基于GPS的新型二级频标锁定系统

提出了一种基于GPS的新型二级频标锁定系统的设计方案。利用信号的时延稳定性和群相位差变化的规律性,产生一种基于长度游标的高精度时间间隔测量方法。将该方法应用于二级频标锁定系统中,通过对被测时间间隔进行多尺度卡尔曼滤波,在MCU控制下算出GPS与二级频标分频信号之间的相对频差;根据二级频标的频-压控制特性得到补偿电压,将该电压进行D/A转换后送到二级频标的压控端,调整输出频率,形成二级频标锁定系统。实验结果表明其锁定精度可达10 -12 /s 量级,与传统频标锁定系统相比具有电路简单,成本低廉,附加噪声小,锁定精度高等特点。
     

AD9852在小型铷频标频率综合电路中的应用

文章概述了一种利用DDS芯片AD9852实现铷频标频率综合电路的方案,给出了具体结果。这种电路方案具有较高的调节能力,可用于小型铷原子频率标准。     

GLONASS-based precise point positioning and performance analysis

Current precise point positioning (PPP) techniques are mainly based on GPS which has been extensively investigated. With the increase of available GLONASS satellites during its revitalization, GLONASS observations were increasingly integrated into GPS-based PPP. Now that GLONASS has reached its full constellation, there will be a wide interest in PPP systems based on only GLONASS since it provides a PPP implementation independent of GPS. An investigation of GLONASS-based PPP will also help the development of GPS and GLONASS combined PPP techniques for improved precision and reliability. This paper presents an observation model for GLONASS-based PPP in which the GLONASS hardware delay biases are addressed. In view of frequently changed frequency channel number (FCN) for GLONASS satellites, an algorithm has been developed to compute the FCN for GLONASS satellites using code and phase observations, which avoids the need to provide the GLONASS frequency channel information during data processing. The observation residuals from GLONASS-based PPP are analyzed and compared to those from GPS-based PPP. The performance of GLONASS-based PPP is assessed using data from 15 globally distributed stations.     

多通道GPS共视法时频传递接收机的研制

GPS共视法是国际上流行的远距离时间频率传递技术,核心是共视法接收机。我们成功研制了多通道GPS共视法时频传递接收机系统,硬件部分主要由自主研制的高精度时间间隔计数器和Motorola生产的VPONCORE GPS引擎组成,软件符合时间频率咨询委员会(CCTF)发布的GPS共视法数据处理软件标准化指南的要求,与单通道GPS定时接收机相比,界面更友好,操作更方便,具有很强的分析处理数据功能。经测试证明多通道GPS接收机零基线共钟共视时间比对的不确定度小于4 ns(仰角40°),与国外报道基本相同。     

Force measurement using strain-gauge balance in shock tunnel based on deep learning

When a force test is conducted in a shock tunnel, vibration of the Force Measurement System (FMS) is excited under the strong flow impact, and it cannot be attenuated rapidly within the extremely short test duration of milliseconds order. The output signal of the force balance is coupled with the aerodynamic force and the inertial vibration. This interference can result in inaccurate force measurements, which can negatively impact the accuracy of the test results. To eliminate inertial vibration interference from the output signal, proposed here is a dynamic calibration modeling method for an FMS based on deep learning. The signal is processed using an intelligent Recurrent Neural Network (RNN) model in the time domain and an intelligent Convolutional Neural Network (CNN) model in the frequency domain. Results processed with the intelligent models show that the inertial vibration characteristics of the FMS can be identified efficiently and its main frequency is about 380 Hz. After processed by the intelligent models, the inertial vibration is mostly eliminated from the output signal. Also, the data processing results are subjected to error analysis. The relative error of each component is about 1%, which verifies that the modeling method based on deep learning has considerable engineering application value in data processing for pulse-type strain-gauge balances. Overall, the proposed dynamic calibration modeling method has the potential to improve the accuracy and reliability of force measurements in shock tunnel tests, which could have significant implications for the field of aerospace engineering.     

Oblique shock train motion based on schlieren image processing

In this paper, shock train motion in a Mach number 2.7 duct is studied experimentally, and large numbers of schlieren images are obtained by a high-speed camera. An image processing method based on Maximum Correlation Detection (MCD) is proposed to detect shock train motion from the schlieren images, based on which the key structures, e.g., separation positions and separation shock angles on the top and bottom walls, can be analysed in detail. The oscillations of the shock train are generated by rhombus and ellipse shafts at various excitation frequencies. According to the analysis of MCD results, the distributions of the frequency components of shock train oscillation generated by the two shafts are distinctly different, in which the motion generated by the ellipse shaft is much smoother; shock train motion is mainly characterized by the oscillation of separation position while the separation shock strength is not so sensitive to downstream disturbance; there is a hysteresis loop relation between the downstream pressure and separation position.     

Frequency reconfigurable antenna actuated by inflated triangular structure: Design and analysis

This paper proposes a frequency reconfigurable triangular antenna actuated by an inflated triangular structure. The open path antenna is transformed from an open type to a closed structure by inflating. Inflatable structures are easy to manufacture by fusing 2 inextensible membranes together along a defined pattern of lines. However, the prediction of their deployed shape remains a challenge. To solve the pattern changed problem, guided by geometric analyses and local buckle characteristics, the inflated triangular structure has been designed and verified by experiment and simulation. In the process of transformation of the antenna, the resonant frequency of the antenna is changed because this frequency is determined by the conformational change. The resonant frequency changes from GHz to kHz when the design of initial structure sizes is from millimeter to meter. The measured peak gains, the frequency, and the radiation direction are also reconfigurable by the initial size. Finally, the reconfigurable resonator array is presented, which is coupled to electric fields to absorb all incident radiation. In this work, the changed pattern design by inflating is applied to the antenna design, and its frequency reconfigurability is achieved. Through the electricity performance analysis of the reconfigurable antenna, precise manufacturing will be possible and provide guidance for manufacturing frequency reconfigurable antennas.     

芯片级光钟技术综述

芯片级光钟是一种基于热原子中光频跃迁的新型光钟,近年来随着光子集成技术、激光技术和微机电技术的发展,该类光钟可以实现较小的体积和较高的精度,有望广泛应用于对体积、质量、功耗和精度敏感的各种国防装备中.介绍了国内外芯片级光钟技术的进展情况,阐述了芯片级光钟的相关技术,包括基于双光子跃迁的光频标技术、微制造气室技术和微腔光频梳技术等,分析了影响频率稳定度和准确度的主要因素,最后对芯片级光钟面临的机遇和挑战进行了简要的展望.     

Unintentional modulation evaluation in time domain and frequency domain

With the development of wireless communication technology, the electromagnetic environment has become more and more complex. Conventional signal identification methods are difficult to accurately identify illegal devices. However, electromagnetic signals have an unavoidable device-specific characteristic unintentionally generated by a transmitter, appearing in the form of an Un Intentional Modulation(UIM), namely Radio Frequency Fingerprint(RFF). RFFs can be used to uniquely identify an emitter ...     

一种超宽带电子战测频技术的研究

随着雷达技术的发展,宽带瞬时信号截获是信息化装备的必备功能单元.从理论和试验验证的角度详细分析了超宽带电子战接收机的工作原理、测频技术和应用场景,提出了一种简化的MonoDFT算法,实现了2GHz～18GHz频段内雷达信号辐射源的高精度频率测量,并设计了两种应用场景和实现方法.理论分析与实验表明,接收机能够实现瞬时带宽...