EP0711451A1 - Dispositif d'attenuation d'ondes parasites pour tube electronique et tube electronique comportant ce dispositif - Google Patents
Dispositif d'attenuation d'ondes parasites pour tube electronique et tube electronique comportant ce dispositifInfo
- Publication number
- EP0711451A1 EP0711451A1 EP94922299A EP94922299A EP0711451A1 EP 0711451 A1 EP0711451 A1 EP 0711451A1 EP 94922299 A EP94922299 A EP 94922299A EP 94922299 A EP94922299 A EP 94922299A EP 0711451 A1 EP0711451 A1 EP 0711451A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- resistive elements
- attenuation device
- wall
- resonator
- coaxial
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J25/00—Transit-time tubes, e.g. klystrons, travelling-wave tubes, magnetrons
- H01J25/02—Tubes with electron stream modulated in velocity or density in a modulator zone and thereafter giving up energy in an inducing zone, the zones being associated with one or more resonators
- H01J25/04—Tubes having one or more resonators, without reflection of the electron stream, and in which the modulation produced in the modulator zone is mainly density modulation, e.g. Heaff tube
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J19/00—Details of vacuum tubes of the types covered by group H01J21/00
- H01J19/28—Non-electron-emitting electrodes; Screens
- H01J19/32—Anodes
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J19/00—Details of vacuum tubes of the types covered by group H01J21/00
- H01J19/78—One or more circuit elements structurally associated with the tube
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J23/00—Details of transit-time tubes of the types covered by group H01J25/00
- H01J23/36—Coupling devices having distributed capacitance and inductance, structurally associated with the tube, for introducing or removing wave energy
- H01J23/54—Filtering devices preventing unwanted frequencies or modes to be coupled to, or out of, the interaction circuit; Prevention of high frequency leakage in the environment
Definitions
- the present invention relates to a device for attenuating unwanted parasitic waves liable to appear in electronic tubes with coaxial cylindrical electrodes.
- This attenuation device is particularly advantageous in a grid tube to avoid the appearance of undesirable modes and in particular of the TEH mode.
- Grid tubes are generally of the tetrode or triode type.
- an additional grid called screen grid placed between the control grid 2 and the anode 3.
- Each inter-electrode space is associated with a resonant cavity 5 consisting of cylindrical walls 4 extending the electrodes and limited in height by a movable piston 6 allowing frequency adjustment.
- FIG. 1 only the resonant cavity associated with the inter-electrode space control gate 2-anode 3 is shown completely for the sake of clarity.
- connection between an electrode and a wall 4 of cavity is provided by a conductive collar 7 in the form of a cup, fixed to the electrode and possibly a conductive crown 8, comprising elastic contacts, inserted between the collar 7 and the wall 4.
- a conductive collar 7 in the form of a cup, fixed to the electrode and possibly a conductive crown 8, comprising elastic contacts, inserted between the collar 7 and the wall 4.
- the electrodes are often brought to a continuous potential with respect to the cathode 1, it is advisable to insert a capacitor producing an HF short circuit and blocking of the direct current between a ring 8 and a cylindrical wall for example.
- the collars 7 are electrically insulated from each other by ceramic spacers 9 which also have functions of mechanically holding the electrodes of the tube and sealing the vacuum. A difference of several thousand volts may exist between the control grid 2 and the anode 3 for example.
- the inter-electrode space associated with its resonant cavity 5 forms a coaxial resonant circuit normally resonating in the TEM mode.
- the resonant circuit can however resonate on several other modes, some of which are particularly troublesome, for example TE11 mode. It is the dominant mode of TE modes in coaxial resonators and has the lowest cutoff frequency.
- the TM modes have them, for the same resonator, much higher cut-off frequencies and are less annoying. Indeed, the higher the frequency of a guided mode, the greater the losses it causes in the walls. Waves corresponding to modes with a high cut-off frequency absorb quickly and cannot propagate.
- a microwave signal is injected at the level of the cavity of the input resonant circuit situated between the cathode 1 and the control grid 2 and the signal after amplification is extracted at the level of the cavity of the output circuit located between the control grid 2 and the anode 3.
