| IEEE Transactions on Information Theory, Vol. IT-14, No. 3, May 1968 |
| A Generalized Concept of Frequency and Some Applications |
| Henning F. Harmuth |
| The system of sine and cosine functions has been distinguished historically in communications. Whenever the term frequency is used, reference is made implicitly to these functions; hence the generally used theory of communication is based on the system of sine and cosine functions. In recent years other complete systems of orthogonal functions have been used for theoretical investigations as well as for equipment design. Analogs to Fourier series, Fourier transform, frequency, power spectra, and amplitude, phase, and frequency modulation exist for many systems of orthogonal functions. This implies that theories of communication can be worked out on the basis of these systems. Most of these theories are of academic interest only. However, for the complete system of the orthogonal Walsh functions, the implementation of circuits by modern semiconductor techniques appears to be competitive in a number of applications with the implementation of circuits for the system of sine and cosine functions. 7 pages. |
IEEE Spectrum, November 1969 |
| Application of Walsh Functions in Communications |
| Henning F. Harmuth |
| Communication theory was founded on the system of sine-cosine functions. A more general theory has become known more recently; it replaces the sine-cosine functions by other systems of orthogonal functions, and the concept of frequency by that of sequency. Of these systems, the Walsh functions are of great practical interest since they lead to equipment that is easily implemented by semiconductor technology. Filters, multiplexing equipment, and a voice analyzer/synthesizer have been built successfully for Walsh functions. Some interesting applications of electromagnetic Walsh waves have been found theoretically. 10 pages. |
|
Transmission of Information by Orthogonal Functions, Second Edition, Springer Verlag, 1972 |
| Historical Background and Motivation for the Use of Nonsinusoidal Functions |
| Henning F. Harmuth |
| Introduction, with sub-sections including 1) Historical Background and Motivation for the Use of Nonsinusoidal Functions, 2) Orthogonal Functions, Walsh Functions and Other Basic Mathematical Concepts, 3) Filtering of Time and Space Signals, 4) Direct and Carrier Transmission of Signals, 5) Nonsinusoidal Electromagnetic Waves, 6) Statistical Theory of Communication. 9 pages |
|
Transmission of Information by Orthogonal Functions, Second Edition, Springer Verlag, 1972 |
| Signal Selection and Synchronization |
| Henning F. Harmuth |
| A chapter fragment, including "Separation of Signals in Mobile Communication" and "Synchronous Reception of Walsh Waves". This is a very early description of the correlation detection of ultra-wideband signals. 9 pages. |
|
Second Symposium and Technical Exhibition on Electromagnetic Compatibility, Montreux, June 28-30, 1977 |
| Interference Caused by Additional Radio Channels Using Nonsinusoidal Carriers |
| Henning F. Harmuth |
| The first radio transmitters and receivers using nonsinusoidal carriers have been built during the last few years. Most advanced is the into-the-ground radar by Chapman, which has become commercially available for construction surveys. Many other good applications for nonsinusoidal waves are known, primarily in radar but also for special types of communications. These waves share the spectrum with the existing radio services that have been traditionally separated by the use of different frequency bands. Two questions arise from the standpoint of frequency management: 1. Can we provide additional radio channels by the use of nonsinusoidal carriers? 2. How will such carriers affect existing radio services? The answer to the first question is that it is indeed possible to add channels to the existing ones, and not merely replace radio channels based on sinusoidal carriers. The existing radio services will be affected, in first approximation, as if the natural background noise had increased. 6 pages. |
|
Report to the Air Force Office of Scientific Research, December, 1974 (Table of Contents, Introduction, Summary only) |
| Radiation of Electromagnetic Walsh Waves |
| S.C. Fralick et al |
| From the introduction—Sinusoidal functions have not always held a preeminent position in the synthesis and analysis of electromagnetic systems. Historically, the first radiation of electromagnetic energy was accomplished with pulses, not sinusoids. The development of the practical capacitor, the relatively high cost of active switching elements, and the resulting emphasis on linear, time-invariant system theory have been the chief reasons for the present preponderant use of sines and cosines. Semiconductor technology has changed the economics of system design and implementation. Today an active switch costs less than a capacitor and uses less space. Often it is less expensive to use several transistors than one resistor when a medium- or large-scale integrated circuit is designed. 12 pages. |
|
Sequency Theory—Foundation and Applications, Academic Press, Inc., 1977 |
| The Dogma of the Circle |
| Henning F. Harmuth |
