GB2052143A - Microwave device of the magnetron type - Google Patents

Abstract

A magnetron arrangement includes a plurality of side-by-side multicavity strapped anode structures 1, each with a cathode 7, adjacent structures being coupled to each other along their length via a slot 11 between two cavities, one from each structure. A plurality of axially spaced strap pairs 8, 9 are incorporated in each structure at the same axial positions and with an axial spacing not greater than half a wavelength of the generated oscillations. To remove mode degeneracy and enhance stability of operation, the straps may be open, with the gaps of successive straps of each structure disposed in a helical manner about the axis of the structure (Figure 4). The output, of which there may be more than one to feed different loads, is via loop 18 and coaxial line 17. A.C. energization may be employed (Figure 3), each anode operating in turn during a cycle. <IMAGE>

Description

SPECIFICATION Microwave device of the magnetron type The invention relates to microwave electron valves and, more particularly, to microwave devices of the magnetron type.

It can find use in industrial superpower microwave apparatus, for example, in big microwave devices designed to heat plasma and sustain the thermonuclear synthesis reaction; in high-power linear electron accelerators; in big industrial microwave apparatus for production processes; in chemistry of plasma to produce new materials; and in other apparatus suitable for use in industry and agriculture.

There is provided a microwave device of the magnetron type, comprising at least two anode blocks having straps, said anode blocks electrically connecting one another and coupled together by means of coupling means equal in number to the pairs of adjacent anode blocks and each formed by the chambers of two cavity resonators, belonging to adjacent anode blocks, and a slot which couples together said chambers at the side of the inductive portions of the resonators, the straps of each anode block being electrically connected to respective vanes of the resonators, said vanes having the like polarities at the mode of oscillation, according to the invention, the straps of the unlike polarities, designed to connect electrically the vanes of the like polarities, are joined in strap pairs in each of said anode blocks, the strap pair of one said anode block being positioned approximately at the same level as the corresponding strap pairs of the remaining anode blocks and the strap pairs of the corresponding levels being located in height, relative to one another, with a pitch which is not greater than a half of the wavelength of the oscillations being generated, so that the anode blocks form a united multistage three-dimensional periodic retardation system, each two strap pairs, belonging to the adjacent anode blocks and electrically connected to the adjacent vanes of those resonators whose inductive portions incorporate the slot serving together with the chambers of the resonators as the coupling means having the unlike polarities so as to form a diaphragmed waveguide line of a periodic structure, the length of the coupling structure being equal to at least double value of the pitch between the strap pairs of the corresponding levels.

It is advantageous that the slot of each coupling means ure is formed by the adjacent vanes of the corresponding resonators, said vanes, having their base interconnected to one another, being coupled to the straps of the unlike polarities.

It is preferable that the straps of the anode blocks are implemented in the form of open rings, said open rings of each anode block being located so that gaps established between their ends, as viewed from ring to another for each strap pair, and between the strap pairs themselves, are located along a helix.

In the microwave device of the magnetron type of the invention, the electric coupling between the anode blocks is made more strong and a united multistage three-dimensional periodic retardation system is provided which offers a sufficient frequency separation, thereby ensuring stable operation of the device. The total working surface of the anode blocks can be increased so that the parameter S ,l2 becomes equal to 5-1 0, which provides for greater power output and higher electronic efficiency. The well-devised connection diagram of the anode blocks makes it possible to eliminate a degeneration of the coupled modes of oscillation, to handle all the modes using a single coupling means and to output the power generated through one of the anode blocks.With a united multistage three-dimensional periodic retardation system, the device space is used to the fullest extent, the power per unit space of the device is increased, and the surface of the electrodynamic structure is developed on a three-dimensional basis as much as possible.

