EP1579469B1 - Micro-wave tube with mechanical frequency tuning - Google Patents

Abstract

This invention relates to a microwave tube ( 3 ) for generation of an electromagnetic wave with frequency F, the tube comprises mechanical means for varying the frequency F composed of a set of rings (A, B, C, D) defining a periodic structure inside the tube and mechanical means ( 4, 5, 2, G) for displacing rings with respect to each other while maintaining a periodicity for periodic structure during displacement of the rings.

Description

Technical field and prior art

The invention relates to a microwave tube with mechanical frequency tuning.

The invention finds a particularly advantageous application in the field of electronic tubes for generating and / or amplifying radio signals.

• une source d'électrons constituée d'une cathode d'émission K et d'un canon à électrons d'anodes CA pour former un faisceau d'électrons F,
• une bobine de focalisation L produisant un champ magnétique B continu axial baignant le faisceau d'électrons de façon à éviter son expansion par répulsion mutuelle entre électrons,
• une structure hyperfréquence H placée à proximité du faisceau et capable de générer, propager et amplifier une onde électromagnétique, et
• un collecteur C pour recueillir les électrons après interaction avec l'onde.

The principle of a microwave tube according to the known art is represented in figure 1 . The microwave tube comprises:

• an electron source consisting of an emission cathode K and an electron gun of anodes CA to form an electron beam F,
• a focusing coil L producing an axial continuous magnetic field B bathing the electron beam so as to avoid its expansion by mutual repulsion between electrons,
• a microwave structure H placed near the beam and capable of generating, propagating and amplifying an electromagnetic wave, and
• a collector C to collect the electrons after interaction with the wave.

Many families of tubes apply the operating principle described above, such as, for example, traveling wave tubes (TOP), BWO (Back Ward Oscillator) tubes, klystrons, magnetrons, carcinotrons, masers etc.

These tubes can operate in single-shot mode (single pulse) or recurrent mode (train pulses).

To provide very large powers, the designers use periodic structures and / or cavities which make it possible to obtain high amplifications as described in the prior art ( US-A-2,853,647 , US-A-2 945 156 , JP-A-1 204 502 and EP-A-0 401 725 ). Among these structures, there are the BWO type tubes whose schematic diagram is given in figure 2 . A type BWO tube comprises an insert I and a periodic structure P. A distance d defines the period of the periodic structure. A microwave type BWO tube is optimized for a single frequency F. It is therefore effective only in a very narrow frequency band ΔF, and even narrower than the output power is important (typically ΔF / F <5%).

In general, the microwave tubes mentioned above are optimized for working at a fixed frequency and the known means for varying the frequency of the tube always lead to a significant degradation of the performance of the tube.

The invention does not have this disadvantage.

Presentation of the invention

Indeed, the invention relates to a microwave tube according to claim 1.

According to one example, the mechanical means for moving the rings comprise a set of electrical contacts between the rings, at least one lead screw, a set of nuts mounted on the lead screw, a set of rods, each rod securely connecting a nut to a ring, the tube being provided with at least one slot allowing the passage of rods in the wall of the tube, the mother screw having several different pitch sectors able to maintain a periodicity between the rings during a rotation of the lead screw .

According to the invention, the mechanical means for moving the rings comprise a set of electrical contacts between the rings, at least one set of pins, each pin being firmly connected to a ring, the tube being provided with at least one longitudinal slot. allowing the passage of the lugs in the wall of the tube, a ring external to the tube comprising at least one set of slots, each slot of the outer ring allowing the passage of at least one lug, the slots of a set of slots having a different inclination for each ring to maintain a periodicity to the different rings when moving the rings.

The mechanical means for varying the frequency F therefore comprise at least one longitudinal slot made in the tube and allowing the passage of drive means of all the rings.

According to an additional characteristic, the microwave tube according to the invention is a TOP, a BWO type tube, a magnetron, a carcinatron or a maser.

According to yet another feature of the invention, the periodic structure of the microwave tube is corrugated sheet.

The invention has the advantage of being able to vary the frequency F of the electromagnetic wave emitted in a large range of variation, namely several tens of percent, while maintaining the amplification performance of the electromagnetic wave existing in power sources working at a fixed frequency.

The invention is advantageously applied to any source of radioelectric power consisting of an electron beam circulating through a structure comprising periodic or non-periodic shape variations.

The integrated source according to the invention comprises a periodic corrugated geometric structure which makes it possible to obtain a frequency variation by a mechanical method allowing either a modification of the pitch of the periodic structure constituted, for example, by corrugated sheet, or a variation of the length of an insert, or a combination of both structures.

This integrated system advantageously allows a rapid modulation of the parameters that are the frequency and the power of the radiofrequency signal. The system is easily automatable and able to be controlled quickly from the outside, without having to modify the operation of the electron beam.

