US2490500A - Stabilized oscillator generator - Google Patents

Description

Dec. 6, 1949 '.'J. YUUNG STABILIZED OSCILLATOR GENERATOR 3 Sheets-Sheet 1 Filed. Dec. 28, 194

TRANSMITTE FREQUENCY MULT/PL/ER 4w paws/2. AMPLIFIER TUNER MASTER OSCILLATOR STANDARD FREQUENCY v s Mu ans 0 mx p C V L A WW 0 mm 00 N V ERU Ml FRC r mm 5\ 0 u v A e i ll l WAVEFORMS CASE I MASTER OSCILLATOR FREQUENCY 700 HIGH CASE 2 MASTER OSCILLATOR FREQUENCY 7270 LOW w Y R M 0 5 Es H V M%A A u Dec. 6, 1949 -c. J. Y OUNG STABILIZED OSCILLATOR GENERATOR I 3 Sheets-Sheet 2 Filed Dec. 28, 1946 1 I I l I I I I I DEC/405 lllllllllllllllllll Mum- 2 I 42 t l l G .N w Y Wu IIIIIIIIIIIIII II R w m N us .n mm A A) H m our/ w Patented Dec. 6, 1949 UNITED Si OF I CE Gharles J Young, Princeton; N; Jr, assignor to Radio Corporatien'of AmericaeaucorporationzofJ Delaware:

Application Decemben28, 1946, Serial .No. 719,035-

14 Claims): (Cl;.-2'5I);-36) I This applicationirelates' to oscillation generatorsand'in particular, a generator the! frequency of operation of which is stabilized. but can be" changed to any frequency within a given wide; range;

There'isgreat need of a' calibrated'variablefre quency'master oscillator which can readily be set: to:any' predetermined frequency within its range, with assurance thatithe output frequency willremain close to the desiredpreset'frequency;

The general object of this invention is to provide oscillation generating means as outlihedi above for supplying to" a transmitter or other utilization means, oscillations of any frequency within a given wide range.

A further object of the present invention is to provide oscillation generating means asidescribed. above and'simple means for setting.v or selecting' the chosen frequency.

A further object ofthepresent inventionisito. 2'0

provide oscillation generating and selecting means wherein the oscillations generated and; of selected'frequency are fi'xeol'infrequenoy with respect'to an oscillator of standard fixed 'frequency such as a crystal oscillator.

An additional object of the present invention is tov provide an. oscillation generator as described. above with simple andfeffective means; for automatically correcting the frequency ofoperatiom of said oscillation generator should the same be improperly related in frequency to. the frequency oflthe standard source thereby stabilizing. theirsquency of'operation of the generator- The above objects are. attained as follows;

Oscillations from the standard. frequencyisource are counted (divided infrequency) and .used to. establish time intervals of fixed. andknownduration andalso to produce voltage of av duration. measured by said time intervals. At tl'ie start of certain of the time intervals, a preset cycle counter is set into operation to count off a preset number of cycles of the oscillations generatedland'f. to stop. A voltage of duration measuredfby the. counting time of the cycle counter. is developed and'the diiierential of said produced voltage and developed voltage isused to; control the: master oscillator frequency; Now'if the frequency of'the controlled. oscillator is changed anda new andf appropriate number set up on the. counter, my

system takes over to stabilize this new frequency of operation. Thus a series of frequenciesrelated as desired may be generated. Suchoperation cannot be carriecl' out in priorart system usingfixed frequency dividers.

In describing my invention in detail; reference will be 'rrrade to fthe attached drawings wherein:

Fig; 1f illustratesby block diagraman 05011135 tion generator in accordance with my invention for stableoperati'on" at any selected frequency of- 5 a-widerange'of frequencies.

Fig: 2 illustrates by voltage'curves' the opera-- tionof my syste'rnwfFi'g: 1; andofFig. 4;

Fig: 3illustrates detailsof one-type of cycle counter circuit which is-satisfactory for -use'in thef alsu-contro-l'ledby'the counter toact through'tiie" reaotairce "tubeof unit-5 tostabilize the'generator"- at f any frequency 'se'le'ct'e'd for'genera'tion" by setting. the number of cycles counted and roughly adjusting the tuning" condenserof the? master" oscillator:

