US2118977A - Television apparatus - Google Patents

Television apparatus Download PDF

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US2118977A
US2118977A US747324A US74732434A US2118977A US 2118977 A US2118977 A US 2118977A US 747324 A US747324 A US 747324A US 74732434 A US74732434 A US 74732434A US 2118977 A US2118977 A US 2118977A
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voltage
current
tube
saw
tooth
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US747324A
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Harold M Lewis
Cawein Madison
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HASELTINE Corp
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HASELTINE CORP
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Priority to US747324A priority patent/US2118977A/en
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Priority to FR796194D priority patent/FR796194A/fr
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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K4/00—Generating pulses having essentially a finite slope or stepped portions
    • H03K4/06—Generating pulses having essentially a finite slope or stepped portions having triangular shape
    • H03K4/08—Generating pulses having essentially a finite slope or stepped portions having triangular shape having sawtooth shape
    • H03K4/10—Generating pulses having essentially a finite slope or stepped portions having triangular shape having sawtooth shape using as active elements vacuum tubes only
    • H03K4/12—Generating pulses having essentially a finite slope or stepped portions having triangular shape having sawtooth shape using as active elements vacuum tubes only in which a sawtooth voltage is produced across a capacitor
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K4/00—Generating pulses having essentially a finite slope or stepped portions
    • H03K4/06—Generating pulses having essentially a finite slope or stepped portions having triangular shape
    • H03K4/08—Generating pulses having essentially a finite slope or stepped portions having triangular shape having sawtooth shape
    • H03K4/10—Generating pulses having essentially a finite slope or stepped portions having triangular shape having sawtooth shape using as active elements vacuum tubes only
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K4/00—Generating pulses having essentially a finite slope or stepped portions
    • H03K4/06—Generating pulses having essentially a finite slope or stepped portions having triangular shape
    • H03K4/08—Generating pulses having essentially a finite slope or stepped portions having triangular shape having sawtooth shape
    • H03K4/10—Generating pulses having essentially a finite slope or stepped portions having triangular shape having sawtooth shape using as active elements vacuum tubes only
    • H03K4/26—Generating pulses having essentially a finite slope or stepped portions having triangular shape having sawtooth shape using as active elements vacuum tubes only in which a sawtooth current is produced through an inductor

Definitions

  • a primary object of the invention is to produce voltage oi saw-tooth wave form to serve as an electrostatic control of scanning in a cathode ray television receiver.
  • Another primary object of this invention is to produce current of saw-tooth 15 wave form through inductance toprovide the new. for magnetic control of scanning in a cathode ray television receiver.
  • Another. object of this invention is to provide circuitsand apparatus ⁇ or generating the saw-tooth andrelated wave forms go in a precisely controllable and economical manner for use in television.
  • Another object of the invention is to generate voltage and current wave forms related to the saw-tooth wave forms which will serve to govern or control'the generation oi voltage or current of saw-tooth form.
  • Figs. la-ld inclusive illustrate as applied to a cathode-ray tube. the manner in which voltages and currents of saw-tooth and related wave forms are employed to eflect scanning in a television receiver.
  • Fig. 2 is a schematic diagram of a cathode-ray television receiver to illustrate the essential units required for receiving, scanning and controlling a television image- Figs. lid-3e inclusive, graphically depict a soealled derivative series of wave forms of which the saw-tooth form is one, to illustrate the voltage and current relationships relative to pure reactances, such as inductance and capacity shown diagrammatically in Figs. 3) and 39 respectively.
  • Figs. 4a, b and c are graphs explanatory of the fcorrect use of the saw-tooth wave forms in scanning the lines in a television picture.
  • Figs. 511-5] inclusive. are graphs similar to those of Fig. 4. illustrative of the use of the saw- 50 tooth wave form for scanning at picture frequency.
  • Figs. Git-6g inclusive are a series oi. fundamental circuits pertaining to the generation of voltages and currents oi saw-tooth and related 55 wave forms.
  • Figs. 7a and b and Figs. 8a and b are diagrams of the wave forms of current and voltage resulting from operation of certain of the Figs. 8a.- to So circuits.
  • an Figs. 9a, b and c, and Figs. 10a, b and c are diagrams of the wave forms of current and voltage resulting from operation of certain of the Figs. 8a.- to So circuits.
  • Figs. 11c. b and c are graphs illustrating wave form suitable for causing current of saw-tooth wave form to flow in an impedance.
  • Fig. 12 is to a simple form oi inductance in series with resistance type or generator, designated as the L/R type.
  • . 'Flgs. 13c. b and 0. show vacuum tube arrangements for utilizing impulse, or impulse plus sawtooth voltage wave forms to cause a saw-tooth wave form .0! current to flow through inductance,
  • Fig.--14 shows a resistance-capacity or R. C type of generator operating as 'an impulse voltage source ior a scanning inductance.
