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How Radiation and Near-Field Systems Really Work

2013 Texas Symposium on Wireless & Microwave Circuits & Systems
by

Hans Schantz

on 2 November 2014

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Transcript of How Radiation and Near-Field Systems Really Work

Heaviside, Oliver, Electromagnetic Theory, Vol. 3, London: “The Electrician” Printing and Publishing Company, Limited, 1912, p. 55.
Radiation as a transverse kink or bend in a field line.
Heaviside (1893) presented this model.
Radiation as “Kinked” Fields
Thompson, J. J., Energy and Matter, New York: Charles Scribner and Sons, 1904, p. 56.
Another early proponent was J.J. Thompson (1904)
Radiation as “Kinked” Fields
A charge accelerates due to an applied field.
The "kinked field line" picture is incomplete...
A complete picture looks something like this and includes an external applied field of finite extent.
No unphysical, unterminated field lines.
Accelerating Charge
Right-Hand Rule for Radiation
Time-Dependent Biot-Savart Law:
Hans Schantz, "Electromagnetic Radiation Made Simple," APS/AAPT Joint Meeting. Washington, D.C., April 18-21, 1997.
Energy
Energy
Energy
Energy
How Radiation and
Near-Field Systems
Really Work

Dr. Hans Schantz, CTO
Q-Track Corporation
Michael Faraday
Overview
Background
How Does Radiation Work?
How Do Radiation Fields Really Work?
How Does Radiation Energy Work in Dipoles?
Application - Near-Field Wireless
Brief History of Electromagnetics
Faraday and "Field Theory"
Maxwell and Electromagnetic Theory
Hertz and Radio Waves
Heaviside and "Maxwell's Equations
J.J. Thompson and the Electron
"...I cannot refrain from again expressing my conviction of the truthfulness of the representation, which the idea of lines of force affords in regard to magnetic action. All the points which are experimentally established with regard to that action, i.e. all that is not hypothetical, appear to be well and truly represented by it."
Experimental Researches in Electricity, Vol. III, § 3234 (New York: Dover Publications, Inc., 1965) p. 397. Originally published 1855.
Field Theory
Prevailing theory: action-at-a-distance
Faraday interpreted filing patterns as implying fields pervading space
Guided by this insight, Faraday discovered induction.
Royal Institution
March 12, 1832

Certain of the results of the investigations which are embodied in the two papers entitled ‘Experimental Researches in Electricity’ lately read to the Royal Society, and the views arising therefrom, in connexion with other views and experiments lead me to believe that magnetic action is progressive, and requires time, i.e. that when a magnet acts upon a distant magnet or piece of iron, the influencing cause (which I may for the moment call magnetism) proceeds gradually from the magnetic bodies, and requires time for its transmission, which will probably be found to be very sensible.

I think also, that I see reason for supposing that electric induction (of tension) is also performed in a similar progressive way.

I am inclined to compare the diffusion of magnetic forces from a magnetic pole to the vibrations upon the surface of disturbed water, or those of air in the phenomenon of sound; i.e. I am inclined to think the vibratory theory will apply to these phenomena as it does to sound, and most probably to light.

By analogy, I think it may possibly apply to the phenomenon of induction of electricity of tension also.

These views I wish to work out experimentally; but as much of my time is engaged in the duties of my office, and as the experiments will therefore be prolonged, and may in their course be subject to the observation of others, I wish, by depositing this paper in the care of the Royal Society, to take possession as it were of a certain date; and so have right, if they are confirmed by experiment, to claim credit for the views at that date; at which time as far as I know, no one is conscious of or can claim them but myself.

M. Faraday
James Clerk
Maxwell
A Dynamical Theory of the Electromagnetic Field, §74 (Edinburgh: Scottish Academic Press, 1982), p. 70. Originally published as "A Dynamical Theory of the Electromagnetic Field", Philosophical Transactions of the Royal Society of London CLV (1865).
"In speaking of the Energy of the field, however, I wish to be understood literally. All energy is the same as mechanical energy, whether it exists in the form of motion or in that of elasticity, or in any other form. The energy in electromagnetic phenomena is mechanical energy. The only question is, Where does it reside? On the old theories it resides in the electrified bodies, conducting circuits, and magnets, in the form of an unknown quantity called potential energy, or the power of producing certain effects at a distance. On our theory it resides in the electromagnetic field, in the space surrounding the electrified and magnetic bodies, as well as in those bodies themselves...."
Heinrich Hertz
"The preponderance of such [action-at-a-distance] forces in theory has long been sanctioned by science, but has always been accepted with reluctance by common sense; in the domain of electricity these forces now appeared to be dethroned from their position by simple and striking experiments." Electric Waves, (New York: Macmillan and Co., 1893), p. 18.
Field Theory
Maxwell "translated what [he] considered to be Faraday's ideas into mathematical form...." A Treatise on Electricity and Magnetism, p. xi
Related speed of light to permitivity and permeability.
Predicted electromagnetic nature of light.
See: http://www.aetherczar.com/?p=3044
How Does Radiation Work?
Electric and Magnetic Ripples?
The "Kinked Field" Model
But is the Kinked Field Model Correct?
Faraday
Predicted radiation in secret 1832 letter
Letter not opened and read until 1937
"Magnetic action is progressive and requires time..."
"I am inclined to compare the diffusion of magnetic forces from a magnetic pole to the vibrations upon the surface of disturbed water...
Oliver Heaviside
Hertz Discovers Radio Waves
Used Leyden Jars to generate sparks at terminals of resonant antennas.

