US2576948A

US2576948A - Deflection circuit

Info

Publication number: US2576948A
Application number: US583822A
Authority: US
Inventors: Roy Raymond B Le
Original assignee: Individual
Current assignee: Individual
Priority date: 1945-03-20
Filing date: 1945-03-20
Publication date: 1951-12-04
Anticipated expiration: 1968-12-04

Description

R. B. LE ROY DEFLECTION CIRCUIT 2 SHEETS-SHEET l Fil ed March 20, 1945 30 r ll 300 V. +450 V- TO COUNTER CENTERING VOLTAGE SOURCE SIGNAL BEING COUNTER FROM GWEEP CIRCUIT ADJUSTABLE STEP MARKER ,RAYMOND B. LEROY Dec. 4, 1951 R. B. LE ROY 2,576,943

DEFLECTION CIRCUIT Filed March 20, 1945 2 SHEETS-SHEET 2 GRID VOLTAGE OF TUBE IO I I l l I l VOLTAGE AT (B) TERMINALZ? l I l l I GRID VOLTAGE OF TUBE l2 CUT-OFF POTENTIAL OUTPUT VOLTAGE AT 380 VOLTS V LTAGE 1 AT POINT "Y"APPL|ED TO UPPER DEFLECTION ll" PLATE OF +v C.R.TUBE

CENTERING VO LTA 6 E Jrwwwbom- RAYMOND B. LEROY Patented Dec. 4, 1951 DEFLEC TION CIRCUIT Raymond-B. Le Roy, United States Navy Application March 20, 1945, Serial No. 583,822

(Granted under the act of March 3, 188%, as amended: April 30, 1928; 370 0.- G. 757) v 9 Claims.

This'invention relates to cathode ray' devices and is particularly concerned with a circuit for generating a voltage wave-form for use in defleeting the electron beam of a cathode ray tube to cause downward displacement of the timing axis'at a predetermined point in the horizontal sweep. One application of the invention is to provide'an adjustable step on the sweep trace of a cathode ray tube for accurate ran e measurement purposes, e. g., in radio-echo ranging and object-detecting apparatus.

It is an object of this'invention to provide improved step-generating means for causing downward deflection of the electron beam of a cathode ray tube at selected points in the horizontal sweepof said tube.

Another object of the invention is to provide a step generator of this class which is simple in operation, compact, and which includes a minimum of necessary circuitcomponents.

A further object of the invention is the provision of a gas-filled grid-controlled discharge tube circuit arrangement in which the firing of this tube can be adjusted within certain desired limits, and further employing an auxiliary electron discharge device which is arranged in such a manner as to extinguish the plat'e-current-fiow through the gas-filled discharge tube to allow its control grid'electrode to regaincontrol in readinessfor the next firing cycle ofits control voltage.

A'still further-object of the invention is topro-= vide an improved range step' generating circuit for generating an adjustable step marker which is movable along the timing sweep of a cathode ray tube to the position of an echo indication whose range is desired; the position of the rangestep being capable of adjustment along'th weep trace over a comparatively wide range.

According to the invention, a circuit arrangement is provided containing a pair of electron discharge devices .with their anode elements connected in parallel'with one another and to one of? the: vertical deflecting plates-of a cathode ray tube. the first electron discharge device being a gas-filled'tube of the type'including a" control grid, and-"the second. electron discharge device being a so-called hard tube or high vacuum tube which may be, for example, a relatively low impedance triode. The circuit is arranged in such a manner that the output of the gasfilled'tubesupplies the adjustable off-set or step to the sweep of the cathode ray tube-for producingthe desired downward displacement of the: timing axis, and the output of the hard tube or second: electron discharge device is used to control the extinction of the gasfilled tube. The control voltages supplied to the control grid of both electron discharge devices are alternating non-sinusoidal potentials of the same frequency and of the phase relationship hereinafter disclosed. In the preferred embodiment exponential or sawtooth control voltages are supplied to the control grid of" the gas-filled tube and square-wave control voltages are fed to the control grid of the hard tube. It is de sirable that these control voltages be fed to the respective control grids in such phase relationship that the positive increment of the control potential supplied to the grid of the gas-filled tube will occur simultaneously with the arrival of the negative increment'of the control potential fed to the grid of the hard tube whereby the latter is rendered conducting simultaneously with the arrival of the negative increment of the control potential at the grid of said gas-filled tube. The resistance of said hard tube during the conduction period is of such value as to present a low impedance electronic path the effect of which is to decrease the anode potential of said gas-filled tube to a value below the minimum voltage necessary to maintain said gasfilled tube conductive thereby to extinguish the plate current flow through the gas-filled tube and enable its grid to regain control in readiness for the next keying increment of the'control potential cyclically fed thereto. The sawtooth control voltage may be derived either from the same source of sweep voltage which is supplied to the horizontal deflection plates of the cathode ray tube to provide its timing axis or it may be generated'independently and synchronized with the horizontal sweep of the cathode ray tube. The quiescent potential of the hard tube is fixed by its circuit.

