Note: Descriptions are shown in the official language in which they were submitted.
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B~CKGROUND OF THE INVENTION
1 Field of the Invention
This invention relates generally ~o the transfer of information by
means of an electromagnetic field, and more particularly to the transfer
of information by a component of the magnetic vector potential field.
2. Description _ the Prior Art
It is known in the prior art to provide systems for the transfer of
information utilizing electromagne~ic fields which are solutions to
Maxwell's equations. I These information transfer systems include
apparatus for generating modulated electr~magnetic fields ana apparatus
~or detecting and demodulating the generated electromagnetic fields.
~xamples of the prior type information transfer systems include radio
ana television band-based systems, microwave band-based systems and
optical band-based systems.
The Maxwell equations, which govern the prior art transfer of
information by electromagnetic fields can be written:
1. CURL E t~ ~ - O
2. CURL H
3. DIV B ~~
4. DIV D = ~
where E is the electric ~ield density, H is the magne~ic field
intensity, B is the magnetic flux density, D is the electric displace-
ment, J is the current density and f is the change density. In this
notation, the bar over a quantity indicates that this is a vector
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quantity, i.e., a quantity for which a spatial orientation is required for com-
plete specification. The terms CURL and DIV refer to the CURL and DIVERGENCE
mathematical operations*. The magnetic field intensity and the magnetic flux den-
sity are related by the equations B ~ H, while the electric field density and the
electric displacement are related by the equation ~ E. These equations can be
used to describe the transmission of electromagnetic radiation through a vacuum or
through various media.
It is known in the prior art that solutions to Maxwell's equations can
be obtained through the use of electric scalar potential functions and magnetic
vector potential functions. The electric scalar potential is given by the expres-
sion:
5. 0~ O ~ ~ d~
where 0~1) is the scalar potential at point 1, p~2) is the charge density at point
2, Y12 is the distance between point 1 and 2, and the integral is taken over all
differential volumes. The magnetic vector potential is given by the expression
6, A ~ ~ C ~ ~ a cl ~r ~l~
where A~l) is the vector potential at point 1, is the permittivity of free
space, C is the velocity of light, J~2) is the ~vector) current density at point
2, rl2 is the distance between point 1 and point 2 and the integral is taken over
all differential volumes dv~2). The potential functions are related to Maxwell's
equations in the following manner.
7. E -GRAD0- ~A
where GRAD is the gradient mathematical operation**.
* and can be denoted by the ~X and V~ mathematical operators
** and can be denoted by the ~mathematical operator.
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8. B = CURL A
where A can contain, for completeness, a term which is the yradient of a
scalar function. In the remaining discussion, the scalar function and
the scalar potential function will be taken to be substantially zero.
Therefore, attention will be focused on the magnetic vector potential A.
In the prior art literature, consideration has been given to the
physical significance of the magnetic vector pntential field A. The
magnetic vector potential field was, in s~me instances, believed to be a
mathematical artifice,J useful in solving problems, but devoid of
independent physical significance.
More recently, however, the magnetic vector potential has been
shown to be a quantity of independent physic~l significance. For
example, in quantum mechanics, the Schroedinger equation for a
(non-relativistic, spinless) particle with chargey and mass m moving in
an electroma~netic field is given by
9 . ~ (~ 6;,~AP -~, A )~ G~n ~ A J ~ f ~
where ~ is Planch's constant divided by 2~ , ; is the imaginary
number ~ , ~ is the electric scalar potential experienced by the
particle, A is the magnetic scalar potential experienced by the particle
znd ~ is ~he wave`function of the particle. The Josephson junction
is an example of a device, operating on quantum mechanical principles,
that is resp~nsive to the magnetic vector potential.
OBJECTS ~F 5HE INNENTION
It is therefore an object of the present invention to provide an
improved system for transfer of infonmation.
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It is a further object of the present invention to provide a system for
the transmission of information that utilizes the magnetic vector potential field.
It is a more particular object of the present invention to provide a
system for transmission of information that utilizes the curl-free portion of the
magnetic vector potential field.
It is another particular object of the present invention to provide ap-
paratus for generation of magnetic vector potential field and apparatus for detec-
tion of the curl-free magnetic vector potential field.
Related Applications
Apparatus and Method for Distance Determination Between A Receiving
Device ~nd A Transmitting Device Utilizing a Curl-Free Magnetic Vector Potential
Field, invented by Raymond C. Gelinas, Serial Number 390,701, filed on November 23,
1981 and assigned to the same assignee as named herein.
Apparatus and Method for Direction Determination by Means of a Curl-Free
Magnetic Vector Potential Field, invention by Raymond C. Gelinas, Serial Number
390,282, Eiled on November 17, 1981 and assigned to the same assignee as named
herein.
Apparatus and Method for Demodulation of a Modulated Curl-Free Magnetic
Vector Potential Field, invented by Raymond C. Gelinas, Serial Number 390,669,
filed on ~ovember 23, 1981, and assigned to the same assignee as named herein.
