数字信道化技术中ADC的性能分析

在卫星通信系统中,数字信道化技术的应用越来越广泛,而模数转换器（ADC）作为数字信道化器前端不可缺少的一部分起着至关重要的作用。基于ADC基本原理和性能,仿真分析了在ADC量化位数不同的条件下,ADC对数字已调信号解调性能的影响。     

数字信道化的级联设计

在宽带信号侦察中数字信道化是一个极其重要的环节。当侦察的信号带宽非常宽,需要的数字信道化个数很大时,用一级信道化实现非常困难。其中,大点数、高速率的DFT设计和硬件实现是一个最突出的难点。针对这个问题,提出了一种数字信道化的级联实现结构,把实信号的数字信道化与复信号的数字信道化级联起来,能够大大降低设计难度,并且这种基于模块化的设计便于工程实现。仿真结果证明,这种方法能够有效实现实信号的无盲区、抗混叠的频谱恢复。     

卫星通信中数字信道化方法及其对比

提出了几种应用于卫星通信中的数字信道化方法,即频域滤波(或FFT滤波)方法、多相/离散傅立叶变换(DFT)和信号分析方法(AS)。并分别对它们的原理、性能和特点进行了讨论和研究。在此基础上,还对三种方法的混合使用进行了较深入的研究。并对三种方法中的一种(AS)方法进行了有效的仿真,使这些方法的有效性得到了证明。     

宽带数字信道化设计

数字信道化接收机具有高截获概率和处理灵活的特点,设备体积小巧,是未来通信对抗接收机的发展趋势之一。通过对低通滤波器组数字信道化实现方法进行研究,实现了实信号非严格抽样数字信道化算法的严密推导,解决了虚假信号判决及信道合并等问题,并使用Matlab仿真工具箱Simulink对算法进行了仿真,对工程的系统设计具有一定的指导意义。     

一种基于复指数调制精确重构滤波的宽带星载数字信道化器

信道化技术是下一代宽带卫星通信系统中星载交换的关键技术之一。运用该技术,提取宽带卫星上行信号中的各窄带信号,然后经过变频、基带信号处理、交换等处理,最后综合成宽带下行信号,进入卫星下行链路。该文针对宽带卫星通信系统,提出一种基于复指数调制精确重构滤波器组的新型宽带星载数字信道化器。该信道化器既适合均匀带宽交换、又适合非均匀带宽交换的星载信道化器。数值实验表明,该新型信道化器具有较强的灵活性和可扩展性,克服了已有信道化技术只适合均匀带宽星载交换的局限,同时对信噪比和数据存储量有较大的改进和提高。     

一种基于时间-频率特征分析的自适应信道化技术

针对按频率均匀划分子信道的数字信道化技术缺乏灵活性、资源利用率低等问题,提出了一种基于信号时间-频率特征分析的自适应信道化技术.对中频数据进行时-频分析,根据信号时-频特征参数差异对子信道进行跟踪、聚类,自适应动态调整参与反变换的子信道,实现宽带复杂调制信号的完整截获、跟踪、分离.仿真分析结果验证了算法的有效性,且其计...     

宽带数字接收机的设计与实现

系统阐述了宽带数字接收机的设计原理及实现方法,并在其基础上重点介绍了数字信道化技术。对多项关键技术进行了论述,并给出了相应的公式推导和原理框图,在电子战（EW）领域的数字接收机工程设计中,具有很高的应用价值。     

基于多相滤波的通用数字信道化技术

传统的信道化技术一旦信道带宽确定后,滤波计算时分解的相数和信道化后的时域分辨率也相应确定,耦合性较强,导致信道化技术在实际工程使用时灵活性存在一定的不足。文中首先给出了基于多相滤波的实信号数字信道化数学模型;然后,在此基础上推导了通用数字信道化数学表达式;最后,通过仿真验证了通用数字信道化技术的正确性。文中提出的通用数字信道化技术有效实现了信道带宽与多相滤波相数、信道化后时域分辨率的解耦,增加了系统设计和信道化技术应用的便捷性。     

