US3113239A

US3113239A - Magnetron type amplifier

Info

Publication number: US3113239A
Application number: US36522A
Authority: US
Inventors: Hass Walter
Original assignee: MIWAG Mikrowellen AG
Current assignee: MIWAG Mikrowellen AG
Priority date: 1959-06-16
Filing date: 1960-06-16
Publication date: 1963-12-03
Anticipated expiration: 1980-12-03
Also published as: GB960245A

Description

Dec. 3, 1963 w. HAss 3,113,239

MAGNETRON TYPE AMPLIFIER Filed June 16, 1960 2 Sheets-Sheet 1 .Hl y l Vl A/ tu 7%5f J /V 7 70 y fr I I4 gy/ f4 ,/7' N35 /2 wwf/W Dec. 3, 1963 w. HAss 3,113,239

MAGNETRON TYPE AMPLIFIER Filed June 16, 1960 2 Sheets-Sheet 2 United States Patent 3,113,239 MAGNE'IRON TYPE AMPLIFIER Walter Hass, Freiburg im Breisgau, Germany, assignor to MWAG Mikrowellen A.G., Basel, Switzerland Filed June 16, 1969, Ser. No. 36,522 Claims priority, application Germany June 16, 1959 3 Claims. (Cl. S15-39.77)

This invention relates to a travelling-field magnetron constructed as an amplifying tube.

A special form of this category of tubes, one that starts from the usual form of the strapped magnetron, has become known by the designation Platinotron See, for example, the article entitled Description and Operating Characteristics of the Platinotron by W. C. Brown in the Proceedings of the IRE 1957, page 1209. It is distinguished from an ordinary strapped magnetron by the fact that the sequence of resonators arranged concentrically around the cathode is severed with respect to high frequency at one place, and the beginning and end of the separated resonator sequence receive in each case, by Way of the likewise separated phase rings (straps), a highfrequency conducting connection. The phase-ring conductor periodically loaded with the resonators thus acquires, with suitable electrical dimensioning, the character of a delay line or band-pass conductor, andthe magnetron, hus modified, acquires the character of a wide-band ampli- Now it is known that strapped magnetrons and their modifications can only be employed for wave lengths of more than about 3 centimetres. For smaller wave lengths the phase rings no longer admit of being manufactured with sufficient exactitude. For the range of wave lengths below 3 centimetres the so-called Rising Sun form has been adopted, which indeed, with respect to the stabilising of the 11F-mode, completely replaces the function of the phase rings, but does not immediately appear suited for the construction of a band-pass conductor. Hence only tubes of the nature of the Platinotron have hitherto been known for wave lengths far above the critical wave length range of 3 centimetres.

This invention shows a way to manufacture amplify ing tubes of the magnetron construction for the range of shorter wave lengths also. It makes use of the possibility of replacing the phase rings by a tubular conductor or wave-guide.

The adoption of a wave-guide as a phase conductor in the magnetron is already known as disclosed in German Patent 839,950. It was proposed to place a rectangular Wave-guide concentrically around or co-axially beside the magnetron anode, and to couple it with the anode oscillatory spaces by means of a slit. In that case, however, the wave-guide forms a closed ring which is not severed with respect to high frequency wave energy because those waves can propagate continuously around and around the ring. That arrangement is intended to stabilize the 1rmode in the normal magnetron and, therefore, does not suggest the idea of operating the magnetron as a wider band amplifier.

The main difficulty that stands in the way of employing a wave-guide in the amplifying magnetron resides in the requirement of suiicient agreement between the angular velocity of the wave-guide wave and that of the stream of electrons, It has hitherto seemed that this requirement could not readily be fulfilled, since the phase velocity of the wave-guide wave is greater than the Velocity of light, whereas within the scope of the practically controllable operative voltages, the speed of flow of the electrons is less by about one order of magnitude.

