卫星通信系统在上、下行综合干扰条件下的性能分析

研究了卫星转发器分别工作于线性状态和限幅状态时,同时存在的上行干扰和下行干扰对整个通信链路的载波与噪声干扰比的影响,并以某一卫星通信系统为例进行了具体分析,验证了采用上行干扰和下行干扰进行综合对抗时,将会取得更好的干扰效果,为干扰卫星通信采用新方法提供了一定的理论依据.     

Starlink星座对GSO卫星系统馈电链路的下行同频干扰分析

随着大型低轨星座网络的快速发展,其与静止轨道卫星通信系统间的用频矛盾越发突出.针对低轨通信星座系统与静止轨道卫星系统的馈电链路下行同频干扰,本文以Starlink第一期星座为研究对象,分析了其对静止轨道卫星系统馈电链路的下行干扰场景,建立了以干噪比和等效功率通量密度为评价指标的同频干扰分析模型.仿真结果表明,低纬度地区...     

透明转发器卫星通信系统在干扰条件下的性能

本文研究了存在上行干扰时透明转发器卫星通信系统的性能。首先对透明转发器卫星通信系统在上行干扰条件下性能进行了分析并给出了计算误比特率性能的数学表达式,然后对其中两种典型情况进行了仿真和分析。研究结果表明:通常认为无抗干扰能力的窄带多址技术结合放大器输入回退,在干扰条件下同样具有一定的健壮性;而且,导致多个用户同时达到不可接受误比特率的干扰信号功率必须与所有用户信号的总功率相当,并且该功率通常比导致转发器进入饱和状态的功率要小一些。     

卫星通信链路及其计算

按照国际电信联盟（ITU）定义的电信基本术语，无线线路（或称无线链路）是指由无线电发信机和无线电收信机提供的信道。卫星通信链路是无线链路中的一种，其基本组成是由一地球站发射机到卫星转发器的上行链路，和卫星转发器到另一地球站接收机的下行链路。由于从地球站发射的微波功率，经自由空间传播到卫星接收天线的过程，和从卫星转发器变频、放大后，经自由空间传播到接收地球站的过程，信号功率会有许多衰减，再加上卫星和地球站的接收系统又存在内部和外部噪声以及其它干扰，因此，决定一条卫星链路传输质量的主要指标是C／N、或…     

通信卫星转发器的主要性能参数

通信卫星转发器的主要参数为G／T、SFD与EIRP。相关参数在用户载波的链路计算和卫星通信的系统设计中起着关键作用．卫星通信工程师应对其有深入的了解。本文拟从转发器参数在链路估算中的使用、参数说明及计算方法，参数的测量与验证．参数在使用中的变化和取值比较等方面．试作简要介绍，以期广大的卫星通信用户能够选好和用好转发器资源。     

WCDMA软切换中的下行功率控制方案

发射功率控制是CDMA系统的关键技术之一。在WCDMA的软切换中，传统下行链路功率控制方案的实现主要存在两个问题：基站发射功率的失衡和下行链路干扰的增大。为解决上述问题，本介绍三种新的下行功率控制方案：降低TPC频率功率控制、调整环功率控制和站选择分集发射功率控制。其中前两种方案用于恢复软切换中基站发射功率的平衡，而最后一种方案用于减小下行链路干扰。研究表明，利用上述方案能够有效减小软切换中基站发射功率的差异或下行链路干扰，从而提高了系统容量。     

一种双向链路频谱重叠共享频带的卫星通信系统

提出一种基于C,Ku,Ka频段透明转发器的双向链路频谱重叠共享频带的TDM/FDMA星型网卫星通信系统方案,小站至中心站的反向链路采用FDMA接入方式,中心站至各个小站的前向链路采用TDM广播方式。理论和仿真分析结果表明:该系统的频带效率比常规TDM/FDMA系统提高了1倍,而链路的传输性能仍可以达到实用要求。     

