US2101137A - Wave modulation - Google Patents

Description

Dec. 7, K. FRITZ WAVE MODULATION I Fild Jan. 8, 1956 modulator- Modulaior' I M; i r 'l I l I h i l l I l l SOURCE OF S/G/VALL/NG m n 5 FMODULAT5E I INSULATOR INSULATOR 4/7/- M J INVENTOR KARL FRITZ M av a ATTO R N EY Patented Dec. 7, 1937 UNITED STATES PATENT OFFHCE WAVE MODULATION Germany Application January 8, 1936, Serial No. 58,066 In Germany February 25, 1935 v p 2 Claims. This invention is concerned with an arrangement to modulate electromagneticwaves or oscil-. lations which operates in such away that the mentally, by a non-reactive resistance or prefer-.

ably an impedance whose value varies as a function of the modulation process. If the said impedance is of an infinitely large value, it will exercise no influence at all upon the energy transfer, and the oscillations will reach the radiator in undiminished form. If the impedance is reduced, then the characteristic impedance of the transmission line at the place where the modulation device is mounted, will be altered unsteadily by great amounts, and this causes, in accordance with known laws, a partial reflection of the oscillatory energy. As a result, much of the energy is used up and only part of the oscillations reach the radiator. It is also feasible to produce this modulation by reflection about mean or average impedance values if the modulation impedance is set to a definite static value, and this value then increased and decreased above .and below the said definite means static value. It has also been shown in the prior application that it is possible, by the ways and means disclosed, to insure energy distribution between two consumers or radiators, the transmitter then operating with adjustable orregulable power, one of the consumers or loads being fed with energy which is not allowed to be passed to the other consumer. The two consumers may, for instance, consist of two antennae with different directions of radiation or dissimilar polarity. Control of energy is effected by a pair of modulation means co-ordinated to each radiator and worked in phase opposition (push-pull). The signals issuing from the two radiators, as will thus be seen, differ only by a phase displacement angle of 180 degrees, while otherwise they are perfectly identical.

Now, according to the present invention, ways and means are disclosed whereby two or more radiators fed from one and the same wave generator are caused to radiate different signals which are totally independent of one another. This is accomplished by co-ordinating a modulator. with each radiator. The position'of the modulatorin the line, e. g. its distance from the radiator and wave oscillator, is so chosen that it will act 'upon only the passage of oscillatory energy from the generator to the radiator with which it is co-ordinated, and will not react upon the other radiators.

The idea underlying the invention will be explained in more detail below by reference to the annexed drawing, in which the Figures 1 and 2 illustrate transmitters with two radiators and separate modulators for each radiator. Referring to the drawing, S designates a transmitter which will be assumed to generate an ultra-short wave (decimeter wave). This wave is carried over an energy feed lead or dcwnlead E consisting, say,

of a parallel-wire system, to two radiators A1, A2. Modulation is to be effected by two devices M1, M2 which may assume any of the forms described in the application referred to above, such as condensers comprising vibratory electrodes, discharge paths in high vacua or in rare-gas atmospheres, etc. As has been ascertained from practical experiments, it is possible to find such values for the distances 0., 1), between the wave generator and the radiators and modulation devices, respectively, that the modulator means M1 will exercise a control action only upon the energy flow to the radiator A1, while producing no effect upon the feed of the radiator A2. The same thing applies similarly to the modulator M2. The explanation for this behavior probably is this, that the two modulators have such a relative position that they form a nodal point only for the refiux of energy. The result of this circumstance is that the two modulator devices are perfectly uncoupled or neutralized in reference to the radiator that does not respectively belong to them. It will be understood that in a similar Way also three or more radiators could be operated by a corresponding number of modulation means.

Inasmuch as the position of the modulators upon the energy feed lead is associated with the length of the working wave, there results the necessity to shift the position of the modulators whenever there is a change in wave-length. In order to facilitate this manipulation, it is preferable to establish coupling by positively acting means (inter-locking) between the tuning means C of the wave generator S and the means for adjusting the modulating devices along the lines. This may be accomplished, for instance, as shown 7 and the same Wave.

in Fig. 2 by connecting the control shaft of C with a gear 8 driven by a rack It, which also shifts the modulators M1, M2 along the lines. I may use any other suitable gearing. However, the same problem is solvable by still simpler Ways and means by changing not only the geometric, but also the electric position of the mod ulation means. As has been indicated in the parent patent application it is possible to insert variable capacities along the feed lead or down-- lead, or to bridge the latter by capacities or inductances, so that the electrically active length of the lead section thus affected will differ from the geometric position. It is evident that the setting of a variable condenser is more easily accomplishable and capable of being coupled or interlockedrwith the adjustment of the transmitter than a geometric shift of the modulator.

The object of the application is of considerable practical value in all such instances Where it is necessary to send several communications on one An instance that may be cited here is the formation of a guide-ray or beam. obtained by superposing two dissimilarly quency. 7

What is claimed is: 1. In a signalling system a tunable oscillation 7 generator, a plurality of radiators, a separate ing a, common portion and two branches connecting said source of oscillations to said radiators, and separate modulating means which may be actuated in accordance with signals shunting the branch portions of said feeder system, said separate modulating means shunting said branch portions of said feeder system being located at points; on: the respective. 'branchl'circuitsz such that operation of ones of, said modulating; means has noeifect on the energyin the branch circuit to which the other modulating means is; connected. V

' FRITZ.

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