US1779198A - Harmonic generator system - Google Patents

Description

Oct. 21, 1930. H. o. STORM HARMONIC GENERATOR SYSTEM Filed Jan. 31, 1927 FIE I I N V EN TOR B y Hans 0720 Sform A TTORNE YS Patented Get. 21, 1939 UNITED STATES wares PATENT @FFKIE OF PALO ALTO, CALIFORNIA, ASSIGNOR TO FEDERAL TELEGRAPH OF SAN FRANCISCO, CALIFORNIA, A'CORPOBATION OF CALIFORNIA HARMONIC GENERATOR SYSTEM Application filed January 31, 1927. Serial No.

This invention relates generally to electrical systems for producing oscillatory energy ofhigh frequency, and has special relation to oscillation generators of the harmonic type.

A broad object of the invention is to provide a source of electrical waves of high and constant frequency.

Another object is to prevent, in a harmonic generator, shifts in the frequency of the fundamental wave.

A feature of theinvention is means for modulating, in a simple and effective manner, a harmonic wave produced in a harmonic generator. Y v V In signalling systems it is often necessar' to employ electrical oscillations of high radio frequency and short, wave length, say below 100 meters. lVhile the ordinary vacuum tube oscillator will operate on afundamental frequency of below 100 meters wave length, spe cial precautions must be taken in operating such oscillators in order to maintain the frequency sufficiently constant for signalling purposes. As an alternative, it has been proposed to operate an oscillator in such a manner as to produce a number of harmonics in addition to a fundamental frequency. One of the harmonics of the frequency desired is then picked off by a suitable filter circuit and amplified to the desired signal strength. A system of this kind is shown in the copending application of Frederick A. Kolster No. 232,360, filed May 23, 1925, and entitled Radio transmitting system which application is assigned to the same assignee as this application. Application N 0. 32,360 discloses the novel idea of employingan arc converter to generate a fundamental frequency together with a number of harmonics, in combination with an amplifier for amplifying one of the harmonics of the desired frequency.

A harmonic system possesses the advantage over a simple high frequency oscillator in that no special stabilizing devices are required. An arc converter may be made to produce a constant fundamental frequency of a wave length of say 500 meters, together with harmonic frequencies. Thus a highfrequency'harmonic from an arc converter Will remain at substantially constant frequency because the fundamental frequency of the converter remains constant. In practice it has been found that the stability of the amplifier and of the harmonic generator is much affected by the nature of the coupling between the generator circuit and the input of the amplifier. Unless this coupling is properly designed, the harmonic frequency may not remain constant and sudden surges of current may occur in the amplifier input which may even be sufficient to cause injury to the amplifier tube. It has also been found that only certain means of coupling will deliver suiiicient energy at the harmonic frequency to be of practical value.

Referring to the drawing:

F l is a circuit diagram illustrating a harmon c generator system incorporating the principles of this invention.

Fig. 2 is a circuit diagram showing a modification of the system shown in Fig: 1.

As certain features of this invention arc especially applicable to arc converters. I have illustrated in the drawing an are convertcr which consists of a paii of are elec trodes 10 supplied from a suitable source of current such as a direct current generator 11. The magnetic blowout field for the arc may consist of a magnet 12 which may also serve as a radio frequency choke. The main oscillation circuit for the converter includes an inductance 13 and capacitance 14 which are connected directly across the electrodes 10. The inductance and capacitance are preferably connected in series and are tuned to resonate at the fundamental frequency of the converter. A converter of this type will not only produce a fundan'iental frequency but will also produce a number of harmonic frequencies. To pick off one of these harmonics which is at a desired frequency. there is provided another circuit consisting of inductance 16 and capacitance l7, and which is C011)l(l to the main or fundamental oscillating circuit. For best results it has been found that the inductance 16 and the capacitance 17 should be connected in series and directly across or in due to p connected to two or DEOTQOSOlllfitOI'j c1r-.

i tance and capacitance'16 and 17,

parallel with inductance 13 and capacitance 14L.

As the energy of is relatively slight, it is generally necessary to amplify it to the desired strength. Thus there has'been of amplifier which may comprise a vacuum tube or electron relay 18 havinga grid 19, filamentor electron emission element 20, and plate or anode 21. The input circuit of the amplifier is coupled to one'of the reactive elements of the harmonic circuit, as by means of a conductor 23 providing a connec-.

inductance 16, the amplifier input is induction between the grid 19 and the mid-point between'inductance 16 and the capacitance 17. Anysuitable work circuit may be coupled'to the output of the amplifier.

such as a radio antenna and ground connection, which is coupled to the amplifier former 26.- output has also been shown as locally energized by means of 'the'usual B battery 27 and tlie'frequency to which one of the harmonic circuits is tuned rather than upon th e fre- ,quency of the fundamental circuit. 1 ihis is the tendency of an arc 'converterwhen cuits of difierent resonant frequencies, to

oscillate upon the resonant frequency of that circuit which has the lowest effective resistance. In case the resistances of the fundamental circuit andone or more of the harmonic circuits'are' approximately equahthe fundamental frequency of the arc converter may therefore fluctuate between that of one circuit'and anoher with consequentmomenthrough the induc-. sufficiently tary surges of current heavyin some cases to injure the apparatus 2 make the total resistance fiers may be and in any case to make the operation of the system ragged and irregular. I have found that these sudden surges of current may be prevented by inserting an additional resistance 31 into the harmonic circuit, this resistance 31 being of sufiicient value to of the harmonic circuit definitely higher than that of the fundamental.

