US2009069A - Oscillation generation - Google Patents

Description

July 23, 1935. PRAY 2,009,069

OSGILLATION GENERATION Filed Oct. 15, 1932 ilk 'lllll &

INVENTOR- GEORG EMERSON PRAY BY i ATTORNEY- {as described more fully Patented July 23, 1935 UNITED STATES 2,009,069 OSCILLATION GENERATION George Emerson Pray,

to Radio Corporation tion of Delaware Oceanport, N. J.', assignor of America, a corpora- Application October 15, 1932, Serial No. 637,925

2 Claims. (01. 250-36 This invention relates to oscillation generators having long transmission lines for frequency control purposes. a

Long transmission lines, a plurality of half wave lengths long at some desired operating frequency, have proven exceedingly useful for the stabilization and frequency control of electron discharge device oscillators. In one form of system, wherein long lines are used for frequency control, and in the United States patent of J. L. Finch and J. W. Conklin, No. 1,945,545, granted February 6, 1934, a long line is connected between input and output circuits of anelectron discharge device. One or more of these circuits are roughly tuned to a desired operating frequency and to insure feed back solely over the frequency controlling line rather than through tube capacities, a further circuit such as a screen grid circuit is provided. Consequently, by making the line a plurality of half wave lengths long at some desired operating frequency, the device is caused to oscillate at a constant frequency corresponding to the number of half wave lengths contained in the line. To prevent reflection on the line, as described more fully in the patent referred to, it is terminated by an impedance equal in value to its surge impedance.

However, in the event that the terminating surge impedance is not accurately matched to the line, reflections will be set up with concomitant undesired radiation. Moreover, if the line is subject to high losses due to its location and/or length, attenuation will be high thereby limiting the length of the line, for a given amount of energy feed back, and hence limiting its frequency stabilizing action. To overcome these defects is the principal object of my present invention and to do so I provide a long line feed back system having a plurality of parallelly arranged conductors or lines of equal length. By placing the feed back conductors parallel and close together, and by exciting them out of phase so that the voltages at corresponding adjacent points in the lines are out of phase at any instant, practically no undesirable radiation will take place. Moreover, since two lines are used, twice as much energy will be delivered to the input circuit as a result of which longer lines may be used having the added advantage of greater frequency stability.

My present invention is more fully described in connection with the accompanying drawing wherein the long line frequency controlled oscillator of my present invention is illustrated in wiring diagram form and incorporated in a high frequency radio transmitter.

Referring to the drawing, electron discharge device oscillator 2 is provided with an input circuit l havinginductance and capacity connected between the control electrode 6 and cathode 8 of vacuum tube 2. Between the anode i0 and cathode 8 there is connected an output circuit i2 also having inductance and capacity. Either circuit d or l2, and preferably both, are adjusted so as to be resonant at approximately a desired operating frequency.

To prevent interelectrode feed back from anode it to control electrode 6,'and to insure feed back solely over the accurate frequency controlling lines 30, 32 a screen grid circuit comprising screen grid i d and radio frequency by-passing condenser i5 is provided. At the higher frequencies, in the event that the lead to the screen grid M has appreciable inductance, condenser itv should be chosen of such a value as to series resonate therewith so as to maintain the screen grid substantially at ground potential. The screen grid is suitably polarized by the action of voltage dropping resistor !8 connected to the plate voltage lead 26, energized from source 22 through resistor 24.

To prevent the flow of high frequency current through source 22, a choke 26 is provided, and, to prevent short circuiting of the plate potential source 22, the output circuit 12 is blocked off therefrom by means of radio frequency by-passing condenser 28.

In accordance with my present invention, two long transmission lines 30, 32 of equal length, and

a plurality of half wave lengths long at a desired operating frequency are coupled between the input circuit t and the output circuit i2 for feeding back energy from the output circuit IE to the input circuit 4 and for frequency stabilizing oscillations generated by device 2 of a frequency corresponding to the lengths of the lines. The input ends of the lines may be inductively coupled to, but are preferably tapped. on to coil 84 of output circuit H on opposite sides of grounding connection 36 whereby voltages applied to the lines 38, 4

32 from coil 34 will be of opposite instantaneous polarity. The lines 30, 32 should be made concentric or placed relatively close together so that radiation therefrom will be self cancelling.

The output ends of the lines may also be inductively coupled to the inductance 40 of input circuit 4 but are preferably tapped thereto through by-passing condensers 42, 44 at opposite sides of the terminating connection 4% having therein the grid leak and condenser arrangement Cil 48 for subjecting grid 6 to a suitable operating potential. Preferably, adjustment of the output ends of the line to coil 45] should be made such that the lines face into an impedance equal in value to their characteristic surge impedance or resistance.

As already pointed out, since the lines are sub- ,iected to instantaneous polarities 180 degrees out of phase, corresponding adjacent points along the lines will also be out of phase, as a result of which radiation from the lines will be substantially nil. Since the ratio of the line current to the current circulating in the tank circuit I2 is twice that of a single line of equal length, the frequency controlling effect of both lines will be twice as great as that of a single line.

Oscillatory output energy may be fed inductively, if desired, to a suitable power amplifier and/or frequency multiplier 56 and thence radiated over a suitable radiating antenna 52. Modulation may be accomplished by supplying modulating potentials through transformer 54 to electron discharge device 56 in turn varying the current flow in accordance with modulating potentials through resistor 24. Because of the resultant variations in plate or anode voltage and screen grid voltage of oscillator tube 2, output energy in output circuit l2 will be amplitude modulated in accordance with the modulating potentials supplied through transformer 54.

Having thus described my invention, what I claim is:

1. An oscillator consisting of a single electron ischarge device having within an hermetically sealed container an electron emitting cathode, an anode, a control electrode and a screen grid, a circuit having inductance and capacity connected between said control electrode and said cathode, a circuit having inductance and capacity connected between said anode and cathode, at least one of said circuits being resonant to approximately a desired operating frequency, means grounding intermediate points on said circuits for high frequency currents, a circuit polarizing said screen grid and preventing capacity feed back from said anode to said control electrode, and a pair of transmission lines connecting said control electrode and anode circuits together, said transmission lines being connected to said cir cuits on opposite sides of said circuit grounding means whereby said lines are excited with voltages of opposite instantaneous polarity.

2. A high frequency oscillatory system consisting of a single electron discharge device having an anode, a cathode, a control electrode, and a screen grid, a circuit grounding said screen grid for high frequency currents whereby interelectrode feed back between said anode and control electrode is prevented, a circuit tuned to approximately a desired operating frequency connected between said control electrode and said cathode, another circuit tuned to a desired operating frequency connected between said anode and cathode, means grounding intermediate points on said circuits for high frequency currents, a pair of relatively closely spaced trans mission lines each of equal length and a plurality of half wave lengths long at a desired operating frequency coupling said circuits together Whereby regenerative energy is fed over said lines from said anode cathode circuit to said control electrode cathode circuit, and animpedance equal in value to the surge impedance of said lines coupled to the output ends of said lines whereby feed back over said lines is rendered substantially aperiodic.

GEORGE EMERSON PRAY.

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