JPH0591005U - Dielectric filter - Google Patents

Abstract

(57) [Abstract] [Purpose] To reduce and stabilize the capacitance formed by spacers and improve the stability of filter characteristics. [Structure] The dielectric coaxial resonators θ1 to θ3 are connected in series by connecting to a coupling substrate 7 to form a filter circuit. The combined substrate 7 is the case 1 via the spacers 8 and 9.
It is supported at a predetermined distance from 0. On the front and back surfaces of the spacers 8 and 9, strip-shaped electrodes 13 having a constant width dimension are formed so as to cross each other.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a dielectric filter in which a plurality of dielectric coaxial resonators are connected in series via a coupling substrate, and more particularly to a spacer interposed between the coupling substrate and the inner surface of the case.

[0002]

[Prior Art]

 FIG. 5 is a perspective view showing a structure of a conventional dielectric filter. The dielectric filter 20 shown in the figure is a quarter-wave insulator for a terminal short circuit in which a cylindrical dielectric 21 made of ceramics or the like is coated with a conductive member on the outer peripheral surface and the inner peripheral surface except one end surface. A filter unit in which coaxial resonators θ11, θ12, and θ13 are connected in series via a coupling substrate 22 is housed in a case 26. A plurality of electrodes d1 are formed on the front and back surfaces of the combined substrate 22, and a coupling capacitance is formed by the electrodes d1. The center conductors (conductive members covering the inner peripheral surface of the hole 21a) of the open ends of the dielectric coaxial resonators θ11 to θ13 are connected to the corresponding electrodes of the above-mentioned coupling substrate 22 via the coupling terminals T11 to T13. It is connected to d1.

Terminals 25 (terminals at one end are omitted) are connected to the lower portions of both ends of the combined substrate 22, and an insulating substrate is provided to support the combined substrate 22 at a predetermined distance from the case 26. Spacers 23, 24 made of one piece are attached. Electrodes d2 and d2 'shown in FIGS. 6 (a) and 6 (b) are formed on the front and back surfaces of the spacers 23 and 24, and the electrode d2 on the front surface and the terminals 25 and the electrodes on the back surface of the combined substrate 22 are The electrode d2 'on the back surface and the case 26 are connected by soldering or the like.

[0004]

[Problems to be solved by the device]

 In the conventional dielectric filter, the spacers 23 and 24 are provided at the mounting positions of the terminals 25 of the combined substrate 22 so as to support the combined substrate 22, so that the electrodes d2 and d2 'on the front and back surfaces of the spacers 23 and 24 can be used as shown in FIG. As shown in FIG. 7, a capacitance C e is formed between the input / output terminal and the ground, which adversely affects the filter characteristics. In particular, since the areas where the electrodes d2 and d2 'on the front and back surfaces of the spacers 23 and 24 overlap each other are large and the formed capacitance Ce is large, the spacers 23 and 24 have a great influence on the filter characteristics.

If the relative positions of the electrodes d2 on the front surface and the electrode d2 'on the back surface of the spacers 23 and 24 are different, the capacitance Ce changes, which deteriorates the stability of the filter characteristics. Has become.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a dielectric filter that reduces and stabilizes the capacitance formed by the spacer and has stable characteristics.

[0007]

[Means for Solving the Problems]

 In order to solve the above-mentioned problems, the present invention provides a spacer having a pair of electrodes formed on the front and back surfaces of an insulating substrate between a coupling substrate that cascade-connects a plurality of dielectric coaxial resonators and the inner surface of the case. In the provided dielectric filter, the electrodes on the front surface and the back surface of the insulating substrate are formed in a strip shape having a constant width dimension and are crossed with each other.

[0008]

[Action]

 According to the present invention, a plurality of dielectric coaxial resonators are connected in series via a coupling substrate, and thus a dielectric filter is constructed. The combined substrate is supported by a spacer at a predetermined distance from the inner surface of the case, and the filter characteristics are affected by the capacitance formed between the electrodes formed on the front and back surfaces of the spacer. The electrodes on the front surface and the back surface of the spacer are formed in a strip shape having a constant width dimension and are formed so as to intersect with each other, and the area formed by the overlapping portions of both electrodes is reduced, so that the capacitance formed by the spacer is reduced. And the effect on the filter characteristics is reduced. Further, even when the relative formation positions of the electrodes on the front and back surfaces are different, the area of the intersection of both electrodes does not change, and the capacitance formed by the spacer is stable. This improves the stability of filter characteristics.

[0009]

【Example】

 FIG. 1 is an exploded perspective view showing a structure of a dielectric filter according to the present invention. The dielectric filter 1 shown in the figure is a three-stage BPF in which the dielectric coaxial resonators θ1 to θ3 shown in FIG. 4 are connected in series by capacitors C2 and C3, and the input end and the output end are each an external coupling capacitor C1. , C4 to terminals 2 and 3.

The dielectric coaxial resonators θ1 to θ3 are quarter-wave coaxial resonators with short-circuited terminations, and are made of, for example, 2.5 mm square prismatic ceramics or the like with a hole 5 formed on the central axis. The outer peripheral surface of the body 4 excluding one end surface and the inner peripheral surface of the hole 5 are covered with a conductive member 6 (dotted portion) such as silver or copper.