It is of course obvious that other amplicoupled to the arc converter for picking off other harmonics.' For example there has been shown a circuit consisting o inductance 32 and capacitance 33 connecte the harmonic frequency shown a conventional type Thus in the drawing there has been shown an ab- SOIPlLlOD device 2-l,

output as by means of transv and minimum limits.

harmonic frequency may be 37 A resistance 34 is also inserted in series with inductance 32 and capacitance 33 for preventing sudden surges of current at this frequency.

In Fig. 2 I have shown a slightly modi- 'fied system which also incorporates a. novel means for modulating the output of the amplifier. In this case instead of conductively coupling the input of the amplifier to the mounted upon a rotor so as to revolve upon EJ/PlVOi] or shaft 43', so that the capacitance the tuning thereof. For'exshown a device having stationary electrodes ll in capacitative relation to movable electrodes 42. 'Electrodes 4L2 arev of this device will'vary between maximum Conductors i l and l5 serve'to connect the, stationary and rotor electrodes across one of the reactive elements of the harmonic circuit, preferably thecondenser 17 As the electrodes 42 are rotated the tuning-of the harmonic circuit is repeatedly varied repeated in the amplifier output. For-coding the output of the amplifier, a key 47. may be inserted in the grid circuit. lVhile the specific form of modulator shown is especially adapted for producing a signal frequency, it is to be understood that the lated with voice frequencies.

I claim: I

1. In a system of the class described, an arc converter tuned to a given fundamental frequency, a circuit coupled tosaid converter and tuned to a harmonic of said fundamental, said circuit including an inductance and capacitance in series, a resistance in series with said circuit, and an amplifier having its input coupled to said inductance whereby energy at said harmonic frequency is amplified.

'2. In a system of the class described, an oscillation generator producing a fundamental frequency and anumber of harmonics, a circuit tuned to one of saidharmonics and coupled to said generator, an amplifier having its input coupled to said circuit for amplifying said harmonic, and means for varying the tuning of said circuit for modulating the output of the amplifier.

3. In a system of the oscillation generator having a fundamental similarly moduv and these variations are p class described, an a frequency and a number of harmonics, a circuit tuned to one of said harmonics and cou pled to the generator, said circuit comprising an inductance and capacitance in series, means for preventing the generator from shiftin its fundamental frequency to the frequency of the harmonic to which said circuit is tuned, said means comprising a resistance inserted in series With said circuit, and an amplifier having its input coupled to said circuit.

In a system of the class described, an scillation generator forming a source of Waves of frequencies corresponding to a harmonic series, a circuit forming a part of the generator and tuned to the fundamental frequnecy of said series, a second circuit tuned to a particular harmonic component of said series and coupled to said generator, said second circuit including an energy absorbing element of such value as to prevent shifting of the frequency of the generator to supply current to said second circuit from a different component of said series, and an output circuit coupled to said second circuit.

5. In a system of the class described, an oscillation generator forming a source of Waves of frequencies corresponding to a harmonic series, a circuit forming a part of the generator and tuned to the fundamental frequency of said series, a second circuit tuned to a particular harmonic component of said series and coupled to said generator, said second circuit including a series resistance of such value as to prevent shifting of the fundamental fre quency of the generator to supply current to said second circuit from a different component of said series, and an output circuit coupled to said second circuit.

6. In a system of the class described, an oscillation generator forming a source of Waves of frequencies corresponding to a harmonic series, a circuit forming a part of the generator and tuned to the fundamental frequency of said series, a second circuit tuned to a particular harmonic component of said series and coupled to said generator, said second circuit including an energy absorbing element of such value as to prevent shifting of the frequency of the generator to supply current to said second circuit from a different component of said series, and a vacuum tube amplifier having its input circuit coupled to said second circuit.

7. In a system of the class described, an oscillation generator producing a Wave of a fundamental frequency and a number of harmonics, a circuit tuned to one of said harmonics and coupled to said generator, an amplifier having its input coupled to said circuit for amplifying said harmonic, and means for varying the impedance of said circuit for modulating the output of said amplifier.

8. A source of oscillations comprising an oscillation generator producing Waves of a my hand.

HANS OTTO STORM.

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