水下相位式激光测距定标方法

基于相位式激光测距的工作原理,提出了将相位式激光测距仪用于水下测距的思路,从原理上分析了水下相位式激光测距的可行性。通过水下距离测量实验,对水下相位式激光测距可行性进行了验证,完成了水下相位式激光测距仪的测距定标算法,并探究了水体浊度对相位式激光测距动态范围和测距精度的影响。实验结果表明,经过定标校正后的水下相位式激光测距仪在水下3.5 m范围内测距误差平均值不超过3 mm,测距范围与水体浊度间存在指数衰减关系。该水下相位式激光测距仪为水下距离的探测提供了一种新方法,可实现水下目标近距离的精确测距。     

相位激光测距中相位测量与误差分析

激光方向性强,单色、相干性好,这些特点使得激光测距可以应用在多个领域。由于相位法测距可以达到较高的精度,因此相位法测距成为激光测距的首选。文中根据激光测距的特点,从几方面对相位法测距进行了改进和优化。在保证精度的前提下,减少了对单片资源的消耗,使激光测距系统有更快的响应速度和更多的资源进行功能扩展。通过仿真验证,文中所提方法达到了预期效果,并可根据不同精度需求,灵活地设计程序。     

SBG加装卫星激光测距仪研制报告

SBG型卫星跟踪望远镜加装激光测距仪可对人造卫星测距和测向。本文重点介绍该仪器的装置情况,主要技术性能;介绍总体设计方案,解决的主要技术问题和激光测距的主要试验结果。利用接收概率公式、测距方程和分配的激光发射、激光接收等部件技术指标、参数对激光测距系统的作用距离和测距精度进行理论分析和计算。地面水平激光测距和卫星激光测距结果表明,理论分析和计算结果是正确的,达到和超过了原设计指标。云南天文     

基于FPGA的激光测距回波信号高速采集研究

在激光测距系统中,微弱回波信号的检测处理一直是一个难题.本文主要讨论了激光测距接收系统的实现方法,这种测距方法既适用于短距离的测量又适用于长距离的测量.首先介绍了脉冲式激光测距的原理,在此原理的基础上,结合FPGA的高速信号处理能力,设计了高精度激光测距接收系统,并设计了回波信号接收与计数电路模块.     

脉冲激光测距系统回波形心小波提取算法研究

为适应数字激光测距系统对测距信息处理的要求,在对脉冲激光测距系统回波信号波形特征分析的基础上,完成用于波形测距的小波基选取,进而实现了小波变换提取波形形心的算法.并凭借MATLAB工具平台,根据试验实测数据验证了形心小波提取算法正确和适应性.     

基于SNSPD与SPAD探测器的激光测距系统的比较研究

通过实验比较研究了基于SNSPD与SPAD探测器的激光测距系统.实验中,当接收回波端衰减120 d B时,天空光背景可忽略,基于SPAD的激光测距系统探测概率低于0.2%,而基于SNSPD的激光测距系统探测概率达35%;当激光发射频率低于1 k Hz,基于SNSPD的激光测距系统探测概率比SPAD高60%以上.研究表明:在探测弱信号回波光子时,SNSPD的探测性能远远优于SPAD,其原因是SNSPD具有较低的暗计数和高探测概率.与此同时,在接收端无衰减情况下,天空光背景会带来暗计数,影响测距系统信噪比.通过仿真分析表明,当背景亮度L0高于30 W/(m~2·sr)时,该基于SNSPD的激光测距系统的信噪比低于6,可能影响测距系统稳定探测.     

