US2105902A

US2105902A - Periodic voltage generator

Info

Publication number: US2105902A
Application number: US64022A
Authority: US
Inventors: Cawein Madison
Original assignee: Hazeltine Corp
Current assignee: BAE Systems Aerospace Inc
Priority date: 1936-02-15
Filing date: 1936-02-15
Publication date: 1938-01-18
Anticipated expiration: 1955-01-18
Also published as: GB489625A; DE688088C; NL47553C; FR817870A

Description

Jan. 1a, 1938.

M. CAWEIN 2,105,902

PERIODIC VOLTAGE GENERATOR Filed Feb. 15, 1936 FIG. I. IO {I2 [l5 [l4 [l5 CARRIER T VIDEO CATHODE FREQUENCY DETECTOR FREQUENCY RAY AMPLIFIER w AMPLIFIER TUBE l6 f PICTURE FREQUENCY. GENERATORR INVENTOR.

I MADISON C EIN I Q r I I11 ATTO NEY.

new 1.... 1a, was 2,105,902

UNITED STATES PATENT OF'FlCE rrmomo vouriioc csncaa'ron Madison Cawcin, Mnnhasw N. Y., assignor to multiple corporation, a corporation or Delaware Application February 15, 1936, Serial No. 54,022 12 Claims. (C 250-36) This invention relates to the generation of periis, applied to the plates with equal amplitudes odlc voltages of complex wave form, such as and opposite polarities, if maximum efliciency is saw-tooth and related forms, and to the utilitobe obtained. More particularly, by tilizi'ng two zation of such voltages, particularly for effecting balanced deflecting voltages only one-half of the 5 cathode-ray scanning in television systems. voltage amplitude is required for each half of the According to present practice in television sysscanning voltage supply, as in the case where tems, a carrier wave is transmitted, modulated by a n l un an s nn n v l is d. n picture or video-frequency signals, corresponding 116K166 an Operating voltage may be used for h to the varying values of light and shade in the generator which is of an amplitude of only onet itt picture, Scanning synchronizing imhalf that which would be needed if a single un- 10 pulses are also transmitted, usually also as modubalanced Scanning Voltage were to be developedlation frequencies impressed on the same tele- Furthermore, any electrostatic and magnetic disvision carrier as the video frequencies. A cathturbances to which the voltage supply circuits ode-ray tube is employed at the receiver, whercare subjected will be balanced out or neutralized in a cathode ray. or electron beam is produced in these circuits also, when such a balanced ar-' 5 and focused upon a fluorescent screen. Voltages fln is p y atvideo frequencies, derived from the received It is an object of the present invention to carrier, are utilized to vary the intensity or the provide an improved generator for d veloping ray according to the signal amplitude. In order p riodic voltages which are of balanced, and h to effect scanning of the screen by the ray, sawp ly f wooth, w v form. wh ch are 20 tooth voltage or current waves are generated and of relatively high amplitudes, and which are utilized at the receiver to produce, respectively, p cia ly sui l for e in a l v i n r ceiver electrostatic or magnetic fields of saw-tooth wave to effect scanning by the cathode y form which deflect the cathode ray, usually hori- A further object of this invention is to provide zontally for line scanning and vertically for pica generator of the character described, which is 25 ture scanning. The well-known rectilinear patrelatively simple in its construction and operation. tern is thereby traced upon the screen to repro- In accordance with the present invention, duce-the scene. The synchronizing impulses dethere is provided a periodic voltage generator rived from the carrier are utilized to control or which includes capacitance means, as for example operate the scanning wave generators so that the a condenser, and a source of direct current. A 30 scanning actions at the receiver are maintained in pair of circuits is provided for charging the caproper synchronism with the corresponding acpacitance means to opposite polarities from the tions at the transmitter. direct-current source, and means-are provided In present practice, relatively high voltages are for controlling the circuits, periodically to charge employed for the electrodes of the cathode-ray the capacitance means alternately to opposite 5 tube, as ior focusing the ray, and correspondingpolarities. One of the circuits includes two imly high scanning voltages are, therefore, required. pedance means of substantially equal values and It is, of course, essential that the saw-tooth scansymmetrically disposed in the circuit for the ning voltages be of such wave term as to effect periodic current th r in. The rm ym accurate linearityof trace and rapid retrace of rically disposed as used in this specification and 40 the scanning ray. Furthermore, it is highly dein the appended claims is intended to denote the sirable that the scanning voltage generators be relationship whereby corresponding portions of relatively simple in their construction and operthe elements, in connection with which the term ation. is employed, are always at equal and opposite Because 01 inherent electrostatic and magnetic periodic voltages with respect to ground. Suitdisturbances to which the deflecting plates or a able means are provided for utilizing the balanced cathode-ray tube are subjected in operation, it is periodic voltages developed across the impedance desirable, it not necessary, that these plates he means. electrically balanced with respect to ground, In the preierred embodiment of the invention, thereby to neutralize the effects of the disturbconstant-current devices, such as pentode tubes ances (which will then occur simultaneously and having suitable potentials applied to their elecin the same polarity on the opposite plates). trodes, are employed as the impedance means, With the plates so balanced" with respect to and vacuum tube conductances are employed for ground, the deflecting voltages applied thereto controlling the circuits periodically to effect the should also be balanced relative to ground. that alternate charge of the capacitance means to accelerating the action of the control tubes.