Summary of the Invention
The aforementioned and other objects are accomplished, according to the
present invention, by apparatus for generating a magnetic vector potential field
A having a substantial component subject to the condition CURL A = O (i.e., a
curl-free magnetic vector potential field component), and by apparatus for detect-
ing the curl-free magnetic vector potential field. By providing apparatus to
modulate the field produced by the apparatus generating the curl-free magnetic
vector potential field, and by providing apparatus to demodulate the curl free
field identified by the detecting apparatus, information can be transferred by
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means of the curl-free magnetic vector potential field.
Examples of the apparatus generating magnetic vector potential fields
with substantial curl-free components include solenoidal configurations and toroi-
dal configurations. The ~osephson junction device is an example of a device which
can detect a curl-free magnetic vector potential field.
In accordance with the present invention, there is provided a system for
transmission of information comprising: field generating means responsive to an
input signal modulated with said information for generating a magnetic vector
potential radiation field having a curl-free component modulated with said infor-
mation; and detector means for detecting said curl-free component of said magnetic
vector potential radiation field said detector producing a signal containing said
information.
In accordance with the present invention, there is further provided a
system for transfer of information comprising: field generating means for gener-ating a magnetic vector potential field having a curl-free component; modulationmeans coupled to said field generating means for modulating said magnetic vectorpotential field with said informatlon; detection means for detecting said curl-
free component o~ said generated vector potential field; and demodulation means
coupled to said detector means for determining said information.
In accordance with the present invention, there is further provided a
method of transEer of information comprising the steps of: a) generating a mag-
netic vector potential field having a substantial curl-free component, said sub-stantial curl-free component modulated with said information; b) detecting said
substantial curl-free component of said vector potential field; and c) extracting
said information from said detected substantial curl-free vector potential field.
These and other features of the present invention will be understood
upon reading of the following description along with the drawings.
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BRIEF _SCRIPTION OF THE DRAWINGS
Figure 1 is a schematic diagram illustrating the procedure for deter-
mining a magnetic vector potential at a point.
Figure 2 is a schematic diagram illustrating the generation of a curl-
free magnetic vector potential field using an infinite solenoid.
Figure 3 is a schematic diagram illustrating the generation of a curl-
free magnetic vector potential field using a toroidal configuration.
Figure 4A is a cross-sectional diagram of a Josephson junction device.
Figure 4B is a perspective view of a Josephson junction device.
Figure 5 is a diagram of the current flowing in a Josephson junction as
a function of the magnetic vector potential field component perpendicular to the
junction surface.
Figure 6 is a schematic diagram of a system for using a curl-free vector
potential radiation field for transmission of inormation.
DESCRIPTION OF THE PREFERRED EMBODIMENT
1. Detailed-Description of the Figures
Referring to Figure 1~ the method of determining the magnetic vector
potential field ~(1) 12 ~i.e., at point 1) is illustrated. Reerring to equakion
6, the contribution by the differential volume element at point 2, dv(2), 11,
having a current density J~2) 13 associated therewith is given by
10. dA~ Cd~r ~ 9
To obtain equation 6, equation 10 must be integrated. Equations 6 and 10 are
valid where J is not a function of time.
Referring to Figure 2J and example of current configuration producing
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a substantial component of curl-free magnetic vectnr p~tential field is
shown. Conductors carrying 3 current I are wrapped in a solenoidal
configuration 21 extending a relatively great distance in b~th
directions along the z-axis~ Within solen~id 21, the magnetic flux
density B ~~L ~ is a constant directed along the z-axis with a value
11. B- E3~ = r) I
where n is the number of conductors per unit length. Outside of the
solenoid, it can be shown that the components of A 23 are
12~ ~x ~ ~ ~ ~ y~
13; Ay ~ ~+,~L
1~ ~z_ ~
where a is the radi~ls of the solenoid. It can be shown that CURL A = O
for the vector potential ~ield outside of the solenoid 21. To the
extent that the solenoid is not infinite along the z-axis, dipole terms
(i.e., cuRL~d ) will be introduced in the magnetic vector potential
field.
Referring to Fig. 3, another ex~mple of a current geometry
generati~g magnetie vector potential field with a substantial curl-free
ccmponent is shown. In this geometry the current carrying conductors
are wrapped uniformly in toroidal configuration 31. Within the toroid~l
configuration, the magnetic flux, B = CURL A 32 and the magnetic flux,
is contained substantially within the torus for A 33. In the region
external to the torus, B = CURL ~ - O and the orientation of ~h~
magnetic vector potential field in the plane of the torus is parallei
the axis of the torus.
Referring to Fig. 4a an~ Fig. 4b, the schematic diagram of a
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detector capable of detecting the curl-free component of the magnetic vector
potential field is shown. This detector is referred to as a Josephson junction
device. The Josephson junction consists of a first superconducting material 41
and a second superconducting material 42. These two superconducting materials are
separated by a thin insulating material 43.` Elements 44 and 45 are conducting
leads for permitting the flow of current tilrough the junction. According to
classical electromagnetic theory, the insulating material 43 will prevent any
substantial conduction of electrons between the two superconducting regions.