  • Fig. 15 shows a-similar resistance capacity typ oi generator-arranged to function as an impulse generator ior causing saw-tooth waveform of current-toilew through an inductance.
  • Figisid is a simplified circuit developed from Fi Figs. 17, 18, 19a and 19b represent strictly L/R type generators oi saw-tooth currents; I
  • Figs. 20, 21 and 22 show the use of resistancecapacity type generators as properly poled sources oi saw-tooth plus impulse voltage for grid control of vacuum tubes whereby saw-tooth current is caused to flow through inductance in the tube output circuits.
  • Fig. 23 is a vacuum tube arrangement simulat ing the fundamental L/R circuit 0! Fig. 16.
  • Fig. 24 illustrates the use of a dynatron as an L/R. generator 01' saw-tooth current through an inductance.
  • the present application is one of a series oi related copending applications to the same inventors, which in aggregate, describe a complete television transmitting and receiving system employing saw-tooth and related wave forms for line and picture scanning.
  • copending application oi' H; M. Lewis. Serial No. 747,070, flied October 5, 1934 there is described the trans-- copendingapplications, or its equivalent. is to be received to provide the vision irequency signals and control impulses referred to in this application ior reproducing the image at the receiver.
  • A represents the luminescent-screen end of a cathode-ray tube K, upon which the scanning traces are indicated as they would appear in their ideal form when no signal is being received and, applied to modulate the grid of tube K to control the intensity of the electron beam striking the screen.
  • This ideal trace is of saw-tooth wave form in that each line is a linear trace from left to right (indicated by heavy line m to represent a constant value of illumination of the screen) and a rapid (practically zero time) retrace-from right to left (indicated bya light line 12) since practically no electrons strike the screen in this brief retrace interval and the illumination is therefore weak.
  • the succession or rate at which the lines are traced is shown to be linear with time from top to bottom of the screen since the lines m and n are evenly spaced for the lines shown and the retract p. q from bottom to top of. the picture is shown to be rapid in that it occurs in the time required for two lines to be traced; and hence these two lines appear oppositely sloped in the picture retrace.
  • the line frequency 111., n saw-tooth wave form has an almost infinite ratio between time of trace and retrace
  • the picture frequency p, q, saw-tooth wave form has a ratio of trace to retrace shown as 10 to 1.- This manner of scanning the picture from left to right and from top to bottom is termed rectilinear scanning.
  • the number of pictures trans mitted per second may be taken as 24, and the line frequency taken as 2880 per second. At least this is a sufllcient definition of quality to serve in this application for purposes of describing the inventions.
  • the ratio of picture trace to retrace time is in practice about 40 to 1 (much better than shown in the illustration). Hence, with the line frequency of 2880 per second, there are 117 lines in each picture and three lost in the picture retrace.
  • This ratio has a correspondence dimensionally to the ratio between the height of picture in a standard mm. motion picture film and the opaque space separating adjacent picture frames (the film to space ratio being, in fact, about 30 to 1).
  • trace-to-retrace ratio in practice is about 10 to 1 which. is far from the ideal of zero time shown in Fig. 1.
  • the cathode ray may be deflected by magnetic or electro-static fields. Magnetic deflection is illustrated in Fig. 1.
  • the coils L1, L1 serve to provide the field for the picture frequency scanning while L2, L2 similarly serve to provide the field for line frequency scanning. Since the magnetic field changes proportionally to the current flowing in these coils, the current through L1, L1 must have As for the line frequency, a reaso-nable tooth wave form at the line frequency m, 11 rate. 4
  • a series of wave forms related to the sawtooth' wave form has been plotted and is shown in Figs. 3a to Be inclusive. This may be termed a derivative series", since any of the wave forms shown is the mathematical derivative of the wave form immediately below it in the series.
  • the utility of this series as it stands relates to pure reactance, since fundamentally the volt age er. across an inductance, Fig. 3f, is the derivative of the current 11. through the inductance, and the current in through a condenser, Fig.
  • Fig. 3g is the derivative of the voltage 80 across the condenser; Hence using the notation at the left of the figure, if a current through a pure inductance has any of the wave forms shown, the voltage acrossthe inductance must be of the wave form shown immediately above, and if a voltage across a pure condenser has any of the wave forms shown the current through the condenser is of the wave form shown immediately above in the series.
  • Fig. 3c is the desired wave form for scanning and is shown as providing a ratio of 10 to 1 in the time of trace to retrace.
  • Fig. 3:: will be referred to as a double-impulse; Fig. 3b as an impulse; Fig. 3c as a saw-tooth, and Fig. 3d as a parabolic impulse wave form.- The form Fig. 3e
  • the cathode ray tube K employs deflecting plates for electrostatic scanning, wherein P1, P1 are the deflecting plates for the'picture frequency and P2, P2 the deflecting plates for the line frequency scanning. Since the deflection of the electron stream is proportional to the voltage between the deflecting plates, the voltage across P1, P1 should be saw-tooth as indicated by the notation 63c and that across plates P2, P: similarly should be saw-tooth in form as labeled 83c.
