US2264781A - Periodic wave generator - Google Patents

Description

2 m43 H. A. WHEELER PERIODIC WAVE GENERATOR Filed March 29, 1939 INVENTOR H ROLD A. WHEELER Bf ATTORNEY ?atented Dec. 2, 1941 orifice 1 ramonrc WAVE GENERATOR Harold A. Wheeler, Great Neck,; N. Y., assignor tov Hazeltine Corporation, a corporation of Dela- Wall'e Application March 29, 193s, semina. 264,716

` (ci. 25o-36) 10 Claims.

This invention relates to periodic wave gen: erators and, while of general application, it. is especially useful in the development of scanning elds of saw-tooth wave form for use in television systems.

Periodic waves having complexpwa've forms, such as saw-tooth and related forms, are useful for various purposes. In television systems, for example, at both the transmitter and the receiver, electrostatic or electromagnetic fields of sawtooth Wave form are utilized in scanning systems to deflect a beam focused on a target, such as the cathode ray in a cathode-ray tube system, so as to cause the beam to scan successive fields or series of parallel lines on the target. Theseelds are produced by applying periodic current or voltage waves of the desired wave form to field-l producing elements.

In general, it is required that periodic wave generators of the type described be capable of developing waves of precisely the desired wave form; in a television system, of a form suitable to eect accurately uniform velocity of trace and rapid retrace of the scanningV beam, that is, a saw-tooth wave comprising a linear trace stroke and a retrace stroke of only a fraction offthe duration of trace stroke.' Further characteristics generator includes a lfeed-back circuit for the tube responsive to operating conditions in the output circuit for effecting operation of the tube over the aforesaid part of its operating range and one of the limiting regions and for causing the tube to develop in the output circuit a current wave including both saw-tooth and pulse components. The generator additionally n-g' cludes means connected in circuit and cooperatessential to such generators are simplicity ofconstruction and dependability inv operation.

It is an object of the present invention, therefore, to provide an improved generator for developing a periodic wave of complex wave form, such as a saw-tooth or related form, which may be either a current wave for electromagnetic scanning or a voltage wave for electrostatic scanning.

It is a further object of the invention to pro.-

vide a periodic wave generator having one or more of the desirable characteristics and features referred to above.

In accordance with the present invention, a

Ygenerator of periodic saw-tooth waves having means from the supply circuit by substantially.

constant current in one direction during the trace periods and discharging of the capacitance v means by current in the opposite direction during retrace periods. The vacuum tube has a grid voltage-conductance characteristic free from excessive curvature over a part of its operating range between limiting regions thereof.' The ing with the capacitance means for dividing the aforesaid current in two paths, one of the paths including the capacitance means. The impedances of the aforesaid paths are relatively so proportioned that there flows through the capacitance means only the one of the aforesaid current components required `to produce the desired saw-tooth wave therein with the tube. operating only over the aforesaid part of its operating range during trace periods. a .5'

For a better understanding of the invention,

together with other and furtherv objects thereof, reference is had to the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims.

\ In the accompanying drawing, Fig. 1 is a circuit diagram of a periodic wave generator em-A .bodying the present invention; Fig. 2 is a circuitv diagram of a modified form of the output circuit of the generator of Fig. 1; Figs'. 3 and 4 are circuit diagrams of modified forms of periodic wave generators embodying the invention: while Fig. 5 is a group of curves illustrating thel wave forms o f various currents and voltages developed in the generator of Fig. 1.

Referring now more particularly to Fig. 1 of the drawing, the generator illustrated comprises an energy-storage means, such as an inductance element t0, which may be a magnetic scanning element of a television scanning system, through which it vis desired to produce acurrent of sawtooth wave form. The inductance element I0 is included in the output circuit of the generator in series with a resistor H, which may comprise, in.V whole or in part, the inherent resistance of the inductance element, a blocking condenser I2, a' j source of operating voltage, such as a' battery I3, and a repeater device, preferably a vacuum tube I4 which may be a triode, as shown, or a multi-- grid tube. For the purpose of controlling certain operating conditions of the system in accordance with the present invention and for applying the operating potential from battery I3 to the anode of the tube I4, a resistor I5' is connected Ain parallel with the series-connected inoi!l resistors I8 and ila lso that only'a' ductance-element Il. resistor II, and condenser I2. Since the resistor I l carries the space current of tube i4, it must be limited to a fairly small resistance value 'and anl inductancey element l may be included in seriesy therewith, asl

