US2221665A

US2221665A - Periodic wave generator

Info

Publication number: US2221665A
Application number: US226874A
Authority: US
Inventors: John C Wilson
Original assignee: Hazeltine Corp
Current assignee: BAE Systems Aerospace Inc
Priority date: 1938-08-26
Filing date: 1938-08-26
Publication date: 1940-11-12
Anticipated expiration: 1957-11-12

Description

Nov. 12, 1946. J. c. WILSON PERIODIC WAVE GEi fiRA ToR Filed Aug. 26, 1938 FIG.2.

FIG. I.

FIG.4.

FIGS- INVENTOR JHN C.WILSON BY 0 l k l 1 I ATTORNEY Patented Nov. 12, 1940 John C. Wilson, Bayside, N. Y, assignor to Hazeltine Corporation, a corporation of Delaware Application August 26, 1938, Serial No. 226,874

' 8 Claims.

ators and, while the invention is of general ap plication, the generator of the invention is particularly suitable for deriving from a given wave a wave of submultiple frequency for use as a timing wave in a television signal transmitter.

In generating timing pulses in a modulatedcarrier television signal transmitter, some of which form components of the transmitted s ig nals, it is customary to generate high-frequency waves which are stabilized with respect to the source of alternating current at the transmitter and to derive therefrom waves of submultiple frequencies. -The submultiple-frequency waves so developed are used for the various timing oper-,

ations necessary to generate and transmit .the

For example, in decomposite television signal. veloping and transmitting a television signal involving double interlaced scanning and 441 lines per second, it is customary to develop a high-frequency. wave, for example, 26,460 cycles, which is stabilized with respect to a source of 60 cycle power supplying the transmitter. From this high-frequency wave there is derived-a submultiple-frequency wave of 13,230 cycles, that is, half the frequency of the high-frequency wave, which is utilized to produce line-frequency synchronizing pulses for the transmitted signal. By a further series of subdivisions, a 60 cycle wave is developed and utilized to provide field-frequency pulses for the transmitted signal. A high degree of accuracy is essential in the relation between the frecuenciesof the difierent wave generators which go to make up the timer chain of the sys- 35 tem. For this reason it is customaryto develop the waves in the manner described above rather than to generate waves of increasingly higher frequencies from the low-frequency source sup- Ply the transmitter. However, in subdividing a generated high-fre quency wave to derive the waves oiflower' 1re-,

quency, it is difficult to secure generators or frequency dividers for each oi the steps which are not subject to some inaccuracies. If a particular wave generator of lower frequency is to produce pulses of a frequency of 1/11. times that of a higher frequency control wave, it is customary to provide a control circuit for the generator which is responsive to pulses in the control wave which are separated by n-l pulses. The usual way of accomplishing this is to provide a relaxatibn oscillator including a vacuum tube having a control electrode to which the desired pulses at are supplied. One particular circuit which has wave.

This invention relates to periodic wave gener- 7 been utilized comprises a condenser which is alternately charged from a direct current source and discharged, one of the operations being controlled by a' vacuum tube. In this type of circuit the activeperiod of the tube depends not only on 5 the control wave, usually applied to the control grid, but also upon the voltage of the condenser which is effectively coupled into the anode circuit of the tube'and thereby affects its anode voltage. In previous circuits of this type, the 1g condenser is charged relatively slowly, either linearly or exponentially, and discharged rapidly, or vice versa. As a result, the anode voltage rises to a substantial value during the initial portion of the linear or exponential charge or discharge is and the slope of the anode voltage wave durin 7 the.final portion of this period is of relatively low value so that the control tube'm'ay be controlled by a wrong pulse in the controlling wave, or by some extraneous influence, such as static. an

', That is, the system is much too sensitive to controlling effects on its control electrode over substantially all of the linear or exponential charging or discharging periods.

It is an object of the invention to provide a 28 periodic wave generator which is not subject to the above-mentioned disadvantages.