  • Fig 1c illustratesmagnetic deflection.
  • coils L1, for the picture frequency'and electrostatic deflection, plates P2,. for the line frequency, and hence the voltage required to cause'saw-tooth current in L1, L1 is of impulse wave form 83b as indicated,
  • the saw-tooth wave is also important in mechanical systems of scanning, which do not use" rotating elements but which, nevertheless, must accomplish rectilinear. scanning. For example,
  • the cathode dry tube is the source of light as well as the light valve, having in its simplestform a cathode I, a control grid 2, an
  • Lens 5 serves to focus the spot of light from A on screen 8 via the mirror surfaces of oscillographtype vibrator mirrors 8 and I which determine the path of the light. It will be clear from the description of Fig. 10 that vibrator 8 must act to deflect the light on the screen according to a sawtooth form at the line frequency and similarly vibrator I must cause the light to traverse the screen linearly from top to bottom and rapidly back to the top in saw-tooth form at the picture frequency. The angle through which the mirror surfaces turn and hence the motion of light on the screen is assumed to be directly proportional to the current through the vibrators and to the voltage applied; hence in each case, the actuating voltage required is; as indicated, of the form Fig. 80.
  • Fig. 2 a diagram of the receiver is shown wherein unit blocks serve to indicate broadly the functions of the various receiver parts.
  • the receiver illustrated is of the superheterodyne type -in that the incoming carrier wave and sidebands are collected by antenna structure 9, amplified by the ratio frequency amplifier l0, and applied to modulator II, together with heterodyne energy from oscillator [2, to produce an intermediate frequency carrier and sidebandswhich are amplified by the intermediate frequency amplifier i3 and applied to detector M.
  • the detector M develops the vision frequencies, which represent detail in the picture.
  • the cathode ray tube 70 is shown as having magnetic control cells L1, Li.
  • the generator unit l8 serves to generate and supply saw-tooth voltage (labeled 7 83a) of line frequency to the deflecting plates Pa,
  • the line frequency impulses and picture frequency impulses developed by detector ll are also applied to filter units (8 and I9.
  • Unit I8 is. for example, a lowpass filter suitable for passing the picture frequency impulse undistorted in wave form to unit 20 which is the picture impulse amplifier and which serves to apply the picture impulse prop-'- erly poled and in adjusted amplitude as a control or synchronizing voltage to 2
  • unit i8 is, for example. a band-pass filter to pass the line impulse to amplifier II which in turn serves to apply the line impulses properly poled and adjusted in amplitude as a control or synchronizing voltage to it.
  • the wave form of the synchronizing impulse's supplied by M to units It and I8 is similar to that shown in Fig. 8b so that this graph may be taken as the form of impulse from It applied to control generator it.
  • a line 111 is being traced on the screen, and during the interval u, t the retrace 11 occurs (the ratio of Similarly in Fig. 8b the control impulse endures for an interval v, w and is repeated after the trace interval w, v.
  • This ratio of intervals is also shown as 10:1.
  • the impulse peak at 11 occurs simultaneously with the end of the trace it in Fig. 4a. perfect synchronism is assured.
  • Non-linearity in the line traces would result in the traces (m in Fig.4) being curved and the picture detail would appear crowded together in some places and too widely spaced in others.
  • the illustration is more easily given when non-linearity exists in the picture trace, as shown in Figs. 5a to 51 inclusive.
  • the wave-form shown for the picture frequency is that of Fig. 3c and the proper uniform spacing of the picture lines which results are shown in the first corresponding pattern Fig. 5b.
  • the second pattern Fig. 50 indicates how the retraces are absent when proper synchronization of the picture frequency is achieved and "block-out occurs.
  • Fig. 5d indicates that the saw-tooth current from generator II is of exponential form in both trace and retrace and the subsequent crowding of the lines at the bottom of the picture is shown in pattern Fig. 5e. With correct synchronization the retrace lines are blocked out as shown in pattern Fig. 5/.
  • generator units l8 and M of Fig. 2 In that they must supply saw-tooth voltage or current as the case requires having good. linearity in the trace, adequate ratio of trace to retrace time, and proper response to synchronizing'control voltages.
  • the units l6 and H for the line control and I9 and for the picture control must fulfill two functions: (a) apply the synchronizing impulse undistorted and in proper amplitude and phase to units i8 and 2
  • Figs. 6a. to Go a number of fundamental circuits are shown for producing current and voltage wave forms related to the saw-tooth derivative series.
