DESCRIPTION
OF WORK FOR
DAVID A. HOWE
NIST TIME AND FREQUENCY DIVISION
2000 TO PRESENT
1994 TO 2000
Signal and Noise Analysis
Time and Frequency Seminars
New Document
Standards for Tests of Stability
Telecommunications,
Internet, and Cell Phone Advancements
Navigation
and Timing Research using Global Positioning System
Quartz Oscillator
Research and Development
Computer Science
and Related Skills
Training,
Certification, and Consulting
1984 TO 1994
Advanced Time
Dissemination Research
Global Network Synchronization
Spread Spectrum Modem Design
and Development
1974 TO 1984
Error and
Accuracy Analysis of U.S. Atomic Time Standard
Frequency and Time
Standards Research
Hydrogen Maser Development
Ammonia Utility Standard
Atomic Beam
Measurement System
Digital Servo Techniques
Precision Power Spectrum and Phase Noise
Measurements
1970
TO 1974
Time and Frequency Broadcast Research
High Power Radio Work at 20
kHz, 60 kHz, and
100 kHz VLF Mode
Television Time Distribution
Television Captioning System
Navigation Studies
HOWE TECHNOLOGIES CORPORATION
Advanced Operator Console for
Radio and TV Stations
Automatic Stereo Phase-Error Correction
Responsibilities as Chief
Executive Officer
NIST TIME AND FREQUENCY DIVISION ^
From June 1970 to the present, I have worked in three different sections
(now called "Groups") of the National Institute of Standards and
Technology (formerly National Bureau of Standards), Time and Frequency
Division. They are Atomic Time Standards, Dissemination Research and Services,
and Frequency Standards Research. The Time and Frequency Division provides the
basic standards for the
2000 TO PRESENT:
^
1. Precision Power Spectrum, Phase-Noise, Electrical, and Time-interval Measurements
I have done extensive work related to making precise signal and noise
measurements, particularly phase-noise measurements, for signal carriers
ranging from below 1 Hz to100 GHz. This work requires expertise in many
topics related to fundamental circuit design and electronic and electromagnetic
theory and measurements. I am proficient in:
[ ] Network and circuits analysis, and equivalent
circuits
[ ] Pulse power measurements, pulse amplification, and pulse distribution
[ ] Filter design (Butterworth, Chebyshev, FIR and IIR, recursive,
constant-delay, multi-tap, etc.)
[ ] Scattering parameter estimation, Bode plots, Smith charts
[ ] Fast rise-time detection and related noise uncertainty analysis
[ ] Wideband analog-to-digital (ADC) and digital-to-analog (DAC) conversion
schemes
[ ] Dielectric coefficient measurements, dielectric loss, and loss tangent
[ ] Laplace and z transforms, Maxwell's equations
[ ] Windowing and sidelobe leakage suppression
[ ] Digital filter design and characterization
[ ] Time-frequency domain, and related convolution-multiplication and scaling
effects
[ ] Spectral aliasing
[ ] Frequency synthesis (using direct digital, PLL, multiplication-division,
programmable array logic, etc.)
[ ] Noise suppression (using cross-correlation spectral
analysis, negative feedback, synchronous lock-in methodologies, etc.)
[ ] Multiresolution signal decomposition and signal reconstruction
[ ] Design of all-pass equalizers, delay-line filters, and complex-conjugate
matched filters
[ ] Impedance transforms and reactance and resistance matching network design
[ ] Analysis and reduction of media phase and frequency dispersion, standing
waves, multipath, and transmission-line loss
[ ] Electrical-length measurements (for example, accurate phase and group
velocity estimation)
[ ] Uncertainty analysis of volt and resistance standards
[ ] Essentially all signal modulation schemes
[ ] Single and multi-mode optical fiber delay measurements
[ ] Directional couplers, bridge couplers, and circulators
2. Quartz Oscillator Research and Development
Considering that quartz oscillators are used in various capacities in virtually
all frequency-dependent electronic systems, I have extensive background in the
research and development of key improvements which have been made in quartz
oscillators in the last 25 years. These include:
[ ] Vibration and acceleration sensitivity analysis and reduction
[ ] Phase noise measurements for radar characterization
[ ] Oven control, intrinsic (dual-frequency mode) and internal temperature
sensing
[ ] Low-noise active and passive component selection and design
[ ] Environmental sensitivity and its reduction
[ ] Estimating frequency predictability, aging, and frequency drift
[ ] Miniaturizing, ruggedizing and configuring oscillator hardware
[ ] Detecting and eliminating frequency steps
[ ] Phase-locked loop design, frequency-locked loop design
[ ] Reduction of cost and power-requirements
1994 TO 2000: ^
For this six-year period, I conducted measurement analysis, statistical research, and system modeling and clock prediction testing within the Atomic Time Standards Group.
