US2480137A - System for producing amplitudemodulated pulses - Google Patents

Description

Aug. 30,719,49- w. D. HouGH'roN 2,480,137

SYSTEM Fon PRoDucING AMPLITUE-MQDULATED PuLsExs y' 3 Sheets-Sheet l Filed May 9, 1947 INVENTOR.

0 ,f M W L/ M t Y WW i fvwm/##77124 E 1:: LII u .WJ/I

ma ay MM ATTORNEY W. D. HOUGHTON SYSTEM FOR PRODUGING AMPLITUDE-MODULATD PULSES Filed 'ay 9, 1947 INVENTOR.

ATTORNEY SYSTEM FOR PRODUCING AMPLITUDE-MODULTED PULSES N O T H G U O H D W Filed May 9, '1947K 3 Sheets-Sheet 5 #N0 fwwww www 72/56'5 TML INVNTOR.

ATTORNEY ltem.

Patented Aug. 30, 1949 SYSTEM Foa PRODUCING AMPIJ'rUDE- MoDULA'rsn rULsEs William D. Houghton, Port Jefferson, N. Y., assignor to Radio Corporation of America, a corporation of Delaware K Application May 9, 1947, Serial No. 747,105

21 Claims.

This invention relates to a method of andl means for producing amplitude modulated pulses of relatively opposite polarities in a'cornmunication transmitter system.

More specifically, the invention enables the production of plus and minus amplitude modulated pulses. The pulses generated in the system of the invention may have a positive polarity, a negative polarity or be of zero amplitude, depending upon the amplitude and polarity of the modulating voltage. When the modulating voltage is zero, no pulses are generated. When the modulating voltage is maximum and negative, the amplitude of the generated pulse is a maximum in one direction, and when the modulating voltage is maximum andpositive, the amplitude of the generated pulse is a maximum in an opposite v direction. The variations in amplitude of the generated pulses are made to be linear with respect to the modulating voltage.

The invention is especially useful in multichannel (multiplex) time division systems wherein a common transmission line is sequentially assigned to diierent channels each of whichhas its own modulation applied thereto. The common transmissionlne may feed any suitable radio frequency generator or transmitter circuit -for modulating the carrier wave, but it is preferred to utilize the amplitude modulated pulses to shift Y the frequency of a frequency modulation transmitter about its mid-carrier frequency; and since no pulses are produced in the absence of modulation, full advantage may be taken of the noise limiting qualities of a frequency modulation sys- A more detailed description of the invention follows in commotion with a drawing, wherein:

Fig. 1 illustrates, diagrammatically, the transmitting end of a multi-channel pulse communi-k cation system in which the invention may be employed;

Fig. 2 illustrates the circuit details of a channel unit and the common output equipment embodying the principles of the invention;

Fig. 3 is a series of curves graphically illustrating voltage waveforms at different points of the circuits of Figs. 2, 4 and 5 given in explanation of the operation of the invention; and

Figs. 4 and 5 show other embodiments 'of the invention. e.

Referringto Fig. 1 in more detail, this gure shows transmitting apparatus for a, plurality of channels each of which is supplied with its own signal modulation. A crystal oscillator A is employed to lock in a pulse oscillator B. The output from pulse oscillator B is coupled through lead I to a step voltage wave generator G. The step voltage wave output from generator G is coupled through lead ||2 to the inputs of a plurality of channels suitably labeled as channel l units I, 2, 3, etc. Each channel unit produces two simultaneously occurring" pulses whose amplitudes are differentially modulated in accordance with the modulation applied to that channel. The two pulses from each channel unit are fed to a common channel combining unit |24 which converts the two pulses to a-single pulse whose amplitude is modulated plus and minus about zero or ground potential. The variations in amplitude of this single pulse are made linear with respect to the modulating voltage. Channel units l, 2 and 3 are shown diagrammatically connected to the channel combining equipment |24 over leads IIB, H9 and |20. respectively.- A synchronizing pulse generator D produces a synchronizing pulse of longer duration than the channel output pulses immediately after the discharge of the step wave generator G, and is controlled by the generator G over lead H3. The combined channel output pulses from combining equipment |24 plus the synchronizing pulse 'are fed to the common ampliiier |25, which ampllfies the pulse train in preparation for modulating a radio frequency transmitter T. The synchronizing pulse generator D is coupled to the amplifier |25 through lead H1, while the amplitude modulated channel pulses from the common channel combining unit are fed to this same amplifier over lead |30.

