US2234830A - Cathode ray modulator - Google Patents

Description

March l1, 1941. L. E. NORTON cATHoDE RAY MODULATOR 2 Sheets-Sheet l Filed May 28, 1938 :S'nnentor March 11, 1941. L. E. NORTON 2,234,830

CATHODE RAY MODULATOR Filed May 28, 1938 2 sheets-sheet 2 4 :Snuentor Gtorneg Patented Mar. 11, 1941 UNITED STATES ATENT OFFICE Radio Corporation of Delaware America, a. corporation of Application May 28, 1938, Serial No. 210,574`

9 Claims.

My invention relates to cathode ray modulators and more specifically to a method of and apparatus for simultaneously applying modulating potentials to grid, cathode and anode electrodes of a cathode ray tube.

The cathode ray in a cathode ray tube is generally deflected by deflecting coils or electrodes, focused by applyingbias voltages to one or more anode electrodes and modulated or varied in intensity by applying modulating voltages between grid and cathode electrodes. If modulation voltages of improperly related amplitudes are applied to the anode electrodes, defocusing usually accompanies the modulation, and thereby an unsatisfactory trace results. I have found that'if the potentials applied to the first and second anodes are suitably varied, a properly focused modulated trace may be secured.

If the best focus is obtained by a given ratio of voltages applied between rst anode and cathode, and between second anode and cathode, anode modulation potentials may be applied in substantially the same ratio. Therefore an obj ect of my invention is to provide means for applying modulation voltages. to the anodes of a cathode ray tube in the ratio which results in* maintenance of proper focus. Another object is to provide means whereby modulation voltages may be applied to anode, cathode and control electrodes of a cathode ray tube. An additional object is to provide means whereby a fixed and a variable pattern may be obtained on a cathode ray screen.

In describing the invention reference will be made to the accompanying drawings in which Figure 1 is a schematic diagram of one application of the invention;

Figures Zand 3 are illustrative cathode ray traces; 4

Figure 4 is a circuit diagram of a preferred embodiment of the invention; and

Figure 5 is a circuitdiagram of a modiiication of the invention.

Although my invention is not limited to any particular form of modulation, for purposes of illustration, a vcomplete schematic diagram of a cathode ray modulation circuit is shown in Fig. 1 'I'his circuitwhich is partly of the type shown in U. S. Patent No. 2,121,359 issued June 21, 1938, on an application Serial No. 134,074, filed on March 31, 1937, by David G. C. Luck and Lowell E. Norton, shows a cathode ray tube on which a marking scale and impulse of a phase to be determined by reference to the scale are impressed on the cathode ray tube in accordance with my invention. A standard frequency generator I provides (Cl. Z50-27) a-source of alternating current of a frequency of 15 kilocycles per second.` This alternating current is impressed on three frequency divider stages 3, 5, 'I which provide alternating currents of the following frequencies: 3000 C. P. S., 1000 C. P. S. and 3331A; C. P.' S. `The output of the last frequency divider 'stage 'l is applied to a multivibrator 9, having a ratio of 8 to 1. The fiat top wave I I produced by the multivibrator is applied to a filter and wave Shaper I3 to produce a sine wave I5, which is applied to a phase splitter I1. The output of the phase splitter is a two phase current I9 which is impressed on the defiecting coils 2l of the cathode ray tube 23.

The output of the several `frequency divider stages 3, 5, 'I are applied to attenuators 25, 21, 29 and from the attenuator to an'amplifer 3|. The output of the amplifier 3| is impressed between the grid 33 and cathode 35 electrodes of the cathode ray tube, and upon a modulator 31. The .20 modulator and cathode ray tuberare supplied with power from a common source 39; The-first 4I and second 43 anode electrodes of the cathode ray tube are connected to a voltage divider which, in turn, is connected to the modulator tube so thatits potential variations follow those ofthe modulator. The signal of unknown frequency, phase, or the like, from a source 45 Amay be impressed through an impulse amplifier 46 onv either the amplifier or the modulator. v30

'Ihe details of a preferred embodiment of amplier, modulator and cathode ray tube circuit are illustrated in Fig. 4. The terminals A-B are connected to the input of a thermionic amplier T. The amplier T may also include an input terminal Y which is connected to a grid Gy. The amplifier output circuit includes a potentiometer R4 and a source of current 5I. The outputcircuit is coupled through a capacitor C to the control electrode G of the cathode ray tube. The cathode electrode K is connected to ground terminal B by a self-bias resistor R3. Therst and second anode electrodes A1,` Az are connected to the cathode K by a resistor R2 which includes an adjustable tap 53. A capacitor 55 may be shunted across either the upper or lower portion of the resistor R2 to maintain their impedance ratio independent of frequency. The anode A2 is connected through a resistor R to an anode Voltage source 51.

