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本文叙述了利用电视信号场道程第16行和329行插入标准时频信息,由同步卫星进行标准时间频率的发播,讨论了由于卫星运动而引起的多普勒频率的计算、多普勒频率和卫星延时对用户接收标准时频信号的影响,着重介绍了补偿原理,并给出了实验结果。经补偿后,主站附近地区的校频准确度高于5×10(-12)/30min,频率稳定度高于3×10(-12)/30min,时间不确定度小于100ns;国内其它地区的校频准确度预期最低可达1×10(-10)/30min。 相似文献
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本文介绍了常用UHF电视扫频仪XSQ-4A、NW5312、QH5320等的几项重要技术特性,如频标信号频率准确度、输出功率或输出电平,平坦度,输出衰减器等,并讨论了指标的检定计量、标准设备选用以及如何提高计量检定精度等. 相似文献
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本文所述的转速标准装置系采用差频稳速系统,用频率综合器作为频率给定,控制部分采用线性差频器和逻辑差频器并联方案,调节部分采用可控硅供电的双环路调节系统,测量部分采用频闪测速系统,且用数字测速法作旁证。整个装置的测量范围为50~100000转/分,准确度优于±5.0×10~(-5)。 相似文献
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IEEE1588精确时间同步技术作为一个标准。它第一次实现了不同末端设备之间基于网络的高精度时间同步。同步精度小于1个μs 。本文主要介绍了这一协议的工作方式。如何使用和实现。以及可以达到的同步精度。 相似文献
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一、概述
1.测量依据
JJG181-2005《石英晶体频率标准检定规程》、JJG180-2002《电子测量仪器内石英晶体振荡器检定规程》。
2.测量环境条件
可处于15℃-30℃范围内任一点,温度最大允许变化范围为±2℃,相对湿度不大于80%。
3.测量标准铷原子频率标准、PO7D频标比对器,输出范围及功能满足被测仪器的要求。
4.测量对象石英频率标准PO16M。 相似文献
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彩色电视付载波频率传播的稳定性已为许多国家的科技工作者所肯定。利用彩色电视付载波校频是一种简单经济的方法,目前不少单位正在积极研究,并已取得一定成绩。一九七八年,我们开始做了一些工作。在选取电路方案时,若采用频差倍增法,需要有组成倍频器和混频器的调谐回路,因而不便于实现集成化。本文介绍一种基于差频周期法和取样鉴相原理并集成化的彩色电视付载波校频电路。其结构简单,成本低廉,可靠性高。同时,又能缩短校频时间。 相似文献
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Wei Zhou 《IEEE transactions on instrumentation and measurement》1994,43(6):945-946
The conventional frequency calibration devices using the color television subcarrier, utilize a frequency synthesizer to generate the calibrated frequency signal into the signal which is the same in nominal frequency with the chroma subcarrier signal. Then it is calibrated by the phase comparison method with the 3.57 MHz chroma subcarrier signal. This paper describes a new method and does not use the frequency synthesizer but uses a simpler device to accomplish the calibration. The measuring accuracy is better than that of conventional devices 相似文献
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Low frequency (LF) voltage and current are important parameters in electrical metrology. The standards for LF voltage and current are established by assigning AC–DC transfer difference to thermal devices, i.e. thermal converters or thermal transfer standard along with current shunts. Automated calibration systems have been developed based on Null method and measurement technique developed by Budovsky for calibration of precision calibrator in LF voltage and current against thermal devices. The technique based on the Algorithm developed by Dr. Ilya Budovsky (National Metrology Institute (NMI), Australia) has been compared with the conventional null technique. Indigenously developed software has been used to calibrate the precision calibrator in the entire LF voltage and current range using Holt thermal converters and current shunts. Calibration results at 1 V, 10 V in the frequency range from 10 Hz to 1 MHz as well as calibration results of 1 A in the frequency range from 40 Hz to 10 kHz are presented in this paper. These result shows that the measurement technique developed by Budovsky has reduced the complexity of AC–DC transfer measurements, measurement time and the uncertainty in measurement. 相似文献
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《IEEE transactions on instrumentation and measurement》1968,17(1):56-68
The design of a system for the synthesis of one frequency from another is discussed in terms of mathematical methods of approximating real numbers, the ratio of the frequencies being the number approximated. A general equation describing the frequency synthesis process is derived and it is shown, using charts, how block diagrams for a frequency synthesizer can be developed from the solutions of this equation. Examples are given for a synthesizer which compares the frequency of an ammonia N15H3 maser with a standard frequency of 5 MHz, and for a synthesizer which offsets a standard frequency of 100 kHz by steps of 1×10-5 Hz. 相似文献
