短波多径环境中一种DOA方法

短波通信存在着多径衰落和干扰的问题,影响了通信的质量。通过使用智能天线,可以提高通信质量和可靠性。但是短波多径环境中会产生多个相干信号,造成智能天线的波达方向（DOA）识剥模糊。本文利用短波信号的循环平稳特性,结合均匀线性阵列,提出了在短波环境中识别DOA的前向空间平滑Cyclic Music方法。     

短波数据信号传输抗干扰技术的研究

短波通信因其具有通信距离远、抗毁能力强、机动灵活等优点，一直是军方和海上移动通信的主要手段之一，但是短波信道是一个时变信道，信道衰落和各种干扰比较严重，因此如何在这样的信道中准确、快速地传输数据，这是人们一直关心的问题。本文根据短波信道的这一特点，采用跳频抗干扰技术，以提高抗信道多径干扰和信号衰落性干扰性能。     

短波干线通信接收机的阻塞现象

一、概述近年来,短波频段使用的日趋拥挤,发射功率的日益增高,使接收机往往不得不处在与信号频率相距极近的强干扰条件下进行工作.这些干扰频率虽处在接收机通频带之外,但因前几级电子管受强干扰作用而处于非线性状态下工作,往往会引起信号阻塞、交叉调制等附加干扰.短波干线通信的距离极长,加上短波传播中经常有的衰落现象等,这就确定了短波干线通信接收机必须是高灵敏度的,显然,这种高灵敏度接收机是更容易     

广域分集技术在短波通信中的研究及应用

由于短波信道的时变性和多径性,信号经过短波信道到达接收端会受到严重的衰落,分集接收技术是抗信道衰落最有效的措施之一。文中针对短波通信特点提出了一种广域分集方法,对三种常用的分集合并方式的性能进行仿真分析,并在实际通信中进行了验证。     

短波宽带信道中噪声与干扰建模

短波通信系统依靠电离层传播,具有通信距离远,灵活性高,抗干扰性强,成本低廉等特点,是一种重要的国防军事通信手段。传统短波通信受电离层特性影响而有效带宽较窄,导致数据传输速率极低。因此,提高信道容量实现高速数据传输的短波宽带通信系统越来越受到重视。短波宽带信道建模是短波宽带通信系统正常发挥性能的关键,对短波宽带通信系统的设计与实际应用具有重要的实际意义。结合现有短波宽带信道的衰落特性模型,介绍了短波宽带信道噪声和干扰模型,并进行了比较和可靠性分析,发现现有模型形式比较单调统一,但和实际测量数据一致,能有效描述短波宽带通信中信道噪声与干扰特性,模型已经比较完善。最后,提出了进一步研究的重点方向。     

短波宽带通信系统中LDPC码的应用分析

针对短波宽带信道时变衰落色散的特性,为减小多径效应以及空间噪声、干扰等不利因素的影响,改善短波通信质量,采用高效纠错编码LDPC码,结合扩频OFDM技术,设计了一种适用于短波宽带信道的编码调制系统结构,仿真结果显示：系统能够显著提高短波宽带通信系统的误码性能,为短波宽带通信提供了一种可靠、有效的设计方案。     

短波自适应通信技术理论研究

在通信技术发展日新月异的背景下,短波通信凭借着自身特有的范围广、灵活性好、顽存性强等优势,通过创新实时信道估值理念,实时扫描测量多信道关键参数包括信噪比、多径延时和误码率,逐步发展完善了短波自适应通信技术.这一创新性技术克服了传统短波通信的弱点,提高了通信的质量和效率,有效改善了信号衰落现象,克服了"静区"效应,提高了短波通信抗干扰能力,并拓展短波通信业务范围.     

短波通信的新技术——自适应与跳频

短波通信实际上是天波通信,而天波通信中,电波比较深入地进入电离层,因此受电离层变化的影响较大,信号很不稳定,即使按常规选择频率,同时确保天线方向架设的准确,有时仍然会发生收不到信号、信号时强时弱及受其他信号干扰等现象。为此短波自适应跳频技术的出现,较好地解决了短波通信质量受电离层变化及其他干扰的影响,使短波通信质量有了提高。     

短波通信中分布式干扰的效能分析

在短波通信中,分析分布式干扰应用,深入分析分布式干扰设备组成、关键技术,随机二维码调制信号.应用Matlab软件模块,对分布式干扰系统进行分析,采用随机二元码,调制信号对短波通信系统的干扰影响.通过仿真结果可知,分布式干扰能够获取显著干扰效果.在本文研究中,围绕短波通信展开讨论,重点分析分布式干扰的效能问题,仅供参考.     

