US2036982A - Inductor - Google Patents

Description

Patented Apr. 7, 1936 UNITED STATES PATENT OFFICE INDUCTOR New York Application October 12, 1933, Serial No. 693,387

10 Claims.

My invention relates to inductor structures and more particularly to such inductors as are adapted for operation at high and ultra-high radio frequencies in electron discharge ampliers.

My invention has for one of its objects to provide an improved tuning inductor arrangement forelectron discharge devices operating at high and ultra-high frequencies whereby the effective inductance of said inductor may be reduced without generating oscillations in the ineffective portion of the inductor.

Still another object of my invention is to provide an improved relatively compact tuning inlI'S` ductor for high power amplifiers operating at high and ultra-high frequencies wherein the convolutions of the inductors are arranged to provide for the increased currents flowing therein as the effective inductance is reduced.

It is a further object of my invention to provide an improved inductor arrangement for pushpull connected electron discharge devices operating at high and ultra-high frequencies whereby the effective inductance of said inductor may be reduced without generating oscillations in the ineffective portions and at the same time, maintaining a high mutual inductance between the effective inductor sections throughout the entire tuning range.

It is a* further object of my invention to provide a relatively compact tuning inductor for push-pull connected electron discharge devices operating at high and ultra-high frequencies wherein a high mutual inductance is maintained between the inductor sections, and the convolutions of the inductors are arranged td compensate for the effect of the increased currents flowing in the circuit as the effective inductance of each of the inductor sections is reduced.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. My invention, itself, however, both as to its organization and method of operation together with further objects and advantages thereof, will be understood best by reference to the accompanying drawing in which Fig. 1 discloses a preferred embodiment of my invention; Figs. 2 and 3 show details thereof, and Fig. 4 discloses the electrical circuit of the inductor.

Referring to Fig. l of the drawing, I have illustrated therein an inductor tuning arrangement comprising two like inductors I and 2 arranged coaxially and supported by a suitable (Cl. Z50-40) framework 3. The active portions of the inductors I and 2 are adjacent to each other so that the inactive or ineffective portions of the inductor are at the opposite extremities of the inductor assembly. Each of the inductors I and 2 is provided with a plurality of taps i and 5 which terminate in a plurality of switch point contacts 6 and 'I. These contacts 6 and 'I are supported by a pair of insulating strips 8 and 9 fastened upon the inductor frame 3. A switch comprising an arm or bar member Ii! slides in the space between the insulating members 8 and S, and the bar is provided with a plurality of switch blades II and I2. The switch blade II is of suiiicient width to engage two of the contacts 6 and 'I of each of the inductors I and 2. The purpose of providing such Wide switch blade I I is to maintain a complete short circuit in the ineffective portion of the inductor which is adjacent to the effective portion of the inductor. The additional switch blade I2 provides an additional electrical path through the ineffective portion of each inductor, thereby preventing the ineffective portion from oscillating at some harmonc frequency of the frequency present in the active portion of the inductor.

The manner of mounting the switch may best be seen by referring to Fig. 2 which is a cross section of that portion of Fig. l as indicated by the arrows II, wherein it will be noted that the arm or bar member Il) is compose-d of an insulating material having at the back thereof, a conductance strip i3 to which the switch blades II and I2 are fastened by means of cap screws. A binding post I4 is in electrical contact with the conducting bar i3 by means of a spring contact I5.

The switch blades I I and I2 are in continuous contact with the taps at the remote extremities of the inductors, as will be apparent by an examination of Fig. 3 which is a cross section of that portion of Fig. 1 viewed in the direction of the arrows III, wherein it will be noted that a binding post I4 supports a metallic bus bar I6 as well as the spring clip I5. The bus bar I6 is connected electrically by direct contact to the taps 4 and 5 and the switch points 6 and 'I by means of cap screws.