Other advantages and features of the inven tion will be apparent from the following particular description thereof made in connection with the accompanying drawing, in which Fig. l is a circuit diagram showing the preferred form of this invention;

Fig. 2 shows a set of explanatory curves to illustrate the operation of the circuit of Fig. 1, and

Fig. 3 is an end view of a cathode rayrange tube showing one form of indication obtained on its screen by the practice of the present invention.

Referring now to Fig. l, the circuit includes a pair of electronic paths or electron discharge tubes HI and It. The tube [0 is a gas-filled triode having a cathode M- of the indirectly heated type, a control grid 15 and a plate or anode Hi. The cathode I4 is positively biased in relation to the grid l5 by means of a resistor I! in shunt with a capacitor l8. The resistor l1! and the capacitor 18 form an RC peaking circuit to uphold the cathode bias during the interval that the plate voltage begins to decrease and the tube l0 commences to cutoff. Sawtooth control voltages, of the wave-form shown in curve A of Fig. 2, are supplied to the grid 55 of the tube In at the terminal 19 from a suitable source (not shown) which in one application of the device may be the saw-tooth output from the plate of the sweep. generator tube (not shown) of the sweep generator unit for the cathode ray tube employed for range determination in a radio-echo ranging and object-detecting apparatus.

Connected in parallel with the anode l6 of the gas-tube I0 is the plate or anode 20 of the tube l2, which is a low impedance triode having a cathode 2! of the indirectly heated type and a control grid 22. The cathode 2! is normally biased beyond cut-off by

resistors

23 and 24 which are of such values as to provide a bias slightly beyond plate-current cut-off for the tube [2 with low bleeder current. The resistors 25 and 26 form a voltage-divider connecting the anodes i6 and 20 to a source of high voltage (of the order of 450 volts), these resistors having such values as to provide satisfactory plate current through tube I0, and 380 volts on the plates l6 and 20 of the tubes I0 and I2 res ectively when both tubes are non-conducting. The voltage supply sources and the cathode heating supply are omitted for simplifying the circuit.

Square wave control potentials, as depicted by the waveform of curve B in Fig. 2, are fed to the grid 22 of the tube l2 at the terminal 21 from a suitable source (not shown) through the differentiating circuit composed of the capacitor 28 and the resistor 29. The resistor 29 and the capacitor 28 are of such values as to allow saturation plate current of the tube l2 for an interval of time long enough after completion of the sweep for the control grid voltage of the tube ill to drop below cutoff. The wave-form of the differentiated signal applied to the grid 22 of the tube I2 is shown in curve C" of Fig. 2. It is to be understood that the saw-tooth waves and the square-waves which control the operation of the tubes I0 and I2 are supplied to the respective grids of these tubes in such phase and so synchronized as to have the phase relationship substantially as shown by the curves A and"B respectively of Fig. 2.

In the plate circuit of tube [2 are the coupling capacitors 30 and 3i, a resistor 33, and the upper vertical deflection plate 34 of a cathode ray tube 35. Curve D of Fig. 2 is a graphic representation of the wave-form at point X of Fig. 1 and depicts the combined output from the plates I6 and 20 of the tubes I0 and I2, respectively. The resistor 33 and the capacitor 30 form a differentiating circuit for producing an exponential discharge curve on the trace of the cathode ray tube 35. The value of the capacitor 30 in conjunction with the resistor 33 determines the length of the exponential discharge curve (range step at point Y and shown by curve E in Fig. 2). The capacitor 30 may be, if desired, replaced by a parallel arrangement of capacitors with a suitable switching arrangement provided for selectively mally biased to beyond cutoff. When the grid voltage (algebraic difference of the cathode voltage and the saw-tooth control voltage) reaches the critical point, tube l0 conducts, the grid l5 at this time losing control of the tube. A steady plate-current flow through the tube [0 and the resistor 26 causes a steady potential at the plate N5 of the tube I0 which is lower by the IR drop across the resistor 26 than the potential at the beginning of the viewing cycle. This square waveform is applied to the upper vertical deflection plate 34 of the cathode ray tube 35 through the differentiating circuit composed of the capacitor 30 and the resistor 33, as above-mentioned, thereby producing an exponential discharge curve on the trace of the cathode ray tube.