A modulator tube T2 is connected as follows: The cathode K1 is connected through a self bias resistor R1 to ground. The first grid G1 is connected to the output of the amplier T by a connection between the capacitor C and the grid G. 55

The anode P is connected to the junction of the resistor R and the second anode A2. The second grid'G2 is connected to a bleeder network 59, 6| which shunts the anode voltage source 51. The third grid Ge is connected to ground through a resistor 63. The source of potential of unknown frequency, or phase or desired modulation may b e connected to the terminal Y and grid Gy in the amplifier T, or the third grid G3 of the modulator T2.

The adjustment and operation are as follows: 'I'he currents in the deiiecting coils are adjusted to produce a circular pattern which maybe adjusted in intensity by R3 so that the circular trace v 61 appears as in Fig. 2 or disappears as in Fig. 3. The cathode ray beam focus is adjusted by varying the tap 53 on resistor R2. The modulator T2 is adjusted to approximately 'cut-off its anode current by regulating the self bias R1. The xed scale or markers 69 are obtained by applying negative impulse potentials, from the attenuators 25, 21, 29 to the grid of the amplifier T. The negativeimpulservoltages applied to the grid appear as positive impulse voltages on the output resistor R4. These positive impulse voltages are simultaneouslyapplied to the grid G of the cathode ray tube and the grid G1 of the modulator tubeTz. ,y Y

The simultaneous .application of the positive impulse voltages to Ythe grids G and G1 increases the brightnessrof the cathode ray traces (Figs. 2 and 3)' during the application of the impulse. Since theV positive Vimpulse voltage on G1 makes the modulator T2 more conductive, this increases the voltage drop in the resistor R, and diminishes the potentials applied lto the rst and second anodes A1! A2 nwhich thereby deflect the trace outwardly Yduring the impulse. While the lpotentials applied to the anodes A1 A2 vary as described, the ratio of the potentialsr being applied between K and A1, and between K and A2 through the' potentiometer R2 remains fixed and thereby the focus' is maintained. Thus, a fixed pattern or traceis'obtained. The unknown modulation impulse may be applied to the grid G2 of the modulator T2V and will be observed as a trace 1i whose position indicates its phasevwith respect to the vxed scale.v The several traces may be extended from the circular trace toward the center instead o f away from the center by applying positive instead of negative impulse voltages, or may be, extended fon both sides of the circular trace by application of negative and positive impulses. Y

Thus a cathode ray modulatorl including a modulator tube connected in shunt to a potentiometer,`from v`which'modulation voltages are applied to the first andsecond anodes of the cathode ray tubehas been described. Iny some installations it may be desirable to apply the modulation potentials byV including the modulator tube in seriesuwith the cathode-circuit of the cathode ray tube as shown in Fig. 5. In the modiiied circuit, ,the tube V is arranged as an oscillator, which is modulated by impressing the modulation potentialsacross the terminals AB.` The output circuit 13 of theoscillator is coupled to a rectiiier V2.` 'I'he rectie output is applied to the cathode K2 and control electrode G4 of the cathode-anode circuit of the modulator tube V3 is connected in series with the self bias resistor R5 of the cathode ray tube.

The anode potential for the cathode ray tube and the modul-ator Vs is supplied from any suitable source 15. The first G5 and second Gs anode electrodes are connected to the slider and upper terminal of a potentiometer 11, which is connected from the cathode K2 to the positive terminal of the source 15. Either the upper or lower portion of the'potentiometer may be shunted by a capacitor 1S to maintain the proper ratio of impedances independent of frequency. After the slider of the potentiometer 11 has been adjusted to properly focus the cathode ray, the focus will be maintained because the modulation potential applied through the modulator tube will not alter the ratio.

