JPH0580004U - Dielectric filter - Google Patents

Abstract

(57) [Summary] [Objective] The input / output capacitor can be easily connected without deteriorating the filter characteristic, and the overall structure including the dielectric resonator and the input / output coupling structure can be miniaturized. [Structure] A λ / 4 resonance type dielectric coaxial resonator having a plurality of resonator holes is used and coupled by an input / output capacitor 22. The dielectric resonator has a stepped structure in which notched step portions 16 are formed at both ends so that both of the resonator holes 12a and 12c located at the outermost ends are cut off. The input / output capacitor has a flat plate type structure having electrodes 24a and 24b on both sides. The input / output capacitor is connected so that the electrode 24a on one side thereof is connected to the conductor film of the resonator hole lacking the part.
The dielectric resonator is attached to the end surface 17 of the notch step portion, and the electrode 24b on the opposite surface of the input / output capacitor is used as an external connection portion.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention mainly relates to a dielectric filter used in the microwave band. More specifically, a λ / 4-resonance-type dielectric coaxial resonator is provided with notched steps reaching the resonator holes at both ends on the open surface side, and an input / output capacitor is provided at the end surface of the notched steps. The present invention relates to a dielectric filter having a structure in which it is mounted and coupled to the input and output. This filter is useful in various fields such as mobile communication and satellite communication.

[0002]

[Prior Art]

 A configuration using a λ / 4 resonance type dielectric coaxial resonator having a plurality of resonator holes as a dielectric filter is known. A dielectric resonator has, for example, a plurality of resonator holes and connector holes that are alternately arranged in the longitudinal direction of a rectangular parallelepiped dielectric block at a specified dimensional interval, and one of the surfaces on which they are open. Is an open surface, and a conductor film is formed on the outer surface excluding the open surface and the inner surface of the resonator hole to form an outer conductor and an inner conductor, respectively. The dielectric resonator is provided with an input / output coupling section consisting of resin terminals and input / output capacitors to form a filter. In this type of dielectric filter, the resonance frequency of each resonator is mainly determined by the length of the resonator hole. The resonators are properly coupled by the intervening coupler holes to produce the desired filter characteristics.

A resin terminal is one in which a lead pin is located at the center and the periphery thereof is covered with a synthetic resin. The resin terminals are inserted into the resonator holes located at both ends of the dielectric resonator, and are input / output coupled by the capacitance formed by the lead pin, the resin, and the conductor film of the resonator hole. Then, it is connected to an external circuit by a lead pin.

In the input / output capacitor system, an input / output capacitor is attached to the open end of the resonator hole located at the end of the dielectric coaxial resonator, and the capacitance is used for input / output coupling. To connect an input / output capacitor, insert a rivet-shaped metal terminal into the resonator hole at the outermost end, or provide a conductor pattern at the open end of the resonator hole at the outermost end. A flat plate type capacitor having electrodes on both surfaces is placed thereon, and the electrodes on the opposite surface are connected to the metal terminals or the conductor pattern by soldering or the like. Then attach a lead wire to the electrode on the opposite side to connect to the external circuit.

[0005]

[Problems to be solved by the device]

 Dielectric filters are required to be smaller and smaller in accordance with the miniaturization and weight reduction of various wireless devices incorporating them. Therefore, the inner diameter of the resonator hole becomes smaller and the distance between the resonator holes becomes narrower.

When the resonator hole is reduced to 0.8 to 0.7 mmφ or less, it becomes considerably difficult to manufacture a resin terminal to be inserted therein. Therefore, it becomes difficult to adopt the input / output coupling method using resin terminals, and this method is disadvantageous in downsizing the dielectric filter.

Although the coupling method using an input / output capacitor can be applied to miniaturization of the dielectric filter, in the conventional mounting structure, the capacitor is protruded from the dielectric block by the thickness of the rivet-shaped metal terminal flange, The height dimension becomes large, which is contrary to the intention of miniaturizing the dielectric block. In addition, in order to adjust the resonance frequency of each resonator, a stepped structure may be used in which the height of both ends of the dielectric resonator is reduced, but it is not always high enough to adjust the height of the entire resonator hole to a low value. It is not limited to have a step, and the upper surface of the input / output capacitor is more likely to project than the open surface of the dielectric block.