The invention will now be described, by way of example, with references to the accompanying drawings in which: Figure 1 is a general view of a microwave device of the magnetron type (with a lateral section and a partial section of the housing of the anode blocks), which device is provided with a united multistage three-dimensional periodic retardation system and with parallel-arranged connections to d.c. and a.c. supply sources, according to the invention; Figure 2 is a diagrammatic representation of a united multistage three-dimensional periodic retardation system of the device of the invention, arranged in a plane of longitudinal section passing through the centers of the anode blocks, according to the invention;; Figure 3 is a view of the modification of Fig. 1 comprising a coupling slot which is formed by the adjacent vanes of the corresponding resonators of the anode block and a star-connection diagram illustrating connections to a three-phase a.c.

source, according to the invention; Figure 4 is a view of the modification of Fig. 2 comprising straps implemented as open rings whose ends are arranged along a helix, according to the invention.

The microwave device of the magnetron type of the invention is described as a magnetron generator further referred to in this text as a multianode magnetron. The latter comprises a united three-dimensional periodic retardation system which is formed by at least two anode blocks; according to the invention, there are three anode blocks 1 (Fig. 1), one central block and two side blocks, which have a height not less than 2 and are located in an evacuated housing 2. The united retardation system comprises three long periodic structures closed in azimuth direction and each comprising a chain of electrically seriesconnected resonators 3 which are of the segmenttype in the given embodiment and are implemented in the body of the anode housing 2.

Each pair of the resonators 3 has a partition which is a vane 4. The ends of the vane 4 form anode holes 5 which accommodate cathodes 6 with heaters 7; in the given embodiment, the cathodes 6 are two coaxial metallic tubes.

Each of the three anode blocks 1 comprises straps 8, 9 which are used to electrically connect respective vanes 4 of the resonators 3, said vanes 4 featuring the like polarities at the rr-mode of oscillation. Therefore, the straps 8 electrically connecting in each anode block 1 alternate ones of the vanes 4 which may be designated as the even numbered vanes have the polarity opposing that of the straps 9 which electrically connect the other vanes 4 which may be designated as the odd numbered vanes. The nearest straps 8, 9 of the unlike polarity, which are used to electrically connect the respective vanes 4 of the like polarity, are joined together in each anode block 1 in strap pairs 10 (Fig. 2). The latter are located one above another through the overall height of the anode blocks 1.Each strap pair 10 of one anode block 1 is positioned approximately at the same level as the corresponding strap pairs 10 of the other anode blocks 1, which level determines a stage of a single retardation system, whereas the strap pairs 10 of the corresponding levels are located in height, relative to one another, with a pitch not exceeding a half of the wavelength for the oscillations being generated.

As stated above, the anode blocks 1 electrically connect one another and are coupled together by means of coupling structures, namely, two coupling means 11 (Fig. 1) in the given embodiment which are formed by the chambers of two resonators 3 of the adjacent anode blocks 1 and by means of a slot 12 which couples together the chambers and is formed in each anode block 1 at the side of the inductive portions of the resonators 3. The anode blocks 1, electrically connected by means of the coupling means 11, include an azimuth periodic structure comprised of the resonators 3 and an axial (arranged in height of the anode blocks 1 ) and a lateral (propagating from one anode block 1 to another) periodic structure, the latter two structures comprising aiternate strap pairs 10, with the result that a united multistage three-dimensional retardation system is provided.

Each two strap pairs 10, belonging to the adjacent anode blocks 1 and electrically connected to the adjacent canes 4 of those resonators 3 (Fig. 1) whose inductive portions incorporate the slot 12 serving together with the chambers of the resonators as the coupling means 11, have the unlike polarities at the zO-mode of oscillation of the longest wavelength. Thus, the above-mentioned strap pairs 10 are used to form in the coupling means 11 a diaphragmed waveguide line 13 (Fig. 2) featuring a periodic structure and comprised of two parallel rows of the strap pairs 10 in the form of opposed "pins" (diaphragms) which are located, in depth d, at the opposite input sections of the coupling means 11 (Fig. 1).

