风云三号(D)气象卫星微波湿温度计系统建模和仿真

针对风云三号卫星微波湿温度计,该文建立了全功率式微波辐射计系统的仿真模型,重点对热辐射噪声源、混频器、低噪放、滤波器与检波器等关键性器件进行了参数化建模。从信号处理的角度对全功率式微波辐射计的工作过程进行了模拟,并对仿真系统的输出功率、灵敏度和线性度进行评估与分析。通过与实际仪器的测试结果对比,验证了所提仿真模型的正确性。

     

基于谱图预处理的卫星通信信号盲检测

传统功率谱检测是建立在噪声谱的均值和方差满足不随频率变化假设基础上的,而实际非协作卫星通信中的噪声谱一般并不满足此假设,导致该方法的检测性能受限。该文用滑动窗最小二乘法对接收信号进行预处理,使噪声谱趋近满足上述假设,由此提出了一种卫星通信信号的盲检测方法,并推导了相对于传统功率谱检测方法的性能改善因子。仿真结果表明：该方法在相同条件下检测性能一般明显优于传统的功率谱检测方法,且具有计算量小、易于实现等优点。     

部分响应连续相位调制信号在卫星移动信道中的误比特率性能分析

该文给出了组合卫星移动信道中采用差分相位检测(DPD)和最大比组合(MRC)的部分响应连续相位调制(PRCPM)信号的误比特率计算公式,并给出了有关数值计算结果。     

基于周期截断数据矩阵奇异值分解的干扰抑制技术

针对现有适用于单天线接收机的干扰抑制技术难以为周期调频(PFM)干扰和卫星导航信号提供足够分离度,导致消除干扰成分时卫星导航信号损伤较大的问题,该文提出一种基于周期截断数据矩阵奇异值分解的干扰抑制方法。利用调频干扰信号的周期性把分散在较大带宽的能量集中到重排数据中几个甚至单个频点;进而采用奇异值分解(SVD)将干扰与期望信号映射进不同的投影子空间以消除干扰成分。仿真结果表明该方法可以降低在剔除干扰时卫星导航信号损失,提升卫星导航接收机对抗宽带周期调频干扰的能力。     

复杂城市环境下的全球导航卫星系统/捷联惯性导航系统组合导航算法

针对复杂城市环境下,全球导航卫星系统(GNSS)信号出现频繁短暂失锁或拒止时,对GNSS/捷联惯性导航系统(SINS)组合导航系统的导航精度和鲁棒性影响较大问题,该文提出一种改进的因子图滤波方法。首先使用GNSS接收机内部参数构建信号误差鉴别函数,能实时估计出信号受多径干扰、遮挡等情况下的信号测量性能;同时利用载体运动约束条件构造零速修正因子,对GNSS拒止情况下的系统状态进行更新,避免系统导航性能极速下降。实验结果表明,改进的因子图方法相比经典因子图方法,在城市复杂环境下能提高定位精度63.50%和测速精度42.26%,同时也具有更低的存储量和计算复杂度,特别适用于城市车辆辅助驾驶导航设备中,对导航精度、硬件资源和实时性约束强的场景。     

北斗时频传递链整体绝对校准技术研究

全球导航卫星系统(GNSS)时频传递因其较好的不确定度水平及使用方便等特点,已成为当前应用最广泛的时频传递技术。时频传递链校准是时间和频率量值精准传递的关键与必要前提,传统的分步绝对校准技术存在校准步骤复杂、不确定度来源多的问题。针对上述问题,该文提出一种整体绝对校准技术,对北斗卫星导航系统(BDS)时频传递链进行整体一次性校准,测量不确定度更低。通过对时频传递链整体绝对校准方法的研究,搭建了时频传递链整体绝对校准系统及实验平台,实现了北斗时频传递链的整体与分步绝对校准实验,评估其不确定度。结果表明两种方法校准结果一致性优于1.76 ns,合成标准不确定度分别评定为0.80 ns与1.00 ns。     

The data station controller of the apollo system

This paper describes a high speed satellite communication system called APOLLO, designed to allow the transmission of documents across Europe. Emphasis is put on the hardware and software for which Logica is responsible, and the message flow through the system. A review is given of the current position and future plans of the project.     

直播卫星电视光接收机的研制

光纤接入是直播卫星(DBS)覆盖技术近期发展的热点之一,尤其是用于新一代Ka波段卫星下传的宽带卫星直播电视信号光传输的光发射机与接收机的开发研制更是成为当前研究的重要课题.通过对直播卫星下行信号和光接收机原理的分析,针对光纤宽带接入网的应用特点,设计并研制开发出了一款达到3 GHz带宽,用于接收宽带卫星电视光传输信号,具有较高灵敏度和较大动态范围的模拟光接收机.     

Experimental study and empirical evaluation of carrier compression and third order intermodulation products of unequal carriers in a communication satellite transponder

Carrier compression and third order intermodulation products of two and three unequal carriers have been studied experimentally using a 36 MHz wide C-band transponder of INSAT-1B satellite. From the experimental data, empirical relations for carrier compression for two unequal carriers have been derived, which agree with the measured data within ±0.5 dB. The empirical relations for carrier compression derived for two unequal carriers have been extended to three unequal carriers and good correlations with measured data have been obtained. Empirical relations for third order intermodulation products of two and three (f₁+f₂-f₃ type) unequal carriers have also been derived.     

The Global Positioning System: Signals,measurements, and performance

The Global Positioning System (GPS) is a satellite-based navigation and time transfer system developed by the U.S. Department of Defense. It serves marine, airborne, and terrestrial users, both military and civilian. Specifically, GPS includes the Standard Positioning Service (SPS) which provides civilian users with 100 meter accuracy, and it serves military users with the Precise Positioning Service (PPS) which provides 20-m accuracy. Both of these services are available worldwide with no requirement for a local reference station. In contrast, differential operation of GPS provides 2- to 10-m accuracy to users within 1000 km of a fixed GPS reference receiver. Finally, carrier phase comparisons can be used to provide centimeter accuracy to users within 10 km and potentially within 100 km of a reference receiver. This advanced tutorial will describe the GPS signals, the various measurements made by the GPS receivers, and estimate the achievable accuracies. It will not dwell on those aspects of GPS which are well known to those skilled in the radio communications art, such as spread-spectrum or code division multiple access. Rather, it will focus on topics which are more unique to radio navigation or GPS. These include code-carrier divergence, codeless tracking, carrier aiding, and narrow correlator spacing.