US2839702A - Modulated distribution system - Google Patents

Description

June 17, 1958 SlN-PIH FAN EIAL MODULATED DISTRIBUTION SYSTEM Filed July 24, 1953 MULTI- POSITION BEAM POSITIONING MEANS MODULATION MAGNETRON BEAM 3 Sheets-Sheet 1 SWlTCHlh G TUBES.

SERIES BEAM SYSTEM CURRENT REGULATOR ll 1 L w DISTRIBUTION V SYSTEM June 17, 1958 SIN-PIH FAN ET AL 2,839,702

MODULATED DISTRIBUTION SYSTEM Filed July 24, 1953 '3 Sheets-Sheet 2 UTILIZATION SYSTEM 20 COMMUTATING MEANS MODLLATION SYSTEM BEAM REGULATOR I FIG. 4

wuwmmaunv-o MODULATION SYSTEM INVENTORS SIN- PIH FAN SeUL KUCHINSKY June 17, 1958 SIANPIH FAN ETAL 2,839,702

MODULATED DISTRIBUTION SYSTEM Filed July 24, 1953 :5 Sheets-Sheet s ls LDISTRIBUTION UTILIZING SYSTEM k k 1 20B 32A 3L5 I 55 PERIODIC BISTABLE TRIGGER STATE PULSES FLIP-FLOP FIG. 5

l8 MODULATION SYSTEM Ill 4e l3 |l POSITIONING SELECTOR HEQY OUTPUT CHANNELS; MEANS MEANS TUBE #|EI IE] I A 58 ,IS I'? SAMPLE PULSE MODULATION EX ERNAL BEAM v 7 soURcE MEANS 'CURRENITREGULATOR 59 OUTPUT OEENEROIZI O PULSE v Is BEAM m SELECTOR w OUTPUT 3.- TUBE SW L CHANNELS V 1 7 FIG. 8,

I l7 l8 I SAWTOOTH EXT RNAL BEAM MODU DEFLECTION I MEANS CURRENT REGULATOR SO '"IYI "JRI ?=A $IUL KUCH mSKY U i es P mfi ,R t' ed J n y,- 1.9

MODULATED DISTRIBUTION SYSTEM Sin-Pih Fan, Marlton, N. J., and Saul Kuchinsky, Philadelphia, Pa., assignors to Burroughs Corporation, De troit, Mich., a corporation of Michigan Application July 24, 1953, Serial No. 370,134

4 Claims. (Cl. 315-9) This invention relates to amplitude-responsive, multiple-channel distribution systems, and particularly to such systems utilizing multi-position electron beam switching tubes.

Multiple position beam switching tubes are known in the art. Improved tubes of this type are disclosed in a copyrighted paper entitled "Multi Output Beam Switching Tubes for Computers and General Purpose Use presented by Saul Kuchinskyat the March 1953, convention of the Institute of Radio Engineers in New York,

Briefly, a multi-position beam switching tube of the type referred to is one in which the switching is accomplished by deflecting an electron stream or beam from one electrode to another at a desired rateior pattern, or

both.

structurally, a tube of the general type referred to above may comprise, within an hermetically sealed envelope, an elongated cylindrical cathode around which are disposed coaxial and concentriearrays of electrodes.

The array nearest the cathode comprises a plurality of trough-shaped elements, known in the art as spades, radially. disposed with respect to the cathode. Surrounding the first array may be a tubular slottedor apertured anode electrode, the slots or apertures being disposed between the areas of the electrode which are radially opposite the trough-like elements. Another array of electrodes, the array farthest removed from the cathode, may

comprise either a single tubular collector electrode or aplurality of collector electrodes radially, aligned with said apertures or slots in the anode electrode. The collector electrode or electrodes may be utilized. as the output means for the tube. Because the tube is intended to be used in conjunction with a magnetic field whose lines. of

force extend through the tube in a direction substantially parallel with the longitudinal axis of the cathode, it is desirable that the electrodes be made of non-magnetic mastrength and direction to overcome the attractive force of the rather symmetrical electric field forthe electrons emanating from the cathode and out otf the1tube. That is,.the electrons are forced, by the magnetic field to follow curved paths around the cathode and are prevented from reaching the spade electrodes.