Reference may now be had to Fig. 4 wherein I have shown the electrical circuit and the manner in which the inductor may be used. While I have shown the inductors connected in the output circuits of the electron discharge devices Il and I8, it is to be understood that a similar inductor arrangement could be suitably used in the input circuit of such an amplifier. In other words, the adjacent extremities of the inductors are connected to the input or output electrodes, which may be termed the ungrounded electrodes. The anodes of the discharge devices II and IB are connected to the extremities of the inductors which are adjacent to each other, and the anode current is supplied from a suitable source through a choke coil I9 which is connected to the taps 4 and 5 which are at the remote extremities of the inductors I and 2. When the switch blade I is at the extreme right position, the blade II rests on only the two contacts at the extreme right so that both the inductors are at maximum inductance. As the switch arm I0 is moved to the left, the switch blade II Will first contact the first two pairs of switch points 6 and 'I and further motion of the switch will move this switch blade along until it has reached the fourth and fifth pairs of contacts as counted from the right to the left, whereby at that moment the switch blade I2 will make contact with the extreme right pair of switch points. It will be apparent that as the switch is moved farther to the left the switch blade I2 provides an additional electric path through each of the ineffective portions of the inductors, thereby maintaining various portions of the inductor at ground potential so as to prevent the generation of spurious oscillations within the ineffective portions of the inductors. The outputs of the elctron discharge devices I1 and I8 are connected to the succeeding circuit through the coupling capacitors 2D and 2I. The output circuit is tuned by varying the total effective inductance of the inductors and by a variable capacitor 22 connected between the anodes which in conjunction with the inherent capacity 23 existing between the adjacent extremities of the inductors, operates to determine the resonant frequency of the output circuit.

As the switch arm I0 is moved to the left to reduce the total effective inductance of the inductors, the resonant frequency of the output circuit is increased and at the same time, the radio frequency current through the active portion of the inductors increases in magnitude. This increase in radio frequency current is caused by the increased ratio of capacity to inductance in the circuit as the circuit is tuned to the higher frequencies.

The inductor disclosed in Fig. 1, therefore, is provided with convolutions which increase in size from the inactive end to the active end of each inductor. By forming the convolutions of the inductor of different size conductors, instead of a single size large conductor, it is possible to arrange such an inductor within a very limited space.

While I have shown and described the application of the inductors to a particular type of amplifier, i. e. a push-pull or balanced amplifier, it is to be understood, of course, that inductors can be used individually in amplifiers of the single cascade type. The inductors when used individually have the advantages of compact structure, and a plurality of electrical paths in the ineffective portion which prevent the generation of spurious oscillations. While a specific switching arrangement is shown, it is obvious that any other arrangement could be employed which would produce the same results.

While I have shown and described my invention in connection with certain specific embodiments, it Will. of course, be understood that I do not wish to be limited thereto since it is apparent that the principles herein disclosed are susceptible of numerous other applications, and modifications my be made in the circuit arrangements and in the instrumentalities employed without departing from the scope and spirit of my invention as set forth in the appended claims.

What I claim as new and desire to obtain by Letters Patent of the United States, is:

1. A tuning device for a pair of electron discharge devices, said device comprising a pair of inductors arranged coaxially, said inductors having adjacent extremities connected to the high potential electrodes of said discharge devices, and means for reducing the effective inductances of said inductors simultaneously by like amounts, said means operating to produce a plurality of electrical paths through the other extremities of said inductors thereby to render said other extremities ineffective while maintaining said ad'- jacent extremities effective.

2. A tuning arrangement for a pair of electron discharge devices including a pair of inductors arranged coaxially, said inductors having adjacent extremities connected to the high potential electrodes of said electron discharge devices, a plurality of taps on each of said inductors, and means for reducing the effective inductances of said inductors simultaneously by like amounts, said means including a switching arrangement cooperating with said taps for producing in each of the opposite ends of said pair of inductors a plurality of electrical paths thereby to render said opposite ends ineffective while maintaining said adjacent extremities effective.

3. A tuning device for a pair of electron discharge devices, comprising two like inductors arranged coaxially, said inductors having active extremities arranged adjacent to each other and connected to the high potential electrodes of respective discharge devices, a plurality oi taps on each of said inductors, and means cooperating with said taps for reducing the effective inductances of said inductors by rendering ineffective like amounts of said inductors, said means including means for short circuiting different unequal portions of each inductor while maintaining the adjacent extremities of said inductors active.