The crystal oscillator A produces a. sine wave output whose positive or negative portion controls the production of a pulse from pulse oscillator B. The oscillator A may be any L. C. or R. C. type depending upon the stability requirements of the system. .The pulse oscillator Bvmay be a blocking type pulse oscillator which produces D.C. pulses `at the frequency of the crystal oscillator A. The

time constants of the pulse oscillator B are so chosen that the natural frequency of operation of the pulseoscillator is slightly lower than the frequency of the crystal oscillator.

The step wave generator G produces a stair or step voltage wave havingy a plurality of risers of substantially the same amplitude range but of different voltage values relative to a base line. A condenser in the step wave generator stores or collects the incremental charges passed thereto by the pulse oscillator, until a predetermined peak or total voltage is reached after which it discharges. There are two outputs from the step wave generator, one of which is the stair or step voltage wave available on lead I I2 and the other of For a more detailed description o! suitable circuits which may be used for the crystal oscillator A, pulse oscillator B and step wave generator G, referenceis made to my copending application Serial No. 608,957, tiled August 4.1945.

Fig. 2 illustrates the circuit details of a channel unit, it being understood that all channel units are identical except for the bias adjustment. This ligure also illustrates the common channel combining equipment I 2l which is fed by all channels.

Each channel unit includes a selector vacuumtube 8 which is biased to be normally non-conducting by an adjustable tap 89 on the cathode resistor 8. It. will thus be seen that resistor 8 is variable. The step wave output from the step wave generatoris ted to the grid of the tube 6 t'. rough a grid current limiting resistor I. Resistor I limits the maximum grid-to-cathode potential. The tube I is biased so that it becomes conducting on a particular riser yof the applied step voltage wave. yWhen tube 6 becomes conducting, the current in this tube rises i'rom zero to a maximum value and remains at`this maximum value i'or'the duration of the applied step wave. AThe condenser 1 in parallel to the cathode resistor 8 servesto bypass A.C. components of cathode current -to ground. The anode of tube 6 is connected through resistor 2 to the positive terminal B+ of a source oi.' D.C. potential.

It should be understood at this time that the inputs of all selector tubes in the diilerent channels are fed in parallel by the applied step voltage wave, and that Athe selector tubes in the different channels are dill'erently biased to become conducting on diflerent risers of the applied step wave, as a result of which the pulses produced in the diil'erent channels occur sequentially Vat different time intervals.

The anode of selector tube`8 is also coupled to the grid of a normally conducting vacuum tube 9 through a condenser 5.' The grid of tube 9 is also connected through a resistor 3 to the terminal B+. The combination of condenser and resistor 3 forms a diierentiator circuit. The anode of tube 9 is connected to the same B+ terminal through a resistor l, while its cathode is connected to ground through aresistor I0.

A pair of triode vacuum tubes II and I2 of similar characteristics have their cathodes directly connected together and'to the cathode of tube 9, as a result of which resistor I0 is a common cathode resistor for all three vacuum tubes 9, II and I2. The ilow of current through 'normally conducting tube 9 produces a voltage drop across resistor I0 which is sufficient to bias tubes and I2 below cut-oil. 'I'he value of resistor I0 is so chosen that when tube 9 ceases conducting, the reduction of the bias voltage developed across this resistor enables tubes II and I2 to operate as` class A amplifiers. For this reason, tube 9 can be considered as a gata A source of audio modulation i'or the channel is supplied to the grids oi' tubes I I and I2 in push.. pull or outy-of -phase relation through transformer I3. The anodes of tubes I| and I2 are individually connected to the B+ terminal through equal value resistors Il and I5, respectively, and arev also coupled through condensers I6 and 1, respectively, to the grids of vacuum tubes 28 and 20.