If, however, one of the spade electro'des is reduced in potential, to somewhere near the cathode. potential, for

example, the symmetry of the electric field is changed to the extent that the effect of the magnetic field in cuting off the tube is modified in the area of the spade'haymg the reduced potential and electrons are attracted to Applicants structure is s'uchthat, although" that spade. some electrons do impinge on the spade, the majority of the electrons are attracted to one of the more positively, charged adjacent target electrodes. Sin-ce'there are target electrodes on each side of each spade, the target electrode on which the electronswill impinge depends on the polarity of the magnetic field, for this field determines the di-' open channel locating, coding and quantizing apparatus. Some general requirements desirable in such systems are:

high switching speed capabilities, amplitude response for modulation in the order of 100%, stability, simplicity and efficiency. Prior art system have not been entirely satisfactory in providing all these characteristics. When the prior artv distribution systemsin order to simplify circuitry, have utilized multi-position switching tubes,'

high percentages of modulation. have been diflicult to obtain without disturbing the switching stability. ForQ example-a control grid assembly maybe associated with a multi-position. beam switching tube, but .since the change in the field configuration resulting from a mqdu I for the in many cases.

lating signal being applied to the control grid, maybe inconsistent with the switching stability requirements,

modulation of such a tube by the u sual control grid conff figuration does not atford optimum switching operation This is particularly true when 100%? modulation is approached. Thus multi-position beam; switching tubes of the prior art haveb n t gating or distribution functions than formodulation. a

ula'ted' signals.

A primary object of the invention is to 'providean" system utilizing multi-position improved modulation beam switching tubes. It is another object of the invention to provide "stable' vide a modulation system formulti-position beam switch- 3 ing tubes in which 100% modulation may be approached '--cordance with the present invention by providing "ex ternal modulation means for controlling beam current .lated signals.

switching systems for Accordingly it is a general object'of the invention to provide improved distribution systems responsive to modeconomically distributing modur,

Further it is an object of the present invention to pro-f;

while maintaining good switching stabilityand aminimum of cross talk. 7 i The foregoing and related objects are achieved in acin a multi-position magnetron-type beamswitching tube in which crossed electric and magnetic fields are utilizedi Thus, a modulatedrbeam-current' regulator device'may be connected in series with' the beam discharge path. To stabilize the switching characteristics with-such modula-, tion, beam positioning and holding circuitry external to the tube is used to direct the beam to any one of itsi positions and hold it there during modulation excursions.

.-.Alternatively, particular tube electrode, structure may be chosen to afford improved beam switching in the presence of modulationfrom the externalbeam current regulation system with internal beam holding bybeam current impinging upon a holding electrode.

In either, i manner percentage of modulation in the order of Other. objects and .featuresof advantage will be found I throughout thefollowing, more detailed description of the invention, which is described with reference to the accompanying drawing, wherein:

Fig. l is a block diagram of a modulated distribution system constructed in accordance with the invention;

Fig. 2 is an isometric view, partly in section, of a multi-position beam switching tube which may be utilized in the present invention;

Fig. 3 is a plan view taken along line 3--3 of Fig. 2;

Figs. 4 and 5 are diagrammatic views of magnetron type beam switching tubes and accompanying block diagram circuits of the invention;

Fig. 6 is a schematic circuit diagram of a modulated distribution circuit embodying further aspects of the invention; and

Figs. 7 and 8 are block circuit diagrams illustrating different features of the invention embodied in the circuit of Fig. 6.-

These portions of the invention which may be found in the prior art, and whose details of themselves form no part of the illustrated embodiments of the invention, are shown in block diagram form to more definitely point out the features of the present invention. Throughout the respective views, like circuit elements will be designated with similar reference characters to facilitate comparison of the different embodiments. 1

With reference to Fig. l of the drawing, a beam switching tube 11 is shown in block diagram form. Switching tube 11, may for example, be of the variety shown in Figs. 2 and 3, or tubes disclosed in the Kuchinsky paper referred to above, or similar tubes.

