US2026712A - Composite oscillator for electromagnetic waves - Google Patents

Description

Jan. 7, 1936. J. 5. STONE COMPOSITE OSCILLATOR FOR ELECTROMAGNETIC WAVES Filed June 1, 1933 INVENTOR film/n Sta/Le Stone ATTORNEY Jan. 7, 1936. J. 5. STONE 2,026,712

COMPOSITE OSCILLATOR FOR ELECTROMAGNETIC WAVES Filed June I, 1933 3 Sheets-Sheet 2 INVENTOR Jlu a Stwwe Sta/Le ATTORNEY Jan. 7, 1936. I J. s. STONE 2;026,7l2'

COMPOSITE OSCILLATOR FOR ELECTROMAGNETIC WAVES Filed Ju ne l, 1933 3 Sheets-Sheet 5 /=l (goproxmate) 76' z' /l watts 5 kg #93 5% 1/2 A zj/z 21 54/2 5/1 7A/2 4A 7@.2 i /21 Quits 3% (2) (2) '2 2 A 52 2 22 52 2 INVENTOR John Stane 660m BY 561M A'fTORNEY Patented Jan. 7, i936 I s l, i

UNITED STATES PATENT. OFFICE COMPOSITE OSCILLATOR FOR ELECTRO- MAGNETIC WAVES John Stone Stone, San Diego. Calif., assignor to American Telephone and Telegraph Company,

a corporation of New York Application June 1, 1933, Serial No. 673,926

4 Claims. (01. 250-33) An object of my invention is to provide a new '10 is a corresponding diagram for electromotive and improved system for generating and radiatforces; in Fig. 11 the diagram of Fig. 7 has been ing electromagnetic waves. Another object is extended to several adjacent and consecutive to accomplish the radiation of such waves withcomponent oscillators; in Fig. 12 the diagram of substantial energy. My invention may 'beprac- Fig. 8 has been similarly extended; Fig. 13 is a 5 ticed advantageously for the effective generation diagrammatic axial or longitudinal section of and radiation of waves of comparatively short an oscillator built according to the principle of length. In one aspect this invention involves my invention; Fig. 14 is a diagram illustrating providing an effective radiating oscillator of a how the various component oscillators may be length considerably greater than a half wave marked off from each other by impedance con- 10 length. This oscillator may comprise adjacent nections instead of by physical discontinuities; oscillators lapping past each other and each Fig. 15 .is a diagram in which the representation shorter than the overall length of the composite is changed somewhat from that of Fig. 1; Figs. oscillator. The foregoing statement of objects 16 and 1''! are diagrams showing radiated wave l5 and advantages of my invention has been made shapes corresponding respectively to parts (I I) 15 with reference to radiation or transmission of and (1) of Fig. 3; Fig. 18 is a diagram showing energy, but it is well known that in general any the power from the central part of a well-known good radiator of energy is an equally good abtype of oscillator as a function of its length; and sorber of energy. Any system will have the same Fig. '19 is a similar diagram with comparison of go absorption spectrum as its radiation spectrum. a radiator made according tomy invention. 20

Accordingly, it will be understood that structures An embodiment of my invention is shown diato operate as composite radiators embodying my grammatically in Fig. 1. Side by side are two present invention will be readily applicable to rows of component oscillators, such as the osciloperate as receivers. For convenience I shall lator 2,5 in one row or the oscillator 22 in the make the following description principally for other row. Each such oscillator consists of a 25 radiators. All the foregoing and other features, length of straight conductor with a coil 23 inobjects and advantages of my invention will beterposed at its middle, and each oscillator in one come apparent in connection with the followrow laps half-way past each of two consecutive ing disclosure of a few examples of practice acoscillators of the other row. At the ends, top

cording to the invention which I have chosen for and bottom, the half-length conductors 2 l' and 30 presentation in this specification. It will be un- 22' are terminated by capacity areas. The disderstood that the following description relates tance between these two capacity areas is conprincipally to these particular embodiments of siderably greater than the half wave length in the invention, and that the scope of the invenfree space to which each component oscillator tion will be indicated in the appended claims. is tuned. 7 3

Referring to the drawings, Figure 1 is a dia- The principles involved in the composite osgrammatic elevation of an oscillator and associcillator of Fig. 1 and the mode of its operation ated circuits adapted for the practice of my inwill be developed in the discussion which follows vention; Fig. 2 is a diagrammatic elevation of in connection with Figs. 2 to 12.