Tube 20 acts as a class Aampliner and has its anode connected through a resistor I8 to the i condenser I9 to the grid of a triode vacuum tube which is the discharge pulse available on lead I I3.

2| also operating as a class A amplifier.

Tube 28 also operates as a class A amplier and has its anode directly connected to the anode oi ampliiler tube 2|. Both ampliiers 2| and 28 are identical. A common load resistor 29 connects the anodes of the two tubes 2| and 28 to the B+ terminal. The cathodes of tubes 2| and 28 are directly connected together, and to ground through a common cathode resistor 21.

The anodes of tubes 2| and 28 are coupled through a condenser 30 to the grid of a triode vacuum tube 33 operating as a class A ampliiler. The anode of tube 33 is connected through a resistor 3| to the B+ terminal, and is also connected through a coupling condenser 32 to the output lead |30 extending to the common ampliiler |25. Plus and minus (positive and nega.- tive) amplitude modulated pulses are derived from the common channel combining equipment |24 on lead |30. The manner in which this is accomplished will now be described more fully.

Tube 6 is biased to be normally non-conducting and is made to start conduction on any desired step riser by adjusting the value of the bias voltage developed across yvariable cathode resistor 8. When tube 6 becomes conducting its anode potential suddenly drops to a low value, causing normally conducting tube 9 to be cutoli. Tube 9 remains cut-oil for a time determined by the time constants of the differentiating network 3 and 5. Vacuum tubes II and I2 are normally non-conducting due to bias vdeveloped across resistor I0 when tube 9 is conducting. The

value of resistor I0 is so chosen that when tube 9 is cut-olf, tubes II and I2 are biased as class A ampliiiers. Hence, two negative going pulses (one across resistor I4 and one across resistor I5) are devoleped when tube 9 is cut-oil. The duration of these negative pulses is equal to the cut-oil time of tube 9, and is determined by the diierentiating network 3 and 5. When no modulation is present on the channel, the two pulses are equal in amplitude. When modulation is present on transformer I3, the amplitude of the pulses vary linearly in a push-pull manner. That is, as the pulse across resistor I 4 increases in amplitude, the pulse across resistor I5 decreases in amplitude by an equal amount.

The operation of the common circuit is as follows: The negative pulse across resistor; I5 is coupled to class A ampliiler 20. The amplication factor of 20 is made unity, hence a positive pulse equal in magnitude to the negative pulse across resistor I5 is developed across resistor I8. Tube 20 can thus be considered a phase inverter tube. The pulse developed across resistor I8 is coupled to the grid of class A amplier 2|, while the pulse developed across I4 is coupled to the grid of class A amplier 28.

For the condition where the channel is unvmodulated, the negative pulse across resistor lI4 ythe pulse across resistor Il. Therefore, since the grid of tube 2| is driven positive by -the same amount the grid of 28 is driven negative, there is no voltage change across resistor 29 and no pulse present to drive output tube 33. For the condition where modulation is present on transformer I3 and the grid of tube I2 is made more positive than the grid oi.' tube II. the negative pulse across resistor I5 is greater in amplitude than the negative pulse across resistor' Il. Hence i the positive pulse on the grid of tube 2| is greater in amplitude than the negative pulse on the grid of tube 28 and a negative pulse is developed across resistor 23 which results in a negative pulse being applied to the grid of tube 33, and as a consequence a positive pulse being developed at the oi tube 2| is driven positive, and hence a positive pulse is. developed across the grid of tube 33 resulting in a negative pulse being developed comes conducting its anode potential suddenly.

drops to a low value and remains at this value for the remainder of the applied step voltage wave cycle.