In the instant circuit the modulating potentials are simultaneously applied to the control grid and rst and second anode electrodes of the cathode ray tube. The operation of the modulator is essentially the same as the modulator circuit of Fig. 4. In the instant circuit the modulation potentials of either Ythe iixedpattern or the ixed pattern and the variable or unknown pattern are applied to the modulator V3 and to the oscillator and, after rectification, are applied to the control grid G4 and the cathode electrode K2. The modulator Vs, being serially connected and suitably biased, Varies the potential between K2 and G5, and between K2 and Gs, of the cathode ray tube to thereby vary its trace. Thus I have described a cathode ray tube modulation system in which the cathode ray beam is modulated without deiocusing. The focus is adjusted and maintained by applying potentials in the proper ratio to the rst and second'anodes. While twophase currents have been applied to deflect the beam in a circular trace, currents of saw-tooth or any suitable wave form may be applied to deflect the beam in'any desired pattern.

I claim as my invention:

1. In a cathode ray tube modulation device,

a cathode ray tubeincludin'g cathode and iirst 'and second anode electrodes, means for applying steady potentials to said rst'and second anode electrodes, meansfor varying the ratio of said potentials to focus said ray, and means for applying modulation potentials to said anode electrodes and maintaining constant the ratio of the cathode to the rst anode potential to the cathode to the Vsecond anode potential during the said applications of saidA modulation vpotentials. 2. In a cathode ray tube modulation device, a cathode ray tube including cathode, control and rst and second anode electrodes, means for applying steady potentials to said first and second anode electrodes, means for varying the ratio of said potentials to focus said ray, meansfor applying modulation potentials to said control electrode, and means for applying modulation potentials to said anode electrodes andmaintaining constant the ratio of the cathode to the rst anode potential to the cathode to the second anode potential during the said applications of said modulation potentials.

3. In a cathode ray tube modulation device', a cathode ray tube including cathode, control and rst and second anode electrodes, Ameans for applying steady potentials to said rst and second anode electrodes, means for varying the ratio of said potentials to focus said ray, and means for simultaneously applying modulation potentials to said control and first and second anode electrodes and maintaining constant the ratio of the cathode to the control electrode potential to the cathode to rst anode potential `and the ratio of the cathode to rst anode Vpotential to the cathode to second anode potential during the said application of modulation potentials,

4. In a cathode ray tube modulation system, a cathode ray tube including control grid and first and second anode electrodes, a first source of modulation potentials, means for simultaneously applying potentials from said first source to said control grid and first yand second anode electrodes, a second source of potentials, means for simultaneously applying potentials from said second source to said electrodes, and means for maintaining a constant ratio of resultant potentials applied to said first and second anode electrodes so that focuses of the resultant cathode ray traces are maintained over a range of said applied potentials.

5. In a cathode ray tube modulation system, a cathode ray tube including control grid, first and second anode electrodes, an amplifier, a vacuum tube having an input and an output, connections from the output of said amplierto said control grid and to the input of said vacuum tube, connections from the output of said vacuum tube to said first and second anode electrodes, means for adjusting and maintaining a ratio of potentials for focusing said cathode ray, means for applying said potentials to said first and second anode electrodes insuring focusing of said cathode ray, and means for applying modulation potentials through said amplifier and said Vacuum tube connections to said cathode ray tube electrodes.

6. In a cathode ray tube modulation system a cathode ray tube including control grid, rst and second anode electrodes, an oscillator, a rectifier, a thermionic tube having an input and an output, connections from the output of sai-d oscillator to said rectier and to the input ofV said thermionic tube, means for effectively connecting the output of said thermionic tube in the anode current paths of said cathode ray tube, means for applying and maintaining potentials of a known ratio to said rst and second anodes insuring focusing of said cathode ray, and means for applying modulation potentials to said oscillator and said thermionic tube so that said cathode ray is modulated.

7. The method of modulating a cathode ray tube having first and second anode electrodes which includes the steps of establishing a cathode ray beam in said tube, focusing said beam by adjusting the ratio o-f steady potentials applied to said first and second anodes, modulating said beam by varying potentials by applying said varying potentials to said anode electrodes and at the same time maintaining constant the ratio of the varying potential applied to the first anode to the Varying potential applied to the second to the rst anode to the Varying potential applied to the second anode,and applying a modulation potential to said control electrode.

9. The method of modulating a cathode ray tube having control, rst and second anode electrodes which includes the steps of establishing a cathode ray beam in said tube, focusing said beam by adjusting the ratio of steady potentials applied to said first and second anodes, modulating said beam by varying potentials by applying said varying potentials to said control electrode and to said anode electrodes and at the same time maintaining constant the ratio of the varying potential applied to the first anode to the varying potential applied to the second anode and maintaining constant the ratio of the varying potential applied to the first anode to the varying potential applied to the control electrode.

LOWELL E. NORTON.

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