MC-CDMA在TDRSS系统SMA业务中的应用研究

针对传统跟踪与数据中继卫星系统(TDRSS)中S波段多址(SMA)业务直接序列扩频码分多址(DS-CDMA)的缺点,提出采用多载波码分多址(MC-CDMA)进行替代的调制解调方案,对其系统结构和在TDRSS中应用需解决的关键技术问题进行了分析。MC-CDMA具有数据传输速率和频带利用率高,发送和接收设备简单等优点,在载人航天通信中具有十分重要的应用价值。     

中继卫星天线指向控制策略研究

首先根据中继卫星系统中中继卫星跟踪用户星的要求,定义了中继卫星天线坐标系,推导出了中继卫星天线对用户星的跟踪规律,通过该跟踪规律可以推出中继卫星跟踪用户星时天线方位和俯仰轴转角,为了保证中继卫星与用户星之间的通信,中继卫星单址天线需要精确的指向用户星;然后详细描述了天线指向控制概念,并且设计了星上自主控制方案,星上自主控制方案由捕获和自动跟踪模式组成,一方面设计了天线捕获过程,另一方面对自动跟踪模式的天线步进逻辑进行了合理选择;最后根据推导的跟踪规律,以不同轨道的用户星作为跟踪目标,对所设计的天线指向控制系统进行了数学仿真,并且通过对仿真结果的分析验证了中继卫星单址天线指向性能。     

我国中继卫星系统在交会对接任务中的应用

我国中继卫星系统在交会对接任务中得到了成功应用,显著提升了测控通信覆盖率,充分体现了中继卫星系统在交会对接任务测控通信中发挥的重要作用.结合中继卫星系统特点,分析交会对接任务对中继卫星系统的任务需求;探讨了中继卫星捕获跟踪用户目标、对用户目标测定轨、着陆场直升机缝隙通信等关键技术;最后总结了中继卫星系统抗雨衰影响、多目标支持能力、应急支持能力等方面的经验做法,并提出了后续改进和完善的建议.     

数据中继传输的实时性研究

以提高中继卫星系统数据传输实时性为目标,通过构建数据分发原型系统,分析了用户数据处理的基本流程,从3个方面分析了服务器内部数传时延产生的机理,针对时延产生的各种原因提出了相应的优化措施,并通过原形系统测试,验证了这些优化措施对提升数传实时性的效果。本文结论对指导中继卫星数据分发系统的性能测试,提高数据分发的实时性具有一定的借鉴意义。     

Optimum Design of Single Channel per Carrier Satellite Systems

Optimization of available satellite power and transponder bandwidth is utilized to minimize the Earth station G/T in satellite channel per carrier (SCPC) systems. The corresponding optimum transponder output backoff is obtained. Applications in system design are given. In a previous paper [1] the channel capacity of a satellite transponder handling single channel per carrier (SCPC) transmission was derived. The link carrier-to-noise (C/N) ratio was maximized over the output backoff and the maximum bandwidth available was determined. Given the bandwidth per channel for each carrier, the channel capacity was obtained. The objective of the present investigation is to derive the minimum G/T of the Earth station in SCPC systems by optimum utilization of available satellite power and transponder bandwidth. Applications in system design are discussed.     

Safe Flight 21: ground broadcast service system

The FAA-initiated Safe Flight 21 program is a cooperative government/industry effort to evaluate enhanced aerodome and aircraft capabilities based on evolving communications, navigation and surveillance (CNS) technologies. Safe Flight 21 will demonstrate the in-cockpit display of traffic, weather, terrain, and obstacle information for pilots and will provide improved information to controllers. The Ground Broadcast Service (GBS) System will act as the main communication service between the Safe Flight 21 sensors and both the avionic and ground vehicle users. The data, collected and processed by multiple sensors, is routed to the GBS System for formatting, broadcast timing coordination, filtering, and transmission to the end-users. This paper provides an overview of the GBS System as part of the FAA Safe Flight 21 program. It also presents the GBS System's complete functional requirements as well as user interface formats and protocols necessary for compliance with the Safe Flight 21 Program architecture.     