' shown, although, in some cases, this element may be omitted. y n

For the purpose of controlling the tube Il, there is provided ar feed-back system responsive 'f to operating conditions in the output circuit of the generator and comprising a reversing and limiting vacuum tube I6 whichmay be a triode, as shown, or a multigrid tube. The input cir-v cuit of the tube I8 is coupled to the loadcircuit of tube Il by way oi' a coupling impedance in'- cluding a series-connected condenser I1 and voltage-divider resistors I8, Ita, and lsb, the control grid of tube I6 being connected at the Junction portion of the available feed-back `voltage -is applied to the tube It. yThe condenser I1 serves to absorb saw-tooth wave-form components from the feedn back voltage so that only pulse components.

' thereof are appliedto the'tube I8. Tube I6 is arranged to operate beyond both its upper and lower cutoff limits so asltol derive .inl its load 'circuit,presently to be described,A a voltage o! lthe lrequired wave form and'amplitude properly to stabilize the operation of the system. Positive i synchronizing pulses for the generator may bel 1 applied to the potential may be supplied from a suitable source. for example, ya battery 23, by way lof a resistor 2| and the load resistor 2|. The load circuit 2|', 22 iscoupled to the control grid of the tube Il by way oia suitable condenser 25 and gridleak resistor 2i. A negative-bias potential is applied to the control grid of the tube Il by way of the resistor from a suitable source, for example, battery 21. While. for simplification, batteries have been illustrated as sources of direct current and bias-voltage supply, it will be understood that, in practice, conventional power supply circuits will ordinarily be utilized.

'I'he operation of the generator of Fig. 1 may best be understood by first neglecting the resistor I5 and the major Apart of the resistor 2|, which comprise essential parts of the present invention, and assuming the former to be replaced by a large choke to carry the space current oi.' tube Il. During the trace period of each cycle, the tube I8 is biased below grid-bias cutoi! and the condenser 22 is charged through the resistor. 24 causing the potential of the upper terminal of the condenser 22, which potential is applied to the control grid of the tube Il, to beco e increasingly positive so that vcurrent bui s up through the series circuit including the tube I4 and inductance element I0. 'This current continues to rise until the operating conditions are disturbed, for example, by the application of a positive synchronizing pulse to the tube I6, which initiates the retrace portion of the cycle. Buchl pulse causes the potential of the control grid of the tube Il to increase negatively, reducing itsoutput current. This reduction in current is reas just described, so

voltage of the required waveyform.- Operating' y cluding tube I6.

f ates not only over oi'. its characteristic 'but also over 1 the lowery generated by means of the feed-back circuit in- As long as the current in the tube Il continues to fall, a positive voltage is fed back tor the tube I6.A The tube 'I4l is thus. regenerated to cutoiif. As soon as the current in the tube Il' is interrupted, the positive feed-back voltagefis removed from'thetube I6 and it returns to cutoff. The trace period described above is then repeated to initiate the next cycle. f

While the grid voltage-conductance characteristic cfa repeater, such as the is substantially linear over the intermediate portion of its range, or at least does not have excessive curvature, the limiting or upper and lower Lcutoff! regions oi' the range are sharply curved.

The synchronizing signal determines the termination of the trace periods and, hence, the upper limit of the operating range. The'circuit con-l stants are preferably so related to the period of the synchronizing signal thatl this upper limit is just within the linear portion o! the tube charfacteristic. However, with the system operating, lthat the current through the tube Il is reduced to zero'at the lend lofthe retrace period, it will be seen that the tube operthe usefull intermediate portion sharply curved limiting region in the early part lof the trace period. l

In accordance with 'the present invention, however, there are provided means for shifting the operation of the device substantially away from this lower limiting-regionduring the entire. trace period. This is ac current component complished by causing a pulseto be superimposed on the desired saw-tooth current'component in the generator output circuit. For this purpose the resistor 2|., included in the load circuit of the tube Il, is given a substantial valuel so thatl there isl developed 'across this circuit and applied to the f control grid of the' tube Il a composite control voltage wave including not only' the saw-tooth -wave component developed across condenser 22 but also a pulse component developed across the resistor 2| which is of a value greater than needed for the development of saw-tooth current in the tube I4. Since it is necessary that only the saw-tooth current component passes through the inductance element ||I.1the`resistor Il is connected in parallel therewith andiso proportioned relative thereto that it eiiectively by-passes all of the pulse-current component and, incidentally, part of the saw-tooth current component.

rlihe actual operation of the system, therefore, 'is modiiied with respect to that described above. In Fig. 5 curves A-D, inclusive, illustrate voltages and currents developed at various points in thesystem during the actual operation thereof.