基于非均匀滤波器组的动态信道化滤波

针对中频带宽内存在多个子带信号,其个数、位置和带宽具有时变性的情况,该文提出一种基于非均匀滤波器组的动态信道化滤波的方法:由事先给定的子带信号间的最小保护间隔确定均匀滤波器组的子信道数目并设计相应的余弦调制滤波器组;由子带信号的位置分布求得非均匀处理矩阵,并由此直接合并余弦调制滤波器组的对应的相邻子信道以构成非均匀滤波器组;当信号动态变化时,只要根据新状态下的子带信号位置分布更新非均匀处理矩阵,就能完成新信号的信道化接收;利用不同子带信号的抽取因子之间的大小关系提前部分抽取因子以降低实现过程的运算量。仿真实例验证了新方法的有效性。     

面向6G的卫星通信网络架构展望

分析和研究了未来6G卫星网络架构并提出了设想。首先介绍国内外星地融合的研究现状,结合6G网络的愿景、需求和6G网络架构的当前研究成果,总结了6G网络架构的技术特征;然后通过对人工智能（AI）在通信领域的研究和应用分析,以及AI在6G网络中关键作用的深入挖掘,提出了AI赋能的6G卫星通信网络总体架构、接入网架构及核心网架构的设想,同时提出了分阶段演进和分步骤实现的建设思路,最后对基于区块链的6G卫星通信网络韧性鲁棒机制进行了技术探讨。     

Capacity gain of an uplink-synchronous WCDMA system under channelization code constraints

The performance of an uplink-synchronous wide-band code-division multiple-access (WCDMA) system is evaluated for radio environments with low temporal dispersion. The capacity gain of synchronous WCDMA is evaluated theoretically under certain constraints and by means of extensive dynamic system level simulations for more advanced scenarios. The effect of channelization code shortage, the impact of the dispersive radio channel on the orthogonality of received signals, and soft handover are some of the considered effects. The potential capacity gain is found to equal 35.8% in a multicell scenario, conditioned on an infinite number of channelization codes per cell. For a more realistic scenario with channelization code constraints, the capacity gain is reduced to 9.6%. The absolute number of users per cell, relative to the available number of channelization codes within each scrambling code group, is therefore found to be an important metric. This further suggests that the capacity gain of synchronous WCDMA decreases when other capacity-enhancing techniques are deployed, such as uplink antenna diversity, soft handover, voice activity detection, etc. The presented simulation results in the case where soft handover is not considered accurately match the analytical findings.     

差分GPS滑坡监测中卫星坐标解算的程序设计

卫星坐标的实时计算是差分GPS滑坡监测的重要基础。文中以面向对象的程序设计思想,具体介绍了GPS卫星坐标的计算过程和程序实现方法,将GPS卫星坐标解算程序实现过程分解为数据导入模块、卫星坐标解算模块和结果保存模块。通过具体实例进行计算,测试了程序的可行性。同时该程序也为差分GPS滑坡监测系统的开发提供了参考。     

宽带数字信道化EDA设计

数字信道化接收机具有高截获概率和处理灵活的特点,设备体积小巧,是未来通信对抗接收机的发展趋势之一。基于低通滤波器组的数字信道化实现方法,构建了优化的数字信道化实现方法。使用Matlab仿真工具箱Simulink及Xilinx集成设计工具System Generator实现了对信道化接收机从系统到底层硬件设计的全流程仿真设计,对工程的系统设计具有一定的指导意义。     

数字卫星接收机中Unicable功能的设计与实现

针对Unicable器件的广泛采用,提出一种在数字卫星接收机中实现Unicable功能的方法。首先介绍了Unicable技术的原理、控制信号时序、数据格式与指令定义,然后对接收机中Unicable软件控制模块的整体框架、初始化和调谐流程、通信冲突检测与异常处理、实现与测试等进行了阐述,实验表明该软件控制模块在不同数字卫星接收机平台中得到了良好的应用。     

Transmission of Two NTSC Color Television Signals Over a Single Satellite Transponder Via Time-Frequency Multiplexing

We describe a time-frequency multiplexing (TFM) method for transmitting two television signals over one satellite transponder, which gives significant improvement over existing methods. The complexity of the hardware implementation is similar to existing time-division multiplexing (TDM) systems, but the picture quality, when received on a 10 m earth station, approaches that which is currently being requested by the major television networks. Unlike existing frequency-division multiplexing (FDM) systems, TFM needs no backoff of the satellite transponder. The general philosophy of TFM is described, including the benefits of using a difference signal to reduce the overall required bandwidth. Also discussed is companding of the difference signal as a means of improving the overall signal-to-noise ratio. Several alternative methods of implementation are considered, along with those which have been explored in some detail. We then describe an experimental TFM system which was implemented using digital field memories and tested with a 10 m earth station operating through the COMSTAR D2 satellite. Received picture quality was excellent in all cases. Weighted SNR was 53-56 dB, and in practically all instances subjects could not tell any difference between single-picture FM transmission and TFM dual-picture transmission.     