Flawed Metrics: Satellite Cost per Transponder and Cost per Day

In engineering design, metrics play a critical role in guiding design choices. It is therefore of prime importance that the metrics used to guide decision-making be the "right" metrics. This paper makes the case that two metrics used to guide communications satellites design, namely cost per operational day, and cost per transponder, are flawed under certain conditions in the sense that they result in design choices-increasingly longer lived satellites and larger payloads-that do not necessarily maximize the system's value. This paper advocates a value-centric mindset in system design, and proposes shifting the emphasis from cost to value analyses to guide design choices that maximize a system's value. Counter-examples are provided that challenge the traditional wisdom that longer lived or bigger satellites, being more cost effective on a per-day or per-transponder basis, are also more profitable or valuable. It is shown that while these metrics are useful guides for design choices in a supply-constrained market (in which a cost-centric mindset can prevail), they are flawed metrics on which to base decisions if the market is competitive, and in which the revenues from the system are not guaranteed to remain stable over time, through the impact of technology obsolescence, or overcapacity resulting in downward pressure on transponder lease prices. Finally, the case is made that the current market conditions require a value-centric mindset (as opposed to a cost-centric mindset) that views a spacecraft as a value-delivery artifact, and integrates considerations about the system's cost, its technical environment, and the market it is serving.     

TDRSS Telecommunications Payload: An Overview

The telecommunications payload is described for the tracking and data relay satellite system (TDRSS). The salient design features of the electronic equipment, as well as the performance requirements that such equipment must satisfy to fulfill NASA and Western Union communication functions are presented. Operational characteristics associated with the single and multiple access channels used to relay information to and from users are also highlighted.     

民用飞机试飞规划与管理软件和飞行试验协同平台的接口研究与实现

针对试飞资源复杂多样的特点,阐述了在民用飞机试飞规划与管理软件和飞行试验协同平台间建立接口交联的必要。飞行试验协同平台接口应用计算机技术,借助民用飞机试飞规划与管理软件前端试验信息处理和管理功能,依托试飞任务单和试飞试验点,实现民用飞机试飞规划与管理软件对飞行试验协同平台试飞数据的读取和调用。经应用分析,通过开发接口能便捷地获取完整、准确的试飞数据,降低试飞成本,减少试飞工作量,提高试飞效率,有助于型号试飞工作的更顺利进行。     

应答机测距转发性能分析

分析了采用视频AGC（自动增益控制）、射频AGC和限幅器等3种测距转发模式的应答机性能,分析结果表明：视频AGC模式下,应答机测距通道的输出功率恒定,测距转发性能不随上行信号强度变化而变化;射频AGC模式下,应答机测距通道的输出功率不恒定,测距转发性能随着上行信号强度变化而变化;而限幅器模式可看作射频AGC的一种特殊情况。仿真分析了我国研制的限幅器和射频AGC两种模式应答机的性能,结果表明理论计算的性能与实测结果一致,理论分析正确且理论分析结果可作为链路计算的依据。     

COTS星载双模测控应答机基带设计与实现

提出了一种星载双模测控应答机基带设计方案,采用COTS（商用现货）器件实现,能较好解决星载功率受限和空间辐射效应引起的相关问题。测控应答机主处理器由反熔丝FPGA（现场可编程门阵列）实现,可在低功耗条件下保证最基本测控需求,解调上行DPSK（差分相移键控）信号,调制下行扩频信号;协处理器受主处理器控制,由SRAM（静态存储器）FPGA来实现,对上行扩频信号进行解扩解调。测控应答机可根据星载电源功率情况和不同测控任务切换模式,具有成本低、可靠性高、使用灵活等优势。     

中继卫星复合控制系统设计

根据中继卫星系统多体控制的特点，合理地选择了中继卫星复合控制系统方案；然后根据所选择的方案，分别设计了中继卫星星体姿态稳定控制系统和单址天线指向控制系统，详细描述了天线指向控制概念，并且设计了星上自主控制方案；最后以不同的用户星作为跟踪目标，对所设计的复合控制系统进行了数学仿真。通过对仿真结果的分析，验证了该系统的有效性。     

Deutsche Airbus flight test of Rosemount smart probe fordistributed air data systems

Deutsche Aerospace Airbus (division of DASA) and Rosemount Aerospace Inc. Jointly sponsored a flight test program to evaluate in-flight performance of distributed multifunction air data smart probes. The probes measure pitot pressure, static pressure, and angle of attack. The tests were conducted at the DLR Flight Test Center, near Braunschweig, Germany. Two smart probes were installed on the DLR VFW 614 ATTAS Flight Test Aircraft and tested between June of 1992 and January of 1993. Flight test results are presented together with suggested air data system architectures, including ARINC 738, that can be used with the distributed smart probe concept. New architectures are developed for future commercial aircraft. The smart probe concept offers several advantages including reduced weight and size, reduced number of line replaceable units (LRUs), and increased reliability. Overall cost of ownership is significantly lowered     