opposite polarities. Suitable means, as for example a regenerating tube, may be provided for of a cathode-ray tube, to eifect scanning by the ray.

For a better understanding of the-present intion, while Fig. 2 is a graph of the balanced sawtooth voltages developed by the generator shown Fig; 1.

eferring now particularly to the drawing, the

frequency or superheterodyne type,

includes, in cascade, an antenna and ground as lO-I I, a carrier-frequency amplifier I2, a detector l3, a video-frequency amplifier I4 and a cathoderay tube l5. ere the receiver is of the superheterodyne type, the conventional oscilator l I,

will be hereinafter further described. The tube I5 is preferably conventional in construction and operation.

Since the system shown in the drawing, thus far described, is, in general,,wel-l understood in the art, a detailed explanation or its general nal from the amplifier i2 is delivered to the detector l3 in which are derived the video frequencies of modulation including the synchronizing-i'requency components which are supplied to the video-frequency amplifier I 4, wherein they are amplified and thence supplied,

in the picture-frequency generator l8 and line-frequency respectively, which generators are, as stated. conthesynchronizing-voltage; impulses and are applied to the scanning elements of the cathode-ray tube to produce magnetic and elecnate charges of the condenser to opposite polarbattery [9 generator I1,

the screen and thereby reproduce the transmitted picture. Referring now more particularly to the portion of the system shown in the drawing which embodies the present invention, the voltage generator l1 comprises capacitance means, more particularly a condenser III, and a direct-current source, such I9. by-Da Scd for periities. Specifically, one of the charging circuits of the condenser l8 includes thecontrol means,

biasing potential is applied the tube 2| from a tap on the battery It! by way of a resistor 24. The other charging circuit includes impedance means which, in the embodiment of the invention illus- Specifically, the constant-current penand 33 are connected with their space-- current paths in series across the through the condenser 18 .and

resistors

34 and 35. Suitable potentials are supplied from the nitude as the voltage, of the source 19. the resultant balanced saw-tooth voltage is of an amplitude approaching twice that of the voltage of the source. It will be understood,.however, that in place of the constant-current devices,

For regenerating the operation of the tubes 20 and 2|, there is provided a regenerating tube 25. The input circuit of the tu 251s eifecti'vely coupled to one of the charging 0 ts of the coni denser l8 and to the video-frequency amplifier ll 75 circuit. The junction of'theresistors 39 and Ill the anode of the tube 23 and the other terminal,

through a coupling condenser 21, to the videofrequency amplifier H. The cathode of the tube 25 is grounded and its control grid circuit includes a suitable biasing resistor 29. The anode of the tube 25 is connected'directly to the control grid of the tube 2| and, by way of a coupling condenser 33, to the control grid of the Operating voltage is supplied from the battery l3, by'way of a resistor 3|, tube 25.