It is a further object of the invention to provide a periodic wave generator which is've-ry insensitive to a control wave, except during portions of each cycle when the control wave shouldbe effective. 7

It is a further object of the invention to provide a periodic wave generator which is very insensitive with respect to any external influence, .35 except during a small portion of each cycle within which it is desired externally to influence the generator. V p

In accordance with the invention, a periodic wave generator adapted to be excited or fired by 40 selected pulses of a periodic-pulse wave which may include disturbing spurious pulses, comprises a capacitance means havingcharging and discharging circuits, the voltage across the .capacitance meanscomprising-the desired voltage 45 Means are provided dependent at least in part upon the voltage of the capacitance means for controlling the charging and discharging circuits periodically and alternately to charge and' discharge the capacitance means. The generator I0 also includes means for decreasing materially the susceptibility to firing by undesired pulses occurring between the selected pulses comprising impedance means included in one of the charging or discharging circuits, the impedance of the imparticularity in the appended claims.

pedance means being so proportioned with respect to the impedance constants of said one circuit that the slope of the voltage-time characteristic of the capacitance means during the greater portion of the final half of the active period .of said one circuit is substantially greater than that of a linear voltage-time characteristic between the same charging voltage limits of the capacitance means. i

In a preferred embodiment of the invention, a direct current circuit is provided for charging a condenser having the above-mentioned imped time means in circuit therewith and the control tube is utilized to discharge the condenser. The control tube is provided with. a control electrode to which may be appliedcontrol pulses. In this preferred embodiment, therefore, the impedance -means prevents the voltage across the condenser fromrising to the critical value, that is, above the value it must have before the tube can be controlled by the pulses on the control grid, until such time as it is desired to control the tube. The circuit is thus very insensitive over nearly all of its charging cycle.

The novel features which are believed to be characteristic of this invention are set forth with vention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof, will best be understood by reference tothe following description taken inconnection with the accompanying drawing, and its scope will be pointed out in the appended claims.

Fig. 1 is a simplified circuit diagram of a periodicwave generator embodying the invention; Fig. 2 illustrates the voltage time characteristics of a circuit similar to that of Fig. 1, if the charging circuit of the. invention is not utilized; Fig. 3 illustrates the characteristics of the circuit of Fig. 1 having constants proportioned in accordance with the invention; Fig. 4 is a circuit diagram of a further embodiment of the invention; Fig. 5 illustrates certain operating characteristics of the circuit of Fig. 4; and Fig. 6 is a circuit diagram of a periodic-wave generator similar to that of Fig. 1 but comprising a high vacuum tube provided with regenerating means.

Referring now more particularly to the drawing, in Fig. 1 there is shown a periodic wave generator comprising a capacitance means l0 which is charged from a battery ll through a circuit comprising a resistor l2 and an inductance l3. Thedischarging circuit comprises a vacuum tube H, preferably of the vapor electric discharge type, having output electrodes connected across condenser and having its control grid normally biased to cutofi by means of a source of voltage,

' indicated as -C, applied through a resistor l5.

Neglecting for the present the featuresof the circuit of Fig. 1 constituting the present invention, the wave generator described is similar to those whichhave previously been used and its operation is well understood in the art. Briefly, however, condenser l0 is'.charged exponentially from battery H during the period t1, tz (see Fig. 2) and is-discharged by vacuum tube I4 during the time ta, ta, this cycle being indefinitely repeated. The periodic voltage across the condenser 10 may be utilized directly as, or may be utilized to derive, a secondary wave of a desired frequency. The wave A of Fig. 2 indicates a source of high-frequency pulses which may be applied to the control electrode of electron dis- The incharge device It, each of the pulses .being suflicient to bias the tube above its cutoff value dur-' the discharge circuit of the capacitance means I0 is jointly controlled in accordance with the voltage of the capacitance means and predetermined pulses of the wave A applied to its control electrode, and the tube, therefore, comprises means dependent at least in .part upon the voltage of the capacitance means for controlling the charging and discharging circuits periodically and alternately to charge and discharge the capacitance means. Curve B of Fig. 2 indicates the voltagetime characteristic during the charging period of condenser l0 and it is seen that, at the time t4, the condenser voltage and, therefore, the anode voltage of tube l l rises above the critical value Vc and the tube may, therefore, be made conductive by pulse C, whereas it is desired that the generator should be insensitive to pulse C and should be controlled by pulse D. Furthermore, due to the relatively large voltage applied to the anode of tube l4 during times in the vicinity of pulseC, extraneous influences, such as static pulses, may easily cause tube It to become conductive even though pulse C itself did not have this effect.