4. A tuning device for a pair of electron discharge devices comprising a pair of inductors arranged coaxially, said inductors having active extremities arranged adjacent to each other and connected to the high potential electrodes of said discharge devices thereby maintaining high mutual inductance between said inductors, a plurality of taps on each of said inductors, and means cooperating with the other extremities of said inductors and said taps on each of said inductors for rendering said other extremities ineffective while maintaining the adjacent extremities effective, said means including a switch for producing a plurality of electrical paths in each of the portions of said inductors to be rendered ineffective, said switch including means to short circuit a relatively small portion of each of said inductors immediately adjacent to the effective portions of said inductors.

5. A tuning device for a pair of electron discharge devices comprising a pair of inductors arranged coaxially, said inductors having active extremities arranged adjacent to each other and connected to the ungrounded electrodes of said discharge devices, each of said inductors comprising a helical conductor having larger cross sections at the active extremity than at the other extremity, and means for rendering ineffective like portions of each of said inductors, said means including means for producing a plurality of electrical paths through each of said ineffective inductor portions thereby preventing the generation of oscillations therein.

6. In combination, an inductor coil adapted for operation over a wide range of frequencies, said inductor coil comprising turns of larger diameter at one end than at the other, means connecting a portion of the coil at the end having the smaller diameter turns continuously in circuit and for short circuiting unequal portions of the remainder of the coil, and means to increase the portion of the coil connected in circuit While maintaining unequal portions of the remainder of the coil short circuited.

7. In combination, a pair of electron discharge devices connected in balanced relation, a pair of coaxially arranged inductance coils, said coils having adjacent ends connected to the output high potential electrodes of said discharge devices, the turns of said coils at said adjacent ends having dimensions corresponding to the shorter of the wavelengths at which said coil operates, the turns of said coils increasingly removed frorn said ends having dimensions differing in accordance with the increasing Wavelengths at which the coil operates when the respective increasingly removed turns are active, and means to connect together variable points on each of said coils, said points being equally removed from said ends, and means to short circuit the portion of each of said coils more removed from said adjacent ends than said variable points.

8. In combination, a pair of inductor coils arranged in end to end coaxial relation, the adjacent ends of said coils being connected together through a capacitance resonant therewith, and the outer ends of said coils being connected together to complete an oscillatory circuit comprising said coils and capacitance, means to excite oscillations in said coils whereby said adjacent ends oscillate at high potential, and means to short circuit portions of said coils remote from said adjacent ends while maintaining said adjacent ends active whereby the resonance irequency of said circuit is varied and close coupling between said coils is maintained at the different operating frequencies.

9. In combination, a pair of inductor coils arranged in end to end coaxial relation, the adjacent ends of said coils being connected together through a capacitance resonant therewith, and the outer ends of said coils being connected together to complete an oscillatory circuit comprising said coils and capacitance, means to excite oscillations in said coils whereby said adjacent ends oscillate at high potential, the turns of said coils near said adjacent ends having dimensions corresponding to operation at high frequencies and the dimensions of the turns of said coils increasingly removed from said adjacent ends diifering in accordance with operation at lower irequencies.

10. In combination, a pair of inductor coils arranged in end to end coaxial relation, the adjacent ends of said coils being connected together through a capacitance resonant therewith, and the outer ends of said coils being connected together to complete an oscillatory circuit comprising said coils and capacitance, means to excite oscillations in said coils whereby7 said adjacent ends oscillate at high potential, and means to short circuit portions of said coils remote from said adjacent ends while maintaining said adjacent ends active whereby the resonance :tre-

quency of said circuit is varied and close couf pling between said coils is maintained at the different operating frequencies and in balanced relation with respect to ground, and means to short circuit unequal portions of each of said coils removed from said adjacent ends while mainm taining said adjacent ends active, whereby the frequency at which said circuit operates is varied while close coupling between said coils is maintained at all operating frequencies.

EDWARD A. LEACH.

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