共查询到20条相似文献，搜索用时 234 毫秒
1.
2.
着重分析了信号通过无源器件魔Ｔ合成与分配的幅度、相位和频率特性。在此基础上，提出了利用魔Ｔ实现多原频率组合与冗余的几种实用结构．它与以往流行的利用开关在源与源之间直接转换相比，无论在源的有效利用上，还是在保持信号的不中断和相位、频率的连续性方面，都呈现出比较突出的优点． 相似文献
3.
针对目前射电观测设备对数字接收机高采样率、宽带宽、多通道幅相一致,以及高速率直接采样和时域数据存储的需求,通过调研分析多个射电观测设备的数字处理系统的技术架构和功能,提出了基于ZYNQ SOC和ADS54J60等核心器件实现的4通道数字接收机系统方案。单通道最高可实现1 GSPS采样率,具有灵活可拓展的优势,可以通过添加板卡实现采样通道数的增加,能够满足未来大规模可拓展射电干涉阵列的需求。系统由高速数据采集卡、光通信接收卡、服务器3部分设备组成,基于SerDes的高速串行接口技术目前实现16位量化精度、300 MSPS的直接采样功能,具备60 dB满量程信噪比、40 Gbps的SFP+数据传输带宽、1.5 GB/s的PCIe通信带宽,可对4.5～150 MHz范围内中频模拟信号进行采集,目前该系统已经完成软硬件设计和测试。在测试中对频率为10 MHz、幅度为125 mV的正弦波信号进行采样,得到4通道间幅度差小于1 mV,相位延时小于3.3 ns。系统集成可编程SFP+通信接口和多机同步机制,可适应多元阵列同步采集的需要,可同时对原始射电信号的数据进行存储,为射电研究提供更详细的时域数... 相似文献
4.
Fabry-Perot滤光器的误差分析 总被引：1，自引：0，他引：1
本文介绍了影响Fabry-Perot滤光器性能的几个重要因素,并对其产生的误差进行了分析,主要有相位误差,温度变化对系统产生的误差,光线入射角度偏移所带来的误差以及平板平行度误差和平板面形精度对系统的影响等。 相似文献
5.
任旭 《中国科学院上海天文台年刊》1990,(11):151-155
相位校正系统是MK－Ⅲ系统中的重要部分之一。相位校正信号的优劣直接决定了实验结果的质量乃至成败。本文试图对这一信号的注入强度及相应的相位测定误差之间的关系作一些分析。 相似文献
6.
王锦清 《中国科学院上海天文台年刊》2008,(1)
天线的远场辐射方向图(幅度图)在实际天线测量中应用极其普遍,而在一般的资料中很少论及相位特性以及相位和幅度的相互关系,该文对远场的相位以及相位和幅度之间的相互影响作了比较深入的分析,在该文中比较详细地分析了远场相位的理论与实际偏差,及引起这种相位误差的来源和测量方式,这对天线测量及评定天线的性能具有一定的理论和实际参考意义,该文也给出了佘山25m天线的测量结果。由于射电天文望远镜通常为圆形,且工作于信号的远场区域,该文就远场区的表达式在圆形口径面的情况下用标量衍射的手段作了一定的推导。 相似文献
7.
相时延处理软件是嫦娥四号(CE-4)任务甚长基线干涉测量(Very Long Baseline Interferometry,VLBI)测轨分系统软件配置项之一,利用其处理着陆巡视器X波段DOR(Differential One-way Ranging)信号时,观测弧段(scan)内偶尔存在残余群时延跳变问题.论文主要分为两部分:一是根据VLBI信号接收和数据处理流程,从相关相位、频率、幅度和功率方面进行分析,最终将影响因素定位在昆明测站模拟信号异常;二是以scan内时延跳变影响因素分析为基础,通过修正异常基线相关相位,研究残余群时延跳变事后改正方法,并利用定轨软件验证其有效性,升级了相时延处理软件. 相似文献
8.
9.
《天文研究与技术》2020,(4)
针对天线变形耦合影响指向误差评估精度的问题,提出基于几何光学的大型双反射面天线指向误差评估算法。通过建立变形反射面天线的最佳吻合抛物面、偏移副反射面以及馈源在基坐标下的数学模型,计算反射面辐射区间并确定指向误差权重因子,最终建立天线的指向误差评估模型。为验证算法的正确性,应用该模型对一座在建70 m天线的多组虚拟变形工况进行指向误差评估,其结果与现有波束偏移因子算法以及电磁仿真算法的评估结果进行对比,结果表明,该模型评估的指向误差结果与电磁仿真算法以及波束偏移因子算法的评估结果吻合,所提算法正确。该算法为分析天线变形耦合对指向误差评估精度的影响提供了理论依据,在一定程度上提高了天线的指向误差评估精度。 相似文献
10.
介绍了GPS的空间部分、地面控制部分和用户部分的发展状况及其作用。并对GPS定位的基本原理做了阐述。GPS定位误差由几何精度因子和站星距离的测量误差决定,站星距离的测量误差由3大类误差因素决定,它们是与GPS卫星有关的误差、与GPS卫星信号传播有关的误差、与GPS信号接收设备有关的误差。对上述重要误差进行了系统全面的分析,并提出了具体的误差修正模型及各种减小或消除误差的方法。 相似文献
11.
