GPS接收机的中频信号处理算法研究

该文对GPS接收机的中频信号处理算法进行了研究,内容主要涉及信号捕获、载波恢复和伪码跟踪3部分,详细分析了信号捕获过程中所采用的匹配滤波器法、快速傅里叶算法(FFT)、锁频环(FLL)、锁相环(PLL)以及延迟锁定环(DLL)的算法原理,并对环路滤波器作了相应的阐述,给出环路对应的递推公式．     

A novel high precision Doppler frequency estimation method based on the third-order phase-locked loop

In deep space exploration,many engineering and scientific requirements require the accuracy of the measured Doppler frequency to be as high as possible.In our paper,we analyze the possible frequency measurement points of the third-order phase-locked loop(PLL) and find a new Doppler measurement strategy.Based on this finding,a Doppler frequency measurement algorithm with significantly higher measurement accuracy is obtained.In the actual data processing,compared with the existing engineering software,the accuracy of frequency of 1 second integration is about 5.5 times higher when using the new algorithm.The improved algorithm is simple and easy to implement.This improvement can be easily combined with other improvement methods of PLL,so that the performance of PLL can be further improved.     

一种锁相环调频方法在铷原子频标中的应用

为了进一步实现铷原子频标小型化,分析了几种典型的锁相环调频电路及其特点,设计了一种锁相环二进制移频键控2FSK(binary frequency shift keying)调频方案,给出了调频信号的频谱测试结果。该调频方案已成功地应用在小型化数字式铷原子频标中,能够满足小型化铷原子频标的要求。     

一种铷原子频标射频倍频单元的实现

讨论了射频倍频单元对汽泡型铷原子频标频率稳定度的影响,介绍了一种我们新研制的用于小型汽泡型铷原子频标的数字锁相倍频电路。将该数字锁相倍频电路接入铷原子频标系统后,闭环测得该频标系统的稳定度为σy（r=1s）≤3×10^-11,达到商用小型铷原子频标性能指标,而该倍频电路板的面积仅为原倍频电路板面积的1／2,功耗仅为原倍频电路的1／3。     

卫星导航接收机中码跟踪实现方式的研究

该文对卫星导航接收机中的码跟踪环路进行了研究,主要叙述了锁相环(PLL)、数字环路滤波器、延迟锁定环(DLL)的原理和实现DLL的两种方式,并对这两种实现方式作了仿真。     

基于精密光程差调制的时域干涉信号闭合相位检测方法研究

闭合相位法是实现长基线恒星光干涉高分辨成像的重要技术手段之一,获得精确的闭合相位信息是进行光干涉图像重构的先决条件.提出一种基于精密光程差调制的时域干涉信号闭合相位检测方法,在3路干涉臂上进行非冗余精密光程调制,并通过多次干涉测量结合数据拟合的方法消除光程差调制中存在的正弦误差,使得光程调制的精度达到20 nm以内.引入高速探测器件提升时域干涉信号的采样频率,对探测器上获得的时域干涉信号进行傅立叶变换处理,获得3路干涉臂精确的闭合相位信息.室内实验结果表明,基于精密光程调制的时域信号闭合相位计算精度可以达到1/50波长以内.     

一种可编程逻辑器件在原子钟频率综合电路中的应用

针对被动型铷原子频标电路模块中由三极管等数量众多的分立元件搭建的9倍选频放大模拟电路和种类繁多的集成电路搭建的5.3125 MHz综合器电路,给出了数字化电路解决方案。在此新方案中,通过使用一种复杂可编程逻辑器件对锁相环进行编程控制,可以实现对10 MHz参考信号18倍频的精确控制;同时,利用该复杂可编程逻辑器件内部"虚拟"的集成电路对10MHz参考信号进行分频变换可以得到5.3125MHz信号。实际使用证明,这种设计方案具备易于集成、调试简单的优点,在替换原有模拟倍频、综合器功能电路后,成功实现整机锁定,各项性能指标均达到或优于原有水平,使整机向数字化、小型化迈出重要的一步。     

Acceleration feedback control(AFC) enhanced by disturbance observation and compensation(DOC) for high precision tracking in telescope systems

In this paper, a cascade acceleration feedback control(AFC) enhanced by a disturbance observation and compensation(DOC) method is proposed to improve the tracking precision of telescope systems.Telescope systems usually suffer some uncertain disturbances, such as wind load, nonlinear friction and other unknown disturbances. To ensure tracking precision, an acceleration feedback loop which can increase the stiffness of such a system is introduced. Moreover, to further improve the tracking precision, we introduce the DOC method which can accurately estimate the disturbance and compensate it. Furthermore,the analysis of tracking accuracy used by this method is proposed. Finally, a few comparative experimental results show that the proposed control method has excellent performance for reducing the tracking error of a telescope system.     