I was reassigned in 1994 to lead measurement analysis and statistical research within the Atomic Time Standards Group. This group is responsible for maintenance of the SI physical standard of time interval, the "second," used as the basis of Universal Coordinated Time.
1. Signal and Noise Analysis ^
The work I perform relates to the generation and maintenance of Universal
Coordinated Time (UTC). At NIST's highest level, oscillator and system
noise must be well characterized with world class precision and accuracy.
This requires a thorough understanding of standards, physical signals, various
protocols, and a myriad of analysis techniques. In particular, I have intimate
knowledge, experience, and problem solving abilities with respect to references
and measurements of those references, specifically topics related to (1) random
noise processes and uncertainties, (2) systematic or deterministic processes,
(3) optimum prediction, (4) statistical combining, known as
"ensembling," and (5) synchronization methodologies. I am
proficient in the following subjects:
[ ] Statistical studies (population statistics, time-series analysis, etc.)
[ ] Variance, covariance, and auto-covariance analysis
[ ] Degrees of freedom and equivalent degrees of freedom
[ ] Statistical bias and signal-processing bias (for example, in servo systems,
limited-live data, multipath, code correlations, etc.)
[ ] Cross- and auto-correlation functions, orthonormality, stationary and
ergodic criteria
[ ] Confidence intervals, uncertainty, and error analysis
[ ] Regression analysis
[ ] Stochastic modeling
[ ] Applied probability
[ ] Estimation and prediction of systematic effects
[ ] Maximum likelihood estimation
[ ] Frequency response functions
[ ] Time, frequency, scale, and phase domain analysis
[ ] Computer simulation
[ ] Integral and differential vector calculus, numeric and analytic problem
solving
[ ] Perturbation theory
[ ] Distribution functions (normal, Gaussian, Chi-square, t, etc.)
[ ] Finite differences, structure functions, and interpolation techniques
[ ] Matrices and linear transforms
[ ] Characterization of noise (white, flicker, random-walk, etc.) and pseudo-noise
codes (Gold, MLS, etc.)
[ ] Power measurements and power spectrum estimation, and power-spectral
density
[ ] Fourier transform techniques (discrete spacial, discrete time, continuous,
fast-fourier, etc.)
[ ] Window functions (rectangular, Hamming, Hanning,
cos-squared, Gaussian, etc.)
[ ] Leakage effects, truncated data effects, zero-padding effects
[ ] Wavelet analysis, transforms, mother wavelet functions, basis functions
(Haar, Daubechie, Mex-hat, etc.)
[ ] Modeling and prediction (using wavelet coefficients,
Kalman, auto-regressive moving-average--ARMA, etc.)
[ ] Data compression and expansion algorithms, secure-data, and data encription
techniques
[ ] Maximum entropy method
2. Time and Frequency Seminars ^
For over 20 years, I have been the technical director for principle courses and seminars given to scientists and managers involved in any aspect of time, time synchronization and frequency. I have prepared valuable, detailed, timely notebook and lecture material which, until 2002, had been available for several hundred dollars per copy. No longer available on demand, a Division policy now requires seminar enrollment and participation in order to obtain this large two-volume set of lecture material.
Seminars and courses typically include other experts who I assign and work with in particular subjects and who lecture on relevant standards, metrology, and technology issues. Consulting services and workshops are typically done by myself.
Along with my skills as a teacher which I developed over many years as a lecturer at NIST, I have been applauded numerous times for my basic speaking, entertainment, and organizational skills. Basic skills originally formed while I worked as a commercial radio on-air personality for 7 years in high school and college at top-ranked FM radio stations in Denver [see Howe Technologies section, below]. The organizational skills were necessary to lead the NIST seminars.
3. New Document Standards and Tests for Stability ^
Since the classical standard variance is not a suitable measure of oscillator and/or system instability, noise level and type, the Allan variance developed at NIST in 1965 has been the standard statistic for determining these fundamental parameters. I developed a new variance beginning in 1995, now called Total variance, which specifies oscillator and network instability with unprecedented precision and accuracy, particularly for long averaging times, and considerably better than the Allan variance which has poor long-term confidence. This advancement for system developers, manufacturers and users made Total variance an immediate IEEE recommended statistic for specifying all oscillator-related system instability measurements [IEEE 1139-1999: Standard Definitions of Physical Quantities for Fundamental Frequency and Time Metrology - Random Instabilities].
4. Telecommunications, Internet, and Cell Phone Advancements ^
Time synchronization is the foundation for most modern and all future large communications networks. Wide bandwidth time-division and code-division multiple-access protocols (called TDMA and CDMA) depend directly on the synchronization of a large number of oscillators which time the signals which are redirected through various nodes, base transceiver stations, routers, and switchers. I recently generalized the Total approach to encompass a broader range of models and noise classes for efficiently assessing network stability using such information carriers as spread-spectrum, wireless CDMA (cell phones), and Internet-based and specialized military networks. Using and interpreting what is called the "modified Total" variance, I was able to develop quick, short-cut wavelet transform, Kalman, and auto-regressive moving-average (ARMA) predictive algorithms for steering these local network oscillators during loss-of-lock, or what is called "oscillator holdover" periods. Holdover specifications set the single most crucial limit for how long the network continues to operate during any one of a variety of loss-of-lock scenarios. I consult to major cell phone and telecommunication service providers who find a constant need to protect services, especially during holdover, while data traffic is projected to increase at exponential rate in some areas.