  • the circuits of Figs. 6a, b and 0 will be termed the R, C, type in that the desired wave form results from the charge and discharge of a condenser through resistance.
  • the circuits of Figs. 6d, e, j, and g. are termed the L/R type in that the wave form results from the flow of ,current through an inductance as affected by resistance.
  • a pendulum S periodically short circuits 9. capacity (I through resistance r"'for a brief interval of time during each swing to the left, owing to closure of switch a.
  • S is assumed to be actuated by some mechanism, as for example the usual clock eseapement, so that the frequency of recurring short circuits is here determined by S.
  • the voltage across C relative to ground and the current-through C are to a close approximation as shown in Figs. 7a and 7b," respectively.
  • the condenser C is exponentially charged from source E throughlresistance R at a rate determined'by thetime constant of the circuit which depends'on the,produ'ct ofaR and C.
  • the condenser C discharges through the resistance r at a ratedeplending upon the product oi. 1' and 'C.
  • the effect of the path through R on the rate of discharge condenser C cancbe neglected since R is large. compared with r.
  • the current through C, Fig. 7b. is the mathematical derivative of the voltage, Fig. 7a. It will be noted that the exponential saw-tooth voltage of Fig. 7a approximates the ideal form, Fig. 3c,
  • Fig. 7a in this case being the current through the inductance L and Fig. 7b being the voltage across the inductance.
  • the battery E supplies current through 1'. L and 0 during the trace part of the cycle.
  • the pendulum is here labeled 0 to indicate that it is an "opening" device instead of the shorting device! of Fig. 4a.
  • the contact to O is closed except during a brief interval during the end of the. swing of O to the right.
  • the circuit constants mentioned to satisfy Fig. 7, are
  • the current throughL increases slowly and exponentially during the trace part of the cycle according to the time constant L/r. During the retrace the current falls rapidly and exponentially according to the timeconstant L/R. It will be noted that during the retrace the part of the circuit which includes E and r can be neglected (i. e., considered as of zero resistance) since R is large compared with r. this assumption is very small.
  • the voltage across the coil is in this case the mathematical derivative of the currentthrough the inductance and is as shown in Fig. 7b.
  • Fig. 6b the same elements of the R, C type circuit are present with the exception that S in this case is a shorting device which acts to short circuit C through r when the voltage across has reached a predetermined maximum value.
  • S in this case is a shorting device which acts to short circuit C through r when the voltage across has reached a predetermined maximum value.
  • the same wave forms of voltage and current as shown by Fig. 7 result here if all circuit constants are the same as in Fig. 6a and if the device 8 closes when the value of voltage across C reaches a maximum of 150 volts, (1. e., when conversely the voltage between ground and point X has fallen to 150 volts) and opens when the voltage across C has fallen to 50 volts.
  • a typical relaxation" oscillator is this circuit in which is a gaseous discharge tube such as a Thyratron".
  • the operating voltages of S may be controlled and when once they are fixed the fundamental frequency of the circuit can be readily set by adjusting either C or R, or both. Also, 1' airects frequency as shown by the equation for the generated frequency given below.
  • V E V 1 2 C(R log -I-r log
  • I frequency in cycles per second
  • C capacitance in farads
  • V1 maximum i-n volts developed across R.
  • the device 0 is substituted for the. pendulum of 0 of Fig. 6d and is assumed to be a device normally closed or conductive and of zero resistance when closed, until the current through it reaches a predetermined maximum value at wh ch instant it opens to become non-conductive. If the conditions are prescribed that O is conductive for all currents less than 30 milliamperes but non-conductive for currents exceeding this value. then with the remaining circuit constants as given for Fig. 6d, the wave forms of Fig. '7 again apply: Fig. 7a representing the current through L and Fig. 7b the voltage across L. In practice, if the adjustment of 0 remains unchanged, the frequency can be controlled primarily by changing r or L, or both. The equation for frequency is as given below, and again for a fixed condition of O, the frequency can be varied without changingthe amplitude or output current through L.
  • the tube is therefore a constant current device and the charging of C through .H during the trace of the saw-tooth voltage cycle is therefore linear with time as desired.
  • the voltage across H (which is also that across C alone plus a direct current component) is as shown in Fig. 8a and the current through C is as shown in Fig. 8b which is the mathematical derivative of Fig. 8a.;
  • the frequency is:
  • a negative resistance -r may be introduced as is illustrated in Fig. 6).
  • Fig. 69 The equivalent of introducing a negative resistance r to maintain constant the voltage across L during the trace is shown in Fig. 69 where a generator (330 of saw-tooth voltage properly poled and adjusted in amplitude is introduced in series with r and L. If the resultant current through L is of saw-tooth wave form then the voltage drop across 1' will be of saw-tooth wave form, and hence the insertion of generator 630 will compensate for the voltage drop across r to maintainthe voltage across L constant during the trace.