The subject of this invention is an amplifying tube of the magnetron type, with a cathode, and having resonators axially symmetrically arranged in relation to the axis of ICC the cathode, the resonators being surrounded by a waveguide ring. It is characterized by the feature that the wave-guide ring is severed at one place with respect to high frequency and is provided with high-frequency supply leads, and that the resonators are coupled to the wave-guide ring individually by way of such a long radial coupling path that the angular velocities of the waved guide wave and of the electron wave are equal.

By this arrangement the wave of the wave-guide is transmitted to a circuit path located nearer to the cathode. The phase velocity is therefore transformed, in proportion to the diameter of the path, and is in this way adapted to readily realizable operative data.

What is particularly advantageous is the electrical decoupling between the high-frequency supply leads (input and output), in the case of the amplifier tube shown in FIG. 1, by means of a metallic transverse partition in the wave-guide. lt must here be emphasized that such a separation constitutes a simpler and more reliable measure for avoiding undesirable external reaction than is possible with the use of straps.

With respect to the necessary band-pass character of the wave-guide ring, the resonators, coupled to the waveguide ring, of the actual magnetron system are to be constructed as sections, open towards the cathode, of Lecher conductors or wave-guides with a series-resonance character. These resonators, the centre lines of which, in the axis of the wave-guide ring for example, are at a distance of about M4 from one another, therefore solve a twofold problem: on the one hand they form the series-coupled series oscillatory circuits that are necessary in the sense of the band-pass character of the ring conductor, and they also form the medium of the alternating action between the flow of electrons and the wave-guide ring which is required for the functioning as an amplifying tube.

In order to adapt the necessary radial distance between the wave-guide ring and the segment heads to the desired operative conditions of the tube, it may be advantageous to increase the electrical length ofthe resonators by single or multiple amounts of M2. A particularly advantageous kind of construction is however characterized by the feature that between the resonator and the wave-guide ring special wave-guide sections are interposed, which are preferably directed radially to the axis of the cathode. Their length should amount to at least about a quarter of the wave length.

The adaptation of the radial distance between the waveguide ring and the resonator heads is advantageously facilitated by these strappings or coupling conductors being given an inclined or curved course, deviating from the radial direction. An advantageous construction of the strappings consists in constructing them as flat rectangular wave-guide sections terminating in slots in the guidebeam plane of the wave-guide ring and coupling slots in the resonators, the shorter cross-sectional side of the said sections being selected, in a manner known in itself, to supply the required impedance match between the resonator and the wave-guide.

The abovementioned electrical separation between input and output must also be carried out within the sequence of resonators. It is advantageous to utilize for this purpose the peripheral range that is claimed by the input and output lines. In this sector, which is necessarily free from coupling slots, the resonators are constructed as high-frequency separation of the resonator sequence. This is advantageously effected in such a way that the resonators arranged here are de-tuned in relation to the useful-wave range, or else are partly replaced by solid electrodes. In this case a resonator which is not detuned, arranged for instance in the middle of the separating sector, may be given a high-frequency supply lead of its own, by means of which the functioning of the tube is controlled. This resonator may alternatively be replaced by an electrode with a simple supply lead. It is likewise utilized for the control, by means of direct voltage or low-frequency voltage.

The space required on the wave-guide parting place for the inward and outward lead wires, in which space are also included means known in themselves for diminishing the reflection loss due to impedance discontinuity, can be rendered unnecessary by placing the wave-guide ring in the form of one or more helical turns around the inner system. This arrangement has the advantage that the inward conductors are particularly simple in shape and free from such discontinuity.

One constructional example of the invention is illus trated in the accompanying drawings, in which:

FIGURE 1 shows the tube in a central section perpendicular to the axis of the cathode; and

FIGURE 2 is a section on the line A-B in FIGURE 1.

