JP2007234343A - Microwave tube - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a microwave tube capable of improving frequency band characteristics and VSWR (voltage standing wave ratio) without increasing the length of an output wave guide tube 44 and the electric field strength generated in a high frequency window 46. <P>SOLUTION: In the output wave guide tube 44, a flat wave guide tube 41 and the standard wave guide tube 42 connected to an output void are used, and the high frequency window 46 is arranged between the standard wave guide tube 42 and the flat wave guide tube 41. A transmission characteristics correction element 48 is arranged in the flat wave guide tube 41. A reflected wave to cancel the reflected wave of the high frequency wave from the high frequency window 46 in the transmission characteristics correction element 48 is formed, and the transmission characteristics of the high frequency wave is corrected. Without increasing the length of the output wave guide tube 44 and the electric field strength generated in the high frequency window 46, the frequency band characteristics and VSWR (voltage standing wave ratio) are improved. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a microwave tube having a high-frequency output connected to an output cavity.

  Conventionally, as a microwave tube using a straight beam, there is a high-power klystron. This klystron has an electron gun unit that generates an electron beam, an input unit that inputs high-frequency power, a high-frequency interaction unit that amplifies high-frequency power by the interaction between the electron beam and a high-frequency electric field, and a high-frequency amplified from the high-frequency interaction unit. A klystron body having a high-frequency output unit for outputting electric power, a collector unit for capturing a used electron beam, and a focusing magnetic field device that is mounted around the klystron body and focuses the electron beam to a certain diameter. .

  Since the input unit is generally low power, a coaxial tube is generally used. However, when the output power is large and the frequency exceeds 700 MHz, the coaxial tube with a large diameter is cut off. Since it cannot be used in relation to the frequency, a high frequency is extracted from the output cavity by a rectangular waveguide instead of a coaxial tube, and a circle such as ceramic is placed in a circular waveguide connected in the middle of the rectangular waveguide. In many cases, a high-frequency window structure called a pill box type in which a plate-like dielectric is arranged to provide a secret structure is adopted.

  9 and 10 show a high-frequency output unit using a general pillbox-type high-frequency window structure, in which a circular waveguide 2 is connected in the middle of a pair of standard waveguides 1 having the same size. At the same time, a disk-shaped dielectric 3 such as ceramic having a small high-frequency loss is hermetically disposed in the circular waveguide 2 to form a high-frequency window 4. Both ends of the circular waveguide 2 are connected to the standard waveguide 1 by a connection plate 5 having good conductivity.

  By the way, when the frequency of the high frequency is low, it is necessary to attach a large waveguide to the output cavity of the klystron body, but it is necessary to provide a space through which the large waveguide penetrates in the focusing magnetic field device. There is an inconvenience that an electromagnet or the like that generates a magnetic field cannot be arranged, and the on-axis magnetic flux density at that location decreases. In order to reduce this, a so-called flat waveguide whose height direction is lower than that of a standard-sized standard waveguide is used as the waveguide connected to the output cavity.

  When such a flat waveguide is used, as shown in FIG. 11, after the flat waveguide 6 is converted to the standard waveguide 1 of the standard size by the step waveguide 7, it is moved to the high frequency window 4 side. It is common to connect, and the frequency band characteristic is also very excellent.

  However, in order to prevent the step waveguide 7 from causing the disturbance of the mode pattern, not only the length of the step waveguide 7 in the middle, but also the flat waveguide 6 and the standard waveguide 1 before and after, It is necessary to ensure a length of at least 0.25 wavelength in the guide wavelength, and when the step waveguide 7 is employed, there is a problem that the entire length of the waveguide portion becomes long.

  An improvement proposed in FIG. 12 is intended to compensate for this problem. Since the impedances of the flat waveguide 6 and the standard waveguide 1 are different, the dielectric 3 is guided in a circular waveguide to match the high-frequency window 4. The distance from the center of the tube 2 to the flat waveguide 6 is such that the distance from the surface of the dielectric 3 to the flat waveguide 6 is the distance from the surface of the dielectric 3 on the opposite side to the standard waveguide 1. Narrow. In this case, the instantaneous frequency band is narrower than the normal high frequency window 4. In addition to the problem that the instantaneous frequency band becomes narrow, the problem of the high-frequency window 4 is that the distance between the dielectric 3 installed in the circular waveguide 2 and the end face of the flat waveguide 6 is short. The strength of the electric field generated in the body 3 is increased, and the withstand power is reduced. Further, the change in the frequency characteristic of VSWR (voltage standing wave ratio) is large due to the axial displacement of the dielectric 3.

