Equipment Clock Research Articles

Research on Clock Acquisition and Correction Technology of Measurement Equipment

Comprehensive energy metering and electricity market-oriented transactions under the dual carbon goals put forward higher requirements on the accuracy of metering equipment clocks. The existing inventory of metering equipment has complex specifications, complex communication methods, and difficult management. Because of different production years, the old version of the metering equipment has poor clock retention capability and insufficient automatic time synchronization function. In order to solve the problems of clock accuracy and time management of metering equipment, a wide-area hierarchical collection and synchronization technology of clocks is designed, a technical framework for clock collection and synchronization of equipment at all levels of the system is constructed, and the normal state of system equipment is strengthened and maintained through the method of serial broadcast time calibration. Clock, designed a time-calibration protocol for object-oriented metering equipment. This technology has been applied to the clock management of on-site metering equipment, and the qualified rate of metering equipment clocks has reached more than 95%, which has improved the automation level of metering equipment clock management, the efficiency of time schooling, and the timely rate of time schooling.

Twenty-Five Years of Applications of the Modified Allan Variance in Telecommunications.

The Modified Allan Variance (MAVAR) was originally defined in 1981 for measuring frequency stability in precision oscillators. Due to its outstanding accuracy in discriminating power-law noise, it attracted significant interest among telecommunications engineers since the early 1990s, when it was approved as a standard measure in international standards, redressed as Time Variance (TVAR), for specifying the time stability of network synchronization signals and of equipment clocks. A dozen years later, the usage of MAVAR was also introduced for Internet traffic analysis to estimate self-similarity and long-range dependence. Further, in this field, it demonstrated superior accuracy and sensitivity, better than most popular tools already in use. This paper surveys the last 25 years of progress in extending the field of application of the MAVAR in telecommunications. First, the rationale and principles of the MAVAR are briefly summarized. Its adaptation as TVAR for specification of timing stability is presented. The usage of MAVAR/TVAR in telecommunications standards is reviewed. Examples of measurements on real telecommunications equipment clocks are presented, providing an overview on their actual performance in terms of MAVAR. Moreover, applications of MAVAR to network traffic analysis are surveyed. The superior accuracy of MAVAR in estimating long-range dependence is emphasized by highlighting some remarkable practical examples of real network traffic analysis.

The Time Deviation in Packet-Based Synchronization.

The telecommunications industry has used the time deviation (TDEV) very effectively for specifying network equipment clock performance as well as the performance of timing signals generated by Central Office equipment such as primary reference clocks and building integrated timing supplies (BITS) and synchronization supply units (SSUs). We discuss here the development of TDEV, and the variations of TDEV motivated by the advent of packet-switching and the steady transformation of the telecom network from circuit-switched-based to packet-switched-based. We illustrate these with simulation of the performance of the precise time protocol (PTP) across a packet-switched network. We then apply published methods to automatically determine noise types, and use these to predict time dispersion from a master clock for a slave clock using these PTP packets to stay synchronized. The result shows how TDEV and the other deviations provide an extensive array of tools for telecom networks, as well as for general time and frequency applications.

Timing rearrangements of SEC and SASE slave clock chains due to non‐small input phase and frequency hits in synchronisation networks

AbstractIn the standard architecture of synchronisation network, chains of slave clocks (namely, stand‐alone synchronisation equipment, SASE, and SDH equipment clock, SEC) transfer timing along synchronisation trails. Hence, the need to assess precisely the performance of timing transfer along such chains, not only in stationary conditions, but also under transient rearrangements occurring after input phase and frequency hits, due for example to reference switching. If possible, system analysis should be carried out beyond the usual assumption of linear behaviour, which is rather restrictive holding only for small perturbations on the input.In literature, very few papers analysed chains of slave clocks. In this work, the non‐linear transient behaviour of SEC and SASE clock chains has been simulated in the time domain, in order to evaluate their timing rearrangements after non‐small phase and frequency hits on the reference signal. Both homogeneous and non‐homogeneous chains of SEC and SASE clocks have been studied in various configurations, assuming the classic analogue PLL scheme, in order to provide a useful and comprehensive survey, both in qualitative and quantitative terms, on the timing performance achievable when planning synchronisation trails of various type and length in a synchronisation network. Copyright © 2006 AEIT

Design of a 1.7-GHz low-power delay-fault-testable 32-b ALU in 180-nm CMOS technology

In this paper, we present the design of a 32-b arithmetic and log unit (ALU) that allows low-power operation while supporting a design-for-test (DFT) scheme for delay-fault testability. The low-power techniques allow for 18% reduction in ALU total energy for 180-nm bulk CMOS technology with minimal performance degradation. In addition, there is a 22% reduction in standby mode leakage power and 23% lower peak current demand. In the test mode, we employ a built-in DFT scheme that can detect delay faults while reducing the test-mode automatic test equipment clock frequency.

Design aspects and analysis of SDH equipment clocks

AbstractNetwork synchronization has gained increasing attention since the introduction of the Synchronous Digital Hierarchy (SDH), as network synchronization performance due to the SDH‐internal bit rate adaptation technique have a major impact on the phase transfer characteristic of SDH‐based networks. Excessive jitter or wander may result in bit errors or frame slips within digital exchanges. This paper discusses the requirements with respect to SDH Equipment Clocks (SEC), which are the basis for improved network synchronization. Two parameters have a significant impact on the phase error generated by the clock: the oscillator performance and the phase detector characteristic. This paper proposes a synthesizer‐based PLL structure employing a fixed frequency highly stable oscillator. A novel approach for an all‐digital phase detector provides enhanced resolution, thereby reducing the phase error. Analytical and simulation results demonstrate the feasibility of this approach.

Letter: PLL Bandwidth Impact on Slave Clock Output Short Term Stability

AbstractStarting from a fairly general slave clock reference model, a relationship between phase noise power spectral density and output stability expressed in terms of TIE, is used to evaluate. via numerical integration, actual clock behaviour in the case of SDH equipment clocks. This approach may prove very useful in designing synchronization for SDH based transport networks.

The role of time/frequency in navy navigation satellites

This paper discusses the role of time and frequency in three areas: 2) the operational Navy Navigation Satellite System, NNSS; 2) an experimental low-altitude navigation concept termed TIMATION; 3) proposals for advanced navigation satellites. These operating, experimental, and proposed systems all use concepts which allow the user to remain passive. The operational NNSS system uses the Doppler technique to establish user positions to ~100 m. In this concept, the frequencies received from the satellite are compared to the frequencies generated in the user equipment. One can also compare the time a signal arrives from a satellite clock to a time generated in the user equipment clock for passive ranging. The paper shows that this passive ranging problem is easily transformed to the celestial navigation problem. Extension of these techniques allows one to use satellites as clock transporters and hence to compare clocks located throughout the globe to 0.5 µs. Experimental results are shown. It has been possible to determine the effects of radiation on quartz crystals and to determine that this effect is due principally to protons. System concepts are described which show this clock/time technique can determine user position, velocity, and time continuously, accurately, and globally.