研究了其在多径瑞利衰落下的性能。并采用TDD模式下的简化接收机结构和实现复杂度,增强了系统的抗多径和多址干扰(MAI)的能力。理论分析和仿真结果均表明该系统具有可行性,有着良好的抗衰落能力。     

传感能力约束下的认知无线网络的多波段光谱感应优化

This paper addresses the problem of joint optimization of subchannel selection and spectrum sensing time for multiband cognitive radio networks under the sensing capability constrains. In particular, we construct a multiband spectrum sensing framework, and derive the probabilities of detection and false alarm taking the different subchannel gain into account. Furthermore, we formulate the multiband sensing as a two-parameter optimization problem under the sensing capability constrains and guaranteeing the QoS of the secondary user. Moreover, we develop a semi-analytical optimization scheme to achieve the optimal solution.     

分形天线多频性及应用探讨

将分形几何应用于天线设计,其自相似性会使得天线具有多频性从而增加天线的带宽.本文主要从仿真模拟和实际测试研究了基于以Minkowski为边界的微带分形天线.分形天线的多频性,可以应用于调频同频通讯等方面.     

Low profile single feed monopole antenna for quad-band circularly polarised applications

ABSTRACT

A single fed monopole antenna for circularly polarised quad-band applications is presented. The antenna radiator is comprised of half ring-shaped arcs integrated with the 50Ω microstrip feed line. In the proposed design, the circular polarisation is achieved by means of integrating ring, stubs and implanting an open-ended C-shaped slot in the ground surface. The designed antenna has a ?10 dB impedance bandwidth in the range of 2.41 GHz to 4.14 GHz and 4.34 GHz to 6.33 GHz. The 3-dB axial ratio bandwidth varies from 3.01 to 3.21 GHz, 3.46 to 3.79 GHz, 4.53 to 4.68 GHz and 5.08 to 5.10 GHz, therefore, exciting four circularly polarised bands. The proposed antenna covers almost all the IEEE 802.11 and IEEE 802.16 standards and may be a suitable candidate for WLAN and WiMAX applications. The optimisation of the designed antenna is conducted using tool Ansys HFSS and found simulated results in a good match with measured results.     

面向一类多频滤波功分器的通用综合设计方法

提出了一种通用的新型多频带滤波功分器综合设计方法,该方法在工业领域和学术领域都具有潜在的应用前景。首先建立了一套完整的闭环解析方程并进行直接综合设计,然后详细展示了所提出的方法在设计任意预设滤波响应(如任意阶数、频带数等)的多频带滤波功分器时的能力,所设计的滤波功分器具有良好的隔离和匹配。因此,该综合方法可以为现代无线通信系统中的多频带滤波功分器提供有效统一的设计指导。设计并制作了三阶双频和三阶三频微带滤波功分器模型作为实例,并进行了测试。测试结果与仿真结果吻合较好,从而验证了所提出的综合设计方法的可行性和所设计的多频带滤波功分器的良好性能。     

新型多波段复合植被伪装材料

为满足多波段兼容伪装的需求,采用多种材料合理匹配与多功能层组合结构的方法,制备了一种可实现可见光、红外和雷达多波段兼容的新型复合植被伪装材料.用雷达波屏蔽效能和反射率测试实验对伪装材料的吸波性能进行了测试,用成像法对伪装材料的可见光和热红外伪装性能进行了试验检测.结果表明,研制的伪装材料有良好的雷达波衰减性能,大于5 ...     

多模多带软件无线电的技术要点和解决方案

文章介绍多模多带软件无线电技术的发展现状,指出移动通信领域对这一技术 的高度期盼,并对其中一些可接受技术提出相应的解决方案。     

The Role of Odd-Frequency Pairing in Multiband Superconductors

Recent progress in the understanding of multiband superconductivity and its relationship to odd-frequency pairing are reviewed herein. The discussion begins by reviewing the emergence of odd-frequency pairing in a simple two-band model, providing a brief pedagogical overview of the formalism. Several examples of multiband superconducting systems are examined, in each case describing both the origin of the band degree of freedom and the nature of the odd-frequency pairing. Throughout, it is attempted to convey a unified picture of how odd-frequency pairing emerges in these materials and propose that similar mechanisms are responsible for odd-frequency pairing in several analogous systems: layered 2D heterostructures, double quantum dots, double nanowires, Josephson junctions, and systems described by isolated valleys in momentum space. In addition, experimental probes of odd-frequency pairing in multiband systems are reviewed, focusing on hybridization gaps in the electronic density of states, paramagnetic Meissner effect, and Kerr effect.     

Asymmetrical mirror imaged monopole antenna with modified ground structure for DBDP radiations

ABSTRACT

In this article, asymmetrical mirror-imaged monopole antenna comprises a rectangular patch with tuneable stub and supported with modified ground structure (MGS) is investigated. The proposed antenna is characterised for dual band dual polarised (DBDP) radiations and can operate at 2.45 GHz for Wi-Fi and WLAN systems (2.4–2.485 GHz) and 5.45 GHz for WLAN band (WLAN band: 5.2–5.8 GHz) with the corresponding polarisations. A rectangular patch integrated with tuneable stub and a pair of asymmetrical inverted L-shaped slots positioned at ground plane is responsible for circularly polarised higher band; while a parasitic patch is created due to slotting of a mirror-imaged stub from the extended ground plane which is accountable for lower frequency band. The fabricated prototype shows that the measured Impedance bandwidths (VSWR < 2) are 350 and 1770 MHz for lower and higher frequency bands, respectively. The measured axial ratio bandwidth (AR < 3 dB) is yielded as 1450 MHz centred at 5.44 GHz for higher frequency band. The peak gains are measured as 4.3 and 4.15 dB for lower and higher frequency band, respectively. For the prototype antenna, substantial 3-dB beamwidth is found along with good cross polarisation suppression.     

基于优化多带复小波的多载波CDMA及反向链路性能

在分析多载波码分多址的原理基础上,利用优化生成的多带复小波,提出了一种基于优化多带复小波的多载波CDMA系统反向链路模型,并采用基于多天线的空间分集合并(SDC)技术进一步完善所提系统.该系统可利用优化多带复小波的优良特性来避免通常多载波CDMA由于插入循环前缀所带来的频谱效率的下降,在此基础上我们研究了所提系统采用空间分集合并技术时在瑞利衰落信道下的反向链路性能;给出相应的误比特率分析.理论分析和仿真结果表明采用基于最大比合并的SDC技术可显著提高所提系统抗空间衰落和各种干扰的能力,而且基于SDC技术的所提系统要好于同样基于SDC技术的通常多载波CDMA系统和基于实小波包的多载波CDMA系统.