Title:
Electrical device
United States Patent 2144337


Abstract:
My invention relates to electric wave shaping apparatus and particularly to a method of and means for producing an electric wave of the desired wave shape by deflecting a cathode ray. S Various forms of apparatus have been employed for producing electric waves having a wave shape other than...



Inventors:
Koch, Winfield R.
Application Number:
US6618736A
Publication Date:
01/17/1939
Filing Date:
02/28/1936
Assignee:
RCA CORP
Primary Class:
Other Classes:
313/326, 313/349
International Classes:
G06G7/26; H03B13/00
View Patent Images:



Description:

My invention relates to electric wave shaping apparatus and particularly to a method of and means for producing an electric wave of the desired wave shape by deflecting a cathode ray.

S Various forms of apparatus have been employed for producing electric waves having a wave shape other than that of a sine wave. Such apparatus generally includes thermionic vacuum tubes, iron core inductances, gas discharge tubes, to or the like. It is often difficult to obtain exactly the desired wave shape when employing such apparatus.

An object of my invention is to provide an improved method of and means for producing elect. tric waves of any desired wave shape. A further object of my invention is to provide improved apparatus including a cathode ray tube for producing an electric wave of non-sinusoidal wave form.

In one embodiment of my invention a cathode ray tube is so designed that the cathode ray is spread out in a plane or line instead of being confined to a ray of small diameter, as is customary in cathode ray tubes. This plane or line of a25 electrons is projected towards a plate having a shape which preferably conforms to the wave shape desired, and the cathode ray is deflected along this plate whereby the number of electrons striking the plate varies from instant to instant to produce a flow of current having the said wave shape.

One of several other embodiments of the invention includes a cathode ray tube having a fluorescent screen and further includes a photo-electric cell and a mask positioned between the fluorescent screen and the photo-electric cell. The mask has an opening therein which preferably has a shape which conforms to the wave shape of the desired electric wave whereby the amount of light reaching the photo-electric cell varies from instant to instant as the cathode ray is deflected across the fluorescent screen.

Other objects, features and advantages of the invention will appear from the following description taken in connection with the accompanying drawings, in which Figures 1, 2 and 3 are schematic and circuit diagrams of three embodiments of my invention, Figures 4, 5 and 6 are end views of the mask and cathode ray tube shown in Figure 3, the three different views showing masks with three different shaped openings, Fig. 7 is a group of curves which are referred to in explaining the operation of the apparatus shown in Fig. 3, and Fig. 8 is a block diagram of a radio transmitter utilizing my invention.

Referring to Fig. 1, the apparatus includes a cathode ray tube comprising an evacuated envelope 1, an indirectly heated cathode 2, a control grid 3, a first anode 4 and a second anode or signal plate 6, which is specially shaped as above mentioned. Preferably another plate 7 is provided adjacent to the plate 6, as illustrated, for the purpose of aiding in the acceleration of the electrons and for providing a return path for electrons which do not strike the signal plate 6.

A screen grid 8 and a suppressor grid 9 may be provided which serve the same purpose as like grids in conventional amplifier tubes. In the embodiment illustrated, the cathode ray is spread out into a plane or line at right angles to the plane of the paper by means of two deflecting or focusing plates II which have a fixed voltage of the proper value supplied thereto. If desired, the same results may be accomplished by properly designing the electron gun and omitting the focusing plates.

Suitable positive voltages are supplied to the first anode 4, the grids 8 and 9 and the plates 6 and 7 from a suitable source such as a battery indicated at 12. A negative biasing voltage is supplied to the control grid 3 from a suitable source such as a battery 13.

Voltage is supplied to the signal generating plate 6 through an output resistor 14 across which the desired signal voltage appears. This signal voltage may be supplied through a coupling condenser 16 to a suitable amplifier 17.

The operation of this apparatus depends upon the fact that as the electron stream, indicated at 18 by the dotted lines, is deflected in a vertical plane by suitable deflecting devices such as deflecting plates 19, the number of electrons striking the signal plate 6 and passing through the output resistor 14 depends upon the angle of deflection of the electron stream. For example, with the electron stream in the position indicated on the drawings, the amount of current flowing 45 through the output resistor 14 is greater than when the electron stream is deflected further from the center of the tube and it is less than when the electron stream is deflected towards the center of the tube. Obviously, the current flow through the output resistor 14 and, therefore, the voltage applied to the grid of the amplifier tube 17 depends upon the shape of the signal plate 6 and the wave shape of the voltage applied to the deflecting plates 19. The deflecting voltage, preferably, is either sinusoidal or saw-tooth in wave form.