In accordance with the present invention, inductance element I3 is inserted in ,the charging that of the resistor [2 are so proportioned relative to the impedance constants of the charging circuit comprised in large part by condenser l0 as to modify the time-voltage characteristic from that of curve B of Fig. 2 to that of curve B, shown in Fig. 3. The high-frequency wave A of Fig. 3 is identical with that of Fig. 2. It is seen that the amplitude of the voltage time characteristic B of condenser ill at any predetermined time during its active or charging period is substantially less than that of characteristic B at a corresponding instant of time over substantially all of the active period. Consequently, the amplitude of the voltage appearing across the capacitance means I0 at any predetermined time during the greater portion of the final half of the active period of the charging circuit is substantially less than that resulting from a linear voltage-time characteristic between the same charging voltage limits of the capacitance means. Therefore, during such period, the voltage of the condenser 10 does not rise dangerously close to the critical voltage V0 and the generator is not likely to be affected by'extraneous pulses-or tram-- greater than that of a linear voltage-time characteristic a, ,b between the same charging voltage limits V2V1 of condenser 10. It is thus evident that the amplitude of the voltage appearing across the condenser ID at any predetermined time during the greater portion of the final half of the charging period .t1t2 is substantially less than that of a linear voltage-time characteristic between the same charging voltage limits V1v2 1'8 of the condenser. Therefore, the tube It is not responsive to the premature pulse C but only to the desired pulse D and is less likely to be trippedv by extraneous transients occurring in time in the vicinity of pulse C. Thus, the system includes Tube 14 Type 884 Capacitance 10 micro farad.. 0.05. Battery 1 1; volts 170 Resistance 12 'ohms 5,000 Inductance 13 henrie s 20 Normal operating freguency cycles '60 The circuit of Fig.4 difiers from that of Fig. 1 primarily in. the fact that a vacuum tube 20 has been provided for effectively opening or interrupting the charging circuit of condenser I during the interval when condenser I0 is beingdischarged through tube 14. Similar circuit elements have been given similar reference numer- I erably-are as follows:,

als in the two figures.

charging circuit comprising series-connected in ductance l3 and resistor 12, while a resistor 2| is included in the discharge circuit of condenser l0 and in the input circuit of tube 20.

In considering the operation of the circuit of Fig. 4, it will be seen that, when tube I4 becomes conductive to discharge condenser 10, an appre-- ciable voltage is developed across resistor 2| by the discharge current which voltage is applied to the control electrode of vacuum tube 20, thereby to bias the same-beyond its cutoff value and effeotively open the charging circuit of the system.

