JPH10302655A - Coaxial magnetron - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coaxial magnetron wherein unstable operation such as moding does not take place and occupied band width is small, by enlarging QL without deteriorating a value of QL ratio Q (a load of an unnecessary mode at a certain frequency)/QL (a load of a resonance circuit determinating oscillation frequency of a magnetron)} of the unnecessary mode. SOLUTION: Grooves 12, 13 for tuning, whose width, depth and number are determined such that desired damping is imposed on a frequency of an unnecessary mode, are formed on conductive surfaces, which run along circumferences of attenuators for holding these, of the ring-shaped attenuators 5, 6 for unnecessary mode suppression for suppressing an unnecessary mode of a coaxial cavity provided in an external cavity 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coaxial magnetron, and more particularly to a coaxial magnetron in which the occupied bandwidth of a signal oscillated and output by the magnetron is reduced.

[0002]

2. Description of the Related Art FIG. 4 is a sectional view showing the structure of a conventional coaxial magnetron of this type. In the figure, 1 is a pole piece, 2 is a cathode, 3 is a vane, 4 is an external cavity coaxially provided in an internal cavity in which these are housed, 5 is a ring-shaped attenuator for unnecessary mode suppression on the outer peripheral side, and 6 is the same. Attenuator for suppressing unnecessary modes on the inner circumference side,
7 is a bellows, 8 is a ring-shaped tuning piston,
9 is an impedance transformer coupled to the outside of the external cavity 4, 10 is an output window coupled to the impedance transformer 9, 11 is a coupling slot attenuator, and 14 is an inner wall of the external cavity 4 and attenuators 5 and 6.
Is a gap provided between the tuning piston 8 and the end of the tuning piston 8.

The ring-shaped unnecessary mode suppressing attenuators 5 and 6 on the outer peripheral side and the inner peripheral side are attenuators for suppressing unnecessary modes in the coaxial cavity. The three surfaces of these attenuators 5 and 6 are metal surfaces of the tuning piston 8.
It is held in close contact with (conductive). The Q is damped by these attenuators 5 and 6 so as to suppress unnecessary modes of the external cavity 4 other than the operating frequency.

The degree of coupling with the outside is changed by an impedance transformer 9 to adjust the operating point as a magnetron. When the degree of coupling and beta, Q _L of resonant circuit for determining the oscillation frequency of the magnetron is expressed by the following equation.

[0005]

Namely, reducing the degree of coupling beta, the load Q _L is improved spread spectrum of the microwave oscillation increases magnetron, occupied bandwidth is reduced.

[0007] Since Q ₀ in the above equation does not change even by changing the degree of coupling, Q _L may be shifted to a larger value to reduce the degree of coupling beta. Increasing the Q _L will become possible to excite the microwave resonator circuit with improved selection of the frequency, the rise of the high voltage pulse to be applied to the magnetron, also in the frequency labile moiety falling portion, the frequency shift Is reduced.

[0008]

In the conventional coaxial magnetron constructed as described above, in order to reduce the occupied bandwidth, the impedance transformer as the output transformer is adjusted to reduce the degree of coupling and to operate. as you increase the Q _L of the frequency, the greater the direction of Q of unnecessary mode of a certain frequency, increasing moding and spurious, there is a problem that can not be increased only to a certain degree of Q _L.

[0009] The present invention has been made to solve the above problems, without degrading the value of Q _L ratio or unwanted mode Q / Q _L of unwanted modes, by increasing the Q _L, It is an object of the present invention to obtain a coaxial magnetron having a small occupied bandwidth without unstable operation such as moding.

[0010]

SUMMARY OF THE INVENTION In view of the foregoing, a first aspect of the present invention is a coaxial magnetron having a ring-shaped unnecessary mode suppressing attenuator for suppressing unnecessary modes of a coaxial cavity in an external cavity. And
A coaxial magnetron characterized in that at least one tuning groove is provided on a conductive surface along the circumference of the attenuator holding the attenuator for suppressing unnecessary modes.

According to a second aspect of the present invention, the width, depth and number of the tuning grooves are determined so that damping is applied to a frequency of a desired unnecessary mode. In the described coaxial magnetron.

According to a third aspect of the present invention, the width, depth, and number of the tuning grooves are determined so that damping is applied to two or more types of unnecessary mode frequencies. The coaxial magnetron according to claim 2, wherein

[0013]

FIG. 1 is a sectional view showing a configuration of a coaxial magnetron according to an embodiment of the present invention. In the drawing, 1 is a pole piece, 2 is a cathode, 3 is a vane, 4 is an external cavity provided coaxially with an internal cavity in which these are housed, 5 is a ring-shaped outer peripheral side unnecessary mode suppressing attenuator, 6 is an attenuator for suppressing unnecessary modes on the inner peripheral side, 7 is a bellows, 8 is a ring-shaped tuning piston, 9 is an impedance transformer coupled to the outside of the external cavity 4, 10 is an output window coupled to the impedance transformer 9, 11 is a coupling slot attenuator, and 14 is a gap provided between the inner wall of the external cavity 4 and the end of the tuning piston 8 provided with the attenuators 5 and 6.

In the coaxial magnetron according to the present invention,
Tuning grooves 12 and 13 are formed on the metal surface (conductive) of the tuning piston 8 that holds the outer and inner attenuators 5 and 6 along these ring-shaped attenuators 5 and 6, respectively. .