| Introduction, with sub-sections including 1) The Dogma of the Circle, 2) The Circle and the Circular Functions and Communications, 3)Basic Mathematical Concepts, 4)Time and Space Signals, 5) Optical Images from Acoustic Waves, 6) Electromagnetic Waves with General Time Variation, 7) Concepts of Communications Applied to Physics 8) A Guide to Reading. 17 pages. |
|
Sequency Theory—Foundation and Applications, Academic Press, Inc., 1977 |
| Frequently Raised Objections |
| Henning F. Harmuth |
| A chapter fragment answering objections to nonsinusoidal waves, along with links to referenced figures. From the description: Experience has shown that certain objections against nonsinusoidal waves and sampled sensor arrays are raised over and over again. Twenty-five frequently made objections are listed here together with short answers. It was felt that the use of hypothetical objections constructed by the author would not have been fair, and that authentic objections by scientists of recognized standing should be used. A perfect source for this purpose are the reviewers of scientific journals with worldwide reputation. 8 pages, plus figures. |
|
IEEE Transactions on Electromagnetic Compatibility, Vol. EMC-19, No. 3, August 1977 |
| Selective Reception of Periodic Electromagnetic Waves with General Time Variation |
| Henning F. Harmuth |
| Several transmitters and receivers for periodic nonsinusoidal electromagnetic waves have been built during the last few years. Various applications of such waves, primarily in radar, have been recognized. The first practical equipment, an into-the-ground radar for construction surveying, has become commercially available. The efficient radiation of nonsinusoidal periodic waves has been discussed in the literature, but very little has been published on their selective reception. This paper describes the principle of selective receivers for periodic waves with general time variation, in analogy to the design of the usual receivers for waves with sinusoidal time variation. 8 pages. |
|
IEEE Transactions on Electromagnetic Compatibility, Vol. EMC-20, No. 1, February 1978 |
| Frequency-Sharing and Spread-Spectrum Transmission with Large Relative Bandwidth |
| Henning F. Harmuth |
| Radio transmission has been based traditionally on the concept of a small relative frequency bandwidth, which permits the use of circuits and structures that resonate with sinusoidal functions. This approach created no problems until high-resolution radar advanced to pulse durations in the order of 1 ns, and spread-spectrum transmission to frequency bands in the order of 100 MHz. The use of a small relative frequency bandwidth requires in these cases operation at frequencies above 10 GHz. Absorption by rain and fog as well as the high noise temperature, make these high frequencies less desirable. Furthermore, the lower frequency bands cannot be used, even though they are there and their absolute bandwidth is perfectly sufficient; only the unnecessary requirement of a small relative bandwidth prevents their use. concepts and equipment that allow operation with a large relative bandwidth make it possible to operate radar with a resolution up to 0.1 ns in the most desirable range from a few hundred megahertz to about 10GHz; spread-spectrum transmission can operate without regard to the relative frequency bandwidth. This paper explains primarily the motivation for the development of equipment handling large relative bandwidths, since the equipment itself has already been discussed in the literature and is available on an advanced experimental level. 8 pages. |
|
Proceedings of the IEEE, Vol. 66, No. 3, March 1978 (Invited Paper) |
| Time-Domain Electromagnetics and Its Applications |
| C. Leonard Bennett and Gerald F. Ross |
| (Partial Abstract) The purpose of this paper is to introduce the reader to the elements of time- domain electromagnetics, which includes baseband-pulse technology and target-signature analysis. Baseband pulses are video or carrierless pulses of very short duration, whose spectral content is concentrated primarily from zero frequency through the microwave region of the spectrum. Work in baseband technology began more than ten years ago at the Sperry Research Center with emphasis primarily on its use as an analytical tool, initially to explore the properties of microwave networks. 20 pages |
|
roceedings of the IEEE, Vol. 67, No. 6, June 1979 |
| Some Physical Constraints on the Use of "Carrier-Free" Waveforms in Radio-Wave Transmission Systems |
| John R. Davis, Dennis J. Baker, J. Paul Shelton, and William S. Ament |
| (Naval Research Laboratory, Washington DC) |
| Are there practical applications in radio-wave transmission of inherently broad-band "carrier-free" waveforms such as Walsh functions? We demonstrate in this paper that the band-limiting constraints of radiating systems limit emission of the low-frequency spectral components of such waveforms and severely restrict the radiation directivity that may be achieved in systems that employ them. We also find that dispersion in the propagating medium poses difficulties for the use of such waveforms, and we present an example that illustrates their impracticality in a case in which medium-related limits on coherence bandwidth are of concern. Considerations of capital cost, reliability, and maintenance militate against the use of these waveforms and in favor of conventional spread-spectrum modulation schemes where such service is required. Troublesome aspects of engineering analysis methods for systems employing such modulation schemes are also exposed, as are some practical and economic difficulties to be expected if they are to be introduced as co-users of the electromagnetic spectrum with conventional radio systems. 8 pages. |