12.
13.
14.
During the declining phase of the longest solar minimum in a century, the arrival of the MESSENGER spacecraft at superior conjunction allowed the measurement of magnetohydrodynamic (MHD) waves in the solar corona with its 8 GHz radio frequency signal. MHD waves crossing the line of sight were measured via Faraday rotation fluctuations (FRFs) in the plane of polarization (PP) of MESSENGER’s signal. FRFs in previous observations of the solar corona (at greater offset distances) consisted of a turbulent spectrum that decreased in power with increasing frequency and distance from the Sun. Occasionally a spectral line, a distinct peak in the power spectral density spectrum around 4 to 8 mHz, was also observed in these early data sets at offset distances of about 5 to 10 solar radii. The MESSENGER FRF data set shows a spectral line at an offset distance between 1.55 to 1.85 solar radii with a frequency of 0.6±0.2 mHz. Other possible spectral lines may be at 1.2, 1.7, and 4.5 mHz; MHD waves with these same frequencies have been observed in X-ray data traveling along closed coronal loops at lower offset distances. An initial analysis of the MESSENGER spectral line(s) shows behavior similar to turbulent spectra: decreasing power with increasing frequency and distance from the Sun. Here we detail the steps taken to process the MESSENGER change in PP data set for the MHD wave investigation. 相似文献
15.
NTSC的双混频时差测量系统试运转结果分析 总被引：1，自引：1，他引：1
中国科学院国家授时中心(NTSC)新进口的由德国Timetech公司制造的双混频时差测量系统(dual mixer time difference system,DMTD)已经通过了试运行。介绍了DMTD的工作原理和设备结构。NTSC时频基准实验室的主钟(MC)信号作为DMTD的频率参考信号,5个氢钟和18个铯钟的频率信号作为被测信号与MC信号进行相位比对。用频率分配放大器输出的多路MC信号也作为被测信号用以监测DMTD本身的精度和稳定度。给出了DMTD和时间间隔计数器TIC实际测量结果的比较及误差分析。测量结果表明DMTD特别适用于频率短期稳定度非常高的氢原子钟这样的频标之间的频率和时间比对。该设备将用于NTSC的守时工作,不久的将来也将用于铯喷泉与氢钟的频率比对。 相似文献
16.
We present a relatively simple time domain method for determining the bandpass response of a system by injecting a nanosecond pulse and capturing the system voltage output. A pulse of sub-nanosecond duration contains all frequency components with nearly constant amplitude up to 1 GHz. Hence, this method can accurately determine the system bandpass response to a broadband signal. In a novel variation on this impulse response method, a train of pulses is coherently accumulated providing precision calibration with a simple system. The basic concept is demonstrated using a pulse generator-accumulator setup realised in a Bedlam board which is a high speed digital signal processing unit. The same system was used at the Parkes radio telescope between 2–13 October 2013 and we demonstrate its powerful diagnostic capability. We also present some initial test data from this experiment. 相似文献
17.
18.
Wavelet Cleaning of Solar Dynamic Radio Spectrograms 总被引：5，自引：0，他引：5
RobertA.Sych Yi－HuaYan 《中国天文和天体物理学报》2002,2(2):183-192
By applying the state-of-the-art mathematical apparatus, the wavelet transformation, we explore the possibillity of a dynamic cleaning of raw data obtained with the Chinese solar radio spectrographs over a wide wavelength range (from 0.7 to 7.6 GHz). We consider the problem of eliminating the interference caused by combination rates of data sampling (10-20ms), and the low-frequency interference (4-30s) caused by the receiving equipment changing its characteristics with time. It is shown that the best choice to reconstruct a signal suffering from amplitude, frequency and phase instabilities, is by means of wavelet transformation at both high and low frequencies. We analysed observational data which contained interferences of nonsolar origin such as instrumental effects and other man-made signals. A subsequent comparison of the reference data obtained with the acoustooptical receiver of the Siberian Solar Radio Telescope (SSRT) with the “cleaned” spectra confirms the correctness of this approach. 相似文献
19.
20.
Yu. D. Zhugzhda 《Astronomy Letters》2006,32(5):329-343
A technique for analyzing periodic processes based on the introduction of an analytical signal is described. This technique allows the instantaneous frequency, amplitude, and phase of oscillations to be obtained. The data on solar brightness fluctuations collected with the DIFOS multichannel photometer onboard the CORONAS-F satellite are processed. The p-mode spectral lines are broadened mainly by amplitude fluctuations, while the frequency stability appears to be high (～10?4). A method for separating signals with close frequencies is developed. The p-mode with l = 0 and n = 21 is used as an example to show that the separation of signals with close frequencies is possible when the conventional spectral methods are inefficient. Analysis of the phase shifts between the oscillations observed in various optical channels of the DIFOS photometer has revealed that the five-minute oscillations travel from the upper and deep photospheric layers toward the middle photospheric layers. This effect directly proves that the evanescent p-modes in the photosphere are nonadiabatic. 相似文献