Suitable beam positioning means 13 is provided for directing an output signal from the switching tube 11 to any one of the output leads 14. Beam positioning generally may be accomplished by varying the configuration of either the magnetic or electrostatic field or both, in a magnetron type switching tube, as is well known in the art. Any suitable distribution system 15 is coupled to the output leads 14 indicating the different beam switching positions of the tube 11. It is noted that the beam positioning means 13 may be either internal or external to the beam switching tube 11. As will be more clearly described hereinafter, counting or commutating means may be specifically coupled with different tube electrodes to select the desired output position, or the internal tube electrodes themselves may be utilized to cause either beam holding or automatic successive commutation of the beam.

Since a change of electrostatic field configuration in the beam switching tube 11 will tend to cause a change in the selected output position, it is extremely difiicult to modulate the output of the tube by medium of the usual control grid structure. Accordingly, with the present invention a series beam current regulator 17 is afforded for'externally modulating the amount of beam current variation in the switching tube 11 in accordance with any desired modulation signal afforded by the modulation system 18. In this manner, when the beam is held on a desired output position by means of beam positioning structure 13 external to the tube, the beam current of the switching tube 11 may be modulated to a degree approaching 100%. In this manner, the beam is held in position even during excursions to zero beam current.

Fig. 4 illustrates this type of construction in connection with a tube of the type shown in Figs. 2 and 3. This general type oftube is highly desirable for use in modulated systems since it provides a pentode type characteristic. That is, the beam current does not vary substantially with target potential variations. The modulated output signals may therefore be taken directly from the target electrodes when this tube is utilized. By means of the substantially U shaped target electrodes 20 and corresponding substantially V shaped spade electrodes '4 22, very little spade current flows and substantially the entire beam 23 is directed to the target electrode.

The tube, more clearly illustrated in Figs. 2 and 3, is generally of coaxial configuration with the elements concentrically arranged around the centrally disposed thermionic cathode 25 within an hermetically sealed envelope.

A magnetic field whose lines of force run substantially parallel to the cathode 25, is provided by the external magnet 26. An array of elongated trough-shaped elements or spades 22 is disposed along and about the cathode 25. The spades 22, as illustrated, are spaced substantially equi-distantly one from another and have the open side of the trough facing outwardly from the cathode 25. The number of spades is usually equal to the number of beam switching positions.

Another similarly disposed array of elongated troughshaped electrodes, the target electrodes 20, is further removed from the cathode than the spades 22. The sides of each trough-shaped spade electrode 22 interlock with or telescope over adjacent sides of adjoining target electrodes 20. Top and bottom mica spacers maintain the desired spacing between the spades 22 and target electrodes 20. Leads connected to the individual spades and to the target electrodes and to the cathode of the tube but not shown in Figs. 2 or 3 in order that the electrode structure be more clearly shown, are brought out through the stem to base pins. The tube is diagrammatically shown in Fig. 4 in order to simplify the description of the associated circuitry.

The beam positioning means 13 is a commutator device in this instance, which establishes one of the spade electrodes 22 such as spade 22A for example at low potential and holds the remaining spade electrodes at high potential. In this manner, the beam is caused to impinge upon the single target electrode 20A associated with the spade electrode 22A. Therefore, in this embodiment the spade potential is held at low potential by the external. commutator means 13, and the spade resistor 30 is chosen to have such low impedance that beam current flowing therethrough does not lower the spade potential enough to hold the beam thereon. In this manner, complete switching control is maintained by the external commutator 13 and modulation approaching may be readily attained with a series beam current regulator such as an electron discharge device 17.

As shown in Fig. 5 this general type tube is particularly desirable should the beam 23 be required to internally lock the beam in its selected output position, since even when beam current approaches cutoff sufiicient current is received by the spade electrode 22A that modulation approaching 100% may be accomplished without causing the beam to switch. In this intsance, the spade resistor 30 is made of such large impedance that beam current flowing therethrough from spade 22A will lower the spade potential enough to hold the beam locked in position upon target electrode 20A. For purposes of beam holding internal current flow may be made to hold the spade 22A at a low potential and assure direction of the beam to target electrode 20A. However, should the beam be modulated 100% and the beam current, therefore, disappears, the beanrwould not remain at target 20A but might switch to some other target such as 20b or become cutoff.

