Application of Ground/Air Data Link to General Aviation Operations

The Federal Aviation Administration (FAA) is currently upgrading secondary surveillance radars with systems which will have an integral data link capability, the Mode Select (Mode S) beacon system. These new systems will allow two-way data communications between ground systems (e.g., weather databases and Air Traffic Control (ATC) systems) and aircraft that are equipped with data link compatible Mode S transponders and suitable display and input devices. Initial data link services include both weather information and ATC advisories. The MITRE Corporation* is developing an in-house capability to perform end-to-end operational evaluation of data link services. Initially, a low-cost, portable pilot position man-machine interface is being developed for use in general aviation operations. The objective is to explore operational issues in laboratory and limited flight test environments, and to demonstrate these services on a data link I/O device, a laptop portable personal computer (PC) with touch panel. A group of pilots will bench test the interface design, and the results will be incorporated into the design used in flight testing. This paper describes the project's objectives and results to date, including implementation details and pilot test results.     

Maximum likelihood azimuth estimation applied to SSR/IFF systems

A conventional (nonmonopulse) secondary surveillance radar (SSR) is significantly cheaper than a monopulse SSR but exhibits much greater azimuthal error, especially when some of the replies are missing. Estimation techniques and their performance are discussed with special reference to SSR applications, and a novel estimator for conventional SSR is described. The proposed technique is a close approximation of the maximum-likelihood estimator (MLE), taking into account the receiver characteristics as well as the missed replies. Estimator performance obtained by analysis and computer simulation is compared with that of conventional estimators that are based on the leading and trailing edges of binary sequences and shows significantly improved accuracy     

Computation of aircraft geometric height under radar surveillance

A radar system for geometric height estimation of civil aircraft is described. The system consists of one standard or mode S secondary surveillance radar (SSR) and one omnidirectional antenna sited away from SSR under an airplane. The geometric height is derived by trilateration. Systematic errors are compensated for by deriving the profile of the effect on height measurements of the bias in range measurements. A curve-fitting technique is then used, which estimates both the geometric height and any non-zero systematic errors     

Federal Radionavigation Plan-pie in the sky for civil aviation?

The Federal Radionavigation Plan states that all present navigation and landing guidance facilities will be retired starting in 2005, and full dependence for these functions will be placed on augmented GPS. Once this is implemented, civil aviation will be totally vulnerable to terrorist jamming of the GPS signals over wide earth areas with widespread disruption of air traffic and potential disasters. It has become apparent that the use of GPS/GNSS is complex and expensive for the required civil aviation functions. It is clear that a different system form is needed for civil aviation, a redundant satellite/ground based system that will prevent it from being a jamming target while providing ATC surveillance, area navigation, collision warning/avoidance, high-speed data link and Category I landing guidance globally, plus precision Category III guidance in the terminal areas as needed. Such a system will be described     

嵌入式电子飞行仪表系统软件设计

设计了一种基于嵌入式操作系统的电子飞行仪表系统软件。介绍了电子飞行仪表系统的基本构成,在嵌入式操作系统上设计并实现了主飞行模式、导航模式、发动机信息模式等功能。分析了电子飞行仪表系统软件设计的原则和结构,介绍了软件的类和消息机制。此外,通过在嵌入式系统的有限资源和三维处理的复杂算法间进行合理的折衷,实现了空间变换、立体投影和曲线消隐等算法模块,构成了自行设计的三维地形引擎。软件已经在基于Intel,Motorola等多种嵌入式处理器的系统上下载成功并且能够稳定运行。     

Performance Analysis of Monopulse Receivers for Secondary Surveillance Radar

In modern secondary surveillance radar (SSR) the monopulse technique is currently introduced for the measurement of the azimuth of the targets. The monopulse technique is based on a suitable processing of signals received by a multiple antenna. In SSR the signals are generated by a transponder on the aircraft as replies to interrogations from ground equipment, and consist of trains of pulses. The monopulse measurements can be carried out on the basis of a single pulse from each train, so that it provides a great number of azimuth estimates. Many monopulse measurement devices exist, corresponding to different processing techniques. From the point of view of accuracy and precision, their behaviors differ with respect to the sources of errors, both internal (noise and imperfect calibrations) and external (interference and propagation effects). The four main types of monopulse receivers are analyzed here with respect to the effects of the internal error sources on the resulting measurement accuracy. After an introductory discussion of the performances of the receivers, a detailed analysis is carried out on the basis of a general mathematical model. The results are given in an analytical form and in some comprehensive diagrams.     

