US2363809A - Electronic tube circuit - Google Patents

Description

NV- 28, 19.44 o. H. SCHADE' ELECTRONIC TUBE' CIRCUIT 'Filed Jan. 20, 1943 l ....DaPDO mmJDa E m w Vl m55 Dn mH yo wm .m mr 0 Vl B Patented Nov. 28, 1944 ELECTRONIC TUBE CIRCUIT" om n. schade, West Caldwell, N. J., assigner to Radio Corporation oi America, a corporation of Delaware Application January 20, 1943, Serial No. 472,952

6 Claims.

This invention relates to an improvement in impulse mixer circuits, and more specifically to an improvement in `a circuit arrangement for mixing impulses in a television system where the impulses correspond to the horizontal and ver-` tical deection frequencies.

In the transmission of television signals, as is ywell known to those skilled in the art, some means must be providedfor maintaining synchronous operation of the various receivers with the transmitter. This is accomplished by transmitting a series of synchronizing impulses which, when received at the television receiving apparatus, are effective to maintain the desired degree of synchronism. In order that the' necessary degree of synchronism may be maintained, it is desirable vto transmit a synchronizing impulse corresponding to each line scanned, and a further synchronizing impulse corresponding to each field scanned. The line scanning rate and/or the eld scanning rate `may be altered to suit particular circumstances, but in any event, synchronizing impulses of relatively short duration are generally transmitted corresponding to each of these parameters.

In the .conventional transmission of television signals, the line synchronizing impulses are transmitted during the interval between picture signals representative of each line, and the field synchronizing impulses are transmitted during the interval between picture signals representa# tive of each field. In an electronic television system, these synchronizing signals initiate the horizontal andvertical return of the cathode ray beam.

In television transmitting systems, impulses of both line and eld frequencies are also used to blank or obliterate picture signals which may be produced during the return deflection of the scanning cathode ray beam or, as an alternative, impulses of line and eld frequencies ,may be used to interrupt the scanning cathode ray beam orv For e (Cl. TIS-69.5)

In most television transmitting systems, an impulse generating system is provided which produces impulses ofline and eld frequency in order that a denite relationship may be maintained between the frequencies of the two series of impulses, and through the use of frequency divider circuits, the line and field series of impulses may be derived from dierent parts of the impulse generating system. When these impulses are applied to an impulse mixing or combining circuit, they are combined so that the produced series of impulses will represent e a composite of both the line and field impulse series.

Various mixer circuits have heretofore been used, but frequently such circuits are not of optimum desirability in that they do not produce the desired wave form in a composite impulse series, or they may require an excessive inputy voltage to produce the desired final wave form. Furthermore; presently known impulse mixing circuits are somewhat complex and include a great number of tube elements and parts. In the present invention, an impulse mixing circuit has been provided which is simple in operation and which will produce a desired composite wave form by the application of a relatively low intensity controlling impulse series.

One purpose of the present invention, therefore, resides in the provision of an impulse mixing circuit which is simple in operation, and which embodies the use of a limited. number of tube and circuit elements.

Another purpose of the present invention resides 'in the provision of an impulse mixing circuit wherein it is possible to produce a desired composite wave form, the impulse mixing circuit being initiated by relatively low intensity impulses of line and eld frequency.

A still further purpose of the present invention resides in the provision of an impulse mixer circuit in which tilted or peaked impulses maybe applied to the mixer circuit without affecting the wave form of the composite series of impulses.

Still other `purposes and advantages of the present invention will become more apparent to those skiued in the art from the foiiowing depling condenser 40.

streams or paths may be enclosed within the same tube envelope or, as will be appreciated, two

separate tube envelopes may be used..

One of the electron streams or paths a cathode I2, a control electrode I4 and an an'ode includes I6. The other electron path includes a cathode shown) by way of anode resistance 26.-.- AThe 1 control electrode I4 is maintained at apotential slightly positive with respect to the cathode i2 by means of a potential divider including resistances 2B and 30 which are connected in series between the positive terminal 24 and the negative terminal or ground. The control electrode I4. is connected to the junction of these resistances, and the potential of the control electrode I4 with respect to the cathode l2 may be determined by properly proportioning the value of the resistances.

The cathode I8 of the second electron path is connected to ground by way of cathode resistance 32, while the anode 22 is connected to the positive terminal 24 by means of the anode load resistance 34. A potential divider including series resistances 36 and 38 is connected between the positive .terminal 24 and the negative terminal or ground, while the control electrode is connected to the junction of these resistances. The potential of the control electrode 20 relative to ground may, therefore, be controlled by proportioning thek resistances 36 and 38. The anode I6 of the first electron path is connected to the cathode I8 of the second electron path by means of a cou- Impulses of horizontal or line deflection frequency are applied to the input terminals 42 and 44', these terminals beingA connected respectively to the control electrode I4 of the rst electron path and to ground. The` horizontal impulses may have a Wave form such as indicated at 46, the 'frequency of the impulses corresponding to I the line deflection frequency. When impulses of such a wave form are applied to the control electrode I4, a potential variation is available at the anode I6 similar to the wave form shown at 48. The bias of the control electrode I4 relative to the cathode I2Iis such that the first electron path performs a clipping action on the applied impulses with the result that the impulse peak is removed. Naturally, the polarity of the impulses is reversed due to the phase inversion operation of the tube. These impulses, as represented at 4B, are then applied to the cathode I8 of the second electron path tomodulate the cathode potential relative to ground.