Referring to .ig. 2 of the drawings, there is illustrated a cathode ray tube 21 which is conventional in construction except for certain modifications which will be described. The tube Includes the usual electron gun 22 and second anode 23, the electron beam being focused electrostatically. As In the embodiment of the invention shown in ig. 1, a signal plate 24 is provided which is positioned in the path of the electron beam and shaped in accordance with the wave form of the signal wave to be generated. The signal plate 24 Is connected through an output resistor 26 to ground whereby a flow of current is produced through the resistor which is proportional to the number of electrons striking the signal plate.

In this embodiment of the invention, the electron beam is in the form of a pencil of electrons substantially circular in cross section. This electron beam is deflected at a comparatively high frequency by means of deflecting plates 27 or Sother suitable deflecting devices whereby the electrons traverse the signal plate 24 along a line as indicated by the dotted lines 28. In order to produce the desired signal wave, the electron beam is also deflected in a plane substantially at right angles to the first deflection by means of other deflecting plates 29 or other suitable deflecting devices.

It will be understood that the operation is substantially the same as the operation of the device previously described. The main difference in operation is that, while the electron beam is being deflected vertically by means of the low frequency deflecting plates 29, impulses of energy are being applied to the signal plate 24 at the frequency ot the deflection produced by the other deflecting plates 27. Because of this, the signal voltage appearing across the resistor 26 is supplied to the amplifier tube 17 through a filter 31 which may consit of an inductance coil 32 and shunt condensers 33 and 34. The filter 31 is given a time constant which is greater than the period of the deflecting wave applied to the high frequency deflecting plates 27 whereby an uninterrupted voltage is applied to the grid of tube 17, the magnitude of the voltage changing in consonance with the low frequency deflection of the cathode beam and in accordance with the shape of the signal plate 24.

Deflecting waves of any desired wave form may be applied to the deflecting plates but in general either sine waves or saw-tooth waves are preferred.

Referring to Fig. 3, the cathode ray tube 36 may be the same as the tube 21 shown in Fig. 2, except that a fluorescent screen 37 is provided at 80 the end of the tube. In this embodiment of the invention, it is desired to produce a line of light on the fluorescent screen and to deflect this line of light behind a mask having an opening therein whereby the amount of light passing through the mask depends upon the shape of the opening. In the drawings, a photo-electric cell is indicated at 38 for receiving light from the fluorescent screen 37. A mask 39 and a suitable optical system 41 are located between the photo-electric cell 38 and the screen 37. One form of mask is shown in Fig. 4, this being an end view of the mask 39 and cathode ray tube 36.

In the particular embodiment shown in Figs. 3 and 4, the electron beam is deflected vertically at a comparatively high frequency by deflecting Splates 42 whereby, as the electron beam is deflected more slowly in the horizontal plane by Sthe deflecting plates 43, a vertical line of light moves across the mask opening. As the line of light moves from the center of the tube to either side, the amount of light passing through the opening increases whereby the output of the photo-electric cell 38 increases. A filter 44 should be provided in the output circuit of the photoelectric cell 38, as indicated, in order to integrate the light impulses caused by the high frequency deflection of the electron beam. It will be understood that the necessary filter action may be provided in the photo-electric cell amplifier 46 itself, if desired. As in the apparatus shown in ig. 2, the filter requirements are that the time constant of the filter be greater than the period of high frequency deflection.

By properly shaping the opening of the mask, any desired alteration in wave shape can be secured. Thus, if "square law" operation Is desired, each side of the opening of the mask 38 is given a parabolic curve as show in Fig. 4. With this mask and with a saw-tooth voltage applied to the high frequency deflecting plates 42 and a sine wave voltage, indicated at 45 in Fig. 7, applied to the low frequency deflecting plates 43, the resulting signal supplied to the amplifier 46 has the wave shape indicated by the curve 47 in Pig. 7. It will be noted that this signal Is sinusoidal in wave form and has double the frequency of the signal applied to the low frequency deflecting plates 43, this being the signal which is re-shaped.

By using a mask 48 with an opening having the shape indicated in Fig. 5 (the upper side of the opening following a parabolic curve), the modulating audio wave at a transmitter may be given a "square root" shape so that with a linear modulator at the transmitter the receiver may have a "square law" detector without any resulting distortion. With a high frequency saw-tooth wave applied to the plates 42 and with the modulating sine wave applied to the plates 43, the resulting wave having the "square root" shape is shown by the curve 50 in Pig. 7.