锁相环频率合成器中的关键指标和一种优化方法

论述了锁相环频率合成器中的几个重要的性能指标:相位噪声,参考杂散和锁定时间,并给出了几条常用的设计准则。最后采用一种优化结构来改进频率合成器的性能,仿真结果证实了这种优化是可行的。     

All-sky search algorithms for monochromatic signals in resonant bar gravitational wave detector data

In this paper we design and develop several filtering strategies for the analysis of data generated by a resonant bar gravitational wave (GW) antenna, with the goal of assessing the presence (or absence) therein of long-duration monochromatic GW signals, as well as the eventual amplitude and frequency of the signals, within the sensitivity band of the detector. Such signals are most likely generated in the fast rotation of slightly asymmetric spinning stars. We develop practical procedures, together with a study of their statistical properties, which will provide us with useful information on the performance of each technique. The selection of candidate events will then be established according to threshold-crossing probabilities, based on the Neyman–Pearson criterion. In particular, it will be shown that our approach, based on phase estimation, presents a better signal-to-noise ratio than does pure spectral analysis, the most common approach.     

BDS-3新频点信号双频精密单点定位精度分析

北斗卫星导航系统(BeiDou navigation satellite System, BDS)已于2020年7月正式建成并开通, 北斗三号(BDS-3)在旧信号B1I和B3I的基础上, 增加了B1C、B2a新信号. 为了全面评估BDS-3的新信号B1C、B2a的定位性能, 试验了GPS (Global Positioning System)、BDS-3、BDS-2/BDS-3新旧信号的定位性能和BDS系统不同频点与GPS组合定位性能, 对BDS (B1I+B3I、B1C/B2a)+GPS (L1+L2)组合静态PPP (Precise Point Positioning)定位性能进行分析, 并与单卫星系统对比分析. 试验结果表明: BDS-3 (B1C/B2a)在East (E)、\lk North (N)、Up (U)方向的定位精度优于1.25cm、0.89cm、1.67cm, BDS-3新旧频点在E、N方向上定位精度与GPS L1/L2在同一水平上, U方向上新频点定位精度高于GPS L1/L2和BDS-3旧频点, 较旧频点定位精度提升了34.2%, 新频点收敛时间25.9min比旧频点提升了12.7%; 相较于BDS、GPS单系统, 组合系统BDS/GPS定位精度和收敛时间有了明显的提高, BDS-3 (B1C/B2a)+GPS在E、N方向上与BDS-3 (B1I/B3I)+GPS定位精度相当, 在U方向上定位精度前者较后者有了明显的提升, 提升了17.2%, 组合系统新频点收敛时间20.1min比旧频点提升了17.6%.     

基于数字锁相环的GPS可驯钟系统研究

介绍了可驯钟系统的基本原理及实现的一般方法,在分析GPS可驯钟一般实现方法的不足的基础上设计了一种全数字锁相环的实现方案,并使用该方法研制了GPS可驯钟系统.实际测量结果表明,使用该方法后本地1 PPS输出稳定度优于常规方法.     

A new method for resolving phase ambiguity in radio interferometry using Earth rotation synthesis

As a key technique in deep space navigation, radio interferometry can be used to determine the accurate location of a spacecraft in the plane-of-sky by measuring its signal propagation time delay between two remote stations. To improve the measurement accuracy, differential phase delay without phase ambiguity is usually desired. Aiming at the difficulties of resolving phase ambiguity with few stations and narrowband downlink signals, a new method is proposed in this work by taking advantage of the Earth rotation. The high accurate differential phase delay between the spacecraft and a calibrator can be achieved not only in the in-beam observation mode but also in the out-of-beam observation mode. In this paper we firstly built the model of phase ambiguity resolution. Then, main measurement errors of the model are analyzed, which is followed by tests and validations of the model and method using the tracking data of the Cassini mission and Chang'E-3 mission. The results show that the phase ambiguities can be correctly resolved to generate a 10-picosecond level accuracy differential phase delay. Angular measurement accuracy of the Cassini reaches the milli-arc-second level, and the relative position accuracy between the Chang'E-3 rover and lander reaches the meter level.     

Measuring the speed of gravity at short distances: Sensitivity estimate

An experimental set up was proposed to determine the speed of gravitational signals traveling in air or in some other medium. It involves two vibrating masses—the emitters, which will be the sources of periodic tidal gravitational signals—and one sapphire-made mass that will act as a detector, positioned between the two emitters. The detector is planned to be suspended in vacuum and cooled down to 4.2 K, and its vibrational amplitude should be measured by a microwave signal (with ultra-low phase-noise) that is expected to resonate with the whispering gallery modes inside the detector. The mechanical and electrical quality factors of sapphire are quite high, yielding a very narrow detection band that reduces the detector sensitivity while amplifying the phase difference of the emitters' signals. The frequencies of the normal modes of the detector were previously determined using a finite element program. In this work, these frequencies are applied to the calculation of a first estimate of the sensitivity of the experiment.     