In order to utilize the periodic voltage thus developed, opposite terminals of the condenser Il may be connected, by'way of coupling condensers 31 and 33, directly to the scanning or deflecting elements of the cathode-ray tube i5. Preferably, a pair of serially-connected resistors 39 and ill having their junction grounded for periodiccurrents is connected across the load may be grounded, for direct current also, as shown, or may be maintained at any suitable direct voltage with reference to the operating voltages of the electrodes of the cathode-ray tube.

In considering the operation of the generator ll shown in the drawing, a single cycle will be described in detail from the point in the cycle at which the condenser I3 is charged to its maximum potential with its upper plate, as shown in the drawing, positive. The tubes 32 and 33 are at all times conductive but the charging circuit of the condenser through these tubes is of high impedance, thereby limiting the rate of charge to a predetermined value. Under these conditions the condenser I3 is gradually and linearly charged, so that the potential of its upper plate increases negatively and that of its lower plate, positively through the circuit commencing at the positive terminal of the battery 19 and-including the tube 32, resistor 34, condenser H, the tube 33 and resistor 35, to the other side of the battery. During this charging operation the potential of the cathode of the tube 32,and thus that of the anode or the tube increases positively, approaching that of the positive terminal of the battery I9, Similarly, the potential of the anode of the tube 33,- and thus 'that of the cathode of thetube 20, increases negatively, approaching that of the negative terminal of the battery I3. This charging action continues until suflicient voltages are built up across the tubes 20 and 2| to break down the .tubes to initiate the flow of current therethrough. The initial surge of current results in a voltage impulse across the resistor 22 which is applied negatively to the control grid of the 'tube' 25 by way of the resistor 25 and condenser 28, thereby reducing the conductance of this tube and producing a positive voltage impulse across the resistor 3i. This positive voltage -is-instantaneously applied to the control grids of the tubes 20 and 2|,

the action of these tubes being thereby regenerated or accelerated, so that "current builds up rapidly in the charging circuit which-includes these tubes and charges the condenser I! to the opposite polarity. As the charge of the condenser ll approaches its-maximum value of the initial 7 polarity, the charging current is reduced rapidly, with theresult that the cathode of the tube 20 rapidly approaches the potential of the positive terminal of the battery 19, while the cathode of the tube 2| rapidly approaches the potential of to the anode of the 2 I connected thereto,

the negative terminal of the battery i9. Under these conditions, the grid of the tube 23 becomes negative with respect to its cathode by an amount approaching the voltage drop across the resistor 3 I while the grid of the tube 20 becomes negative relative to its cathode by an amount approaching through the resistor 25. The tubes 23 and 2i are thus rendered-non-conductive and the charging of the condenser 13 to the opposite polarity is tial polarity, since the impedance of the circuit including the tubes 32 and 33 is very much higher than that of the circuit including the tubes 20 and M.

The charging of the capacitance means or condenser IB alternately to opposite polarities is periodic and the action is synchronized by virtue of the synchronizing impulse voltages which are applied negatively to the control grid of the tube 25 from the video-frequency amplifier, by way of the coupling condenser 21 and voltage divider 25. The circuit constants are so selected that the voltage built up across the tubes 23 and 2i during the trace is justshort of breaking down these tubes with normal grid voltages applied. During this portion of the cycle the grid voltage of the tube of" a negative synchronizing impulse, the conductanceof the tube 25 is suddenly decreased and its anode voltage raised. That is, the grid volt.- ages of the tubes 2il'and 2| are increased positively to such a value that their existing anode voltages are suflicient to break them down. The effectiveness, on the control of the tube 25, of the synchronizing voltage impulses from the video-frequency amplifier I4 and the voltage developed across resistor 22 may be controlled simultaneously and in opposite senses by adjustment of the tap on the voltage divider. Properly synchronized operation of the generator may thus be obtained. It will be understood that suitable discriminating means will be included in the input circuit of the generator H5 or II, or both, to en.- sure that each is controlled only by its respective synchronizing impulses. Since the impedances of the tubes 32 and 33 are of substantially equal values, as are the

resistors

34 and 35. and since these elements are symmetrically disposed in current of the generator, the alternating voltage developed across the condenser I8 is substantially balanced with respect to ground. This voltage is impressed across the resistors 39 and 40 and is sent time and the ordinates represent amplitude. Relative polarities are indicated as and and ground is indicated as 0. The received synchronizing voltage impulsessupplied by thevideofrequency amplifier determine the frequency at the generator, and the constants of the circuit determine the amplitude of the resultant voltages til 'the bias impressed thereon from the battery l3 1 their respective charging circuits for the periodic developed. As clearly shown by the curves 4|,

and 42, the voltages which are developed are balanced relative to ground.