  • Fig. 8a represents the current through L and Fig. 8b the voltage across L for this figure. Also the voltage across 0 is of impulse form since the sum of the voltage drops across 1', L, R and 33c must add up to the constant direct current voltage E.
  • the L/R circuit may be developed as an amplifier of an R, C generators output to produce saw-toothcurrent through scanning inductances.
  • Such circuit is indicated as L and R in series.
  • the pattern on the screen will be as shown in Fig. 9b. If the transmitters retrace endures for a time interval only one-half as long as that of the impulse component of this scanning wave, the picture retrace block-out will appear as shown in Fig. This blocks out that part of the picture retrace which lies across the field to be viewed and throws that part of the retrace which was not blocked out .above the field of view.
  • the current through the scanning coils can. of course. be made very large in the type of load circuit of Fig. 110 by having L and C resonant at, or near, the fundamental frequency of the wave form. Such a design. however, materially approximately exponential.
  • Fig. 110 the first. cycle shown is of form Fig. 30, indicated as the wave form of voltage e applied.
  • the current, and hence the voltage ea, Fig. 11c,. is shown as having approximately exponential trace and retrace.
  • the difference in voltage between e and e: is es which is of the which point it opens.
  • Fig. 3d (parabolic impulse) as shown of small amplitude in Fig. 111;.
  • this wave form is composed primarily of the lowfrequency fundamental and the lower harmonics; that is the amplitude ofthe harmonics decreases rapidly with frequency and henoe the observation that discrimination against the low frequency components tends to make the saw-tooth wave form appear exponential is confirmed.
  • a vacuum tube may be utilized in two fundamentally different ways to give saw-tooth current through an inductance (this statement being made without regard as to whether or not the voltage control applied to the grid is from a separate source or the result of a feedback).
  • the tube maybe employed as a linear amplifier to repeat the voltage applied to the control grid into the plate circuit as illustrated in our copending application Serial'No. 747,068, filed Oct. 5. 1934. Patent No. 2,052,183, granted August 25, 1936, or
  • vacuum tube 26 has voltage of impulse wave form e applied between its control grid and cathode.
  • a filter network '(band-pass) comprising elements 21, 28, 29, 30, 8
  • the voltage e: applied between control grid and cathode is illustrated as being of impulse wave form corresponding to Fig. 327.
  • the output voltage is a replica of the input voltage
  • the output voltage across Lin will be of impulse wave form and the current therein will be of saw-tooth form, Fig. 30, according to the derivative series.
  • Fig. 13b in which tube 28' is again excited by an impulse wave form eg.
  • the load is inductive.
  • C011 34 is assumed to be large compared with the scanning inductanceLsc and capacity 35 is large (low reactance to the scanning frequency) so that Lso is essentially the plate circuit load. If under these conditions tube of its characteristic then the current will not be saw-tooth in form through Lac, with the impulse excitation shown,.since a. voltage drop oc-' current when a large negative bias is employed, is A important.
  • tube 26 serves to close the plate circuit during the trace partof the cycle and opens it briefly during the negative impulse peakior the retrace.
  • the current through L under such conditions will be of saw-tooth form.
  • the traces will be exponential approaching linearity to air extent decapacity type circuits for supplying saw-tooth pendent upon the reduction in tube resistance and output circuit resistance.
  • Fig. 130 it will be clear that by using a combined impulse and saw-tooth wave form (as there illustrated) for the grid control voltage, current of saw-tooth wave form in the plate circuit can more readily be obtained.
  • a transformer 36, 3'! is employed to couple Lac in the plate circuit as an alternative of the capacity coupled arrangement of Fig. 132:.
  • the effective circuit resistance is represented by resistor 38. If tube 26 is operated as a linear amplifier a fixed value of plate-cathode resistance must be considered in series with resistance 39 and the inductive load. Under such conditions the sawtooth component required will be relatively large and the pollng of voltage e,; is immaterial.
  • tube 28 it is important that the impulse peaks be poled to be negative as applied to the grid of tube 26.
  • this tube opens the plate circult during the retrace when the grid is highly negative and. during the trace the saw-tooth component acts to compensate for the voltage drop due to tube and circuit resistance thereby holding the voltage across transformer 36, 31 constant and hence assuring good linearity of current traces through Lac.
  • Fig. 15 shows a complete circuit for carrying out the. arrangement of Fig. 13b, the impulse wave-form generator being one which has been v illustrated and described in our Patent No.
  • Voltage source E charges condenser 0 through constant current device, tube H; the value of charging current, and hence thc 'fre-,- quency, being controlled by the grid tap f which sets the bias,on the control grid ofI-I.
  • Short .circuiting tube S regenerated by the reversing tube Rv acts to short circuit condenser C when its potential has reached a predetermined value which will cause current to'start flowing between plate and cathode of tube S.
