US1908249A - Frequency multiplication system - Google Patents

Description

May 9, 1933. A. HUND FREQUENCY MULTIPLICATION SYSTEM Filec Oct. 5,1926

INVENTOR. /waif TTORNEY 1a BY Patented lVlay 9, 1933 PATEN FFHIE AUGUST HUND, OF BETHESDA, MARYLAND, ASSIGNOR, BY MESNE ASSIGWTB, 1'6 WIRED RADIO, INC, OF NEW YORK, N. '51., CORPORATION 0F DELAWARE FREQUENCY MULTIPLICATIUN QYETM Application filed hotelier e, 139526. Serial He. inane-e.

My invention relates broadly to systems for generating oscillations and more particularly to frequency multiplication circuits.

One of the objects of my invention is to provide a frequency multiplication system and method by which a relatively low frequency impressed voltage may be increased in frequency a plurality of times.

Another object of my invention is to pro vide a system and method for generating relatively high frequency electrical oscillations by the impression of unidirectional current impulses upon an oscillation circuit and controllin the frequency thereof by the timed relation of the current impulses.

A further object of my invention is to provide an oscillation generator circuit in which the frequency may be controlled by successively impressing unidirectional charges upon the oscillation circuit, the charges being derived from an initial source of low frequency current subsequent to its impression upon a rectification circuit.

Still another object of my invention is to provide a circuit system for the production of high frequency oscillations from an initial source of low frequency alternating current where a. form of rectifier is interposed between the initial source and the high frequency oscillation circuit and adjusted to allow the periodic impression of charging current upon said oscillation circuit during selected time intervals separated by noncurrent intervals, whereby oscillations of a frequency dependent upon the rate of impression of the charging current upon said oscillation circuit may be produced.

My invention will be more clearly understood from the following specification by reference to the accompanying drawing in which:

Figure 1 represents graphically the'characteristics of the circuits of the frequency changing system of my invention; Fig. 2 shows a circuit diagram embodying the principles of my invention with characteristic curves of the current which is supplied to the oscillatory circuit and the current in the oscillating circuit; Fig. 3 circuit arrangement embodying the principles oi my invention with an explanatory curve showing the characteristic of the current supplied to the circuit; Fig. 4 shows a modified arrangement of rectifier and .frequency multiplication circuit illustrating the characteristic of the current supplied to the frequency multiplication circuit.

My invention finds particular application in association with piezo electric crystal control circuits for increasing the frequency of oscillations derived from the piezo electric crystal element of relatively large thickness. ln controlling high frequency oscillations by piezo electric crystal elements the piezo electric element is normally very thin and fragile. 'lhe grinding of a crystal to the extreme thinness required in high frequency operation is relatively tedious and difiicult and the possibility of breakage and the labor necessary for grinding of the crystal involve relatively large expense. Besides, it' is more difiicult to make thin crystals oscillate. By my invention 1 provide a circuit arrangement which may be associated with a piezo electric crystal oscillator of relatively low frequency for multiplying the frequency thereof within limits to any required frequency. My invention finds application in other circuit arrangements where it is necessary to increase the freshows a further quency of a relatively low frequency alternating current to a higher frequency.

Referring to the drawing in detail, Fig. 2 shows circuits arranged for operation in accordance with my invention and curves indicating the current in said circuits. A source of alternating potential E is shown having one side connected to a rectifier B and the other side to an oscillatory circuit comprising inductance L and capacity uency o The rectifier Bis connected intermediate the source of alternatinfiwtential E and the oscillato circuit The natural freoscillation of the circuit'LC is etermined by the values of the inductance L and the capacity C, and is substantially equal to It is well known that if the capacity1 C is" char 6. and the source of charge is t en remove capacity C will discharge and recharge repeatedly through the inductance L at the natural frequency of oscillation of circuit L0. The current so set up in LG is indicated b reference character I. The current I wi have a lower value for each succeeding cycle and will die out after a period of time depending on the losses in the circuit.

In order to maintain oscillations in the circuit LC and in accordance with my invention, I provide a rectifier Bin series with the source of alternating potential E and select values for L, C, and the frequency and voltage of the supply source E so that the frequency of the current I is substantially a multiple of the frequency of source E.. I arrange the rectifier R so that it will ofier ractically infinite impedance to a current f, until a redetermined value of voltage is impresse d across the rectifier. When the voltage of E exceeds this predetermined value the resistance of the rectifier changes and a current I flows from the source E to the circuit LC. When the voltage across the rectifier R falls below the said predetermined value the rectifier again ofiers practically infinite impedance to current I. and also when the voltage of E is of opposite polarity. It is readily seen, therefore, that current flows into the circuit LC from the source E onl when the voltage of E exceeds a pre etermined value in one direction. This results in the circuit LC receiving a series of current impulses L of predetermined duration at the frequency of the source E During the intervals when no im ulses are bein received b the circuit L said circuit is cc to oscillate at its natural frequency. I arrange the circuit LC so that each impfiulse I Wlll be substantially}? phase with t e current I in the circuit In order to show the relations between the various factors as illustrated in the drawing I have chosen the following additional f= frequency of the alternating potential source E.,.