Worse than a simple loss-of-lock scenario, network timing loops occur when a local oscillator loses normal synchronization to a higher stratum (when stratum 1 to 4 architecture is used), whereupon the local oscillator seeks any suitable reference timing signal, but ultimately finds itself to lock to. I consult to conventional telephone service providers who must comply with standard stratum 1 to 4 frequency synchronization topologies within their networks and who must detect and eliminate timing loops without reducing bandwidth or disturbing normal communications and operations.
5. Navigation and Timing Research using the Global Positioning System ^
Since its inception, I have worked closely with the
[ ] Common view time transfer
[ ] Two-way time transfer
[ ] Specifying, estimating, improving, and/or correcting node-oscillator drift
and aging
[ ] Ring laser gyro and various inertial navigation systems
[ ] Broadcast services (for example, WWVB, Loran, etc.)
[ ] Fixed satellite service
[ ] Laser ranging
[ ] Fiber optic data communications
[ ] Oscillator combining, developing and testing ensemble algorithms, and
redundant systems analysis
[ ] Managed and administered real-time optimization of network topology
[ ] Automated computer time services
[ ] Real-time time-interval noise analysis (called "cluster"
analysis) for isolating and correcting cause of noise in a system
[ ] Automatic seek of lock to highest available stratum reference
[ ] Wide area augmentation systems (WAAS) and local area augmentation systems
(LAAS)
[ ] Differential GPS
6. Quartz Oscillator Research and Development ^
Considering that quartz oscillators are used in various capacities in virtually
all frequency-dependent electronic systems, I have extensive background in the
research and development of key improvements which have been made in quartz
oscillators in the last 36 years. These include:
[ ] Vibration and acceleration sensitivity analysis and reduction
[ ] Phase noise measurements for radar characterization
[ ] Oven control, intrinisic and internal temperature sensing
[ ] Low-noise active and passive component selection and design
[ ] Environmental sensitivity and its reduction
[ ] Estimating frequency predictability, aging, and frequency drift
[ ] Miniaturizing, ruggedizing and configuring oscillator hardware
[ ] Detecting and eliminating frequency steps
[ ] Phase-locked loop design, frequency-locked loop design
[ ] Reduction of cost and power-requirements
7. Computer Science and Related Skills ^
The maintenance of time synchronization among standards laboratories is typically labor-intensive, requiring a great deal of manual work to setup equipment and collect data, if these procedures are not automated. From January, 1994, to May, 1995, I studied options dealing with the implementation of a variety of computer architectures, with the ultimate goal of integrating the time from advanced world-wide frequency standards labs using two-way satellite-time transfer, or TWSTT (see item 1, next section), as efficiently as possible into NIST's existing atomic time-scale computer and without sacrificing performance criteria. This required theoretical analysis, modeling, and optimizing of computer logic, programming sequences, architecture, and choice of programming language to achieve a maximum level of automation, speed, and uncompromised performance. My formal background in math, physics, and electronics enabled me to perform computer science tasks to complete this study, in addition to other subsequent computer-related tasks, having done extensive necessary followup programming and having built a variety of facilities world-wide which use both PC and frame computers.
I have installed servers and contributed significantly to NIST's Automated
Computer Time Service (ACTS) and the Internet time service. The following
is a list of my various skills related to this work:
[ ] Proficient on computer operating systems: NT, workstation NT, PC Windows
platforms, Alpha OS, Linux
[ ] Proficient in computer languages: MatLab, Tex, LaTex, C, Basic, HTML
[ ] Proficient in computer programs: Adobe Illustrator, Word, Excel,
PowerPoint, PhotoEditor, Wordperfect
[ ] Excellent English grammar, review, and editing skills, 50wpm typing speed
[ ] Good French literacy (reading, writing, fair speaking)
In addition, I have knowledge in the operation of standard test equipment and hardware built by the following manufacturers: Hewlett-Packard (and Agilent), Fluke, Tektronix, IBM, any Intelsat-compliant satellite equipment manufacturer, any FCC type-accepted transmitter and receiver manufacturer, any ISO-9000 and ITU-compliant measurement, test, and analysis equipment manufacturer, Compaq (including former DEC systems), Sun, 3Com, Cisco, Intel, AMD, Microsoft, Linux.
