JPS59126302A - Dielectric filter - Google Patents

Abstract

PURPOSE:To obtain a dielectric filter which prevents deterioration in its out- band attenuation characteristics by providing unmetallized parts to the through- hole circumferential part and input/output terminal circumferential part of a dielectric block, and providing a metallized external conductor film entirely over the remaining surface. CONSTITUTION:The external conductor film 19 is metallized on the top surface of the block 11 and is connected to an external film 16. Parts 20 and 21 are unmetallized circumferential parts around through holes (resonance element) 12 and 13 on the top surface of the block 11. The external conductor film 19 is formed over the entire top surface of the block 11 except at unmetallized parts 20, 21, 22, and 23 to cover the surface of the block 11 almost entirely with the external conductor film 19 and external conductor film 16. Then, the external conductor films 16 and 19 themselves as a shield case.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to a dielectric filter, and more particularly to an improved structure for improving the external attenuation characteristics of the filter.

(2) Background of the Technology In general, dielectric filters have the advantages of being small, lightweight, and less affected by temperature changes, and are therefore widely used in various communication devices. In particular, dielectric filters are frequently used in portable radio devices called mobile radio devices and in-vehicle radio devices, as they require filters that are small, lightweight, and less susceptible to temperature changes.

This type of dielectric filter generally has a rectangular parallelepiped lightning arrester,
To provide a plurality of through-holes in the block, the inner surface of the through-hole for a resonant element is metalized to form a resonant hole (resonant element) having an internal conductor film, and the required amount of the block is The surface is metallized to form an external conductive film, and input/output terminals (exciter) are provided at both ends of the filter to form a band pass filter (BPF). There is. Then, input/output terminals and resonant elements,
The resonant elements are electromagnetically coupled to each other, each resonant element resonates in a predetermined band, and the band is output from the output terminal to an external circuit. In some cases, a part of the celadon magnetic field energy between the input terminal and the resonant element or between the resonant elements leaks to the outside of the dielectric material and couples with the output terminal, or when the electromagnetic field energy of the input terminal A portion of the filter may be directly coupled to the output terminal through space, and these phenomena adversely affect (deteriorate the characteristics) the attenuation characteristics outside the passband (attenuation characteristics in the attenuation band) of the filter. This tendency is particularly strong in small dielectric filters with a small number of resonant element stages because the distance between the input and output terminals is small.

Therefore, there is a need for a dielectric filter having a structure that can prevent such phenomena.

(3) Prior art and problems Figure 1 is a diagram for explaining a conventional dielectric filter, where (A) is a perspective view, (←) is (A) a plan view seen from the direction of arrow A in the figure, and C is a diagram for explaining a conventional dielectric filter. It is a side sectional view along the BB' line of a (b) figure. In the same figure, reference numeral 10 indicates a lightning arrester and body filter, 11 indicates a lightning arrester block, 12° and 13 indicate through holes formed in the plate 11, and 14° and 15 indicate input/output terminals (made of metal rods). (excitation body) are shown respectively. The dielectric film 11 has an external conductor film 16 (indicated by crosshatching in the figure) metallized by a method such as thick film firing on its side and bottom surfaces. Through hole 12
Inner conductor films 12a and 1'3a which are metalized in the same manner as described above are provided on the inner surface of each of ゜13.
2a and 13a are formed such that their lower ends are short-circuited to the external conductor film 16 and their upper ends are open. Therefore, the through hole 12.1
3 is the depth of the hole and the height of the internal conductor films 12a and 13a)
It is formed as a resonant element (resonant hole) that resonates at a frequency of 1/4 wavelength (λ/4). Input/output terminal 1
4.15 is fitted in a non-metalized hole 17.18 and serves as an exciter and is connected to an external circuit. In this way, a filter configured with a structure in which the top surface of the filter 11 is not metalized and is open and has a small number of stages (in this case, a two-stage configuration consisting of resonant elements 12 and 13) is provided with the input/output terminal 14. Since the distance between ゜15 and ゜15 becomes close, for example, if the symbol 14 is used as an input terminal, the terminal 14
There is a phenomenon in which a part of the electromagnetic field energy between the resonant element 12 and the resonant elements 12 and 13 leaks to the outside from the top surface of the block 11 and is coupled to the output terminal 15.
A phenomenon in which a part of the electromagnetic field energy of No. 4 is directly coupled to the output terminal 15 through space tends to occur. Due to these phenomena, there is a problem in that the out-of-band attenuation characteristics of conventional filters such as (4) Object of the Invention are deteriorated. By suppressing the leakage of electromagnetic field energy between the resonant element and the resonant element, and by suppressing the coupling of direct lightning and magnetic field energy between the input and output terminals, even in a small filter with a small number of stages, the filter An object of the present invention is to provide a dielectric filter that can prevent deterioration of out-of-band attenuation characteristics.

