US2216011A - Low damped oscillation circuit for ultra short waves - Google Patents

Description

Sept. 24, 1940. H. E. HOLLMANN 2,216,011

LOW DAMPED OSCILLATION CIRCUIT FOR ULTRA SHORT WAVES Filed Oct. 8, 1938 wsmumm INVENTOR. HANS ERICH HOLLMANN BY y mm/ ATTORNEY.

Patented Sept. 24, 1940 UNITED STATES PATENT OFFICE LOW DAMPED OSGILLATION CIRCUIT FOR ULTRA SHORT WAVES tion of Germany Application October 8, 1938, Serial No. 233,911

In Germany September 17, 1937 3 Claims.

In my parent application, Serial No. 214,435, filed June 18, 1938, there is disclosed a lowdamped oscillatory or tuning circuit for ultrashort waves which comprises two parallel metal discs which are disposed upon an axial conductor a certain distance apart. This circuit, which is a further development of the circuit comprising two hemispheres facing each other upon a common shaft or spindle, in addition to the advantage inhering in a very high natural period, offers appreciable mechanical advantages, especially in so far as mechanical stiffness or rigidity as well as insensitiveness to shocks or vibrations are concerned.

The object of the present invention is to provide a low-damped oscillation circuit which, in mechanical regard, possesses the advantages associated with the disc circuit disclosed in my parent copending application, supra, though in electrical regard it may be conceived to be a sphere circuit (to which the above-mentioned oscillatory circuit known in the prior art is to be regarded), and which may therefore be used also for stabilization of waves of longer length.

According to the invention, there is disposed between the plates of the disc circuit built as disclosed in the parent copending application, on the outer circumference thereof, a ring consisting of a sort of material having a dielectric constant greater than unity.

Fig. 1 illustrates the basic principle underlying the construction of such an oscillatory circuit. F and F denote the two discs mounted upon a spindle it between which, on the outer circumference thereof, is a ring Q consisting of a material possessing a high (ii-electric constant. This ring concentrates the capacity of the circuit upon the outer disc zones so that the circuit, from the electric angle, is similar in its operation to the sphere circuit known in the prior art. However, from the mechanical viewpoint the arrangement here disclosed offers appreciable advantages over what is known in the earlier art. For instance, the stability and ruggedness of the surfaces F d and F" may be substantially raised by simple means over the stability of hemispheres which, as will be remembered, must moreover be fitted with additional capacity surfaces. Moreover, there are additional chances for a continuous or steady change of the natural wave-length of the circuit, that is, good tuning.

As in the arrangements known in the art, the tuning is accomplishable by variation of the disc spacing, there being an air-gap a between the ring Q and one of the discs which represents a series capacity in reference to the capacity constituted by the ring Q. Inasmuch as this chance to tune is but hard to be utilized because of the outer circuit elements associated with the circuit, for instance, tube, etc., the tuning preferably is effected by a shift of the entire ring Q with the result that parts thereof project from the discs or else by a disposition as shown in Fig. 2. As can be seen by referring to Fig. 2, the ring Q is split, and part S is either withdrawable from the rest of the ring or else it is arranged so as to be screwed out. This latter arrangement is shown in Fig. 2, where A is the axis of rotation of part S. By adjustment of the screw V, part S may be turned more or less far into the space between the two discs of the oscillatory circuit so that the marginal capacity between the discs is altered.

The ring Q which is provided according to the invention may consist, for instance, of a ceramic possessing a high dielectric constant. What is essential is that the material be free from losses in order that the freedom from damping insured by the remainder of the circuit may not be offset by losses in the capacity ring again. However, it is known in the art that materials are available which combine a high dielectric constant with a practically negligible low loss factor so that the circuit turns out to be extremely free from damping. 1

The connection of the circuit here disclosed with other circuit elements, vacuum tubes, etc., may be effected in the very same way as disclosed in the parent copending application. Thus, in the present instance, it is possible to subdivide the inner conductor in order that the feed potential of the vacuum tubes may be applied directly by way of the discs. A preferred exemplified embodiment of this last-named idea, as set forth in the parent copending application, is that the central conductor of the circuit could consist simply of central expansions or reinforcements of the opposite plates. Between the two discs there could also be interposed a radial median sheet. The latter most suitably is built up of two laminations which are forced together, with interposition of a thin dielectric, and to these laminations the cathode terminals of the tube are connected. Inasmuch as it is rather difficult to ac commodate one or more oscillators between the 'two discs, though this is particularly easy in the case of sphere circuits, it will be necessary for the median or central laminations to project beyond the discs so that one or more oscillator tubes may be fitted outside upon the disc circuit. In this instance, it is necessary to divide the insulating capacity ring into two parts in order that the middle laminations may be passed through the same. It is, finally also feasible to utilize the extension of the oscillation circuit axis for the antenna or to insert the circuit to act as a bridge in a Lecher wire circuit, and this may be efiected either conductively or capacitively.

What is claimed is:

1. A low-loss oscillatory circuit comprising a pair of discs having relatively large flat conducting surfaces spaced parallel to one another and substantiall coextensive, a shaft directly connecting said discs together, said shaft forming an inductance which, together with the capacity between said discs, forms a resonant circuit, there being disposed between said discs and around the marginal area only of said discs a ceramic material having a high dielectric constant, and means for varying the position of a portion of said dielectric material with respect to said discs for varying the tuning of the circuit.

2. A low-loss oscillatory circuit comprising a pair of discs having relatively large flat conducting surfaces spaced parallel to one another, a shaft directly connecting said discs together, said shaft forming an inductance which, together with the capacity between said discs, forms a resonant circuit, there being disposed between said discs a ring of ceramic material having low losses and igh dielectric constant, and means for varying the position of a portion of said dielectric material with respect to said discs for varying the tuning of the circuit, said ring having a stationary portion and a portion which is movable with respect to said stationary portion, whereby the capacity between said discs can be changed to vary the tuning of said oscillatory circuit.

3. An oscillatory circuit of low loss comprising a pair of suitably spaced flat metal discs and a conductor coupling said discs together at their centers, and a relatively narrow ring of insulating material placed between said discs around the edge of at least one of said discs for concentrating the capacity of said oscillatory circuit near the edges of said discs, said ring having low loss and a high dielectric constant, at least a portion of said ring being shiftable in position between said discs for changing the capacity between said discs with a consequent change in the tuning of said circuit.

HANS ERICH HOLLMANN.

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