MC-CDMA应用于TDRSS多址业务的关键技术研究

传统TDRSS的多址业务采用单载波CDMA扩频方式，数据传输速率和频带利用率低，设备复杂。本文提出采用MC—CDMA方式代替现有的单载波CDMA方式，结合TDRSS的应用环境对MC—CDMA上下行链路的结构进行分析，并对扩频序列设计、信道估计和系统同步三方面的关键技术问题提出解决方法。采用MC—CDMA可以大大提高现有TDRSS多址业务的数据传输速率，频带利用率提高一倍，设备简单，在未来的航天通信中具有重要的现实意义。     

ATS-6 Interferometer

The Applications Technology Satellite-6 (ATS-6) RF interferometer is utilized primarily as a precision 3-axis attitude sensor having an unambiguous field of view of 350°. This function requires two separated ground transmitters, each using one of the two available frequency channels or sharing a single channel by time multiplexing. For 3-axis control, one uplink transmitter can provide 2-axis attitude (pitch and roll) with other sensors (e.g., a Polaris tracker) providing yaw attitude. By utilizing two uplink transmitters and the Earth sensor or three time multiplexed uplink transmitters, the interferometer can also provide measurements of ATS-6 spacecraft orbit position. Uplink frequencies are 6.150 and 6.155 GHz. The receiving antennas are spaced at 19.95 wavelengths (?) for the vernier baseline and 1.66 ? for the coarse baseline. Spacecraft system weight is 8.39 kg (18.5 lb) and power requirement is 15.5 W. Flight evaluation results are given for the interferometer including R F link budgets, modulation of uplink carrier, signal-to-noise ratio, and dropout behavior. A hardware calibration model is described, containing major biases in the phase measurements. Techniques for flight calibration as both an attitude and spacecraft position sensor are outlined . Flight testing has shown that on-line calibration of receiver/converter biases must be performed on a short term routine basis. Interferometer resolution was found to be 0.00140 space angle with negligible noise (jitter) at transmitted power levels above 72 dBW. As an attitude sensor, the interferometer has demonstrated the ability to provide stabilization to better than 0.     

交会对接任务天基双目标测控通信设计

针对交会对接任务对测控通信提出的高覆盖率和双目标测控等需求的问题,分析2颗中继卫星能够提供的覆盖率,设计双目标测控工作模式以及天地协同机制,计算中继链路的性能,分析表明,天基测控可提供约72%的测控覆盖率,能够支持双目标测控,链路余量满足要求;统计了任务中关键段落的测控通信工作情况,分析结果和实际任务情况验证了天基测控在交会对接任务测控通信中的重要作用;最后提出后续任务改进和完善的建议。     

Satellite Communication System Using TDM and SSMA

An outline and the multiple access techniques used in a domestic satellite communications system accommodating numerous small Earth stations are presented. Two kinds of Earth stations are employed in this system, a small Earth terminal (SET) and a master Earth station (MES). Forty-eight two-way satellite channels were achieved in the 6/4 GHz bands with a transponder eirp of about 62 dBm. Time division multiplex is employed in the MES to SET link and spread spectrum multiple access in the SET to MES link.     

调频调相应答机距离零值测量新方法

叙述了分频调制度变换器的工作原理和时延测量。提出了根据测量FM信号源大频偏调制与小频偏调制的时延差来挑选出恒时延FM信号源,采用恒时延FM调制器构成FM—PM应答机（或FM—PM测距地面站）距离零值测量方法和设备,这是FM—PM体制侧音测距系统的一种距离零值测量新方法;提出了采用分频调制度变换器和非恒时延FM信号源构成FM—PM应答机（或FM-PM测距地面站）距离零值测量方法及设备。     

A Domestic Satellite Design

This paper deals with the design parameters of a communications satellite which would be capable of providing domestic telephony, data, and television distribution services. Certain important aspects of the design are discussed, including satellite antenna beam coverage, transponder bandwidth, and transponder radiated power for a given weight range. A baseline satellite design is then presented which has 24 transponders (with 4000 watts radiated power on-axis and 34-MHz radio-frequency bandwidth) fully accessible from the 48 contiguous United States. The design uses crossed linear polarization to reuse the satellite transmit and receive frequency spectrum.     

飞行控制计算机模拟接口BIT电路设计及仿真

随着航空电子设备维修性要求的提高以及设备本身要求具备检测隔离故障的能力以缩短维修时间,机内测试(BIT)在测试领域研究中将越来越重要。功能电路BIT系统是航空电子设备整机BIT系统的重要组成部分,因此从解决实际问题出发,针对飞行控制计算机中的模拟输入和输出接口电路,提出了几种BIT的设计方法,并使用Multisim软件对所设计的BIT监测电路进行仿真,仿真结果表明,所设计的BIT电路是可靠及有效的。