(5) Structure of the invention In order to achieve the objects of and, according to the present invention,
A plurality of through holes are formed at predetermined intervals along the longitudinal direction in a rectangular parallelepiped dielectric block, input/output terminals are provided at both ends of the block, and among the through holes, a through hole for a resonant element is formed; The surrounding area of either of the openings and the surrounding area of the input/output terminal on the surface of the block are formed as non-metallized parts, and the metal part of the block surface excluding these non-metallized parts and the through hole for the resonance element are formed. Provided is a dielectric filter characterized in that it is formed by metallizing the inner surface.

(6) Embodiments of the invention Hereinafter, embodiments of the invention will be described in detail based on the drawings.

FIGS. 2 to 4 are detailed illustrations of the present invention.

FIG. 2 is a diagram showing the first embodiment of the present invention, (A) is a perspective view, (←) is a plan view seen from the direction of arrow A in (A), and e is (←) B-B' in the figure. Side cross-section along the line, to) is (
FIG. 3 is a bottom view seen from the direction of arrow C in the figure. In the figure, reference numeral 20 indicates a dielectric filter. In this figure, the same parts or parts as those of the conventional example shown in FIG. 1 mentioned above are given the same reference numerals as in FIG. Therefore,
11 is a dielectric block, 12.13 is a through hole (resonant element), 12a, 13a are internal conductor films, 14.15 is an input/output terminal (exciter made of a metal bar), 16 is a professional, External conductor film formed on side and bottom surfaces, 17.18
1A and 1B respectively indicate holes that are not metalized, and since they are formed in the same manner as in FIG. 1, their explanation will be omitted. Now, reference numeral 19 indicates an external conductor film metallized on the upper surface of the plate 11, which is connected to the aforementioned external body film 16. Further, reference numerals 20 and 21 indicate non-metalized portions formed without metalizing the opening periphery of the through hole (resonant element) 12 and 13 on the upper surface of the block 11, respectively. Therefore, this non-metallized portion 20
21 is formed into a ring shape whose inner diameter is the diameter of the through hole 12.13. Similarly, reference numerals 22 and 23 indicate non-metalized portions formed around the input/output terminals 14 and 15 on the upper surface of the plate 11 without metallization. 1 In this first embodiment, the outer conductor film 19 is formed on the upper surface of the plate 11 excluding the non-metalized portions 20, 21, 22, and 23. The film 19 and the outer conductor film 16 cause the film 11 to
Most of the surface is coated. These outer conductor films 16 and 19 themselves are formed to also serve as a shield case. Therefore, this filter effectively suppresses leakage of the coupled electromagnetic field energy inside the filter 11 to the outside, and is formed as an extremely electrically stable filter. Therefore, by forming the filter in this way (7), even in a small filter with a small number of stages, the direct coupling of electromagnetic field energy between the input and output terminals is suppressed, and the deterioration of the filter's out-of-band attenuation characteristics is prevented. As a result, a filter with good out-of-band attenuation characteristics can be realized. Non-metalized part 20
．． The width of the non-metallized portion 20.21 may be very narrow, for example, if the width of the protrusion 11 is 11 m and the diameter of the through hole 12.13 is 3 mm, the width of the non-metallized portion 20.21 is It may be made to have an outer diameter of about 1 m and an outer diameter of about 5 mm.
Furthermore, this width may be formed to be approximately 0.11111%. However, as this width becomes very narrow, the frequency of the pass band tends to change.
There is no problem because it is easy to obtain a predetermined passband by adjusting the height of the passband. Next, with reference to FIG. 5, the attenuation characteristics of the embodiment will be explained.