Referring to'Fig: 1; the? master oscillator 2; wnich'supplies theoutbutfor' use in; for example; a transmitter-T, isshown as controlledfrom' a" frequency standard I The frequency standard l "mayinclude'acrystalbscillator; The'basiccon troris obtainediby comparing twotim'e'intervals; one measured" by the" standard oscillator I" ire-'- quency; the other a measure of a preset number of? cycles ofitheoscillations generated unit- 22 By way'of example; it may be: assumed that the' frequency standard I operates at'a. frequency of 1000' cycljesip'er secondend' the master oscillator 2 which may beset'andjortuned at. any, one of? any'd'esired numbenofrfr'equencies; wiILiforpur;

poses of "illustration; be operated at 7580" cycles: persecond. To obtain the two'sliort time intervais'whichare comparedto obtain control energy foncontrollingthefrequency of operation of oscillator; 2, separateffreque'ncy' dividers or. time:

4 sensitive'ele'ments'BTandAare'usedJ Element 3"- isbasi'ca'll'y a fixed frequency divider which divides thefrequency'offthestandard" I i. in1the*case"il lus-' trated byIOG. Thismeans that" the output of" divider"3"will haveafrequencyiof ten cycles per second; In the embodiment, described." the unit 3is"ass mned'to include a divider 'ofth'e counting} circuittype and supplyingten pulsesper. second. as illustratedi'by line a of Fig. 2.

The secondfrequen'cy!divider or timer. which. is" in.unit ris in the embodimentdescribediessentiall'y an electronic; counter witli'an adf'u'stabl. stop setwhich stops thebount'thereofas set. A counter'ofthis tyne is-shown. in Gi'osdofl 'Uj application Ser. #5801461 filed. March 1; 1945: It the purpose ofth'is' counter in unit fto count off a predetermined number of cycles of operation of the master oscillator in unit 2 and at the end of this counting interval, to stop counting and produce an output pulse (lines D and c of Fig. 2). In my illustration of the oscillator, operating at 7580 cycles per second, assume that the counter is set at the value 758. This means that if the master oscillator unit 2 is operating exactly on a frequency of 7580 cycles per second, the interval of time which counter 4 will measure will be equal to the length of time passed during 758 cycles or second time intervals measured by divider 3. The start of operation of counter 4 coincides, with respect to time, with one of the pulses from counter 3, and counter 4 counts the preset number of cycles or pulses from the master oscillator of unit 2 and stops. 7

The differential correction control 5 compares the fixed intervals of time measured by the divider 3 with those measured by counter 4 and produces a; corrective voltage, representing the difference of the intervals, which is applied to an oscillator frequency control means in unit 6 which may be, by way of illustration, a reactance tube per se well known in the art. Line d of Fig. 2 shows a voltage pulse measured by a standard interval of time obtained in the correction control unit 5 from the timer output pulses line a and lines 6 and f show the intervals produced in the correction control 5 by the output pulses from counter 4. The initiation of the intervals shown in lines e and j is produced by alternate pulses of line a, a here comingfrom the divider 3, while termination of the intervals shown in lines e and f is produced .by the pulses of lines D and 0, here coming from the counter 4. Two cases are illustrated by the wave forms; lines D and e illustrating case 1 where the oscillator in unit 2 is operating at too high a frequency and lines and illustrating case 2 where the'oscillator in unit 2 is operating at too low a frequency. That is, in both cases, the oscillation generator in unit 2 is not operating at the frequency selected. To obtain the control voltage, the correction control circuit in unit combines the voltage represented by line (1 with the voltage represented by line e or 1. These combined voltages are shown as lines 9 or it for case 1 or for case 2 respectively. It will be noted that inline 9, case 1, positive polarity pulses are shown and in line h, case 2, negative polarity pulses are shown. These pulses are applied, after averaging their value, through the reactance tube in unit 6 to control the frequency of the oscillator in unit 2 and the pulse polarity is such as to correct the frequency of the oscillator in 2 in the proper direction to reduce the correction voltage to zero or to adjust the oscillator in unit 2 to the correct point of operation. The relationship between the frequency of the standard in unit I and the master oscillator in unit 2 can be adjusted or set at any desired value by means of dial switchesassociated with the counter 4. In the case illustrated, the cycle counter dials are assumed to be set at 758 which would cause the master oscillator in unit 2 to operate at 7580 cycles per second. Adjusting the counter circuit in unit 4 changes the frequency of the oscillator as described above and its frequency may be changed practically continuously throughout a wide range merely by setting the counter as desired and then roughly returning the oscillator in unit 2 to the frequency set. The oscillatory energy as selected in frequency is supplied to the transmitter T for use as desired.

