JPS5974705A - Double cavity - Google Patents

Abstract

PURPOSE:To select optionally an input coupling degree and to facilitate easy design and control of a tuner by constituting a cavity resonator with a double cavity and ensuring easily the tuning in a wide range of bands with the double cavity. CONSTITUTION:A cavity resonator is formed with an inside cavity 6 formed between a center conductor 4 and a cylindrical intermediate conductor 5 and an outside cavity 8 formed between the conductor 5 and a cylindrical external conductor 7. These cavities 6 and 8 are terminated by short circuit plates 9 and 10 respectively. The plates 9 and 10 can be moved independently of each other toward the axial direction of this double cavity for control of input impedance of both cavities 6 and 8. Furthermore both cavities 6 and 8 share the conductor 5, and the impedances of both cavities are connected in series via the conductor 5. Thus the input coupling degree can be selected optionally for this cavity resonator, and therefore both design and control are facilitated for a tuner.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cavity resonator, and more particularly to a cavity resonator having a double structure in order to widen the variable range of impedance.

As is well known, a cavity resonator is made up of an outer conductor and a center conductor that form a hollow cylinder, for example, and the distance l from the short-circuited end to the input end is changed to create an input bias, -dance. Adjust. In this case, tuning at low frequencies is difficult due to size reasons.

The purpose of the present invention is to solve the above-mentioned problems of the conventional cavity resonator, and also to make it possible to arbitrarily set the degree of input/output coupling when the cavity resonator is used in an output stage such as an oscillation circuit. The object of the present invention is to provide a cavity resonator that makes it possible.

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 cavity resonator according to the prior art.

The center conductor l and the cylindrical outer conductor 2 are short-terminated by a short circuit plate 3 at a distance l from the input end (left end in FIG. 1). Then, in order to change the distance l, the shorting plate 3
The position of is adjustable in the direction of the arrow.

When the line is lossless, the characteristic impedance is Z6, and the wave propagation constant is β, the input impedance Zg is given by equation (1) (where j is an imaginary unit).

Zs = j Zo-βl (1) In order to obtain high output (for example, IMN or higher) in the high frequency band,
The electron tube (not shown) naturally becomes larger, and as a result, the output capacity of the electron tube becomes smaller. Therefore, in order to reduce the inductance, it is necessary to reduce l, as seen from equation (1). In the high frequency band, l is about 10 cIL. Furthermore, since there is a structural upper limit to reducing 2°, it becomes difficult to design the circuit. I am keeping track of this.

λ -βE=-β(I!+-) ・・・・・・・・・(
2) However, even in this case, the circuit structure is unreasonable and there is a problem with stability.

On the other hand, in the case of low frequencies, the capy length l is 2
~3tn, which is extremely inconvenient to operate.

FIG. 2 is a conceptual cross-sectional view of an embodiment of a cavity resonator according to the present invention.

The cavity resonator is composed of an inner cavity 6 formed between the center conductor 4 and the cylindrical intermediate conductor 5, and an outer cavity 8 formed between the intermediate conductor 5 and the cylindrical outer conductor 7. (Hereinafter, the cavity resonator according to the present invention will be referred to as a double cavity.) The inner cavity 6 and the outer cavity 8 are terminated by shorting plates 9 and 10, respectively. -The above shorting plate 9,1
0 can be moved independently in the axial direction of the double cavity, and by moving the shorting plates 9 and 10, the input impedance of the inner cavity 6 and the outer cavity 8 can be adjusted. That is, the impedances entering the inner cavity 6 and the outer cavity 80 can be respectively set by functions of the same type as equation (1).

Since the inner cavity 6 and the outer cavity 8 share the intermediate conductor 5, their respective impedances are connected in series via the intermediate conductor 5.

Therefore, if the reactances of the inner cavity and outer cavity viewed from the input end are X, , X, the total impedance 2 is expressed by equation (3).

Z = j Xl + jL ・・・・・・・・・
(3) Here, Xl, X, is the shorting plate 9.10
In other words, by moving the position of the input end (second
It can be changed by the distance between A, B', C and the shorting plate 9.10 (left end of the figure) +1!1t.