Fig. 3, curve C represents the waveform de veloped across cathode resistor I0 which is common to tubes 9. II and I2, the dash-dot line labelled Y indicates the potential below which tubes II and I2 become conducting.y The length or duration of these pulses is determined by the R. C. constants of differentiating network 3 and 5 which diierentiate the negative going edge of the anode voltage wave of tube 6, Fig. 3, curve B.

Fig. 3, curve D shows the Waveform of the modulating voltage applied to the grid of tube Iii, and Fig. 3, curve E the waveform ofthe modulating voltage applied to the grid of tube I2. The waveform of Fig. 3, curve Ebears a 130 out-of-phase relationship with that of Fig. 3, curve D. i

Fig. 3, curve F represents the negative going pulses on the anode of tube I2, and Fig. 3, curve G the negative going pulseson the anode of tube ii. tive pulses of Fig. 3, curve F and Fig. 3, curve G are equal in amplitude. This is due to the fact that at the time of conduction of tubes II and I 2, the applied modulating signals are passing through zero.

Fig. 3, curve H shows the positive pulses at the grid of tube 2i. These pulses are equal in amplitude but 180 out-of-phase with those appearing on the anode of tube I2 (Fig. 3, curve F).

Fig. 3, curve I shows the plus and minus pulses as they appear on lead |30 at the output terminal. It vshould bev noted that there are no pulses appearing at times R, S, and T since at these` points the two sine waves Fig. 3d and 3e are at zero amplitude and the positive pulses in Fig. 3h are equal and opposite to those in Fig. 3g; resulting in the increase in current in tube 2I being exactly balanced by the decrease in current 'in tube 23.

'I'his balance occurs when tubes II and I2 are made conducting at a time when the modulating waves applied to their grids have zero amplitude. At all other times, a' pulse will appear and will It will be seen at time R, S, and T the negabe either positive or negative. depending upon which tube (II or I2) carries the greater amount of current when it-is made conducting. vIn multiplex systems.` the time interval between adjacentl pulses, curves F, G and H oi Fig. 3, contain yall the other channel pulses. -It will ,thus be seen that -the unal output pulses from eachchannel are either positive or negative in sign and are amplitude modulated. The

final output pulses from the different channels occur at diierent time intervals.' For each cycle of operations represented by a single complete step voltage wave, there will be a pulse from each channel unit in the presence of modulating voltage, and this pulse will be either positive or negative, and the pulses from the diilerent f channels occur sequentially. In the output of the common ampliiier I25. each cycle of operations will also include a synchronizing pulse of longer duration than the channel pulses and which occurs at the end of the step voltage wave, or after all the channels have each produced one pulse. 'I'he synchronizing pulse may have an amplitude equal to or 'slightly .greater than the maximum amplitude of any channel pulse .under extremes of modulation. The synchronizing pulse may be smaller in amplitude if the receiving equipment is designed to acceptit. Y

Figs. 4 and 5 show other embodiments of the invention which are not as desirable as Fig. 2 when using a large number of channel units, on account of the greater tendency for cross-talk in the systems of Figs. 4` and 5, but are desirable for smaller systems due to their simplicity. The same parts which appear in al1 three figures have been given the same reference characters.

Figs. 4 and 6 employ a transformer 60 in the channel unit for producing the desired plus and minusfoutput pulses. The operation of Fig. 4 may be understood by reference to the curves A to I qi? Fig. 3. Fig. 3 curve A shows the step voltage wave applied to the grid of selector tube 6. Let it be assumed that the tube 6 of Fig. 4 is so biased as\'to become conductive on the second riser of the step waveof Fig. 3, curve A. 'I'he horizontal dash line p in- Fig. 3, curve A indicates the point of conduction and the horizontal dash line :r indicates the level at which the grid-to-cathode potential of tube 6 reaches zero. The anode. potential of tube 6 is shown in Fig. 3, curve B 'for the condition assumed above. On the negative going edge vo f the voltage wave 'across resistor 2, the normally conducting gate tube 9 is cut-off for a time interval determined by the time constants .of diierentiating network 5, 3. The negative pulses of the curve C of Fig. 3 indicate the intervalsv during which tube 9 is cutoE. When tube 3 is cut-oi! the potentialv across resistor I0 drops, as a result of which tubes II and I2 conduct and actas class A ampliiiers during the cut-oil? time of tube 9.

