JPH0134401B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a bandpass wave device constructed by coupling a plurality of coaxial resonators using a dielectric material.

Recently, in order to miniaturize high frequency equipment, there is an extremely strong demand in the industrial world for miniaturization of the bandpass filters often used in such equipment. As one means for reducing the size of a filter, a method is known in which a filter is constructed by capacitively coupling a plurality of resonators using a low-loss dielectric material. FIG. 1 shows a conventional half-wavelength dielectric resonator. a is an axial cross-sectional view, b
is a sectional view taken along line A-A' of a. An outer conductor 10 is placed in a low-loss dielectric cylinder 103 made of ceramic or the like.
1. A unit resonator is constructed by providing an internal conductor 102. The outer conductor 101 is made of a dielectric cylinder 103 made of a highly conductive metal such as silver by baking or plating.
It may be formed around the outer periphery of the The internal conductor 102 may be created by fixing a metal cylinder inside the dielectric cylinder 103 with a conductive adhesive or the like.

A conventional filter constructed using this resonator is shown in FIG. 201 to 203 are the resonators of λg/2 shown in Fig. 1, and after placing and fixing them in a metal cylinder 204 as shown in the figure, input/output connectors 205 and 206 are attached to create a filter. . The input/output capacitance is formed in the gaps 211, 212 between parallel circular electrodes formed between the disks 209, 210 provided at the ends of the center conductors of the connectors 205, 206 and the center conductors of the resonator 201 or 203. . Further, the coupling between the resonators can be realized by the capacitance generated in the gaps 207 and 208 between the opposing center conductors of adjacent resonators.

In order to produce filters with good reproducibility, it is necessary to create input/output and interstage coupling capacitances with high precision. Among these, the input/output capacitance has a large capacitance value and is not impossible to adjust after assembly, but the inter-resonator coupling, that is, the inter-stage coupling, cannot be adjusted after assembly. Since the coupling capacitance between stages is determined by the arrangement between the resonators, that is, the geometric distance between the center conductors, it is necessary to position them by some means.

In the conventional structure shown in FIG. 2, there is no effective means for accurate placement or positioning of the resonator, and since the resonator resonates at the fundamental frequencies 2f ₀ and 3f ₀ , this frequency is It had the disadvantage that a pass band was formed at the center, and it did not have the high frequency suppression effect of a transmission filter.

The present invention has been made to eliminate the above-mentioned drawbacks, and aims to improve the harmonic suppression effect and realize accurate interstage coupling capacitance.

FIG. 3 shows an example of a resonator that is the basis of the configuration of the band-pass wave device of the present invention, which has already been proposed by the same applicant. In the figure, a shows a cross-sectional shape in the axial direction, and b shows a cross-section taken along line A-A' of a. This resonator is constructed by processing a cylindrical dielectric material 303 into a structure in which the outer periphery near both ends is reduced, the outer periphery is metallized to form an outer conductor 301, and an inner conductor 302 is further provided. By employing this resonator, it is possible to improve the high frequency suppression effect of the conventional filter structure described above. FIG. 4 shows a metal cylinder which is an important component of the present invention when a filter is constructed using a plurality of resonators shown in FIG. Here, a is the axial cross section, and b is the A of a.
It is a sectional view at -A'. This metal cylinder 40
1 is used for positioning and fixing the resonator. The inner diameter of the cylinder 401 is slightly larger than the outer diameter of the tip of the resonator shown in FIG. 3, and the outer diameter is approximately the same as the outer diameter of the center of the resonator. The metal cylinder 401 has a length l, and the tips of two resonators having the structure shown in FIG. 3 are inserted from both sides of the cylinder 401 and fixed with a conductive adhesive or the like. At this time, the length of the tip of the resonator must be 1/2 or less, and at this time, a total capacitance is formed between the center conductors of the two resonators inserted from both ends of the cylinder 401. If the length of the tip of the resonator and the length l of the metal cylinder are properly regulated, the distance between the center conductors of the two resonators can be regulated with precision, and the coupling capacitance can be realized with good reproducibility.