Thus, curve A illustrates the desired saw-tooth saw-tooth current therethrough so that the total voltage developed across the load circuit of tube Il by the saw-toothload current is of the combined saw-tooth and pulse wave form illustrated by curve C. The current through the resistor I5, therefore, and inductance 0, where such is ncluded in the circuit, is also of saw-tooth and pulse wave form. yThe total current which must be passed by the tube I4, therefore, is oi' the wave form illustrated by curve D, having both pulse n and saw-toothloomponents. Current of this revacuum tube Il,

veloped thereby and applied to the control grid of the tube I4. The end of the trace period, as explained above, is determined below the upper limiting region bythe application of the synchronizing pulse to the generator. During the retrace period the combined pulse and saw-tooth retrace components carry the tube through the lower limiting regionoi its repeating lcharacteristic to cutoiI and the tube thereupon swings away from this lower limiting region so that the trace period begins in and extends over the intermediate part of the range of the characteristic which is free from excessive curvature.

In certain casesit may be necessary for the resistor I to be of a relatively low value in order properly to carry the direct current. In such a case. in the absence of the inductance 9, the

path including resistor I5 would take an excessive amount of the pulse current. 'I'he inductance 8, however, may be included, as shown, for the purpose of providing greater impedance to the pulse current when the resistor is of such low value.

It will be appreciated that the grid voltageconductance characteristic of the tube I4 tends to cause curvature of the saw-tooth wave form of the current developed by the-system during the trace period. Likewise, certain impedance elements in the system tend to cause such a curvature; for example, the condenser I2, to'- gether with the other load circuit elements connected therewith, the resistor 28 and condenser 25, and the resistor 24 anl condenser 22. 'I'he curvature which these impedance elements tend to cause, however, is opposite to that due to the tube Il and the circuit constants are so proportioned that these Opposite curvature eilects compensate each other. Thus, while the condenser I2 has so large a capacitance that it does not greatly affect the wave form oi' the wave developed by the system, any curvature eilected thereby is galanced against the characteristic of the ubeI While a voltage oi' both pulse and saw-toothl wave-form components is impressed upon the feed-back circuit, the saw-tooth components are absorbed, as explained above, by the condenser I1 and only the pulse components are applied to the input circuit oi' tube I8. Tube II being operated beyond both its upper and lower cutofl' limits, a pure pulse current is developed thereby4 and the control voltage oi' the required complex wave form is developed across its load circuit comprising resistor 2| and condenser 22.v Not only does the limiting action of the tube I8 properly limit the amplitude of the control wave but it serves also to avoid cumulative wave-form distortion and thus stabilizes thewave form and amplitude of the wave developed by the system.

In order that the tube Il may simultaneously supply pure saw-toothfeurrentntoftheload inductance l0 and a pulse and saw-'tooth'current inresistor I5, the time constant of the coupling impedance 2l, 22 is made equal to that of the output circuit as follows:

in which C, R, and L are the capacitance, resistance, and inductance, respectively, ot the particular elements indicated by the appended numerals. Ihis relation is based on the assumption oi' a linear grid voltage-conductance characteristic in the tube I4 which is approximately realized v over the major portion of its operating range.

In order to procure a pure pulse voltage across the resistors I la and I8b, the condenser Il is proportioned, 'as explained, to absorb the saw-tooth voltage developed across the resistor Il in the output circuit as follows:

CHRF

in which, as in Equation 1, C, R, and L are the4 and beginning of the retrace period; the remain` ing characteristic of the wave, the duration oi' the retrace period, is determined by the tube Il reaching cutoil', whereupon the tube I4 is instantaneously swung away from the cutofi' region to begin the trace period.