8. Training, Certification, and Consulting ^
I teach (and have extensively taught for 25 years) industry engineers and scientists on behalf of the Time and Frequency Division on the details of frequency domain signal analysis. My training of students gives them a metrology certification necessary to ensure traceability of their measurements to NIST's time and frequency standards. This training and certification is broken down into 10 different subgroups around which I teach workshops and consult to industry and military. I am lead author with Dave Allan and Jim Barnes of the paper, entitled "Properties of Signal Sources and Measurement Methods." This document has been a classic referenced by members of the IEEE subcommittee on standards, the International Telecommunications Union, and other international governing committees which recommend publications for scientists interested in advanced, thorough treatments of time-series analysis as applied to communications and navigation systems involving oscillators and frequency standards.
1984 TO 1994: ^
In 1984, a recently installed chief of the Time and Frequency Division gave high priority to new, advanced systems of communicating the Division's extremely high clock accuracy to industrial, commercial, and military users. He assigned me to lead a program to improve, update and modernize NIST time dissemination services.
1. Advanced Time Dissemination Research using Geostationary Communications Satellites ^
Existing short wave radio stations (WWV in Fort Collins, CO, and WWVH in Kauai, HI), long wave station WWVB, and GOES satellite services were very popular but lacking in precision and accuracy. Because of my intimate knowledge of the physics of timekeeping and metrology, I was asked to start and lead two major project efforts: (1) build a time dissemination research test program to demonstrate and develop the best available precision and accuracy communications systems, and (2) develop a time broadcast service which equaled the performance of today's atomic clocks and which would continue into the next century.
My initialization of the R&D program represented the largest single
effort by the NIST Division in terms of dollars, with total expenditures of
over one million dollars in capital equipment alone. The new dissemination
technique, called TWSTT (for two-way satellite time transfer), uses
international and domestic stationary communications satellites in a global
network.
I have reported results of time transfer accuracy to the one nanosecond level and precision to 0.1 nanoseconds (or 100 picoseconds), 10,000 times better than the prevailing time transfer accuracy. One nanosecond is the time it takes light to travel only one foot, so the system can easily detect the smallest fluctuations thousands of miles away from the NIST Boulder Labs. My 1987 IEEE publication entitled "Progress toward One Nanosecond Two-Way Time Transfer Accuracy Using Ku-Band Geostationary Satellites" was reviewed prior to publication by the Director of the National Research Council Time Division of Canada. He acknowledged this paper with a glowing recommendation as the best definitive description of the future of time synchronization among laboratories participating in the generation of UTC. The paper still stands as among the best outlines of ultimate limits on precision and accuracy of TWSTT to industry and future network communications in terms of fundamental calibration limits.
2. Global Network Synchronization ^
I was assigned to develop a global time network in support of high-speed
data communications to connect laboratories engaged in scientific and military
experiments. This had the inherent requirement for the highest available timing
accuracy. The experiments include (1) navigation of deep-space probes for Jet Propulsion
Laboratories and NASA, (2) calibration and verification of the specifications
of the military's Global Positioning System, (3) coordination of primary
frequency standards in Japan, England, Austria, Germany, France, and the U.S.
(these are the locations of the principal standards of the free world), and (4)
high-precision tracking of position and velocity of orbiting communications
satellites. My program in TWSTT has created a large number of future R&D
opportunities in industry and government. Several programs are being proposed
which rely on recent TWSTT research. For my work, I received the Commerce
Department's highest achievement award in 1990, the Gold Medal, in a ceremony
in
3. Spread Spectrum Modem Design and Development ^
To meet the specialized needs of a global satellite time synchronization project, I and another co-worker specified, designed and developed a prototype spread-spectrum modem from 1989 to 1991. Particular features of the modem were (1) that a variety of code types and chip rates could be programmed, (2) that the signal structure allowed for the exchange through the satellite of its own recovered time-residual data, (3) that the signal would have sufficiently low power density to exist alongside other types of signals which shared the same satellite transponder, (4) that precision would be 200 ps (picoseconds) or better, and (5) that the cost would be significantly below other commercially available modems. The design was successfully demonstrated in 1992 and led to contract development and procurement of other modems for laboratory and military use.
1974 TO 1984: ^
I transferred to the Frequency and Time Standards group in 1974. The work in this group involves an advanced understanding of atomic physics and quantum electronics. In particular, work was with the NIST primary cesium (Cs) beam standards at that time, NBS-4 and NBS-6, and later with hydrogen maser development. This required a working knowledge in the field of atomic physics, specifically atomic beam spectroscopy. Additionally, I did research in oscillator phase noise measurements and spectral analysis. I have been engaged in a number of different programs as outlined below.
