US2529408A - High-frequency generator - Google Patents

Description

Nov. 7, 1950 A. MONTANI HIGH-FREQUENCY GENERATOR Filed Sept. 24, 1945 FIG. I

m nzbo FIG. 2

INVENTOR.

ANGELO MONTANI ATTORN EY Patented Nov. 7, 1950 UNITED STATES TENT OFFICE HIGH'-FREQUEN CY GENERATOR Application September 24, 1945, Serial No. 618,353

3 Claims.

The present invention relates to space discharge devices, and particularly to space discharge devices of the electron beam type.

It' has heretofore been proposed to produce oscillating currents by means of a cathode ray beam which is caused to scan a mask having a series of perforations, or apertures, therein, and collecting the electrons which pass through the perforations on a collector anode positioned behind the mask. The stream of electrons is interrupted by the mask and consequently the col lector supplies a number of impulses whose frequency depends upon the velocity of the beam movement and the number of apertures.

It is an object of the present invention to provide an improved spaced discharge device of the electron beam type for :producing oscillating currents having any desired waveform.

Another object of the'invention is to provide an improved spaced discharge device of the electron beamtype for efiecting a multiplication in the frequency of an alternating current.

Briefly, these objects are accomplished by providing a collecting electrode and a mask in a tube structure similar to a conventional cathode ray tube. The mask is preferably constructed in the form of a grid having interstices which vary in size in a predetermined manner. The mask is scanned by the cathode ray beam causing a current which varies in accordance with variations in the size of the interstices in the mask to be produced therein. A complementary current is produced in the collecting electrode, located behind the mask, by the electrons passing through the interstices. fication of the invention the mask is formed by two intersecting groups of parallel wires, the interstices between the wires in each group varying progressively in a predetermined manner. With this mask more complex output currents may be obtained by deflecting the cathode ray beam both horizontally and vertically. In a second modification of the invention a ring-shaped mask is used having interstices about the circumference thereof which recurrently vary in size-in a continuous manner. When this mask is scanned by a rotating cathode ray beam an alternating current having a frequency which is a multiple of the scanning frequency will be produced in the mask and in the collecting electrode.

The invention will be better understood from the fOllOWil'lg description when considered in conjunction with the accompanying drawing, in which:

Fig. 1 discloses one form of the invention in According to onemodi- 1 which the electron beam is cyclically deflected along a rectilinear scanning path;

Fig. 2 is a modification of Fig. l in which the electron beam is deflected in two directions; and

Fig. 3 is a modified form of mask forusein the tube shown in Fig. 2.

Referring to Fig. 1 of the drawing, there is shown a cathode ray tube having the conventional heater l, cathode 2, and beam forming electrodes 3, t, and 5, all of which are energized-by a suitable battery 5, or the like. The. pencillike electron beam, indicated by the broken line '1, passes between a pair of deflecting electrodes 3, which are positioned on opposite sides of the beam axis. It is to be understood that the equivalent magnetic deflecting coils or other suitable means may be substituted for the electrostatic deflectin electrodes, if desired. The electron beam is caused to scan a. rectilinear path along the length of mask 9' by applying an alternating voltage from a suitable source, such as an oscil lator ill, to the deflecting electrodes 8. The mask 9 may conveniently be constructed in the form of a pair of spaced apart arcuate supporting rods, which arebridged by a number ofparallel spaced apart wires in the manner of ladder rungs. The spacing of the bridging. wires varies along the length of the arcuate supporting rods in a manner dependent upon the output waveform de-' sired. Several successive cycles of such variations in the interstices may be used, if desired. Located behind the mask 9 is a collecting electrode or plate, 12, upon which electrons passing through the mask 9 impinge. The mask 9 and the collecting electrode l2 are connected to battery 6 through resistorsl3 and [4, respectively, across which the output voltages are obtained when the tube is in operation. As the electron beam travels-from the top to the bottom-of mask 5 a progressively smaller portion of the electrons in the beam will be intercepted by'the mask and a progressively larger portion of the electrons will pass through the mask etc impinge on the collecting electrode l2. On the return sweep of the electron beam the converse action takes place.

Undulating currents are thus caused to flow through resistors l3 and 14, which may be bridged by small condensers l5 and [6, respectively, to smooth out the waveform of the voltage appearing thereacross.