  • the current through tube S and hence through its plate rcsistor 40 is of impulse waveform as shown, for examplein Fig. via capacity ll and resistor 42 to the control grid of tube 26.
  • Fig. 16 a simplification of Fig. 15 is shown which in practice gives a current of quite good saw-tooth wave form through scanning inductance hi:- Rv fulfills also the function of an output tube.
  • rrent through tube S is of impulse wave form
  • the voltage across resistor 40 applied to the grid ortube R is of impulse wave form with the peaks .poled negatively.
  • the output circuit of tube R1) is similar to that of Figs. 13b and 15.
  • the current through L is of saw-tooth form and the voltage across Leo is of impulse form and properly poled so that when applied to the grid of tubes over connection 57 the impulse peaks are positive to regenerate tube S and accelerate the shorting of'capacity C.
  • the circuits of Figs. 15 and 16 are as noted, arranged to secure either the operation of Fig. 6d or that of Fig. 13b in that a separate generimpulse wave form is provided.
  • the circuit of Fig. 17 is particularly designed to function according to the principles of Fig. 68.
  • tube 26 acts as the opening anspvv device when the current in its plate circuit has reached a predetermined maximum. If current of saw-tooth wave form flows in the plate circuit of tube 28, the voltage across resistance 86 will be of saw-tooth form. No current flows between plate and'cathode of tube 8 until a predetermined voltage across resistor 66 is developed.
  • Tube 8 when the voltage across 88 has reached a value sufllcient to cause current to flow in tube 8, a negative voltage is developed at the grid of tube Rv, which tube in turn applies a positive voltage to the grid of 8. Tube 8 is therefore regenerated by tube R1: to cause tube 8 rapidly to short circuit resistor 88. Simultaneously a negative impulse from the plate of tube 8 is' applied to the control grid of tube 28, via the grid blocking condenser 88, and leak resistor 88. Tube 28 thus automatically opens the circuit when the current has reached a predetermined maximum value.
  • ning coils Lsc are coupled into the circuit through transformer 88, 87, in part to eliminate the direct current component, and to secure an impedance match for best performance by introducing an effective inductance into the plate circuit of tube 28 to give optimum results.
  • the circuit provides saw-tooth current of quite good wave form, slightly exponential as to traces. It is clear from Fig. 11 and its exposition, that the voltage across coil '86 is of impulse form, that across resistor 68 is of saw-tooth form, and the resultant as applied between grid and cathode of tube Rv via capacity 6
  • the tube Rv is a linear voltage amplifier for repeating the combined impulse and saw-tooth voltage in reversed polarity between the grid and cathode of tube 26 via capacity 68 and resistor 88.
  • a magnetic feedback may be utilized as shown by the addition of a third coil 88, Fig. 19, to the transformer 88, 81.
  • the voltage across the coil is of impulse wave form and hence, that across coil 84 is likewise of impulse wave form poled to apply the peaks negative to the grid of tube 28. Only the impulse and not the saw-tooth component is appliedback to the grid of tube 28.
  • the frequency is controllable by either an adjustable resistor 88 in the plate circuit, Fig. 19a, or by'resistor 88 in the grid circuit. When one of these resistors is used, the other may be omitted. In either case, an increase of resistance corresponds to an increase of the frequency generated.
  • a quite acceptable current of sawtooth wave form is obtained through the scanning coils he.
  • Fig. 19b differs from that of Fig. 19a only in that resistor 61 is employed in the cathode branch common to both plate and grid circuits. Increase of resistor 61 corresponds to increase in generated frequency and in general the performance of the Fig. 1% circuit is slightly superior to that of'Flg. 19a.
  • the circuits of Fig. 19 are moreeifective for high (line) frequency than for low (picture) frequency scanning.
  • circuits of Figs. 18 and 19 can be made to carry out the principles involved such, for example, as a combination arrangement of the two whereby a reversing tube will serve to perform a part of the feedback and a feedback coupling will serve to perform part of the feedback function.
  • the output circuit of tube 26 could, of course, be of the form shown as the output or plate circuit of Fig. 136 or 13c.
  • a resistor M in the cathode path gives negative regeneration. This output arrangement is most effective for low (picture) frequencies.
  • the negative regeneration element 73 has been found efiective in maintaining good linearity of the saw-tooth current. trace even when low frequency components areattenuated due to the reactance of capacity 12 (which should be as large a capacity as is feasible) and reaction throughthe power supply elements.
  • Fig. 21 the resistance-capacity type of generator employs a voltage source E charging capacity C through constant current tube H.
  • tube 26 may operate as an opening device as described in connection with Fig. 20.
  • the cathode of device H is above ground potential, and in prder that there shall be no relative changes at the generated frequency of voltage between screen grid and cathode, and between the control grid and cathode of tube H, the bias to the control grid, which determines the generated frequency, is furnished by the direct current voltage drop across potentiometer I9 and the direct current potential to the screen grid is through resistor 18.