一种面向空间应用的激光测距方案设计与实验

针对空间应用背景对激光测距系统宽测程、高精度、实时测量的要求,使用相位式激光测距法中分散的直接法设计了一种激光测距方案,其理论测程可以达到10 km,测距精度可以达到0.1m。对激光器和窄带滤光片提出了技术指标要求,对雪崩光电二极管（APD）进行了选型,并通过对空间环境背景噪声的分析和对空间非合作目标测程方程的分析验证了技术指标选择和APD 选型的合理性。实验结果表明:该系统最大测距误差为8.71 cm,符合测距精度优于0.1 m的技术指标要求,同时具有较高的动态性能,测距时间不超过1 ms。此外,系统具有较小的整体功率和质量,分别为13.29W 和693 g,可作为天基应用的有效载荷。     

西德韦特策尔新型卫星激光测距系统的首次试验

1976年9月在美国加利福尼亚州对一台短脉冲激光测距系统进行了验收试验后,于同年12月运抵韦特策尔人卫站安装。但因运输所引起热交换器损伤,直到1977年6月才开始第一次卫星测距试验。该系统的详情见文献〔1〕和〔2〕。本文仅介绍在韦特策尔安装以来的试验,并讨论有关硬件、跟踪软件和卫星测距的试验资料,评述在韦特策尔用卫星激光测距的远景。     

时间比例放大法在脉冲激光测距中的应用

脉冲激光测距机体积小巧、测距时不需要辅助目标,因此便于携带且操作简单。但由于受到计时器计时精度的限制,脉冲激光测距的精度相对较低。而高精度脉冲激光测距系统往往难以达到低成本和便携的要求。为此,介绍一种时间比例放大法用来提高脉冲激光测距精度,这样就可以以低成本开发具有较高测距精度的便携式激光测距系统。     

光电经纬仪中激光测距发射系统设计

论述了在光电经纬仪上应用激光测距装置的重要性,即可实现单台经纬仪确定目标位置.介绍了激光测距的原理及测距方程,针对光电经纬仪中激光测距系统的结构特点,对测距分系统发射系统进行了设计,实现了各种复杂条件下的激光测距.     

基于扩频多址的差转游标测距方法与应用

针对游标测距法在转发测距中无法实现多址测距的问题,提出了一种基于扩频多址的差转游标测距方法。该方法采用游标法实现高精度测距,采用直接序列扩频技术以正交的伪随机码（PN码）区分不同的测距信号,利用不同的差转频率区分不同的转发信标。基于该方法构建了测距系统,系统的测距精度可达亚米级。转发信标使用电池供电和无线通信调度,结构简单,成本低,功耗小,安装简单。该系统非常适用于工业场景的人员定位管理。     

Efficient space segment utilization in satellite data networks

A generalized approach to the efficient utilization of the space segment in multicarrier per transponder applications is presented. Based on the concept of normalized satellite link densities, the conditions required to fully utilize the available transponder resources (power and bandwidth) are derived. These conditions are applied to the design of satellite data networks comprising a large number of stations of various sizes. The design approach is based on the idea of determining the ground segment configuration that ensures that the satellite links to small earth stations (power-limited links) and those to large earth stations (bandwidth-limited links) are balanced in such a way, that both the transponder power and the bandwidth are fully utilized. An example of the design of a simple data network using this technique is shown.     

A Method for Transponder Capacity and Link Performance Optimization in Preassigned Multilevel SCPC Systems

An investigation of ways to improve the capacity in a dedicated SCPC transponder has resulted in the development of a method for optimizing the transponder capacity and link performance in preassigned multilevel SCPC systems. The main approach is to form different groups of carriers based on the traffic requirement, and on typical characteristics of the link destinations such as variations in the satellite e.i.r.p. and downlink path loss, and differences in the receive earth station antenna size. The Fletcher-Powell optimization technique is used to determine the set of optimum carrier levels at the transponder TWTA input. Application of the method to a number of preassigned multilevel frequency plans in a global transponder environment clearly indicates that the total carrier-to-noise ratios for all the links can be optimized at any specified CNR value, and that the optimized capacities are substantially higher than that of the basic two-level system. The implementation of multilevel plans is fairly simple if all downlink carrier levels can be monitored at some reference station in the SCPC network to reasonably control the uplink e.i.r.p. levels.     

卫星数据链路干扰分析

本文对卫星通信的上、下行链路和转发器实施干扰的可行性进行了分析,并详细分析了上行干扰对透明转发器的影响.研究结果表明,对上、下行链路实施干扰的有效途径为升空平台(无人机或卫星)载有干扰设备;对透明转发器卫星通信系统,干扰的有效功率必须大于所有用户的总功率,宽带干扰或梳状谱干扰是较好的干扰方式.     