While there has been described what at present is considered the preferred embodiment of the invention, it will be obvious to those skilled in 1 the art that various changes and modifications may be made therein without departing from the invention, and it is, therefore, aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is: g

1. A periodic voltage generator comprising capacitance means, a direct-current circuit, a pair 4 of circuits for charging said capacitance means to opposite polarities from said direct-current circuit, means for controlling said pair of circuits I periodically to effect alternate charges of said capacitance means toopposite polarities, one. of the circuits of said pair including two impedance means of substantially equal values and symmetrically disposed therein for the periodic current of said generator, and an output circuit in which the periodic voltages developed across said impedance means appear as balanced oppositely poled voltages. v

2. A periodic voltage generator comprising capacitance means, a direct-current circuit, a'pair of circuits for charging said capacitance means to opposite polarities from said direct-current circuit, means for controlling said pair of cir- I cuits periodically to eifect alternate charges of means to opposite polarities from said direct-current circuit, means for controlling said pair of said capacitance means to opposite polarities, one of the circuits of said pair including two impedance means of substantially equal values and symmetrically disposed therein for the periodic current of said generator, at least one of said impedance means being adapted to maintain the current in said circuit substantially constant, and an output circuit in which the periodic voltages developed across said impedance means appear as balanced oppositely poled voltages.

3. A periodic voltage generator comprising capacitance means, a direct-current circuit, a pair of circuits for charging said capacitance means to opposite polarities from said direct-current cir cuit, means for controlling said pair of circuits periodically to,efiect'alternate charges of said capacitance means to opposite polarities, one of the circuits of said pair including two impedance means of substantiallyequal values and symmetrically disposed therein for the periodic current of said generator, each of said impedance means comprising a constant-currentdevicefor -maintaining the current in'said circuit substantially constant, and an output circuit in which the periodic voltages developed across said impedance means appears as balanced oppositely poled voltages.

'4. A periodic voltage generator comprising capacitance means, a direct-current circuit, a pair of circuits for charging said capacitance circuits periodically to effect alternate charges of said capacitance means to opposite polarities, one ofthe circuits of said pair including two impedance means of substantially equal values and symmetrically disposed therein for the periodic current of said generator, each of said impedance means including the space-current path of a pentode tube, means for applying potentials to the electrodes of said tubes whereby they are eflective to maintain the current in saidcircuit which the periodic voltages developed across said impedance means appear as balanced oppositely poled voltages.

5. A periodic voltage generator comprising capacitance means, a direct-current circuit, a pair of circuits for charging said capacitance means to opposite polarities from said direct-current circuit, means for controlling said pair of circuits periodically to efi'ect alternate charges of said capacitance means to opposite polarities, one of the circuits of said pair including two unilaterally conductive impedance means of substantially equal impedance values, said impedance means being symmetrically disposed for the periodic current of said generator, and an output circuit in which the periodic voltagm developed across said impedance means appear as balanced oppositely poled voltages.

6. A periodic voltage generator comprising capacitance means, a direct-current circuit, a

pair, two unilaterally conductive means symmetrically disposed therein for the periodic cur rent of said generator and connected with such polarity as to charge said capacitance means to a polarity oppo ite to that of said first circuit, and

an output 0 cult in which the periodic voltages developed across said impedance means appear as balanced oppositely poled voltages.

7. A periodic voltage generator comprising capacitance means, a direct-current circuit, a pair of circuits 'for charging said capacitance means to opposite polarities from said directcurrent circuit, means for controlling said pair of circuits periodically to eifect alternate charges of said capacitance means to opposite polarities comprising, in one of the circuits of said pair,

-two impedance means of substantially equal 'values and symmetrically disposed therein for the periodic current of said generator and, in the other of the circuits of said pair, the space-current paths of two vacuum tubes serially connected and symmetrically disposed therein for the periodic current of said generator, and an output circuit in which the periodic voltages developed across said impedance means appear as balanced oppositely poled voltages.