1. Error and Accuracy Analysis of
The standard of time interval is the "second." It is currently
defined by the frequency of a particular quantum energy transition in an
unperturbed cesium atom. In 1983, I was asked by NIST to complete an evaluation
of the reference clock, which is a highly specialized atomic spectrometer and
the source of
2. Frequency and Time Standards Research ^
I have experience and proficiency in many areas of physics. These
include:
[ ] Atomic and molecular spectroscopy
[ ] Atomic transitions, quantum energy states, and Lorentzian transitions and
line shape
[ ] Electron-oscillator model
[ ] Magnetic dipole, hexapole and optical state selection
[ ] Maser and laser theory
[ ] Saturated absorption
[ ] Magnetic field and gyromagnetic ratio measurements
[ ] Optical pumping
[ ] Polarization and induced dipole moments
[ ] Atomic resonance, radiative damping, and resonance Q
[ ] Lifetime and collision broadening and spin-exchange cross section
[ ] First- and second-order Doppler shifts, reduction and cancellation schemes
[ ] Doppler broadening, thermal atomic and molecular effects
[ ] Cavity design, cavity Q, cavity (reactive) frequency pulling, line pulling,
background pulling
[ ] Laser diodes
[ ] Atomic rate equations
[ ] Evaluation of coupling coefficients
[ ] Atomic and molecular beam velocity distributions, thermal equilibrium and
Boltzman derivation
[ ] Field inhomogeneity effects
[ ] Optical resonators
[ ] Waveguide and waveguide coupling theory
A. Hydrogen Maser Development ^
My work here was in the development of a new kind of precision frequency standard, a compact passive hydrogen maser. This development work represented an entirely new approach to maser technology and required a very broad background in both physics and electronics fundamentals. I and one other co-developer were fully responsible for this four-year effort. The purpose of this project was to develop hardware for potential use in the next generation of clocks in outer-space satellite probes, future military work related to the Milstar program, and civilian navigation needs, noteably the Global Positioning System. Furthermore, five hydrogen masers are combined to be the ''flywheel" oscillators in NIST's realization of UTC (universal coordinated time) since NIST's very accurate primary Cs frequency standard (F-1) cannot be run continuously as a clock and is not as stable as the hydrogen masers. For this work, I was awarded the distinguished Bronze Medal, which is the third highest award given in the Department of Commerce. It also led to a promotion.
Specific tasks that I performed during the hydrogen maser work are: 1. I designed and built a pure atomic hydrogen beam source using an RF plasma discharge of molecular (tank) hydrogen. The discharge is electrostatically induced on the inside of a Pyrex bulb. Atomic hydrogen is collimated through a hexapole state-selector magnet in which the lower magnetic dipole energy level in the ground state of the atom is focused into a microwave cavity.
2. I designed and built a new microwave cavity which is a high-Q TE011 mode type at the hydrogen magnetic transition frequency of 1.420 GHz. This cavity has a wall coating of low-loss alumina to reduce its size by dielectric loading of the electric component in the RF field.
3. I developed a new technique for applying a highly clean and inert wall coating of Teflon on the inside of the microwave cavity. The atomic wall interaction between the volume of hydrogen and the Teflon coating determines to a very large extent the quality factor of the maser. With my technique, I was able to reach the known best limit of performance of the atom-wall interaction. The breakthrough in understanding the Teflon wall coating technique is expected to affect a very wide variety of Teflon users.
4. I designed and built a multitude of peripheral aspects to the maser including temperature servo systems, vacuum hardware (in the 10-12 Torr region), large magnetic and electrostatic shields, HF to microwave multipliers, high resolution frequency synthesizers, and precision machining work of various kinds. B. Ammonia Utility Standard ^
From 1976 to 1978, I was responsible for the development of the electronic control system (commonly referred to as a frequency control servo system) for a portable frequency standard based on an ammonia vapor electric dipole resonance. Most cesium frequency standards are large, expensive, and weigh nearly 100 lbs with batteries. This device was to fill a need for an accuracy level of 10-9 and was designed to be small enough to be easily carried by an individual, to be low in cost (one-tenth the cost of cesium standards), to have quick start-up capability (within 15 seconds for full accuracy), and to be extremely rugged.
This work, sponsored by a U.S. Air Force R&D contract, when successfully completed, also produced several highly innovative outcomes. One of the most notable was my development of a high-stability internal reference oscillator having a miniature printed-circuit, high-Q, transmission line resonator (commonly referred to as a microstrip resonator). Quartz crystal oscillators are used most often, but their narrow tunability and shock sensitivity made them unsuitable as a reference in this ruggedized atomic standard. In the development of the microstrip oscillator, a breakthrough occurred in the fundamental understanding of the mechanism that controls the intrinsic stability of all oscillators. Prior theory held that a particular kind of noise process (instability) depended on resonator Q, or quality factor. This was proven false by data from my stripline design which showed that the prior noise process could be directly controlled by oscillator drive (which is limited in quartz oscillators) and active-device impurities. Specific noise processes were largely independent of Q.
A new kind of servo system was also developed out of the ammonia standards work. Rather than frequency-locking at a fundamental resonance rate, higher harmonics were also sampled and this greatly reduced errors in the accuracy of the lock. This work ultimately led to a promotion for me.