|
Nonsinusoidal Waves for Radar and Radio Communication, Academic Press, Inc., 1981 |
| Origins and Use of Nonsinusoidal Waves in Radar and Radio Communication |
| Henning F. Harmuth |
| Introduction, with sub-sections including 1) The Origins of Sinusoidal Waves in Radio Transmission, 2) Lumped, Time-Variant Resonant Circuits, 3) Distributed, Time-Variant Resonant Circuits, 4)Relative Bandwidth, 5) Attenuation of Waves, Noise, and Distortions, 6) When to Use Nonsinusoidal Waves. 17 pages. |
|
IEEE Transactions on Electromagnetic Compatibility, Vol. EMC-25, No. 1, February 1983 |
| Antennas for Nonsinusoidal Waves: I. Radiators |
| Henning F. Harmuth and Shao Ding-Rong |
| During the last few years numerous applications of nonsinusoidal electromagnetic waves have been discussed in this journal. It is generally accepted that the antennas pose the greatest difficulty. In a series of papers on radiators, sensors, and arrays, we will investigate antennas, both theoretically and experimentally. Sufficient information is provided to permit anybody who is equipped for work with pulses of about 1-ns duration to build simple radiators and sensors. 12 pages. |
|
IEEE Transactions on Electromagnetic Compatibility, Vol. EMC-26, No. 1, February 1984 |
| Comment on "Antennas for Nonsinusoidal Waves: I. Radiators" |
| Juan A Morente and Rafael Gomez |
| Letter to the editor. 1 page |
|
IEEE Transactions on Electromagnetic Compatibility, Vol. EMC-25, No. 2, May 1983 |
| Antennas for Nonsinusoidal Waves: II. Sensors |
| Henning F. Harmuth and Shao Ding-Rong |
| The use of the basic large-current radiator¾discussed in a previous paper¾and the Hertzian electric dipole as sensor is investigated. If the sensor works into a large resistive load, typically implemented by an emitter follower, its output voltage varies like the electric field strength, while a capacitive load produces an output voltage proportionate to the integral of the field strength. The maximum energy is transferred to a load impedance that is equal to the radiation resistance of the antenna. This is the same result as in the case of sinusoidal waves, but the radiation resistance for nonsinusoidal waves differs from that for sinusoidal waves. An effective aperture can be defined, which is again analogous, but not equal, to the same concept used for sinusoidal waves. 9 pages. |
|
IEEE International Symposium on Electromagnetic Compatibility, 1983 |
| Large-Current, Short-Length Radiator for Nonsinusoidal Waves |
| Henning F. Harmuth and Shao Ding-Rong |
|
Antennas and Waveguides for Nonsinusoidal Waves, Academic Press, Inc., 1984 |
| Introduction to Antennas and Waveguides for Nonsinusoidal Waves |
| Henning F. Harmuth |
| Introduction with sub-sections 1) Basic Concepts, 2) Transmitter and Receiver, 3) Nonsinusoidal Spread Spectrum Radio Transmission, 4)Pulse Agility Versus Frequency Agility, 5) Limits on the Use of Fourier Analysis, 6) Absorbers, 7) Reflection of Short Pulses by a Layered Medium, 8) Impedance Matching for Electromagnetic Waves, 9) Matching Absorption and Impedance, 10) Absorption of Radio Signals with Large and Small Relative Bandwidth. 43 pages. |
|
IEEE Aerospace and Electronic Systems Magazine, November 1990 |
| Report: Assessment of Ultra-Wideband (UWB) Technology |
| Charles Fowler, John Entzminger, and James Corum |
| Summary Report of the DARPA/OSD Ultra-Wideband Radar Review Panel (convened by Battelle) to examine the state-of-the-art, benefits, and limitations of UWB Technology, with particular emphasis on radar applications. 5 pages. |
|
Ultra-Wideband Radar—Proceedings from the First Los Alamos Symposium, 1991 |
| Energy Transfer & Propagation and the Dielectrics of Materials: Transient versus Steady State Effects |
| Terence W. Barrett |
| This paper examines the consequences of the effects of inertia in the medium on transferring energy by ultrafast pulses or wavepackets which are also ultrawideband. Envelope effects such as Sommerfeld and Brilloin precursors are examined. The theoretical and experimental evidence for precursor effects are presented and discussed as well as the linear classical area theorem and the nonlinear McCall-Hahn area theorem for self-induced transparency. Definitions of the velocity of ultrafast packet propagation through various media are described. The importance of causality conditions and the Cauchy initial and final conditions in describing nonstationary and envelope effects is stressed and the limitations and appropriateness of the global Fourier analysis steady state technique are examined. 19 pages. |
|
IEEE AES Systems Magazine, March 1992 |
| Ultra Wideband Signals¾ ¾A New Step in Radar Development |
| Lev V. Astanin and Alexander A. Kostylev |