The characteristics of the wave generator of Fig. 4 .are illustrated in Fig. 5 from which. itis seen that, byopening the charging circuit of the condenser III while the condenser is being discharged, the amplitude of the condenser voltage is further decreased during the initial portion of .the charging period and the slope of the charging voltage time curve of condenser I0 is further increased during the final portion of the charging period. This is shown by curve B of Fig. 5. From this curve, it is seen that the amplitude of the voltage across the condenser III at any predetermined time during the final half ts-tr of the charging period t1-tz is even less than that resulting from the voltage-time characteristic of the Fig. 1 arrangement, as indicated by the curve of Fig. 3,

and. especially is this so during the relatively shortinterval ts-tz which immediately precedes the desired synchronizing pulse D. Therefore, the

circuit of Fig. 4 is much less sensitive overthe initial portion of .the charging periodthan the circuit of Fig. 1 and is at least equally sensitive to the desired synchronizing pulses near the end of the charging period. Thus, resistor 2| comprises impedance means -in,circuit with vacuum tube 20 for controlling the periods of conductivity of this tube.

One set of values for the circuit of .Fig. 4 pref- Tube 14 Tube 20 Type 605 Resistance21 Between 100 and 500 ohms- The output electrodes of vacuum tube 20 are connected directly in the ype,884 f The other values remain the same as those giv en above for Fig. 1. I

While there-has been described a periodic wave generator comprising a vapor electric discharge tube for discharging the condenser, it will be understood that the principles of the-invention are equally applicable to'an arrangement, as shown by Fig. 6, utilizing a high vacuum tube '18 ineluding suitable regenerating-means, comprising inductively coupled windings 11, I8, to change the conductivity of the tube from minimum to maxias that of Fig. 1 of Patent 2,148,096, issued February 12, 1939, to G. B. Banks. Further, the vacuum tube may be included in the charging circuit of thecondenser rather than the discharging circuit,- as shown by Patent 2,118,352, dated May 24, 1938, in which case the discharge circuit-isproportioned in accordancewith the above prin-' ciples.

mum for a small difference in grid voltage such 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-andscopeof the invention. a What is claimed is: V 1. A periodic wave generator adapted to be fired by selected pulses of a periodic-pulse wave which may include disturbingspurious pulses,

comprising capacitance means, charging and discharging circuits for said capacitance means, means dependent at least inpart upon the voltage of said capacitance means for controlling said circuits periodically and alternately to charge and discharge said capacitance means, and means for decreasing materially the susceptibility to firing by undesired pulses occurring, between said selected pulses comprising impedance means 1m;

cludedin one of said circuits, the impedance of said'impedance means being so proportioned with respect to the impedanceconstants of said one of said circuits that the slope of the voltage-time characteristic of said capacitance meansduring .the greater portion of the final half of the active period of said one of said circuits is substantially greater than thatof a linear voltage-time characteristic between the same charging voltage limits of said capacitance means.

2. A periodic wave generator adapted to be fired I 4 by selected pulses of a periodic-pulse wave which may include; disturbing spurious pulses, comprising capacitance means, charging and dis-- charging circuits for said capacitance means, means dependent at least in part upon the voltage of said capacitance means for controlling said circuits periodically and alternately to charge and discharge said capacitance means, and means for decreasing materially the susceptibility to firing.

by undesired pulsesoccurring'between said se-v lected pulses comprising impedance means included in one of 'said circuits, said impedance means-being so proportioned with respect to the reactive constants of said one of 'said circuits that the amplitude of the voltage. appearing across said capacitance means at.any predetermined time during the greaterportion of the final half of the active period of said one of said circuits is s'ubstantially less than that resulting from a linear voltage-time characteristic between the same.

charging voltage limits of said capacitance means.

.. 3. A periodic wave generator adapted to be fired lected pulses comprising means including a seriesconnected inductance and resistor in one of said circuits, the values of said inductance and said resistor being so proportioned with respect to the value of said capacitance means that the amplitude of the voltage appearing across said capacitancemeans at any predetermined time during the greater portion of the final half of the active period of said one of said circuits is substantially less than that resulting from a linear voltage-time characteristic between the same. charging voltage limits of said capacitance means.