C. Atomic Beam Measurement System ^
I was assigned to design and build a complete system which would interface to a cesium beam tube and determine the distribution of atomic velocities in the beam. This determination is a crucial part of a complete evaluation which the beam tube must undergo in order to calculate the accuracy limit of the tube in a frequency standard configuration. The measurement of the velocity distribution is a complex task requiring the aid of a large number of probes and a computer if the measurement is to be done efficiently. Furthermore, the technique for this measurement had never been used prior to my work.
By 1975, a complete velocity distribution measurement system was assembled
under my supervision. I developed not only the hardware and interface aspects,
but also designed the software and operating system. The system was based on a
Data General frame computer with reel-to-reel 9-track
tape mass storage units, best available at the time. The development of this
system led to a novel digital servo system design for finding the exact center
frequency of the cesium atomic transition. The measurement of velocity
distribution was performed and documented on over 20 Cs tubes, all of which
were maintained at the NIST and U.S. Naval Observatory in
D. Digital Servo Techniques ^
Parallel with the cesium spectroscopy effort was the development of an entirely new digital servo system which allows a high resolution lock of an external oscillator to a particular atomic transition in a beam tube. Existing techniques suffer from offsets in the frequency lock which are very difficult to measure. My technique allows resolving line center to better than 1 x 10-13 at one second averaging in the case of the cesium atomic clock transition. Part of the new digital servo system has been used successfully on the new passive hydrogen standards program and in the locking of signals from lasers to other lasers. It has also been used for the NIST primary standards work, ammonia standards work, and in the velocity distribution measurement mentioned earlier.
3. Precision Power Spectrum, Phase-Noise, Electrical, and Time-interval Measurements ^
I have done extensive work related to making precise signal and noise
measurements, particularly phase-noise measurements, for signal carriers
ranging from below 1 Hz to 40 GHz. This work requires expertise in many
topics related to fundamental circuit design and electronic and eletromagnetic
theory and measurements. I am proficient in:
[ ] Network and circuits analysis, and equivalent
circuits
[ ] Pulse power measurements, pulse amplification, and pulse distribution
[ ] Filter design (Butterworth, Chebyshev, FIR and IIR, recursive,
constant-delay, multi-tap, etc.)
[ ] Scattering parameter estimation, Bode plots, Smith charts
[ ] Fast rise-time detection and related noise uncertainty analysis
[ ] Wideband analog-to-digital (ADC) and digital-to-analog (DAC) conversion
schemes
[ ] Dielectric coefficent measurements, dielectric loss, and loss tangent
[ ] Laplace and z transforms, Maxwell's equations
[ ] Windowing and sidelobe leakage suppression
[ ] Digital filter design and characterization
[ ] Time-frequency domain, and related convolution-multiplication and scaling
effects
[ ] Spectral aliasing
[ ] Frequency synthesis (using direct digital, PLL, multiplication-division,
programmable array logic, etc.)
[ ] Noise suppression (using cross-correlation spectral
analysis, negative feedback, synchronous lock-in methodologies, etc.)
[ ] Multiresolution signal decomposition and signal reconstruction
[ ] Design of all-pass equalizers, delay-line filters, and complex-conjugate
matched filters
[ ] Impedance transforms and reactance and resistance matching network design
[ ] Analysis and reduction of media phase and frequency dispersion, standing
waves, multipath, and transmission-line loss
[ ] Electrical-length measurements (for example, accurate phase and group
velocity estimation)
[ ] Uncertainty analysis of volt and resistance standards
[ ] Essentially all signal modulation schemes
[ ] Single and multi-mode optical fiber delay measurements
[ ] Directional couplers, bridge couplers, and circulators
1970 TO 1974: ^
My earliest work here involved many aspects of timekeeping, time generation,
and dissemination, while still completing college work at CU,
1. Time and Frequency Broadcast Research ^
My first studies were directed toward determining the precision with which timing information could be disseminated in the shortwave radio spectrum. This involved extensive wave analysis and signal and noise modeling.
Two sites containing transmitting and receiving equipment along with
precision clocks were located approximately 1000 miles apart; measurements were
taken during daylight on 13.56 MHz. My responsibilities involved designing and
building equipment specifically for these tests, operating the site near
As a result of the field studies, I undertook the task of implementing an
experimental format for WWV. This required extensive knowledge of the
capabilities of local frequency standards, the effects introduced by electronic
circuitry, the electromagnetic theory associated with given modes of
communications, and the variations due to external parameters unique to this
spectrum. I was responsible for the design and installation of modulation
equipment at the
The experimental format included modulation in the single-sideband mode and the design of special high-efficiency class D and class E rf high-power amplifiers. Since this mode had never before been used in these designs, the development of a modulator meeting demanding specifications and generating precise timing information became a fundamental aim of the project. My formal training in radio-physics and wave analysis, and my experience in solid-state electronics and communication and modulation theory were valuable in this effort.