FIG. 5 shows an embodiment of the present invention.
In the figure, 501 to 503 are dielectric resonators having the structure shown in Fig. 3, 504 to 505 are metal cylinders having the shape shown in Fig. 4, 506 to 507 are metal cylinders to which input/output connectors are attached, and 508 is a filter. A cover to protect the outer periphery, which may be made of metal or plastic. 509-510 are input/output connectors,
511-512 are gaps between resonators, 513-
514 is a gap where an input/output coupling capacitance is formed.

Since the gaps 511 and 512 between the resonators can be accurately realized as described above, the coupling capacitance formed therein can also be accurately reproduced, and the characteristics of the filter are stabilized.

By the way, the filter shown in FIG. 5 has a cylindrical shape as a whole as shown in FIG. 6, and it may be difficult to fix the filter. 50 in figure
8 is a cover, and 509 is an input terminal. In such a case, instead of using the metal cylinder 401 shown in FIG. 4, the filter may be constructed using a resonator fixing metal 701 having a structure in which a cylinder is hollowed out within a square pillar as shown in FIG. By covering the outer periphery of the assembled filter with a rectangular tube 801 as shown in FIG. 8, and fixing the filter and cover, a filter that is easy to install can be realized.

In addition, if it is necessary to change the interstage coupling capacitance of the resonator, prepare a large number of metal disks 901 with the same shape as the cylindrical cross section of FIG. 4 with different thicknesses t, as shown in FIG. Then, the disk 901 is combined with the cylinder 401 shown in FIG. 4 or the rectangular cylinder 701 shown in FIG. 7,
This problem can be solved by realizing a fixing fitting with a length of equivalently l+t. In this example, this can be done only when the coupling capacitance is to be reduced; if the coupling capacitance is to be increased, the l of the cylinder 401 or the prism 701 must be cut short in advance.
Further, the cylinder 701 or the prism shown in FIG. 4 or 7 may be formed by combining a large number of metal disks 901 shown in FIG. 9 or metal thin plates having the cross-sectional shape shown in FIG. 7.

As described above, in the present invention, the outer diameter of the protruding regions near both open ends of the dielectric is made smaller than the outer diameter of the central region, and a stepped change is provided in the outer diameter of the dielectric, thereby giving a step-like change to the line impedance. , multiple resonators with a structure in which the high-order resonant frequency deviates from an integral multiple of the reference resonant frequency are used, and the stepped portions are fitted to the metal coupling means, thereby obtaining a harmonic suppression effect and achieving complete fixation. Its industrial value is extremely great, as it can play the role of positioning, and the characteristics of the bandpass waver can be extremely stabilized with a simple configuration.

[Brief explanation of drawings]

FIG. 1a is an axial cross-sectional view of a conventional coaxial dielectric resonator, FIG. 1b is a cross-sectional view taken along line A-A' of a, and FIG. FIG. 3a is an axial cross-sectional view of a dielectric resonator applied to the present invention, FIG. 3b is a cross-sectional view taken along line A-A' in a, and FIG. An axial sectional view of a metal cylinder that also serves as a resonator fixing device, FIG. 7a is an axial cross-sectional view of a resonator fixing fitting having a rectangular cross section, FIG. 7b is a cross-sectional view taken along line A-A', and FIG. A perspective view showing the structure of
FIG. 9a is an axial cross-sectional view of a metal disk for adjusting the interstage coupling of the filter, and FIG. 9b is a cross-sectional view of its structure. 501-503...dielectric resonator, 504,5
05...Metal cylinder for fixing the resonator, 511, 51
2...Gap where interstage coupling capacitance is formed, 50
9,510...Input/output connector.

Claims (1)

[Scope of Claims] 1. A central conductor is inserted into a hollow part of a dielectric, and the outer diameter of the protruding regions near both open ends of the dielectric is smaller than the outer diameter of the central region, so that the outer diameter of the dielectric has a step change. and a plurality of resonators having a structure in which a step-like change is given to the line impedance by forming an external conductor on the outer periphery of the dielectric material, and the higher-order resonance frequency deviates from an integral multiple of the reference resonance frequency; A cavity is provided, and the protruding regions of the resonators facing each other are fitted into both ends of the cavity, and a coupling capacitance is formed between the center conductors of both the resonators in the cavity. , and metal coupling means for positioning between the opposing resonators.