| The utilization of UWB signals enables us to solve at quite new qualitative levels the most important problems of radar target observation: the measurement of coordinates and their derivatives, discrimination and radar imaging, and the measurement of radar target characteristics. The survey of the description methods of UWB radar design including details of peculiarities of radiation, scattering, reception of signals and digital processing techniques is presented. 4 pages. |
|
Invited Paper, MILCOM ’93 Conference |
| Multiple Access with Time-Hopping Impulse Modulation |
| R.A. Scholtz |
| A time-hopping modulation format employing impulse signal technology has several features which may make it attractive for multiple-acess communications. These features are outlined, an estimate of the multiple-access capability of a communication system employing this format under ideal propagation conditions is presented, and emerging design issues are described. 5 pages. |
|
Chapter One, Introduction to Ultra-Wideband Radar Systems, edited by James D. Taylor, |
| CRC Press, 1995 |
| Ultra-Wideband Radar Overview |
| James D. Taylor |
| Discussion of the book’s contents, including UWB Radar Terminology and Concepts, Potential Applications of UWB Radar, and UWB Systems Frequency Spectrum Sharing and Interference Issues. 10 pages. |
|
Chapter One, Introduction to Ultra-Wideband Radar Systems, edited by James D. Taylor, |
| CRC Press, 1995 |
| Technical Issues in Ultra-Wideband Radar Systems |
| Harold F. Engler, Jr. |
| Long chapter discussing Fundamental Radar Principles, Classification of Radar Waveforms, Design Issues, Signal Characteristics Governing Range and Velocity Measurement Resolution, Range Accuracy Requirements for Velocity Estimation from Differential Time Delay, and the Concept of Nonlinearity. 40 pages. |
| .
Association for Unmanned Vehicle Systems International 1997 Conference (AUVSI'97), |
| Baltimore, June 3-6, 1997 |
| An Ultra Wideband Communication Link for Unmanned Vehicle Applications |
| Robert J. Fontana, J. Fred Larrick, and Jeffrey E. Cade |
| Covert communications links are highly desirable for unmanned vehicle applications in which the presence, and hence location, of the vehicle must not be compromised by the long range detection of electromagnetic emissions radiated from the platform. In addition, an anti-jam (AJ) command and control uplink is critical to the survivability of unmanned aerial vehicles in either hostile or high electromagnetic interference (EMI) environments. Ultra wideband (UWB) technology, well-known for its ground penetrating radar applications, has been demonstrated to possess both low probability of intercept and detection (LPI/D) as well as AJ features when properly deployed in a communications system design. Such waveforms provide a unique form of spread spectrum communications utilizing extremely short duration pulses (typically 1-2 nanoseconds) and low average power levels (typically only a few microwatts). UWB systems are also characterized by their low cost, all-digital design, small size, and light weight, making them ideally suited to unmanned vehicle applications. 6 pages. |
|
Invited Paper, IEEE PIMRC ’97, Helsinki |
| Impulse Radio |
| Robert.A. Scholtz and Moe Z Win |
| Impulse radio, a form of ultra-wideband signaling, has properties that make it a viable candidate for short range communications in dense multipath environments. This paper describes the characteristics of impulse radio, gives analytical estimates of its multiple access capability, and presents propagation test results and their implications for the design of the radio receiver. 23 pages. |
|
IEEE Communications Letters, Vol. 2, No. 1, January 1998 |
| Impulse Radio: How It Works |
| Moe Z Win and Robert.A. Scholtz |
| Impulse radio, a form of ultra-wide bandwidth (UWB) spread-spectrum signaling, has properties that make it a viable candidate for short range communications in dense multipath environments. This letter describes the characteristics of impulse radio using a modulation format that can be supported by currently available impulse signal technology and gives analytical estimates of its multiple access capability under ideal multiple access channel conditions. 3 pages. |
|
An Ultra Wideband Synthetic Vision Sensor for Airborne Wire Detection |
| R.J. Fontana, J.F. Larrick, J.E. Cade, and E.P. Rivers, Jr. |
| A low cost, miniature ultra wideband (UWB) radar has demonstrated the ability to detect suspended wires and other small obstacles at distances exceeding several hundred feet using an average output power of less than 10 microwatts. Originally developed as a high precision UWB radar altimeter for the Navy’s Program Executive Office for Unmanned Aerial Vehicles and Cruise Missiles, an improved sensitivity version was recently developed for the Naval Surface Warfare Center (NSWC Dahlgren Division) as part of the Marine Corps Warfighting Laboratory’s Hummingbird program for rotary wing platforms. Utilizing a short pulse waveform of approximately 2.5 nanoseconds in duration, the receiver processor exploits the leading edge of the radar return pulse to achieve range resolutions of less than one foot. The resultant 400 MHz bandwidth spectrum produces both a broad frequency excitation for enhanced detection, as well as a low probability of intercept and detection signature for covert applications. 9 pages. |