US2247234A - Electron beam tube circuits - Google Patents

Description

June 24, 1941. C, W HANSELL 2,247,234

ELECTRON BEAM TUBE CIRCUITS Filed May 28, 1958 Pon/ER AMPL/F/ER FREQUENCY Ml/l 7' /PL IER AIVD MPl/F/ER E'ECTOR BUFFER MPL /F/ER AUD/0 INVENTOR. HM@ om? ,vos #uf/Amm A TTORNEY.

Patented June 24, 1941 UNITED STATES PATET CFFICE ELECTRON lBEAM TUBE CIRCUITS Clarence W. Hansell, Port Jefferson, N. Y., assignor to Radio Corporation of America, a corporation of Delaware Claims.

The present invention relates generally to novel circuits employing a cathode ray type of electron tube wherein an electron stream is shifted between a pair of anodes under the influence of a deflecting electric eld. More specifically, the invention is described in connection with a radio frequency transmitter circuit, although it should be understood that various aspects of the invention are not limited thereto.

In most modern radio frequency transmitters, it is customary to produce radio frequency energy in a relatively low power oscillator whose frequency is controlled by a piezo-electric crystal. The output of the crystal oscillator is then amplified and the frequency thereof multiplied to obtain the final output power and frequency for the transmitter in a manner described in my United States Patent No. 2,032,208, issued February 25, 1936. At some point in this known type of system there is provided means for keying or modulating the transmitter output. The modulation may be produced by Varying the amplitude, phase, or frequency of the energy going to make up the transmitter output.

According to the present invention, there is employed the cathode ray type of tube for all or any of the foregoing purposes heretofore achieved by the ordinary type of vacuum tube. In the invention it is preferred to employ a specic type of cathode ray tube characterized by the use of two cup-shaped anodes symmetrically arranged with respect to the cathode and so designed as to reduce the effects of secondary emission caused by electrons striking the anodes. A shield is provided between the anodes to which is attached an accelerating grid structure in the path of the electrons. In the operation of this type of tube, practically all of the electron stream will be focussed upon the shield passing through the center of the accelerating grid in the absence of a deiiecting electric field, and little or no electron current will flow to the anodes. However, upon the occurrence of a deecting eld, such as may be -produced by a radio frequency signal, the electron stream will oscillate back and forth across the center shield or bridge of the accelerating grid and a portion of the electron stream will pass through the grid to the anodes. With relatively appreciable high-frequency deflecting potentials, most of the electron stream will strike the anodes. For intermediate values of applied radio frequency deecting potentials, the distribution of electron current between the grid and anodes will vary more or less in proportion to the strength of the applied radio frequency current, and if the tube is properly designed, the distribution or variation in electron flow to the grid and anodes Will reproduce any amplitude modulation which may be present in the applied radio frequency current. For a more detailed description of such a tube, reference is made to my United States Patent No. 2,066,037, granted December 29, 1936.

A better understanding of the invention may be had by referring to the following description, which is accompanied by a drawing, wherein:

Fig. 1 shows the invention as applied, by way of example, to a radio frequency transmitter circuit whose vacuum tubes constitute cathode ray devices which with their associated circuits are illustrated schematically, and

Fig. 2 shows the invention as applied to a crystal oscillation generator circuit, which is a modification of the oscillation generator shown in connection with Fig. 1.

Referring to Fig. 1 in more detail, there is shown diagrammatically a transmitter circuit composed of a crystal oscillator I, a buffer amplifier 2, a frequency multiplier 3 and a power amplier 4. Of course, a greater number of tubes or stages than that shown in the drawing may be used for each particular function.