It will be seen that, in accordance with one aspect of the present invention, impedance means, in the system of Fig. 1 the resistor I5, effeetively is connected in parallel and cooperates with the energy-storage means to divide the current through the output circuit into two paths. One of the paths includes the energy-storage means, the inductance element lli in Fig. 1, while the other path includes the impedance means 9, I5. The paths are so proportioned that there ilows through the energy-storage means only the current components required to produce the desired saw-tooth wave which, in the generator of Fig. 1, is the current o! saw-tooth wave form.

In Figs. 2, 3, and 4, there are illustrated modications of the invention. Like reference numerals indicate corresponding parts in Figs.' 1 4, inclusive.

In Fig. 2 there is illustrated a modified form of output circuit which may' be;4 substituted for the corresponding circuit in the generator of Fig. l. In the circuit of F1g.2. a resistor Iia is connected directly across the inductance element III andresistor II and an inductance element or choke 28, of the iron-core type, is connected in parallel with the circuit with its lower terminal at the inner side of condenser I2, providing a separate direct-current path for the space current o! the tube I4. Since, with this arrangement, the shunt resistor I 5a does notl carry the space current of the tube I4, with resultant voltage drop, as in the case of the resistor I5 of Fig. l, the resistor Ia. may be made any size desired without aecting the space current or anode voltage of tube Il and required battery voltage is less. c

In Fig. 3 a modiiled iorm of the generator of Fig. l is shown' which includes certain additional advantageous features whereby various operating characteristics. of the system may be readily adjusted. Except, as explained below, the generator of Fig. 3 is of the same construction as that of Fig. 1. In the generator oi' 3 a single battery I3a is provided for supplying the operating potentials oi' both oi' the tubes Il and I 8, these potentials being applied by way of anadjustable tube I6 by way of resistors 24 and 2Ia,

. plitude which is connected to the anode of the latter preferably being adjustable, as shown. Resistor 34 is connected tothe 4anode of tube I4 by way of resistor I5. A voltage-divider resistor is connected across battery |30. and resistor 34 and has an adjustable tap to which the resistor II is connected. The condenser I2 in this case is connected directly between the lower end of resistor II and the cathode of tube I4. A biasing resistor 36 is included in the cathode circuit of tube I4 and an adjustable biasing resistor 31, by-passed by a condenser 38, is included in the cathode circuit of tube I6. Condenser 22' may resistor 34 be alternatively connected directly to the cathode of tube I6, instead of to ground. This alternative connection 'has the advantage of returning the pulse of output current of tube I6 directly to the cathode andV thereby reducing the requirements ofthe by-pass condenser 38. The grid-leak resistor 26a of tube I4 is also adjustable.

The operation of this generator is substantially the same as that of the generator of Fig. 1. Here, however, the various adjustable resistors provide means whereby the various operating characteristics of the generator may be readily adjusted. By adjustment of the resistor 34, the amplitude of the wave developed-by the system may be readily controlled. When increased voltage is applied 4to the ytube I4 for developing a wave of greater amplitude, an increased control voltage is required to -be developed by the tube I6 so that its operating voltage should also beA increased. The resistor 34 thus provides a single means which may be adjusted simultaneously to effect the proper adjustments of the operating voltages of both tubes. 4 l

By adjustment of the tap on the voltagedivider resistor 35, the value of the direct-current component which flows through the inductance I0 may be readily controlled. Where the element I0 constitutes a scanning element of a cathode-ray tube, therefore, this adjustment is useful for vthe purpose of centering the scanning pattern on the target of the tube. Adjustment of the resistor 2 la serves to control the arnplitude of the pulse component'of the control wave developed by the feed-back system. This provides a means for accurately controlling the curvature of the wave developed by the generator at the beginning of itsv trace period. A further control of the linearity or curvature of the wave developed by the generator is provided by the adjustable resistor 26a. Thus, the adjustable resistor 34 comprises means for adjusting the amof the Wave developed by the generator, the amplitude adjustment being independent of the linearity and frequency of the developed wave, and the adjustable resistors Zia and 23a comprise means for adjusting the linearity of the ywave developed by the generator, the linearity adjustment being independent of the amplitude and frequency of the developed wave.

