US2156056A - Method of producing carrier frequencies - Google Patents

Description

April 25, 1939. HORNUNG 2,156,056

METHOD OF PRODUCING CARRIER FREQUENCIES Filed July 8, 1936 Patented Apr. 25, 1939 METHOD OF PRODUCING CARRIER FREQUENCIES Heinrich Hornung,

. assignor to 0. Lorenz Berlin-Tempelhof, Germany,

Aktiengesellschaft, Berlin-Tempelhof (Germany), Lorenzweg Application July 8,

In Germany 1936, Serial No. 89,682

July 1!, 1935 3 Claims. (Cl. 175-415) In order to produce an electric carrier frequency two frequencies may be caused to interfere with each other so as to generate a so-called beat frequency, or a' frequency may be modulated with another and either the lower side band or the upper may be used as the carrier. In the latter method the frequency generator whose frequency is modulated is controlled mechanically, as by a quartz, for example, 'whilst the frequency generator whose frequency serves for the modulation has no such mechanical control. The frequency of this generator on the one hand is variable while on the other hand it is as far as possible maintained constant byadditional means, such as oscillatory circuits independent oftemperature, or by arranging casings dependent upon temperature, oralso by keeping constant the anode voltage in the case of indirect heating, etc.

The invention has for its object to obviate frequency variations which are due to variations of temperature. In accordance with the invention this problem can be solved by so choosing the temperature coeflicients of the frequency generators, that is, the temperature coeflicients determining the frequency, as to compensate for frequency variations caused by differences of temperature. In' the beat method the temperature coeflicients must be of the same sign and the frequency variations must be of the same magnitude. In the modulation method the temperature coefficients must be of the same magnitude but of different sign it the upper side band is used. If, however, the lower side band is used then the temperature coefficients must be equal to one another in magnitude and sign. Frequency variations can thus be avoided in a simple manner even if the temperature differences are great for the following reasons:

If f denotes the desired frequency, h the frequency of the first generator, I: that of the second 0 generator then in the case of the beat method there is the relation 1 f1+ Afr) 12+ Ah) generator, t the temperature, and if a, p are the temparture coeflicients, then the j=f (1 -at) +fv 1 F relation is valid if the upper side band is used as the carrier.

If the frequency is required to be constant at all temperatures then f nt and fvpt must cancel each other.

When using the lower side band the relation is as follows:

quency variations. These frequency determining elements of the oscillating circuits may then be subjected to temperature variations without providing any means for the temperature constant.

the purpose of maintaining The condition for an unobjectionable functioning of this'arrangement, however, necessarily requires the selection of the temperature coefiicient in that the frequency variations of such a manner both oscillators are of equal magnitude, and that the frequency determining elements of both oscillators present at any instant the same temperature.

From the two frequencies generated by said oscillators, a third desired freque ncy may be derived according to different methods, viz. as a difference between the two frequencies, as the sum of these frequencies or as a modulation product from one of these frequencies and another frequency, whereby either the upper or the lower side frequency is utilized.

In order to effect the novel method the temperature coeificients are regulated with the aid of certain means.

For instance, tuning elements variable by bimetallic arrangements, or condensers with regulable temperature coefiicient are suitable for this purpose.

Such condensers have two metallic coatings opposite each other and a dielectric which for example is a part a positive and coefficient.

disc having in in part a negative temperature According to whether more of the dielectric having the one temperature coefficient or more of the material having the other temperature coemcient is turned into the space between the condenser coatings a temperature coeflicient will be obtained which is more sense or the other.

or less in one The two oscillation generators of this construction are subjected to the same temperature differences, that is posed in the same room in order t to say, are dishat in the event of temperature variations both generators shall be influenced by the same variations of temperature.

Figs. 1 and 2 show, respectively, a side elevation and a vertical cross-section of embodiments of the invention. Reference numerals I and 2 indicate the plates of a condenser between which a disc 3 of dielectric material is rotatably arranged. The disc 3 consists of two different dielectric materials which present opposite temperature co- 7 eflicients. The portion 4 may for instance consist of a ceramic material known asCondensa N which presents a negative temperature c0- efllcient, while the portion 5 may consist of a ceramic material known as Tempa S and which has a positive temperature coeiiicient. The temperature coemcient of the dielectric is defined by the following formula:

in which 1 denotes the dielectric constant and d6 indicates the change of the dielectric constant in the dielectric with positive temperature coeflicient is extended within the space between the condenser plates, the more positive the temperature coefficient of the condenser is made. In the reversed sense, the temperature coefllcient of the condenser gets more negative, the more the dielectric having a negative temperature coeflicient is prevailing within the space between the condenser plates.

The invention allows of employing simple 10 transmission arrangements. All that is necessary to such end is that the two oscillation generators have the stated properties.

What is claimed is:

l. A condenser'comprising two metallic coat- 5 ings and a plural part dielectric means movable therebetween to different extents to adjust the temperature coeificient of said-condenser, said parts having different temperature coefilcients.

2. A condenser according to claim 1 wherein 2" said dielectric means comprises a rotatably mounted disc having in part a positive and in part a negative temperature coefficient.

3. A condenser comprising two metallic coatings and a dielectric having a part of positive 25 temperature coeflicient and a part of negative temperature coeflicient, said dielectric being adjustably positioned so that the proportion of positive to negative temperature coefllcient material between said coatings may be varied to give an the condenser a desired temperature coeflicient.

HEINRICH HORNUNG.

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