It is necessary that some means must be provided to remove the plate voltage from the tube ID at the completion of the viewing cycle to allow the grid [5 of tube H] to regain control and be ready for the next firing cycle. As above-described, this function is performed by the tube l2 which is normally biased beyond cutoff by the

resistors

23 and 24. The grid 22 of tube I2 is coupled through the differentiating circuit composed of the capacitor 28 and the resistor 29 to the same source of negative souare wave voltage which blocks the sweep generator tube (not shown) emploved for the cathode ray tube 35. At the end of the part of the viewing cycle when sweep volta e is generated by the swee generator tube (not shown) and plate current is dra n by its plate, the grid [5 of the tube I0 is again very negative with respect to the cathode l4. At this instant, the following edge of the negative square wave ap lied to the grid [5 of the tube I0 is s inging positive, and the t be l2 conducts. Since the plates l6 and 20 of the tubes ID and I2 res ectively are connected together in parallel, the voltage on the plate 15 of the tube ID will decrease, this voltage decrease being more than s fiicient to extinguish plate current flow through the t be ID, allowing its grid l5 to re ain control. The arrangement of this circuit thus has the advanta e that the tube I2 is driven into conduction only a few microseconds to conserve power.

Control of the biasing potential of the cathode 14 may be obtained bv any desirable means such as, for example, by the voltage divider arrangement formed by a known form of selective resistor networks 40 and 4|, and the adjustable resistor 42. the movable slider 45 of the resistor 42 being preferably connected to the cathode lead 46 of the gas-filled tube l0. Suitable gearing 41 may be provided for operating the resistor slider 45, and range counter mechanism 48 may be included for range indication.

By controlling the bias the firing potential of the gas-filled tube l 0 may be caused to take place either at points a, b or c on the sawtooth wave A shown in Fig. 2 whereby the tube I 0 can be fired at a predetermined selected potential and thus the position of the output sweep displacement voltage or step along the timing axis may be adjusted as desired to produce downward displacement of the timing axis at the measuring point of an echo indication whose range is desired.

It is to be understood that positive sawtooth sweep voltages are applied to the right horizontal plate of the cathode ray tube 35 to produce the horizontal time axis. Negative video signals or marker voltages are applied to the lower vertical deflection plate of the cathode ray tube 35, causing upward displacement of the sweep. The negative step marker or displacement,voltage-from.

displacement of the-timing axis of 'the'cathode raytube. Additionally, it is to be understood that positive square waves from-a source (not shown) are applied to the control electrode (not shown) of thecathode ray tube 35 and serve to --unblank the indicating tube during the viewing or receiving period, as is a common practice in art.

While Ihave shown and described above apreferred embodiment of my invention, it is'to' be understood that various changes and modifications may be made therein without departing from the spirit of the invention andthe scope of the appended. claims.

.The invention herein described may b'e-m'anufactured and used by or for the Government of the UnitedStates of America for governmental purposes without. the payment of anyroyalties thereon or therefor.

WhatI claim is:

1. In combination, a pair of electron discharge devices each having an anode, a cathode and a control electrode, circuit means for connecting said anodesin parallel to a source of potentials and to an output circuit and for biasing. the oathodes so that said devices pass current in response to positive potential signals applied to the control electrodes thereof, a first source of alternat ing non-sinusoidal control voltages applied to the control electrode of one of said discharge devices for establishing anode-current flow duringpositive excursions thereof to initiate formation of a pulse signal in said output circuit, means for varying the cathode bias of said one discharge device for determining the time current flow is established, a second source of alternating nonsinuscidal control volta es 'of the frequency of said first source and 180 degrees out of phase therewith, and coupling means applying said second source to the other control electrode for renderin said second discharge-devices conduct ing substantially at the beginning'o'f'the positive excursion of said second control voltage to'provide a low impedance ath to groundfor said one discharge device to extinguish said'anode-curr'ent flow and'to'terminateformation of saidpulse signal.