The free oscillating frequency of the generator of Fig. 3 is regulated by the time constant of resistor 31 and condenser 38, which determines the end of the trace period'in the absence of a synchronizing pulse. As stated above, the end of the trace period is determined by the starting of current in tube I6. The operation of tube I6 inFig. 3 is determined partly by resistor 31; that is, each pulse of current develops a bias across the condenser leaks off through the resistor 31 during the trace 38 which is applied positively to the cathode of tube I6, and this bias partially period. As it leaks oir, it reaches a point where current starts to now in tube I3, even inthe absence of a synchronizing pulse, whereupon the trace period is ended and retrace begins; that is, a saw-tooth control voltage is ldeveloped across the circuit 31, 38. 'I'he time constant of resistor 31 and condenser 38 is adjusted so thatI the free oscillation period is slightly longer than the synchronizing period, so that the failure of a single synchronizing pulse will not result in too great a disturbance of the normal periodicity of the generator. Thus, the resistor 31 and condenser 38 comprise means for adjusting the free oscillating frequency of the generator, .the frequency adjustment being independent of the amplitude and linearity-of the developed Wave.

The circuit constants of `a generator such as illustrated in Fig. 3 which have proved highly satisfactory in actual practice are as follows:

For improved linearity of trace, the following valuesmay be used in place of those above:

Resistor 31= 2,700 ohms Resistor 2|=7,000 ohms Resistor 36=800 ohms Resistor ISL- 1,500 ohms Condenser 38:1 microfarad Condenser 25:0.25 microfarad Condenser I 2:8 microfarads ator, an important advantage is obtained, since at such low frequencies effective inductance coils are generally large and expensive.

In Fig. 4 there is illustrated still another modied form of the generator of the present invention which is designed to develop a saw-tooth voltage wave across capacitance means. The generator of Fig. 4 is similar to that oi Fig. l except for the output circuit and certain details of the circuits of tubes I4 and I8. Here the energystorage means comprises capacitance means including series-connected condensers 48, 46, grounded at their junction, and a condenser Ilia in parallelV therewith which may be the deilecting plates of a television cathode-ray tube, providing a balanced output circuit. For building up a saw-tooth voltage from a saw-tooth current,

resistors 40, 40 are connected across the con- V densers 46, 46 and Illa and their junction is grounded by way of a battery |3b. The uncommon terminals of resistors 40 are connected across the tube I4 .by way of coupling condensers 4|, 4|, anode resistor 42, a. biasing resistor 43, and by-pass condenser 44 included in the cathode circuit of the tube. Anod'e potential is supplied to the tube I4 from a suitable tap on thebattery I3b by Way of a choke 45 and the resistor 42, and the direct-current path of the battery is completed by a similar choke 45a connected between the negative or grounded terminal of the battery and the cathode resistor 43. Chokes 45 and 45a are preferably of the same inductance and may be wound on the same core.V

Balancingcondensers 46 are eiective *tol bypass pulse-current components in the output circuit to supplement the capacitance IIla.

Anode potentialxfor the tube I6 is supplied from the battery I3b by way of a series resistor 41, by-pass condenser 48, and the resistors 24 and 2|. A self-biasing resistor 49 and by-pass condenser 5I) are included in the cathode circuit of the tube I6 and the lower terminals of these elements and the input circuit resistor I8b are grounded, by way of the common low potential lead of the system and the choke 45a. For the Y purpose of applying synchronizing pulses to the tube I6, there is provided an input transformer 5I having its secondary Winding conmc'cted across the resistor |817, the terminals 20a, 20a of its primary winding being suitable for receiving the synchronizing wave.

1n the generator of Fig. 4, as in Fig. l, the Various circuit elements are proportioned, so that the characteristic curvature of the tube I4 and that of the circuit elements, which tend to cause curvature of the saw-tooth wave developed by the system, effectively counteract each other during the trace period. Here the condensers 4| and inductance elements 45 and 45a are included in the group of elements whose values are proportioned for this purpose.

The operation of the generator of Fig. 4 is similar to that of Fig. 1 except that here a balanced voltage of saw-tooth wave form is required to be developed across the capacitance means instead of a current of saw-tooth wave form through an inductanoe element. A pulse voltage component the current ows, and second,` the path provided by resistors 40 throughwhich the saw-tooth current flows. That is, the battery I3b and the tube f I4 comprise means including a voltage supply wise be excessive at low frequencies.

