US3003068A - Parametrically-excited resonators - Google Patents

Description

Oct. 3, 1961 o. A. JORGENSEN 3,003,068

PARAMETRICALLY-EXCITED RESONATORS Filed March 18, 1959 i v I 3\,' l I I I I I I.

I N Is I L "I L J J INVENTOR.

OTTO A. JQRGENSEN WAN/5% ATTORNEY Unitem Pa fi oi PARAMETRICALLY-EXCH'ED f Otto A; Jorgensen, NY lssignor to General Dynamics Corporation, a corporation of Delaware t Filed Mar. 18,;1959,'Ser.-No;800,282 x V y 1 Claim. 7 (Cl. 307-88) 7 starting signal, oscillation being sustained by changing the impedance of the inductive tank element at a rate that is twice the resonant frequency of the tank. Such a resonator has been described by Ei-ichi Goto in a paper entitled n the Application of Parametric-ally-Excited Non-linear Resonators, appearing in the Journal of Electrical Communications Engineering of June 1955. While such a resonator taken by itself may be useful, it usually finds application in systems requiring a number of intermittently operable sources or generators which are capable of producing synchronous signals.

Accordingly, it is an object of my invention to provide a group of new and improved signal sources capable of producing synchronous signals.

Another object of my invention is to provide a system for driving a group of parametrically-excited resonators in synchronism.

Another object of my invention is to provide a new and improved system for synchronously varying the value of each of the inductive elements within a group of parametn'cally-excited resonators. 7

Another object of my invention is to provide a system including new and improved paranietrically-excited resonators which continue to produce output signals until stopped from a common point;

I accomplish these and other objects in the preferred embodiment of my invention which is set forth below. For the convenience of the reader, reference is made in the following'paragraphs to the drawing attached to and forming a part of the present specification which shows a schematic diagram of a system having a group of parametrically-excited resonators.

Referring to the drawing, I provide a group of parametri'cally-excited resonators, such as 1 and 2. While the following detailed description of resonator operation is confined entirely to resonator 1, it is to be understood first, thatresonator 2 functions in the same manner, and second, that as many other resonators substantially identical to resonators 1 and 2 as required by the system can be provided without altering the principles of operation set forth in the following paragraphs.

Each resonator includes a tank. In the case of resonator 1, the tank comprises capacitor 8 connected in parallel with an inductive element which includes seriesconnected coils 6 and 7. Coils 6 and 7, which may be a path concentric with core 4 are equal and opposite,

and therefore undetectable across capacitor 8. g The material and dimensions of core 4, the number of turns in coils tive for "producing signals at substantially the resonant frequency of the tanks. Means individual to each resonator, such as normally open, manually operable switch 9 in thecase of resonator 1,-is provided for connecting generator 10 across the corresponding tank, so that gene erator 10 momentarily drives resonator l at its resonant 7 frequency from the time switch 9 contacts are closed 'until they are reopened. The effect of 'this momentary starting signal tothe' tank of any resonator is'to be explained presently.

The material used to form core 4 is chosen so that the permeability, and hencethe inductance of coils 6 and 7, changes as the magnetic flux density within core 4 is changed. This non-linear characteristic of the inductive element of each tank is used to sustain resonator 1 and i all other resonators in oscillating condition after a starting signal has'been applied to their tanks. Accordingly, I provide a second signal source including generator 11 which is common to all resonators and is continuously operative for producing a signal at substantially twice the resonant frequency of the tanks within the various resonators. In order to modify the inductance presented by the inductive element within the tank of each resonator,

winding 14, which embraces core 4, is operative in response to the current flow therein for exciting core 4, i.e., controlling the flux density in and concentric with core 4, thereby controlling the permeability of core 4. Means including battery 12, variable resistor 13, and normally closed switch 15 is provided for connecting generator 11 in series with coil 14. With this arrangement, the flux density within core 4, and hence the induction of coils 6 and 7, is varied at twice the resonant frequency of the tanks within the various resonators. By adjusting the value of resistor l3, the flow of direct current from battery 12 through coil 14 is regulated to drive the average flux density within core 4 to the point where the permeability of core 4 swings within the upper and lower limits as the alternating current component from generator 11 is passed through winding 14 requiredto change the inductance presented by the coils within the various resonator tanks sufficiently to sustain oscillation within those resonator tanks.

In the absence of an exciting signal from external generator' 10, none of the resonators including 1 produces a signal across its tank even though current fromgenerator 11 continues to flow through winding 14. However, the operation and release of switch 9 in theaforernentioned manner and the resulting momentary application This continuing signal across the tank constitutes an output signal for the resonator and, as such, is coupled directly to load 5, where it is utilized. 7

In order to stop all resonators at the same time, normally closed switch 15 is operated and thereby stops the previously described change of permeability within core 4. As a result, the value of the inductive element within the coils of all resonator tanks becemesfixed. and the mimetic, 3, 1951 signal across the outputs'of the actuated ones of the resonators decaystozero. Switch 15 can thereuponbe-rement of my invention, other modifications will readily occur to those skilled in the art.

I do not therefore desire my invention to be limited to the specific arrangement shown and described andI intend in the appended claim to cover all such modifications within the true spirit and scope of my invention.

What I claim is:

In a'signaling system, a plurality of substantially identical parametrically-excited resonators, each of said resonators comprising first and second windings and a capacitor, a multi-aperture core of magnetic material common to said resonators, said core having an aperture for each of said resonators, said first and second windings in each resonator being wound through the aperture for that resonator and around an individual portion of said -4 a core, means for connecting the first and second windings in each-resonator in seriesopposition and in'circuit with the capacitor in that resonator to form a resonant circuit having a resonant frequency f, a control winding disposed in inductive relationship with said core, means for applyingan-exciting signal having afrequency which is a harmonicoffrequency f to said control winding, and means for' selectively applying an input signal of frequency f-to tlieresonant circuit in any one of said resonators.

References Cited in the file of this patent UNITED STATES PATENTS 1,544,381 *Elmenet a1. June 30, 1925 15 FOREIGN PATENTS 778,883 Great Britain July 10, 1957 OTHER REFERENCES Magnistor, published by Potter Instrument Co., Inc., 20 11s Cutter Mill Road, Great Neck, NY. 4 pages).

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