The diagram in Mg. 8 shows how such a wave shaper may be included in a radio transmitter.

A wave shaper of the type above-described is indicated at 49.

By making the opening in a mask 51 of the shape shown in Fig. 6 the cathode ray tube may be employed to give "linear detection" by applying the radio or intermediate frequency voltages to the deflecting plates 43. The wave form of the signal applied to the amplifier 46 when the mask is of the form shown in Fig. 6 is indicated by the curve 52 in Fig. 7. It will be apparent that this is a rectified sine wave.

It may be noted that if the fluorescent material of the fluorescent screen continues to glow after the bombardment stops, the slope of the "decay" curve should be steep and the shape of the opening in the mask may have to be modified.

From the foregoing description, it will be appar- 05 ent that various other modifications may be made in my invention without departing from the spirit and scope thereof and I desire, therefore, that only such limitations shall be imposed thereon as are necessitated by the prior art and are set forth in the appended claims.

I claim as my invention: 1. An electrical wave generator comprising an electric discharge tube having means for producing a stream of electrons spread out in a certain 7g plane whereby their cross-section is a line, a fluorescent screen positioned in the path of said electrons whereby a line of light is formed thereon, a photo-electric device positioned to receive said light, a mask positioned between said fluorescent screen and said photo-electric device, said mask having an opening therein which is shaped in accordance with the desired wave shape of the electrical wave to be generated, and means for deflecting said stream of electrons substantially at right angles to said certain plane whereby the amount of light reaching said photo-electric device from said line of light varies in accordance with the shape of said mask opening. 2. An electrical wave generator comprising an electric discharge tube having means for producing a beam of electrons, a signal plate of electrically conducting material shaped in accordance with the desired wave shape of the electrical wave to be generated, means for deflecting said electron beam at a comparatively high frequency in a certain plane whereby said electrons strike said signal plate along a line, means for deflecting said electron beam periodically at a comparatively low frequency and substantially at right angles to said line, whereby the number of electrons striking said plate is varied, and means including a filter for taking the resulting signal from said plate, said filter having a time constant which M is larger than a period of said high frequency deflection.

3. An electrical wave generator comprising an electric discharge tube having means for producing a beam of electrons, means for deflecting said s5 electrons in a certain plane at a comparatively high frequency, a fluorescent screen positioned in the path of said electrons whereby a line of light is formed thereon, a photo-electric device positioned to receive said light, a mask positioned between said fluorescent screen and said photoelectric device, said mask having an opening therein which is shaped in accordance with the desired wave shape of the electrical wave to be generated, means for deflecting said beam of electrons substantially at right angles to said certain plane whereby the amount of light reaching said photo-electric device from said line of light varies in accordance with the shape of said mask opening, and an output circuit for said photo-electric device, said output circuit having a time constant which is larger than the period of one of said high frequency oscillations.

4. An electrical wave generator comprising an electric discharge tube having means for producing a beam of electrons, means for deflecting said beam in a certain plane at a comparatively high frequency, means including a screen structure so positioned in the path of said beam that said deflection causes said beam to trace a line thereon for generating in response to deflection of said beam at right angles to said certain plane a signal voltage having a wave shape determined by the outline of said screen structure, means for deflecting said beam at right angles to said certain plane at a comparatively low frequency, an output circuit including a filter having a time constant which is larger than the period of one of said high frequency oscillations, and means for supplying said signal voltage to said output circult.

5. An electrical wave generator comprising an electric discharge tube having means for producing a stream of electrons effectively spread out in a certain plane whereby their effective cross-section is a line, means for deflecting said beam periodically in a plane substantially at right angles to said certain plane in accordance with an electrical field, and means including a screen structure having an area bounded by an edge parabolic in shape and by an opposite edge which is a straight line for making successively changing fractions of said line of electrons effective to produce signals during said deflection, said screen structure being located with said straight line edge at right angles to said certain plane whereby the wave shape of said signals is the square root of the wave shape of said electrical field.

WINFIBD B. KOCH.

DISCLAIMER 2,144,337.-Winfield R. Koch, Camden, N. J. ELECTRICAL DEVICE. Patent dated January 17, 1939. Disclaimer filed November 22, 1939, by the assignee, Radio Corporation of America.

Hereby enters this disclaimer to claims 2 and 4 in said specification. [Official Gazette December 19, 1989.]