4. A periodic wave generator adapted to be fired by selected pulses of a periodic-pulse wave which may include disturbing spurious pulses, comprising capacitance means, charging and discharging circuits for said capacitance means, means comprising a vacuum tube included in one of said circuits controlled at least inpart in accordance with the voltage of said capacitance means for controlling said circuits periodically and alternately to charge and discharge said capacitance means, and means for decreasing materially the susceptibility to firing by undesired pulses occurring between said selected pulses comprising impedance means included in the other of said circuits, said impedancemeans being so pro-,

portioned with respect to said capacitance means that the amplitude of the voltage appearing across said capacitance means at any predetermined time during the greater portion of the final half of the active period of said one of said 'circuits is substantially less than that resulting from a linear voltage-time characteristic between the same charging voltage limits of said capacitance means.

' 5. A periodic. wave generator adapted to be fired by selected pulses of a periodic-pulse wave which may include disturbing spurious pulses, comprising capacitance means, charging and discharging circuits for said capacitance means,

, means dependent atleast in part upon the voltage of said capacitance means for controlling said circuits periodically and alternately to charge and discharge saidcapacitance means, and means for decreasing materially the susceptibility to firing by undesired pulses occurring between said se lected pulses comprising impedance means included in one ofsaid circuits, said impedance means being so proportioned with respect to said capacitance means that the amplitude of th voltage appearing, across said capacitance means at any predetermined time during the greater portion oi: the-final half of the active period of said one of said circuits is substantially less than that resulting from a linear voltage-time characteristie between the same charging voltage limits of fired by selected pulses of a periodic-pulse wave which may include disturbing spurious pulses,

comprising capacitance means, a charging circuit for said capacitance means, means comprising a vacuum tube controlled in accordance with the voltage across said capacitance means for discharging said capacitance means at periodic intervals, andmeans for decreasing materially the susceptibility to firing by undesired pulses occurring between said selected pulses comprising impedance means included in said charging circuit, said impedance means being so proportioned with respect to the impedance constants of said charging circuit that the amplitude of the voltage appearing across said capacitance means at any predetermined time during the greater portion of the final half of the charging period of said capacitance means is substantially less than that resulting from a linear voltage-time characteristic between the same charging voltage limits of said capacitance means, and means including a vacuum tube included in said charging circuit for effectively interrupting said charging circuit during the discharge period of said capacitance means to decrease further the amplitude of the voltage appearing across said ca-.

pacitance means during the said greater portion of the final half of said active period.

'7. A periodic wave generator adapted to be fired by selected pulses of a periodic-pulse wave which may include disturbing spurious pulses, comprising capacitance means, a charging circuit for said capacitance means, means comprising a vacuum tube controlled in accordance with the voltage across said capacitance means for discharging said capacitance means at periodic intervals, and means for decreasing materially the susceptibility to firing by undesired pulses occurring between said selected pulses comprising impedance means included in said charging circuit, said impedance means being so proportioned with respect to the impedance constants of said charging circuits that the amplitude of thevoltage appearing acrosssaid capacitance means at any predetermined time during the greater portion of the final half of the charging period of said capacitance means is substantially less than that resulting from a linear voltagetime characteristic between the same charging voltage limits of said capacitance means, a vactioned vacuum tube for controlling periods of conductivity of said last-mentioned vacuum tube.

8. A, periodic wave generator adapted to be synchronized by selected pulses of a periodicpulse wave which may include disturbing spurious pulses, comprising capacitance means, charging ,and discharging circuits for said capacitance means, means comprising a vacuum tube having .a control electrode for controlling said circuits periodically and alternately to charge and discharge'said capacitance means, said last-mentioned means being controlled jointly in accordance with the voltage of said capacitance means and predetermined pulses of said-wave applied to said control electrode, and means for decreasing materially the susceptibility to synchronization by undesired pulses occurring between said seany predetermined time during the greater- 1'50;-

tion of the final half of the active period of said one of said circuits is substantially less than that resulting from a linear voltage-time characteristic between the same chai'ging voltage limits of said capacitance means.

. JOHN C. WILSON.