Fig. 3 curves D and E indicate the audio modulation voltage applied to the grids of tubes II and I2 by transformer I 3. These voltages are identical but out-of-phase, that is, transformer I3 feeds the grids of II and I2 in a push-pull manner well known in the art. The waveform F of Fig. 3 represents the negative voltage pulses appearing on one-half of the primary winding of transformer B0 due to current in tube I2 while Fig. 3 curve G represents the negative voltage pulses appearing on the other half of the primary winding of 60 due to current in tube II. Curve I of Fig. 3 representsthe plus and minus pulses as they appear across the secondary winding oi transformer 69. are no pulses appearing at times R, S, and T in Fig. 3, curve I since at these times the modulating voltage is passing through zero and the voltage on the grid of tube II is equal tothe voltage on the grid of tube I2 and hence they carry equal currents when conducting and since transformer 60 is a push-pull type there is no change in voltage across the secondary winding. However, in the presence of an audio voltage on transformer I3, if the grid-to-'cathode potential of tube II is made more positive than the grid-to-cathode potential of tube I2, a pulse is developed across the output winding of transformer 60 of a. polarity depending upon the connections of the transformer. On the next half cycle of the audio voltage. tube I2 carries more current than tube II and hence a pulse of opposite polarity is developed across the output winding.

' Fig. 5 shows a modification of the system of Fig. 4 in which push-pull transformer I3 of Fig. 4 is replaced by a phase inverter tube 49. The operation of this circuit follows:

A step voltage wave as shown in curve A of Fig. 3 is coupled to the grid of normally non-conducting tube 6. Tube 6 is biased to become con- It will be noted that there ducting on a. particular step riser as previously l,

described. When tube 6 becomes conducting its anode potential suddenly drops to a low value (see curve B of Fig. 3) and remains at this low value for the remainder ofthe step wave cycle. The negative going or falling edge of the voltage wave on the anode of 6 is differentiated by the differentiating network consisting of 3 and 5. Thus a negative'pulse is developed on the grid of normally conducting tube 9 sufficient to cause it to cease conducting. Tube 9 remains cut-off for a period of time determined by the values of 3 and 5.

When-tube 9 is conducting it develops a .voltage across resistor I0 suiilcient to maintain tubes II and I2 cut-off. Hence when tube 9 buts off tubes I I and I2 become conducting. The value of I0 is so ,chosen that tubes I'I and I2 operate as class A ampliers during the time they are conducting. .The voltage developed across resistor I0 is as shown in c urve C of Fig. 3. Tube 49 is a conventional phase inverter tube which produces a voltage across its plate resistor which is equal to and 180 out-of-phase with the voltage developed across its cathode resistor. The voltage developed yacross the anode resistor 20 of tube 49 iscoupled to the grid of tube II via coupling condenser I6 and the voltage developed across the cathode resistor I8 of tube 49 is coupled to tube I2 via coupling condenser I1. Elements II4 and I'I5 are the grid leak resistors for tubes II and I2 respectively. The modulating signal appearing across grid resistor II4 is shown in curve D of Fig. 3 and the signal appearing across resistor II 5 is shown in curve E of Fig. 3.

The negative pulse voltage across one-half of the primary of 6D due to pulse currents in tube- I2 is shown in curve F of Fig. 3, while the negative pulse voltage across the other half of the primary of 60 due to pulse currents in I I is shown 8 than that on the other and when they become conducting (tubes II and I2) a pulse will appear on the output, the polarity being a function of the tube carrying the greater current and the amplitude being a function of the degree of unbaiance in the grid voltages.