The length 1 (Fig. 2) of the coupling means 11 (Fiy. 2), as measured along the height of the anode blocks 1, is equal to at least a double value 2h of the pitch h (Fig. 2) between the strap pairs 10 belonging to the corresponding levels; said length 1 is equal, in the limit case, to the total height of the anode blocks 1.

The coupling means may also be formed by means of the elements belonging to both the retardation system and to the coupling means itself. Figure 3 illustrates a modification of the coupling means 14 in which a slot 15 is formed by the adjacent vanes 4 of the corresponding resonators 3, which vanes, having their bases directly joined together, being coupled to the straps 8,9 (Fig. 4) of the unlike polarities.

Therefore, the slot 1 5 of the coupling means 14 (Fig. 3) is made in one piece with the chambers of the corresponding resonators 3.

The adjacent anode blocks 1 in the described embodiments of the device of the invention are coupled mechanically and electrically in such a manner that the centers of the anode holes 5 (Figs 1, 3) are positioned on a single axis and in a single longitudinal plane that passes through the centers of the slots 12 (Fig. 1 ) and 1 5 (Fig. 3) of the anode blocks 1.

In a more generalized case, a number of anode blocks can be positioned in a surrounding relation to the central anode blocks, electrically connect it and be coupled by virtue of the coupling means so that the centers of the three anode holes are disposed in either a single or different longitudinal planes.

The straps 8, 9 (Figs 2, 4) of the anode blocks 1 may be implemented as open rings shown in the drawing diagrammatically. It is advantageous that the rings of each anode block 1 be located so that gaps 1 6 (Fig. 4) between their ends, as viewed from one ring to another for each strap pair 10, and between the strap pairs 10 themselves, are located along a helix.

An output coupling means 1 7 (Figs 1, 3) designed to output the energy being generated is implemented in the above-mentioned embodiments as a doubled inductive loop 18 and a coaxial waveguide line 19, which are mounted on a desirable anode block 1, side or central.

According to Figs 1, 3 the means 1 7 is mounted on the central anode block 1.

When the device of the invention is utilized as a power amplifier and in the case when the power output should be distributed among several consumers, the number of the ouput means can be increased as it is required.

The cathodes 6 with the heater 7 are affixed to the respective anode blocks 1 in axial relation to the anode holes 5 by means of vacuum-type metallic-ceramic insulators 20 (cathode lugs). The latter include terminals 21, 22 by which the filament circuits of the heaters 7 and the anode voltage circuits are couplet to supply sources Un, Ua. The housing 2 of the anode blocks 1 is held at a positiva potential Ua and is grounded.

Figure 1 illustrate a modification of the device of the invention in which the three cathodes 6 and heaters 7 are coupled in a parallel fashion to the feeder line of the supply sources Un, Ua, that connection being fulfilled according to the grounded anode chassis circuit.

Figure 3 illustrates another modification of the device of the invention and its connection diagram. Here, the anode voltage is taken from a three-phase a.c. mains in accordance with a starconnection circuit. The voltage provided by each phase is applied to a respective cathode 6, the housing 2 is coupled to the zero point of the star connection, and the filament current passes to the heater 7 from individual supply sources Uni, U,,2, Un.

The microwave device of the magnetron type of the invention operates in the following manner.

The cathodes 6 (Fig. 1) located at the centers of the anode holes 5 of the evacuated housing 2 are heated to the required temperature using the heaters 7 which are coupled to the supply source U, of the filament circuit. The electrons emitted by the cathodes 6 into the interaction region between the ends of the vanes 4, forming the anodes, and the cathodes 6 are accelerated by an electric field established by the anode voltage supply source Ua which is inserted between the cathodes 6 and anodes according to a parallel supply circuit. In the presence of a magnetic field directed along the axis of the anode blocks 1, at a certain value of the anode voltage, the electrons tends to excite r.f.