In these gures, 1 is the metallic magnetron body, usually made of copper, with the wave-guide ring 2, the coupling conductors or strappings 3, the resonators 4 and the cathode 5. The wave-guide ring 2 is interrupted by the transverse metallic partition 6. The input and output of the tube are formed by the wave-guides or

hollow conductors

7 and 8 and 7 and 8 respectively and the vacuum-

tight apertures

9 and 9. Wedges 10 and 11 serve in a known manner for constituting a su'iciently shock-free transition. The strappings 3 are produced by slots in the otherwise solid ring 12. The parting place within the resonator ring is formed by a solid body 13, with adjacent de-tuned cavities 14.

The magnet arrangements necessary for operating the tube are not represented in the drawing or described in the speciiication, since they are immaterial to the description of the invention, being structural elements of the magnetron that are known to the technologist.

The application of this invention is not restricted to wave lengths below 3 centimetres.

I claim:

1. A traveling Wave magnetron amplifier comprising an evacuated structure enclosing a cathode and an anode, the anode being arranged about the cathode to provide a circular interelectrode space, the anode having a plurality of resonators contiguous to the interelectrode space, electrons emitted by the cathode being caused to move in the interelectrode space, a waveguide surrounding the reso- 5 nators, the waveguide having signal input and output terminals formed by straight waveguide sections, the straight sections having a common metallic wall extending radially outwards from the inner circumferential wall of the waveguide, and means forming signal coupling paths from the waveguide to the resonators, the paths being of such length as to equalize the angular velocity of an electron Wave in the interelectrode space and an electromagnetic wave propagating through the waveguide.

2. A traveling wave magnetron amplifier comprising an evacuated structure enclosing a cathode and an anode, the anode being arranged about the cathode to provide a circular interelectrode space, the anode having a plurality of resonators contiguous to the interelectrode space, electrons emitted from the cathode being caused to move 0 in the interelectrode space, a main waveguide surrounding the resonators, the main waveguide having separate input and output ports, and means forming signal coupling paths from the main waveguide to the resonators, each path being formed by a waveguide section interconnecting the resonator and the main waveguide, and each section being an integral multiple of a quarter wave length at the signal frequency.

3. An amplier in accordance with claim 2 in which the waveguide section acts to match the impedance of the 30 main waveguide to that of the resonator.

References Cited in the tile of this patent UNITED STATES PATENTS OTHER REFERENCES Description and Operating Characteristics of the Platination, (Brown), Institution of Radio Engineers (Proceeding), 1957, pages 1209 to 1222 relied on.

Claims

1. A TRAVELING WAVE MAGNETRON AMPLIFIER COMPRISING AN EVACUATED STRUCTURE ENCLOSING A CATHODE AND AN ANODE, THE ANODE BEING ARRANGED ABOUT THE CATHODE TO PROVIDE A CIRCULAR INTERELECTRODE SPACE, THE ANODE HAVING A PLURALITY OF RESONATORS CONTIGUOUS TO THE INTERELECTRODE SPACE, ELECTRONS EMITTED BY THE CATHODE BEING CAUSED TO MOVE IN THE INTERELECTRODE SPACE, A WAVEGUIDE SURROUNDING THE RESONATORS, THE WAVEGUIDE HAVING SIGNAL INPUT AND OUTPUT TERMINALS FORMED BY STRAIGHT WAVEGUIDE SECTIONS, THE STRAIGHT SECTIONS HAVING A COMMON METALLIC WALL EXTENDING RADIALLY OUTWARDS FROM THE INNER CIRCUMFERENTIAL WALL OF THE WAVEGUIDE, AND MEANS FORMING SIGNAL COUPLING PATHS FROM THE WAVEGUIDE TO THE RESONATORS, THE PATHS BEING OF SUCH LENGTH AS TO EQUALIZE THE ANGULAR VELOCITY OF AN ELECTRON WAVE IN THE INTERELECTRODE SPACE AND AN ELECTROMAGNETIC WAVE PROPAGATING THROUGH THE WAVEGUIDE.