8. APPARATUS FOR CONVERTING AN ANALOGUE INPUT SIGNAL INTO A BINARY CODE OUTPUT SIGNAL COMPRISING A SOURCE OF PERIODIC CLOCK PULSES, PULSE TRAIN GENERATING MEANS CONNECTED TO SAID SOURCE FOR PRODUCING A TRAIN OF PULSES BETWEEN SAID CLOCK PULSES, AN EXPONENTIAL WAVEFORM GENERATOR CONNECTED TO SAID SOURCE FOR PRODUCING A VOLTAGE WAVEFORM WHOSE AMPLITUDE DECREASES ONE-HALF WITH EAHC SUCCESSIVE PULSE OF SAID PULSE TRAIN, AN INTEGRATOR FOR STORING THE INPUT SIGNAL VOLTAGE FOR DISCHARGE IN STEPWAVE FORM, TRIGGER MEANS COUPLED TO SAID INTEGRATOR AND TO SAID EXPONENTIAL WAVEFORM GENERATOR FOR PRODUCING OUTPUT VOLTAGES WHENEVER THE OUTPUT VOLTAGE OF SAID WAVEFORM GENERATOR IS EQUAL TO OR LESS THAN THE OUTPUT VOLTAGE OF SIAD INTEGRATOR, SAID OUTPUT VOLTAGES THEREBY OCCURRING AT TIMES CORRESPONDING TO A BINARY REPRESENTATION OF THE PORTION OF THE INPUT SIGNAL INTEGRATED, GATING MEANS FOR PRODUCING OUTPUT PULSES ONLY WHEN THE OUTPUT OF SAID TRIGGER MEANS AND OF SAID PULSE TRAIN GENERATOR ARE SUBSTANTIALLY IN COINCIDENCE TO THEREBY PRODUCE A BINARY CODED PULSE TRAIN, AND MODULATOR MEANS FOR MODULATING PULSES PASSED BY SAID GATING MEANS WITH THE OUTPUT OF SAID EXPONENTIAL WAVEFORM GENERATOR TO PROVIDE SAID INTEGRATOR WITH PULSES OF STEADILY DECAYING AMPLITUDE TO REDUCE THE STORED SIGNAL VOLTAGE ON SAID INTEGRATOR BY A PREDETERMINED AMOUNT OF THE TIMES WHEN THE GATING PULSES ARE PASSED.
Aug, 24, 1965 D. H. BQCK ANALOGUETO-BINARY GODE CONVERTER 4 Sheets-Sheet 1 Filed Feb. 16, 1960 NIN DITMAR H. BOCK A?. L.. Zavm ATTORNEYS Aug. 24, 1965 D. H. BOCK ANLOGUE-TO-BINARY CODE CONVERTER 4 Sheets-Sheet 2 Filed Feb. 16. 1960 INVENTOR -IVNv-"l o m r l. l DITMAR H. BOCK /j, L. A ORNEYS Aug. 24, 1965 D. H. BooK ANALOGUE-TO-BINARY CODE CONVERTER 4 Sheets-Sheet 3 Filed Feb. 16, 1960 S m K T C N N O R w B O m H. 46m y M m S150 m500 E m ||||l|||||..|. l l I l i I l l I l I l I l I l I I||| 1 wwe omT N\ omT l l b u h N@ l l m Wl u n mm u im u" mm of A Nm ww om +Il |L l n -i D S1 @m mm m l om| l om u om om o om NN r|||.|...|||||| l I l I I l I l I I l I l I I i I I l l l I I I I I I|| om om .mm @I Aug. 24, 1965 D. H. BOCK 3,202,981
ANALOGUE-TO-BINARY CODE CONVERTER Filed Feb. 1e, 19Go 4 sheets-sheet 4 Time COUNTING CYCLE l5 :5o F so INVENTOR 3 DITMAR H. BOCK and United States Patent O f 3,2@2381 n ANALG-UE-T-BINARY CGD?. QNVERTER Ditmar H. Boch, Buffalo, Nit/v., assigner, by mesne assignments, to the United States ot America as represented bythe Secretary ot the Navy Y Filed Feb. 1e, 195e, Ser. No. 9,142
' 8 Claims. (Si. 340-347) This invention relates to an analogueto-binary code converter for converting an analogue voltage or other varying signal to a binary .code `output which is suitable for use by most digital computers.
ln the past in order to convert from an anaiogue voltage to units which were suitable for use by digital computers, mechanical converters, which had a large number of moving parts that generated noise and transients, have been used. The most serious limitationof these prior devices was the relatively low speed at which they were able to make a complete conversion from an analogue voltage 'to a digitalcount. .Y
The vprimary object of this vinvention therefore `is to provide an analogue-to-binarycode converter which uses f no moving parts and which may operate at speeds up to and beyond 100,000 conversions per second.
p Another object of this invention is to provide rvan analogue-tobinary code converter which eliminates transient noise and switching chatter.
