US2276879A - High frequency oscillator - Google Patents

Description

March-17, 1942. M. A.- ROTE 2,276,879

' HIGH FREQUENCY OSCILLATOR I Fild .Nov. 10, 1939 I LOAD GRID mew/r INVENTOR MELVIN r4. R072 ATTORNEY Z Patented Mar. 17, 1942 2,276,879 HIGH FREQUENCY OSCILLATOR.

Melvin A. Rote, Newark, N. J assignor to International Telephone Development Co. Inc., New York, N. Y., a corporation of Delaware Application November 10, 1939, Serial No. 303,750

4 Claims. (Cl. 250-36) My invention relates to oscillators of the type.

for generating high frequencies and more particularly to an improved method of constructing a self-controlled oscillator.

An object of my invention is to provide an oscillator having a high degree of stability.

A further object of my invention is to provide a buffer circuit particularly adapted to high frequencies. With my invention an amplifier stage to isolate the oscillator from a load is no longer necessary.

- Self-controlled oscillators having a high degree of stability are relatively diflicult to construct. The instability is increased when the oscillator is connected to a load which varies. The reason for this increased instability is the effect of the varying load upon the feedback circuit from the plate of the oscillator to the grid of the oscillator. By my invention I eliminate the effect of any varying load in the plate circuit of the self-controlled oscillator upon the feedback between the plate circuit of that oscillator and the grid thereof.

My invention may be more clearly understood by reference to the attached drawing wherein:

Fig. l is a diagram of a self-controlled oscillater having in its output a re-entrant loop circuit;

Fig. 2 is a modification of the circuit shown in Fig, 1.

In Fig. 1 a self-controlled oscillator designated I is connected to two loops 2 and 3 by means of a link coupling 4. The loops 2 and 3 are of a type shown in the patent to Alford No. 2,147,809, and are particularly adaptable to a self-controlled oscillator for generating high frequency currents. The oscillator may be any oscillator of a well known type having. all incidental or stray coupling between the grid and plate neutralized' so as to prevent any internal feedback in the oscillator itself. The feedback circuit of the oscillator comprises a link 4 coupled to the tank or plate circuit 5, the path A and the leads 6 and coil 6a. coupled to the grid circuit 1. Traveling waves entering the loops 2 and 3 will pass around the loops in opposite directions, and due to the transposition 8 will produce voltage nodes at the points 9 which are equi-distant from the connection points of the link coil 4 to the loops. The two halves of the loops are assumed to be identical in all characteristics. At the points 9 is connected a balancing circuit H) which has characteristics substantially identical to those of the plate circuit of the oscillator. If a load H and grid coupling leads and coil 6 are connected symmetrically on the loops 2 and 3 and between the oscillator plate circuit and balancing, circuit connections, there will be no effect upon, the voltage nodes at the points 9, provided that both the load and the grid coupling link have equal impedances. It is apparent, however, that unequal impedances of the load and grid coupling link circuits may be compensated for by use of I well known coupling means, or the loops them-v selves may be used as transformers by changing the positions of the elements coupled thereto;

Fig. 2 is a modification of the circuit shown in Fig. 1 and is more readily adapted to explaining the operation of the stabilizing circuit. Referring tothis figure, l2 represents the oscillator plate circuit and t3. the oscillator grid circuit. The

feedback path comprises leads i4, path A, leads 6 and coil 6a. The loops 2 and 3 are represented as square in form but bear no relationto the, physical shape of the loops themselves, that is,

the loops may be made of any desired shape and compensating means inserted to eliminate any disturbances that arise therefrom. Traveling waves entering the loops 2 and 3 by way of leads [4 will again produce voltage nodes at the points 9. The nodes are maintained at this point as long as the load I I and the grid coupling circuit 6 present equal impedances to the loops 2 and 3, and this condition is especially desirable since it is preferable to keep all energy possible out of the balancing circuit ID to prevent waste of energy in that circuit.

Assuming that the circuit is in an oscillating condition, traveling wave will be sent along the loops 2 and 3, producing nodes at the points 9 and supplying energy to the load II and the grid coupling circuit 6. If, for some reason, the load varies in value from its value during the stable condition, there will be an alteration in the transmission of waves past the points a and a. In the case that part of the waves is transmitted backward toward the oscillator plate circuit and forward toward the balancing circuit, it will be seen that if the distances along the arms A, B and C, D are equal the reflected waves will produce nodes at the points b and b in a manner similar to the way that nodes are produced at the points 9, when the source of waves is the oscillator plate circuit. These nodes will be produced at the points b and 12', however, only when the impedances of the oscillator plate circuit and balancing circuit are identical since unequal impedances would cause unequal attenuations of the reflected'waves passing along the arms A, B and C, D and therefore leave a resultant voltage at the points b and b.

It is readily apparent therefore that any changes in the load II will create neutralizing effects at b and b' that cause no alteration in the feedback energy.

In the preferred form, arm A=arm B=arm C=arm D. However, the important requisite is that the path from a, a by way of arms A and B be equal to the path from a, a to b, b by way of arms C and D. It would be possible to make arm A equal to arm C and arm B equal to arm D, neither of these pairs of arms being equal to a each other; or it would be possible to make arm B equal to arm C and arm A equal to arm D, these pairs of arms also not being equal to each other. Inequalities in the length of the arms B, C and A, D will cause some of the energy from the oscillator plate circuit to be fed to the balancing circuit In, and as stated before the energy going to the balancing circuit would be an undesirable loss.

In the preferred form, the conjugate networks that I have described have dealt particularly with natural lines designed for use with high frequencies. It is possible, however, to make the arms of these networks of impedances or artificial lines.

While I have described particular embodiments of my invention for purposes of illustration, it will be understood that various modifications and adaptations thereof may be made within the spirit of the invention as set forth in the appended claims:

What is claimed is:

1. An oscillator comprising an output circuit, a conjugate bridge network comprising a reentrant loop circuit connected at one point to said output circuit, a balancing circuit connected to said network at a second point, means for connecting a load circuit to said network intermediate said points, and an input circuit for said oscillator connected to said network and electrically remote from said means.

2. An oscillator comprising an output circuit, a conjugate bridge network comprising a reentrant loop circuit connected at one point to said output circuit, a balancing circuit connected to said network at a second point, means for connecting a load circuit to said network intermediate said points, and an input circuit for said oscillator connected to said network intermediate said points and 180 electrically different in distance from said means.

3. An oscillator comprising an output circuit, a conjugate bridge network comprising a reentrant loop circuit connected at one point to said output circuit, a balancing circuit substantially equivalent electrically to said output circuit connected to said network at a second point substantially electrically different in distance from said first point, means for connecting a load circuit to said network intermediate said points and electrically equi-distant therefrom, and an input circuit for said oscillator connected to said network intermediate said points and electrically equi-distant therefrom and 180 electrically different in distance from said means.

4. An oscillator comprising an input circuit and an output circuit, a load circuit, a balancing circuit, a conjugate network comprising a transmission channel having its two ends joined to form a closed loop, connections between said load circuit and a first point of said loop, connections between said input circuit and. a second point of said loop whose electrical distances along the two halves of said loop to said first point differ by 180, connections from said output circuit and said balancing circuit, respectively, to symmetric intermediate points on said loop whereby said load circuit is conjugate to said input circuit.

MELVIN A. ROTE.

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