IEEE FELLOW Nomination – 2021

My fellow colleagues recently nominated me to be an IEEE FELLOW.  An IEEE Fellow is a distinction reserved for select IEEE members whose extraordinary accomplishments in any of the IEEE fields of interest are deemed fitting of this prestigious grade elevation. I was nominated by Dr. John Vig – former President of the IEEE.  The IEEE has about a half-million members from around the world.  I have received two previous IEEE AWARDS, and was made a “life senior member”

  1. 2016 IEEE/UFFC Achievement Award with the citation: “For seminal work to the UFFC community regarding time determination, time prediction, time dissemination, and timekeeping through contributions to atomic frequency standards, space-based navigation, time and frequency stability analysis, time-scale algorithms.”
  2. 2018 IEEE Keithley Award with the citation: “For leadership in time determination and precise timing instruments,” which included a $10,000 stipend that I gave to my church.

I just learned that my nomination was approved by the IEEE on 29 Dec. 2020.  About one in a thousand of the IEEE members receive the FELLOW status.  In the newly posted list of recipients for 2021, there were 129 USA recipients and two from Utah (Dr. Rajeev Balasubramonian of Salt Lake City, UT, USA, and myself).  My citation reads: “For contributions to timing systems and precision clocks.”

As a part of the nomination process, John Vig asked me to write a letter listing my awards:

Requirements for Fellow nomination

At the time the nomination is submitted, a nominee must:

  • have accomplishments that have contributed importantly to the advancement or application of engineering, science, and technology, bringing the realization of significant value to society;
  • hold IEEE Senior member or IEEE Life Senior member grade;
  • have been a member in good standing and has completed a minimum of five full years (consecutive or not) of IEEE membership in any grade preceding 1 January of the year of elevation.


In 2016, the IEEE/UFFC produced a Special Issue celebrating the 50th anniversary of my master’s thesis, which gave birth to the Allan variance including 16 papers.  That same year, I was given the highest IEEE/UFFC Award at International Frequency Control Symposium in New Orleans with the citation “For seminal work to the UFFC community regarding time determination, time prediction, time dissemination and timekeeping through contributions to atomic frequency standards space-based navigation, time and frequency stability analysis, time-scale algorithms, and time-keeping devices.”  And in 2018 I was given the $10,000 prestigious IEEE Keithley Award with the citation “For leadership in time determination and precise timing instruments.”

Over my 32 years at the National Bureau of Standards (NBS, now NIST) my colleagues and I have developed three measurement metrics, which became IEEE international standards in 1988: the Allan variance (AVAR), the Modified Allan variance (MVAR), and the Time variance (TVAR).  My 1965 master’s thesis gave birth to the Allan variance, and was published a year later in the 1966 February Proceedings of the IEEE, and has become one of the most cited publications to come out of the Department of Commerce.  The square root of these three variances is denoted: AVAR, MVAR, and TVAR.

As GPS was being developed, AVAR was used to assure that the performance of the atomic clocks needed to achieve the few billionths of a second synchronization requirements needed across the GPS satellite network was satisfied. ADEV, MDEV, and TDEV are used extensively by the time and frequency, navigation, and telecom communities, respectively.  I have been invited to give over a dozen lectures about my research across the globe, and I have received significant awards from all three of these communities.

In 1999, John Wiley and Sons asked me to write a colleague textbook on GPS and Precision Timing.  I had written THE SCIENCE OF TIMEKEEPING booklet for Hewlett Packard while consulting for them.  Their request was to basically make a college text of this 84-page booklet.

I started writing that book and then got side-tracked into some more interesting unified-field-theory (UFT) research since Einstein did not finish that work – showing how the four force fields in nature are tied together.  We did seven experiments validating this new UFT direction and got some very exciting results.  These results I published in 2014 in Chapter 21 of my book entitled IT’S ABOUT TIME.  The book is almost autobiographical.