SBM系统数传与测距实现及其在军事通信中应用

序列平衡调制配以跳频、比相单音测距、和近正交二进制移相键控（BPSK）调制数据块码,可以同时进行抗干扰数据传输和距离测量,数传和测距性能优越,适宜于军事通信网上广泛使用;本文介绍序列平衡调制的数学模型、系统结构、调制、解调、测距的实现原理与方法、及其数据传输和测距性能。适于高速数据链的目标跟踪与命令传输、军事Ad hoc网路、mesh网络、军用认知无线电网络等。     

利用帧头消除测距时标整周期滑动的方法

在弹载扩频脉冲应答式测距系统中,应答机直接利用捕获脉冲作为时标信号进行测距。此法在高信噪比时测距精度较高,但在低信噪比时,伪码同步脉冲的抖动较大,同时捕获脉冲会产生整数个伪码周期地滑动,导致测距误差较大。为了提高测距精度,提出了一种利用帧头消除脉冲应答式测距时标整周期滑动并降低时钟抖动的方法。在获得伪码捕获脉冲并检测到帧头后,应答机才启动应答信号,可有效降低低信噪比时的测距误差。     

An Adaptive Multiple Beam System Concept

An adaptive multiple beam system, which has flexibility to adapt beam power to varying beam traffic, is proposed. The multiple beam transmitter, which is called "hybrid transponder" in this paper, consists of a pair of multiport hybrids and a set of amplifying elements. Power combining, isolation, and intermodulation characteristics of this multiport network are analyzed. Also, a new interbeam exchange and feeder link connection concept, which serves as the basis for an adaptive multiple beam system, is proposed. Finally, characteristics of an experimental 8-amplifier 8-port hybrid transponder are described.     

一种双向链路频谱重叠共享频带的卫星通信系统

提出一种基于C,Ku,Ka频段透明转发器的双向链路频谱重叠共享频带的TDM/FDMA星型网卫星通信系统方案,小站至中心站的反向链路采用FDMA接入方式,中心站至各个小站的前向链路采用TDM广播方式。理论和仿真分析结果表明:该系统的频带效率比常规TDM/FDMA系统提高了1倍,而链路的传输性能仍可以达到实用要求。     

Routeing and filtering in the ETS-V transponder for mobile communication experiments

The Japanese spacecraft ETS-V implemented an experimental mobile satellite communication system via a transponder called AMEX (aeronautical maritime experimental transponder). L-band was used for the mobile link and C-band for the feeder link. For the L-band two-beam system routeing and filtering were performed through 12 SAW filters and four switches in the IF part. The effective frequency allocation plan was obtained considering the features of the links used and the characteristics of SAW filters. The filtering to prevent EMC problems was also studied for AMEX, which handles high- and low-level signals simultaneously. AMEX shows good performance in orbit and is being used for a variety of mobile communication experiments by many organizations including the Communications Research Laboratory.     

Up-link power control of satellite earth-stations as a fade countermeasure of 20/30 GHz communications systems

All 20/30 GHz satellite communications systems suffer from atmospheric attenuation in cloudy or rainy weather, particularly if high link availabilities are required. In FDMA systems the power transfer characteristic of each carrier is linear, so any up-link fade degrades the overall performance on a dB-by-dB basis. This, together with the fact that the 30 GHz up-link attenuation is much greater than the 20 GHz down-link attenuation, makes adaptive countermeasures of up-link fades most important. This paper shows how the overall link performance can be improved by applying up-link power control. It is explained how this improvement depends on the up-link/down-link balance, the dynamic range of the up-link power control, and the up-link and down-link atmospheric attenuation. If a small number of carriers can be allocated in an intermodulation-free frequency plan, the satellite transponder can be operated near saturation in order to optimize the down-link performance. Computer simulations of up-link power control for such an FDMA scheme have been performed based on measured three-carrier characteristics of a transponder TWT. It is shown that the overall link performance in faded conditions can be significantly improved with up-link power control. This may be utilized to increase the availability of a satellite link or to relax the earth-station performance in terms of G/T or EIRP if the link margin provided by an earth-station with fixed EIRP is satisfactory.