JPS61189001A - Inter-digital filter and its manufacture - Google Patents

Abstract

PURPOSE:To adjust easily a resonance frequency by forming a cutting part which has cut a conductive film of a dielectric block, in one outlet peripheral part (conductive film open end) positioned alternately at the opposite side of a columnar hole of the block. CONSTITUTION:Plural columnar holes 13 are formed in a block 12 of a ceramic dielectric having a high dielectric constant so that its axes become parallel lines to each other. Also, a conductive film 14 is provided on the whole block surface of the dielectric block 12 and the inner surface of each columnar hole 13 by using silver, copper plating, etc., and thereafter, the conductive film 14 of the block surface of the periphery of one outlet positioned alternately at the opposite side of each columnar hole 13 and the inner surface of the columnar hole 13 is cut by a rotary grindstone, an open end of the conductive film 14 is formed by providing a film removed part 15 on the periphery of one outlet and also resonance frequency adjusting use cutting parts S1, S2 are formed in the edge part (the surface of the block and the inner surface of the hole) of the film removed part 15, and the resonance frequency is set to a prescribed value.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an interdigital filter for radio equipment installed in automated vehicles, broadcasting satellites, etc., and a method for manufacturing the same.

(Summary of the Invention) The present invention provides an interdigital filter used in the microwave band, in which cut portions obtained by cutting a conductive coating of a dielectric block are connected to one outlet located alternately on the opposite side of the columnar holes of the block. It is formed on the peripheral portion (open end of the conductive film) to facilitate adjustment of the resonant frequency.

(Prior art) For car telephones, radio equipment for broadcasting satellites, etc., 800
A filter for frequencies around MHz to 1.5 GHz is required, but the filter currently used consists of a plurality of metal N3s mounted inside a case. That is, as shown in Figure 4 (showing the situation with the case lid included), the interdigital filter 1 is inserted into the case 2.
and a plurality of metal rods 3 attached to the case.

(Problems to be Solved by the Invention) By the way, in the conventional interdigital filter 1 shown in FIG. 4, the length of the metal rod 3 is required to be λ/4, where λ is the wavelength of a predetermined radio wave. Therefore, it can be small for relatively short wavelength (high frequency) radio waves, but it is large for long wavelength (low frequency) radio waves, making it unsuitable for mounting on moving objects. However, there were disadvantages in that it took a lot of effort to assemble and it was not easy to adjust the resonant frequency.

(Means for Solving the Problems) The present invention eliminates the drawbacks of the above-mentioned conventional interdigital filters, and provides a compact, lightweight, easy-to-manufacture filter for radio waves of various required frequencies, and adjustable resonant frequency. The present invention aims to provide an interdigital filter that is easy to use and a method for manufacturing the same.

The present invention can be applied to, for example, recently developed barium titanate (BaTiO3).
), etc., and ceramic dielectrics with high dielectric constants made of materials in which various metal oxides, etc. were added. Columnar holes are provided so that their axes are parallel to each other, and a conductive coating is provided on the entire block surface except for the block surface around one exit of each columnar hole and on the inner surface of each columnar hole. By alternating the exits on the side where the exit is not provided, and further by providing a cutting part for resonant frequency adjustment on either or both of the block surface around the one exit of the columnar hole and the inner surface of the columnar hole. , which solves the above-mentioned problems.

(Function) In the present invention, the resonant frequency can be easily adjusted by forming a cut portion around one exit of the columnar hole forming the open end of the conductive film. That is, as the conductive film is removed and the cut portion becomes larger, the resonance frequency becomes higher.

