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Search Publications by: Michael A. Lombardi (Assoc)

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Displaying 1 - 25 of 146

Dissemination of UTC(NIST) over 20 km of commercial optical fiber with active phase stabilization

May 2, 2024
Author(s)
Jacob VanArsdale, Matthew J. Deutch, Michael A. Lombardi, Glenn Nelson, Jeffrey Sherman, James Spicer, William Yates, Dylan Yost, Samuel Brewer
We demonstrate the transfer of a cesium frequency standard steered to UTC(NIST) over 20 km of dark telecom optical fiber. Our dissemination scheme uses an active stabilization technique with a phase-locked voltage-controlled oscillator. Out-of-loop

Measuring the Frequency Accuracy and Stability of WWV and WWVH

March 1, 2023
Author(s)
Michael A. Lombardi
Radio station WWV, famous for the "at the tone ...." announcements broadcast at the top of each minute, is known to shortwave listeners and radio amateurs worldwide as a trusted source of accurate time. However, you might not know that the original purpose

Measurement of Transient Environmental Effects in GPS-Disciplined Clocks

January 23, 2023
Author(s)
Andrew Novick, Michael A. Lombardi, Demetrios Matsakis, John Clark
GPS-disciplined clocks (GPSDCs) are designed to optimize the accuracy and stability of their pulse-per-second (PPS) and frequency outputs by steering an internal oscillator to the timing solution from a GPS receiver based on the received satellite signals

Measuring the Timing Accuracy of Satellite Time and Location (STL) Receivers

January 23, 2023
Author(s)
Peter Johnson, Andrew Novick, Michael A. Lombardi
We present measurements of the timing accuracy and stability of Satellite Time and Location (STL) receivers with respect to UTC(NIST), the coordinated universal time scale (UTC) operated by the National Institute of Standards and Technology (NIST). STL is

Time Transfer using High-Definition Television (HDTV) Broadcast Transmitters in Common View

January 23, 2023
Author(s)
Konstantin Tarasov, Bethany Bauer, Sebastian Olsen, Eugene Graver, Howard Feil, Jeffrey Sherman, Aidan Montare, Matthew J. Deutch, Glenn Nelson, Michael A. Lombardi, Timothy Marczewski, David A. Howe
We have developed and demonstrated a time transfer system using high-definition television (HDTV) broadcast signals in common view. The system is comprised of a software defined radio (SDR), a TV antenna, a digitally programmed crystal oscillator (DOCXO)

A Resilient Architecture for the Realization and Distribution of Coordinated Universal Time to Critical Infrastructure Systems in the United States: Methodologies and Recommendations from the National Institute of Standards and Technology (NIST)

November 3, 2021
Author(s)
Jeffrey Sherman, Ladan Arissian, Roger Brown, Matthew J. Deutch, Elizabeth Donley, Vladislav Gerginov, Judah Levine, Glenn Nelson, Andrew Novick, Bijunath Patla, Tom Parker, Benjamin Stuhl, Jian Yao, William Yates, Michael A. Lombardi, Victor Zhang, Douglas Sutton
The Time and Frequency Division of the National Institute of Standards and Technology (NIST), an agency of the United States Department of Commerce (DOC), was tasked with fulfilling Section 4, Part (i) of the Position, Navigation and Timing (PNT) Executive

Synchronizing Stock Market Clocks to UTC(NIST)

August 29, 2020
Author(s)
Michael A. Lombardi
To reduce the possibility of fraudulent activity and market manipulation, the world's major stock exchanges require every clock involved in a stock market transaction to be synchronized to agree with a common reference clock that keeps accurate and

Comparison of the multi-national SIM time scale to UTC and UTCr

July 1, 2020
Author(s)
J. M. Lopez, Michael A. Lombardi, E. de Carlos, N. Munoz, C. Ortiz, M. Gertsvolf, R. de Carvalho, R. Solis
The Sistema Interamericano de Metrologia (SIM) is one of the world's five major Regional Metrology Organizations (RMO's) recognized by the International Committee for Weights and Measures (CIPM). With the goal of allowing SIM National Metrology Institutes

Metrological and legal traceability of time signals

March 1, 2019
Author(s)
Michael A. Lombardi, Demetrios Matsakis, Judah Levine
Metrological traceability requires an unbroken chain of calibrations that relate to a reference, with each calibration having a documented measurement uncertainty. In the field of time and frequency metrology, the desired reference is usually Coordinated

Rethinking Timekeeping for Modern IT Solutions

January 28, 2019
Author(s)
Son VoBa, Charles L. Ulland, Michael A. Lombardi, Arno Lentfer
Advances in processor performance and virtualization technologies, together with complexities of operating systems (OS) and software defined networking, have outpaced legacy network-based solutions for keeping system clocks accurate across geographic

SIM Time Scale: 10 years of operation

March 29, 2018
Author(s)
J. M. Lopez, Michael A. Lombardi, E. de Carlos, N. Munoz, C. Ortiz
The Inter-American Metrology System (SIM) is one of the world's five major Regional Metrology Organizations (RMO's). Starting in 2005, the SIM Time and Frequency Metrology Working Group (SIM TFWG) developed a time and frequency comparison network for the

Metrological and legal traceability of time signals

January 30, 2018
Author(s)
Demetrios Matsakis, Judah Levine, Michael A. Lombardi
Metrological traceability requires an unbroken chain of calibrations that relate to a reference, with each calibration having a documented measurement uncertainty. In the field of time and frequency metrology, the desired reference is usually Coordinated

Improving packet synchronization in an NTP server

January 29, 2018
Author(s)
Andrew N. Novick, Michael A. Lombardi, Kevin Franzen, John Clark
A computer or dedicated client can use the Network Time Protocol (NTP) to synchronize an internal clock to a server that is synchronized by a 1 pulse-per-second (pps) signal from a national timing laboratory. Measuring an NTP server on a local area network

The effects of the January 2016 UTC offset anomaly on GPS clocks monitored at NIST

January 31, 2017
Author(s)
Jian Yao, Michael A. Lombardi, Andrew N. Novick, Bijunath Patla, Jeffrey A. Sherman, Victor S. Zhang
Errors in the Coordinated Universal Time (UTC) offset parameters broadcast by Global Positioning System (GPS) satellites caused many thousands of GPS clocks to be in error by approximately -13 µs on January 25-26, 2016. The erroneous UTC offset information

Accurate, Traceable, and Verifiable Time Synchronization for World Financial Markets

October 7, 2016
Author(s)
Michael A. Lombardi, Andrew N. Novick, George Neville-Neil, Ben Cooke
This paper describes how the National Institute of Standards and Technology (NIST), through a collaboration with Perseus, is providing accurate, traceable, and verifiable time synchronization to stock exchanges in the United States, Europe, and Asia. The

Timekeeping in the Americas

October 1, 2015
Author(s)
Michael A. Lombardi, Jose M. Lopez
Time and its measurement belong to the most fundamental core of physics, and many scientific and technological advances are directly or indirectly related to time measurements. Timekeeping is essential to everyday life, and thus is the most measured

Practical Limitations of NTP Time Transfer

April 12, 2015
Author(s)
Andrew N. Novick, Michael A. Lombardi
The Network Time Protocol (NTP) is commonly utilized to synchronize computer clocks in packet-switched, wide area networks (WANs) such as the public Internet. The delay asymmetry in WANs, often due to inconsistent routing and/or bandwidth saturation, is