JPS5990402A - Resonance frequency variable coaxial cavity for large power - Google Patents

Abstract

PURPOSE:To operate stably a cavity without causing a problem such as improper contact by rotating a feeding screw for moving a ring conductor so as to move the position of the termination, in the construction of a termination plate of a coaxial cavity used for large power. CONSTITUTION:A feeding screw 9 screwed to a ring conductor 8 and a driver 11 to rotate the feeding screw 9 via a gear 10 are provided in order to move a slide termination comprising a ring insulator 7 and the ring conductor 8. An outer cylindrical conductor 5 and an inner conductor 6 are terminated by the series coupling of a capacitor C1 formed by the outer cylindrical conductor 5 and the ring conductor 8 and a capacitor C2 formed by the ring conductor 8 and the inner conductor 6. Thus, the substantially same effect as a conventional short-circuit plate using a short-circuit conductor is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a resonant frequency variable coaxial cavity, and more particularly to the structure of a termination plate of a coaxial cavity used for high power applications.

The resonant frequency of a coaxial cavity depends on the length of the cavity. Using this, the resonant frequency of the capity is
Conventionally, adjustment has been carried out by changing the length of the capity. That is, for example, a desired resonance frequency can be obtained by combining a plurality of coaxial tubes of different lengths and a coaxial cavity whose ends are short-circuited, or a shorting plate that short-circuits the ends of the cavities can be moved in the axial direction of the cavity. The resonant frequency is adjusted by changing the position of the shorting plate.

In the former method, it is difficult to continuously change the frequency, and it takes a long time to install and remove the cavity, resulting in problems in workability.

In the latter method, the short circuit at the end of the cavity is the position where the tank current is at its maximum, so there is no risk of sparks or loss due to poor contact at the contact point between the end short circuit plate L and the coaxial pipe. This often occurs and can degrade the performance of the cavity.

It is an object of the present invention to solve the problems of the conventional coaxial cavity with variable vibration frequency.

The present invention will be described below with reference to the drawings.

FIG. 1 is a conceptual cross-sectional view of an example of a resonant frequency variable coaxial cavity with a movable end shorting plate according to the prior art, FIG. 2 is a conceptual cross-sectional view of an embodiment of a resonant frequency variable coaxial cavity according to the present invention, and FIG. is a sectional view taken along line A-A.

The prior art coaxial capity of FIG. 1 has an outer cylindrical conductor 1. Inner conductor 2. and an end shorting plate 3, which can be moved in the axial direction of the cavity by suitable means 4. The left ends P and Q of the outer cylindrical conductor 1 and the inner conductor 2 in the figure are the input ends of the capity, and the shorting plate 3 is moved to cause resonance to the input. In this case, as described above, if there is poor contact between the shorting plate 3 and the outer cylindrical conductor 1 or the inner conductor 2, a problem will occur in the operation of the cavity.

The present invention solves the above problem by short-circuiting the cavity at high frequency by capacitive coupling between the outer cylindrical conductor and the inner conductor without short-circuiting the cavity.

The coaxial cavity shown in FIGS. 2 and 3 showing an embodiment of the present invention includes an outer cylindrical conductor 5, an inner conductor 6, and a material such as Teflon that is in contact with the inner circumferential surface of the outer cylindrical conductor and the outer circumferential surface of the inner conductor. A ring-shaped insulator 7, a ring-shaped conductor 8 disposed opposite to the outer cylindrical conductor 5 and the inner conductor 6 via the insulator 7, and the above-mentioned insulator 7 and the above-mentioned insulator 7. a feed screw 9 that is screwed into the ring-shaped conductor 8 in order to move the slide end portion consisting of the ring-shaped conductor 8; and a drive device 1 that rotates the feed screw 9 via a gear 10.
Consists of 1.

In this structure, an outer cylindrical conductor 5 and an inner conductor 6 are terminated by a conode having a ring-shaped insulator 7 such as Teflon as a dielectric.