短波电离层反射信道模型的建立与仿真

工作在短波波段的电子战设备进行天波通信时,会受到电离层高度变化和多径传播的影响,使信号产生多普勒展宽和多径时延,表现为时间选择性衰落和频率选择性衰落,严重影响信号质量.本文介绍了短波电离层反射信道对信号的影响,推导出信道的理论模型,提出了实现方案,并利用systemview进行了信道仿真,结果表明,该模型基本上反映了短波信道的特点.     

Submillimeter wave communication versus millimeter wave communication

This paper studies the performance of a submillimeter wave antenna operating between frequencies 0.1 THz and 10 THz with a 4-cyano-4-pentylbiphenyl [5CB] substrate. Since the size and shape of the antenna impact its gain/directivity, resonant frequency, bandwidth, and efficiency, the two antenna types considered in this paper are: (a) Rectangular Patch Antenna (RPA), and (b) Cylindrical Dielectric Resonator Antenna (CDRA). Here a submillimeter wave antenna is compared with a millimeter wave (a few GHz to 100 GHz) antenna. These popular mm-wave antennas are chosen for the submillimeter wave antenna in order to understand changes in their performance as the result of changes in their geometrical shape. FEldberechnung bei Korpern mit beliebiger Oberflache (FEKO) software is used for the design and calculation of the Three-Dimensional (3D) ElectroMagnetic (EM) patterns. This paper also concentrates on the design and analysis of a massive submillimeter wave Multiple-Input Multiple-Output (MIMO) (8 by 8) RPA and CDRA.     

波浪浮标测波方法比较

波浪浮标是一种无人值守,自动检测的常用的海洋监测设备。在介绍国内外波浪浮标研究使用现状的基础上,对比分析了基于加速度传感器和GPS传感器的两种波浪浮标的共同点和不同点。     

Nonlinear wave propagation in traveling–wave amplifiers

A method is given for computing the efficiency of traveling-wave amplifiers with high gain and low C, including the effects of space charge and attenuation. The ballistics of the electrons is governed by the Boltzmann transport equation which, together with the circuit equation, is solved in a power series expansion of the input voltage. Only the first two terms of this series are computed and various nonlinear results are given in the form of curves. It appears that for small C and small convergence parameters, overtaking affects the nonlinear operation slightly.     

矩形波导中电磁波传输特性研究

本文基于功率流分别讨论了在矩形波导横截面积一定,TEm0和TMmn模式单独传输时,宽长尺寸比的最优解问题,得到了TEm0波传播时,其宽长比应趋近于0;TMmn波传播时,m＜n,仅TM12的宽长比为1;m≥n,宽长比为n/m.所得结果对矩形波导尺寸的选择和设计有潜在的应用价值.     

Shielded rectangular dielectric wave guides for millimeter wave integrated circuits

The dispersion characteristics of Insulated non-radiative dielectric guides are computed using mode matching technique. From the dispersion characteristics the dielectric loss conductor loss and wave impedances are derived. Effect of metallic walls on trapped insulated image guide are also discussed. The dimensions of Insulated non radiative dielectric guide are same as that of rectangular metallic wave guide at ka band.     

Magnetostatic wave convolvers

The present paper reviews recent theoretical results, and reports initial experimental results, on the convolution of contra-propagating magnetostatic forward volume waves (MSFVWs), in the form of cw signals or time-limited cw pulses, in an epitaxial yttrium iron garnet (YIG) film. Computations of the convolver bilinearity factorF _int indicate an efficient convolution process over a wide bandwidth, with values ofF _int that are of the same order as, or better than, the reported experimental results for MSW convolution in a YIG cylindrical or plate geometry. The values of F_int determined experimentally are in excellent agreement with theory. These results are of interest to microwave system developers particularly if bandwidths of 1 GHz or larger can be realized in practice. A limiting feature of magnetostatic wave (MSW) convolvers is that the maximum delay time of a delay line that is realizable without excessive insertion loss is in the order of 0.5s. The advantage of MSW convolvers, of course, lies in their ability to perform signal processing directly at microwave frequencies, and in applications such as electronic warfare the advantageously large bandwidths would mitigate the limitations in delay time.This work was supported in part by a contract from the AIL Division of the Eaton Corporation.     

Electrodynamics of wave processes into two-connected planar wave guide structures

There are represented three configurations of two-connected planar wave-guides, two of them have small dissipations. We research theoretically and experimentally dependences of wave impedance, integration level and dissipations of proposed waveguides on their geometrical parameters and dielectric fulfillment structure. Obtained results for planar waveguide are represented and compared with results, correspondent to standard microstrip line researches.     

Millimeter wave antennas

Major advances in millimeter-wave antennas have been made in recent years, in particular in two areas. A new class of leaky-wave antennas based on open millimeter waveguides has been proposed and investigated, and substantial progress has been achieved in integrated antennas where active and passive circuits, possibly in monolithic form, are combined with the radiating elements in one compact unit. Interesting developments have taken place also in a third group of millimeter-wave antennas, that of microstrip antennas and printed circuit antennas in general. An attempt is made to summarize these developments