对GPS区域映射系统中比例优化的研究

GPS区域映射系统通过对分布式转发器的时延控制,实现定位区域上的映射关系,使由GPS制导的武器错误定位,从而偏离原有的目标,实现对重要目标的保护^[1]。文章首先给出了求解区域映射系统中虚拟点邻域的迭代算法,在此基础上分析了虚拟点与真实点的位置关系以及转发器的分布对映射比例的影响,并在有效干扰区域内,对如何选择虚拟点的位置和转发器的分布以达到映射比例的优化进行了研究,得出的结论为实际应用提供了参考。     

芯子宽厚比对铝蜂窝夹层结构平压强度的影响

用正六边形代替实际蜂芯,推导了夹层结构的平压强度与芯子宽厚比的关系,并对八种规格的芯子平压强度进行统计,统计结果虽然与推导的结果有偏差,但规律却是一致的,即蜂窝夹层结构的平压强度随着芯子宽厚比d/t_s增大呈负指数减小。     

Temporal evolution analysis of storm-enhanced density during an intense magnetic storm on March 2015

An intense Storm Enhancement Density (SED) event with the magnetic storm occurred on 17–24 March 2015 has been investigated. The morphological character of the SED during different phase of the magnetic storm is examined and compared with the non-storm time. Three intensity indexes, i.e., “general” SED index, “heavy” SED index and “severe” SED index, are defined to represent the intensity of SED respectively represented by the numbers of the ionospheric total electron content (TEC) grids with TEC > 60 TECu, TEC > 80 TECu and TEC > 100 TECu. The temporal evolution of the SED intensity indexes during a time span covering the non-storm time and the magnetic storm time have also been investigated. The SED exhibits a shape with two parallel slender troughs in the middle and low latitudes during the non-storm time and then gradually develops into an ellipse structure as the development of magnetic storm. The intensity of SED and the fluctuation of the TEC evolution are generally corresponding to the fluctuation of Dst index. The analyzing results enrich our understanding of the temporal and spatial evolution of the ionospheric SED.     

基于MAP估计和广义高斯MRF的SAR图像边缘比率检测方法

SAR图像极低的信噪比以及乘性噪声给SAR图像的边缘检测带来了较大的困难。提出了一种针对SAR图像边缘的自适应贝叶斯检测方法。该方法利用广义高斯马尔可夫随机场作为局部均值的先验概率分布模型,利用贝叶斯准则推导了局部均值的最大后验概率估计。广义高斯马尔可夫随机场模型参数估计和局部均值估计采用联合迭代技术进行求解。边缘检测器的参数采用接收机操作性能曲线和卡方检验进行选择。基于实测SAR数据的仿真实验结果表明,本文的边缘检测算子是有效的,并优于已有的SAR图像边缘检测算子。     

真实干扰条件下的雷达信干比测量研究

提出了雷达接收功率比的定义及其表达式,建立了典型干扰样式的雷达信干比关系式,从而形成了以雷达接收功率比为中介参数,在不影响雷达工作状态和实际环境条件下测量雷达信干比的方法。经实验室对比性测试,初步验证了研究结果的正确性。     

Estimation of ballistic coefficients of space debris using the ratios between different objects

This paper proposes a new method to estimate the ballistic coefficient (BC) of low earth orbit space debris.The data sources are the historical two-line elements (TLEs).Since the secular variation of semi-major axes is mainly caused by the drag perturbation for space objects with perigee altitude below 600 km,the ballistic coefficients are estimated based on variation of the mean semi-major axes derived from the TLEs.However,the approximate parameters used in the calcu lation have error,especially when the upper atmosphere densities are difficult to obtain and always estimated by empirical model.The proportional errors of the approximate parameters are cancelled out in the form of ratios,greatly mitigating the effects of model error.This method has been also been validated for space objects with perigee altitude higher than 600 km.The relative errors of esti mated BC values from the new method are significantly smaller than those from the direct estimation methods used in numerical experiments.The estimated BC values are used for the prediction of the semi-major axes,and good performance is obtained.This process is also a feasible method for prediction over a long period of time without an orbital propagator model.     

SAR干扰效果研究

研究了对干扰前不同图像质量的合成孔径雷达(SAR)的干扰效果问题。从干扰前SAR图像质量指标积分旁瓣比(ISLR)入手,提出等效信干比的概念,建立积分旁瓣比与等效信干比的关系,分析等效信干比与发现概率、错误概率的关系,最后确定不同图像质量所对应的所需信干比。     

多晶硅沉淀的灰色分析

本文给出了灰色信噪比的定义，并将其用于多晶硅沉淀的数据分析，使表面缺陷和沉淀厚度在最佳条件下试验结果与灰色预估值更符合。     

基于FPGA的数据链路误码仪设计

本文对数据链路通信系统中的误码仪进行分析设计,给出了误码率的定义,剖析了误码仪的工作原理,并分别对发射端和接收端两部分进行了描述,介绍了两种典型误码仪的工作方法,其中详细描述了阈值检测法的原理和工作模式。文中实现了发射端和接收端的FPGA设计,给出FPGA设计结论,并最终表述了在数据链路上的应用情况。     

GNSS carrier phase ambiguity resolution based on integrity restriction in ambiguity domain

Carrier phase ambiguity resolution of Global Navigation Satellite System (GNSS) is a key technology for high-precision navigation and positioning, and it is a challenge for applications which require both high accuracy and high integrity. This paper proposes efficient ambiguity resolution methods based on integrity restriction using Fixed Failure rate Ratio Test (FF-RT) and Doubly Non-central F-distribution Ratio Test (DNF-RT), and derives the related processing models and numerical algorithms compared with the traditional Ratio Test (RT) method. Firstly, the integer ambiguity resolution and validation procedures, especially the Least squares AMBiguity Decorrelation Adjustment (LAMBDA) estimation and RT validation are analyzed. Then the quality evaluation using success rate, the FF-RT method using Integer Aperture (IA) estimation and the NDF-RT method are proposed. Lastly, the simulation and analysis for LAMBDA using RT, FF-RT and DNF-RT methods are performed. Simulation results show that in case of unbiased scenario FF-RT and DNF-RT have similar performances, which are significantly better than RT. In case of biased scenario it is difficult for FF-RT to predict the biased success rate thus it should not be used for bias detection, while DNF-RT can detect biases in most cases except for the biases are approximate or equal to integer, which has the important benefit for early detection of potential threat to the position solution.