oscillations in the retardation system of the device, when working through the gaps between the vanes 4. An r.f. field created within the gaps operates to group the electrons in beams. The latter, under the action of the applied anode voltage and magnetic field, are moved along the anode surface in synchronism with the excited slow wave carrying r.f. oscillations, which wave being maintained its retarding phase; thus, the beams transmit the energy received from the supply source U, a to an r.f. electromagnet,c field and the energy of the d.c. supply source is converted to microwave oscillation energy. The latter is accumulated in the resonators 3 of the respective anode blocks 1 constituting the retardation system of the device.This united multistage three-dimensional periodic retardation system is held in a resonance condition at that mode of oscillation whose frequency corresponds to the synchronous movement of the electron flow which interacts with the electromagnetic wave representing only this mode of oscillation.

The device of the invention of Fig. 1 operates in the self-oscillator mode, usually at the 7rO-mode of the longest wave (the type TEo, N 2 wave). The device is advantageous in that it can be operated in the amplification mode using an external control signal. The TE0, N 2 wave with an azimuth variation corresponding to the phase shift between the adjacent vanes 4 and equal to'r, and with an axial variation of the field between the ends of the anode blocks 1 equal to zero, is excited in each of the three anode blocks 1. In the case of the resonators coupled together with slots in the anode blocks, there results at the longest mode, at the coupling frequency f1, r.f.

oscillations which have equal amplitudes and are phase-synchronized. The electromagnetic energy can also be accumulated in the anode blocks 1 at two other coupling frequencies f2, f3 which correspond to the 7r0-mode of osciliation. At the frequency f2, the oscillation amplitude is equal to zero in the central anode block 1, while in the side anode blocks 1 the oscillation amplitudes are equal in amplitude but have a 1 800 shift. At the frequency f3, the oscillation amplitudes in the side anode blocks 1 are equal to each other and cophasal, while in the central anode block 1 the oscillation amplitude is shifted by 1800 with respect to the first two.

The stability of operation of the device with the coupled anode blocks 1 is increased at the 7rO-mode of oscillation with an increase in the separation between the coupling frequencies. This frequency separation is greatly dependent on the coupling factor for the anode blocks 1 and the operative condition of the device with the coupled anode blocks is practically determined by the degree of coupling only.

In addition, the degree of coupling determines an effectiveness of summation of microwave powers of the oscillations being generated, performed in each anode block 1, as well as an effectiveness of launching the total microwave power, via one of the anode blocks, into a useful load.

The device of the invention is advantageous in that the multistage three-dimensional periodic retardation system provides for the coupling factor of the anode blocks 1 equal almost unity. This advantage is a result of a multistage and periodic arrangement of the joined strap pairs 10 (Fig. 2) comprised of the straps 8, 9. The strap pairs 10 are located at the same levels in the coupled anode blocks 1 and the strap pairs 10 of the corresponding levels are separated by a pitch h not exceeding a half of the wavelength .1 (h S) 2 The electromagnetic wave of the abovementioned retardation system is characterized by three phase shifts 0, per period p, which determine the wave vector ,B.In such retardation system, the flow of r.f. energy P tends to rise and the energy transfer velocity P Ve= W rises too, where W is the average energy stored per unit length of the retardation system in the direction of the flow propagation. Since the velocity Va in the three-dimensional periodic system is equal to the group velocity Vg, the latter rises too and the separation of the coupling frequencies is increased.