In this particular embodiment the switching tube has separate beam switching and beam holding electrodes. The beam switching electrodes are connected in two common sets 32a and 32b, which may be alternately established at high or low potential by the bistable state flip flop circuit 34 in the beam positioning means 13". For cyclic distribution, periodic trigger pulses may be generated in a suitable source 35 connected to the flip flop circuit complementing terminals C to provide synchronized control of the switching. Random timing may be obtained by providing random pulses to the same complementing terminal. Each of the beam Switching electrodes 32 is placed in such a position that they have no effect upon the formation of the beam 23 and therefore the beam is mainly caused to impinge upon a particular target because of the field established by the associated adjacent spade electrodes. Should the beam strike another spade electrode than 22A however, current flowing through the corresponding spade resistor would decrease the potential enough to cause the beam to switch thereto, if in the proper direction from the beam location as determined by the magnetic field orientation.

Thus, assuming a trigger pulse arriving at the flip flop circuit 34 to change output lead 37 to'low potential and the associated output lead 38 to high potential, the beam 23 will be diverted by the field about electrode 32b only in the region of the target electrode A to impinge upon the spade electrode 22b. This change of potential occurring only in the region of the target 20A defocuses the beam and makes it broader, shifts its position, or

both. The magnetic field orientation tends to cause the beam to travel towards spade 22b as shown in the drawing. Therefore, the beam will, upon, striking spade 22b, cause current flow through resistor to lower the potential of the spade 22b and switch the beam into the new position on target electrode 20b. Alternatively the use of discrete pulses to all control elements in common will cause automatic successive commutation. Change of target potential however has little efiect upon the beam 23. Accordingly, with this type of tube modulation may be readily accomplished even though the beam is held in position by internal beam current.

Should it be desired to randomly rather than successively distribute signals in a plurality of ordered channels, a circuit such as shown in Fig. 6 may be utilized. Because of the characteristics of the magnetron type switching tube, the beam tends to travel in a particular direction unless special precautions are taken. Therefore should it be desirable to randomly select any one of the ordered output channels 0 through 9, the electron beam in the switching tube 11' should be cutofi entirely and reformed in the desired position. A system of thistype is particularly described in the copending Kuchinsky application for Pulse Code Modulation System, Serial No. 304,344. Beam cutolf is accomplished by a negative sampling pulse of suitable amplitude at input terminal 40, which applied to the current regulator tube 17 will cutoff the beam of the switching tube 11". At the same time the sampling pulse forms a beam by energizing the cathode 41 of the beam positioning tube 13". This tube operates in a manner similar to the commutating means 13 of Fig. 2 in that the beam is selectively directed to any one of a plurality of output electrodes such as identified at 43 and cause current flow through corresponding output resistor 44 and thereby lower the potential of the spade 4 corresponding to the target electrode of the ordered output channel 4 in the switching tube 11". The selected output electrode of the beam positioning tube 13" is determined by the deflection potential applied to beam positioning means 46 at the time the sampling pulse occurs.

The beam switching tube 11 is another magnetron type of tube which is connected to operate in the manner previously described where beam current impinging upon a spade electrode holds the beam in position at a particular output target electrode. For purpose of simplicity, the spade circuitry is not shown. In this tube an anode 48 is provided with apertures therein to direct the beam to the desired targets by means of the field established betweeen two adjacent .spade electrodes. This tube is also desirable where variation of target potential does not substantially affect the beam formation provided by the anode 48 and associated spades.

' Regulator tube 17' in addition to its actiori'in suppress ing the beam current in switching tube 11" to facilitate switching of the beam, as above described, performs the modulating function of beam current regulator 17, shown in block form in other figures, under the influence of a variable'electrical signal applied by modulation system 18. Thus, the potential of the grid of tube 17 may be controlled eitherto vary the plate circuit impedance of the tube and thereby vary the current through tube 11""in a continuous manner or to efiect abrupt stopping and starting of this current.