For example, if Xl is capacitive reactance Xc and X is inductive reactance Xt, then 2 becomes equation (4).

Z = jXc −jXc ・・・・・・−・・・ (
4) Also, X, , X, are both inductive reactance XL1
, Xl2, Z becomes equation (5).

Z = jXt, 1 + jXt2・・・・・・・・・(
5) Figures 3, 4, and 5 show a tuning circuit and an output circuit, respectively, of the dual capacity according to the present invention.

This is an example in which it is used as part of an input circuit. In Figures 3 to 5, A, B, and C are the input terminals of the center conductor, intermediate conductor, and outer conductor in Figure 2, and the circuit element between A and 8 is the circuit between B and 6 in the inner cavity. The element represents the impedance of the outer cavity.

In the tuned circuit shown in Fig. 3, at high frequencies, the inner cavity 6 operates as a capacitive reactance (-jXc), and the outer cavity 8 operates as an inductive reactance (jXL
).

That is, the inner cavity 6 is operated in the (α+nλ/4) region (n: odd integer, α: small phase angle), and the outer cavity is operated in the inductive region, that is, the λ/4 region. Now, the inductive reactance required for tuning is +jXt,
The required impedance can be obtained by setting jXt, o=j XL -j XC. In this way, a circuit can be designed using an inductance XL larger than the required inductance XLO. Furthermore, at low frequencies, if the inner cavity 6 has an inductance XL1 and the outer cavity 8 has an inductance XL2, the necessary inductance XLO can be the sum of the two inductances from ξ.

jXLo = jXLl + jXbz...
... River... (Kasachini) The reactance of the inner cavity 6 and the outer cavity 8 is expressed by the same formula as equation (1), so by selecting an appropriate value for the characteristic impedance, the inner cavity 6 and the outer cavity 8 are In addition, the length of the coaxial cavity can be designed to an appropriate value in order to differentiate the characteristic impedance of the two.

When used as an output circuit or an input circuit as shown in FIGS. 4 and 5, the intermediate conductor 5 is drawn out as an intermediate terminal B. Since the inner cavity 6 and the outer cavity 8 are connected in series, by appropriately changing the ratio of the reactance Ll, L of the inner cavity 6 and the outer cavity 8, the output coupling can be achieved in the output circuit of FIG. In the input circuit of FIG. 5, the input coupling degree can be easily adjusted.

As explained above, the dual cavity of the present invention can be easily tuned over a wide band, and the degree of input/output coupling can be arbitrarily selected, making it extremely easy to design and adjust the tuner. becomes. That is, it is possible to avoid making the dimensions of the double cavity extremely large or small.

[Brief explanation of the drawing]

Figure 1 is a conceptual cross-sectional view of a conventional cavity resonator, Figure 2 is a conceptual cross-sectional view of a double cavity, Figure 3 is an example of its use as part of a resonant circuit, and Figure 4 is a conceptual cross-sectional view of a cavity resonator according to the prior art. is an example of use in an output circuit, and FIG. 5 is an example of use in an input circuit. 4... Center conductor, 5... Middle conductor, 6... Inner cavity 1 7... Outer conductor, 8... Outer cavity, 9.10...Short circuit board. @Figure 1

Claims (1)

[Claims] (11) It has a structure in which an intermediate conductor is provided inside the outer conductor, and a center conductor is disposed inside the intermediate conductor, and the center conductor and the intermediate conductor constitute an inner cavity. The intermediate conductor and the outer conductor constitute an outer cavity, and further, in order to terminate the inner cavity and the outer cavity, a shorting plate short-circuits the intermediate conductor and the center conductor, and a short circuit plate that short-circuits the intermediate conductor and the outer conductor. A double cavity in which a shorting plate that shorts the conductor is arranged so as to be movable independently in the axial direction of the cavity. (2) The center conductor, the intermediate conductor, and the outer conductor are concentric cylinders. The first claim characterized in that
Double capacity as described in section.