一种高效的宽带数字信道化接收方法

宽带雷达对抗侦察数字接收机具有较宽的瞬时频率覆盖特性和较高的截获概率,并能处理同时到达的多个信号。多相滤波信道化接收机是实现宽带接收的一种方法,其抽取运算在滤波运算之前,运算量小,输出速率低,便于后续处理,是一种高效结构。给出了多相滤波信道化数字接收机的基本原理和实现方法,采用重叠一半多相滤波信道化数字接收机能够有效消除接收盲区,实现全概率接收并消除虚假输出,通过仿真试验证明了其有效性。     

Modeling of Buffer Storage in Video Transmission

In video applications, the storage requirement is considerably large and hence they require large amount of network resources for their transmission. For transmitting the videos through a physical channel, there are two types of channelization-constant bandwidth and variable bandwidth channelization. It has been reported that using variable bandwidth channelization the buffer storage requirement is less than that of constant bandwidth channelization. Therefore, using variable bandwidth channelization a stochastic model is proposed for estimating the buffer storage so that the continuous delivery of the video data can be provided to the users.     

Saw filter technology in support of mobile communications at ESA

Severe RF spectrum limitations imposed by international regulations make filtering, and principally channel filtering, a key parameter of the mobile satellite service. About 30 MHz is available at L-band for maritime, aeronautical and land mobile users, and must be shared between all potential service providers! Furthermore, this band must also accommodate signals with characteristics as dissimilar as: data at low and high bit rates, digital and analogue voice. Even worse, the transmissions are to be done with different categories of users, having terminals with G/T in the range of ?4 to ?24 dB/K. If the satellite payload provides a global earth coverage the RF spectrum will have to be channelized so that the various types of signals can be efficiently handled. This is what happens in the return transponder of the INMARSAT second-generation satellite. If, as anticipated for future mobile satellite systems, spot beams are implemented, further channelization becomes necessary to provide the maximum of flexibility in the channel to beam allocation. In either case, a minimum of bandwidth can be wasted in the guardbands, while at the same time hardly any distortion is to be tolerated in the useful passband. The present article will illustrate, with two examples, how these drastic filtering requirements can be best fulfilled with surface acoustic wave technology.     

Capacity gain of beamforming techniques in a WCDMA system under channelization code constraints

This study addresses the performance of a wideband code-division multiple-access mobile communications system with beamforming antenna arrays (AAs) at the base station, synthesizing a grid of beams. In order to fully exploit the capacity gain from beamforming without jeopardizing the stability of the system, a directional power-based admission control (AC) scheme is applied. Due to the higher capacity offered by beamforming techniques, shortage of orthogonal channelization codes in the downlink becomes an increasingly important factor, which may result in blocking of users before the interference power limit is reached. The problem of channelization code shortage is addressed, and a solution based on splitting the cell into several code regions is proposed. For a network with circuit switched data services operated at 64 kb/s, the capacity gain for an eight-element AA is found to equal a factor of 2.5 for a universal mobile telecommunications equivalent system, with one channelization code set per cell. The capacity gain is limited by severe channelization code shortage under these circumstances. This problem is solved by deploying a cell splitting strategy with multiple code regions, which subsequently results in a capacity gain increase to a factor of 3.4. Furthermore, the soft capacity mechanism associated with partial deployment of AAs in a subset of the cells in the network is also addressed. It is demonstrated that a hot spot cell with AAs also helps increase the capacity of the surrounding cells with conventional sector antennas when using a power-based AC strategy.     

面向21世纪的现代卫星移动通信 下

面向２１世纪的现代卫星移动通信（下）陈如明（邮电部外事司北京１００８０４）３．３ＭＥＯ－Ｏｄｙｓｓｅｙ系统Ｏｄｙｓｓｅｙ（奥德赛）系统是由美国ＴＲＷＩｎｃ。公司开发的ＭＥＯ系统，于１９９１年５月２８日向美国ＦＣＣ提出了使用许可证申请。它由１２颗星组成...