When a pair of rectangular standard waveguides of the same size as shown in FIGS. 9 and 10 is used, the dielectric of the high frequency window is directly seen from the output cavity side in the standard waveguide. There is a barrier member that cannot be used, and a cooling medium is allowed to flow inside the partition member. This is intended to suppress thermal damage to the dielectric and temperature rise of the waveguide. (For example, see Patent Document 1). That is, when a standard waveguide and a flat waveguide that is flatter than the standard waveguide and connected to the output cavity are used, problems such as frequency band characteristics are not considered.
JP-A-11-149876 (page 2-3, FIG. 1-2)

  As described above, in the case where the high-frequency window 4 is provided between the flat waveguide 6 and the standard waveguide 1, if the step waveguide 7 is employed, the total length of the waveguide portion becomes long, and the klystron If the position of the dielectric 3 in the high frequency window 4 is moved from the center of the circular waveguide 2 to the flat waveguide 6 side to prevent the deterioration of the VSWR, As the frequency band is narrowed, the electric field strength generated in the dielectric 3 is increased, and there is a problem that the power consumption is reduced.

  The present invention has been made in view of the above points, and without increasing the length of the output waveguide or increasing the electric field strength generated in the high-frequency window, the frequency band characteristics and VSWR (voltage standing wave ratio) are achieved. An object of the present invention is to provide a microwave tube capable of improving the above.

  The present invention is a microwave tube having a high-frequency output portion connected to an output cavity, the high-frequency output portion being a standard waveguide, flatter than the standard waveguide, and connected to the output cavity. A flat waveguide, an output waveguide having a high-frequency window disposed between the standard waveguide and the flat waveguide, and disposed in the flat waveguide, and from the high-frequency window in the flat waveguide And a transmission characteristic correction element that creates a reflected wave that cancels the reflected wave of high frequency.

  According to the present invention, even in the case of an output waveguide that uses a standard waveguide and a flat waveguide that is flatter than the standard waveguide and connected to the output cavity, the transmission arranged in the flat waveguide The characteristic correction element creates a reflected wave that cancels the high-frequency reflected wave from the high-frequency window and corrects the high-frequency transmission characteristics without increasing the length of the output waveguide or increasing the electric field strength generated in the high-frequency window. The frequency band characteristics and VSWR (voltage standing wave ratio) can be improved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  1 to 6 show a first embodiment.

  As shown in FIG. 3, a klystron 11 as a microwave tube includes a klystron main body 12 and a focusing magnetic field device 13.

  The klystron body 12 includes an electron gun unit 16 that generates an electron beam, a high-frequency interaction unit 17 that amplifies high-frequency power by the interaction between the electron beam and a high-frequency electric field, and an input unit 18 that inputs high-frequency power to the high-frequency interaction unit 17 The high-frequency output unit 19 that outputs the high-frequency power amplified by the high-frequency interaction unit 17 and the collector unit 20 that collects the used electron beam that has passed through the high-frequency interaction unit 17 are provided.

  The high-frequency interaction unit 17 includes a drift tube 21 through which an electron beam passes, an input cavity 22 to which an input unit 18 is connected, a plurality of intermediate cavities 23, and an output cavity 24 to which a high-frequency output unit 19 is connected. ing.

  The focusing magnetic field device 13 includes a main magnetic field generating unit 27 disposed around the high frequency interaction unit 17, and an electron gun unit side magnetic field (not shown) disposed around the electron gun unit 16 on one end side of the main magnetic field generating unit 27. A generator is provided. The main magnetic field generation unit 27 includes a main coil 28 disposed around the high frequency interaction unit 17 and an output coil 29 disposed outside the output cavity 24.

  As shown in FIGS. 1 to 3, the high-frequency output unit 19 includes a flat waveguide 41 connected to the output cavity 24, a standard waveguide 42 for extracting high-frequency waves, and the flat waveguide 41 and the standard waveguide. An output waveguide 44 is constituted by a circular waveguide 43 connected between the wave tube 42.

  The flat waveguide 41 and the standard waveguide 42 have a rectangular cross section, and the standard waveguide 42 has a standard size, whereas the flat waveguide 41 has a lower width in the height direction than the standard waveguide 42. It is formed in a flat size.

  In the center of the circular waveguide 43, a dielectric 45 formed in a disk shape with a ceramic or the like is hermetically arranged to form a high-frequency window 46. Flat waveguides are formed on both end faces of the circular waveguide 43. A highly conductive connection plate 47 to which 41 and the standard waveguide 42 are connected is hermetically arranged.

  The high-frequency window 46 to which the flat waveguide 41 and the standard waveguide 42 are connected generates a high-frequency reflected wave due to the difference in impedance, but the high-frequency reflected wave is canceled in the flat waveguide 41. A transmission characteristic correction element 48 that generates a reflected wave and corrects a high-frequency transmission characteristic is disposed. The transmission characteristic correction element 48 is a cylindrical shape having conductivity, and is oriented in a direction perpendicular to the flat surface of the flat waveguide 41 and in the width direction intersecting the flat direction of the flat waveguide 41. The two are spaced apart. Inside the cylindrical transmission characteristic correction element 48 is formed a cooling passage that can be thermally stabilized through a cooling medium such as cooling water by a cooling device (not shown).

