Low-cost precise measurement of oscillator frequency instability based on GNSS carrier observation

Global navigation satellite systems (GNSS) receivers can be used in time and frequency metrology by exploiting stable GNSS time scales. This paper proposes a low-cost method for precise measurement of oscillator frequency instability using a single-frequency software GNSS receiver. The only required hardware is a common radio frequency (RF) data collection device driven by the oscillator under test (OUT). The receiver solves the oscillator frequency error in high time resolution using the carrier Doppler observation and the broadcast ephemeris from one of the available satellites employing the onboard reference atomic frequency standard that is more stable than the OUT. Considering the non-stable and non-Gaussian properties of the frequency error measurement, an unbiased finite impulse response (FIR) filter is employed to obtain robust estimation and filter out measurement noise. The effects of different filter orders and convolution lengths are further discussed. The frequency error of an oven controlled oscillator (OCXO) is measured using live Beidou-2/Compass signals. The results are compared with the synchronous measurement using a specialized phase comparator with the standard coordinated universal time (UTC) signal from the master clock H226 in the national time service center (NTSC) of China as its reference. The Allan deviation (ADEV) estimates using the two methods have a 99.9% correlation coefficient and a 0.6% mean relative difference over 1–1000 s intervals. The experiment demonstrates the effectiveness and high precision of the software receiver method.     

SLUCUBE: Innovative high performance nanosatellite science and technology demonstration mission

The Space Systems Research Laboratory (SSRL) at Saint Louis University is developing SLUCUBE nanosatellite as part of the space mission design program. The objective of the mission is to demonstrate space capability of high performance nanosatellite components that has been developed at SSRL for the past three years. The objective of the program is to provide extremely low-cost and rapid access to space for scientists and commercial exploitation using commercial-off-the-shelf components. SLUCUBE is a double CubeSat with dimensions 10×10×20 cm and a mass of 2 kg. This nanosatellite features suite of technology demonstration components to enlarge the capability of space mission for such class of spacecrafts. The primary mission of SLUCUBE is to test and demonstrate several enabling technologies by flying a number of university developed high performance components. This paper describes the new developed technologies by providing details of specific components developed along with the R&D efforts and laboratory facilities. A brief discussion about the student involvement and educational benefits will also be presented.     

隔离信号调理模块自动校准系统设计

针对隔离信号调理模块型号多、参量多、使用量大,采用手动计量校准耗时耗力、容易出错、工作效率低等问题,在VEE Pro软件开发平台上,设计开发出一套隔离信号调理模块自动校准系统。该系统包括仪器信息记录、校准及打印输出三个主模块,测试过程采用实时测试显示,自动进行数据处理并存档。使用结果表明：该系统操作简便,提高了工作效率及准确度,降低了人为出错几率,确保了测试数据准确可靠。     

基于脉冲调制的卫星射频测试系统变频链路群延时参数校准

群延时参数是变频链路的关键指标之一,本文主要研究卫星射频测试系统变频链路群延时参数校准方法。卫星射频测试系统是卫星地面测试设备的重要组成部分,其变频链路的群延时特性对卫星测距功能测试及信号的传输质量具有重要意义;从群延时定义出发,讨论了群延时的测试原理和方法,提出并实现基于软件无线电技术的调制法测量群延时,该方法特别适用于内本振无法接入的变频系统群时延的精确测量;详细说明调制法的基本原理并研建校准装置。实验表明调制法测量群延时具有较高的精度。     

正交调制解调算法在软件无线电中的应用

软件无线电中信号的调制与解调是研究的重点问题之一。在通用的硬件平台上,采用不同的软件算法来实现不同调制与解调是软件无线电的核心思想。本文提供了一种正交调制解调结构,并给出了用FPGA实现的简化算法,该方法能够很好地满足软件无线电中的要求,最高可达8Mbps的信息传输速率。     

软件可靠性之定量评估方法研究

基于对多种软件可靠性模型的分析,并结合工程软件之特点,提出一种工程软件适用的可靠性定量评估方法,并将其应用于某航天工程软件的可靠性评估。实践表明,本方法简单、可行,对其它领域的软件可靠性评估同样具有参考价值。     

在轨测试软件数据处理模型探讨

本文分析了在轨测试软件中数据处理算法的不一致性问题,提出了统一的逻辑链路模型方法,以消除各种测试链路之问的差异,达到统一化数据处理算法的目的。     

基于工具的软件开发组协作环境解决方案

根据软件工程的理论,以及在实际软件项目开发过程中所遇到的问题,首先强调了工具软件使用对贯彻软件工程思想的重要性,同时介绍了以微创BMS和TCM为核心的开发组协作环境建设方案的构想,可以为软件项目组建立自己的开发协作平台提供借鉴和参考。     

航天扩频测控系统抗传统测控信号干扰研究

随着扩频技术的应用,航天测控网形成了传统测控体制与扩频测控体制相结合的局面,会出现潜在的相互干扰问题。针对这种情况,运用仿真软件建立模型,根据传统测控信号经过相关器后频谱的变化,分析扩频测控系统的处理增益,并详细说明了在扩频测控信号接收带宽内距中心载波不同位置的传统测控信号对扩频测控系统处理增益的影响,以及不同扩频码速率下系统处理增益的变化情况。最后运用本文的分析成果进行举例计算。     

一种基于组合覆盖的黑盒测试用例自动生成方法

给出了一种黑盒测试用例的自动生成方法,该方法基于组合覆盖测试,能够在保证测试质量的同时有效地减少测试用例的数目和测试成本,提高测试效率。本文给出了这种用例生成方法的算法,说明了其有效性,并介绍了该方法软件原型的实现。