Impulses .of vertical or eld deflection frequency-are' applied to the terminals 50 and 52 preclude the passage of current to anode 22.

The impulses of line deflection frequency as represented at 48 which are applied to the cathode I6 are also `oi? sufficient intensity to cause the tube 'to be vblocked by driving the cathode I8 positive.

Current through the second electron path. is. therefore, interrupted both during the applica'- tion of impulses of line frequency to the cathode I8, and during the application-of'eld impulses to the control electrode 20. Modulation of the electron stream in the second electron path, therefore, varies the amount of current in the anode circuit with the result that a potential variation may be derivedfrom the anode 22 which is representative of the combined series of impulses. This potential variation may be derived from output terminals .56,and 58, the former being connected to the anode 22 by way of a relatively large condenser 60, -while the terminal 58 is connected to ground or some point of xed potential. The output terminals 56 and 58 are connected together by a variable resistance 62 of a relatively low value.

In order that the second electron path including cathode I8 and anode 22 may be driven to cut-off by cathode modulation, the anode resistance 34 is made relatively large in order to reduce the plate voltage at the anode 22 in orden that the impulses of line frequency as applied to the cathode I8 may produce a sharp cut-off of the 'for example, by the dotted line 55 associated with the Wave form curve 54. The composite or mixed impulses which are available from the anode 22 of the second electron stream are, therefore, positive inv polarity and arel preferably derived by Way of a relatively low alternating current load in order to maintain goud wave form. The low impedance alternating current loadv is produced by means of the relatively large condenser 60. andv the relatively small resistance 62.

In order that proper direct current potentials may be applied to the control electrodes I4 and 20, the resistance 30 is generally chosen to equal approximately 10% of the value of resistance 28, while the resistance 38 is generally chosen to equal approximately 5% of the resistance 36. The cathode resistance 32 may have a value of approximately 500 to 1,000 ohms While the anode resistance 26 for the first electron path may have a value from 15,000 to 50,000 ohms. As explained above, in order to produce a sharp cut-olf in the second electron path, the anoderesistance 34 should preferably have a fairly high value corre- Y sponding to approximately 200,000 ohms.

For performing the combining or mixing operation, the tube I0 may be of the type 6SM-GT or type 7F?, although it is to be understood that various other single or dualpurpose tubes may be used wheredesired.

The base line of the mixed impulses, as represented by the wave form 64 and available from the output terminals 56-58', can be made perfectly at or it maybe tilted to a desired degree for one or both of the input' impulse series by pre-tilting the base line of the Wave forms supplied to either of the control electrodes le or 20.

46 that the horizontal vimpulses as applied to the input terminals 42and 44 extend in a negative direction. lf, however, vthe available impulses of horizontal deflection frequency should extend in a positive direction, a similar mixing circuit could be used by providing cathode coupling between the two triode sections of the tubeV l0. I1' horizontal impulses of such polarity are applied to the input terminal 42, it would still be desirable to apply positive impulses of horizontal deflection frequencyto the cathode I8 of the triode section including cathode I8, control electrode 20 andanode 22. In this case, the coupling condenser 40 would be omitted and the cathode l2 would be directly connected to the cathode I8 in 'order to aiord the desired cathode coupling. The cathode resistance 32 would then be common to both cathode electrodes.

With such a slight revision it would then be possible to apply horizontal impulses having a pclarity reversed with respect to those shown in the gure, and still utilize the present invention for affording a circuit arrangement for mixing the horizontal and vertical impulses. The samel tube types as suggested above could be used, or, if

desirable, a tube such as the type 6SC7 could be 4,

employed since this particular tube type has a common cathode electrode.

Furthermore, it is conceivable that the application of the horizontal and vertical impulses to the cathode I8 and control electrode`2ll could be reversed, assuming, of course, that the polarity of the impulses is simultaneously reversed. Under these conditions, vertical impulses that extend in a positive direction could be applied to the cathode I B, and horizontal impulses extending in a negative direction could be applied to the control electrode 20. These latter impulses would be derived from anode I6 by Way of condenser 40 and would result from the application of horlzontal impulses to the control electrode I4, the pulses extending in a positive direction. It is desirable that the polarity of the applied pulses operate to 'bias the control electrode- 20 with respect to the cathode I8 such that electron flow to the anode 22 is precluded.

