US2340594A

US2340594A - Electron discharge device

Info

Publication number: US2340594A
Application number: US407738A
Authority: US
Inventors: Jonker Johan Lodewijk Hendrik
Original assignee: Individual
Current assignee: Individual
Priority date: 1939-05-22
Filing date: 1941-08-21
Publication date: 1944-02-01
Anticipated expiration: 1961-02-01

Description

Feb. 1, 1944. .1. 1.. H. JONKER 2,349,594v

ELECTRON DISCHARGE DEVICE Filed'gu 21, 1941 i 1 v IQ INVENTOR JkazvlHe/bnlia Patented Feb. 1, 1944 ELECTRON DISCHARGE DEVICE Johan Lodewijk Hendrik Jonker, Eindhoven,

Netherlands; vested in the Alien Property Custodian Application August 21, 1941, Serial No. 407,738 In the Netherlands May 22, 1939* 4 Claims.

This invention relates to an electron discharge device of the variable mu type in which the mutual conductance may be varied or controlled in response to control voltages, such as those used in automatic volume control.

The so-called variable mu tubes usually comprise one or more grids having a variable pitch or two or more grids between which the distance is unequal at various points along the grids so as to ensure a gradual decrease in mutual conductance with increasing negative bias or grid voltage with reference to the cathode. The anode-current grid-voltage characteristic of a variable mu tube may be imagined to be made up of the individual characteristics of small parts or portions of the grid. For instance, in a variable mu tube having a grid with apertures of various sizes the smallest apertures through which consequently a camparatively small electronic stream passes will impart to the tube a characteristic having a steep slope, and to this small stream is then added the much larger electronic stream passing through the large apertures, which impart to the tube a characteristic having much less slope. This tube characteristic may be imagined to be the resultant or sum of these characteristics for each individual aperture, and is of gradually decreasing slope. At minimum grid bias the discharge passes through all of the apertures, the mutual conductance characteristic is predominantly that due to the smaller apertures, and therefore its slope is steep and the anode current is a maximum. As the grid bias increases and the grid becomes more negative, the discharge through the smaller apertures stops, the mutual conductance is determined principally by the larger apertures and therefore its slope is less, and the anode current decreases. It has been found difiicult to construct such tubes which have a very steep slope of the anode current grid voltage characteristic without at the same time having an undesirably large anode current at minimum grid bias where the slope is very steep. If the distance between two grids through which the discharge passes in succession is not equal throughout the length of the grids, the characteristics for different points along a grid will have different slopes, so that electric discharge tubes having grids between which the distance varies along the grids will also have a grid voltage-anode current characteristic whose slope will gradually decrease.

It has been customary to operate a variable mu tubeat different points along this characteristic bvva y ng the ri b as. L ns i ep he d aw back that upon adjusting the grid bias to operate the tube where the characteristic has very steep slope the anode-current is much higher than necessary for attaining this slope.

The principal object of the invention is to provide a device having a mutual conductance which can be readily controlled or regulated so as to vary between high mutual conductance and low mutual conductance without changes in the bias of the control grid, and preferably with a very continuous and uniform variation in mutual conductance.

According to the invention the difierent characteristics imparted to the tube by the different portions of the grid are in effect used individually and practically unaffected by other portions of the grid. Preferably the device is so made that there can be obtained a very continuous transition from one of these characteristics to another, such as from high mu to low mu. To this end the electron discharge is concentrated into one or more electron beams shifted along a signal grid of the variable mu typelby beam control or deflecting members. Preferably two or more grid-shaped electrodes are placed in the path of the beam so as to'be passed successively by the beam, one of the grids being sufilciently irregular with reference to the othertube elements, as, for example, by being inclined to the other grid to cause the mutual conductance of the tube to vary along the grids in a direction in which the electron beam can be deflected. This construction in which the distance between the signal gridplane and another grid-plane varies along the grids is a simple way of obtaining an uneven potential in a grid-plane through which the beam pass By varying the difference of potential between deflecting members on opposite sides of the electron beam path the beam can be" directed and the discharge practically confined to difierent sections of the grid which impart difie'rent grid voltage-anode current characteristics to the tube. If the spaced grid conductors extend parallel with the direction in which the electron beam can be deflected, the transition between the different characteristics will be very gradual and will not change abrupty, as might occurat'eachaperture if the grid conductors were spaced non uniformly and extended transversely of the direction ofdeflection of the electron beam. Thus, according to the invention, a great variation in the slope of the grid voltage-anode current characteristic is obtainable without the attainrepresents schematically one embodiment ofth'e invention.

The particular embodiment of the device shown in the accompanying drawingcomprises an electron discharge tube having an evacuated'enve;

lope l enclosing electrode elements arranged to constitute a variable mu or variable amplification factor tube having an anode or output electrode 2 and a source of electrons for directing an electron beam to the anode, such as an indirectly heated cathode 3 and a beam forming electrode, such as a cylinder 4' coaxial with the cathode and having a slot or opening in one side. The electrons emitted by the cathode are formed into an electron beam 5 which, in the particular con-' struction shown in the drawing, is a flat-sided or'ribbon-like beam substantially rectilinear in cross-section and directed to' the anode 2; In-

terposed between the anode and the'source of electrons is a grid electrode'fi' which comprises a rectangular frame and a plurality of spaced parallel conductors 1 extending lengthwise of the frame and may be used as a control grid.