, circuit and a vacuum tube for effecting periodic charging of the capacitance means from the supply circuit by substantially constant current in one direction during the trace periods and discharging of lthe capacitance means by current `flow in the opposite direction during the retrace periods. Negligible current flows through the coils 45, 45a and the resistor 41, except for the direct-current components. Negligible voltage :is developed across condensers 4|, 4|. This division of current is inevitable since a saw-tooth Voltage is produced across the condenser Illa, and, therefore, across resistors 46 and condensers 46.. In this case, the energy-storage means is not only the condenser Illa of the useful load circuit but also the condensers 46, 46, which 4are added for the practical reason of 'reducing theimpedance of the output circuit, which would othermary, it will be seen that the arrangement of Fig. 4 comprises a generator of periodic sawl tooth waves having substantially linear trace and vrelatively short retrace periods. The vacuum tube I4 of the Fig. 4 arrangement has, like the corresponding vacuum tube I4 of the Fig. 1 arrangement, a grid voltage-conductance characteristic free from excessive curvature over a part of its operating range between limiting regions thereof. Reversing vacuum tube I6 and the circuit elements I'I, I8, I8a, I8b, 2|, 22 and 24 compriseY a feed-back circuit for Athe vacuum tube I4 responsive to operating conditions in the output circuit of the latter tube for effecting operation of the vacuum tube I4 over the curvature-free portion of its operating range and one of the limiting regions thereof and for causing this vacuum tube to develop in its output circuit a current wave including both saw-tooth and pulse components.

l, voltage of vacuum tube I4 a feed-back voltage is also required for the feed-back circuit, as in the circuit of Fig. l. Therefore, a resultant voltage of saw-tooth and pulse wave form must be developed across the output circuit of the generator. The desired saw-tooth voltage appears across the capacitance means "Illa and current of due to the flow of current therethrough, the required Afeedback pulse voltage component, since otherwise there would be only the desired sawtooth voltage across the output circuit.

Thus, in the generator of Fig. 4, it will be apparent that means are provided whereby the output current is divided between two paths, iirst, the capacitive path including condensers I 0a and 46, 46, through which the pulse component of having saw-tooth and pulse wave-form components of relative amplitudes independent of those of the aforesaid output voltage. The-resistors 40, 4I! comprise means connected in circuit and cooperating with the capacitance means Illa for dividing the current in the output of vacuum tube I4 into two paths, one of which paths includes the capacitance means 10a, and the impedance of the paths are relatively so proportioned that there Hows through the capacitance means Illa only the one of the current components required to produce the desired saw-tooth wave therein with the vacuum tube I4 operating only over the curvature-free portion of its operating range during trace periods.

While there has been described what is at present considered to be the preferred embodiment of this invention, it will be obvious to those skilled in 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:

l. A generator of periodic saw-tooth waves having substantially linear trace and relatively cuit including capacitance means, means including a voltage supply circuit and a vacuum tube for effecting periodic charging of said capacitance` means from said supply circuit by substantially constant current in one direction during said trace periods and discharging of said capacitance means by current in the opposite direction during said retrace periods, said vacuum tube having a grid voltage-conductancer characteristic free from excessive curvature over a part of its operating range between limiting regions thereof, a feed-back circuit for said tube responsive to cperating conditions in said output circuit for effecting operation of said tube over said part of said range and one of said limiting regions and for causing said tube to develop in said output circuit a current wave including both saw-tooth and pulse components, and means connected in circuit and cooperating with said capacitance means for dividing said current in two paths, one of said paths including said capacitance means, and the impedances of said paths being relatively so proportioned that there flows through said capacitance means only the one of said current components required to produce the desired sawtooth wave therein with said tube operating only over said part of said range during trace periods.

2. A generator of periodic saw-tooth waves having substantially linear trace and relatively short retrace periods comprising, an output circuit including capacitance means, means including a voltage supply circuit and a vacuum tube for effecting periodic charging of said capacitance means from said supply circuit by substantially constant current in one direction during said trace periods and discharging of said capacitance means by current flow in the opposite direction during said retrace periods, said vacuum tube having a. desired grid voltage-conductance characteristic free from excessive curvature over a part of its operating range between relatively sharply curved limiting regions thereof, a feedback circuit for said tube responsive to operating conditions in said output circuit for controlling said tube to cause operation thereof over said part of said range and at least one of said limiting regions, and means including resistance means eiectively coupled to said capacitance means and so proportioned with respect thereto as to shift the operation of said tube substantially away from said limiting region during trace periods.