It will be understood that it is not necessary to employ individual tubes for the triode electrode structures, since if desired, a dual or twin triode tube can be used which contains two electrode structures within a single evacuated envelope.

What is claimed is:

1. In a pulse generating system, the method which includes producing two simultaneously occurring pulses of the same relative polarity, different'ially modulating said pulses in accordance with a signal, and converting said two pulses to a single pulse whose amplitude is modulated plus or minus relative to a reference value.

2. In a pulse generating system, the method which includes producing a pair of simultaneously occurring pulses of the same relative polarity, equalizing the amplitudes of said pulses in the absence of modulation, varying the amplitudes of said pulses diilerentially and linearly in accordance with a modulating signal, and converting said pair of differentially modulated pulses to a singlepulse which has one polarity when one pulse of said pair has a larger amplitude than the other, and which has an opposite polarity when said'one pulse has a smaller amplitude than the other.

3. In a pulse generating system, the method which includes producingftwo simultaneously occurring pulses of equal amplitude and of the same relative polarity, modulating the relative amplitudes of said pulses in accordance with 'a modulating voltage. controlling the ow of space current vin one path by one of said pulses, controlling the flow of space current in another path by the other of said pulses, balancing outv the effects of the ow of current in said paths when the pulses are of equal amplitude, causing a greater ilow of current in one path compared to the other path when said pulses are of different amplitudes, and utilizing said difference in current ow to produce a pulse in one direction or the other depending upon which path has the greatest current ilow.

4. In a pulse generating system, the method which includes producing first and second simultaneously occurring pulses of negative polarity and of equal amplitudes, differentially modulating l the amplitudes of said negative pulses in accordance with a modulating signal, obtaining a positive pulse from, said first negative pulse and of the same relative amplitude, controlling the flow of space current in one path by said positive pulse,

in curve G of Fig. 3. The resulting plus and minus amplitude modulated pulses are shown in curve I of Fig. 3. I

It should again be noted that when the tubes II and I2 conduct-when the modulating voltage is passing through zero no voltage is developed on the secondary of 60. This is due to tubes II and I2 carrying equal currents. When the voltage on the grid of one tube has a magnitude greater controlling the flow of space current in another path by said second negative pulse, balancing out the controlling eiects of said positive and said second negative pulses, only when said iirst and second negative pulses have equal amplitudes,

and utilizing any difference in the controlling effects caused by said differential modulation to produce a pulse whose sense depends upon which path carries the greater ilow of current and whose magnitude depends upon the extent of the dierence in current flow in the two paths.

5. In a pulse generating system, the method which includes producing a pair of simultaneously occurring pulses of the same relative polarity, equalizing the amplitudes of said pulses in the absence of modulation, varying the relative am- 76 plitudes of said pulses linearly In accordance with function of the modulating voltage and which has one polarity when one pulse oi' said pair has a larger amplitude than the other, and which has an opposite polarity when said one pulse has a smaller amplitude than the other.

6. A pulse generating system comprising a ilrst vacuum tube electrode structure biased to be normally non-conducting, a circuit for supplying a recurring waveform to said rst structure of a polarity and magnitude to render it conducting at the frequency of said waveform, a second vacuum tube electrode'structure biased to be normally conducting, a diflerentiator circuit coupled between the output of said ilrst structure and the input of said second structure, to thereby cause said second structure to cease conducting in re- Y fio' to a single'pulse whose polarity depends upon which electrode structure oisaid pair passes the greater amount of current 'and whose magnitude depends upon the extent of difference4 in the amounts of current iiow through both electrode structures. A

10. A pulse generating system comprising a pair of vacuum tube electrode structures, each including a control electrode and an anode. a circuit sponse to the conduction condition of said iirst space paths being biased to be non-conducting in the normal conduction condition of said second structure and passing current during the nonconducting condition of said second structure, means for did'erentially controlling the flow of current in said space paths in accordance with a modulating voltage, and means for deriving vfrom said space pathsa pair of differentially modulated pulses having variations in amplitude which' are linear with respect to the modulating voltage.

