JPS61167201A - Interdigital filter - Google Patents

Abstract

PURPOSE:To obtain a small-sized interdigital filter with an excellent temperature characteristic by making plural holes having parallel axes to a block of a ceramic dielectric and providing a conductive film to a prescribed location. CONSTITUTION:Plural cylindrical holes 13 in parallel with each other are provided to a block form ceramic dielectric 12. The conductive film 14 is formed to the outer surface of the dielectric 12 and the inner face of the holes 13 by silver or copper plating. Further, a part 15 not formed with the conductive film is provided to the surface of the dielectric around one outlet of the holes 13 and the parts 15 adjacent to each other are arranged in opposite position to each other. Through the forming above, the small-sized interdigital filter with excellent temperature characteristic is obtained.

Description

Detailed Description of the Invention (3-1) Industrial Application Field The present invention relates to an interdigital filter for communication equipment such as automobiles and broadcasting satellites.

(3-2) Conventional technology: 3.
00 megahertz (MHz) to 130 gigahertz (GHz)
) is required, but the filter currently used consists of multiple metal rods installed inside a case. That is, as shown in FIG. 2 (showing the case with the lid removed), the interdigital filter 1 consists of a case 2 and a plurality of metal rods 3 attached to the case. This filter requires the length of the metal rod to be input/4 when the wavelength of the specified radio wave is input, so it can be small for relatively short wavelength (high frequency) radio waves. However, since it is large for radio waves with long wavelengths (low frequencies), it is not suitable for mounting on moving objects, takes time to assemble, and has poor temperature characteristics.

(+-3) Problems to be Solved by the Invention The present invention solves the above-mentioned drawbacks of the conventional interdigital filter, and provides 1. The objective is to provide an interdigital filter that is small, lightweight, and has good temperature characteristics.

(3-4) Means for solving the problem and its effect The present invention is based on the development of a ceramic dielectric material with a high dielectric constant made of, for example, barium titanate (BaTi03) and various metals added thereto. This method was developed by molding a dielectric material into a block shape, drilling multiple holes with parallel axes, and making the surface of the block and the inner surface of each hole conductive except for the area around the exit of one of the holes. The above-mentioned problem is solved by providing a coating and alternating the outlets without a coating.

The configuration of the present invention will be explained below based on the drawings of the embodiments. FIG. 1 [(a) is a perspective view, and (b) is a cross-sectional view of the Rollo cross section in FIG. In the figure, an interdigital filter 11 is a block-shaped (cuboid-shaped in this figure) ceramic dielectric 12.
multiple (six in this figure) cylindrical holes,
The hole 13 is formed by drilling a hole 13 whose axes are parallel to each other, and the outer surface of the dielectric 12 and the inner surface of the hole 13 are coated with a conductive coating 14 of silver, copper plating, or the like. Further, a portion 15 in which no conductive coating is formed is provided on the dielectric surface around one exit of each hole, and furthermore, this portion 15 of adjacent holes is arranged on opposite sides.

The interdigital filter according to the present invention described above is made of ceramic having an extremely high dielectric constant. Since a dielectric material is used, even a filter for frequencies close to 300 MHz to 1300 Hz can be made compact. In addition, the number of parts is small (only one dielectric is required), and assembly is easy. Holes can be easily processed by plating, etc., and the parts 15 on which no conductive film is formed can be processed after plating. Since it can be easily processed by using a grinder, the cost can be reduced. Furthermore, it has better temperature characteristics than the conventional filters mentioned above.

In the above embodiments, the shape of the dielectric body is a rectangular parallelepiped, but the shape is not necessarily limited to this, and may be any suitable block shape such as a cylinder or a prism.

(3-5) Effects of the Invention The present invention provides a block-shaped ceramic dielectric material with a plurality of mutually parallel cylindrical holes, and a conductive coating is applied to the block surface and the inner surface of the hole except around the exit of one of the holes. established,
By providing a portion without a conductive coating on the dielectric surface around the exit of one of the holes, and arranging the portions of adjacent holes in opposite directions, it is possible to create an interconnect that is small, low cost, and has good temperature characteristics. It has extremely excellent effects, such as making it possible to obtain a digital filter and making it possible to reduce the weight and size of electrical equipment such as car phones.

[Brief explanation of the drawing]

Fig. 1 is a diagram illustrating an interdigital filter according to the present invention, in which (a) is a perspective view, (b) is a cross-sectional view of the Ro-Ro cross section in Fig. (a), viewed in the direction of the arrow, and Fig. 2 is a conventional interdigital filter. It is a diagram showing a digital filter. lΦ・Fist Interdigital Filter 200. Case 300. Metal rod 11...Interdigital filter 12...Dielectric material 13, fist, hole 14, Φ, conductive film 15...part

Claims (1)

[Claims] A block of ceramic dielectric material with a high permittivity is provided with a plurality of approximately cylindrical holes whose axes are parallel to each other,
An interdigital filter comprising a conductive coating provided on the block surface except for the block surface around one exit of each hole and on the inner surface of the hole, and the one exit of adjacent holes is arranged on the opposite side.