2. In combination, a gaseous tube havingan anode, a cathode and acontrol electrode with the cathode thereof biased so that ionization ocours in response to positive potential 'signa'ls'applied to said controlelectrode; a high vacuum discharge device having ananode; a'cathode and a control electrode" with the cathode thereof biased .so that the device passes current in response to application of positive potential signals to the control electrode thereof, circuit means connecting the anode of said tube and the anode of saiddischarge device in'parallelto a source of potential and to arr-output circuit; a'first'sou'rce of -said discharge device for rendering said dis? charge device conducting substantially at thebeginning of the positive excursions of said secondcontrol voltage to provide a low impedance path to-ground. for said tube thereby extinguishing ionization thereof and terminating formation of;

said pulse signal.

- 3. Incombinationapair of electron discharge devices each having an anode, a cathode anda control electrode, circuit means for connecting said anodes in parallel to a source of potential and to an output circuit and for biasing the cathodessothat said devices pass current in response topositive potential signals applied to the control electrodes, a first source of alternating nonesinusoidal control voltages of saw-tooth waveform applied to the control electrode of one of said discharge devices for establishing anodecurrent iiow duringpositive excursions thereof to. initiate formation of apulsesignal in saidoutput circuit, bias control means for the cathodeot said. one discharge deviceoperable to determine the time. the anode-current flow is established, a second source of alternating non-sinusoidal control voltages of rectangular Waveform having aIfrequency of said first source and degrees outof phase therewith, and differentiating means applying said second source to the other control electrode'for rendering said second discharge device conducting substantially at the beginning of the .positiveexcursions of saidsecond control voltage to provide a low impedance path to groundfor said one discharge device thereby extinguishing. saidancde-current flow and. terminating formation of said pulse signal.

4... In combination, a gaseous tube having an anode, a cathode and a control electrode with the-cathode biased so that ionization occurs in response to positive potential signals applied to saidicontrolelectrode, a high vacuum discharge device having an anode, a cathode and a control electrode withthe cathode thereof biased so that the. device passes current in response to application of positive potential signals to the control electrode thereof, circuit means connect ing the anode of said tube and the anode of said discharge deviceinparallel to asource of potential and to an output circuit, a first source of alternating non-sinusoidal control voltages applied to the control electrode of said tube to'ionize said tube durin positive excursions thereof for initiating formation of a pulse signal in said output circuit, a second-source of alternating nonsinusoidal control voltages of the frequency of said firstsource and 180 degrees out of phase therewith, coupling means applying said second source to the control electrode of said discharge device for rendering said discharge device conducting substantially at the beginning of positive excursions of said second controlvoltage to provide a low impedance path to ground for said tube thereby extinguishing ionization of the gas and terminating formation of:-said .pulse signal,

andmeans connected in the cathode circuit of" said 'tubeioperative to hold the biason the oathode of said tube during the period immediately preceding extinction-of ionization to insure substantially sharp deionization of said tube.

5. In combination, a pair of electron dischargedevices each having an anode, a cathode and a control electrode, circuit means forconnecting said-anodesin parallel. to a source ofpotential;

andtoan output circuit and for biasing the cath odes solthat said devices pass current in; response tonpositivepotential signals applied to the control electrodes, a first source of alternating nonsinusoidal control voltages of saw-tooth waveform applied to the control electrode of one of said discharge devices for establishing anodecurrent flow during positive excursions thereof to initiate formation of a pulse signal in said output circuit, a second source of alternating nonsinusoidal control voltages of rectangular wavee form and of a frequency corresponding to the frequency of said first source and 180 degrees out of phase therewith, difierentiating means applying said second source to the other control electrode for rendering said second discharge device conducting substantially at the beginning of positive excursions of said second control voltage to provide a low impedance path to ground for said one discharge device thereby extinguishing said anode-current flow and terminating formation of said pulse signal, and means operative to selectively establish the cathode bias of said first discharge device for initiating formation of the output pulse at any predetermined point on the positively increasing portion of the saw-tooth waveform.

6. In combination, a gas-filled tube having an anode, a cathode and a grid; a high vacuum tube of relatively low impedance having an anode, a cathode and a grid, the anodes of both of said tubes being connected in parallel; a cathode ray tube having horizontal and vertical deflection plates, and means for controlling said gas tube for producing a step-forming voltage which is applied to one of said deflection plates; the lastnamed means including means comprising alternating non-sinusoidal control voltages of different wave-forms applied to the respective grids of both tubes, said control voltages being supplied in such phase relationship so that the positive increment of the control potential fed to the grid of said gas-filled tube occurs simultaneously with the arrival of the negative increment of the control potential fed to the grid of said high vacuum tube whereby conduction thereof occurs simultaneously with the arrival of the negative increment of the control potential at the grid of the gas-filled tube, the resistance of said high vacuum tube during its conduction period being of such value as to present a low impedance electronic path effective to decrease the anode potential of said gas-filled tube to a value below the minimum voltage necessary to maintain said gas filled tube conductive thereby to extinguish platecurrent flow through the latter and enable its grid to regain control in readiness for the next control potential cylically fed thereto; and means operative to provide an adjustable bias on the cathode of said gas-filled tube for varying the point at which firing thereof occurs thereby to enable the position of said step-forming voltage output from said gas-filled tube to be varied as desired along the timing axis of said cathode ray tube.

