共查询到20条相似文献,搜索用时 156 毫秒
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介绍了一种采用锁相环技术(PLL)产生高稳定度正弦信号的宽频带频率合成器方案,在该系统中采用锁相环频率合成器芯片ADF4360-7设计锁相环电路.简要分析了该芯片的工作原理,并给出了频率合成器的电路参数.通过该系统实现的宽频带本振信号的输出频率范围达到500 MHz~1 GHz. 相似文献
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本介绍了一种高稳定锁相接收系统,这种系统不仅整体合一、体积小、而且性能优良、可靠性高,为氢频标的工种化、商品化提供了条件。它可以提高氢脉泽频标的长期频率稳定度,对影响氢脉泽频标中短期频率稳定度的旧的电子系统也有所改善。章详细介绍该系统的工作原理、设计原则和各项技术指标,并对环路的性能进行了分析,最后给出了该系统的实测应用结果。 相似文献
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《天文研究与技术》2015,(4)
简述了基于ROACH和Xilinx System Generator平台的接收机数字后端系统的设计与实现。介绍了Zoom-PFB算法原理,讨论了该算法的核心部分低通滤波和抽取的现场可编程门阵列(Field-Programmable Gate Array,FPGA)实现。针对谱线观测局部高精度分辨率的需要,给出了将400 MHz带宽分为带宽25 MHz的16个通道,对其中任一通道做通道数为6 k、频率分辨率为4 k Hz的频谱细化系统的具体设计方案。在实验室条件下,对该数字后端的性能进行了分析和测试,并以4.5 m口径X/Y结构天线进行银道面中性氢谱线观测检验其应用效果,验证了方案的可行性。 相似文献
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结合高精度原子钟频率稳定度测试系统的工作原理,介绍了测试系统的软件设计。基于软件的需求分析,运用对象模型方法,重点分析了系统的框架结构、自动测试流程和数据处理及其算法。实验结果证明,该软件可以实现测试过程的稳定和自动化。 相似文献
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概述了法国高层大气所空间综合孔径项目背景、科学目标以及有效载荷,介绍了该项目演示系统的基本工作原理,探讨了该演示系统的望远子系统、指向子系统、共相子系统和成像子系统,并分别给出了该演示系统在非共相控制和共相控制情况下对半导体激光器和白光点光源的成像结果,实验结果表明演示系统不同独立望远镜之间已经基本实现了共相成像。最后对该演示系统进行了总结,并指出该系统可以进一步优化之处。该演示系统对我国综合孔径成像实验研究具有一定的借鉴意义。 相似文献
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A wavelength calibration system based on a laser frequency comb (LFC) was developed in a co-operation between the Kiepenheuer-Institut für Sonnenphysik, Freiburg, Germany and the Max-Planck-Institut für Quantenoptik, Garching, Germany for permanent installation at the German Vacuum Tower Telescope (VTT) on Tenerife, Canary Islands. The system was installed successfully in October 2011. By simultaneously recording the spectra from the Sun and the LFC, for each exposure a calibration curve can be derived from the known frequencies of the comb modes that is suitable for absolute calibration at the meters per second level. We briefly summarize some topics in solar physics that benefit from absolute spectroscopy and point out the advantages of LFC compared to traditional calibration techniques. We also sketch the basic setup of the VTT calibration system and its integration with the existing echelle spectrograph. 相似文献
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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
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A broadband radio spectrometer has been put into operation at Bleien, Switzerland, to register the flare emission of the full
Sun. In the frequency range of operation, 0.1 to 4.0 GHz, both modes of circular polarization are recorded continuously. The
new system, Phoenix-2, has been developed from the experience with the previous Phoenix spectrometer. Improved, computer-controlled
focal hardware allows now a complete daily calibration, a more sophisticated calibration procedure, and monitoring of all
essential instrumental and environmental parameters. Calibrated data are now usually available the day after observation and
are accessible through the Internet. The scientific improvements include a larger frequency range of observation, a larger
number of completely recorded events due to full-day registration, more accurate measurements, particularly in circular polarization,
and more reliable operation. First observations are presented and quantitative results comparing the calibration with single
frequency instruments are reported.
Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1005194314845 相似文献
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Giulia Schettino Ernesto Oliva Massimo Inguscio Carlo Baffa Elisabetta Giani Andrea Tozzi Pablo Cancio Pastor 《Experimental Astronomy》2011,31(1):69-81
A spectrally filtered Optical Frequency Comb (OFC) laser is proposed as a versatile calibration source for astronomical spectrometers in the 1?C2 ??m spectral range. Such a source overcomes the limitations of current calibration lamps providing a uniform spectrum of equally spaced lines with similar intensity and extremely high long-term frequency stability. We present preliminary studies and results of a system which filters the OFC from a 100 MHz comb spacing to 16 GHz one, an adequate spacing for spectrometers with resolving power ????/???>30000. The first approach employs two Fabry-Perot cavities in series, made of dielectric coated mirrors, followed by a non-linear optical broadening system. The limitations of such a filtering process are discussed. These can be overcome by the second approach, based on filtering cavities with metallic coated mirrors. 相似文献
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卫星信道租赁费是目前卫星双向时间传递(Two-Way Satellite Time and Frequency Transfer, TWSTFT)的主要成本之一.在2017年5月以前,参与UTC (Coordinated Universal Time)计算的亚洲-欧洲实验室之间进行Ku波段卫星双向时间频率传递一直使用2.5 Mcps/s码速率,带宽为2.5 MHz的伪随机码.为了在不影响时间频率传递性能的前提下降低成本,在欧亚间首次尝试采用1 Mcps/s码速率,带宽为1.7 MHz的伪随机码,进行亚欧卫星双向时间传递.并使用已校准的GPS PPP (Global Position System Precise Point Positioning)链路为双向链路进行间接校准.选择2018年12月的TWSTFT链路数据,分析链路性能发现,通过ABS-2A卫星,使用1 Mcps/s码速率构建的卫星双向时间比对链路的日频率稳定度达到10~(-15),时间稳定度优于0.3 ns.与已校准的GPS PPP链路数据进行验证分析,结果表明,使用1 Mcps/s码速率进行超长距离卫星双向时间传递与已校准的GPS PPP时间传递结果一致,与传统手段相比,其系统造价低,时间传递性能可以满足国际原子时计算的需求. 相似文献
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A. Kontogeorgos P. Tsitsipis C. Caroubalos X. Moussas P. Preka-Papadema A. Hilaris V. Petoussis C. Bouratzis J.-L. Bougeret C. E. Alissandrakis G. Dumas 《Experimental Astronomy》2006,21(1):41-55
We present the improved solar radio spectrograph of the University of Athens operating at the Thermopylae Satellite Telecommunication
Station. Observations now cover the frequency range from 20 to 650 MHz. The spectrograph has a 7-meter moving parabola fed
by a log-periodic antenna for 100–650 MHz and a stationary inverted V fat dipole antenna for the 20–100 MHz range. Two receivers
are operating in parallel, one swept frequency for the whole range (10 spectrums/sec, 630 channels/spectrum) and one acousto-optical
receiver for the range 270 to 450 MHz (100 spectrums/sec, 128 channels/spectrum). The data acquisition system consists of
two PCs (equipped with 12 bit, 225 ksamples/sec ADC, one for each receiver). Sensitivity is about 3 SFU and 30 SFU in the
20–100 MHz and 100–650 MHz range respectively. The daily operation is fully automated: receiving universal time from a GPS,
pointing the antenna to the sun, system calibration, starting and stopping the observations at preset times, data acquisition,
and archiving on DVD. We can also control the whole system through modem or Internet. The instrument can be used either by
itself or in conjunction with other instruments to study the onset and evolution of solar radio bursts and associated interplanetary
phenomena. 相似文献
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Sarod Yatawatta 《Experimental Astronomy》2012,34(1):89-103
Interferometric calibration always yields non unique solutions. It is therefore essential to remove these ambiguities before the solutions could be used in any further modeling of the sky, the instrument or propagation effects such as the ionosphere. We present a method for LOFAR calibration which does not yield a unitary ambiguity, especially under ionospheric distortions. We also present exact ambiguities we get in our solutions, in closed form. Casting this as an optimization problem, we also present conditions for this approach to work. The proposed method enables us to use the solutions obtained via calibration for further modeling of instrumental and propagation effects. We provide extensive simulation results on the performance of our method. Moreover, we also give cases where due to degeneracy, this method fails to perform as expected and in such cases, we suggest exploiting diversity in time, space and frequency. 相似文献
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为提升高精度时间比对的可靠性, 结合卫星双向时间比对(Two-Way Satellite Time and Frequency Transfer, TWSTFT)和GPS精密单点定位(Precise Point Positioning, PPP)时间比对长短稳特性, 利用稳定度加权、Vondrák-\vCepek组合滤波以及 Kalman滤波融合方法对中国科学院国家授时中心(National Time Service Center, NTSC)和德国物理技术研究院(Physikalisch-Technische Bundesanstalt, PTB)间的TW-STFT和GPS PPP时间比对结果进行了融合处理并对3者进行了比较分析. 结果表明, 3种融合算法对于TWSTFT中的周日效应以及GPS PPP结果的``天跳''现象都有不同程度的改善, 融合结果与GPS PPP链路差值(Double Clock Difference, DCD)结果的绝对值保持在链路校准的不确定度范围内. 3者1d的时间和频率稳定度可以达到亚纳秒和10-15量级, Vondrák-\vCepek融合方法1d以内的稳定度最高, 适用于对短稳要求高的时间比对链路的融合. 稳定度加权、Kalman滤波融合保真度较好, 适用于对准确度要求高的时间比对链路融合. 相似文献
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用GPS校准计算机系统时间 总被引:1,自引:0,他引:1
文章介绍了一种计算机时间校正系统,该系统利用GPS提供标准时间,采用UNIX C作为编程语言,具有良好的兼容性,可移植性,可以方便地用于计算机系统时间的校正。 相似文献