I was our nation’s timekeeper for most of my 32 years in Boulder, CO, having written in 1968 the algorithm, AT-1, for the generation of time from an ensemble of atomic clocks.  With improvements by my colleagues in Boulder, AT-1 is still providing official time for the USA today.

I 1984 I was given the I. I. Rabi Award with the citation “for his contribution to the measurement and characterization of precision time and frequency sources.”  Professor Rabi is credited as the person to first think about atomic clocks for timing, and the award was named after him.  He was the first recipient, and I felt greatly honored to be the second.

I spent many years helping in the development of the GPS program, and the Institute of Navigation made me a fellow in 1999 because of my contributions to the GPS effort:  Outside of the GPS program sponsored by the DOT is the international Civil GPS Service Interface Committee (CGSIC), and I was the first chairman of the “Timing Sub-Committee” for the CGSIC and served there even after my retirement.

I have been privileged to write chapters in several technical books and most of my publications can be found on my other web site: .

  1. Education

Degrees                               Year                       Educational Institution                 Location

BS in Physics                      1960                       Brigham Young University            Provo, Utah

MS in Physics                     1965                       University of Colorado                   Boulder, Colorado

  1. Professional History

From     To                           Name of Company                                          Position Held

1960       1992                       National Bureau of Standards/NIST          Senior Scientist and Group Leader

1993       present                Allan’s TIME, LLC                                               President

1993       1997                       Consultant for Hewlett Packard                 Part of a team for the development of a special GPS receiver for synchronizing cell phone towers, and for the development of an Advanced GPS Common-view technique, and for writing the HP Application Note: The Science of Timekeeping.

2001       present                Allan’s Space Time Solutions, LLC               President

  1. Individual Contributions

5a.          Research Engineer/Scientist

First distinctive technical contribution:

Allan and colleagues developed three measures of clock performance: the Allan Variance, the Modified Allan variance, and the Time variance.  The Allan variance came out of his master’s thesis, where he derived that the classical variance and its square-root, the standard deviation, typically taught in statistics courses is not a good metric for characterizing the variations in precision oscillators and atomic clocks.  Taking the standard deviation of a data set is like taking a black and white picture of a rainbow – giving intensity but no color.  The metrics Allan and his colleagues have developed give full color to the different spectral density types useful in modeling precision oscillators and clocks.  All three of these metrics became IEEE standards in 1988.  The square roots of these are denoted ADEV, MDEV, and TDEV.  They became the main metrics for characterizing variability for the time and frequency, the navigation, and telecom communities, respectively.  A Google search of “Allan variance” yields over 100,000 hits.

Allan’s thesis showed that, for example, flicker-noise, which is a common-noise model for many precision oscillators and atomic clocks, the classical variance has no well-defined mean value nor does the variance converge to a well-defined value.  Whereas, Allan shows that ADEV converges quickly and is also very useful for not only flicker noise but for many other noise models used in characterizing precision oscillators and atomic clocks and that are also observed in nature.

In 1968, using ADEV and some other unique techniques, Allan wrote the time-scale algorithm, AT-1, for combining the readings of atomic clocks for official time for the USA.  With improvements by colleagues, it is still keeping official time today.  Some of Allan’s ideas were used by the International Bureau of the Hour (BIH) in writing the time-scale algorithm, ALGOS, which generates official time for the world, UTC and TAI.  ADEV was used while GPS was being developed to assure that the accuracy needed for the atomic clocks to be used in that system met specification.  Allan spent many years helping in the development of GPS.  Allan’s Division Chief, Dr. Donald Sullivan, nominated Allan for the DoC Gold Medal and stated, “He ‘wrote the book’ on the…methods [for characterizing clocks and time and frequency distribution systems] and the statistical variance he introduced is named after him. Mr. Allan is as well recognized in the field of time and frequency technology as any other figure in the world.”