Used a loop antenna with adjustable gap as a detector.
Established standing waves.

Determined that radio waves propagate at the speed of light.
Background
"...Faraday, in his minds eye, saw lines of force traversing all space where the mathematicians saw centers of force attracting at a distance. Faraday saw a medium where they saw nothing but distance. Faraday sought the seat of the phenomena in real actions going on in the medium, they were satisfied they had found it in a power of action at a distance impressed on the electrical forces."
Treatise on Electricity and Magnetism, Preface to the First Edition, p. xi.
"I have succeeded in producing distinct rays of electric force, and in carrying out with them the elementary experiments which are commonly performed with light and radiant heat." Electric Waves, (New York: Macmillan and Co., 1893), p. 172.
Heaviside Form of Maxwell's Equations
"In the sense of our theory we more correctly represent the phenomena by saying that fundamentally the waves which are being developed do no owe their formation solely to processes at the origin, but arise out of the conditions of the whole surrounding space, which latter, according to our theory, is the true seat of the energy." Electric Waves, (New York: Macmillan and Co., 1893), p. 146.
“However mysterious energy (and its flux) may be in some of its theoretical aspects, there must be something in it, because it is convertible into dollars, the ultimate official measure of value.” Electromagnetic Theory Vol. 1, p. 381
Dipole Fields
Hertz plotted dipole fields in detail.
Electric Waves, p. 144.
"When I had translated what I considered to be Faraday's ideas into a mathematical form, I found that in general the results of the two methods coincided, so that the same phenomena were accounted for, and the same laws of action deduced by both methods..."
Treatise on Electricity and Magnetism, Preface to the First Edition, p. ix.
What is Maxwell's theory? .... Speaking for myself, it was only by changing its form of presentation that I was able to see it clearly, and so as to avoid the inconsistencies. Electromagnetic Theory, Vol. 1 1893, pp. vi-vii.
J.J. Thompson
Thomson Discovers Electron
Studied Cathode Rays
Measured charge/mass ratio
Identified "electron" as primary charge carrier
"As the cathode rays carry a charge of negative electricity, are deflected by an electrostatic force as if they were negatively electrified, and are acted on by a magnetic force in just the way in which this force would act on a negatively electrified body moving along the path of these rays, I can see no escape from the conclusion that they are charges of negative electricity carried by particles of matter."
Phil. Mag. 44, 1897, p. 293
"...a moving electrified particle radiates energy whenever its velocity is changing either in magnitude or direction. "
Electricity and Matter, 1904,
p. 105.
Radiation as "Kinked" Fields
Radiation is a transverse component in a changing field line - a "kink."
Original Field Line
Time
Radiation = Transverse Field Line
Change Propagates at
Speed of Light
Radiation Isn't "Kinky"
Infinite, unterminated field lines are unphysical
Violates Conservation of Energy - from where does the charge get the energy to radiate?

So How Do Radiation Fields Really Work?
Gauss' Law
Basics of Fields
What's Missing from the "Kinked Field" Model?
The usual “radiation field” approximation…



…violates Gauss’s Law
Gauss's Law: Radiation
Are there sinks or sources associated with radiation?
What About Radiation?
Suppose we add another term…


…then Gauss’s Law (source free region) is satisfied:
Gauss' Law for Radiation
A radial component is needed to close the loop:


Bound field lines have:
Source (positive charge)
Sink (negative charge)
Unbound or radiation field lines are closed field lines (neither source nor sink).
Take a closer look at the "kinked field line" model...
Radiation is Divergenceless
A simple calculation in the co-moving (i.e. v = 0) reference frame.
The fields are (for the charge): (for the applied field):


From the equation of motion:
The tangential field is:

…which goes to zero for:
Energy Localization: Accelerating Charge
Since Sr = E H, no energy passes through this sphere around the charge