The standard frequency oscillator in rectangle I may be conventional and many oscillators appropriate for use here are known in the prior art and the same will not be described in detail herein. The same remarks apply to the apparatus in rectangle 3 wherein this apparatus is designated a timer. In practice, it takes the form of a frequency divider or a decade counter. The frequency divider may be of the counter type or any other approved type, many of which are known in the prior art. For example, a decade counter such as used in unit 4 described hereinafter may be used in unit 3. It is essential, however, that wave shaping be carried out in the timer to provide pulse output as shown in line a, Fig. 2. Many means are known in the prior art for shaping the waves as desired. For example, when the timer in unit 3 is a multivibrator, its output is of square wave form and may be supplied to a difierentiating network to produce the peaks separated by the desired time intervals. A voltage differentiating network of this general type is shown in Fig. 1 of Max Mesner application #559,469, filed October 19, 1944. The counter circuit in unit 4 is as stated above in general like that of the above referred to Grosdoif application. and additions thereto have been made and the details of the counter circuit are illustrated in Fig. 3. The differential correction control circuit of unit 5 wherein the pulses are compared as to time intervals is illustrated in detail in Fig. 4. The reactance tube 6 and oscillator 2 may be conventional but in order to make my invention clear, have been included in Fig. 4 so that the manner in which the same and the correction control circuit etc., are connected in the system may be illustrated.

Referring to Fig. 3, three decade counter circuits are shown; more or less may be used. Decade l consists of multivibrator-like locking stages VI, V2, V3 and V4. These stages each have two positions of rest at one or the other of which they stay locked, when tripped thereto, until some applied voltage or current trips them again to lock them in the other position. In the embodiment shown, application of a negative voltage to the anodes and thence to the grids of the locking circuit tubes will reduce current in that tube drawing current and start the tripping action which switches the current through the other tube. Decades 2 and 3 are similar and to simplify the diagram have been illustrated by rectangles. Associated with each decade is a three-pole, tenposition switch. These switches are referred to as SI, S2 and S3, and the contacts thereof are coupled to the anodes of the locking circuit tubes whereat the potentials rise and fall depending on which tube of the pair is drawing current. For example, the anode of tube H of VI is connected to alternate contacts of pole PI of the three-pole switch S. The anode of tube 12 of this stage is connected to the remaining contacts of this pole. The anodes of tubes [3, l4 and I6 of V2 and V3 are connected to staggered pairs of contacts of the second pole P2, etc. The basic details of each decads and how it operates is covered fully in GrosdoiT, 580,446, referred to above and consequently, no detailed explanation will be given here. The decades count the incoming pulses from the master oscillator 2, these pulses being applied to the lead labeled Input of decade I.

The basic purpose of the counter circuit is to produce output pulses after the counter decades have counted a predetermined number of master oscillator cycles or pulses. The start of the counting is controlled by a Gate circuit so labeled in Improvements Fig. :4 as will be explained later. The -development 20f the output pulses from the decades to be produced after the predetermined count has been reached is-tobtained by combining the proper volte'gesifrom the anodes .of certain tubes in all three decades. This scheme is explained and is shown generally by Grosdoif 659,704, filed April 5, 1946. Using my illustration of a count of 758, switch S] on :decade I would be :set at position 8 which ts the units count, the switch $2 "on decade 2 *Would be set on position '5 which is the tens count an'd switch S3 on decade 3 would be set on .position '7 which is the hundreds count. The voltage pulses collected by the switchesa're combined by means of three vacuum triodes 26, 21 and 28. The tubes "are in conventional circuits including biasing lresistances 2BR connecting the switches to ground. This combination is produced by the connections of said switches to the control grids of these three tubes. The anodes of the tubes are connected together to .produce a single pulse, which represents the sum of the collected pulses, and .feeds the :same by 'way of resistors 29, Hand 31 .andscommon resistor 32 to the grid 33 of ta 'fina'l combining tube '34, The tube 34 *is connected in Jan amplifier stage with its grid grounded by a resistor 35 and its cathode tgrounded bya resistor 36 and its anode .connected -to the plus terminal of 'a :direct current source. The anode of amplifier tube 34 is cou- 'pled by a capacitor :31 to the control grid 38 of an output tube 39, the purpose of which is to deliver the combined pulse =to a'1l of the ltubesin all of the decades to trip 'the same .back to their starting position for'succ'esslve operation of the counter. This cathode ifollower stage also delivers this combined'output pulse to th'e dilierential 'correc'tionpontrolcircuit :501 Figs. .1 and 4. To do this, the cathodeiload resistor 40 of this tube is coupled through :a capacitor 43! to a lead '42 lrunning to a common reset lead in each of the three decades and also to the Ilead '44 labeled Output :whichgoes to the unit tSof-Figs. 1 and 4.