In Fig. 2 an additional pair of deflecting electrodes ll are provided to deflect the electron beam l in the horizontal plane under the control of a second oscillator H. The mask or grid, l8 may in this case be conveniently formed by two groups of parallel spaced apart wires, the wires in the two groups intersecting at right angles. The grid may conform to the surface of a sphere with center at a point on the axis of the tube between the pair of deflecting plates 8 and [1, as illustrated, to eliminate distorting effect which may otherwise be introduced when the electron beam is deflected large amounts. The spacin between the grid wires in each group is varied progressively across the mask. With either one of the oscillators or H inactive, the tube shown in Fig. 2 operates the same as that shown in Fig. 1. When both of the oscillators l0 and II are active, however, very complex waves may be produced by the tube shown in Fig. 2. The wave shape of the output Voltage obtained across resistors l3 and [4 may be varied by changing the amplitude or the frequency of either one of the oscillators ID or H with respect to the other. These two oscillators may be interlocked by means of well known synchronizing methods.

In Fig. 3 there is shown a circular mask which may be used in the tube shown in Fig. 2 in place of mask I8 in order to adapt the tube for use as a, frequency multiplier. The mask 20 may comprise a disk 2! and concentric ring 22, between which a number of grid wires, such as 23, extend in radial directions. The grid wires are located so as to provide a plurality of closely spaced areas between which the spacing varies progressively to a maximum value. Two such cyclic variations in spacing have been shown in Fig. 3. If the two oscillators l0 and II are adjusted to the same frequency with their outputs in phase quadrature the electron beam 1 will scan a circular path on the mask 20. It is preferable to use only one oscillator and to provide a suitable phase shifting network in order to obtain the necessary quadrature relation between the horizontal and vertical deflecting voltages. When the electron beam 1 scans a circular path on the grid wires of the mask 20, a current having a frequency twice that of the scanning frequency will be produced therein by the electrons intercepted thereby. A similar current will be produced in the collecting electrode or plate, H! by the electrons impinging thereon which pass through the mask 20. A greater frequency multiplication factor may be obtained by increasing the number of cyclic variations in the spacing of the grid wires in the mask 20. It should be noted that this device provides a substantially continuous flow of energy to the output circuit instead of depending upon shock excitation of a resonant circuit by impulses created by a commutated electron beam. The output frequency may therefor be varied by adjusting the scanning rate without the need for any readjustment of tuned circuits in the output circuit as in prior electron beam frequency multipliers.

While what is now considered to be the preferred form of the invention has been illustrated, it is to be understood that numerous modifications may be incorporated therein without departing from the true spirit and scope of the in- 6 vention as defined in the subjoined claims.

What is claimed is:

1. A high frequency generator comprising an electron gun having a heater cathode, and forming electrodes, means for activating said electron gun, means for deflecting a projected stream of electrons in a fixed path, a collector anode located in said path, and a mask located in said path between said electron gun and said anode for screening a stream of electrons deflected in said path towards said anode, said mask consisting of a screen having a plurality of openings of variable areas for correspondingly varying the intensity of a stream of electrons deflected in said path and projected upon said anode through said openings of said mask, said openings of said mask occurring in at least two sequential series, the areas of the openings in each said series varying progressively from an area of minimum value to an area of maximum value accordin to a definite pattern.

2. In a high frequency generator, the combination with an electron discharge device having means for emitting a beam of electrons, and horizontal and vertical beam deflecting means for deflecting an emitted beam of electrons in a closed two-dimensioned path, of a collector electrode positioned in said path and a grid positioned in said path between said first means and said collector electrode for screening an emitted beam of electrons deflected in said path towards said collector electrode, said grid comprising a screen having a plurality of openings, said openings varying in size progressively in two intersecting directions according to a predetermined pattern for correspondingly varying the intensity of an emitted beam of electrons deflected in said path and projected upon said collector electrode through said openings of said grid.

3. In a high frequency generator, a cathode, a plate, means for forming an intensified beamof the electrons emitted from said cathode to said plate, means for rotating said intensified beam of electrons in a closed two-dimensioned path substantially circular in form, a ring-shaped mask located in said path between said cathode and said plate, said mask having a plurality of radially directed openings of varying areas located therein for correspondingly Varying the intensity of said rotating beam of electrons projected upon said plate through said openings of said mask, said openings radially located in said mask in two sequential series, the areas of the openings in each said series varying progressively from an area of minimum value to an area of maximum value in accordance with a prescribed plan.

ANGELO MONTANI.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,026,892 Heintz Jan. 7, 1936 2,071,382 Balsley Feb. 23, 1937 2,086,904 Evans July 13, 1937 2,173,193 Zworykin Sept. 19, 1939

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