Each tube is of the cathode ray type employing two cup-shaped anodes A, A having an accelerating grid G interposed between said anodes and the cathode K. The anodes A, A are shielded from each other by the grid support and shield S located symmetrically between the anodes. Both the anodes A, A and the accelerating grid G are maintained at suitable positive potentials relative to the associated cathode. Suitable focussing and deflecting electrodes D, D for each tube are designed so that with suitable potentials they will cause the electrons to strike the center of the grid G at the location of the supporting shield S in the absence of deiiecting potentials, and to shift the electrons to strike the anodes A, A alternately upon the application of suitable radio frequency potentials to the electrodes D, D. The anodes A, A are cupshaped and so spaced that electrons strike the interior thereof where there is Very little, if any, Ipotential gradient and where, as a result, secondary electron emission which results from electron impact will not be drawn out. A suitable bias source, not shown, supplies a negative potential, indicated in the drawing by the minus sign, to the deflecting electrodes D, D of each tube in order to bias the same in suitable manner for operation.

cuit consisting of a variable condenser C and anV inductance coil L, tuned to the operating frequency. The crystal and associated connections of oscillator I here appear as an effective inductance and the output circuit is also an effective inductance. These two inductances provide series resonance for the two feed-back condensers C, C at the oscillating frequency, thereby providing correct phase relations between input and -output alternating current potentials of the tube for maintenance of oscillations.

The defiecting electrodes of the buffer amplier 2 are connected symmetrically across the output coil L of the oscillator, as shown, and the output of the buffer is tuned in a manner similar to the output of the oscillator. This Vbuffer prevents reaction between the oscillator I and the frequency multiplier 3 which is coupled to the output of the buffer, thereby providing,

greater constancy of frequency.

As for the frequency multiplier 3, it should be noted that both anodes thereof are connected in. parallel so as to produce in the output thereof two pulses of current for each cycle of input.

energy applied to the deflecting electrodes.

Any suitable utilization circuit, such as an antenna 5, is shown connected to the power ampliiier 4, in turn coupled to the frequency multiplier 3.

For modulating the energy to be transmitted, there is shown a keying device comprising an audio amplifier 6 to whose deectingelectrodes there may be supplied a suitable keyed tone signal, and a keying detector tube 'I in whose out-- put is a resistor R connected also to the accelerating grid of the multiplier 3. In the operation of this keying circuit, variations in intensity of the tone, such as may be caused by telegraph key interruptions, will vary Vthe 1R drop in resistance Rin the output circuit of tube l. Any decrease in current in resistance R will produce an increased positive potential on theaccelerating grid of frequency multiplier 3 and an increase in the amplitude of the output of the multiplier.Y

An increase in current in resistance R will, of course, produce a decrease in the amplitude of the output energy in the multiplier. The audio components of current appearing in the output of the keying detector tube will be suppressed by a b-y-pass condenser or suitable nlter, leaving only the keying wave to be impressed upon the frequency multiplier grid. Y

If desired, a modulated super-audible carrier could be used for the audio frequency keyed tone signal, and the modulations would then appear on the frequency multiplier; or the keying tube 7 maybe connected and used as an audio yamplifier having impressed on it an audio frequency current which will modulate the output of the multiplier to produce amplitude modulation. For this purpose the output may be taken from a transformer 4having a primary lwinding-connected between the two anodes and a secondary connected to modulate or vary the potential on the grid of the frequency tripler tube.

Fig. 2 shows a modified form of crystal oscillator in accordance with the invention, wherein there is obtained regeneration of a type in which the crystal and associated connections, and also the output circuit, appear as effective capacitances, in contradistinction to the oscillator circuit of Fig. i, wherein the crystal and associated connections, and the output circuit, appear as effective inductances. The frequencies of operation of Figs. 1 and 2 are on opposite sides of the crystal resonant frequency, and consequently are slightly different from each other. However, the crystal oscillator will be stable in frequency in either case due to the constancy and low power factor of the crystal as an equivalent oscillating circuit.