This position required utmost speed and a need to proceed with little or no actual supervision much of the time. My contributions toward the group effort are evidenced by two facts: (1) that I was asked to continue to work until the very last possible moment before returning to college (and to be available in case of difficulty with ongoing experiment); (2) that I received a special cash award for my contribution.
2. High Power Radio Work at 20 kHz, 60 kHz, and 100 kHz VLF Mode ^
I co-developed a device which calibrates VLF tracking receivers using a 1
MHz frequency standard. WWVL and WWVB in
3. Television Time Distribution ^
This work dealt with the development of a new time dissemination method using coded information in the vertical retrace interval of the video scan of the standard television format. Primary duties involved researching methods of TV timing to get an optimum system. I was engaged in studying future needs of time users, exploring resources and methods of TV time dissemination, applying computer technology and logic design to a wide spectrum of timing problems within the framework of the television method (design solutions were largely a function of cost constraints and system requirements), working with contractors, lab assistants, and other research teams to coordinate activities, and lab and field testing of prototype timing equipment.
Because I had been involved in the television project since its inception, I possess a comprehensive background of such systems. The TV code generator and its companion receiver provide a method of communicating precise time and frequency information by utilizing line 21, a normally unused line in the vertical interval of the television format. Binary-coded-decimal (BCD) messages are transmitted which update receiver clocks and furnish alphanumeric communications; frequency data is transmitted via a 1 MHz coherent signal. The received code provided unambiguous time to 12 hours, with a resolution of 1 nanosecond and long-term stability of 10 nanoseconds for 10-second averaging. To achieve the best results, the complexity of design necessarily approaches even today's state-of-the-art computer technology.
The proposed NIST TvTime System was met with great acceptance by scientists interested in precise time and frequency synchronization. This interest led to a NIST-sponsored experiment of the active time and frequency code transmitted on the ABC television network, which encompassed nationwide coverage. This experiment presented an opportunity to (1) simulate as closely as possible the proposed layout necessary to accomplish widespread time distribution on a permanent basis; (2) allow evaluation by all interested laboratories with on-the-air signals; (3) determine any detrimental effects on the large population of home TV receivers; (4) more accurately define limitations imposed by typical network-to-affiliate programming (e.g., system would not work with video tape delays without the use of special equipment at the affiliate's studio); (5) research and optimize the design of all hardware aspects of the system; and (6) make pertinent time and frequency measurements and publish the results.
I was instrumental in the preparation of the equipment for the experiment. I, along with two other lab workers, built and aligned four complete time code generators and eleven high-resolution receiver-decoders. This was a major undertaking; each time code generator and decoder was a very complex instrument containing literally thousands of components, most packaged in integrated circuit "chips." The decoder designed was much like that of a terminal computer; it was comprised of data shift registers, major and minor divider chains, extensive control circuitry, video synchronizer, and 1-MHz and video phase-locked oscillators.
During this experiment, I traveled a great deal, installing precision
decoders throughout the continental
After three months of rigorous field study and laboratory analysis, using the best available instruments, I completed a comprehensive technical manuscript in which a large number of aspects of the system valuable to standards labs were documented. The TvTime study required in-depth knowledge of methods of measuring the spectral noise, statistical stability using the Allan variance, and phase vs. time of precision oscillators.
Because of the volume of work that I was able to complete during the nationwide television time and frequency experiment, I received a special award and cash bonus for my efforts.
4. Television Captioning System ^
The TvTime experiments proved the feasibility of communicating extra data via the standard television format, and interesting additional applications began to emerge, most notable the development of captioned television programming for the deaf. My responsibilities multiplied as our group undertook the task of applying our communications technique to a television captioning system.
I was instrumental in the design and development of a prototype time-frequency-caption
encoder which was used in the demonstration on
My work later was in the area of designing and building a prototype caption processor, which could read from magnetic tape, and a unique encoder/decoder unit which could allow captions to be imprinted on movies and films by means of a special FM subcarrier submerged in the audio track. I was again responsible for the complete documentation of circuits and equipment design related to these endeavors.
During the summer of 1972, our group was trying to gain TV industry approval
and FCC rulemaking in favor of TvTime and captions. I demonstrated our system
in the
The Public Broadcasting Service (PBS network) continued work on captioning
after NIST involvement ceased. The FCC approved rulemaking in 1976 principally
to allow captioning for the deaf. Currently, all the major networks offer
captioned television programs. On
5. Navigation Studies ^
Efforts to investigate new applications of the TvTime System generated opportunities in the areas of geodetic surveying and automatic vehicle location. The availability of powerful television signals in urban areas makes possible a technique of position determination and navigation by means of a precise time and frequency television code. Automatic Vehicle Monitoring (AVM) is a method whereby fleet vehicles are precisely located in real time and information reported to a central control station. Experiments were set up to measure the effectiveness of the TvTime System applied to AVM. Results were discussed in the paper, "The Feasibility of Applying the Active TvTime System to Automatic Vehicle Location."