The capacitors C2 and C3 are formed by electrodes D1, D2 and D3 which are formed on the surface of a rectangular dielectric substrate 7 by being coupled to each other. Further, electrodes are formed on the back surface of the combined substrate 7 at positions facing the electrodes D1 and D3, respectively, the capacitor C1 is formed by the electrode D1 and the back surface electrode, and the capacitor C4 is formed by the electrode D3 and the back surface electrode. Has been done. The coupling substrate 7 is arranged in front of the open end faces of the dielectric coaxial resonators θ1 to θ3, and the electrodes D1 to D3 formed on the surface of the coupling substrate 7 and the centers of the respective dielectric coaxial resonators θ1 to θ3. The conductor (the conductive member 6 in the hole 4) is connected to each of the coupling terminals T1 to T3. Further, a pair of spacers 8 and 9 are attached to the lower surfaces of both ends of the combined substrate 7 so as to support the combined substrate 7 at a predetermined distance from the side surface of the case 10 with the terminals 2 and 3 interposed. The filter unit of BPF1 is configured by this.

As shown in FIG. 2, the spacers 8 and 9 are strip-shaped electrodes 13 (surfaces) having a constant width dimension on the diagonals of the front and back surfaces of a rectangular insulating substrate 12 made of, for example, glass epoxy. Electrode) and the electrode 14 (back surface electrode) are formed so as to intersect with each other. It should be noted that the width L1 of the electrode 13 and the width L2 of the electrode 14 may be such that the areas of the portions 15 that intersect with each other at the time of forming the electrodes are constant, and, for example, at both ends where they do not intersect. It does not have to be a certain width. Further, the width dimension L1 and the width dimension L2 may be different.

Then, the filter unit is housed in a case 10, and a part of the lower side surface of the dielectric coaxial resonators θ 1 to θ 3 and the electrodes 14 on the back surfaces of the spacers 8 and 9 are attached to the case 10, for example, by soldering or the like. After the filter unit is fixed and grounded by connecting by, the cover 11 is covered and the BPF 1 is completed.

Since the spacers 8 and 9 are provided below the mounting positions of the terminals 2 and 3 of the combined substrate 7, the equivalent circuit of the BPF 1 is shown in FIG. 4 by the electrodes 13 and 14 on the front and back surfaces of the spacers 8 and 9. As shown by the dotted line, a capacitance Ce is formed between the input / output terminals 2 and 3 and the ground.

As described above, since the front surface electrode 13 and the back surface electrode 14 are formed in the band shape having the constant width dimensions L1 and L2 and are formed so as to intersect with each other, both electrodes 13, 14 intersect. Since the area of the portion 15 to be formed is small, the value of the capacitance Ce can be reduced. As a result, the influence of the capacitance Ce formed by the spacers 8 and 9 on the circuit of the BPF 1 is reduced.

Further, even when the relative forming positions of the front surface electrode 13 and the rear surface electrode 14 are different, the area of the portion 15 where the electrodes 13 and 14 intersect does not change, and the spacer 8 , 9, the size of the capacitance Ce formed is stable, which has the advantage of improving the stability of the filter characteristics of the BPF 1.

Note that the electrodes 13 and 14 formed on the spacers 8 and 9 are not limited to the above-mentioned shapes, and may be any electrodes in which strip-shaped electrodes having a certain width intersect. For example, as shown in FIG. 3 (a), linear strip electrodes 13 'and 14' may be formed so as to be diagonally crossed, and as shown in FIG. The strip-shaped electrode 13 ″ may be formed in the horizontal direction, and the electrode on the back surface may be the strip-shaped electrode 14 ″ formed in the long side direction.

Although the BPF has been described in the above embodiment, the present invention can be applied to any dielectric filter having a structure in which the coupling substrate is separated from the inner surface of the case by a spacer.

[0019]

[Effect of the device]

 As described above, according to the present invention, a strip-shaped electrode having a constant width dimension is formed on the front and back surfaces of a spacer that supports a coupling substrate that cascade-connects a plurality of dielectric coaxial resonators away from the inner surface of the case. Since the electrodes are formed so as to intersect with each other, the capacitance value formed in the spacer is reduced and the influence on the filter characteristics is reduced as the area of the intersecting portion of the electrodes on the front and back surfaces is reduced. In addition, the capacitance change due to the difference in relative forming positions of the electrodes on the front and back surfaces is small, and the stability of the filter characteristics of the dielectric filter is improved.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing a structure of a dielectric filter according to the present invention.

FIG. 2 is a diagram showing electrodes formed on the front and back surfaces of a spacer.

3A and 3B show another embodiment of the electrodes formed on the front and back surfaces of the spacer so as to intersect with each other. FIG. 3A is a diagram in which strip electrodes are formed on a diagonal line, and FIG. It is the figure which formed the electrode.

FIG. 4 is a diagram showing a circuit configuration of the dielectric filter (BPF).

FIG. 5 is a perspective view of an essential part showing the structure of a conventional dielectric filter.

6A and 6B show the shape of a spacer electrode applied to a conventional dielectric filter; FIG. 6A is a diagram showing an example in which the front surface electrode is smaller than the back surface electrode, and FIG. It is a figure which shows the example which made the electrode of the back surface substantially the same.

FIG. 7 is a diagram showing an equivalent circuit of a conventional dielectric filter.

[Explanation of symbols]

1 Dielectric Filter 2, 3 Terminal 4 Dielectric 5 Hole 6 Conductive Member 7 Combined Substrate 8, 9 Spacer 10 Case 11 Cover 12 Insulator Substrate 13, 14, 13 ', 14', 13 ", 14", D1
D3 electrodes C1 to C4 capacitors θ1 to θ3 dielectric coaxial resonators T1 to T3 coupling terminals

Claims (1)

[Scope of utility model registration request] 1. A dielectric filter in which a spacer having a pair of electrodes formed on the front and back surfaces of an insulating substrate is provided between a coupling substrate that cascade-connects a plurality of dielectric coaxial resonators and an inner surface of a case, wherein A dielectric filter, wherein the electrodes on the front and back surfaces of the body substrate are formed in a strip shape having a constant width dimension and are crossed with each other.