Referring to :decade I which has its switch -Sl set at position *8, :it is inoteduthat :for each po- 'sition -'of the switch, "a different combination of voltages from the eight tu'besof decade are used as explained in the Grosdofi application #580;- "446. The voltage on the :switch'S'l as applied to the :grid "of tube 26 reaches :a certain maximum .positive 'value'only when the count-is at the value for which the :switchpositioniis setand the final desired output pulse applied to the .grid of tube Ellis obtained only when the propercombination of voltages occur'ssimultaneously on the selected tubes of all three decades. For example, in decade I on the-count 'of 8, the voltages selected by'switch S! are those at the anodes *of tubes H and 14 :and 18. This combination :of "three voltages raises the "control gridof tube 26 above its cut-ofi point so that conduction is initiated in tube 25 and the potential on its anode and at resistor-29 falls. -A similar action takes place in tubes 21 and 28 when the proper voltages are obtained by the settings .on switches S2 and S3. When the final pulse which-represents the final combination of voltages from the tubes 26, 21 and 28 'is reached the voltage applied to the con- "trol grid of .tubeid is reduced Knegative) to such a point that conduction 'in the tube L3! is out oh. This action occurs suddenly at the instant the decades of the counter reach "the number or count for which'the switches have been set. Also -the tubes 26an'd 2Tmay'be made conductive severaltimesduring'the'proeess'ofthe countyettthe i6 combined voltage applied to the grid of tube 83 is never suiiiciently negative to cut tube an until the time occurs when tubes '28. 2:1 and 4B setting fun'ction is accomplished by application of the output pulse, which is positive in ipolar-ity, to the grid circuits or all the tubes in the ace-- ades Which draw current in the starting position.

As stated above, the oscillations or short pulses representative thereof are supplied :from the :oscillator to the input lead of the 'first "decade counter, Fig. 3, and at the cathode end of load resistor 40 of tube 38 is produced the potential which :resets the decade counters when they have finished. counting the preset number, and, also the potential supplied "to lead '44 which goes to the .diiferential correction control unit 5 to terminate the time interval rmeasuriing thecounting time. I'Ihe potential, also, as will appear in deta'il hereinafter, operates to close a gate for the generated oscillations and to return locking stages to one condition of stability :so that the cycle -of operation may be completed and repeated.

The arrangement :ior accomplishing these pur- :posesiand other purposes is shown in Fig. in

Fig. 4, the "dotted :rectangle 5 includes the difzfer'en'tial correction control and comprises in the embodiment shown, two multivibrator type iock- -ing stages :MVJ and MW. The dotted rectangle l .may include in addition to the counters shown in Fig. 3, a multivibrat'or type locking stage MV3 controlled .by the locking s'tageJMVJ and also :a

:gating stage GS controlled .bythe locking stage MV3. In practice, the gating stage may :als'o peak the oscillations :and may with its control stage =MV3 :be included in a separate unit here designated 4 'l h'e' -sh'owing or these connections is simplified in Fig. -1. The dotted "rectangle 6 includes the reactance tube while the "dotted freetangle 2 includes the master oscillator.

Ih'e pulses of :line c are Zminus "and are 'su'pplied by condenser 46 to the anodes and thence to the control grids of the pair of ttlbes in the locking circuit MVl which is isubstantially com ventional so that when the one tube is drawing current, the other tube is cut bit :and vice versa and the application of a "negative pulse "is ine ffective on that tube having f'a negative grid but is effective on that tube having :a positive grid to switch current therefrom "to the other tube. The :locking stage MVl has its second tube 48 anode :coupled by a condenser :50 :to the control grid of the tube .53 in the locking stage MV3. The anode of tube 48 is :also coupled by condenser 54 to the -control 'grld 0f the tube 56 of the locking stage 'MV2. Ihezi'anod'e of the tube 58 of locking stage MV2 is connected by a re- 'is controlled by the said pulse which is ampufied intube 63 and fed by coupling condenser 65' to the control grid of tube 58 of the stage MV2. .The'anode of tube 45 of the stage MVI is also connected by resistor to theanode of diode 66 and, by way of resistor 65 and connection 6!, to the capacitor 69. The arrangement here is such that both of the voltages developed on the left end tubes of stages MVI and MV2 are combined in Si and applied to the diodes connected in opposed polarity. The anode of diode 66 is connected by diiierential resistors 65 and 6! to the cathode of the diode 68 so that the potential therein which represents the difference between the potentials of lines (1 and e or d and 1 appears across the condenser 69 which is supplied to the control grid of a reactance tube stage .'II.' The reactancetube stage is connected in a well known manner with the conventional oscillator in unit 2 to control its frequency of operation in accordance with the potential developed The locking stage MVB has the anode of its tube 53 coupled to the third grid of a gating stage tube 55. Note that the control grid of the tube 52 of this locking stage MV3 is also coupled by condenser 52 to the anode of the amplifier stage tube 63, the grid of which is connected to the output lead 44 of the counter circuit output, Fig. 3.