During my employment with the time and frequency dissemination research team, I was involved in each and every project effort. My schooling in the field of radio physics provided a strong base for four years of close study and work at NIST in electromagnetic theory and its relationship to time-interval and frequency in rf field studies, multipath and propagation-delay effects, communications, navigation, standards, and precision metrology.
HOWE TECHNOLOGIES CORPORATION ^
I established Howe Technologies Corporation (HoweTech) in the fall of 1981
to provide consulting and maintenance services to radio and TV stations which
were upgrading to stereo audio from monaural audio. Prior to this, I
served as an on-air talent at FM radio stations in
Investors in the recording business were not interested in a radio and TV consulting or manufacturing effort which I started in 1977 which catered to owners of FM and TV stations who were upgrading their stereo audio production capabilities. Consequently, Mountain Ears was separately incorporated as a "spin-off" company with no continuing corporate ownership or affiliation with HoweTech. HoweTech was first established as a sole proprietorship and later incorporated in 1981.
1. Advanced Operator Console for Radio Stations ^
In 1977, I developed custom multichannel audio consoles designed specifically for on-air use in a 24-hour per day radio and television stations. At that time, the available manufactured consoles had outdated designs in spite of increased interest by radio stations (particularly FM and TV) for more advanced designs. The requirement for extreme reliability continued to exist but recording studio, sound reinforcement, and movie sound consoles were generally inadequately designed and unreliable for the task. Also, extraneous console facilities of "non-radio" consoles were expensive and too complicated for most on-air situations. My radio, audio and electronic expertise led to the development of six custom consoles which provided advanced performance while not sacrificing the total reliability necessary for broadcasting operations.
Design ideas were documented and console manufacturing was initiated. The
basic design permitted customizing by the radio station engineer, retained
excellent performance criteria, and allowed operation without fatigue by DJ's.
This console, which is titled the Series 7000, was introduced at the 1979
National Association of Broadcasters show in
One advantage of the Howe consoles is their ability to operate in a high RF (radio frequency) field with no sacrifice in performance. Many radio stations are co-located with transmitters and antennas. Audio equipment that is not designed to withstand a high concentration of RF simply does not perform adequately in this situation. Radio frequency interference (RFI) is virtually non-existent with all of my designs.
In addition to consoles, I also developed many console accessories, such as turntable preamps, power amplifiers, microphone mixers, telephone interconnects, etc.
2. Automatic Stereo Phase-Error Correction ^
A unique stand-alone piece of analysis, signal processing and real-time signal correction equipment that is receiving considerable praise for innovation in the broadcast industry is the Phase Chaser. This device continuously optimizes the phase relationship of two (left and right) stereo channels for noticeably clearer reception. It uses a proprietary cross-correlation technique, and the Phase Chaser represents a breakthrough for the broadcaster upgrading to digital stereo. Since its availability in January 1982, over 500 of these units have been delivered to major-market radio and TV facilities and commerical production studios. Development and manufacturing of the Phase Chaser elevated Howe Technologies to a leading-edge status. HoweTech holds the proprietary interest in its correlation technique and a patent issued in 1989. The advent of Dolby surround-sound widened the scope of usefulness of this device as evidenced by the large number of competing units which have now entered the market.
3. Responsibilities as Chief Executive Officer ^
As CEO for HoweTech, I wrote comprehensive business plans which led to two successful rounds of financing, in 1981 and 1984. These plans outlined all future goals, strategies, and organizational aspects needed to bring growth in revenues. My careful solicitations and interviews attracted two well-known venture capital companies that brought the initial capital infusion needed to implement the 1981 plan. Again in 1984, additional expansion needs led to a new growth plan which outlined new marketing opportunities, particularly in stereo TV. This brought in more financial support from the venture companies and an additional bank line of credit. Total working capital amounted to $500,000, outside of the company's own substantial holdings.
I brought to the company a very broad range of experience and know-how. I was the inventor of key concepts, methods, and products which brought Howe Technologies to a prominent position in the broadcast industry. As a consultant to broadcasting since 1970 and the founder of Howe Technologies in 1972, I gained a respected position in the industry independent of my full-time research position at NIST. In 1985, I left the company and an elected individual filled my CEO position in order for me to give priority to family, community activity, and expanding NIST research programs. In 1992, Howe Technologies ceased its design and manufacturing programs and returned to its original form as a radio and TV consulting and maintenance company.
During the growth of Howe Technologies, I obtained valuable skills in
responding to a market, interpreting audit results and other various financial
documents, procuring private equity funds, and managing people and other
resources to implement the business plans. This experience is rare in the
background of a research physicist, engineer, and mathematician and shows
clearly my ability to adapt to a variety of objectives with positive results.