This integrated system is particularly well suited to BWO type microwave tubes. It then replaces the periodic structures in place and / or the inserts. It is also easily adaptable to other types of tubes. It can also be associated with other systems provided to allow a variation of the output frequency of a signal. It then advantageously makes it possible to increase the efficiency and the field of operation of the system.

The frequency radiated by a tube according to the invention may advantageously be chosen in a significant range, for example several tens of%, without collapse of the output power, the other parameters of the tube (such as, for example, voltage and current). current of the electron beam) not being modified.

Brief description of the figures

• la figure 1 représente un schéma de principe de tube micro-onde selon l'art connu ;
• la figure 2 représente un schéma de principe de tube BWO selon l'art connu ;
• les figures 3A et 3B représentent un exemple de tube micro-onde;
• les figures 4A et 4B représentent un tube micro-onde selon l'invention.

Other features and advantages of the invention will appear on reading a preferred embodiment with reference to the appended figures, among which:

• the figure 1 represents a schematic diagram of microwave tube according to the prior art;
• the figure 2 represents a schematic diagram of tube BWO according to the known art;
• the Figures 3A and 3B represent an example of a microwave tube;
• the Figures 4A and 4B represent a microwave tube according to the invention.

In all the figures, the same references designate the same elements.

Detailed description of embodiments of the invention

An example of a microwave tube is shown in Figures 3A and 3B .

The electromechanical structure for adjusting the frequency of the microwave tube comprises a fixed part and a movable part.

The fixed part consists of the longitudinal wall 3 of the tube in which is formed at least one guide slot G.

• au moins une vis mère 4,
• des écrous 5 montés sur la vis mère 4,
• un ensemble de tiges 6 et un ensemble d'anneaux (par exemple quatre anneaux A, B, C, D), chaque tige 6 reliant solidement un écrou à un anneau, les anneaux étant montés à l'intérieur de la paroi 3 du tube,
• des contacts électriques 2 entre les anneaux.

The moving part comprises:

• at least one mother screw 4,
• nuts 5 mounted on the lead screw 4,
• a set of rods 6 and a set of rings (for example four rings A, B, C, D), each rod 6 securely connecting a nut to a ring, the rings being mounted inside the wall 3 of the tube ,
• electrical contacts 2 between the rings.

The guide slot or slots G allow the passage of the rods 6 in the longitudinal wall 3 of the tube to connect the nuts 5 to the rings. A ring seen in section (see figures) is, for example, shaped like a rim.

When adjusting the frequency, the lead screw is rotated, which drives the nuts 5, the rods 6, the rings A, B, C, D and the electrical contacts 2 in a translation movement. According to a variant of the first embodiment, the ring A can be connected to a mechanical part p which can then slide in the tube 3.

The mother screw 4 is monobloc. It consists of several different threading areas adapted to each of the nuts 5. A single mother screw is theoretically sufficient for the implementation of the invention. By way of non-limiting example, the figure 3A illustrates the case where the device comprises two mother screws. The second screw, when used, must then rotate in perfect synchronism with the first lead screw. The quality of the translation of the rings is improved because of the symmetrization of the application points of the movement.

A lead screw has several sectors of different pitch to keep the system, during the rotation of the lead screw, the same distance between the vertices of the periodic corrugated structure that constitute the rings.

Let L (AB) be the distance between the rings A and B, L (BC) the distance between the rings B and C and L (CD) the distance between the rings C and D.

Let (a) the pitch of the nut integral with the ring A, (2a) the pitch of the nut integral with the ring B, (3a) the pitch of the nut integral with the ring C, ( 4a) the pitch of the nut secured to the ring D.

$$\mathrm{L}\left(\mathrm{BC}\right)\mathrm{=}\left(\mathrm{3},\mathrm{1416}\right)\left(3\mathrm{a}\mathrm{-}2\mathrm{a}\right)\mathrm{=}\left(\mathrm{3},\mathrm{1416}\right)\mathrm{a}\mathrm{,}$$

$$\mathrm{L}\left(\mathrm{CD}\right)\mathrm{=}\left(\mathrm{3},\mathrm{1416}\right)\left(4\mathrm{a}\mathrm{-}3\mathrm{a}\right)\mathrm{=}\left(\mathrm{3},\mathrm{1416}\right)\mathrm{a}\mathrm{.}$$

