JPH04167701A - Dielectric filter - Google Patents

Abstract

PURPOSE:To ensure the separation of input and output electrodes and to improve the filter characteristic by arranging coaxial resonators in a way that their open ends are directed in the opposite directions to each other. CONSTITUTION:An outer conductor and an inner conductor of a coaxial resonator 10(11) of one end open type are formed by coating a conductive material to an outer surface of a dielectric block 10b(11b) and an inner surface of a hole 10a(11a) and the coaxial resonators 10, 11 are arranged in a way that their open ends are directed in the opposite direction to each other. Thus, the distance between input and output electrodes 14a, 14b connected to the inner conductor of the coaxial resonators 10, 11 is widened. Thus, even when the size of the resonators is made small, the direct coupling between the input and output electrodes 14a, 14b is suppressed and an excellent filter characteristic is realized.

Description

[Detailed description of the invention] (b) Industrial application fields The present invention relates to a dielectric filter.

(B) Prior art Conventionally, a plurality of open-ended dielectric blocks each having an outer conductor and an inner conductor are formed by coating the outer surface of a dielectric block with one hole and the inner surface of the hole with a conductive material. Dielectric filters consisting of coaxial resonators are known (for example,
(See Japanese Patent Publication No. 62-42521).

Incidentally, in recent years, with the development of mobile communications, there has been a demand for the development of small and lightweight devices. Furthermore, in order to realize such a small and lightweight device, high-density mounting of components is required, and a shift to a surface-mounted type dielectric filter is also required.

A dielectric filter having the structure shown in FIG. 4 can be considered as a dielectric filter that solves this problem.

In FIG. 4, 1.2 is the outer surface of dielectric blocks 1b, 2b having holes 1a, 2a, respectively, and the holes 1a, 1.
b is an open-ended coaxial resonator in which an outer conductor and an inner conductor are formed by coating the inner surface with a conductive material; 3 is a part of the outer conductor of the coaxial resonator 1.2 or a dielectric block 1b; A concave portion formed by removing a part of the outer conductor including 2b so as to be parallel to the inner conductor, and 4 coupling electrodes 4a and 4b formed to couple with the inner axis of the coaxial resonator 1.2, respectively. This is a bonding board that is attached to the four parts 3 via an adhesive or the like.

(c) Problems to be Solved by the Invention According to the dielectric filter shown in FIG. 4 above, surface mounting is possible, but since the spacing between the coupling electrodes is narrow, direct coupling occurs between the coupling electrodes, resulting in filter characteristics. There is a risk of deterioration.

(d) Means for Solving the Problems In view of the above points, the present invention provides an outer conductor and An inner conductor is formed, and two conductors are arranged such that their open ends face in opposite directions.
A coaxial resonator with one end open, and a part of the outer conductor of this coaxial resonator or a part of the outer conductor including the dielectric block removed so as to be parallel to the inner conductor. The present invention is characterized in that it includes a notch and a coupling substrate having an input/output electrode formed at a position facing the notch to be coupled to the inner conductor of the coaxial resonator.

(E) Effect According to the present invention, since the coaxial resonators are arranged so that their open ends face in opposite directions, the distance between the input and output electrodes coupled to the inner conductor of the coaxial resonator increases.

(F) Embodiment FIG. 1 is a diagram showing an embodiment of the present invention. In FIG. 1, 10 and 11 are dielectric blocks 10b and 11 having one hole 1.0a and lla, respectively, and an outer conductor and an inner conductor are formed by coating the outer surface of the dielectric block 1.0a and the inner surface of the hole with a conductive material. It is an open-ended coaxial resonator with a dielectric constant of 38 (T]020S r, O, +Z ro,) and is arranged so that the open ends face in opposite directions.
The external shape is 3 mm square, and the resonator length is 4.8 mm.

12 and 13 are part of the outer conductor of coaxial resonator 10. An input electrode 14a and an output electrode 14 are respectively formed at positions facing the cutout 12.13 to be coupled to the inner conductor of the coaxial resonator 10.11.
This is a bonded substrate having a shape of 1.b and is made of alumina, and a ground conductor is provided on the back surface. 15 is a part of the outer conductor of the coaxial resonator l0111 or the dielectric block 10
Coupling between the coaxial resonators is achieved by joining the window portions 15 to each other using a window portion formed by removing a portion of the outer conductor including portions b and llb.

When the conventional resonator shown in FIG. 4 has the same external dimensions as the resonator of this embodiment, the distance between the input and output electrodes is 2.5 mm, whereas in the present invention, it can be increased to 3.8 mm. and can improve the direct coupling of inputs and outputs.

FIG. 2 shows the characteristics of the filter in FIG. 4 and the filter in FIG. 1, where the solid line shows the characteristics of the filter in FIG. It shows.

As is clear from FIG. 2, according to the present invention, the amount of attenuation outside the passband is larger than that of the conventional filter, and good filter characteristics can be exhibited.

FIG. 3 is a diagram showing another embodiment of the combined substrate, in which the input electrode 1
A ground electrode 14c is provided between the output electrode 4a and the output electrode 14b.

If the combined substrate shown in FIG. 3 is used, the input and output electrodes can be separated more reliably, and the filter characteristics can be improved.

In addition, if coaxial resonators are arranged so that their open ends face in opposite directions, and the modes of each resonator are different and the coupling between resonators is reduced, the shape of the window may be adjusted. You can adjust the degree of coupling by

Note that the present invention is not limited to this embodiment, and it is possible to change the dielectric material, external dimensions, etc.

(G) Effects of the Invention According to the present invention, an outer conductor and an inner conductor are formed by coating the outer surface of a dielectric block each having one hole and the inner surface of the hole with a conductive material, and the hole is opened. Two open-end coaxial resonators arranged such that their ends face in opposite directions, and a part of the outer conductor of the coaxial resonator or a part of the outer conductor including the dielectric block as an inner conductor. a cutout portion formed by removing the cutout portion so as to be parallel to the cutout portion;
Since a coupling board having input and output electrodes formed to be coupled to the inner conductor of the coaxial resonator is provided at a position facing this notch, even when the resonator shape is made small, the input and output electrodes can be connected to each other. direct coupling can be suppressed, and good filter characteristics can be obtained.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing filter characteristics, FIG. 3 is a diagram showing another example of a bonded substrate, and FIG. 4 is a diagram showing a conventional example. 10.11... Coaxial resonator, 12.13... Notch, 14... Combined substrate, 14a... Input electrode, 14b
...Output electrode, 15...Window part.

Claims (2)

[Claims] (1) An outer conductor and an inner conductor are formed by coating the outer surface of a dielectric block each having one hole and the inner surface of the hole with a conductive material, and the open ends are oriented in opposite directions. two open-ended coaxial resonators placed in the resonator, and a part of the outer conductor of the coaxial resonator or a part of the outer conductor including the dielectric block removed so that it is parallel to the inner conductor. A dielectric material comprising: a cutout portion formed as a cutout portion; and a coupling substrate having an input/output electrode formed to be coupled to an inner conductor of the coaxial resonator at a position facing the cutout portion. filter. (2) The coaxial resonator has a window formed by removing a part of the outer conductor, and the resonators are coupled by joining the window. 1. The dielectric filter according to 1.