3. A generator of periodic saw-tooth Waves having substantially linear trace and relatively short retrace periods comprising, an output circuit including capacitance means, means including a current supply circuit and a vacuum tube for eiecting periodic iiow of substantially constant current in one direction through said capacitance means from said supply circuit during said trace periods, said vacuum tube having a grid voltage-conductance characteristic free from excessive curvature over a part of its operating range between limiting regions thereof, a feed-back circuit for said tube responsive to operating conditions in said output circuit for effecting operation of said tube over said part of said range and one of said hunting regions to cause in said output circuit a current wave including both saw-tooth and pulse components,l

and means connected in circuit and cooperating with said capacitance means for dividing said current in two paths, one of said paths including said capacitance means and the other of said paths including resistance means and said paths being so proportioned that there nows through said one path only said current components of pulse wave form with said tube operating over said part of its range during trace periods.

4. A generator of periodic saw-tooth waves having substantially linear trace and relatively short retrace periods comprising, an output circuit including capacitance means, means including an energy supply circuit and a vacuum-tube repeater having a control electrode for effecting periodic flow of substantially constant current through said capacitance means during said trace periods, said vacuum-tube repeater having a grid voltage-conductance characteristic free from excessive curvature over a part of its operating range within upper and lower limiting regions, a feed-back circuit for said tube comprising a reversing tube having an input circuit-and impedance means coupling said input circuit to said output circuit and proportioned to derive therefrom a feed-back voltage of pulse wave form, and a load circuit for said reversing tube coupled to said vacuum-tube control electrode comprising a series-connected resistor and condenser proportioned to develop a control voltage wave having saw-tooth and pulse wave form. components for causing operation of said repeater tube over said part of saidrange and said lower limiting region, and means cooperating with said capacitance means for shifting the operation of said tube substantially away from said lower limiting region substantially simultaneously with the initiation of said trace periods.

5. A generator of periodic saw-tooth current waves having substantially linear trace and relatively short retrace periods comprising, an output circuit including an impedance element, a current supply circuit and a repeater vacuum tube for effecting periodic flow of current through said output circuit and developing voltage thereacross, said tube having a grid voltageconductance characteristic free from excessive curvature over a part of its operating range within relatively sharply curved upper and lower limiting regions, a feed-back circuit for said repeater tube comprising a reversing tube and a complex impedance proportioned to derive from said output voltage a feed-back voltage having saw-tooth and pulse wave-form components of relative amplitudes independent of those of said output voltage for effecting operation of said repeater tube over said part of said range and said lower limiting region during retrace periods of operation. means for determining the duration of trace periods of operation of said repeater tube and limiting said operation below said upper limiting region, and impedance means in parallel withl said impedance element for by-passing the pulse components of the current from said impedance ele-` ment thereof to shift the operation of said repeater tube substantially above said lower limiting range substantially simultaneously with the initiations of said trace periods.

6. A generator of periodic saw-tooth waves having substantially linear trace and relatively short retrace periods comprising, an output circuit including capacitance means, a voltage supply circuit and a vacuum-tube repeater for eifecting periodic charging and discharging of said capacitance means and developing a voltage across said output circuit from said supply circuit during said trace and retrace periods, said tube having a grid voltage-conductance characteristic tree from excessive curvature over a to said output circuit and part of its operating range within upper and lower limiting regions, a feed-back circuit for said repeater tube comprising a reversing tube and a complex impedance proportioned to derive from said output voltage a feed-back voltage having saw-tooth and pulse wave-form components of relative amplitudes independentcf those of said output voltage for effecting operation of said repeater tube over said part of said range and said lower limiting region during retrace periods of operation, means for determining the duration of trace periods of operation of said repeater tube and limiting said operation below said upper limiting region, and resistance means in parallel with said first-mentioned capacitance means for by-passing said saw-tooth wave-form current components from said capacitance means to shift the operation of said repeater tube substantially away from said lower limiting region substantially simultaneously with the initiation of said trace periods, whereby the operation of said tube is held above and below said lower and upper limiting regions, respectively, during said trace periods. Y