Preferably a second similar grid electrode 8' is interposed between the control grid 6 and the anode 2, and is connected to act" as a screen grid. The control grid 6 is so related to theother elements of the tube, preferably by being inclined to the anode, so that one end is nearer the anode than the other, as indicatedin the drawing, that the grid electrodes 6' and 8 constitute a grid structure which is sufiiciently irregular with ref.- erence to the other elements of the tube to give the tube a difierent mutual conductance or amplification factor at difierent positions of the beam 5 along the conductors of the grid 6; In the particular construction shown the upper end of inclined grid 6 is nearer the anode, and grid 8 is parallel to the anode. at the position A near the upper end' of'the grid 6, the mutual conductance or amplification factor is high and the tube acts as a' high mu tube, and when the beam is near the-other end. of the grid at position B, the amplification factor is low and the tube acts a low mu tube. By shifting the beam 5'along the grid 6 lengthwise of the grid conductors l, a very regular and continuous change in mutual conductance from high mu to lowmu can be obtained. r

The tube may be regulated to operate at will with any selectedamplification iactor within-the range of the tubeby control means for deflecting the beam lengthwise of the conductors I of the grid 6, such as deflection plates Sand lii-positioned between the electron source and-thegrid 6 on opposite sides ofthe' path ofthe" beam to provide a passage for the beam. Theposition of the-beam-on the grid 6'will depend upon the diflerence of potential between the deflection plates-'9 and I0, and by varying the potential of the plate ill, for example, th -beam can bade- When the beam'is flected and held at any selected point on the rid 6.

For clearness of illustration, the tube is shown as of the elongated type, but obviously the tube can be made of cylindrical construction and the beam 5 instead of being a. flat ribbon-like beam can be a circular disc beam such as may be obtained by known constructions as, for example, U. S. Patent to Hamacher, 2,090,001. In this case the two grids and the anode are obviously in the form of rings or cylinders to correspond to the shape. ofthe circular disc beam.

The variation in potential on the deflection plate It] to determine the position of the beam on the grid 6 maybe obtained in various ways, but for purposes of illustration, the device is shown for use in automatic-volume control with the tube connected to a conventional automatic volume control circuit of a construction and operation well known in the art. As shown, an input circuit ll is connected to the control grid 6 which can be biasedas desired by a grid bias connection ii. The output circuit l3, connected to the anode 2, includes the usual diode rectifier l4 connected to the conventional diode resistor l5 from which the audio frequency network is supplied. One end of the diode resistor I5 is connected through the usual filter network IE to the automatic volume control connection l1 leading to the preceding tubes of the set. This automatic volume control connection I! is connected by a lead I8 to the deflection plate l0 'so thatthevoltages developed upon. the connection H will be impressed upon the deflection plate. The circuit is supplied from the'usualvoltage' divider l9 which is connectedto the various elements of the circuit and tube in the conventional way.

In operation, the electron beam 5 shaped as a broad thin band or ribbon is deflected along the grid 6 by the deflection plates 9 and It] so that this beam impinges on the grid 6 at different points in accordance withthe differences in potential be tween the deflection plates. Owingto the diner: ence in spacing between the grids 6 and 8 at different pointsalong the grids, a dififerentfanode current-gridvoltage characteristic is obtained. at different'poi'nts along the grid 6 so that in accordance with the potential on the deflection plate Hi, the tube will operate with difierent mutual conductance characteristics. When thesignal strength is high, the voltage impressed on the deflection plate I 0 will be sufficientlyhigh to pull the beam 5 to the position B, where the mutual conductance of the tube is low. When the signal is weak, the voltage on the deflection plate Hi is lower, the beam assumes the position-A, as shown in thedrawing, and will be directed throughlthe control grid fi at a point where the mutualiconductance or mu of the-tube is high. Since: the gridconductors I extend in a direction parallel with thedirection' of deflection of the" electron beam, the transition between'the difierent cha'racteristics at different points of the grid liiwill b'e very regular and continuous, with the mu: factor decreasing regularly and continuously as the con trol' voltage onthe deflection plateiii increases with increasing output.

I- claimi 1. An electron discharge tube comprisingan anode, asource'of" electrons for producing an electronbeam to said anode, agridelectrodecomprising elongated gridconductors side byfside and extending-across thepathflof said beam and lying in surface-inclined to said anode}- and beamid'e'z flector means adjacent said path for shifting said beam lengthwise of said grid conductors from the ends nearer the anode toward the ends more remote from the anode in response to an increase in voltage on said beam deflector means.

2. An electron discharge tube comprising an anode, a cathode, beam forming means for forming the discharge from said cathode to said anode into a flattened beam, a pair of flat insulated parallel beam deflection plates spaced apart and providing a passage for the beam with the plates alongside the broad sides of the passage, and a grid electrode between said deflection plates and said anode comprising spaced parallel grid conductors extending across the path of said beam, 1;

each of said grid conductors being inclined at the same angle to said anode.

3. An electron discharge tube comprising an anode, a source of electrons for producing an electron beam to said anode, two grid electrodes positioned side by side between said source and said anode to be passed in succession by said beam, one of said grids comprising spaced para1 lel grid conductors inclined to said anode, and a pair of insulated beam deflection plates between said source and said grids spaced apart'and providing a passage between them for said beam to deflect said beam along and lengthwise of said conductors from the end nearer the anode toward the other end in response to increase in difference of potential between said deflection plates.

4. An electron discharge tube comprising an anode, a source of electrons for producing an electron beam to said anode, two grid electrodes positioned side by side between said source and said anode to be passed in succession by said beam, one of said grids being inclined to said anode, a pair of insulated beam deflection plates between said source and said grids spaced apart and providing a passage between them for said beam to deflect said beam along said inclined grid, each of said grids comprising spaced elongated parallel conductors extending across the path of said beam in the same direction as the beam is moved by said deflection plates.

JOHAN LODEWIJK HENDRIK JONKER.