  • Capacity 11 connects the screen of tube H to its cathode and the time constant of the resistance-capacity branch II, 11 is made to correspond to a frequency lower than the fundamental frequency generated, so that the voltage between screen and cathode remains constant.
  • the bias for the control grid tube H maybe secured by connecting its grid througha resistor to a tap on E, and providing a capacity path from control grid to cathode instead of employing 19 as shown.
  • the only adverse criticism to such a connection is that the response 01' the circuit to any change of bias on the control grid for setting the generated frequency is sluggish, due to the time constant 01' the resistor-capacity circuit suggested, which may be made low.
  • the impulse voltage drop across resistor 78 is applied to the grid of tube Rv poled to make its grid, during the impulse peaks, negative with respect to its cathode, and that tube Rv in turn applies an impulse voltage to the grid of tube S poled to make its grid, during the impulse peaks, positive with respect to its cathode.
  • Tube Ru thus regenerates S to expedite the shorting of condenser C during the retrace part of the cycle.
  • the resultant impulse voltage across resistor 16 and saw-tooth voltage across condenser C are a combined impulse plus saw-tooth voltage properly poled to be applied to the grid of tube 28 through 69 and 7755 so that the action from there on is like that already described for Fig. 20.
  • a resistance-capacity generator inverted to give a properly poled voltage of combined impulse plus saw-tooth wave form applied to the grid of output tube 26.
  • voltage source E charges ated by feedback transformer T instead of by a reversing vacuum tube.
  • Resistor 8t (as in Fig. 14) damps the transformer T to prevent spurious oscillation which may occur due to the circuit constants and distributed capacities of T and S.
  • a resultant voltage having an impulse component due to the voltage drop across resistor 15 and a saw-tooth component due tothe voltage drop across condenser C is applied to the control grid of tube 26 through capacity 59 and potentiometer ill.
  • Saw-tooth current flows in output scanning coils Lie as discussed in connection with Fig. 20.
  • the branch 59, Iii should be of high impedance to prevent its acting as an appreciable load on the generator part of the circuit, and it should provide good fidelity (i. e., a low time constant as determined by capacity 59 and resistor 10) to 'apply the generated voltage wave form undising for the pendulum arrangement 0 there shown, a mechanical interrupter 0 controlled by a vacuum tube oscillator acting as the frequency determining source.
  • a vacuum tube oscillator acting as the frequency determining source.
  • lating circuit for tube is of a typical form comprising a tuned grid circuit and feedback winding in the plate circuit.
  • the voltage developed in the plate circuit winding is applied to coil 8i
  • the particular form of the contact 0 may, for example, be of the vacuum tube type to reduce the effects of sparking at the contact.
  • FIG. 24 an L/R. type of saw-tooth current generator is shown which employs the negative resistance characteristic of the dynatron to effect its operation.
  • tube 88 has a voltage source E applied between cathode and one grid acting as the anode.
  • a direct current bias adjustment, labeled 1, on the grid nearer the cathode serves to determine the slope of the negative resistance characteristic at which operation occurs and also to control the generated frequency.
  • Scanning coil Lsc may be directly introduced in the plate circuit or coupled therein by transformer winding 88, 31 as shown.
  • Resistor 08 represents the resistance introduced by 38, 81, and L which would be made as low as possible.
  • the distributed capacities related to winding 38, 31 and Lao should be kept low.
  • the control of frequency by adjustment of the negative bias at I is effective in increasing frequency as the bias is increased.
  • Resistance introduced in the anode (screen) circuit also increases the generated frequency.
  • Fig. 24 is in practice an economical and efficient generator of current of saw-tooth wave form through the scanning inductances. It is particularly suited to the generation of high (line) frequencies. Synchronization can be achieved by applying the impulses of the synchronizing signal to frequency control grid.
  • any of the generator units here shown may be substituted and co-ordinated to serve as the units i8 and II of Fig. 2 in a complete receiver and projector of television images.
  • a first vacuum tube having grid and plate circuits, means supplying direct current operating potentials to electrodes of said tube, said plate circuit containing inductance and a resistor in series, and means producing in said inductance a current of sawtooth wave form having retrace intervals of short duration relative to the trace intervals, said means comprising, a connection shunting said resistor and containing the space path of a second vacuum tube arranged to pass current when the voltage across said resistor reaches a predetermined value, a capacitive coupling from the grid of the first tube to the plate of the second, and a third vacuum tube regeneratively coupling the input of said second tube to its output, whereby a negative potential is applied to the grid of the first tube from the plate of the second upon occurrence of said predetermined maximum voltage across said resistor thereby to accelerate retrace of said saw-tooth current.