Interesting implications:
No energy can pass
through this surface
EM analog to an event horizon
Energy Localization: Accelerating Charge
Exponential Decay
Radiation is a decoupling of field lines from a source
How Does Energy Decouple from Harmonic Dipoles?
No energy escapes without being temporarily stored
Dipole “emits” only half the time
Average radiation distance 0.173lambda
EH-Phase Delta
H-Phase
E-Phase
H. Schantz, “Near-Field Phase Behavior,” 2005 IEEE Antennas and Propagation Society International Symposium, Washington, DC, USA, Vol. 3B, 3-8 July, 2005, pp. 134-137. See: http://bit.ly/edzH82
H. Schantz, “A Real-Time Location System Using Near-Field Electromagnetic Ranging,” 2007 IEEE Antennas and Propagation Society International Symposium, Honolulu, HI, USA, 9-15 June, 2007, pp. 3792-3795. http://bit.ly/uo1feI
H. Schantz and R. DePierre, “System and method for near-field electromagnetic ranging,” U.S. Patent 6,963,301, 8 Nov., 2005. See: http://bit.ly/AlEExY
E-Field Phase Superluminal
H-Field Phase Antichronous
Confounds Time-of-Flight
Phase Delta:
Near-Field Velocity: Phase
H. Hertz, Electric Waves, (London: Macmillan and Co., 1893), p. 152. See http://bit.ly/vJroXs
Charles Capps, “Near Field or Far Field,” EDN, August 16, 2001, pp. 95-102. See: http://bit.ly/tknV2z
Far Field:

Diverges in Near-Field Zone

Near-Field Impedance
Harald T. Friis (1893-1976)
Harald Friis, “A note on a simplified propagation formula,” Proc. IRE, 34, May 1946, pp. 254-256.
Photo of Harald Friis by permission of Mt. Holyoke College Archives
Friis’ Law – Far Field
Far-Field Propagation
H. Schantz, “A Near Field Propagation Law Vol. 3A, 3-8 July 2005, Pages: 237 - 240. See: http://bit.ly/tDB9eq
“Like” Antennas


“Unlike” Antennas
Near Field Propagation
H. Schantz, et al, “Characterization of Error in a NFER Real-Time Location System,” 2011 IEEE Radio and Wireless Symposium, 16-20 Jan. 2011. See: http://bit.ly/mtJNpZ
Office/Lab Environment 16m x 36m
Five Receivers; ~15m Spacing
Evaluate accuracy at 82 Locations
Total 410 Data Points
Average Error 55cm; w/in 1m 80%
NFER RTLS Accuracy
Gauss' Law
In 1835, Gauss found that the electric flux through any closed surface is proportional to the enclosed electric charge.
Corollary - electric field lines begin and end on charges

Magnetic field lines are "divergenceless," i.e. a closed loop with no beginning and no end.
-
+
Is this a complete picture?
A charge does not accelerate of its own volition.
For an electron, re = 2.8E-15 m is the “classical electron radius”
Understanding Radiation Energy
Accelerating charges are not the direct source of radiation energy.
Radiation fields trigger the release of energy from fringing zone of an applied field.
Can understand the origins of radiation energy by looking for surfaces through which there is no energy flow (radial Poynting vector goes to zero)
How Does Radiation Energy Work for Dipoles?
Exponential Decay
Harmonic Dipole
For an exponentially decaying dipole,
for:
so:

Inside: energy flows in
to be dissipated in decay.
Outside: energy radiates
away.
Radiation energy comes
from energy stored in the
static fields - not from the region around the accelerating charges themselves.
Space-Time Energy Flow for Harmonic Dipoles
E-Field Phase
H-Field Phase
Phase Delta
Near-Field Phase Relations
Applications
Near-Field Links
Near-Field Electromagnetic Ranging
Q-XL™
Q-Dose™
Tag
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Integrators: IIS, Digitnexus, RSCS
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Placed on Cranes & Forklifts
Order for Five Systems Pending
QT™-600
TX Tag
QT™-550
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Receiver
Non-Line-of-Sight Collision Avoidance
Proximity Detection
Many Parameters – High Accuracy
Summary
Background
How Does Radiation Work?
How Do Radiation Fields Really Work?
How Does Radiation Energy Work in Dipoles?
Application - Near-Field Wireless
Questions? More Information?
See: Art and Science of UWB Antennas
Q-Track Website: http://www.q-track.com
E-Mail: h.schantz@q-track.com
http://prezi.com/otni2uxyxo4_/how-radiation-and-near-field-systems-really-work/
Energy Flow and Accelerating Charges
Increasing velocity: increasing kinetic energy
Increasing current: increasing magnetic energy
Accelerating charges absorb energy
Applied field supplies radiation energy
H. Schantz, "On the Localization of Electromagnetic Energy," Ultrawideband-Short Pulse Electromagnetics 5, 2002, pp. 89-96.
H. Schantz, "Electromagnetic Energy Around Hertzian Dipoles," IEEE Antennas and Propagation Magazine, Vol 43, No. 2, April 2001.
Full transcript