[0008] If the distance between the resonator holes is further reduced, the distance between the input and output capacitors mounted on the open surface is reduced and the lead wire is also pulled out in the same direction, especially when the number of stages is small. , The direct coupling (so-called “radio wave skip”) occurs between the input and output terminals, and the filter characteristic (particularly, the out-of-band attenuation amount) deteriorates.

The object of the present invention is to solve the above-mentioned drawbacks of the prior art, to easily connect an input / output capacitor without deteriorating the filter characteristics, and to include a dielectric resonator and an input / output coupling structure. Another object of the present invention is to provide a dielectric filter that can reduce the overall structure.

[0010]

[Means for Solving the Problems]

 The present invention is a dielectric filter having a structure in which a λ / 4 resonance type dielectric coaxial resonator having a plurality of resonator holes is used and coupled by an input / output capacitor. The dielectric resonator used in the present invention has a stepped structure in which a notched step portion is formed at both ends so that a part of both resonator holes located at the outermost end portion is not formed. The input / output capacitor has a flat plate structure with electrodes on both sides. Attach this input / output capacitor to the end face of the notched step of the dielectric resonator so that the electrode on one side of it is connected to the conductor film of the resonator hole where the above-mentioned part is missing. The surface electrode is used as an external connection portion.

A lead wire for connecting to an external circuit may be soldered to the external connection portion, or it may be a surface mounting type by devising the electrode shape and attachment position of the input / output capacitor. To make it a surface mount type, the input / output capacitor is L-shaped so that the electrode on the opposite surface covers one side of the input / output capacitor, and the input / output capacitor is dielectric with the electrode surface on that side. Attach it to the notch step so that one side of the body resonator is aligned.

[0012]

[Action]

 The dielectric resonator is coupled to an external circuit through the input / output capacitors provided in the notched steps on both end surfaces on the open surface side, and produces desired filter characteristics as a whole. The basic function of the input / output capacitor is the same as the conventional one, and it is coupled to the resonator located at the end by its capacitance. In the present invention, the input / output capacitor is located on the end face of the notch step, the input / output lead wires are pulled out in the opposite direction, and the input / output terminal spacing is widened. Direct coupling (radio wave skipping) is blocked and good filter characteristics are developed.

In the case of the surface mount type, the input / output terminals (electrode surface) are soldered in the same direction, but the dielectric filter is mounted on the circuit board and the side surface of the dielectric resonator (mounting on the board). Since the surface will be dropped to the ground, it will be shielded at that part. The electrodes on the opposite sides of the input and output capacitors (the electrodes not connected to the dielectric resonator) are located on the opposite sides of each other and the distance between them expands. The unnecessary direct binding of is less likely to occur.

[0014]

【Example】

 FIG. 1 is an exploded perspective view showing an embodiment of the dielectric filter according to the present invention, FIG. 2 is a vertical sectional view in its assembled state, and FIG. 3 is a partial plan view thereof. This is an example of a three-stage bandpass filter. As the dielectric resonator, a substantially rectangular parallelepiped dielectric block 10 made of a sintered body of a high dielectric constant material for microwaves is used. Three resonator holes 12a, 12b, 12c are formed at predetermined intervals in the longitudinal direction of the dielectric block 10 and a connector hole 14 is provided between them. Then, the notched step portion 16 is formed so that a part of the resonator holes 12a and 12c located at the outermost end portion is cut off, and the dielectric block 10 has a stepped structure. The outer surface of the dielectric block 10 excluding the open surface is defined as one of the open surfaces (the upper surface in FIGS. 1 and 2) of the resonator holes 12a, ... , 12c, a conductor film is formed on the inner surfaces of the resonator holes 12a, ..., 12c to form the outer conductor 18 and the inner conductor 20, respectively. In FIG. 1, the shaded portion is the surface on which the conductor film is provided, and the portion with fine dots indicates the surface where the conductor film is absent and the dielectric substrate is exposed. The conductor film is a layer of a thin conductive material formed by, for example, baking a silver paste.

