Patent GB-216132-A (GB)
Title: A system for repeatedly raising the frequency of electric currents
IPC: H03B19/10
Filed: 1924-05-14
Abstract: 216,132. Western Electric Co., Ltd., (Assignees of Affel, H. A.). May 15, 1923, [Convention date]. Addition to 216,108. Harmonics, producing and utilizing.-Alternating current of a fundamental frequency is passed through a wave-distorting device (for example, a triode valve or a rectifier) and an harmonic selected from the output side is passed back to the input side of the wave-distorter, so as to produce a higher harmonic, the action being repeated until a sufficiently high frequency is obtained. As shown in Fig. 1, an alternator S supplies the fundamental frequency f through a transformer 13 to the grid circuit of a wave-distorting valve VI. The output transformer 17 has a secondary coil 16 connected through two or more branched circuits 18, 19 to a primary coil 20 of another transformer 22. the circuits being tuned to harmonic frequencies. The energy is thus transferred to a second similar valve V<2>, coupled through transformers and tuned circuits 26, 27 to the input side of the valve V1. In one method of using the apparatus, the frequency f applied to the valve V1 produces a component of frequency 2f which passes through the resonant circuit 18 to the valve V2. A frequency 4f produced in the output circuit of this valve is selected by the tuned circuit 26 and applied to the valve VI. The frequency 8f is selected by the circuit 19 and transferred to valve V2, causing a frequency 16f in the, circuit 27. The output circuit O thus carries a mixture of all these harmonics, any one of which may be selected. The modulating action of the distorting valves V<1>, V<2> also causes other harmonics, of the sum and difference frequencies, to be produced. In a modification shown in Fig. 2, the fundamental frequency f is applied in phase opposition to the grids of two balanced valves V1, V2. The output coil 34 is connected in the common branch of the plate, circuits, so that it is not affected by the fundamental or by odd harmonics, only the even harmonics being transferred to the coupled coils 36, 37. The frequency 2f is selected by the tuned circuit 38 and applied to the valve input transformer. The frequencies 4f, 8f are similarly selected by tuned circuits 39, 40 and re-applied to the grid circuits. A mixture of even harmonics is thus applied to the valve V3, which may be adjusted to amplify these currents, or to modulate them with one another, so as to produce sum and difference frequencies. The valves do not tend to oscillate, as any frequency applied on its input side is: balanced out in the output circuit. In another modification, the input frequency is supplied by the vibration of a tuning fork in an air gap of the input transformer core; the vibration being sustained by the magnetic action of a core surrounded by coils connected between the valve plates and the coil 34. Alternatively, the fundamental frequency may be produced by a tuning fork vibrated by an electromagnet which has its coils connected in series with a battery and with a microphone or current interrupter actuated by the fork. Any suitable rectifiers may replace the valves V1, V2, Fig. 2.