US2587734A - Modulator tube and circuits - Google Patents

Description

March 4, 1952 v, KALFMAN 2,587,734

MODULATOR TUBE AND CIRCUIT Filed Dec. 22. 1947 MODULAT. L AND OSCILLATOR CARRIER ,,/z

WAVE f T VIDEO 5/GNAL c axis I INVEIYTOR.

Patented Mar. 4, 1952 UNITED STATES ATENT FFISCZE The present invention relates to modulator tubes, and more particularly to cathode beam the path of a cathode ray beam to serve as effective electrical wave controllers for these and ,lgindred purposes.

In the general mode of time division transmission, the carrier wave is interrupted at a high fre uency rate. With such abrupt interruption .of the carrier, the sidebands usually expand be yond the assigned limits, However, it'is found that, the output products of the modulated carrier wave can be restricted to particular frequency regions by controlling the waveshape of the time divisions of the carrier wave. One instance of modulation by this'method is given by F. Gray in his Patent 2,257,795, October '7, 1941..

Where these spectral limitations are observed, it is basic that, the waveshape of the interruption be that of the curve of a cosine function, which rises and falls from substantially a zero level in a definite time interval. To illustrate this state more clearly, reference is made to the periodic envelopes at C, in Fig. 1, wherein, the peak magnitude of each envelope corresponds to a statistical magnitude of the intelligence wave 3. However, in order to produce these envelopes free of the varying changes of the wave 3, this wave is first sampled in steady state electrical quantities, as shown at B, which in turn modulate the envelopes at C. The areas a indicate the wave shape relations of the envelopes at C with respect to the simple case of unity modulation at A. 'In order to convey the maximum amount of information allowed per given time, it is desired that the periods b at C be filled in. However, in either case, the carrier envelopes must be first produced in periodic envelopes, as at C, in tWO separate channels in alternate sequence, and the outputs of the two branches combined for continuous operation. Such operation requires ating means, so that the carrier is not interfered with during the sampling periods b. However, gating means in the prior art do not possess ideal characteristics for this purpose, as the "waveshape must be accurately predetermined. Accordingly, I provide targets of novel design, which may serve as combined gate and wave shapers, or modulators --in general.

In the drawings:

Fig. 1 shows a partly diagrammatic modulator :tube of the cathode beam type, and schematic circuit ar an em o prod cing waveszo mpants in accordance with the invention, and A, B and C are waves involved in it.

Figures 2, 2b and 2c are various shapes of target structures in the cathode ray modulator tube.

In Figure 1, the modulator tube comprises a vacuum envelope l8, heater element 2?, cathode element 28 an electron intensity control grid 29. focusing gun 30, electrostatic deflecting plates 22 and 25 a cathode beam IT, a preshaped wave ccontrol target 23, and secondarily emitted electron collector anode 3|, The tube I8 may be fashioned in general, as of various conventional types. such employing a suitable type of gun structure for electrostatic focusing, magnetic focusing, magnetic deflection, and multiple stages o elect on acc le ting a o et ls of various shapes of the target 23 anodes are shown in Figures 2, 2a, 2b and 21;, with their active faces parallel to the plane of the paper, and the electron beam I1 is indicated in its position of normal flow.

In Figure 2, the target electrode is divided into two sections 'a and b. The section 1) consists of a uniform conductive surface in the plane perpendicular to the flow of the beam 11, with a central conductive strip 32, which extends to the l ft and su -d ides th .s t q 'ah 1 ,ductiye section b, at terminal ct, is electrically conn c ed o a termi a Such a o ha Sh i electrical path to the emitting cathode. Both subedivisions of the section a consist of a plurality of conductive strips 33 parallel to andlextending outwardly from said central extension tri s/' o he e t on b, and a t ed u that, thesurtace of each elemental strip perpendicular to the axisof the electron beam 11. The orientation of the target is also such that, the elemental strips 33 are parallel to the .direction in which the beam vll is to be deflecte d by a wa e 34 e ua to hal t fr q en o the s pcarrier wave 2. Sub-carrier wave is referred to a Wave h v n a qu cy fm at which he carrier wave is time divided. The elementalstrips 33in hothnsub-divisions of section a are made to have mutual conductance of some predetermined value by resistance element 35 such that-between the .two outgoing terminals y and y" and the central termina at the va iat on of co d t nc is linear.

,Malging reference to the wave-control action.

of the tar e ele ode sh w n F g- 2 th lectron beam IT is deflected horizontally by a gate cont o were .34 havin a r quen y 13 /2, so that the beam raises a e se i qn a l ri g o lf va ied 9 the wa 9 35 and e qisci o i nb du nsthe next helisrgleperiq f h a w As mentioned previously, the section b has direct electrical path to the emitting cathode, hence, the horizontal shift of the beam at the normal central position maintains ideally zero signal at the, output terminals y and y'-.