The operation of the complete system will now be fully explained and reference will be made to Fig. 4. v

In the initiation or starting condition of the circuit, the tube 45 of locking circuit MVI and the tube 55 of locking circuit MV2 and the tube 53 of gate circuit locking stage MV3 are all in a state of conduction as indicated by the arrows adjacent their anode resistances. Their complementary tubes 48, 58 and 52 are non-conductive. The generated oscillations are continuously applied to the first grid of gate tube 55 which is biased negative by resistor 51. However, the gate tube 55 is in a state of non-conduction because of the negative direct current potential applied its number one grid and also to its number three grid by the negative anode by tube 53 of MV3. The bias is such that when the gate tube is opened very short pulses only of current flow to the anode in response to the applied oscillations. The timing pulses from timer 3 are applied to stage MVI by the input condenser 46. The first pulse or initiating pulse which starts the system through a cycle of operation causes the states of conduction of tubes 45 and 48 to be reversed or exchanged and the second pulse from the timing circuits restores MVI back to the starting position again. This operation of MVI is illustrated by line d of Fig. 2 which shows that tube 45 is cut ofi and tube 48 remains continu- .ously conductive, after being triggered for a length of time equal to the distance between the incoming pulses which is is second for the illustration selected. At, the same time that the first or initiating pulse'is applied to the locking circult MVI, the triggering of tube 48 to a conductive state sends a negative pulse by way of condenser 56 to stage MVt in the gate circuit. It is the purpose of the gate circuit combined with gate tube-55 topass peaks of the cycles of oscillation .from the master oscillator 2 into the counter circuit of unit 4 so that the counter may count off :a predetermined number of cycles as explained ipreviously. To carry out this operation, the looking' circuit MV3 controls conduction through gate tube 55.'- Normally, or m the absence of control,

gate tube 55 is biased to 'cut-ofi because as shown above tube 53 is conductive and its anode'is negative and holds the number three grid of tube 55 well below the cut-off point. If the initiating pulse from looking stage MVI acts by virtue of the drop in potential on the anode of tube 48 to trigger stage MV3, this raises the potential of the anode of tube 53 and on the number three grid of tube 55 to the point where the gate is open. The cycles of energy, that is, peaks thereof, received from the master oscillator via condenser 59 are allowed to pass (amplified) through tube 55 and go out on lead 6| to the counter only when the gate is in the open position. At all other times, when the gate is closed, no pulse from the master oscillator is passed to the tube counter.

So far in my explanation of operation, MVI has been turned on and the countin of osclllating cycles in the counter has been initiated. MV2 was also triggered, by the negative potential developed on the anode of tube 48 and applied by condenser 54 to the grid of tube 56, at the same instant when MVI was originally triggered. Hence, tube 58 is also tripped to the state of conduction and tube 56 is cut off. No further action takes place in the system, except application of the potentials developed at the anodes of tube 45 and 58 to the diodes 65 and 68, until the counter of Fig. 3 has accumulated or counted ofi the pre-determined number of cycles that number being 158 in our illustration. When the counter has reached this count, its output pulse developed as explained previously will be applied by way of input triode 63 to perform two functions. The first function is to trigger the gate circuit GS to the ofi position to stop the flow of master oscillator output cycles to the counter. This is accomplished by application of the counter output pulse reverse by tube 63 to the grid of tube 52 (conductive) of locking stage MV3 by way of condenser 52' which triggers it into its initial position with tube 53 conductive. This action then restores the cut-01f bias on gate tube 55 thus stopping the flow of oscillator cycles to the counter. At the same time that the gate circuit is turned off, the negative potential swing at the anode of tube 63, caused by the pulse from the counter, passing through condenser 65, triggers the locking stage MV2 back into its initial or starting position with tube 58 cut ofi and tube 56 conductive. The operation of MV2 is illustrated by lines e and ,f of Fig. 2 for case 1 and case 2 as mentioned earlier. Considering case 1 of line c, it is noted that MV2 is restored to its initial condition prior to the time that MVI, as shown by line d, is returned to its initial condition. In other words, theinterval of time measured by MV2, shown by line e, is shorter than the interval of time measured by MVI or shown by line 11. This difierence in these two time intervals is due to and indicates the fact that the frequency of the masteroscillator 2 is too high. This frequency being too high causes the counter in Fig. 3 to count off the predetermined number of cycles in an interval of time shorter than the standard interval of time measured by the timing pulses out of timer 3. If, now the master oscillator frequency here is too low, as indicated and illustrated by line 1 of case 2, then the interval of time determined by the locking stage MV2 as controlled by pulses from the counter would be greater than the standard interval of time of line d. Since the counter produces an output pulse, when a'pr'e. determined number of cycles has passed, difierent BAQOAQQ:

output pulses may occur earlier orlater than the: second pulse from the timer 3,, which re.-, tripsstage MVI and terminates the voltage pulse (lined), depending on whether the master oscillator frequency is higher than or lower than the correct. value. When the master oscillator in unit 2 is exactly on the proper frequency, the output pulse from the counter of unit 4 occurs simultaneously with the second output. pulse from the timer of unit 3.

Toobtain a correct voltage for the oscillator to restore it to the correct frequency, a double diode circuit is used. In this circuit it will be noted that. the two diodes 66. and 68 are connected in the direction of conduction between a point H10, held at a chosen negative voltage by divider resistances 69' and II, and ground. Initially, therefore, the capacitor 69 may be charged to any voltage between and the. potential of point I00. Any tendency for the capacitor voltage to become positive, will be prevented by conduction from 69 through resistor 65, diode 66,.and'resistor 66! to ground; while any tendency to become more negative than point I00 will be prevented by conduction through diode 68 and resistor 61'.

In operation, the voltage of the plate of tube 45 is represented by d in Fig. 2, while that of the plate of tube 58 is shown by e and f. These two voltages connected through resistors and 60 respectively combine in lead 6| so that its voltage is as shown by g and h in Fig. 2. For the case of g the positive pulse passes through capacitor IM' and momentarily raises the potential on point I00; This causes conduction through diode 68 and resistor 61 to reduce the negative potential on capacitor 69 and thereby lower the bias on reactance tube TI which lowers the frequency of master oscillator 6. On the other hand, in case 2, the negative pulses shown by h in Fig. 2 passthrough capacitor H12 and make the diode 66 momentarily conductive to pass charge from cae pacitor 69 through resistor 65, thereby making the negative bias of tube 1| greater and thus increasing the frequency of the master oscillator.

The corrective action is an accumulative one due to the storage effect of capacitor 69. The more positive pulses arrive, the more positive becomes the bias voltage on tube H and the more the frequency of the master oscillator is reduced. Asits frequency approaches the correct value the potential on capacitor 69 approaches a steady stateand the length of the corrective pulses approaches zero.

The particular feature of this invention is that the master oscillator 2 may be adjusted readily and quickly to operate at any one of' a large number of frequencies. These frequencies in the case illustrated all are integral multiples of the output frequency of the timer for if it was desired to; change'the output frequency from 7580, as. mentioned before, to a new value, this would be accomplished byroughly turning the master osc-ill'ator to the new: frequency and by setting up new positions of switch SI, S2 and S3 of the. counter. When the. new switch positions are selected, the corrective action already described takes place. and the.v masteroscillator 2, is adjusted to the new frequency automatically and held: there by the correction. action.

For example, if I let f- -the, master oscillator frequency to be controlled jt gthe' standard reference frequency, preferably from a crystal oscillator- 10; m=the division ratio applied; to in. Ike-the division. ratio preset in the counter which,

is excited by I, and T=,the duration. of the comparison time interval;

Then

In my example, this. becomes emphasizes a valuable feature of my invention, namely that the decade dials of unit 4 can readily be made direct reading in master oscillator frequency, 1. e. D stands for dial setting in the equation. k

' What is claimed is:

1. In apparatus for generating oscillations, the frequency of which may be adjusted and for stabilizing the frequency of the generated oscillations in combination, a source of oscillations of fixed frequency, a source of oscillations of controllable frequency, a voltage phase comparer' and detector, a frequency divider coupling said source of fixed frequency to said phase detector, an adjustable frequencydivider coupling said source of oscillations of controllable frequency to said phase detector and means for controllingthe frequency of operation of said controllable source in accordance with a component resulting from phase, detection of the divided frequencies in said phase detector.