The Q of the conventional unnecessary mode can be reduced by adjusting the width and depth of the tuning grooves 12 and 13 and, if necessary, the number thereof so that the frequency of the unnecessary mode is damped. it can. By doing so, lower the Q of the unwanted mode which increases with the decreasing the degree of coupling by the impedance transformer 9, a coaxial magnetron can operate stably at and Q _L is large is obtained. Further, it is possible to reduce also the occupied bandwidth by increasing the Q _L.

[0016] Figure 2 is an illustration Q _L ratio (unnecessary mode Q / Q _L), Q _L as will be conventional represented by B is about 1
000 which Q _L ratio was over 1 at is a Q _L ratio until Q _L is 2000 as represented by A one of the present invention 1
It can be held below.

This will be described in more detail. The coaxial magnetron is designed so that the external cavity 4 is excited in the TE ₀₁₁ mode. However, the TM mode (TM ₀₁₁ , TM ₂₁₁ etc.) or the TE mode (TE ₁₂₁ , TE _121
211 , TE ₃₁₁ ...).

Since the TM mode is a mode in which a current flows through the end of the external cavity 4, a gap is provided at a portion indicated by 14 in FIG. On the other hand, in the TE mode, the dielectric attenuators, ie, the attenuators 5 and 6 inserted around the gap 14 are used.
Q is reduced by the loss due to Therefore TM mode,
In any of the TE modes, Q changes in a downward direction, and unnecessary waves are suppressed.

As shown in FIG. 3A, when the periphery of the attenuator 5 is a metal 8a as in the prior art, the electrical length of the attenuator 5 as viewed from the gap 14 is only the length La of FIG. On the other hand, as shown in FIG. 3 (b), when a tuning groove 12, that is, a space is provided in a part of the metal 8a as in the present invention, this can be a reflection surface. The electrical lengths are La and Lb.

The two electrical lengths are calculated as λg / 2 in the unnecessary mode.
By adjusting to the vicinity, damping can be effectively applied.

As described above, the tuning grooves 12 and 13 are provided in connection with the groove supporting the attenuator for suppressing the unnecessary mode, and the impedance matching of the attenuator in the unnecessary mode and frequency of the external cavity 4 is aimed at. The unnecessary mode can be effectively damped. Further, the provision of the tuning grooves 12 and 13 makes it possible to dampen several frequencies. By adjusting the width and length of the tuning grooves 12 and 13 and, if necessary, by adjusting the number of the tuning grooves 12 and 13, Damping can be effectively applied to more than one type of unnecessary mode.

[0022] In the impedance transformer 9 to adjust the degree of coupling β to the main frequency of the TM ₀₁₁ mode, when a large Q _L, Q _L or greater of other unwanted modes, those or smaller At present, it cannot be controlled. Therefore, when the main frequency _QL is increased, unnecessary modes that increase similarly are checked in advance, and the width and depth of the tuning grooves 12 and 13 are adjusted so that damping is applied to the unnecessary modes. Effectively.

[0023] Thus, it is possible to reduce the Q _L ratio (unnecessary mode Q / Q _L) as shown in FIG. 2, can be increased main Q _L without deteriorating the mode jumps and spurious unwanted mode. A larger Q _L, magnetron applied voltage, the rise of the current, the frequency shift amount at the time of falling is reduced can be obtained magnetron occupied bandwidth is small.

[0024]

As described above, according to the first aspect of the present invention, there is provided a coaxial magnetron provided with a ring-shaped unnecessary mode suppressing attenuator for suppressing unnecessary modes of a coaxial cavity in an external cavity. Since at least one tuning groove was provided on the conductive surface along the circumference of the attenuator that holds the attenuator,
Effectively damping by an attenuator with a tuning groove for unnecessary modes in which the Q increases at the same time as the main Q _L is increased, and by lowering the Q, suppresses the occurrence of moding and increases spurious. effects such that can provide less stable coaxial magnetron of occupied band by raising the Q _L is obtained.

According to the second aspect of the present invention, by adjusting the width, depth and number of the tuning grooves, it is possible to provide a coaxial magnetron capable of damping the frequency of a desired unnecessary mode. can get.

According to the third aspect of the present invention, it is possible to provide a coaxial magnetron capable of damping two or more kinds of unnecessary mode frequencies by adjusting the width, depth and number of tuning grooves. And the like.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of a coaxial magnetron according to an embodiment of the present invention.

Shows a comparison of FIG. 2 Q _L ratio (unnecessary mode Q / Q _L).

FIG. 3 is a diagram for explaining the effect of the tuning groove according to the present invention.

FIG. 4 is a cross-sectional view showing a configuration of a conventional coaxial magnetron.

[Explanation of symbols]

1 pole piece, 2 cathodes, 3 vanes, 4 external cavities, 5 attenuator for suppressing unnecessary modes on the outer circumference, 6 attenuator for suppressing unnecessary modes on the inner circumference, 7 bellows, 8 tuning piston, 9 impedance transformer, 10 output window, 11 coupling Slot attenuator, 12, 13 Tuning groove, 14 gaps.

Claims (3)

[Claims] 1. A coaxial magnetron provided with a ring-shaped unnecessary mode suppression attenuator for suppressing an unnecessary mode of a coaxial cavity in an external cavity, wherein the attenuator holds the unnecessary mode suppression attenuator along a circumference of the attenuator. A coaxial magnetron, wherein at least one tuning groove is provided on the conductive surface. 2. The coaxial magnetron according to claim 1, wherein the tuning groove has a width, a depth and a number determined so that damping is applied to a frequency of a desired unnecessary mode. 3. The tuning groove according to claim 2, wherein the tuning groove has a width, a depth, and a number determined so that damping is applied to frequencies of two or more kinds of unnecessary modes. Coaxial magnetron.