7. A pulse generating system comprising a pair of electrode structures each including an anode and a control element, cathode means for said structures, a. bias element in circuit with said cathode means for normally biasing said electrode structures below cut-oir, individual impedances in circuit with the anodes of said structures, a circuit for periodically overcoming the cut-oil bias of said structures to thereby render them conducting, a modulating circuit coupled to said control elements in push-pull relation, and means coupled to said impedances for deriving diierentially modulated pulses.

8. A pulse generating system comprising a. pair of electrode structures each including a cathode, an anode and a grid. a common cathode resistor for said structures, individual resistors connected between said anodes and the positive terminal of a source of D.C. potential, a circuit for causing current to ilow periodically through said cathode resistor to thereby periodically cause said electrode structures to conduct, means coupled to said grids for supplying a modulating voltage to said grids in opposing phase relation, and'leads cou'- pled to said individual resistors for deriving therefrom a pair of simultaneously occurring pulses of the same relative polarity but whose amplitudes vary in dependence upon the modulating voltage.

9. A p'ulse generating system comprising a pair of electrode structures each including a cathode,

' an anode and a grid, a common cathode resistor tor periodically causing said structures to become simultaneously conductive and then non-conductive, a circuit for supplying a modulating voltage to the control electrodes of said pair of vstructures in out-of-phase relation, and leads coupled to said anodes for deriving from said structures a pair of simultaneously occurring pulses of the same relative polaritywhen said structures simultaneously chan-ge from one current condition to the other.

11. AA pulse generating system comprising a pair of vacuum'tube electrode structures, each including a, control electrode and anode, a circuit for periodically causing said structures to become simultaneously conductive and then non-conductive, a. circuit for supplying a modulating voltage to the control electrodes of said pair of structures in out-.of-phase relation, individual resistors connected between the respective anodes and the positive terminal of a source of D.C. potential, and means connected to said anodes for deriving therefrom a pair of simultaneously occurring pulses of negative polarity when said structures change from the non-current passing condition to the current passing condition.

12. A pulse generating system comprising a pair of vacuum tube electrode structures, each including a control electrode and an anode, a. circuit for periodically causing said structures to become simultaneously conductive and then nonconductive, a circuit for supplying a modulating voltage to the control electrodes of said pair of structures in out-of-phase relation, individual resistors connected between the respective anodes V Aand the. positive terminal of a source of D.C.

^ modulating voltage, controlling the flow o! space f l 'current in one path by one of said pulses, conpotential, a phase inverter amplifier coupled to "the anode of one of said structures, a second amplifier coupled to the anode of the other structure, a. third amplifier coupled to the output of said phase inverter, a common load resistor for said second and third ampliers, and means coupled to said common load resistor for deriving therefrom a pulse whose polarity may be either plus or minus depending upon which one of said electrode structures carries the greater current during the time both electrode structures are simultaneously conductive.

13. A pulse generating system including means for producing a pair of simultaneously occurring pulses of the same polarity whose relative amplitudes vary linearly in response to a modulating voltage, and means :Ior converting said pair of pulses to a single pulse whose polarity depends uponwhich one of said pair of pulses has the greater amplitude and whose amplitude depends upon the extent of difference in amplitudes of said .pair of pulses.

f 14. In a-pulse generating system, the method which includes producing tw simultaneously occurring pulses of equal amplitude and of the same relative polarity, dinerentially modulating the amplitudes of said pulses in accordance with a r trolling the ilowof space current in another path by the other of said pulses, balancing out the effects of the iiow of current -in said paths when er ilow of current in one path compared -to the other path when said pulses are of diiferent amplitudes, and utilizing said difference in current flow to produce a pulse in one direction or the other depending upon which path has the greatest current iiow, said last means comprising a phase inverter amplifier fed by one of said pulses of said pair, a' second amplifier coupled to the output of said phase inverter, and a third ampliiler fed by the other pulse of said pair, there being a common load resistor for said last two amplifiers, and an output circuit coupled to said common load resistor.