卫星数字电视接收站的工程设计、调测和系统性能评估（4）

2.1.3 上、下行链路中的干扰噪声 卫星数字电视接收站的噪声除上、下行链路线性器件内部产生的热噪声外,还有一部分是上、下行链路的干扰噪声。由于落在噪声带宽内的各种干扰功率的总和N_(Itol)可以假想成一个噪声温度为T_(Itol)噪声源产生,N_(Itol)=kT_(Itol)Bn,k为波尔兹曼常数。这样这些干扰噪     

数字卫星转播车链路分析

1.前言针对目前新闻时效性要求越来越高,新闻报道要求更快、更广、更活、更深、更近的方向发展,我台购置了一台新闻卫星车并于2009年5月投入使用,该车采用德国奔驰公司的Sprinter515CDI厢式车改装;卫星天线采用英国GIGASAT公司1.5m车载式天线。新闻卫星通信质量不单单取决于占用的卫星功率和地球站的品质因素,它还受上行链路参数、卫星转发器工作点和一些外界参数的影响,为此需要进行整个通信链路计算。用户提出业务信息容量和质量的需求,并选定通信卫星后,设计者进行链路计算。先由信息带宽算出占用转发器带宽的百分比(也是占用卫星功率的百分比),于是定出占用的卫星发射功率。     

FDD—CDMA的下行链路的波束形成

本文研究了在智能天线在ＦＤＤ－ＣＤＭＡ中的下行链路的应用，利用上行链路接收数据，估计了下行链路的信道相关矩阵和对其它小区用户的相对干扰总量，给出下行链路的波束形成方法，即在保证一定的有效发送功率的同时，使得对其他小区的用户干扰最小。计算机仿真表明：（在多小区蜂窝ＣＤＭＡ环境中，采用上述方法比仅保证用户方向的最大发送功率，有更小的中断率。     

Partial Processing Satellite Relays for Frequency-Hop Antijam Communications

Military satellite communications systems may be implemented with varying levels of satellite on-board processing. For frequency-hop (FH) spread-spectrum signals two options are the dehop-rehop transponder (DRT) and the symbol regenerative processor (SRP). This paper considers FH,M-ary FSK modulation in the presence of full band and worst case partial-band noise jamming. The relationships among end-to-end signal-to-noise ratio (SNR) performance or probability of bit errors and the uplink and downlink SNR are derived. For a DRT, an additional parameter is the satellite filter bandwidth Wssince this may differ from the despread modulation bandwidth Wrfor a particular user access under TDMA variable-data-rate operation. The SNR performance in this case depends upon the ratioW_{s}/W_{r}a well as the uplink and downlink SNR. The resulting penalty in the link budget of the weaker of the uplink or downlink is much less than the mismatched ratioW_{s}/W_{r}and diminishes as the links become unbalanced. The SRP slightly outperforms the DRT but it is more complex and does not as easily accommodate variable data rates.     

Up-link power control of satellite earth-stations as a fade countermeasure of 20/30 GHz communications systems

All 20/30 GHz satellite communications systems suffer from atmospheric attenuation in cloudy or rainy weather, particularly if high link availabilities are required. In FDMA systems the power transfer characteristic of each carrier is linear, so any up-link fade degrades the overall performance on a dB-by-dB basis. This, together with the fact that the 30 GHz up-link attenuation is much greater than the 20 GHz down-link attenuation, makes adaptive countermeasures of up-link fades most important. This paper shows how the overall link performance can be improved by applying up-link power control. It is explained how this improvement depends on the up-link/down-link balance, the dynamic range of the up-link power control, and the up-link and down-link atmospheric attenuation. If a small number of carriers can be allocated in an intermodulation-free frequency plan, the satellite transponder can be operated near saturation in order to optimize the down-link performance. Computer simulations of up-link power control for such an FDMA scheme have been performed based on measured three-carrier characteristics of a transponder TWT. It is shown that the overall link performance in faded conditions can be significantly improved with up-link power control. This may be utilized to increase the availability of a satellite link or to relax the earth-station performance in terms of G/T or EIRP if the link margin provided by an earth-station with fixed EIRP is satisfactory.     