40 a single component tuned oscillator; Fig. 3 is a A single simple oscillator is shown in Fig. 2, 40 set of diagrams showing wave shapes for currents a straight length-of conductor wire with a tuning and electromotive forces in simple oscillators of coil interposed at its middle and an associated various lengths compared to the wavelength for inductively related circuit 24 bywhich alternatwhich they are tuned alike; Fig. 4 is an ening current energy may be fed into the oscillator.

5 larged diagrammatic elevation of a section of Assuming that various lengths are given to the the oscillator of Fig. l s o i g conduction and oscillator of Fig. 2 but that in each case the tundisplacement currents; Figs. 5 and 6 are diaing coil is adjusted so that the wave length in grams showing desirable wave shapes for curfree space will be the same, diagrams arefshown rent and electromotive-force in an oscillator; in Fig. 3 for the current Wave shapes and the 59 Fig. '7 is a diagram showing current wave shapes electromotive force wave shapes. in a component oscillator whose length is one In each of these diagrams the continuous line wave length; Fig. 8 is a corresponding diagram curve shows the current wave shape of maximum for electromotive forces; Fig. 9 is a diagram values, and the dotted line shows the electromoshowing current wave shape in a component ostive force wave shape of maximum values. But,

cillator whose length is two wave lengths; Fig. of course, the maxima of one curve do not occur at the same instant of time as for the other curve, but are 90 apart in phase. The current is at or near zero when the electromotive forces are at or near their maximum. The dotted lines may also be regarded as representing conditions of static charge when the current is at or near zero, as well as representing electromotive forces.

The third part of the diagram of Fig. 3, for an oscillator of length equal to a half wave length in free space, shows a simple readily understood current wave form and electromotive force wave form. Making the oscillator a little longer, as in the fourth part of the diagram, that is, fiveeighths of a wave length instead of one-half of a wave length, it is necessary to interpose a substantial amount of tuning coil inductance at the middle point to preserve the same Wave length in free space. There will be a sharp potential drop across this inductance coil which is represented by the part of the dotted line extending at a right angle to the length of the oscillator.

Starting with the tuned linear oscillator of the first part of Fig. 3, whose effective length is a quarter wave length, and increasing this length by one-eighth wave length at each step, but keeping the wave length in space the same by means of the adjustable tuning coil at the middle of the oscillator, we proceed from left to right through all the parts of Fig. 3, and at the extreme right We have the case of an oscillator whose length is full two wave lengths. In all these parts of Fig. 3 we assume the same maximum terminal difference of potential, that is, the ordinates at the ends of the dotted line curves, for example at 25, are all equal in absolute magnitude.

From the first part of Fig. 3 at a quarter wave length to the third part at one-half wave length, the intensity of the radiation in the equatorial plane of the oscillator will increase very rapidly. Going on, the intensity decreases until it becomes practically nil in the seventh part of the figure. Going on, it waxes and wanes as before. There is a maximum at each length of the oscillator that is an odd multiple of a half wave length and a null value at each length that is equal to an even number of half wave lengths.

Certain considerations leading to the'present invention will now be mentioned with reference to Figs. 16 to 19.

The maximum possible radiative power per unit of length of a straight conductor is given by the expression 401r Zi watts, in which Z is the length of the conductor, A is the wave length of the radiation in free space, and i is'the current amplitude throughout the conductor expressed in amperes. We see therefore that for a given current amplitude and wave length, this maximum possible radiative power per unit of length of the conductor is proportional to the length of the conductor. But the condition of the foregoing expression is only true, and the maximum possible radiative power of a given linear oscillator is therefore only attainable when the amplitude i of the current is constant throughout the length of the conductor.

Furthermore, an. ordinary linear conductor executing oscillations whose wave length x is small compared to twice the length of the linear conductor, has a current amplitude distribution which is far from uniform throughout the length of the conductor. Under these circumstances the current amplitude is distributed along the conductor in loops with intervening nodes as illustrated by the full line curves of (1) to (l5-) ,'Fig. 3 of the drawings.