  • a first vacuum tube and a second vacuum tube each having input and output elements, an output load for said first tube comprising inductance and a first resistance in series, means for coupling the output of said first tube to the input of the second tube, means including a second resistance and capacity coupling the output of the second tube to the input of the first tube to provide regenerative feedback in which the frequency determining elements are essentiallysaid inductance and said first resistance whereby the voltage across said inductance is of impulse wave form and the current therein is essentially of saw-tooth wave form, and means for adjusting said first resistance to control the .generated frequency.
  • said vacuum tube being actuated by current in a said circuits to periodically open said output circult for only a small fraction of each cycle and the winding polarities being such as to provide regeneration between said input and output circuits, a variable resistance included in at least one of said circuits, said resistance and the inductance of said transformer winding in the last said circuit being proportioned to determine the periodicity of the generated wave, means for adjusting said resistance to control said periodicity and means for coupling said third winding to the scanning inductance.
  • a circuit effectively including said scanning inductance and comprising. in series, inductance means, resistance means, a normally fully conductive circuit controlling device, and a source of operating voltage for said circuit, means responsive to operating conditions in said circuit for periodically rendering said device substantially completely nonconductive for only a small fraction of each cycle and means for adjusting said resistance means to control the periodicity of said generator.
  • a circuit effectively including said scanning inductance and comprising, in series, inductance means, resistance means, a normally fully conductive circuit controlling device comprising the space-current path of a vacuum tube, and a source of operating voltage for said circuit, means responsive to a predetermined current through said circuit for periodically rendering said device substantially completely non-conductive for only a small fraction of each cycle and means for adjusting said resistance means to control the periodicity of said generator.
  • a circuit effectively including said scanning inductance and comprising, in series, inductance means, resistance means, anormally fully conductive circuit controlling device including the space-current path of a vacuum tube, and a source of operating voltage for said circuit, means responsive to operating conditions in said circuit for periodically rendering said device substantially completely non-conductive for only a small fraction of each cycle and means for adjusting said resistance means to control the periodicity of said generator.
  • inductance means in series, inductance means, resistance means, a normally fully conductive circuit controlling device including the space-current path of a vacuum tube, and a source of operating voltage for said circuit, vacuum tube means responsive to operating conditions in said circuit for periodically rendering said device substantially completely non-conductive for only a small fraction. 01 each cycle and means for adjusting said resistance means to control theperiodicity of said generator.
  • a circuit efiectiveiy in eluding said scanning inductance comprising, in series, inductance means, resistance means, a normally fully conductive circuit controlling device, and a source of operating voltage for said

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Details Of Television Scanning (AREA)
  • Investigating Or Analyzing Materials By The Use Of Magnetic Means (AREA)
US747324A 1934-10-08 1934-10-08 Television apparatus Expired - Lifetime US2118977A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
BE411652D BE411652A (enMihai) 1934-10-08
US747324A US2118977A (en) 1934-10-08 1934-10-08 Television apparatus
GB26502/35A GB468057A (en) 1934-10-08 1935-09-24 Improvements in the generation of scanning waves for television apparatus
FR796194D FR796194A (fr) 1934-10-08 1935-10-08 Disposition pour la reproduction d'images de télévision

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US747324A US2118977A (en) 1934-10-08 1934-10-08 Television apparatus

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US2118977A true US2118977A (en) 1938-05-31

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2433758A (en) * 1940-01-25 1947-12-30 Rca Corp Radio pulse generator
US2441334A (en) * 1943-04-30 1948-05-11 Du Mont Allen B Lab Inc Signal level and phase control
US2485569A (en) * 1945-03-15 1949-10-25 Francis T Coughlin Method of and apparatus for compensating for residual magnetization in cathode-ray apparatus
US2509761A (en) * 1948-03-16 1950-05-30 Motorola Inc Saw-tooth voltage generator
US2521008A (en) * 1944-06-27 1950-09-05 John H Homrighous Television and sound multiplex system
US2728875A (en) * 1953-09-01 1955-12-27 Rca Corp Raster size control

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2433758A (en) * 1940-01-25 1947-12-30 Rca Corp Radio pulse generator
US2441334A (en) * 1943-04-30 1948-05-11 Du Mont Allen B Lab Inc Signal level and phase control
US2521008A (en) * 1944-06-27 1950-09-05 John H Homrighous Television and sound multiplex system
US2485569A (en) * 1945-03-15 1949-10-25 Francis T Coughlin Method of and apparatus for compensating for residual magnetization in cathode-ray apparatus
US2509761A (en) * 1948-03-16 1950-05-30 Motorola Inc Saw-tooth voltage generator
US2728875A (en) * 1953-09-01 1955-12-27 Rca Corp Raster size control

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GB468057A (en) 1937-06-21
FR796194A (fr) 1936-03-31
BE411652A (enMihai)

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