The elemental conductive strips 33 in Figure 2, section a, may be constructed in diilerent ways with the same results obtained as given above. For example, the mutual conductance of the elemental strips may be made reactive, instead of resistive. This is shown in Figure 2b. The elemental strips 33 are made of metallic sheets stacked up alternatively with dielectric material 42. The size of the metallic sheets 33, the spacing between each elemental sheet 33, and the dielectric material 42 may be chosen to obtain a desired capacity between the outgoing terminals y and 11 which are connected to the inductance 19 as shown in Fig. 1.

The targets shown in Figures 2 and 2b are designed for balanced output operation; however, they may also be used for single ended operation, and as shown in Fig. 2c. The elemental strips 33 may be devised either with capacitive or resistive mutual conductance. The extreme lower end strip in section a is electrically connected to the conductive section b, and the outgoing terminals are taken from the extreme upper end strip of section a and the conductor of section b, which is the grounded terminal. The switching wave 34 is applied to the electrostatic deflecting plates to sweep the beam [1 in a direction parallel to the elemental strips 33. The sub-carrier wave 2 is applied to the electrostatic deflecting plates to sweep the beam H in a direction right angle to the elemental strips 33, and the magnitude of the sub-carrier wave 2 is adjusted so that, at the lower slope of the said wave the beam l7 reaches to a point where the elemental impedance in section a with respect to the section b is zero. The carrier wave is then modulated by the intelligence D. C. components, such as shown at B in Figure 1, and applied to the intensity control grid 29 for the production of the desired waves at the outgoing terminals.

} Having described my invention I wish it to be understood that I do not desire to be limited to the details as shown and described, as various modifications coming within the scope of the appended claims will suggest themselves to a person skilled in the art.

I claim:

1. In modulator tubes of the cathode beam type where the output of the beam current is controlled by a target in the path of the beam, a target which comprises first and second parts: the first part comprising electron responsive uniform surface and connecting means therefor to return substantially all of the incident beamcurrent to the original electron source; the second part comprising a plurality of beam responsive parallel strips adjacent to the first part and said strips having mutual impedances in incremental steps of predetermined values with respect to the said first part, in a sense that, the second part presents to the beam an effective impedance which at any one position in a dimension at right angle to the said parallel strips is a function of the displacement of the beam from a normal position, and at saidnormal position the impedance is substantially zero to the first part.

2. In combination, a modulator tube comprising beam forming electrodes, a target in the path of the beam, said target comprising first and second parts: the first part comprising an electron responsi v'e uniform surface and connecting means therefor to return substantially all of the incident beam current to the original electron source, the second part comprising a plurality of beam responsive parallel strips adjacent to the first part and said strips having mutual impedances of predetermined values and structural arrangement therefor to electrically connect one elemental member of the said strips to the first part, whereby the second part presents to the beam an effective impedance which at any one position in a dimension at right angle to the said parallel strips is a function of the displacement of the beam from zero impedance at normal incidence upon the said elemental member, means to sweep the beam to and fro upon the first and second parts in a dimension parallel to the said strips at a switching frequency fm/2, means to simultaneously sweep the beam in a dimension perpendicular to the said strips at a frequency jm or multiple thereof, in a sense that, the switching point of the beam occurs substantially at incidence upon the said elemental member, whereby the beam current fiows through incrementally changing divisions of the total impedance of the said second part, and said changing divisions are periodic functions of the wave im.

3. As set forth in claim 2, which includes in combination, means to vary the strength of the said beam incident upon the said target at a carrier frequency, whereby said carrier is modulated by the said functions while being swept across the said second part and being suppressed during the sweeping across the said first part of the target.

4. As set forth in claim 2, which includes in combination means to vary the strength of the said beam incident upon the said target by intelllgence waves, whereby the said periodic functions are produced in various peak magnitudes corresponding to statistical levels of the said waves.

MEGUER V. KALFAIAN.

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

UNITED STATES PATENTS Number Name Date 913,521 Latour Feb. 23, 1909 1,613,626 Von der Biji Jan. 11, 1927 1,976,400 Illberg Oct. 9, 1934 2,013,162 McCreary Sept. 3, 1935 2,024,979 Metcalf Dec. 17, 1935 2,144,337 Koch Jan. 17, 1939 2,193,539 Shelby Mar. 12, 1940 2,213,938 Bennett Sept. 3, 1940 2,220,165 Malter Nov. 5, 1940 2,224,677 Hanscom Dec. 10, 1940 2,257,795 Gray Oct. 7, 1941 2,262,764 Hull Nov. 18, 1941 2,368,328 Rosencrans Jan. 30, 1945 2,395,467 Deloraine Feb. 26, 1946 2,427,500 Houghton Sept. 16, 1947 2,429,631 Labin Oct. 28, 1947 2,459,724 Selgin Jan. 18, 1949 2,522,291 Marrison Sept. 12, 1950 FOREIGN PATENTS Number Country Date 505,653 Great Britain May 11, 1939 OTHER REFERENCES Therman, Radio Engineers Handbook, 1943 ed. Published by McGraw-Hill Co., N. Y.

Images