Again, the radiation from each ventral segment of current amplitude in such a relatively long linear oscillator throws off a separate train of waves which pursues its own individual course difierent from that radiated from any other ventral segment of current amplitude in the oscillator. This is illustrated by Figs. 16 and 17. The arrows indicate the direction of motion of the dilferent trains of radiation from the several ventral segment of current amplitude.

It is to be noted that in Fig. 17, where 2:) there is no radiation in the equatorial plane of the oscillator ab, while in Fig. 16-, where the radiation in the equatorial plane of the oscillator ab is due solely to the central ventral segment of current amplitude.

Or inar l e a en he than that in h equator a plfi fit W 3? tha useless as t; s. o te be ba i ea th by the Heaviside layer and causes interference with the direct rays as well as interfering with the directive characteristics of directive receivers andradio compasses.

From all this we see that, other things being equal, the maximum possible useful power of radiation per unit of length of a linear'oscillator, without capacity areas and tuned by a coil at its centre to the period of the waves, is attained when l= (or more exactly Z=0.4767\), under which circumstances the tuning inductance is zero and the current amplitude distribution is that illustrated in Fig. 3, part (3).

The component of this current amplitude which is constant throughout the length of the conductor is timesthe maximum amplitude i, so that the foregoing expression in watts becomes loom/2e: 76.21%

watts.

For a given maximum current amplitude i and wave length A, any increase or decrease of the length Z of the oscillator from (approximate) diminishes the power radiated per unit length of the oscillator from the central part of the oscillator (which is all the radiation that is commonly useful in practice). When the length of the oscillator isl= (or more exactly 0.97 6x) the power radiated from the central part of the oscillator per unit of length of the oscillator is zero. This is case (1) of Fig. 3 and the case of Fig. 17.

When

(or more exactly 1.4'76 the power radiated from the central part of the oscillator per unit of length of the oscillator is again a maximum, which however is slightly smaller than one third that reached. when This power radiated from the central part of the oscillator perunit of length of the oscillator reaches subsidiary maxima for (approximately), when p is any odd integer and reaches zero minimum for when q is any even integer. The fluctuations of the radiation from the central part of the oscillator per unit of length of the oscillator, and for given i and A, as Z is increased from zero to 4). is illustrated in Fig. 18. In view of the foregoing condition in respect of the radiative power of linear oscillators, I have undertaken the task to devise means whereby the radiative power per unit of length of linear oscillators for given maximum current amplitude and wave length may be made to increase continuously with increase of the length of the oscillator, even when the length of such oscillator exceeds the critical value (more exactly 0.476%) If this radiative power is tobe made proportional to the length of the oscillator as illustrated in the right line of Fig. 19, it is clearly necessary to cause the effective current amplitude, for points in space outside the oscillator system, to be constant throughout the length of the oscillator.

It is not possible to make the total current amplitude in this oscillator constant throughout the oscillator forthis would involve infinite phase speed. So I employ a compound oscillator in which the oscillations of the individual parts or component oscillators consist of nodes and loops, but in which, so far as the field of force external to the compound or resultant oscillator is concerned, the effective current amplitude in the compound oscillator will be constant throughout its length.

The curve (2) of Fig. 19 represents the power radiated per unit length of conductor from the central portion of an ordinary linear oscillator, and is the same as the curve of Fig. 18 but to a smaller scale of ordinates and a longer scale of abscissas. It is given to illustrate the gain possible to be effected through the use of the compound oscillator.

The waxing and waning described heretofore of the radiation in the equatorial plane of the linear oscillator of Fig. 3 when its length is in-' creased may be identified with the development of standing waves, the length of each such standing wave being approximately a half wave length in free space. When these standing waves have a node at the center point of the oscillator there will be no radiation in itsequatorial plane, but when they have a loop at that point the intensity of the radiation is a maximum. At a considerable distance from the oscillator represented by part (I) of Fig. 3, assume a certain plane surface of definite area lying transverse to the equatorial plane, and transverse to the direction of propagation in that plane. Let the power or the rate of flow of energy across this area be unity. Next let the length of the oscillator be increased so that the radiation is a maximum, that is, so that the length of the oscillator is a half wave length or three halves times a wave length,-or any odd number of half wave lengths. Then it can readily be shown that the power or energy fiow through that same area will be 6.8 units.