  Even in the case of the output waveguide 44 using the standard waveguide 42 and the flat waveguide 41 that is flatter than the standard waveguide 42 and connected to the output cavity 24, The disposed transmission characteristic correction element 48 creates a reflected wave that cancels the high-frequency reflected wave from the high-frequency window 46, and corrects the high-frequency transmission characteristic. Therefore, the frequency band characteristic and VSWR (voltage standing wave ratio) can be improved.

  FIG. 4 shows the results of measuring the relationship between VSWR and high frequency. In the frequency band in the range of VSWR = 1.2, the transmission characteristic correction element 48 is used for the configuration B of the conventional example in which the dielectric 3 is eccentric in the circular waveguide 2 as shown in FIG. In the case of the configuration A of the present embodiment, a result that is 25% wider was obtained.

  FIG. 5 shows the result of measuring the relationship between the distance in the Y-axis direction and the X-axis direction from the center of the surface of the dielectric 45 and the electric field strength. In the case of the configuration A of the present embodiment, the electric field strength can be reduced by 15% or more compared to the configuration B of the conventional example.

  FIG. 6 shows a change in the center frequency when the dielectric 45 is displaced from the center of the circular waveguide 43. The change of the center frequency was suppressed to about half in the case of the configuration A of the present embodiment compared to the configuration B of the conventional example.

  Therefore, even in the case of the output waveguide 44 using the standard waveguide 42 and the flat waveguide 41 which is flatter than the standard waveguide 42 and connected to the output cavity 24, In order to correct a high-frequency transmission characteristic by creating a reflected wave that cancels a high-frequency reflected wave from the high-frequency window 46 by the arranged transmission characteristic correction element 48, the length of the output waveguide 44 is increased and the dielectric of the high-frequency window 46 The frequency band characteristics and VSWR (voltage standing wave ratio) can be improved without increasing the electric field strength generated in 45. Moreover, the change in the center frequency with respect to the shift of the dielectric 45 during assembly can be suppressed to about half.

  Next, FIGS. 7 and 8 show a second embodiment.

  A standing wave type high frequency wave in which a circular waveguide 43 having a large length L is provided between the flat waveguide 41 and the standard waveguide 42, and a dielectric 45 is disposed at substantially the center of the circular waveguide 43. The window structure is shown.

  Also in this case, the same effect as the first embodiment can be obtained by arranging the transmission characteristic correction element 48 in the flat waveguide 41.

  The transmission characteristic correcting element 48 can improve the transmission characteristic without any problem even at one place. Further, the transmission characteristic correction element 48 is not limited to a cylindrical shape, and may be a rectangular tube shape, or may be a polygonal column such as a column or a quadrangular column, an elliptical column, or the like, as long as it has good conductivity.

  Further, the microwave tube is not limited to the klystron 11, but may be a linear accelerator, a gyrator, a traveling wave tube, or the like.

It is a perspective view of the high frequency output part of the klystron which shows the 1st Embodiment of this invention. It is sectional drawing of a high frequency output part same as the above. It is sectional drawing of a klystron same as the above. It is a graph which shows the relationship between VSWR of a klystron same as the above, and the frequency of a high frequency. It is a graph which shows the relationship between the distance of the Y-axis direction and the X-axis direction from the center of the surface of the dielectric material of a klystron, and electric field strength. It is a graph which shows the change of the center frequency when the dielectric material of a klystron is shifted from the center of a circular waveguide. It is a perspective view of the high frequency output part of the klystron which shows the 2nd Embodiment of this invention. It is sectional drawing of a high frequency output part same as the above. It is a perspective view of the conventional high frequency output part. It is sectional drawing of the conventional high frequency output part. It is sectional drawing of the other conventional high frequency output part. It is sectional drawing of the other conventional high frequency output part.

Explanation of symbols

11 Klystron as a microwave tube
19 High frequency output section
24 output cavity
41 Flat waveguide
42 Standard waveguide
44 Output waveguide
46 high frequency window
48 Transmission characteristic correction element

Claims (3)

A microwave tube having a high frequency output connected to an output cavity,
The high-frequency output unit is
A standard waveguide, a flat waveguide that is flatter than the standard waveguide and connected to the output cavity, and an output waveguide having a high-frequency window disposed between the standard waveguide and the flat waveguide Tube,
A microwave tube, comprising: a transmission characteristic correcting element that is disposed in the flat waveguide and that generates a reflected wave that cancels a high-frequency reflected wave from a high-frequency window in the flat waveguide. The microwave tube according to claim 1, wherein the transmission characteristic correction elements are arranged at a plurality of locations in a direction intersecting a flat direction of the flat waveguide. The microwave tube according to claim 1 or 2, wherein the transmission characteristic correction element is formed in a cylindrical shape through which a cooling medium passes.

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