Othery objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:
FIG. 1 is a block diagram of the analogue-to-binary code converter; Y f v FIGS. 2A and 2B are schematic diagrams or" a preferred embodiment of the f FIG. 3 -is a group of drawingsrillustratingpthe wave forms ofthe analogue-to-bina'ry converter. f
Referring to FIGS.K1 and 3^a signal voltageinput 10, as is illustrated bycurve Aon FIG. y3, may be an analogue voltage which varies either slowly or vrapidly with respect to time. yThis varying lanalogue voltage is passed through an initial condition circuit 11` to an integrator 12, whichinteg'rator will follow theanalogue voltage inl put 10.
if a conversion of this binary count is desired', a start signal 13 energizes a start voltage'to an output having av tegrator 12. In order to achieve a binary output, differ-- ential trigger 23 operates and opens And gate 20 when`1 the amplitude of the sweep voltage, FIG. 3H, is equal to" or less than the voltage on integrator 12. Every time that the exponential sweep voltage FIG. 3H is equal to or less than the integrator 12 voltage, the
' sweep generator 22 output, FiG. 3H, and therbinary code analogue-tobinary converter;
output 21, FiG. 3G, are fed to a modulator 24 where they are mixed lto produce the series of impulses as shown in FIG. 3l which have an amplitude which is in ay decreasing binary series and which is the same as the amplitude of the sweep voltage FIG. 3H. This series of impulses, FIG. 3i, is fed from modulator 24 to the integrator 12 where it reduces the voltage on the integrator 12 by an amount equal to the sweep voltage to successively reduce the voltage on the integrator 12 to zero; as indicated by the waveform shown in PiG. 3F. The coupling of the modulator to receive the'discrete output code pulses of the And-gate 20 eliminates the need oi a limiter and amplitier in the production of pulses tobe Yfed to the l integrator 12, y
This reduction of the voltage on the integrator 12 occurs during a counting cycle so that the integrator is then `discharged and is ready to be charged again up tothe signal voltage input to `await another count. For example curve G showsa count of 1-Ol0l which is suitable foruse in most digital computers without further modification or conversion. To prevent integrator 12 from 'recharging during counting 'cycle 1S, the initial condition circuit disconnects signal voltage input 10 from integrator 12. This counting operation may be initiated at any time by a startsignal or may be a repetitive operation.
Referring now to FIGS. 2A and 2B, which show a preferred embodiment ofthe invention, a signalvoltage may be fed to -an input terminal tdand varied by a potentiometer i0 since the maximum voltage input 1d/to the integrator 12V mustbenless than twice the maximum sweep generator 1d to initiate a. count cycle which is indicated by a short pulse 15 on FG. 3A. Counting cycle 15 may be very .short and,in order to eliminate quantizing noise,
' is appreciably shorter than the inverse of the highest frequency component that the signal voltage input 10 will have in any particular application. Since countingv cycle 15 is short relative to the variation of the signal input, arrows 16 on FIG. 3A indicate thatrthe time scale of the various wave forms in the converter (FEGS. '3B-I) have been expanded in order to more clearly show the convverter mode of operation.
' A differentiated start signal as shown in FIG. 3B triggers start-generator 14 to deliver a one mic-rosecond rectangular output pulse as shown by FIG. 3C to trigger monostable flip-flop 17. lli/ionostable lip-iiop 17 has a long output pulse, FiGBD, which is slightly shorter than the counting cycle time 15 and which energizes pulse train generator 1S. Pulse train generator 18 generates ing oscillator tube 47 to produce several outputs. Monov stable flip-flop 17 is triggeredfromthe plate of blocking oscillator d'7 to generate a long output pulse, shown in FIG. 3D, which turns on a pulsed Hartley oscillator tube 48. Amplifiers 49 in pulse generator 13 diierentiateand amplify tube 48 output so that the positive pulses in FIG.
3E are connected to And gate 2t? by line 50.
The positive pulse, FIG. 3C, on the grid of blocking oscillator tube i7 is connected by a line 51 to an ampli- A5,3 to a nominal -50 volts.
er tube 52 in the exponential sweep generator 22 where it is inverted to charge a sweep capacitor 53 to the sweep voltage, FIG. 3H, through a diode 54 to a nominal minus 40 volts. A diode clamp 55 limits the range of capacitor I vSweep capacitor 53 discharges through resistor 59 to provide a sweep voltage with a halt amplitude decay time equal to the oscillation period of Hartley oscillator tube 43 in pulse train generator 18. Cathode follower tube 56 connects the sweep voltage, FG. 3H, by line 57 to ditferential trigger Z3 and to modulator 24 by line 60.