In Fig. 7 a block diagram circuit corresponding to the schematiccircuit of Fig. 6 illustrates a manner in which this circuit is'utilized for random output channel distribution by means of beam positioning input signals. Accordingly sampling pulses provided by the source 55 aroused periodically, during occurrence of the pulse, to energize an output signal of selector means 13 by way of lead 58 and simultaneously de-energize the beam of switching tube '11 by'medium of lead 59 and external i random --order. a

For successive distribution of the signals, the circuit of Fig. 6 may be utilized as illustrated in the block diagram of Fig. 8. Thus, no sampling pulse is necessary and the beam positioning means 46' is connected for linear saw tooth deflection of the beam in selector tube 13' in the manner well known in the art. Thus, the modulated signal output of the beam switching tube 11, as provided by modulating source'18 and theexternal beam current regulator 17, is successively distributed to the desired plurality of output channels 15.

It is recognized from the foregoing description that improved and simplified distribution systems for modulated signals are provided in accordance with the teachings of this invention.

What is claimed is:

1. A modulated current distribution system comprising in combination, a multiposition beam switching tube having crossed electric and magnetic fields and structure adapted to selectively direct an electron beam to any one of its positions, electrodes in said beam tube defining a discharge path, a controllable electron discharge device having the discharge path thereof connected in series with said beam tube discharge path to control the beam current therethrough, modulating means controlling said discharge device to modulate said beam current in accordance with a desired pattern, and output electrodes in said beam tube having connections for distributing the modulated beam current to a plurality of channels, the electrodes of said beam tube including a plurality of substantially U shaped target electrodes, a plurality of substantially V shaped spade electrodes, and a cylindrical cathode, the spade electrodes concentrically surrounding the cathode with the open ends directed away from the cathode, the target electrodes concentrically surrounding the cathode with the open ends directed toward the cathode and overlapping the open ends of two adjacent spade electrodes, said electrode structure being compatible with a high degree of modulation of the beam unaccompanied by postional instability thereof.

2. A modulated current distribution system comprising in combination, a multiposition beam switching tube having crossed electric and magnetic fields and structure adapted to selectively direct an electron beam to any one of its positions, electrodes in said beam tube defining a discharge path, a controllable electron discharge device having the discharge path thereof connected in series with said beam tube discharge path to control the beam current therethrough, modulating means controlling said discharge device to modulate said beam current in accordance with a desired pattern, and output electrodes in said beam tube'having connections for distributing the modulated beam current to a plurality of channels, the electrodes" of said beam tube including a plurality of targetelectrodes surrounding the cathode, and an anode providing said electric field is positioned between said cathode and the target electrodes and apertured to permit beam current to fiow to the target electrodes.

3. A modulated current distribution system comprising in combination, a multiposition beam switching tube having crossed electric and magnetic fields and structure adapted to selectively direct an electron beam to any one of its positions, electrodes in said beam tube defining a discharge path, a controllable electron discharge device having the discharge path thereof connected in series with said beam tube discharge path to control the beam current therethrough, modulating means controlling said discharge device to modulate said beam current in accordance with a desired pattern and output electrodes in said :bear'n tube having connections for distributing the modulated beam current to a plurality of channels, the electrodes of said beam tube including a cathode, a plurality ofspade electrodes concentrically surrounding the cathode and. adapted to intercept a portion of the electron beam, the tube configuration being such that a decrease of spade potential causes the beam to change position,

4. The system defined in claim 3 and including a beam:

selector tube having a plurality of output electrodes and a cathode for providing an electron beam adapted to be.

swept over each of said output electrodes, each of said output electrodes of said beam selector tube being connected to a spade electrode of said beam switching tube.

References Cited in the file of this patent UNITED STATES PATENTS 2,116,671 Dowsett May 10, 1938' 2,296,050 Poch Sept. 15, 1942 2,303,924 Faudell Dec. 1, 1942 2,395,299 Skellett Feb. 19, 1946 2,536,150 Backmark et al. Jan. 2, 1951 2,540,646 Bernard Feb. 6, 1951 r 2,591,997 Backmark Apr. 8, 1952 2,617,964 Blayney Nov. 11, 1952 2,620,454 Skellett Dec. 2, 1952 2,706,248 Lindberg Apr. 12, 1955 2,733,409 Kuchinsky Jan. 31, 1956-

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