An increase in the degree of coupling in a wide bandpass is caused by the fact that the length 1 (Fig. 2) of the slots 12 of the coupling means 11 (Fig. 1), as measured along the anode blocks 1, is increased up to a waveguide size, namely, to not less than a half of the wavelength, which is the critical wavelength of the oscillations at the 7rO-mode. The straps 8, 9 (Fig. 2) coupled to the adjacent vanes 4 of the resonators 3 (Fig. 1), whose chambers constitute the coupling means 11, are used to form, along the overall length of the slots 12, the diaphragmed periodic waveguide line 13 (Fig. 2) at the input sections of the slots 12.The line 13 provides for a wide-band conversion of the r.f. energy at the mode of oscillation, from one anode block 1 to another, since the amplitudes of the r.f. oscillations at the 7mode, at the opposite input sections (in depth d) of the coupling means 11 (Fig. 1), will be given a 1800 phase shift and equal to each other. The amplitude of the r.f. oscillations along the length 1 of the coupling means 11 and, therefore, slots 12 corresponds to the amplitude of the corresponding n-mode in the interaction region of the anode blocks 1 through their overall height.

The device of the invention is advantageous in that, along with an increase in the electrical coupling between the anode blocks 1 , there results the separation of the coupling frequencies not only at the rr-mode but also at the modes with the phase shift jEc7r and, in particular, at the N - -- )mode.

2 Since the anode blocks 1 connect one another and the coupling means 11 establishes a coupling between them, the device of the invention is given a new feature which consists in a selective nature of the coupling at different modes of oscillation. In addition, a doubled degeneration of the modes with the phase shift 0-tO, related to the symmetry of a single anode block 1, is eliminated.

As a result, the device of the invention features a stable operation at the 7r0-mode and the working area of the volt-ampere characteristic is increased.

Therefore, the electromagnetic wave at the n-mode of oscillation propagates from one anode block 1 to another at almost the same group velocity as within each anode block 1 and the flow of the electromagnetic energy from all the anode blocks 1 is summed up without loss in the coupling means 11 and can be output via one of the anode blocks 1.

The total r.f. power output is outputted via the central anode block 1 by virtue of the output coupling means 17 comprised of a doubled inductive ioop 1 8 which is connected to two resonators 3, and is then passed through a coaxial waveguide line 1 9 (or a waveguide line) to a load via a metallic/ceramic output fitting with a dielectric evacuated window (an r.f. load and the window are not shown in the drawing).

To provide for much more electric coupling between the anode blocks 1, which improves mutual synchronization of the r.f. oscillations in the anode blocks 1, increases the separation of the frequencies of the operating mode and undesirable modes, ensures more stable device operation and effective summation of the power outputs of the anode blocks 1 in a single output coupling means 17, the coupling means 14 can be implemented in accordance with Fig. 3. In this modification, the slot 1 5 of the coupling means 14 is formed directly by virtue of the adjacent vanes 4 of the resonators 3 of the adjacent anode blocks 1, the vanes, having their bases jointed together, being coupled to the straps of the unlike polarities.

Such a construction provides for close coupling in which case d < (Fig. 4) and undesirable coupling loss through a deep slot 1 5 are eliminated especially when the depth d of the slot 1 5 is commensurate with the wavelength, i.e., d > /2.

The discontinuities in the strap pairs 8, 9 of the anode blocks 1, which are made as open rings, tend to disturb the azimuth symmetry of the retardation system of the anode blocks 1, with the result that the doublet modes with the phase shift s*0,7r are not degenerated and the electric coupling between the anode blocks 1 at these modes is increased. This allows for better loading of the non-working modes with the phase shift s6$07F, in particular, the N - 1)-modes using a single output coupling means 17 (Fig. 3) so that more stable operation of the device is attained at the working rr,-mode of oscillation.

The discontinuities in the straps 8, 9 (Fig. 4) tend to decrease to some extent frequency separation including the 7r0-mode and the adjacent azimuth N - -- )mode.