An Orbital Prediction Algorithm for LEO Satellites Based on Optical Observations of Short Arcs at Single Station

The forecasting technique of the target tracking based on the short arcs at single station is an important way to guarantee that high-precision photoelectric theodolites can normally track and capture the targets in unconventional environments. We construct the tracking prediction algorithm based on nonlinear filter, which can provide the guiding data for the closed loop tracking under normal circumstances. At the same time we also construct the target prediction algorithm based on the nonlinear transformation, without valid observational data, which can provide a track guidance for the theodolite and ensure that the targets will not be lost. It is demonstrated that the nonlinear filtering is more effective than the EKF (extended Kalman filter) in the tracking prediction algorithm of the short arcs at single station. The results indicate that the nonlinear filter designed in this paper can be used as the guiding algorithm for the optical tracking equipments. And its guiding accuracy is in the same order of magnitude of the theodolite's random measurement accuracy. When the systematic error of the equipments reaches 50″, the accuracy can achieve 20″ for predictions in 60 s. This still satisfies the requirement of the field of view of the tracking equipments.     

The design of diamond Compton telescope

We have developed radiation detectors using the new synthetic diamonds. The diamond detector has an advantage for observations of “low/medium” energy gamma rays as a Compton telescope. The primary advantage of the diamond detector can reduce the photoelectric effect in the low energy range, which is background noise for tracking of the Compton recoil electron. A concept of the Diamond Compton Telescope (DCT) consists of position sensitive layers of diamond-striped detector and calorimeter layer of CdTe detector. The key part of the DCT is diamond-striped detectors with a higher positional resolution and a wider energy range from 10 keV to 10 MeV. However, the diamond-striped detector is under development. We describe the performance of prototype diamond detector and the design of a possible DCT evaluated by Monte Carlo simulations.      

Development of Control Softwares for the SRAO 6-Meter Telescope Based on PCs Running Linux

We have developed a control system for the Seoul Radio Astronomy Observatory (SRAO) 6-meter telescope operating in the 85–115 Ghz frequency range. Four PCs running the Linux operating system control source tracking, take data, execute observations and handle user interface. The control system utilizes a modular and multiprocessing structure to facilitate easy upgrading and troubleshooting. Communication between the processes relies on the interprocess communication (IPC) resources on Linux such as shared memory, message queues, and TCP/IP sockets. Communication between PCs is made via an Ethernet link. We also use digital I/O lines for some status signals which require a short delay. The control system supports scheduling observations, updates observation logs automatically and also supports graphical user interfaces. These all makes the operation easy. By using a commercially available motion control card with an embedded microcomputer for antenna control, we achieved a tracking accuracy to better than 1 arcsec. This revised version was published online in July 2006 with corrections to the Cover Date.     

Scope of high-frequency time keeping in searches for short-period gamma-ray sources

This paper presents a novel technique to derive the absolute time of occurrence of an event with an accuracy of < 200 μs by adapting the HF time synchronization technique to correct for the aging rate and the frequency drift of a temperature-controlled quartz frequency standard. The propagation delay suffered by the HF time signals has been estimated by monitoring the clock error with respect to time signals from five broadcast stations located at distances in the range 500–3700 km from Gulmarg. Using simulated data, we further show the viability of this technique in permitting periodicity searches on timescales of ≥5 milliseconds in cosmic gamma-ray data An erratum to this article is available at .     

A New Feature Vector Using Selected Line Spectra for Pulsar Signal Bispectrum Characteristic Analysis and Recognition

Average pulse profiles of pulsar signals are analyzed using the bispectrum tech-nique. The result shows that there are nonlinear phase couplings between the two frequency axes of the bispectrum charts, which indicate nonlinear factors in the generation and prop-agation of pulsar signals. Bispectra can be used as feature vectors of pulsar signals because of their being translation invariant. A one-dimension selected line spectrum algorithm for ex-tracting pulsar signal characteristic is proposed. Compared with selected bispectra, the pro-posed selected line spectra have the maximum interclass separability measurements from the point of view of the whole one-dimension feature vector. Recognition experiments on several pulsar signals received at several frequency bands are carried out. The result shows that the selected line spectrum algorithm is suitable for extracting pulsar signal characteristics and has a good classification performance.     

一种高精度时间同步器的研制与性能测试

针对移动通信网络基站间需要建立高精度时间同步的需求,研制了一种具有高精度时间同步功能和高精度频率输出的时间同步器,并设计了相应的性能测试方法。测试结果表明,在同等条件下,不同时间同步器输出的1PPS平均同步精度优于5ns／d,24h内输出的频率准确度优于10^-12／s,其他各项指标基本合格,符合设计要求。