When the lead screw rotates 180 °, the ring A moves (3,1416) x (a), the ring B moves (3,1416) x (2a), the ring C moves from (3.1416) x (3a), the ring D moves (3,1416) x (4a). He comes: $$\mathrm{The}\left(\mathrm{AB}\right)\mathrm{=}\left(\mathrm{3},\mathrm{1416}\right)\left(\mathrm{2}\mathrm{at}\mathrm{-}\mathrm{at}\right)\mathrm{=}\left(\mathrm{3},\mathrm{1416}\right)\mathrm{at}\mathrm{,}$$

$$\mathrm{The}\left(\mathrm{BC}\right)\mathrm{=}\left(\mathrm{3},\mathrm{1416}\right)\left(3\mathrm{at}\mathrm{-}2\mathrm{at}\right)\mathrm{=}\left(\mathrm{3},\mathrm{1416}\right)\mathrm{at}\mathrm{,}$$

$$\mathrm{The}\left(\mathrm{CD}\right)\mathrm{=}\left(\mathrm{3},\mathrm{1416}\right)\left(4\mathrm{at}\mathrm{-}3\mathrm{at}\right)\mathrm{=}\left(\mathrm{3},\mathrm{1416}\right)\mathrm{at}\mathrm{.}$$

la périodicité de la structure est conservée. Elle varie linéairement en fonction de la rotation de la vis.It follows that: $$\mathrm{The}\left(\mathrm{AB}\right)\mathrm{=}\mathrm{The}\left(\mathrm{BC}\right)\mathrm{=}\mathrm{The}\left(\mathrm{CD}\right)\mathrm{=}\left(\mathrm{3},\mathrm{1416}\right)\mathrm{at}\mathrm{,}$$

the periodicity of the structure is preserved. It varies linearly depending on the rotation of the screw.

The Figures 4A and 4B represent the invention.

According to the invention, the variation of the periodicity of the rings is based on the rotation of a ring equipped with slots inside which lugs connected to the periodic corrugated structures can move. The inclination of these slots is such that it allows to maintain a periodicity.

The tube 3 is the same as that of the previous assembly. Each ring placed inside the tube 3 is integral with a lug 7. A lug 7 moves inside two slots located on two independent parts, namely the fixed tube 3 and an outer ring 8. A first slot 9 placed on the fixed tube 3 allows only translational movements of the rings in the longitudinal direction of the tube. A set of slots 10, placed on the outer ring 8, make it possible to set the extent of the variations of the period of the periodic structure. They correspond to the different steps of the mother screw 4 of the assembly previous and ensures the same function. The slots 10 have a different inclination for each ring in order to maintain, during the movement of the rings, a periodicity to the different rings.

There are, on the outer ring 8, as many pairs of slots 9, 10 and lugs 7 as rings to move inside the tube 3.

The outer ring 8 can therefore be assimilated here to a set of screw-and-nut pairs of the device according to the example of the microwave tube.

According to the invention shown in Figures 4A and 4B the tube 3 comprises only one longitudinal slot 9 and the outer ring 8 comprises only one set of slots 10. The invention also relates to the case where the tube 3 comprises, for example, two longitudinal slots 9, the two longitudinal slots being then arranged symmetrically on the tube 3, and where the outer ring then comprises two sets of slots 10, the second set of slots 10 being associated with the second longitudinal slot to ensure the displacement of the rings according to the principle of the invention.

Whatever its embodiment, the mechanism according to the invention is automatable, controllable quickly from the outside and at will without modifying the operation of the electron beam.

Any mechanical system for rapidly varying the position of the rings inside the tube while maintaining a periodicity of the rings can also suit.

The embodiment of the invention described above can easily be coupled to stepping motors, to jacks placed either inside the tube or outside the tube (the movements being then carried out by the intermediate of watertight passages). The system according to the invention can be adapted to several categories of sources, without calling into question the basic principle.

According to an improvement of the invention, the microwave tube may also include an insert whose length can be adjusted. Such an adjustment is implemented by the displacement of a second tube in the tube 3, with preservation of electrical continuity. This improvement is not used in itself to make, vary the frequency of the tube. It may allow, for example, to adapt the total length of the tube (insert + periodic structure) to the length variations of the periodic structure.

Claims (4)

1. Microwave tube (3) for generation of an electromagnetic wave with frequency F, the microwave-tube comprising a periodic structure which sets the frequency F, placed inside the tube, the periodic structure being made of a set of rings (A, B, C, D), the microwave tube comprising mechanical means (4, 5, 2, G; 7, 8, 9, 10) for displacing the rings with respect to each other while maintaining a periodicity for the periodic structure during displacement of the rings, characterised in that the mechanical means for displacing the rings comprises a set of electrical contacts (2) between the rings, one set of pins (7), each pin being firmly connected to a ring, the tube (3) being provided with at least one longitudinal slit (9) through which pins (7) can pass in the wall of the tube, a ring (8) external to the tube comprising a set of slits (10), each slit (10) in the outer ring (8) allowing the passage of a pin (7), the slits in the set of slits having a different inclination for each ring so as to maintain a periodicity for the different rings during displacement of the rings.
2. A microwave tube according to claim 1, characterised in that it is a PWT, a BWO type tube, a magnetron, a carcinotron, or a maser.
3. A microwave tube according to claim 1 or 2, characterised in that the periodic structure of the microwave is made of corrugated plate.
4. A microwave tube according to claim 1, characterised in that it comprises an insert with an adjustable length.

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