2. The method of generating oscillations of substantially fixed frequency which may be changed through a wide range of frequencies which includes these steps, producing pulses separated by time intervals of fixed duration, recur- 55 ringat a fixed rate per second, generating oscillatory energy of a frequency which may be controlled through a wide range, counting a preselected number of cycles. of said generated energy, establishing time intervals. measured by the 0 time required to make, said count, developing energy representative of the. difference in dura-. tion of saidfirst and second time intervals, and controlling the frequency of said generated oscillations, in accordance with said developed energy.

3. The method of providing oscillatory energy of substantially fixed frequency which may be changed through a wide range of frequency which includes these steps, producing pulses separated by time intervals of fixed duration, recur- 70 ring: at a fixed rate, generating oscillatory energy of a frequency which may be controlled through a widerange, counting a preset number of cycles of said generated energy during a time interval of a length about equal to the length of one of 76 said first timeintervals, developing a potential the magnitude of which is representative of the difference in duration of said first mentioned time interval and said second mentioned time intervals and the direction of variation of which indicates which of said two time intervals is longest and controlling the frequency of said generated oscillations in accordance with said developed potential to reduce said developed potential to about zero magnitude.

4. The method of generating oscillations of substantially fixed frequency NX which may be changed through a wide range of frequency (where N is a pre-selected number) which includes these steps, producing pulses separated by time intervals of fixed duration, recurring at a rate of N per second, generating oscillatory energy of a frequency which may be controlled through a wide range, counting X cycles of said generated energy, establishing other time intervals each starting about at the start of a different one of said first time intervals and of a duration equal to the time required to make said count, developing energy, the magnitude of which is representative of the difference in duration of said time intervals, and the polarity of which indicates which of said two developed intervals is longest and controlling the frequency of said generated oscillations in accordance with said developed energy to reduce said developed energy to about zero magnitude.

5. The method of providing oscillatory energy of substantially fixed frequency which may be changed through a wide range of frequency which includes these steps, producing pulses separated by time intervals of fixed duration, recurring at a fixed rate, generating oscillatory energy of a frequency which may be controlled through a wide range, counting a preset number of cycles of said generated energy during a time interval which starts about at the start of one of said first time intervals, devolping a direct current potential the magnitude of which is representative of the difference in duration of said first mentioned time interval and said last mentioned time intervals and the polarity of which indicates which of said two time intervals is longest and controlling the frequency of said generated oscillations in accordance with said developed potentional to reduce said developed potential to about zero magnitude.

6. The method of producing oscillatory energy of substantially fixed frequency which may be changed. through a Wide range of frequency which includes these steps, developing voltage peaks separated by time intervals of fixed duration, and recurring at a fixed rate per second, generatmg oscillatory energy of a frequency which may be controlled through a wide range, countmg a preset number of cycles of the generated energy during a time interval starting about at the start of a time interval between two of said voltage peaks, producing a pulse of energy at the start and the end of said count, developing energy the duration of which is representative of the time duration between said voltage peaks, developing energy, the duration of which is representative of the time duration between said energy pulses, combining said developed energies to produce a resultant potential the magnitude of which indicates which of said two time intervals is longest and controlling the frequency of said generated oscillations in accordance with said developed resultant potential to reduce said develop potential to about zero magnitude.

7. The method of producing oscillatory energy;

of substantially fixed frequency which may be changed through a wide range of frequency which includes these steps, developing voltage peaks separated by time intervals of fixed duration, and' recurring at a fixed rate per second, generating oscillatory energy of a frequency which may be controlled through a wide range, generating short electrical pulses in synchronism with said oscillatory energy, counting a preset number of pulses during a time interval starting about at the start of a time interval between two of said voltage peaks, producing a pulse of energy at the start and the end of said count, developing energy the magnitude of which is representative of the time duration between said voltage peaks, developing energy the magnitude of which is representative of the time duration between said energy pulses, combining said developed energies to produce a resultant potential the polarity of which indicates which of said two time durations is longest and controlling the frequency of said generated oscillations in accordance with said developed resultant potential to reduce said developed energy to about zero magnitude.