v '7. In an indicating system, a cathode ray tube having a pair of deflecting means, a sweep circuit operative in accordance with control voltages of rectangular waveform tofeed sweep potentials of saw-tooth waveform having the frequency of said control voltages and 180 degrees out of phase therewith to one pair ofsaid deflecting means, a pair of electron discharge devices each having an anode, a cathode and a control electrode, circuit means for connecting said'anodes in parallel to asource of potential and to the other pair of said deflecting means and for biasing said oath-3' odes'so that said devices pass current in response to positive potentials applied to said control elec-' trodes, means applying said sweep potentials to one of said eontrol electrodes to render one of said devices conducting at a particular voltage point of said saw-tooth waveforms determined by the cathode bias of said one device, and a differentiating circuit for applying said control voltages of rectangular waveform to the other control electrode for rendering the other discharge device conducting at the beginning of positive excursions of said rectangular waveforms to provide a low impedance path to ground for said one discharge device to thereby extinguish conduction thereof.

8. In an indicating system, a cathode ray tube having a pair of deflecting means, a sweep circuit operative in accordance with control voltages of rectangular waveform to feed sweep potentials of saw-tooth waveform having a frequency corresponding to the frequency of said control voltages and degrees out of phase therewith to one pair of said deflecting means, a pair of electron discharge devices each having an anode, a cathode and a control electrode, circuit means for connecting said anodes in parallel to the other pair of said deflecting means and for biasing said cathodes so that said devices pass current in response to positive potentials applied to said control electrodes, coupling means applying said sweep potentials to one of said control electrodes to render one of said devices conducting at a particular voltage point of said saw-tooth waveforms determined by the cathode bias of said one device, a differentiating circuit for applying said control voltages to the other control electrode for rendering the other discharge device conducting at the beginning of positive excursion of said rectangular waveforms to provide a low impedance path to ground for said one discharge device to thereby extinguish conduction thereof, and means operable to selectively vary the oath-- ode bias on said one discharge device for establishing conduction thereof at predetermined voltage points on the saw-tooth waveforms.

9. In an indicating system, a cathode ray tube having two pairs of deflection plates, a control voltage of rectangular waveform, saw-tooth sweep circuit operative responsively to said control voltage of rectangular waveform and connected to one pair of said deflection plates, a gaseous discharge tube having an anode, a cathode-and a control electrode with the cathode so biased that ionization occurs in res onse to positive potential signals applied to said control elec-' trode, a hi h vacuum discharge tube having an anode, a cathode and a control electrode with the cathode thereof biased so that the tube passes current in response to the application of positive potential signals to the control electrode thereof, the anode ofsaid gaseous tube being connected to the anode of said vacuum tube, resistance means connecting said anodes to a source of potential, a differentiating circuit connecting said anodes'to a plate of the other pair of said deflecting plates, means connecting said sweep circuit to the control electrode of said gaseous tube to render said tube conducting at a particular voltage point of the saw-tooth waveform determined by the cathode bias of said vacuum tube, and coupling means applying said control voltage of rectangular waveform to the control electrode of said vacuum tube for rendering said vacuum tube conducting at the beginning of positive excurlsions of said rectangular waveform to provide a low impedance path to ground for said gaseous Number tube to thereby extinguish conduction thereof. 2,286,894 RAYMOND B. LE ROY. 2,301,196 2,350,069 REFERENCES CITED 5 23503333 The following references are of record in the 2,412,210 file of this patent: 2,428,149

UNITED STATES PATENTS Number Name Date 10 2,147,472 Ulrey Feb. 14, 1939 2,280,949 Hall Apr. 28, 1942 10 Name Date Browne et a1 June 16, 1942 Bradford Nov. 10, 1942 Schrader et a1. May 30, 1944 Hall June 6, 1944 Edson et a1 Dec. 10, 1946 Falk Sept. 30, 1947 OTHER REFERENCES Electronics, January 1942, Des. 34, 35, Photofiash Synchronizer Tester, by Marsal.