FIG. 5 is a diagram showing the attenuation characteristic curve of the first embodiment of the present invention in contrast to the attenuation characteristic curve of the prior art example (FIG. 1). In the figure, the vertical axis is the attenuation amount (d
B), the horizontal axis shows the frequency (a), the curve E shown by a broken line shows the conventional example, and the curve MF shown by a solid line shows the attenuation characteristic curve of the first embodiment. As shown by curve E in the figure, in the conventional filter, due to the direct coupling of the electromagnetic field between the output terminals as described above, a certain level of transmission has already been made to the output terminal without passing through the resonant element. Therefore, it is difficult to expect attenuation beyond a certain level. On the other hand, as shown by curve F, the filter of this embodiment has been improved in this respect and exhibits extremely good attenuation characteristics.

FIG. 3 shows a second embodiment of the present invention, in which (A) is a perspective view, (B) is a top view seen from the direction of arrow A in FIG.
) is a bottom view seen from the direction of arrow C in figure (A). In the figure, numeral 30 indicates a dielectric filter, and all other numerals are the same as in the first embodiment (Fig. 2). The parts or the same parts are shown.Therefore, their explanations are omitted.This second embodiment has the same structure as the first embodiment in terms of the board.The only difference from the first embodiment is the following. The metallized portions 20 and 21 are arranged alternately on the upper and lower surfaces of the block 11, respectively.This second embodiment constructed as described above also provides the same characteristics as the first embodiment.

Although this second embodiment illustrated a filter with a two-stage configuration, for example, in the case of a filter with a four-stage configuration, the first and third
The first and fourth non-metallized parts are alternately arranged on the top surface of the block 11 and the second and fourth non-metalized parts on the bottom surface, and the first and second non-metalized parts are arranged on the top surface of the block 11, and the second and fourth non-metalized parts are arranged on the top surface of the block 11 and It is also possible to alternately arrange the third and fourth non-metallized portions on the bottom surface. Furthermore, in other multi-stage configuration filters, the non-metallized parts are also processed.

A combination of alternately disposed on the upper and lower surfaces of the ribs 11 can be used as a seclusion.

FIG. 4 is a side sectional view showing a third embodiment of the present invention.

In the same figure, the reference numeral 40 indicates a dielectric filter. Reference numerals 11 to 23 indicate the same parts or components as those in the first embodiment (FIG. 2). Therefore, these descriptions will be omitted. The basic configuration of this third embodiment is the same as that of the first embodiment. Now, in FIG. 4, numerals 24 and 25 indicate cylindrical hardware, which are arranged coaxially with the input/output terminals 14 and 15, respectively, and whose flange portions are fixed to the external conductor film 19. There is. Flexible metal tubes 26 and 27 are fitted into the cylindrical metal fittings 24 and 25, respectively, and the tubes 26 and 27 are filled with a resin material such as plastic and resin, and are arranged coaxially. Conductive wires 28 and 29 respectively connected to the input and output terminals 14 and 15 are arranged. As described above, in the third embodiment, an electromagnetic field shielding means is provided in the portion where the input/output terminal (exciter) 14.15 is exposed from the block 11, and the gap between the input/output terminals 14.15 is provided. This filter is formed to completely block direct electromagnetic field coupling and obtain even better out-of-band attenuation characteristics. The above embodiments are exemplified for the case of a 1/4 wavelength coaxial dielectric filter. However, the present invention can of course be applied to the lk wavelength coaxial dielectric filter in the same manner as in the above embodiment.