Second distinctive technical contribution:

Allan and colleagues developed four precise timing instruments: 1) the Dual-Mixer Time-Difference (DMTD) has unlimited precision in measuring the time or phase difference between two clocks; it has been commercialized and is used throughout the world to measure ADEV and the spectral density phase noise of precision oscillators; 2) a GPS Common-view timing receiver with global precisions and accuracies approaching a nanosecond; it also has been commercialized and was used in synchronizing the NASA/JPL Deep Space Tracking stations and for communicating the times of atomic clocks across the world to the International Bureau of Weights and Measures (BIPM) for the generation of international time (UTC and TAI); 3) ACTS (Automatic Control Timing System) allowed NBS/NIST official time to be distributed to a remote modem by self-calibrating the round-trip time to remove the delay error; and 4) Allan consulted with colleagues at HP using his Smart Clock patent and TDEV to characterize the GPS nose and remove the civil signal degradation on GPS during 1993-1999.  Based on these ideas and technology along with HP’s staff, a special GPS receiver with excellent long-term hold over was developed, Model HP 58503, using HP’s outstanding quartz-crystal oscillator to make the receiver perform like an atomic clock.  These receivers were sold throughout the world for synchronizing cell-phone towers.

Before the invention of the DMTD, there were problems with previous measurement systems having dead-time in the data acquisition, which impacted adversely the statistical analysis of the performance of the clocks involved.  Also, the measurement noise was often larger than the clock noise.  The DMTD can be configured so that its noise is less than the clock noise being measured.

The GPS Common-view receivers were also used to measure the highly stable millisecond pulsar spin rates.  Allan installed one of these receivers at the Arecibo radio telescope.  Using the data taken he used ADEV to show that the electron-content across the 12 thousand-light-year path was a random-walk process.  He also showed evidence that the millisecond pulsar was a binary.  It was later shown to be so.  The GPS program office gave Allan’s group about a quarter-million dollars a year to do atomic-clock research and to characterize all the GPS clocks.  Allan and Marc Weiss inverted a five-by-five matrix to separate out the GPS noise components: clock noise, ephemeris error, clock-correction error, propagation noise, and reference clock noise.  This information was used to fine-tune the Kalman filter parameters.

  1. Evidence of Technical Accomplishments

First main item:

The IEEE/UFFC asked Allan to pull together a committee and act as chair to produce a standard for characterizing precision oscillators and clocks.  This standard was published in 1988 and Allan gave a paper at the International Frequency Control Symposium documenting the committee’s work.  It has been updated several times since, and has become an important standard for the time and frequency community.

The standard describes procedures for characterizing clocks and precision oscillators in both the frequency and time-domains and deals with important issues coming from environmental perturbations on clocks and precision oscillators as well.

ADEV, MDEV, and TDEV became internationally recognized standards with this 1988 IEEE publication, and its contents were summarized in the paper Allan gave for the committee at the 1988 IFCS.

Second main item:

Allan has over 100 papers on the NIST Time and Frequency Division’s web site documenting the work in item 5c above:   He has these listed on his web site as well along with some additional ones associated with his consulting work for HP and his research work with his company ASTS:   The HP 84 page Application Note, The Science of Timekeeping, is also available here as well.

Many of these papers list his research in other areas not covered in 5c above.  For example, as part of his ASTS research with the help from Bliley, Inc. and with the HP 58503 GPS receiver as a reference, he and his colleague, Gus German, were able to configure an oven-less, six-vector quartz-crystal oscillator ensemble going through 5-gs of acceleration and also through military specification temperature variations to perform instability like an atomic clock.  These results were shared at the IFCS in San Francisco.

Allan and German also did some Unified Field Theory research.  They demonstrated the possible existence of diallel-field lines.  They were able to modify the local gravitational field and demonstrate quantum transitions in these diallel-field lines.  These experiments are described in Chapter 21 of Allan’s book:

Third main item:

Allan has given several tutorials around the concepts in 5c above.  He was invited to give one for the PTTI planning meeting and for the Naval Research Laboratory atomic clock research group.  The UN-sponsored him to give a three-week lecture in the PRC on the topics in 5c above.  After his retirement from NIST in 1992, he organized and chaired the tutorial sessions each year for the IFCS from 1993 to 1997.

