US1851408A - Frequency multiplier circuit - Google Patents

Description

March 29, 1932. w. RUNGE' 1,851,408

I FREQUENCY MULTIPLIER CIRCUIT Filed Oct. 28, 1929 INVENTOR wlmzam mums y ,W ATTORNEY Patented Mar. 29, 1932 UNirED STATES PATENT OFFICE v WILHELM RUNGE, F BERLIN, GERMANY, ASSIGNOR TO TELEFUNKEN GESELLSCHAF'I' FUR DBAHTLOSE TELEGRAPHIE M. B. 11., OF BERLIN, GERMANY, A CORPORATION OE GERMANY FREQUENCY MULTIPLIER CIRCUIT Application filed October 28, 1929, Serial No. 402,961 and in Germany November 10," 1928.

There is a large field in electricity where it is desirable to distort sinuous current waves and to filter out therefrom high harmonics or overtones in order to thus derive high frequencies from the original low frequency,

that is to say, to multiply the frequency. for such frequency multiplication work, thermionic tubes are employed, then it is usual to employ for the distortion either the lower or the upper knee in the anode-current characteristic of the tube. Hence, what is necessary is to provide the tube with such a biasing potential and to feed it with such a high unlwave alternating current potential that one of the knees in the plate characteristic will be passed over periodically.

In this manner it is possible to produce rather high overtones. The disadvantage, however, is that while a very high singlewave alternating current potential is required therefor, the amplitude of the ensuing harmonics is comparatively low, so that frequency after each multiplication amplification of the newly obtained overtone is necessary until its amplitude will be sulficiently high for another multiplication.

It is therefore one of the objects of the present invention to obviate the above mentioned drawbacks by that distortion of the single 3 wave potential is brought about in the grid circuit of the tube, while working at a point of maximum slope of the plate characteristic. Since the grid-current characteristic in the neighborhood of zero grid potential presents a curvature which is marked comparatively with the curvatures of the plate characteristics, it is possible to insure appreciable distortions even with small amplitudes. Since, furthermore, the tube itself acts as an amplifier for the harmonic newly produced in the grid circuit, it follows that the amplitude ratio of the new harmonic and that of the fundamental wave fed to the grid is far more favorable than what would be obtained by 5 frequency multiplication at the plate knee.

As a result it is feasible, even afterthe production of high overtones, to pass to the next multlplicationstage withoutit being necessary to submit the newly formed overtone to an amplification. Inasmuch as only low f amplitudes are required, the wholeamplification can be carried out by means of a minimum of tube and other working equipment.

Other objects and advantages of the inven tion will become apparentfrom a reading of the appended detail discussion in connection ,with the drawings in which z- Figure 1 illustrates a'preferred circuitarrangement of myinventionyand,

Figure 2 illustrates-a graph useful in describing the action of said circuit.

Distortion in the grid circuit may be effecteld, for instance, in accordance withFigure The alternating current potential 02 is fed to an oscillation circuit which by way of the audion condenser C is associated with the grid of a tube being connected with the filament by way of the resistance R. The plate lead contains an oscillation circuit being tuned to the higher harmonic to be ob-' ta1ned.- In the oscillation circuit associated with the grid'end of the tube a sinuousalternating current potential is produced, the latter being supplied to the grid by way of condenser C. As soon as the grid potential assumes positive instantaneous values, a grid current starts to flow, and this results in a negative charge on the grid, provided the 80 grid (leak) resistances Rwis chosen sufiiciently high and the condenser C adequately" lowin value. r In Figure 2 curve 1 shows the sinuous potential arising in the grid oscillation circuit. Curve 2 shows the potential supplementary arising at the grid owing to the production of grid current; After the first quarter-period the grid has been charged up negatively practically to the same degree as corresponds to grid of'the tube.

the dischargecurve of a condenser by Way of a resistance. ,7 Upon the beginning ofrthe first quarter of the following cycle a grid current impulse is setup again as positive grid potential is supplied, and the process of the preceding period is repeated.

This shape of the supplementary grid potential is illustrated'in curve 2. It will be seen that apart from the sinuous potential Wave 1, there is a distorted potential 2 at the Both potentials are amplified by the controlling action of the grid potential'upon the plate current, and hence a higher 'harmonic' which is contained in curve 2and having appreciable energy can be derived from the plate circuit.

In order'to obtain the effect as hereinbefore described,-it is necessary that condenser C and resist-ance'R should be-so chosen that inside the three quarter period of the .fre-

quen'cy to be multiplied, the grid charge has a chance. to leak off to an appreciable extent. To insure this, essentially low capacity values are required for condenser C. However,

'ing an electron discharge device having a since alsothe grid-filament capacity of the tubebecomes charged up and must be caused denser connected between said resistance and said input circuit in'series With the grid and I said tuned input circuit the values of said condenser and resistance being chosen so that for substantially the positive quarter of a cycle ofinput energy the grid of said device is subjected to approximately an equivalent negative biasing potential and for the remaining three-quarters of the input cycle the charge on the grid leaks off to a negli-' gible value. n

. v WILHELM HUNGE- to flow off by Way of the resistance R, it is recommendable especially'for the multiplication of high fund-amentalwaves to'utiliz'e' tubes exhibiting low grid-cathode capacity.

Claims: V p 1. A frequency multiplier circuit compristuned input and a tuned outputcircuiteach tuned to different frequencies, a condenser connected between said tuned input circuit and the grid of said triode and a resistance shunted across said condenser and said tuned inputcircuit-the values of said condenser and resistance being chosen so that for substantially the positive quarter of a cycle of input energy the grid of said device is subjected to approximately an equivalent negative biasing potential and for the remaining three quarters of the input cycle the charge on the grid leaks off to a negligible value. a

2. In a frequency changer circuit an electrondischarge device having input and output circuits the output circuit being tuned to a 'cdiifer'ent frequency than thatof energy applied to the input circuit, a resistancein p'arallelwith said input circuit and iconiao

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