8. The method of providing oscillatory energy of substantially fixed frequency which may be changed through a wide range of frequency which includes these steps, producing pulses separated by time intervals of fixed duration, recurring at a fixed rate, generating oscillatory energy of a frequency which may be controlled through a wide range, counting selected groups of cycles-- of said generated energy, each'group comprising a preset number ofoyclesgduring time intervals which start about at the start of an alternate one of said first time intervals, developing-a direct current potential the magnitude of which is representative of the difference in duration of said first mentioned time intervals and said last mentioned time intervals and the polarity of: which indicates which of said two developed in-- controlled through a wide range, counting spaced blocks of the generated cycles, each of which blocks comprises a pre-selected number of cycles, during time intervals starting about at the start of the time intervals between alternate ones of said voltage peaks, producing a pulse of energy at the start and the end of each count, developing energy the magnitude of which is representative of the time duration between said voltage peaks, developing energy the magnitude of which is representative of the time duration between said energy pulses at the start and end of each count, combining said developed energies to produce a. resultant potential the polarity of which indicates which of said two time durations is longest andcontrolling the frequency of said generated oscillations in accordance with said developed resultant potential to reduce said developed energy to about zero magnitude.

. 10. In apparatus for generating oscillatory en-.

ergy of changeable frequency in combination,.a

source of oscillatory-energy of controllable fre quency, means for producing pulses separated by predetermined fixed time intervals, a pre-set cycle counter coupled to said controllable oscillation generator and set in operation by said pulses for counting off a pre-set number of cycles of said oscillatory energy during time intervals which vary as the frequency of the energy varies, means for comparing the relative lengths of said time intervals and producing a potential the magnitude of which is a measure of the difference in duration of said intervals, and means for controlling the frequency of said oscillatory energy in accordance with said resultant to make said time intervals equal to thereby bring said potential about to zero.

11. In apparatus for generating oscillatory energy of changeable and known frequency in combination, a source of oscillatory energy of fixed frequency, a source of oscillatory energy of controllable frequency, means controlled by said fixed frequency source for producing pulses separated by fixed time intervals, a preset cycle counter set in operation by said pulses for marking off the intervals of time required by said oscillation generator to generate said preset number of cycles, means for producing a first voltage measured by said first time intervals, means for producing a second voltage measured by said second time interval, and means for controlling the frequency of said controllable source in accordance with the differential of said first and second voltages.

12. In apparatus for producing oscillatory energy the frequency of which may be changed through a wide range in combination, a source of oscillatory energy of fixed frequency, a source of oscillations of controllable frequency, a controllable reactance coupled to said last source, a frequency divider and wave shaper coupled to said first source to provide pulse energy of fixed frequency, a cycle counter which may be preset for the desired count and which includes means by which it is stopped at the end of said count, a coupling between said cycle counter and said controllable source, means coupling said cycle counter to said wave shaper to start operation thereof on the appearance of a pulse of said pulse energy, a first means excited by said pulse energy to develop voltage of a duration measured by the time between the energy pulses, a second means coupled to said wave shaper and to said counter for developing a voltage of a duration measured by said counting time, a combining circuit coupled to said first and second means for providing a potential the magnitude of which represents the differential of the voltages generated thereby and means for controlling the value of said reactance in accordance with said last named potential.

13. In apparatus for generating oscillatory energy of changeable and known frequency in combination, a source of oscillatory energy of fixed frequency, a source of oscillatory energy of controllable frequency, means controlled by said fixed frequency source for producing N pulses per second separated by predetermined fixed time intervals, a preset cycle counter set in operation by said pulses and excited by oscillations from said controllable source for producing an energy pulse after a time interval sufficient for said controllable oscillator to generate a preset number of cycles, means for producing a first voltage the duration of which is measured by said first time interval, means for producing a second voltage of opposed phase the duration of which is measured by said second time interval, and means for controlling the frequency of operation of said controllable oscillator in accordance with the differential of said produced voltages to thereby bring said controllable oscillator to a frequency per second equal to N times the number preset.

14. In apparatus for generating oscillatory energy of changeable frequency in combination, a source of oscillatory energy of fixed frequency, a source of oscillatory energy of controllable frequency, means controlled by said fixed frequency source for producing pulses separated by predetermined time intervals, a preset cycle counter coupled to said controllable oscillation generator and set in operation by individual ones of said pulses for producing an energy pulse after said controllable oscillator generates a preset number of cycles, means for producing a first voltage measured by said first time interval, means for producing a second voltage of opposed phase measured by said second time interval, means for combining said voltages to produce a resultant the magnitude of which is a measure of the difference in duration of said voltages and the polarity of which is determined by which voltage is of greatest duration, and means for controlling the frequency of said controllable voltage in accordance with said resultant to thereby bring said controllable oscillator to a frequency equal to the sum of number preset.

CHARLES J. YOUNG.

REFERENCES CITED UNITED STATES PATENTS Name Date Wendt July 22, 1941 Number

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