However, quantum theory predicts, and experiments verify that conduction can take
place through the insulating material. The result of this conduction is a net
current
15. IJJ~ k sin ( ~ ~ ~ ~ A c~s ~ t; ~t~
where the magnitude of the current K and the phase ~ are determined by intrinsicproperties of the junction device, e is the charge of the electron, A is an ex-
ternally applied magnetic vector potential, ds is a differential element extending
from one superconducting element to the other superconducting element, t is time,
and V is an externally applied voltage. This conduction takes place when leads
44 and 45 are coupled with overflow impedence to the current flow. The component
of the magnetic vector potential field A perpendicular to the plane of the junc- tion determines the current IJJ.*
Referring to Figure 5, the relationship of the Josephson junction device
current as a function of externally applied magnetic vector potential field is
shown. The integral~ as A is increased, results in a change of phase for IJJ.
* Examples of the use of the Josephson junction as a magnetic field detector
have been described in the book "Superconductor Applications: SQUIDS and
Machines . . .",Plenum Press 1976 by Brian B. Schwartz and Simon Foneu and in the
article by Jakleviz et al Phys. Rev. 140 A 628 (1965).
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The dot product of A with ds, where s is the length of the junction perpendicular
to the junction, results in the phase angle of IJJ, being proportional to the
component of A perpendicular to the junction Al. This change in phase produces
the oscillating behavior for IJJ as a function of magnetic vector
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pntential field perpendicular to the Josephson junction. This relation-
ship will hold as long as there is n~ externally applied voltage to the
Josephson junction (i.e., V = 0).
Referring next to Eig. 6, a system for the transfer of infonmation
using a curl-free vector potential field is shown. Apparatus 60 is
comprised of a current source 64 and apparatus 65 configured to generate
a magnetic vector potential field having a substantial curl-free
component using the current fr~m the current source. The magnetic
vector potential field is established in ~he intervening media 61 and
~mpinges upon a magnetic vector potential field detector 66 of
retrieving apparatus 63. The property of detector 66 indicating the
presence nf a magnetic vector potential fielcl is analyzed in apparatus
67 for information content.
2. OFeration of the Preferred Emkodiment
In order to transmit information, it is necessary to vary the field
carrying the information. No mention has been made-in the previous
discussion of the e~fect of modulating the current source. It will be
clear that the finite field propagation velocity will cause a delay
between a change in the vector potential field produced by the generator
of the field and the detection of that change by the detector located at
a distance from the generator. However, these delay effects will be
ignored in this discussion. With respect to curl-free vector potential
field generating apparatus, any limitation on the upper limit of
generated frequency c~mponents imposed wilI be the result of parameters
~mpacting rapid changes in the current. m us parareters su h as
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inductance can provide a limit to ability to impose high ~requency
m~dulation on the vector potential field.
With respect to the media between the field generating apparatus
and the field detectin~ aFparatus, tw~ effects are important. Pirst as
implied by equation (1)
16. CU,~eL F t~ --CIJ~L ~ t C~ L ~d~ C~Lf~t~
or
17. ~t ~ ~ E
Therefore as modulati~n is ~mposed on the vector pntential field, the
change in the vector potential field will prod~ce an electric field
intensity. The electric field intensity will produce a flow of curren~
in conducting material or a temporary polarization in polarizable
material. With respect to materials demonstrating magnetic properties,
the bulk magnetic pr~perties are responsive to the magnetic flux density
B. However, B = CURL A = O for the curl-free vector potential field
component. Therefore, the interaction of the curl-free magnetic vector
potential field is weaker in magnetic materials than is true for the
general magnetic vector potential field. Media effects and especially
~he conductivi~y of the intervening media will provide a mechanism
delaying the achievement of steady state condition for the curl-free
magnetic vector potential field (i.e., because ~A __ ~ ) field and
thus ca~sing a media l~mitation on frequency. A curl-free magnetic
vector poSential field can be established in materials that are not
capable of transmitting nonmal electromagnetic radiation. The media
delay problem can be compensated for by lowering the frequen~y spectrum
of the m~dulation on the curl~free magnetic vector potential field.
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With respect to the detector, the Jnsephson junction can be
constructed to provide responses of sufficiently high frequency so that
this element of the system is not typically a factor lLmiting frequency
of information transfer.
As indicated in equation 12, the effect of the application of a
vector potential field to a Josephson junction, in the absence of a
voltage applied to the junction, is to change the phase of the sine
function determining the value of the junction current I~J . The
excursions from zero magnetic vector potential field can be analyzed and
a determination made of the modulation applied to the field. When a
vnltage is applied to the Josephson junction, oscillation occurs in the
I~J as will be seen from the Vdt term of e~uation 12. The
application nf an external vector potential field causes the phase of
the oscillation to change. By monitoring the phase change in the
Josephson junction oscillations, the modulation of the vector p~tential
field can be inferred.
Another method of detection of a n2gnetic vector potential field
utilizes the property that ~ Thus, for example, by measuring
the changes in a material resulting ~rom the application of the electric
field, the magnetic vector potential field causing the electric field
can be inferred.
Many changes and mGdifications in the above-described embod~ment of
the invention can, of course, be carried out wi~hou~ departing from the
scope thereof. Accordingly, the scope of the invention is intended to
be l~mited only by the scope of the accompanying claims.
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