用于SAR运动补偿的DGPS/SINS组合系统研究

使用考虑位置误差相关项的伪距率观测模型 ,研究了用于合成孔径雷达运动补偿的差分 GPS/ SINS伪距率组合系统。结果表明 ,组合系统的长期位置精度能达到 1 m左右。 GPS数据更新率低于 INS,在 GPS测量时间间隔内 ,组合系统的性能仅由 INS决定。虽然 INS误差随时间积累 ,在 GPS数据更新率为 1 s的情况下 ,即使采用中等精度的惯性仪表 ,其相对位置精度为厘米级 (这里相对位置精度指组合系统在 GPS测量时间间隔内位置误差的变化范围)。     

Separation of SSR Signals by Array Processing in Multilateration Systems

Location and identification of cooperating aircraft in the airport area (and beyond) may be implemented by multilateration (MLAT) systems using the secondary surveillance radar (SSR) mode S signals. Most of these signals, spontaneously emitted from on-board mode S transponders at a fixed carrier frequency, arrive randomly at the receiving station, as well as many mode A/C replies from legacy transponders still in use. Several SSR signals are, then, overlapped in multiple aircraft situations. Therefore, the aim of this work is the separation of overlapped SSR signals, i.e., signals superimposed in time at receiving stations. We improve the MLAT receiving station by replacing the single antenna by an array of m elements and using array signal processing techniques. In the literature, several algorithms address the general source separation problem, but a very few of them are specifically designed for a mixture of overlapping SSR replies. Unfortunately, all of them have either some shortcomings, or an expensive computational cost, or no simple practical implementation. In this paper, we use the time sparsity property of the sources to propose more reliable, simpler, and more effective algorithms based on projection techniques to separate multiple SSR signals. Real recorded signals in a live environment are used to demonstrate the effectiveness of our method.     

Analysis and design optimization of monopulse receivers forsecondary surveillance radar

The sensitivity to calibration and component errors of the receiver configurations used for monopulse processing of secondary surveillance radar (SSR) replies is analyzed. The effects of video gain error in amplitude processors and large Gaussian perturbations in phase processors are discussed. Phase processors are shown to be robust to variations in antenna difference pattern null depth. A half-angle phase processor that yields the benefits of phase processing without the sensitivity to system errors associated with conventional implementations is described     

基于三层C/S模式的远程数字法视频监控系统设计

结合当前视频技术、计算机网络技术、通信技术的发展,研究分析了数字视频监控系统两层C/S模式的优缺点,给出了基于三层C/S模式的数字视频监控系统设计,以及三层C/S模式数字视频监控系统中管理服务器的应用实例.     

TV space surveillance system

This article represents the research results of the television space surveillance system, or, in other words, the optical surveillance system. The purpose of the work is the design of a specialized optical surveillance system, stabilization and surveillance equipment, and a television unit. The system's simplified structural and functional scheme is described, as well as its justification and operation principle. The application prospects are estimated.     

STADAR: Servo Tester with Automatic Data Acquisition and Reduction

STADAR is a Servo Tester with Automatic Data Acquisition and Reduction developed for the Apollo program. This paper describes the operational capability of STADAR and discusses certain aspects of the design. STADAR evaluates system performance by supplying an input stimuli and two data acquisition and analysis channels. Stimuli (0.02-30 c/s 0-10 V peak) are automatically programmed to a frequency accuracy of ±0.01 percent and an amplitude accuracy of ± 0.1 percent. Data acquisition accuracy is 0.1 percent or 50 microvolts. System design utilizes programmable data filters to improve system S/N ratio. Active filter mechanization methods and results are presented as well as techniques for instantaneous precise generation of stimuli which are automatically programmed.     