- parasitic resonances on undesirable modes established in the output resonant circuit can excite the input resonant circuit and give rise to sustained oscillations.
- a first known solution consists in coupling wave guides each terminated by an absorbent to the resonant output circuit. These waveguides are placed radially around the resonant cavity. The dimensions of the guides are chosen so as not to influence the TEM mode. These guides have a cutoff frequency which is between the frequency of the unwanted modes and the frequency range of the amplifier. The opening of these guides forms in the outer wall of the resonant cavity series inductances which are traversed by the surface currents generated by the TEM mode. This has the effect of moving the frequency range of the amplifier downwards.
- Another known solution consists in placing above the control grid or the screen grid, in the bottom of the anode which is generally a little wider than the part bombarded by electrons, a cylindrical conductive structure comprising several resonant circuits.
- RLC type with distributed constants tuned to the frequency of the parasitic waves to be attenuated.
- the material of the structure is chosen so that it has high losses.
- This solution has the drawback of being selective: the conductive structure only works in a narrow band since it includes resonant circuits. Given the limited space available in the anode, it is difficult and even impossible to accommodate other conductive structures whose resonant circuits are tuned to other frequencies to be eliminated.
- Another known solution consists in placing in the outlet cavity ferrites having high losses for the frequencies of the parasitic waves.
- the present invention aims in particular to remedy all these drawbacks. To achieve this, it proposes a device for attenuating unwanted waves for electronic tube with coaxial electrodes which is simple to produce and therefore inexpensive, which is effective on a plurality of frequencies and which does not modify the size of the tube.
- the present invention relates to a device for attenuating unwanted waves appearing in an electronic tube comprising at least two coaxial cylindrical electrodes. These two electrodes help to form the walls of a coaxial resonator.
- the parasitic waves to be attenuated generate surface currents in the walls of the coaxial resonator.
- the parasitic wave attenuation device comprises resistive and electrically conductive elements which are inserted into at least one wall of the resonator so as to cut the surface currents generated by the parasitic waves in the wall.
- resistive and electrically conductive elements inserted directly into the wall of the resonator, are completely linked from the high frequency point of view to the wall of the resonator.
- These resistive elements are capable of attenuating all the undesirable modes insofar as they are crossed by the surface currents generated by these modes.
- the resistive elements are directed along the generatrices of a cylindrical wall of the coaxial resonator.
- resistive elements in pyrolitic graphite because of its electrical and thermal properties. This is particularly the case when the resistive elements are bombarded by the electrons emitted by the cathode.
- the invention also relates to an electronic tube which includes such a device for attenuating unwanted waves.
- This electron tube can belong to the family of grid tubes or magnetrons.
- FIG. 4a and 4b a detail of the resistive elements of the attenuation device according to the invention
- - Figure 5 a partial longitudinal section of a grid tube provided with an attenuation device according to the invention
- FIG. 6 a detail of a grid tube anode provided with an attenuation device according to the invention.
- FIG. 2a represents, in transverse section, a coaxial resonator of an electronic tube with coaxial cylindrical electrodes conforming, for example, to that represented in FIG. 1. It is assumed that the cut was made at the level of the active part of the anode 3 and only the control grid 2 is shown. The cut could have been made in the resonant cavity which extends the anode and the grid.
- the anode 3 forms the outer wall of the resonator and the control grid 2 the inner wall.
- On this section are drawn in dashed lines the magnetic field lines and in solid lines the electric field lines for TE11 mode (particularly troublesome). We see two magnetic field nodes represented by the diametrically opposite points s and s, at the level of the internal surface of the external wall of the resonator. The electric fields are substantially radial in this section.
- FIG. 2b represents a development of a half circumference of the internal surface of the external wall of the resonator of FIG. 2a.
- the half-circumference is taken on either side of point s.
- the dashed lines represent the distribution of the surface currents which are established in this wall for the TE11 mode. These currents have a component directed along the axis YY 'which is normal to the axis XX' of the tube and in the plane of the developed wall. This amounts to saying that these currents all have a tangential component to the outer wall of the coaxial resonator. It is the same in the inner wall of the resonator.