(Example) Hereinafter, an example of an interdigital filter and a manufacturing method thereof according to the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view of the embodiment, FIG. 2 is a plan sectional view of the embodiment, and FIG. 3 is an enlarged sectional view of the main part. In these figures, an interdigital filter 11 is a block (cuboid shape in this example) 12 of a ceramic dielectric material with a high dielectric constant.
A plurality of (six in this example) cylindrical holes 13 are provided in the
The axes are formed parallel to each other. After providing a conductive film 14 with silver, copper plating, etc. on the entire block surface of the dielectric block 12 and the inner surface of each cylindrical hole 13, one exit of each cylindrical hole 13 located alternately on the opposite side is formed. The conductive coating 14 on the surrounding block surface and the inner surface of the cylindrical hole 13 is cut with a rotating grinder, and a coating removal section 15 is provided around one exit to form an open end of the conductive coating 14. At the same time, as shown in FIG. 3, cut portions S 1 and S 2 for adjusting the resonance frequency are formed on the edges (block surface and hole inner surface) of the film removal portion 15 to set the resonance frequency to a predetermined value.

By using a ceramic dielectric with an extremely high dielectric constant as the dielectric block 12, the interdigital filter 11 of the above embodiment can be made small and lightweight even as a filter for frequencies in the vicinity of 800 MH2 to 1.5 GHz. . Also, the number of parts is small (
Only one dielectric block is required. ), easy to assemble. Furthermore, the part of the exit of one of the cylindrical holes 13 where the conductive coating is not formed can be easily processed by applying a rotary grindstone after plating the entire surface of the block 12 and the inner surface of each cylindrical hole 13. Now, at this time, the frequency adjustment cutting part 81. By forming S2, resonance frequency adjustment can also be performed. That is, the cutting part Sl,
By increasing S2, the resonant frequency of sharp frequency characteristics (for example, bump-pass characteristics) can be increased, and adjustment can be performed with high accuracy and satisfactorily. In particular, the cut portion S2 on the inner surface of the cylindrical hole 13 can significantly change the frequency. Further, by devising the structure of the rotating grindstone, it is possible to simultaneously process a plurality of cylindrical holes 13.

In the above embodiment, a dielectric block having a rectangular parallelepiped shape is exemplified, but the block may have an appropriate block shape such as a cylinder or a prism.

(Effects of the Invention) As explained above, according to the present invention, a dielectric material is formed into a block shape, a plurality of columnar holes are provided so that their axes are parallel to each other, and one of the columnar holes is formed. In a configuration in which a conductive coating is provided on the entire remaining block surface except for the block surface around the exit and the inner surface of each columnar hole, and the exits on which no conductive coating is provided are alternated, the area around the one exit of the columnar hole A resonant frequency adjustment cutout is formed on either or both of the block surface and the inner surface of the columnar hole, making it possible to create an interdigital system that is small, lightweight, low cost, and easy to adjust the resonant frequency. 2 filters can be obtained, which has an extremely excellent effect in reducing the size and weight of communication equipment such as car telephones.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an embodiment of the interdigital filter and its manufacturing method according to the present invention, FIG. FIG. 3 is a plan view of the internal structure of the digital filter. 1.11... Interdigital filter, 12...
- Dielectric block, 13... Cylindrical hole, 14... Conductive film, 15... Film removal part, Sl, S2... Cutting part for resonance frequency adjustment.

Claims (2)

[Claims] (1) A plurality of columnar holes are provided in a dielectric block so that their axes are parallel to each other, and the entire remaining block surface except the block surface around one exit of each columnar hole and the inner surface of each columnar hole An interdigital filter is provided with a conductive coating on the surface of the block, and the one outlet of adjacent columnar holes is arranged on the opposite side, the block surface around the one outlet of the columnar hole and the inner surface of the columnar hole. An interdigital filter characterized in that a cutting part for adjusting a resonance frequency is provided on one or both of the above. (2) After providing a conductive coating on the entire block surface and the inner surface of each columnar hole of a dielectric block in which a plurality of columnar holes are formed so that their axes are parallel to each other, the conductive coating is applied to each columnar hole alternately. The conductive coating on either or both of the block surface and the inner surface of the columnar hole near one exit located on the side is cut with a grindstone to form an open end of the conductive coating and a cutting part for adjusting the resonance frequency. A method for manufacturing an interdigital filter, characterized in that the interdigital filter is formed.