The effective length of a linear oscillator for short wave lengths, that is, its length for the purpose of comparison with the wave length in free space, is very nearly the same as the physical length; the two lengths are connected by the equation Z=l+ \/41.5, where l is the efiective length, l is the physical length and A is the wave length.- r

For intensity of radiation it is evident that the oscillator of the third part of Fig. 3 is no less advantageous than the longer oscillators in the parts of the figure to the right. But if we could havean oscillator of the same length as the oscillator in the extreme right-hand part of this figure, and have the same electromotive forces at its ends (as at with the electromotive force distribution as shown by the dotted line in Fig. 5, and with the current wave shape shown in Fig. 5, then we would get far greater intensity of radiation, indeed, the intensity would be sixteen times greater than for the third and eleventh parts of Fig. 3, or somewhat more than. I08 when the intensity for the first part of Fig. 3 is taken as the unit. Further, if we were to put capacity areas at the ends of this oscillator, as shown in Fig. 6, and have the same extreme electromotive forces at the ends (as at 25"), then we might have a current of nearly the same magnitude all along the length of the oscillator, as shown by the full line curve 5| in Fig. 6, and in this case, if the maximum amplitude of the current were the same as in Fig. 5, the intensity of radiation would be about 26 times that of the third and eleventh parts of Fig. 3, or about 170 times the intensity in the first part of Fig. 3.

The oscillator of Fig. 1 is constructed and de- Theoscillator of Fig. l is built up of 1 equal linear oscillators end to end staggered along two parallel axes, as already described in connection with: that figure. Thus, when executing free oscillations the two lines of oscillators have the opportunity to form two sets of loops of potential and current amplitude which neutralize the effects of each other in the medium directly surrounding the oscillator, leaving only a component of current whose amplitude is substantially constant throughout the length of the composite oscillator as a whole. This creates an external field of radiation due to the resultant overall potential amplitude, so that there is a substantially constant cylindrical distribution of electric force around the axis of the oscillator in its intermediate portion.

In Fig. '7 I have shown one component oscillator component oscillator. In the complete, composite oscillator I want a. wave shape such as represented by the dotted line 26. But in the complete composite oscillator there are. two rows. of component oscillators, so I will assume. that only half the desired current represented by the line 26 is to be attributed to the oscillator shown. in Fig. 7. This gives, the line 27. being one component of the current represented by the full line curve 28., the other component isreadily seen to be represented by the dotted line curve 29,.

As indicated by the dotted line in Fig. 6, the electromotive force is expected to grade uniformly from one end to the other of the complete composite oscillator. The actual electromotive force wave shape in a single component oscillator will be as shown by the fullline curve 30. in Fig. 8, and its, components are readily seen to be given by 31 and 32.

The component oscillators of Fig. 1 may have other lengths than a wave length infree space, as was assumed in connection with Figs. '7 and 8. Figs. 9 and 10 are corresponding diagrams for the case in which each component oscillator hasa length equal to two wave lengths in free space.

Whereas Fig, '7 deals with a single component oscillator, Fig. 11 shows a plurality of such oscillators in a short section of length of the complete oscillator of Fig. 1. For the sake of clearness, the oscillators have been thrown outof alignment, as indicated by the horizontal dotted lines each with an arrow head showing the direction of displacement. With the explanationv that has been given heretofore, the significance of Fig. 11 will be apparent at once.

Similarly, Fig. 12 shows the electromotive forces for several associated oscillators as compared with Fig. 8, which is for a single component oscillator alone.

In Fig. 11 the total current in the complete composite oscillator is represented in twoparts, half in the line 33 and half in lines 34 and 39, and. in Fig. 12 the electromotive force is represented by lines of equal slope as at 42 and- 43.

Referring to Fig, 11, consider that. part of the complete oscillator lying between the points a2 and b1. It will be seen that the alternating components represented by the dotted curves 31: and 38 tend to neutralize each other for-points outside the immediate vicinity of the two-conductorswithin this stretch, and the same is true for'the alternating components of the current amplitudes of the corresponding parts of all juxtaposed component oscillators. But the straight linecomponents 33 and 39 add to give a straight. line resultant corresponding to the straightline |v of Fig. 6. Also, in Fig. 12 we see that the components represented by the curves 4D and 41 neutralize and the components represented by 42 and 43, coincide to give us the overall distribution ofelectromotive force.