7. A generator of periodic saw-tooth waves having substantially linear trace and relatively short retrace periods comprising, an output circuit including capacitance means, means including a voltage supply circuit and a vacuum-tube repeater having a control electrode for effecting periodic charging of said capacitance means from said supply circuit by substantially constant current in one direction during said trace periods and discharging of said capacitance means by current flow in the opposite direction during said retrace periods, said vacuum tube having a grid voltage-conductance characteristic free from excessive curvature over a part of its operating lrange within upper and lower limiting regions, a feed-back circuit for-said repeater tube comprising a reversing tube having an input circuit and impedance means coupling said input circuit proportioned to derive therefrom a feed-back voltage of pulse wave form and a load circuit for said reversing tube coupled to said repeater tube control electrode and comprising a series resistor and condenser for developing a control voltage wave having saw-tooth wave-form components and pulse Wave-form components determining the duration of retrace periods of operation and to effect operation of said repeater tube within one of said limiting regions during said retrace periods, means for applying synchronizing pulses to said input circuit for determining the duration of trace periods of operation of said repeater tube within said part of said range, and resistance means in parallel with said first-mentioned capacitance means for by-passing said saw-tooth wave-form current components from said capacitance means to shift the operation of said repeater tube substantially away from said last-mentioned limiting region substantially simultaneously with the initiation of said trace periods, whereby the operation of said tube is held above and below said lower and upper limiting regions, respectively, during said trace periods.

8. A generator of periodic saw-tooth Waves having substantially linear trace and relatively short retrace periods comprising, an output circuit including energy-storage means, an energy supply circuit, and a repeater device for effecting periodic charging and discharging of said storage means from said supply circuit, said device having a repeating characteristic free from excessive curvature over a part of its operating range between relatively sharply curved limiting regions thereof, a feed-back circuit for said device responsive to operating conditions in said output circuit for controlling said device to cause operation thereof over said part of said range and at least one of said limiting regions, impedance means effectively coupled to said storage means and so proportioned with respect to the impedance thereof as to shift the operation of said device substantially away from vsaid limiting region during trace periods, means for adjusting the amplitude of the wave developed by said generator, said amplitude adjustment being inde-` pendent of the linearity of said developed wave,

and means for adjusting the linearity of the wave 1 developed by said generator, said linearity adjustment being independent of the amplitude of said developed wave. f

9. A generator of periodic saw-tooth waves having substantially linear trace and relatively short retrace periods comprising, an output circuit including energy-storage means, an energy supply circuit, and a repeater device for effecting periodic charging and discharging of said storage means from said supply circuit, said device havy ing a repeating characteristic free from excessive curvature over a part of its operating range between relatively sharply curved limiting regions thereof, a feed-back circuit for said device responsive to operating conditions in said output circuit for controlling said device to cause operation thereof over said part of said range and at least one of said limiting regions, impedance means effectively coupled to said storage means and so proportioned with respect to the impedance thereof as to shift the operation of said device substantially away from said limiting region during trace periods, means for adjusting the amplitude of the wave developed by said genand means for adjusting the free oscillating frequencyA of said generator, said frequency adjustment being independent of the amplitude of said developed wave.

10. A generator of periodic saw-tooth waves having substantially linear trace and relatively short retrace periods comprising, an output circuit including energy-storage means, an energy supply circuit, and a repeater device for effecting periodic charging and discharging of said storage means from saidsupply circuit, said device having a repeating characteristic free from excessive .curvature over a part of its operating range between relatively sharply curved limiting regions thereof, a feed-back circuit for said device responsive to operating .conditions in said output circuit for controlling said device t0 cause operation thereof over said part of said range and at least one of said limiting regions, impedance means effectively coupled to said storage means and so proportioned with respect to the impedance thereof as to shift the operation of said device substantially away from said limiting region during trace periods, means for adjusting the linearity of the wave developed by said generator, said linearity adjustment being independent of the frequency of the developed wave, and means for adjusting the free oscillating frequency of said generator, said frequency adjustment being independent of the linearity of said developed wave.

HAROLD A. WHEELER.

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