First additional item:

Bill Riley, who helped develop the rubidium gas-cell atomic clocks for GPS, saw the need and took the NBS/NIST clock stability software and concepts and developed STABLE 32.  Allan assisted Riley in this effort by testing and experiment with this software.  This software has several features.  It can characterize both the frequency-domain and time-domain performance and it can provide simulated data for the different noise-models characteristic of precision oscillators and atomic clocks.

The STABLE-32 software is handed out at the NIST Time and Frequency Seminars each year, and its usefulness is described as part of the seminar.

Second additional item:

Dr. Samuel R. Stein took the DMTD concept and improved on it significantly and made it a product for his company.  It has been bought out and transferred to different companies over the years, and improvements have been made to his technological.  As mentioned, the DMTD concept allows the measurement noise to be below the clock noise.  His various models compute ADEV and the frequency-domain performance of the clocks being measured.

Sam has been giving talks on this technology for several years at the annual Time and Frequency Seminars.

Third additional item:

Allan organized some of the first time and frequency seminars at NBS.  Originally, they were not held annually.  Those developing GPS came, as the NBS seminars were the best place to know the characteristics of atomic clocks and how to best use them.  Many of the ideas from these seminars have been incorporated into the design features of GPS.

Allan remembers giving a lecture when Brad Parkinson, who is considered to be the Father of GPS, was one of the students.

Dave Howe has done a terrific job of keeping these most useful seminars going.

Fourth additional item:

Allan’s colleagues have taken his ADEV equation and shown its usefulness in connection with potential accuracy and stability: ADEV may be shown to be proportional to the atomic-clock’s bandwidth divided by the clock’s quantum-transition frequency and by the signal to noise.  One sees immediately from this equation why optical atomic clocks have the potential to be 100,000 times better than microwave frequency clocks, which is where the definition of the “second” is today based on Cs-133’s transition frequency of 9 921 631 770 Hz.  From this equation, we see why a new definition of the “second” is forthcoming.

Fifth additional item:

Allan developed the Smart-Clock patent with colleagues at NIST just before he retired.  HP bought the rights to it for the development of their special GPS receiver designed to synchronize cell tower stations.  The patent has built into it the concept that a clock will always read the correct time within some error limits.  The concepts in this patent were integrated into the software for the HP 58503 GPS receiver along with a filtering function to remove the degradation on the civil GPS signal.  The quartz-crystal oscillator in the receiver then behaved like a synchronized atomic clock.

  1. IEEE Activities

7c. Leadership in Standardization Activities

Chairman for the committee on standards for characterizing atomic-clock and precision oscillator performance, which standard was made effective in 1988.  The committee worked on the preparations for this standard from 1985 until 1988.

7e. IEEE Journals and Magazines Editorship

Allan served the IEEE/UFFC as a peer reviewer of some of the papers relevant to his field of expertise for some years (1987-1992)

7f.  IEEE Conference Leadership Position (General Chair, Technical Program Committee/Member, Steering Committee member, etc.

Not sure of the dates, but Allan has chaired some of the IFCS sessions.  He was on the executive committee for several years for paper selection for the IEEE/UFFC IFCS meetings.

Allan organized and chaired the tutorial sessions for the IFCS during the years 1993-1997.

  1. Non-IEEE Activities

8a. The Institute of Navigation made Allan a Fellow in 1999 for his work with GPS.  Allan spent many-man-years working on GPS:

The National Physical Laboratory in Israel invited Allan to help them improve the atomic clock timing system for the State of Israel.  Allan made four trips there (1987-1992) and installed a GPS Common-view receiver for them to tie their atomic-clock ensemble to the BIPM data set for inclusion into the computation of UTC and TAI.