- the other unwanted TE-type modes also generate currents with a tangential component in the interior and interior walls of the coaxial resonator.
- the currents generated by the useful mode TEM are directed longitudinally along the axis XX 'and have no tangential component.
- resistive and electrically conductive elements are inserted into at least one of the walls of the resonator so that they cut the surface currents created in this wall by the undesirable mode or modes. Surface currents pass through these resistive elements and dissipate energy in the form of heat. The parasitic waves giving rise to these surface currents are thus attenuated.
- Figures 3a, 3b respectively show a longitudinal section and a cross section of a resonator output circuit of a grid tube provided with an attenuation device according to the invention.
- the resistive elements referenced 10 are bars inserted in the internal wall of the anode according to generatrices. These bars 10 are opposite the control grid 2 and therefore are bombarded by the electrons emitted by the cathode. These bars attenuate the modes which generate surface currents having a tangential component while the surface currents which have only a longitudinal component are not disturbed.
- bars 10 will advantageously be rectangular parallelepipeds and in the example described, they are three in number.
- Grooves 11 have been dug in the inner wall of the anode 3 and the bars are fixed in the grooves 11 by brazing for example. It is preferable not to disturb the TEM mode to limit the area of the bars 10 offered to electronic bombardment.
- the bars 10 are made of a resistive and electrically conductive material.
- Pyrolitic graphite is a particularly interesting material for making these bars.
- Pyrolitic graphite also called oriented graphite is essentially a crystallized graphite obtained by thermal decomposition of a gaseous hydrocarbon on the surface of a material brought to very high temperature under controlled atmosphere. A layer of graphite is thus deposited.
- Pyrolitic graphite has an electrical anisotropy which is essentially linked to its crystallographic structure. In a normal direction (called axis C) to the deposition plane, its electrical resistivity is much greater than in a direction parallel to the deposition plan.
- FIG. 4b The cross section of the bars 10 has not been modified compared to FIG. 4a. It is preferable to use an odd number of resistive elements so as not to give a preferential position for establishing a parasitic mode.
- the surface currents generated in the walls of the resonator have, along the periphery, an even number of current nodes. In the outer wall, these nodes (for TE11 mode) are placed on generatrices passing through the points s and s' represented in FIG. 2a.
- the TE11 mode could be established without being really attenuated because these resistive bars would not cut the surface currents generated by the parasitic mode.
- the resistive elements have been placed in the anode. It is possible to place them in another place but always in at least one of the walls of the resonator. In FIG. 5, they are inserted into the outer wall of the resonant cavity 5. It could of course also be envisaged that the resistive elements are inserted into the anode but at its upper part, above the grid as in the figure 6 illustrates this.
- each resistive element is always very strongly linked from a high frequency point of view with one of the walls of the coaxial resonator since it is inserted directly into this wall.
- the electric field is radial at the level of the resistive elements.
- the electronic tube with coaxial cylindrical electrodes described is a grid tube. This grid electron tube can be used in particular as a television amplifier or in a particle accelerator or even in an industrial installation using high frequencies.