15. A system for converting a pair of simul taneously occurring pulses of the same polarity and whose amplitudes vary differentially in ac-4 cordance with a modulating voltage to a single pulse, including a phase inverter amplier fed by one of said pulses of said pair, a second amplifier coupled to the output ofsaid phase inverter, and

ins a grid, anode and a cathode, a diiferentiator circuit coupled between the anode of said rst structure andthe grid of said second structure, third and fourth electrode structures each including grid, cathode and anode electrodes, a commoncathode resistor for the cathodes of said second, third and fourth electrode structures, whereby the voltage developed across said common cathode resistor due to current flowing in said second structure biases said third and fourth structures below cut-olf, a transformer having a primary winding coupled across the anodes of the third and` fourth structures, and a secondary winding for deriving output pulses from said transformer, and a circuit for applying a recurring waveform lto the grid of said iirst structure of such polarity and magnitude as to cause said first structure to.

conduct, to thereby bias/said secondv structure to the anode-current cut-oi! condition and cause said third and fourth structures to conduct.

17. A pulse generating system comprising a' first normally non-conducting electrode struc' ture having a grid, anode and a cathode, a second normally conducting electrode structure having a grid, anode and a cathode, a differentiator circuit'coupld between the anode of said 12 condition and cause said third and fourth tures to conduct, said common cathode resistor having such value that said third and fourth electrode structures operate as class A amplifiers ture having a grid, anode and a cathode, a second normally conducting electrode'structure having a grid, anode and a cathode, a diiferentiator circuit coupled between the anode of said first structure and the grid of said second structure. third and fourth electrode structures each including grid, cathode and anode electrodes, a common cathode resistor for` the cathodes of said second. third and fourth electrode structures, whereby the voltage developed across said common cathode resistor due to current flowing in said second structure biases said third and fourth structures below cut-oil, a transformer having a primary winding coupled across the anodes of the third and fourth structures, and a' secondary winding .for deriving output pulses from said transformer,

and a circuit for'applying a recurring waveform to the grid of said first structure of such polarity and magnitude as to cause said first structure to conduct, to thereby bias said second structure Ato the anode-current cut-off condition and cause said third and fourth structures to conduct, said common cathode resistor having such value that said third and fourth electrode structures operate as class A amplifiers wlen said second structure is biased below cut-off, and means for applying -a modulating voltage to atleast one of said third and fourth electrode structures.

19. A pulse generating system in accordance with claim 18, characterized in this, that said last means includes a phase inverter tube. f

20. In a pulse generating and modulating system, the method which includes producing two simultaneously occurring pulses of the same rela- Vtive polarity and equal amplitude in the absence of modulation, modulating the amplitudes of first structure and the grid of said second structure, third and fourth electrode structures each Y including grid, cathode Iand anode electrodes, a

common cathode resistor'for the cathodes of said second, -third and fourth electrode structures, whereby the voltage developed across said ccmmon cathode resistor due to current iiowing in said second structure biases said third and fourth structures belowcut-oii. a transformer having y a primary winding coupled across the anodes of `7i) Numbersaid pulses relative to each other in accordance with a signal, and convertininsaid two pulses to a single pulse whose ampli de is modulated `plus or minus relative to a reference value.

conductive,means biasing said structures to operate as class A ampliers when they become conducting, a circuit for supplying a modulating voltage to the control electrode ofatleast one vof said structures, and leads coupled to said anodes for deriving from said structures a pair of simultaneously occurring pulses of the same relative polarity when said structures simultaneously change from onev current condition to the other.

WILLIAM D. HOUGHTON.

REFERENCES The following references are of record in the ille of this patent:

, STATES PATENTS Name Date 2,411,062 Schade Nov. l2, 1946 2,415,359

Loughlin Feb. 4, 1947

Images