To explain in more detail, the tip/cell C1 formed by the outer cylindrical conductor 5 and the ring-shaped conductor 8 and the ring-shaped conductor 8
The outer cylindrical conductor 5 and the inner conductor 6 are terminated by series coupling of the capacitor C2 formed by the outer cylindrical conductor 5 and the inner conductor 6. FIG. 4 is an electrical equivalent circuit of the short circuit section. In the embodiments shown in FIGS. 2 and 3, the insulator 7 in contact with the outer cylindrical conductor 5 and the insulator 7 in contact with the inner conductor are integrally formed to cover the ring-shaped conductor 8. However, it is naturally possible to form these separately.

In this way, the outer cylindrical conductor 5 and the inner conductor 6 are terminated by the capacitors C1 and C.

It becomes electrically short-circuited at high frequencies, and can obtain substantially the same effect as the conventional shorting plate 3 using a 5-shorting conductor.

If the inner diameter of the outer cylindrical conductor is D2, and the outer diameter of the inner conductor is D2, the wave resistance W of the cylindrical coaxial cavity can be expressed by the following equation.

-2π If the wavelength of the electromagnetic wave is λ, its phase constant is β (-d), and the distance between the input end and the end of the cavity is θ, then the inopedance Z seen from the input end when the end is short-circuited is It is expressed by the following formula.

Z == W tanβe Here, if β is 135 times λ, then 4”
4 ′ 4 ′ janββ becomes infinite, and the cavity enters a resonant state. Normally, when the frequency is IOMH2 to 200MHz and the output power is 500 KW to 2MW, the value of W is selected to be between Ω and Ω.

Experimentally and theoretically, if the value of the reactance due to the electrostatic capacitance shown in Fig. 4 is set to 6 - the value of the wave resistance W, the outer cylindrical conductor 5 and the inner conductor 6 can be short-circuited at high frequencies. was confirmed.

For example, if the frequency is 5Q MHz, W is 50Q, D, =
l m, D2 = 0.606 m, the thickness d of Teflon is Q required for voltage resistance, 5 mm, the specific inductivity of Teflon is ε, = 2, and the width W of the slide conductor is 0.15 m. The capacitance c1 between the cylindrical conductor and the ring-shaped conductor, and the capacitance C2u between the ring-shaped conductor and the internal conductor have the following values.

c,: 0.0167 ttF, c2 = 0.
01 fi F Therefore, the composite reactance Xc becomes the following value.

Xc = 0.510, that is, the value of Xc is approximately 100 W. Due to the shunting reactance Xc, the outer cylindrical conductor 5 and the inner conductor 6 are substantially short-circuited at high frequencies.

Since the ring-shaped conductor 8 can be continuously moved from the outside by the feed screw 9, the gear 10, and the drive device 11, the position of the termination caused by the reactance can be moved. Unlike the terminal end, the metal part is mechanically non-contact, so problems such as poor contact do not occur, and the cavity can be operated stably.

[Brief explanation of the drawing]

FIG. 1 is a conceptual cross-sectional view of an example of a resonant frequency variable coaxial cavity with a movable termination plate according to the prior art, FIG. 2 is a conceptual cross-sectional view of an embodiment of a resonant frequency variable coaxial cavity according to the present invention, and FIG. The figure is a sectional view taken along the line AA, and FIG. 4 is an electrical equivalent circuit of the terminal end. 5...Outer cylindrical conductor, 6...Inner cylindrical conductor, 7...Insulator, 8...
Ring-shaped conductor, 9...Feed screw.

Claims (3)

[Claims] (1) An outer cylindrical conductor, an inner conductor, a ring-shaped conductor disposed on the outer cylindrical conductor and the inner conductor, and facing each other with an insulator in between, and a ring-shaped conductor that is screwed into the ring/g. A resonant frequency variable coaxial cavity for high power use, consisting of a mating feed screw, and capable of moving a nog-shaped conductor by rotating the feed screw. (2) The variable resonant frequency coaxial cavity for high power use according to claim (1), wherein the outer cylindrical conductor and the inner conductor form a coaxial cylindrical structure. (3) Claim No. (1) characterized in that the ring-shaped conductor is covered with the insulator described in (1) above.
Coaxial cavity with variable resonant frequency for high power as described in section.