If it is desired to reduce fading by frequency diversity in the case of telegraphy, or to transmit telephony or multiplex telegraphy, etc., phase modulated waves may be transmitted by varying the phase of the oscillations anywhere in the transmitter system ahead of the final output circuits. This can be accomplished by paralleling any stage, say the buffer amplifier by another amplifier having a phase displaced high frequency input and-then differentially modulating the input and output of the two paralleled ampliers.. Other means for producing phase modulation, known'in the art, may also be used.

Frequency modulation may be employed if the crystal oscillator is replaced by a high frequency source which can be frequency modulated. Frequency modulatedsources are already known in the art.

Of course my system of Fig.,2 may be extended to higher power levels by adding additional ampliiers. The beam type tubes indicated in Fig. 1, in the present stage of development, are limited to rather low power levels. Consequently, available tubes of more conventional types would be used in higher-power stages when required.

What is claimed is:

l. An electron tube oscillator having an electron emitting element, a plurality of anode members symmetricallyarranged relative to the emitting element, and a pair of deiiecting electrodes intermediate the emitting element and the anodes, all within an envelope, controllable capacitive feed-back paths directly connecting saidanodes to said deiiecting electrodes, and a piezo-electric crystal connected across said de- .flecting electrodes for controlling the frequency of the generated oscillations, whereby the frequency of operation of said oscillator is slightly different from the resonant frequency of said crystal.

2. An electron tube oscillator employing an electron stream and having a cathode, a plurality of anode :members symmetrically arranged relative to sai-:l cathode, aA pair of deflecting members on opposite sides of the electron stream and intermediate rsaid cathode and said anodes, all within an evacuated envelope, a direct capacitive feed-back path fromv each anode to that deecting electrode which is onthe same side of the normal path of travel of said electron stream, a tuned circuit coupled to said anodes and a resonant circuit coupled across said deflecting `electrodes for stabilizing the frequency of generated "oscillations, said resonant circuit, said tuned circuitfand associated connections appearing as effective inductances, whereby the frequency of operation of Vsaid oscillator is slightly diierent from the resonant frequency of said resonant circuit.

3. An electron tube oscillator employing an electron stream and having a cathode, a plurality of anode members symmetrically arranged relative to said cathode, a pair of deecting members on opposite sides of the electron stream and intermediate said cathode and said anodes, all within an evacuated envelope, a capacitive feed-back path from each anode to that deecting electrode which is on the other side of the normal path of travel of said electron stream, a tuned circuit coupled to said anodes, and a resonant lcircuit coupled across said deecting electrodes for stabilizing the frequency of generated oscillations, said resonant circuit, said tuned circuit, and associated connections appearing as effective capacitances.

4. An electron tube oscillator employing an electron stream and having a cathode, a plurality of .cup-shaped anode members symmetrically arranged relative to said cathode, a pair of deflecting members on opposite sides of the electron stream and intermediate said cathode and said anodes, all within an evacuated envelope, a capacitive feed-back path directly connecting each anode to that deecting electrode which is on the same side of the normal path of travel of said electron stream, a tuned circuit coupled to said anodes, and a piezo-electric crystal resonant circuit coupled across said deflectlng electrodes for stabilizing the frequency of generated oscillations, said resonant circuit, said tuned circuit, and associated connections appearing as eiective inductances, whereby the frequency of operation of said oscillator is slightly dierent from the resonant frequency of said crystal.

5. An electron tube oscillator employing an electron stream and having a cathode, a plurality of cup-shaped anode members symmetrically arranged relative to said cathode, a pair of deecting members on opposite sides of the electron stream and intermediate said cathode and said anodes, all within an evacuated envelope, a capacitive feed-,back path from each anode to that deflecting electrode which is on the other side of the normal path of travel of said electron stream, a tuned circuit coupled to said anodes, and a piezo electrical crystal resonant circuit coupled across said deflecting electrodes for stabilizing the frequency of generated oscillations, said resonant rcircuit, said tuned circuit, and associated connections appearing as effective capacitances.

CLARENCE W. HANSELL.

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