甚高频数据链模式二通信协议栈一致性测试系统设计及验证

甚高频数据链模式二(VDLM2)通信协议是航空电信网(ATN)所支持的四种甚高频数据链模式之一,已被定为过渡时期ATN空地通信的主要方式,是目前应用最为广泛的甚高频数据链。本文以自主开发的甚高频模式二协议栈通信系统为被测系统,设计了一种与之适合的一致性测试系统,通过该测试系统对模式二协议栈进行了一致性测试。测试结果表明,测试系统可以很好地完成一致性测试的功能,并具有很强的扩展性,为系统性能进一步测试奠定了基础。     

星基ADS-B接收机监视容量分析

星基广播式自动相关监视（ADS-B）系统是实现广域范围内航空器监视的重要技术手段。星基ADS-B系统内部存在严重的共信道干扰,共信道干扰限制了系统的监视性能。为了定量给出星基ADS-B接收机监视容量的计算方法,首先,给出了星基ADS-B系统的模型;随后,通过理论分析得到了星基ADS-B接收机报文冲突概率及报文正确接收概率,以此为基础理论,分析得出星基ADS-B接收机位置报文更新间隔及监视容量的计算方法;最后,构建了星基ADS-B仿真系统,仿真验证了理论计算公式的正确性。研究表明：星基ADS-B接收机的监视容量由飞机-卫星空天链路的误码率及ADS-B应用子系统所要求的位置报文更新间隔联合决定。     

Software Techniques for Detecting False SSR Tracks

The problem of detecting false secondary surveillance radar (SSR) tracks due to electromagnetic reflections is discussed. An approach via software is considered and some algorithms for the SSR tracks detection are proposed. Some experimental results are reported.     

DGPS-based aircraft flight guidance/test system

The utilization of the GPS system for Aircraft Flight Guidance/Test (AFGT) is a research project in China. The paper describes the concepts and the technical realization of such a system, including three components: ground subsystem, on-board subsystem and data communication link using TDMA technique. The purpose of the proposed AFGT system is to calibrate and verify performance of an on-board radar. Therefore, it must meet the requirements of evaluation of radar performances in several areas: accuracy, coverage range, and others. The AFGT System's displays are separately: a Moving Colored Digital Map on which flight trajectories, waypoints, and heights of aircrafts are clearly marked; and a Polar Coordinate Figure on which the bearings, headings, and distances of aircrafts relative to the origin of the ground control center are shown. The AFGT may monitor and guide several aircrafts flying in the pointed airspace. It support airport surface surveillance and air traffic control at the terminal area. A real-time software package RTTEST, which includes tracking display software and on-flight test software for radar evaluation, has conducted simulation with satisfactory position accuracy     

Preoperational testing of data link-based air traffic managementsystems in Magadan, far East Russia

The Global Positioning System (GPS) has been used in many ways which were unimagined by its original planners and implementers. This paper discusses one such application; the surveillance of commercial aircraft in a developing airspace environment. GPS provides system users with the ability to determine their own position with an accuracy, reliability and cost that is unprecedented. Voice procedures augmented by radar have been the primary tools for air traffic surveillance since the end of World War II. But for some countries the equipage of aircraft with GPS and a data link capable of carrying position reports to the ATC authorities is providing a viable alternative to long-range secondary radar systems. In the summer and fail of 1995, ARINC installed and demonstrated equipment in Magadan, Russia which permits air traffic controllers of MagadanAeroControl to monitor GPS position reports generated by aircraft as far away as Canada and the South Pacific. The position reports were displayed against maps and flight tracks. This equipment has clearly demonstrated an alternative technology for the upgrading of the ATC system in Siberia and other remote areas     

加载速率对层间断裂韧性的影响

虽然加载速率对层间断裂的影响已经被广泛的研究,但是现有的研究结果还未能给出加载速率对层间断裂韧性影响的明确趋势。研究人员发展了许多测量层合板复合材料以及胶接层断裂韧性的实验方法。本文的主要目的是对层间断裂韧性测量的实验方法进行综述,尤其是准静态和动态加载条件下层间起裂韧性的测量。首先介绍了准静态下Ⅰ型、Ⅱ型以及Ⅰ/Ⅱ复合型层间断裂韧性的测量方法,然后综述动态加载下层间断裂韧性的实验方法。前两部分着重介绍断裂实验中断裂参数(载荷、位移、起裂时间以及裂纹长度)的测量以及断裂韧性的计算。之后又综述了两种光学测量方法在层间断裂实验中的应用。最后将文献中加载速率对层间断裂韧性影响的实验研究结果进行了总结。