. F=fre3uency of oscillation of circuit LC m-m tiplication factor T.,=cyclic period of source E,

T=cyclic period of current I .LC from which it follows thatt==duration o'f an impulse of current I... The multiplication factor m represents the relation between the frequency of source E,

and the uency of oscillation of circuit The cyclic period .is the reciprocal of the frequency so therefore and I control the duration t of the impulses of current L so that t is equal to one-half cycle of current I, hence (4) T=2t By substituting Equations 2 and 3 in Equation (1) I obtain and substituting t for T as in Equation 4:,

Iobtain 1 m gf vor (7) T.,=2mt

I I s T.,t=(2/m1)t Now referring to Fig. 1 of the drawing,

I have schematically illustrated the relations between the currents I and I for four conditions of operation of the circuits of my mventlon.

The curves in bracket 20 show the relation between L, and I when the multiplication factor m equals 1. In this case the freqduencies of the source E and of the circuit C are ual.

In brac et 21 I have illustrated the current relations when m uals 2. Under this condition of operation t e frequency of the circuit LC is twice the frequency of source E and the interval between im ulses I is 3t, which is obtained by substltutin the value of 2 for m in Equation (8). %imilarly in bracket 22 illustrating the current relations when m equals 3, F equals 3 and the interval between impulses is 5t; an similarly in bracket 23 I have illustrated the current relations when m equals 4; then F equ7als 4f andthe interval between impulses is t It is evident, therefore, from the foregoing description and equations that if the circuit LC is so proportloned as to have a natural frequency which is substantially a multiple of the frequency of the source E the frequency of said source will control the frequency of the circuit LG by means of the recurring impulses I which are impressed on the circuit LC, thatis, if the natural frequency of the circuit'LC is very nearly but not exactly a multiple of the frequency of the source E the recurring impulses I which supply the ener y to maintain oscillations in the circuit LL, will maintain the frequency of LC at an exact multiple of the frequency of the source E...

Such properly timed current impulses I can be readily obtained from a source of alternating potential, as previously described, by using a selected portion of-each cycle of said alternating otential. This result can be accomplished by the use of many types of rectifiers such as glow discharge, thermionic, mercury arc, dry contact rectifiers, etc.

When the rectifier R is a glow discharge tube as illustrated at 14 in Fig. 3, the frequency multiplication is accom lished in a very simple manner because t e voltage across the glow discharge tube must reach a certain value before the tube will pass current. For instance, in Fig. 3 I have illustrated a glow discharge tube 14 containing a suitable gas and the electrodes 10 and 12. Suppose the ignition voltage of such a rectifier is 80 volts as indicated in Fig. 3, then no current can flow for voltages less than 80 volts and the current passing through the tube 14 is limited to the current produced by voltages in excess of 80 volts. By selecting the proper voltage for the alternating potential E5, theduration t of the impulses I may be controlled.

In Fig. 4 of the drawing, I have illustrated a rectifier comprising an ordinary thermionic two element tube 15 having a hot cathode or filament 16 and an anode or plate 17. The source of potential 18 supplies the energy 'to heat the filament 16. The source of potential 19 opposes the voltage from the source E and until the voltage of E becomes greater than the voltage of source 19 no current flows into the circuit LG. I use the source of potential 19 in connection with rcctifiers which do not have a definite ignition voltage such as the glow discharge tube illustrated in Fig. 3.

' It is believed that the principles of my invention will be clear, and while I have described my invention in its preferred embodiments, I desire that it be understood that modifications may be made and that no limitations upon my invention are intended other than are imposed by the scope of the appended claims. Y

WhatI claim as new and desire to secure by Letters Patent of the United States is as follows:

1. In a frequency multiplication system a source of alternating current, a circuit adapted to oscillate at a frequency which is a multiple of the fre uency of said source, a gaseous discharge tu e interposed between said source and said circuit, means for fixing a critical point of potential above which unidirectional current impulses may be transferred from said source to said circuit through said gaseous discharge tube and below which critical point of potential transfer of energy is prevented, and means for limiting the duration of energy transfer to time intervals in which the current from the alternatin source and the current of the multiple requency are in phase with one another.

2. In a frequency multiplication system a resonant circuit adapted to oscillate at a desired frequency, a source of energy, a glow discharge tube connected between said source of energy and said circuit and controlling said energy to produce impulses for recurrently energizing said circuit at a frequency which is an aliquot part of the frequency of sald resonant circult, said glow discharge tube being adapted to pass said energy by lonization at predetermlned potentials only.

.3. In a frequency multiplication system a source of energy suitable for periodic shock excitation, a circuit adapted to oscillate at a desired frequency, said frequency being a harmonic of the periodicity of said shock excitation, a gaseous discharge tube interposed between said source and said circuit, means for fixing a critical point of potential above which unidirectional current impulses may be transferred from said source to said circuit through said gaseous discharge tube and below which critical point of potential transfer of energy is prevented, and means for limiting the duration of energy transfer to time intervals in any one of which not more than a half cycle of oscillations of said circuit is comprehended.

In testimony whereof I afiix my signature.

' AUGUST HUND.

Images