In 1969, the Italian government gave Allan a two-month visiting professor grant to help them with their atomic clock ensemble time generation system and to give a series of lectures.  They prepared a book of several of Allan’s papers to give to the students to go along with the lectures.

The DoT organized the international Civil GPS Service Interface Committee (CGSIC), and Allan was invited to be the first chairperson for the Timing Sub-committee, which he did until 1997.

8b. Because of his work with the millisecond pulsar community, Allan was invited to be a member of the International Astronomical Union and to chair a sub-committee on that topic.

Allan installed a GPS Common-view receiver at the Arecibo Observatory in 1984, which gave much better accuracy to their millisecond-pulsar acquired data.   He gave a time and frequency lecture to the Arecibo Observatory staff, and his subsequent analysis of the data using ADEV gave a new understanding of the random-walk properties of the electron content over the 12 thousand-light-year path.  The ADEV analysis also showed evidence of the millisecond pulsar being a binary, which was later shown to be the case.

The last millisecond pulsar sub-session he organized and chaired was held in August 1994 in Den Haag, Holland.  Allan had invited Dr. Michael Davis, who was the scientific director at the Arecibo Observatory, to lecture.   Dr. Davis shared that the lecture Allan had given his staff in 1984 was the first time he really understood how time was generated for scientific experimentation.

Allan represented the US at the ITU CCIR meetings in Geneva from 1975 to 1997, and he and Dr. Richard Sydnor were editors for a time and frequency handbook.

  1. IEEE Awards

9a. IEEE Level Awards

In 2016, Allan was awarded a Senior-life-time IEEE membership.

In 2018, Allan was given the $10,000 prestigious IEEE Keithley Award with the citation “For leadership in time determination and precise timing instruments.”

9b. IEEE Society Awards

In 1984, Allan was given the I. I. Rabi Award with the citation “for his contribution to the measurement and characterization of precision time and frequency sources.”  Professor Rabi is credited as the person to first think about atomic clocks for timing, and the award was named after him.  He was the first recipient, and Allan felt greatly honored to be the second.

In 2016, Allan received the highest IEEE/UFFC Award at the IFCS in New Orleans, with the citation, “For seminal work to the UFFC community regarding time determination, time prediction, time dissemination, and timekeeping through contributions to atomic frequency standards, space-based navigation, time and frequency stability analysis, time-scale algorithms, and timekeeping devices.”

In 2016, the IEEE/UFFC celebrated the 50th anniversary of the publication of Allan’s thesis, which gave birth to the Allan variance, by having a special issue.  Sixteen papers were published sharing varying dimensions of the usefulness of the ADEV along with some of its limitations.  A special anniversary session of the International Frequency Control Symposium was included in the symposium that year, and Allan was honored in being asked to chair that session.

9c. Non-IEEE Awards

In 2011, Allan was given the “Time Lord Award” by the International Sync Forum in Edinburgh, Scotland: is used throughout the international telecom community as a useful network synchronization characterization metric.

In 2014, Allan was invited to give the plenary talk at an International Symposium on Time and Space in Suzdal, Russia.  While there, the time and frequency laboratory, VNIIFTRI, honored Allan with a plaque signed by their chief scientists, with the statement that ADEV “…forms the golden foundation of modern T&F statistics,”

At the symposium, Allan was surprised with another plaque with the citation, “50 years Allan deviation… To the founder of the modern time and frequency measurement statistic…” signed by 40 of their top scientists.

In 2015, Allan was invited to St. Petersburg, Russia to an International Navigation Conference to give a paper, a talk, and chair a panel around the importance of the MDEV as an important metric for the navigation community.  Allan was again honored for his work at this conference.

  1. Proposed Citation

Seminal work in generating time, timing instrumentation, performance characterization of precision clocks, and timing systems.

David W. Allan