When the amplitude of the sweep voltage FIG. 3H is equal to or less than the voltage on integrator capacitor 4, pulses FiG. 3G are passed through And gate 20 to a binary code output 21 and to modulator 24 by a line 58 so that the decreasing binary series of impulses FIG. 3J
sweep `capacitor 53, the Schmitt trigger circuit in diier-V k ential trigger 23 is operated and sends Va gating pulse by line 66 to'open the And gate 20 and produce the binary code output 2l as shown by FIG. 3G. During counting cyclelS, winding '70 on the blocking :oscillatortransformer in start generator 14 charges ca- ;-p'acitor 72fin diode bridge 43 to reverse bias each diode "in the bridge and prevent conduction from the signal voltage input to integrator capacitor 44. v Capacitor 72 discharges through resistor 73 duringV counting cycle 15 so thatintegrator capacitor 44 may be recharged to the signal voltage to await another counting cycle.
'Asis apparent to one skilled in the art, the Schmitt trigger circuit in differential trigger 23 may be some limitation at ,'high speeds, but this may easily be improved by using-high current pentodes and additional positive feedback as is well known in the art.
The circuit as thus described may need a counting cycle .15fof only ten -to twenty microseconds to allow a conversion rate of 50,000 to 100,000 per second. VHigh current, Vhigh speed circuits with solid state ydiodes or transistors can easilyfirnprove this iigure if desired.
' Obviously many 'modifications and variations of the "present kinvention are possible in the light of the above teachings.
It is therefore tobe understood that within the scope of the appended claims the'invention-rnay be practicedotherwis'e than as specifically described. What` is claimed is:V 7 *Y l. An analogue to binary code converter having a sig- 'nal ,vol-tage input and abinary code output ycdinprising 'an integrator for storing said-signal voltage, a start genera'torffor.` initiating a counting cyclehaving a relatively short-'time as compared-withfthe inverse of the highest frequency component of said signal voltage whereby quantizing -noise may be minimized, apulse trainl generator connected to said start generator for generating a series of pulsesY during said cycle, an exponentiallsweep generator connected to saidfstart Vgenerator for gener-ating an exponential sweep'voltage, .a-diiferential trigger connected to-said integrator and sweep generator for generating an output when the amplitude of said sweepy voltage is equal to or less than said stored signalvoltage, an And gate connectedv'to said pulse train generatorand differential trigger for passing a binaryf'code output having a digital count proportional to the amplitude of said signal voltage input, and a modulator connectedgto said binary code output and exponential sweep generator for reducing the signal voltage on said integrator fbyV a predeterminedy amount whenever said gate passes an output pulse.
2. An analogue to binary code converter according to claim 1 andfurther characterized by an initial condition circuit connected between said signal voltage input and said integrator for passing said signal voltage to said integratorV except during a counting cycle.
3. lAn analogue to binary code converter according to 'clairnZ and further characterized by means connecting said startv generator and initial condition circuit for blocking the connection between said input and integrator during a counting cycle.
4. An analogue to binary code converter according to claim 2 and further characterized by said blocking means additionally comprising a diode bridge and voltage storage means for reverse biasing said diodes.
5. An analogue to binary code converter according to claim Si and further characterized by said modulator additionally comprising a diode gate for mixing said exponential sweep and said binary code output to produce a binary series of impulses having a count proportional to said signal voltage and having a steadily decaying amplitude arranged in a binary series. y
6. An analogue to binary code converter according to claim 5 and further characterized'by said exponential sweep having a half amplitude decay time equal to the time between pulses Yof said series of pulses.
7. An analogue to binary code converter according to claim l and further characterized by a monostable fliplop connected between said start generator and pulse train generator for turning on said pulse train generator for a period slightly less than said counting cycle.
S. Apparatus for converting an analogue input signal into a binary code output signal comprising a source of periodic .clock -pulses,'pulse `train generating means connected to said source for producing a train of pulses between said clock pulses, an exponential waveform generator connected to said source for producing a voltage waveform whose amplitude decreases one-half with each successive pulse of said pulse train, Ian integrator for storing the input signal voltage for `disc'harg-ein stepwave lform, V-trigger means coupled to said integrator and to said exponential waveiorm generator for producing output voltages whenever the output Voltage of said waveform generator is equal to or lessthan lthe output voltage of said integrator, said output voltages thereby occurring at times corresponding to a binary representation of the portion of the 'input signal integrated, gating means lfor producing output pulses only when-the output pulses of said trigger means and of said pulse train generator are substantially in coincidence to thereby produce a binary coded pulse train, andy modulator means for modulating pulses passed by said gating means with the output of said exponential waveform generator to provide said integratorv with pulses 2,754,503 7/56 Forbes g 340-347 2,784,396. 3/57 Kaiser et al. 340-347 2,872,670 2/59 Dickinson v 340-347 2,941,196 6/ 60 Raynsford et al. 340-347 2,957,943 10/60 Rack 340-347 MALCOLM A. MORRISON, Primary Examiner. iRVlNG L. lSRAGOW, JOHN F. BURNS, Examiners,