8. A periodic voltage generator comprising capacitance means, a direct-current circuit, a

pair of circuits for charging said capacitance means to opposite, polarities from said directcurrent circuit, means for controlling said pair of circuits periodically to efiect alternate charges of said capacitance means to opposite polarities comprising, in one of the circuits of said pair, two impedance means of substantially equal values and symmetrically disposed therein for theperiodic current of said generator and, in the other of the circuits of said pair, the space current paths of two vacuum tubes each having a control electrode, said tubes being serially connected and symmetrically disposed therein for the periodic, current of said generator, means for energizing said control electrodes with synchronizing voltage impulses, and an output circapacitance means, a

cuit in which the periodic voltages developed across said impedance means appear as balanced oppositely poled voltages.

9. A periodic voltage generator comprising direct-current circuit, ,a pair of circuits for charging said capacitance means to opposite polarities from said direct-current circuit, means for controlling said circuits periodically to effect alternate charges of said capacitance means to opposite polarities comprising, in one of the circuits of said pair, two impedance means of substantially equal valuw and symmetrically disposed therein for the periodic current of said generator and, in the other of the circuits of said pair, the space-current paths of two vacuum tubes each having a controlelectrode, said tubes being serially connected and symmetrically disposed therein for the periodic current of said generator, means for energizing said control electrodes with synchronizing voltage impulses, means'associated with said tubes for regenerating the action thereof, and an output circuit in which the periodic voltages developed across said impedance means. a

10. A periodic voltage generator comprising capacitance means, a direct-current circuit, a 'pair of circuits for charging said capacitance means to opposite polarities from said directcurrent circuit, means for controlling said pair or said capacitance means to opposite polarities comprising, in one of the circuits of said pair, two impedance means or substantially equal values and symmetrically disposed therein for the periodic current of said. generator and, in

the other ofthe current paths oi two vacuum tubes each having a control electrode, said tubes being serially connected and symmetrically disposed therein Patent No. 2,105,902.

of circuits periodically to effect alternate charges circuits of said pair, the space-,

CERTIFICATE OF CORRECT-ION.

MADISON CAWEIN p for the periodic current of said generator, means for energizing said control electrodes with synchronialng voltage impulses, a regenerating vacuum tube amplifier having its input circuit coupled to one or said circuits and itsv output circuit coupled to the control electrode of at least one of said charging tubes, and an output circuit in which the periodic voltages developed across said impedance means.

11. In a cathode-ray tube television receiver, a periodic voltage generator for developing scanning voltages for the tube of said receiver comprising capacitance means, a direct-current circuit, a pair of circuits for charging said capacitance'means toopposite polarities from said direct-current circuit, means for controlling said pair of circuits periodically to effect alternate charges of said capacitance means to opposite polarities, one of the circuits of said pair including two impedance means of substantially equal values and symmetrically disposed therein for the periodic current of said generator, and an output circuit in which the periodic voltages-developed across said impedance means.

12. An electric circuit arrangement for developing a periodic voltage balanced relative to January- 18, 1958.

It is hereby certified that error appears in the printed specification of the abovemumbered patent requiring correction as follows: Page second column line 21. claim', for the word "air" read pair; page 5, first column,

-line 8 cla1m9, after "said" insert pair of; 'line 2h, same claim, and'sec'onc' column, lines 9and 21 claims 10 and 11' respectively, after "means" and before th'e period insert'the words appear as balanced oppositely poled volt- Office.

( Seali Signed and sealed this 29th day of March, A. D; 19 58.

a Henry Van Arsdale,

- acting commissioner of Patents.

ages; and that the said- Letters Patent should be read with these corrections therein that thesame may conform to the record of the case in the Patent capacitance means, a

CERTIFICATE OF c0RREcTIoN.-

( Seali Signed and sealed this 29th day of March, A. D; 19 58.

a Henry Van Arsdale,

- acting commissioner of Patents.

ages; and that the said- Letters Patent should be read with these corrections therein that thesame may conform to the record of the case in the Patent