Landscapes
- Microwave Tubes (AREA)
Abstract
Description
Claims
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FR9309432A FR2708785B1 (fr) | 1993-07-30 | 1993-07-30 | Dispositif d'atténuation d'ondes parasites pour tube électronique et tube électronique comportant ce dispositif. |
FR9309432 | 1993-07-30 | ||
PCT/FR1994/000926 WO1995004366A1 (fr) | 1993-07-30 | 1994-07-22 | Dispositif d'attenuation d'ondes parasites pour tube electronique et tube electronique comportant ce dispositif |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0711451A1 true EP0711451A1 (fr) | 1996-05-15 |
EP0711451B1 EP0711451B1 (fr) | 1998-01-14 |
Family
ID=9449815
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP94922299A Expired - Lifetime EP0711451B1 (fr) | 1993-07-30 | 1994-07-22 | Dispositif d'attenuation d'ondes parasites pour tube electronique et tube electronique comportant ce dispositif |
Country Status (5)
Country | Link |
---|---|
US (1) | US5894197A (fr) |
EP (1) | EP0711451B1 (fr) |
DE (1) | DE69407976T2 (fr) |
FR (1) | FR2708785B1 (fr) |
WO (1) | WO1995004366A1 (fr) |
Families Citing this family (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB2360872B (en) * | 2000-03-30 | 2004-05-05 | Marconi Applied Techn Ltd | Magnetrons |
FR2828007B1 (fr) * | 2001-07-27 | 2004-02-13 | Thales Sa | Dispositif d'amplification d'un signal haute frequence |
US20170047633A1 (en) * | 2015-08-11 | 2017-02-16 | Keysight Technologies, Inc. | Signal transmission line and electrical connector including electrically thin resistive layer and associated methods |
US10109904B2 (en) * | 2015-08-11 | 2018-10-23 | Keysight Technologies, Inc. | Coaxial transmission line including electrically thin resistive layer and associated methods |
WO2019074470A1 (fr) | 2017-10-09 | 2019-04-18 | Keysight Technologies, Inc. | Fabrication de câble coaxial hybride |
Family Cites Families (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR1373741A (fr) * | 1963-08-06 | 1964-10-02 | Thomson Houston Comp Francaise | Perfectionnements aux tubes électroniques pour fréquences très élevées |
FR2116725A5 (fr) * | 1970-12-04 | 1972-07-21 | Thomson Csf | |
FR2275017A1 (fr) * | 1974-06-11 | 1976-01-09 | Thomson Csf | Dispositif d'attenuation d'ondes parasites tres courtes, utilisable en particulier dans des tubes electroniques, et tubes electroniques comportant de tels dispositifs |
FR2276685A1 (fr) * | 1974-06-28 | 1976-01-23 | Thomson Csf | Dispositif d'attenuation d'ondes parasites tres courtes, utilisable notamment dans des tubes electroniques, et tubes comportant de tels dispositifs |
FR2276682A1 (fr) * | 1974-06-28 | 1976-01-23 | Thomson Csf | Dispositif d'attenuation d'ondes parasites tres courtes pour tubes electroniques a electrodes cylindriques coaxiales, et tubes comportant de tels dispositifs |
FR2298184A1 (fr) * | 1975-01-14 | 1976-08-13 | Thomson Csf | Dispositif de suppression d'oscillations parasites et tube electronique comportant un tel dispositif |
DE2632404C3 (de) * | 1976-07-19 | 1979-03-15 | Siemens Ag, 1000 Berlin Und 8000 Muenchen | Hochfrequenz-Elektronenröhre mit einer Einrichtung zur Dämpfung von Hohlraum-Störwellen |
US4349424A (en) * | 1981-05-15 | 1982-09-14 | The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration | Ion sputter textured graphite |
DE3134034A1 (de) * | 1981-08-28 | 1983-03-10 | Gesellschaft für Schwerionenforschung mbH, 6100 Darmstadt | "absorber" |
-
1993
- 1993-07-30 FR FR9309432A patent/FR2708785B1/fr not_active Expired - Fee Related
-
1994
- 1994-07-22 WO PCT/FR1994/000926 patent/WO1995004366A1/fr active IP Right Grant
- 1994-07-22 EP EP94922299A patent/EP0711451B1/fr not_active Expired - Lifetime
- 1994-07-22 DE DE69407976T patent/DE69407976T2/de not_active Expired - Fee Related
- 1994-07-22 US US08/586,819 patent/US5894197A/en not_active Expired - Fee Related
Non-Patent Citations (1)
Title |
---|
See references of WO9504366A1 * |
Also Published As
Publication number | Publication date |
---|---|
FR2708785A1 (fr) | 1995-02-10 |
DE69407976D1 (de) | 1998-02-19 |
US5894197A (en) | 1999-04-13 |
FR2708785B1 (fr) | 1995-09-01 |
DE69407976T2 (de) | 1998-05-28 |
EP0711451B1 (fr) | 1998-01-14 |
WO1995004366A1 (fr) | 1995-02-09 |
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