CA1172756A - Apparatus and method for transfer of information by means of a curl-free magnetic vector potential field - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A system for transmission of information using a curl-free magnetic vec-tor potential radiation field. The system includes current-carrying apparatus for generating a magnetic vector potential field with a curl-free component coupled to apparatus for modulating the current applied to the field generating apparatus.
Receiving apparatus includes a detector with observable properties that vary with the application of an applied curl-free magnetic vector potential field. Analyzing apparatus for determining the information content of modulation imposed on the curl-free vector potential field is coupled to the detector. The magnetic vector potential field can be established in materials that are not capable of transmit-ting more common electromagnetic radiation.

Description

1 l7æ7s6 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 ~ ., ~202860 ~ . 1 10/q5/80 ~
,.. . .

~ 117~7~6 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.

~ 172756 -

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.

~202860 ~ , 3 1~/15/80 ~ a 1 7 27 ~ 6 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 .

` ' 17~756 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.

.t,. .ii ' ~ 1 ~2756 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 t ~7~756 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 520~860 ~ , 7 10/15/80 ! 172756 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).

- ' ~ 72756 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 -8a~

t ~ ~275G

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 5202860 ' . 9 10/15/80 t ~ 7275~
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.

.

. 5202860 ~, 10 1~/15/80 ~ 1 72756 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.

5~02860 ' , 11 10/15/S0

Claims (8)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. 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 information, and detector means for detecting said curl-free component of said magnetic vector potential radiation field, said detector producing a signal containing said information.

2. The information transmission of claim 1 wherein said field generating means includes apparatus for applying a current source modulated with said information to configuration of conductors for generating said curl-free magnetic vector potential field.

3. The information transmission system of claim 2 wherein said detector means includes a Josephson junction.

4. The information transmission system of claim 3 wherein a change in phase in the current of said Josephson junction results from a change in said vector potential radiation field.

5. A system for transfer of information comprising: field generating means for generating a magnetic vector potential field having a curl-free component, modulation means coupled to said field generating means for modulating said magnetic vector potential field with said information; detection means for detecting said curl-free component of said generated vector potential field; and demodulation means coupled to said detector means for determining said information.

6. A method of transfer of information comprising the steps of:
a) generating a magnetic vector potential field having a substantial curl-free component, said substantial 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.

7. The method of transfer of information of claim 6 wherein step a) includes the step modulating a current, said modulated current applied to a configuration of conducting elements producing said modulated substantial curl-free component field.

8. The method of transfer of information of claim 6 wherein step c) includes detecting of current phase changes in a Josephson junction device.