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提出了一种将标准短路试验波形注入多通道任意波形发生器,来产生模拟实际的校准波形,进而对测量系统进行校准的方法。校准装置使用现场可编程门阵列(FPGA)、直接数字频率合成器(DDS)等器件。对装置的检定结果表明:在10 Hz^200 kHz频率范围内,输出频率、输出电压最大误差分别为2.1×10^-6、3×10^-3。重复输出10次,输出幅值的最大相对标准偏差为5.7×10^-4,1年内幅值变化的最大相对标准偏差为1.9×10^-4。通过将该装置用于实际高压短路试验测试系统的校准,验证了试验波形的噪声、零漂及带宽均会对测量系统的准确度产生显著影响。 相似文献
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Gammell PM Maruvada S Harris GR 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2007,54(5):1036-1044
Time-delay spectrometry (TDS) is a swept-frequency technique that has proven useful in several ultrasonic applications. Commercial TDS systems are available, but only in the audio frequency range. Several ultrasonic research TDS systems have been constructed, and they have been used effectively for substitution calibration of hydrophones and for measurement of attenuation and sound velocity in materials. Unfortunately these systems depend on features of commercial equipment no longer manufactured, so a new system has been designed using modern equipment and straightforward signal processing. This system requires a frequency source with a reasonably linear sweep of frequency versus time, audio frequency filters, a standard double-balanced mixer, a power splitter, a waveform digitizer capable of handling audio frequency signals, and a personal computer. An optional implementation that shifts the signal to a lower frequency for more convenient digitization and easier velocity measurements additionally requires an audio frequency oscillator and an audio-range analog multiplier. The processing steps are performed with standard signal processing software. To demonstrate the operation of the system, substitution calibration measurements of hydrophones as well as attenuation measurements on a tissue mimicking material were obtained and compared to a custom TDS system previously described by the authors. The data from these two TDS systems agree to within +/- 0.5 dB in the 1-10 MHz frequency range used. Higher frequency source transducers could be used to extend this range. 相似文献
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为解决光纤时间传递系统中存在的远距离传递准确度低的问题,分析了环回法、双纤双向时间同步、双向波分复用、双向时分复用四种主流的高精度光纤时间传递方法的基本原理和技术特点,在此基础上研制了单信道时频传递装置。该装置采用电学相位补偿法实现频率传递同步,采用环回法与时分复用相结合的方法实现时间传递同步;使用1 秒脉冲(Pulse Per Second, PPS)和100 MHz共同标记时刻信号,其中1 PPS作为时刻粗标记,100 MHz作为时刻细标记,实现高精度时间同步。经实验证明,单信道时频传递装置的不确定度约为13 ps,能够满足现有光纤时频同步网计量校准的要求。该装置在多级时间传递同步、光纤时频同步网计量校准等领域中具有广阔的应用前景,为建设高稳定性、高可靠性和高精度的授时体系提供了重要技术支撑。 相似文献
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声呐系统性能检测需要一种多通道可控相位信号和多通道大容量高速数据采集系统。通过多种高速数据采集和信号发射方案的对比,选用基于图形化编程语言LabVIEW和相应的硬件设备,设计、研制了一种32通道发射和128通道高速数据采集系统,用于多数声呐系统的性能检测。发射系统利用直接数字合成技术,生成可以单独调节相位的32通道正弦信号;采集系统采用分块读取减少缓冲区数据占用的方式,实现有限数据采集,并采用减少显示图形更新次数、使用DAQmx配置记录函数等方法,实现连续数据采集。测试结果表明,系统实现在采样率为2 MHz时,128通道中每通道1 300 000点的有限数据采集,以及采样率最高为0.7 MHz的128通道的连续数据采集。利用该系统对高分辨率测深侧扫声呐的发射信号进行检测,发射信号正常,系统工作良好。 相似文献
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《IEEE transactions on instrumentation and measurement》1984,33(1):55-58
After giving a brief summary of the main devices allowing the measurement of phase shifts between two sine signals in the approximate range 1 Hz-1 GHz, we propose a new apparatus for measuring phase shift. The principle of this apparatus uses a heterodyne technique in association with a phase-locked loop which brings about frequency translation of the measured signals. The intermediate frequency which is obtained is small with respect to the frequencies studied conveying a high degree of selectivity to the apparatus. This allows measurements to be made on signal with noise or low-level signal while also maintaining good accuracy. For a system operating from 1-300 MHz, we have obtained phase linearity of ± 1°, resolution of 0.1°. In obtaining the accuracy of ± 5°, the sensitivity is -86 dBm in the 1-30-MHz frequency range; with 300 MHz the sensitivity reached is -68 dBm. 相似文献