(11) As an example of the method for manufacturing the filter of the present invention, the outer surface of the block 11 and the inner surface of the through holes 12 and 130 are simultaneously metalized (however, the mounting holes 17 and 130 of the input/output terminals 14 and 15 are simultaneously metalized). There is a method of forming a conductive film (except for 18) and then scraping off the conductive film around the through holes 12 and 13 using, for example, a taper reamer. This method has the advantage of simplifying the filter manufacturing process.

It should be noted that the present invention is not limited to the above-mentioned embodiments, and for example, the following modifications can be implemented.

(a) The outer circumferential shape of the non-metalized part is a shape other than circular,
For example, it may be formed into a rectangular shape or the like.

(b) The input/output terminals 14 and 15 can be arranged at different positions from those in the above embodiment. For example, in FIG. 2, terminals 14 and 15 are connected to bu p.

The terminals 14 and 15 are arranged diagonally on the upper surface of the terminal 11.
one is placed on the top surface of the block 11 and the other is placed on the bottom surface, and the terminals 14 and 15 are placed on the side surface 11 of the block 11.
a (or the opposite side thereof), and it is also possible to arrange one of the terminals 14.15 on the side surface 11m and the other on the opposite side of the side surface 11m.

(7) Effects of the Invention As explained in detail above, the dielectric filter of the present invention provides non-metalized portions around the through holes (resonance holes) of the dielectric block and around the input/output terminals, By providing a metalized external conductor film on all other surfaces,
Even in the case of a small filter with a small number of stages, there is a great effect that the out-of-band attenuation characteristic can be improved with a simple structure.

[Brief explanation of drawings]

FIG. 1 is a perspective view, a top view, and a side sectional view of a conventional dielectric filter, and FIG. 2 is a perspective view, a top view, a side sectional view, and a bottom view of a first embodiment of the present invention. V1 FIG. 3 is a perspective view, top view, and bottom view of the second embodiment of the present invention, FIG. 4 is a side sectional view of the third embodiment of the present invention, and FIG. FIG. 3 is a diagram showing an out-of-band attenuation characteristic curve of one embodiment in comparison with a characteristic curve of a conventional example. E;...Conventional dielectric filter, 20.30.40.
...Dielectric filter according to the present invention, 11...Dielectric block, 11L...Side surface of block 11, 12.13
...Through hole (resonance hole, resonance element), 121L, 1
31L...Inner conductor film, 14.15...Input/output terminal (exciter), 16,19...Outer conductor film, 20.2
1゜22.23...Non-metalized part, 24.25.
...Tubular hardware with collar, 26.27...Flexible metal tube, 28.29...Conductive wire. Patent Applicant: Fujitsu Limited Patent Attorney: Akira Aoki, Patent Attorney: Kazuyuki Nishidate, Patent Attorney: 1) Yukio, Patent Attorney: Akira Yamaguchi (15) Figure 1. (c)

Claims (1)

[Claims] 1. A rectangular parallelepiped dielectric block is provided with a plurality of through holes at predetermined intervals along its longitudinal direction, input/output terminals are provided at both ends of the block, and Among them, the part of the through hole for the resonant element, the peripheral part of one of the openings on the surface and the peripheral part of the input/output terminal are formed as non-metallized parts, and these non-metalized parts are excluded,
A dielectric filter characterized in that the entire surface of the filter and the inner surface of the through hole for the resonant element are formed by metallizing. 2. All of the non-metallized portions around the opening of the resonant element through-hole are arranged and formed on one surface of the dielectric block including the opening. Dielectric filter. 3. The non-metalized portions around the opening of the resonant element through-hole are arranged alternately on one surface including the opening and the other surface of the dielectric block. The dielectric filter according to item 1. 4. The dielectric filter according to any one of claims 1 to 3, characterized in that the terminal for attendance is provided with an electromagnetic field tracing means.