2 The non-working N (--1)-rhode 2 must be loaded by increasing the coupling between the anode blocks 1 and using the straps 8, 9 in the form of open rings; on the other hand, the frequencies of the 7ro- and N (- -1 )-modes 2 must be separated sufficiently. Thus, the required trade-off consists in such iocation of the open rings at which the gaps 1 6 between their ends in each anode block 1 are arranged along a helix. In this case, at each stage of the retardation system, formed by the corresponding strap pairs 10 the N - -- )mode 2 of oscillation changes the azimuth orientation angle of the amplitude of the r.f. field and is frequency-separated from the 7ro mode to a greater extent.The degeneration of the doublet modes is eliminated with the result that the coupling between the anode blocks 1 is increased at the fequency of the N - -- )mode 2 in particular, and at the modes with the phase shift +0,7r in general case. Therefore, the condition of loading the modes characterized by 0*0,7r via the output coupling means 1 7 (Fig. 3) is improved and their competition is decreased. It is thus advantageous that the device of the invention has a multistage three-dimensional periodic retardation system in which the strap pairs 8, 9 (Fig. 4) are made in the form of open rings whose ends are arranged along a helix through the overall height of the anode blocks 1.

The connection of a multianode (three-anode in the given embodiment) device according to Fig. 3 makes it possible to utilize an a.c. mains without special rectifiers necessary for the modification of Fig. 1. In the embodiment of Fig. 3, the anode blocks 1 operate in turn during each positive period of a certain phase, with a 1 200 phase shift.

In the embodiments of Figs 1, 3 relating to the coupling means 11, 14 all the eight possible modes of coupled oscillation are non-degenerated and orthogonal according to the theory of group representation. These modes do not interact with one another, which ensures effective operation of the device.

The design features and modifications of the device of the invention provide for a new multistage three-dimensional periodic retardation system based on sevsral anode blocks electrically joined to one another and coupled together, and for an increase in the power output due to an increase in the overall working surface of the retardation system, anode blocks and cathodes.

Thus, the multianode microwave device of the magnetron type is given a stronger coupling between the anode blocks. As a result, the maximum permissible size of the overall working anode surface is attained, S A2 5 to 10, with an appreciable degree of frequency separation for the 7rO-mode and the non-working concurrent modes. In addition, the powers at the generated (or amplified) working frequency are summed up using a single output means, with the result that a greater power output is obtained.

Claims (4)

1. A microwave device of the magnetron type, comprising at least two anode blocks having straps, said anode blocks being electrically joined to one another and coupled together by virtue of coupling means equal in number to the pairs of the adjacent anode blocks and formed by the chambers of two resonators, belonging to the adjacent anode blocks, and a slot which couples together said chambers at the side of the inductive portions of the resonators, the straps of each anode block being electrically connected to respective vanes of the resonators, said vanes having the like polarities at the n-mode of oscillation, the straps of the unlike polarities, designed to connect electrically the vanes of like polarities, being joined in strap pairs in each of the anode blocks, a strap pair of an anode block being positioned approximately at the same level as the corresponding strap pairs of the remaining anode blocks and the strap pairs of the corresponding levels being located in height, relative to one another, with a pitch which is not greater than a half of the wavelength of the oscillations being generated, so that the anode blocks form a united multistage three-dimensional periodic retardation system, each two strap pairs, belonging to the adjacent anode blocks and electrically connected to the adjacent vanes of those resonators whose inductive portions incorporate the slot serving together with the chambers of the resonators as the coupling means, having the unlike polarities so as to form in the coupling means a diaphragmed waveguide line of a periodic structure, the length of the coupling means, as related to the height of the anode block being equal to at least a double value of the pitch between the strap pairs of the corresponding levels.

2. A device as claimed in claim 1 , wherein the slot of each coupling means is formed by the adjacent vanes of the corresponding resonators, the vanes, having their bases directly joined together, being coupled to the straps of the unlike polarities.

3. A device as claimed in claims 1, 2, wherein the straps of the anode blocks are implemented in the form of open rings, said open rings of each anode block being located so that gaps established between their ends, as viewed from one ring to another for each strap pair, and between the strap pairs themselves, are located along a helix.

4. A microwave device of the magnetron type substantially as hereinbefore described with reference to the accompanying drawings.