The two simple oscillators 21 and 22 of Fig. 1 are represented by the like reference numerals in Fig. 4. Here the dotted lines represent lines of. current flow. Within each unit oscillator 21. or 22 the current flow is conductive, as for example at 20. But in the air gap betweenthe'members 2| and 22 the current isa displacement current, as represented at H? in Fig. 4. Thus, although the conduction current in any one'cscillator unit such as 2| or 22 is an oscillatory-currententirely within that unit, the combined; conduction currents and. displacement currents of, the; complete oscillator as a whole give a uniform currentalong the. length of the completeoscillator asa-whole,

thouglrof course this current ,varies cyclically in time.

Instead of lapping the simple oscillators past each other in the manner indicated in Fig. 1, they may be built as shown in Fig. 13, where the lower part of each simple oscillator is a cylinder 44 closed above and open below, and the upper part,

the arrangement of Fig. I may be looked upon as I diagrammatic and equivalent to the arrangement shown in. Fig. 15. The more essential feature is thatin a linear sequence of linear oscillators each extending lengthwise along the general direction of the sequence as a whole, each oscillator laps a substantial distance,'preferably half-way, past the two adjacent oscillators in the sequence.

The elementary theory of the steady state of the. forced current and potential oscillations in a compound linear conductor of the type that has been disclosed in Figs. 1, 13; 14 and 15, may be made to rest on the following assumptions, for the sake of simplicity. It may be assumed that the dissipative resistance of each component oscillator is concentrated at themiddle point of its length,.that the component oscillators are all equal, that the oscillations are maintained by equal impressed, electromotive forces at the middle point of each oscillator, and that the radiation, resistance of the complete compound oscillator may be assigned in equal portions to the various component oscillators and form part of the dissipative resistance that is assumed to be lumped at the middle points of the component oscillators. e

On the foregoing assumptions which are obv1- ously. valid for the sake of simplifying the mathematics, the mathematical theory of the distribution of currents and electromotive forces can be worked out and the-results afford a check on the theory and may be relied upon to some extent for guidance in constructing and operating the system such as shown in Fig. 1.

The complete compound oscillator acts in one aspect like a balanced metallic circuit, and in another aspect like a single conductor. In the first aspect of a balanced metallic circuit, the cur-rentand potential amplitudes in this circuit are indicated by the'dotted curves such as 31 and 38. 111 Fig. 11 and land 4| in Fig. 12. In the other aspect of a single conductor, the current amplitude, is indicated by adding the ordinatesof the" dotted lines 33and 39 in Fig. 11; and the potential amplitude is given by a line having double the steepness of the-lines 42 and 43 in Fig. 12. J v

The quantity of energy thatcan be radiated at a certain short wave length from a single oscillator alone is small. Though they quantity of energy might be increased by increasing the size of the oscillator and making the wave length longer, this may not be what is desired. When it is desired. to make the oscillator larger and thereby increase the; radiated. energy but keep ashort wave length, thenmy system as illustrated diagrammatically in Fig. 1 may be employed. This acts like a long oscillator in respect to quantity of energy radiated but keeps the short wave length established in connection, with each component oscillator.

What is claimed is:

1. In combination, a series of equal linear oscillators arranged lengthwise and consecutively along a common line, each oscillator being tuned to the same comparatively short wave length, each oscillator lapping half-way past both consecutively adjacent oscilators in series, capacity areas connected to the end oscillators oi the series, respective energy transmitting circuits connected with the oscillators, and phase adjusters in said circuits to keep said oscillators inthe same phase.

2. A radiator for electromagnetic waves consisting of a. series of linear oscillators each lapping substantially half way on the consecutively adjacent oscillators of the series, each oscillator having a winding at its middle point, an inductively related energy transmitting winding at each such place, respective circuits comprising these last mentioned windings, a central device to which all these circuits are connected, and phase adjusting means in these respective circuits.

7 3. A radiator for electromagnetic waves consisting of a series of linear oscillators each lapping substantially half way on the consecutively 5 adjacent oscillators of the series, the end oscillators of the series have capacity areas, eachoscillatorhaving a winding at its middle point, an inductively related energy transmitting winding at each such place, respective circuits comprising 10 lators lying in staggered relation in two rows side 20' V by side, and impedances between the consecutively adjacent ends of' the oscillators in each row to separate them electrically. 7 JOHN STONE STONE.

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