合成孔径雷达复合干扰机研究

分析了SAR的回波信号处理原理。在现有有源欺骗干扰信号实现方式的基础上,提出了一种复合式干扰机。该干扰机可以根据不同的干扰效果,选择工作方式,实现应答、转发及散射波干扰。     

Analysis of reactive jamming against satellite communications

In this paper, we analyze the feasibility of reactive jamming in a satellite communications scenario and propose a countermeasure that takes advantage of the constraints associated with reactive jamming. A reactive jammer is a type of jammer that has the ability to sense a portion of spectrum and immediately transmit a jamming signal when it senses a signal it wants to jam. Thus, a reactive jammer can counter the processing gain associated with frequency hopping spread spectrum. This paper provides a three‐step approach to analyzing the primary constraints associated with reactive jamming, as well as detailed example scenarios (both theoretical and simulated) that demonstrate the feasibility analysis. Additional clarity is provided by splitting the analysis into uplink and downlink jamming. A strategy to mitigate the effects of reactive jamming is presented, which takes advantage of the geometric constraints of reactive jamming by using a coding and interleaving scheme that results in the transmitted bits appearing at the very beginning of each hop. This work demonstrates that reactive jamming is a valid threat to satellite communication systems. The analysis and simulation results suggest that as long as the geographical area around user terminals is free of reactive jammers, substantial mitigation can be achieved using the proposed mitigation strategy. Copyright © 2015 John Wiley & Sons, Ltd.     

自适应调零天线对快速跟踪干扰抑制的研究

为了有效地抑制来自跳频卫星通信系统上行链路的快速跟踪干扰,本文提出了一种数字波束形成与跳频相结合的新型干扰抑制技术(AJDBFFH).基于AJDBFFH技术,本文较好地解决了快速跟踪干扰与跳频有用信号相关所带来的干扰抑制问题.通过对快速跟踪干扰抑制的计算机仿真,其结果表明,AJDBFFH技术可以有效地抑制快速跟踪干扰,系统的误码率性能得到了明显的改善.     

Frequency-hopped spread spectrum in the presence of a followerpartial-band jammer

A countermeasure to a partial-band follower jammer is proposed for frequency-hopped spread-spectrum communications. This technique randomizes the transmission technique used by the transmitter (and receiver). Either the information is carried by M tones which are transmitted in a frequency slot, or by M frequency slots which contain signal energy. As a counter-countermeasures, the jammer randomizes between jamming the same frequency slot being used by the communicator, or jamming a subset of the slots not being used by the communicator. The performance for randomized strategies for the communicator and jammer is investigated. It is shown that the proposed technique enhances the system's performance     

时空混沌二相调制雷达与干扰一体化信号

减小电子战平台上雷达和干扰机体积、重量、功耗的有效途径是实现雷达和干扰机一体化，即使雷达和干扰机共享硬件平台，发射信号采用同时具有探测定位能力和干扰特性的一体化信号。提出了一种基于单向耦合映象格子构造时空混沌二相序列的方法，分析了时空混沌二相序列的伪随机性能，构造了时空混沌二相序列调制的．体化时空混沌二相编码信号，并分析了该信号的同有分辨能力和干扰性能。分析结果表明，时空混沌二相编码信号可以作为雷达与干扰机一体化信号，并且具有优良的固有分辨能力和遮盖下扰特性。     

相控阵干扰机干扰防空雷达网资源分配

当前空袭作战中,防空方可能采用地空导弹武器系统组网打击来袭目标,多波束相控阵干扰机成为干扰防空武器系统组网雷达的首选。着重研究了多波束相控阵干扰机干扰防空雷达网中资源分配的问题;建立了以防空雷达网各接收机前端干信比之和最大为目标函数的数学模型,并根据所建立的数学模型,选择启发式算法,通过计算机编程对数学模型进行了仿真研究,得出了仿真结论。