In the present invention, the duration of the individual horizontal impulses corresponds tol about 7% to 8% of the horizontal deection nterval, and the duration of the vertical impulses corresponds to about 1.0 or 1.5 horizontal deflection cycles. It is to be understood, however, that impulses of different time duration could as Well be used in the present invention.

Through the use of the present invention it may, therefore, be seen that an effective and efficient impulse mixing or combiningcircuit has been provided which will respond to applied impulses of relatively low intensity, and which will produce theV desired composite wave form even though some tilting or peaking may be present in the applied impulses. Furthermore, it will be appreciated that all of the impulses of the composite series as represented by the curve 64 have the same intensity, their duration and frequency being determined by the duration and frequency of the applied horizontal and vertical impulse series. It will'lalso be appreciated that an irnpulse mixer circuit has been provided which will produce a composite series of impulses without in any Way affecting the operation or action of the sources from which the independent series of horizontal and vertical impulses are derived.

Although the present invention has been described somewhat in detail, it will be appreciated that various alterations and modifications mayv be made therein without departing from the spirit and scope thereof, and it is desired that any and all such alterations and modiflcations be considered Within the purview of this invention except as limited Iby the hereinafter appended claims.

Havingnow described my invention, what I claim as new and desire to have protected by Letters Patent is: Y

l.4 An impulse mixer for combining two series of impulses, the impulses of each series differing in time duration and frequency, comprising a rst and second electron discharge path each including a cathode. a control electrode, and an anode, an

anode load .impedanc-e associated with each electron discharge path, means for 4applying the lmpulses of one of the series to the'control electrode of the rst electron discharge path to produce vvoltage variations of corresponding time duration and frequency across the load impedance of that path, means including a coupling condenser for applying the voltage variations produced across the load impedance of the first electron discharge path to the cathode of the second electron discharge path, means for ,applying the other series of impulses to the control electrode of the second electron discharge path whereby the impedance of the second electron discharge path will be altered by both the applied produced voltage varia- I tions and the other applied series of impulses.

` the series tothe control electrode of the rst elecand an output circuit coupled-across the anode load impedance of the second electron dischargepath.

2. An impulse mixer circuit for combining two series of impulses comprising a rst and second` electron' discharge path each including a cathode, a control electrode and an anode, an anode load impedance associated with each electron discharge path, means for applying the impulses of one of the series to the control electrode of the first electron discharge path to thereby produce corresponding voltage variations at the anode of that path, means for applying the voltage variations produced at the anode of the rst electron discharge path and the other series ofimpulses to the cathode and control electrodefof the second electron discharge path' to produce a series of voltage variations corresponding to the combined series of impulses, and an output circuit associated with the second electron discharge path. y

3. An impulse mixer circuit f or combining two series of impulses, the impulses of each series differing in time duration and frequency, comprising a first and second electron discharge path each including `a cathode, a control electrode and an anode, means to apply the impulses of one of tron discharge path to thereby produce voltage variations of corresponding time duration and frequency across an anode load circuit associated with the path, and means to apply the voltage variations produced across the anode load circuit and the other series of impulses to the cathode one frequency to the control electrode of the first L electron current path to produce voltage variations of a corresponding frequency at the anode of that electron current path, means for applying the voltage variations produced at the anode of the first electron discharge path to the cathode of the second electron current path, means for applying the impulses of said another frequency to the control electrode of the second electron current path, the applie'dproduced volt- 5. An impulse mixer circuit for combining a series of impulses of one' frequency with arseries y of impulses of another frequency comprising a first and second electron dischargepath each having a cathode, a control electrode and an output electrode, means for applying the impulses of the one frequency to the control electrodeof the first electron discharge path to produce corresponding potential variations at the output lelectrode of that electron discharge path, means for applying the potential variations produced at the output electrode of the first electon'discharge path to the cathode of the second electron discharge path, and means for applying the voltf age variations of the other frequency to the con- 'trol electrode of the second electron discharge path, the applied produced potential variations and the applied impulses of the other frequency being effective to modulate the electron stream in the second electron discharge path to produce voltage variations representative of the combined impulses of both frequencies at the output electrode of the second electron discharge path.

6. An impulse mixer circuit for use in a television system for combining a series of impulses of line frequency with a series of impulses of iield frequency comprising a first and second electron discharge path each including a cathode; a control electrode and an anode, means to apply impulses of line frequency to the control electrode of the rst electron discharge path to produce corresponding voltage variations at the anode of that electron discharge path, means to apply the voltage variations produced at the anode of the first electron discharge path to the cathode of the second electron discharge path, means to apply the impulses of eld frequency to the control' representative of both line and field frequency at the anode of the second electron discharge,

path, and an output terminal connected to the anode of said second electron discharge path OITO H. SCHADE.

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