An input / output capacitor 22 is mounted on the notched step portion 16 of the dielectric resonator. The input / output capacitor 22 has a flat plate type structure having electrodes 24a and 24b on both front and back surfaces. The input / output capacitor 22 is soldered to the end face 17 of the notch step portion 16 so that the electrode 24a on one side thereof is connected to the conductor film (inner conductor 20) of the resonator holes 12a and 12c, which are partially cut off. 26 (see FIG. 3) or the like, and the lead wire 28 is connected using the electrode 24b on the opposite surface as an external connection portion. The size of the input / output capacitor 22 is set to be slightly smaller than the height of the end surface 17 of the cutout step portion 16.

When the input / output capacitor 22 is mounted in the resonator holes at both ends of the dielectric resonator and coupled through it, the resonance frequency shifts to the low frequency side due to its capacitance. In the present invention, by forming the notch step portion 16, the resonance frequency of the resonators at both ends becomes relatively high, and the resonance frequency can be adjusted for each resonator of the dielectric resonator. Further, since the input / output capacitor 22 can be directly soldered to the conductor film (inner conductor 20) of the resonator holes 12a and 12c, which are partially cut off, it is not necessary to provide a metal terminal or a conductor pattern for attachment. . The capacitance required for I / O coupling is determined by the I / O capacitor installed. After assembly, the input / output capacitance can be adjusted by removing some of the electrodes of the input / output capacitor, if necessary. The lead wires 28 are pulled out in opposite directions (see FIG. 2).

FIG. 4 partially shows another embodiment of the present invention. Since the structure of the dielectric resonator is the same as that of the above-described embodiment, the corresponding parts are designated by the same reference numerals and the description thereof is omitted. In this embodiment, the electrode structure of the input / output capacitor 32 and its mounting position are changed so as to be compatible with surface mounting. The input / output capacitor 32 has an electrode 34a on one surface thereof, and the electrode 34b on the opposite surface is L-shaped so as to cover one side surface of the input / output capacitor. The input / output capacitor 32 is attached to the notch step portion 16 so that the electrode surface r on the side surface thereof and the one side surface s of the dielectric resonator are aligned with each other. In this case, the dielectric filter is a horizontal type and is directly mounted on the circuit board 40. The electrode surface r of the input / output capacitor 32 is soldered to be connected to an external circuit, and is connected to the ground at the side surface s of the dielectric resonator.

Although the embodiment of the present invention has been described in detail above, the present invention is not limited to the illustrated configuration. The number of resonator holes formed (the number of steps) is not limited to three, and can be applied to a filter having an arbitrary number of steps. It can also be applied to dielectric filters that do not have connector holes. In that case, a conductor pattern for coupling adjustment is formed on the open surface.

[0019]

[Effect of the device]

 According to the present invention, the notch step is formed at both ends of the dielectric resonator as described above, and the flat plate type input / output capacitor is connected to the conductor film of the resonator hole where the electrode on one side is partially cut off. Due to the mounting configuration, the entire unit can be made smaller, and even if it is made smaller, the input / output capacity can be easily taken out and adjustment work can be performed easily. In addition, since it becomes difficult for unnecessary direct coupling between the input and output terminals to occur, it is possible to prevent deterioration of the filter characteristics (especially the out-of-band attenuation amount).

[Brief description of drawings]

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

FIG. 2 is a vertical cross-sectional view of the dielectric filter of FIG. 1 in an assembled state.

FIG. 3 is a partial plan view of the dielectric filter of FIG.

FIG. 4 is a partial explanatory view showing another embodiment of the dielectric filter according to the present invention.

[Explanation of symbols]

 10 Dielectric Blocks 12a, 12b, 12c Resonator Holes 14 Connector Holes 16 Notch Steps 18 Outer Conductors 20 Inner Conductors 22 Input / Output Capacitors 24a, 24b Electrodes

Claims (2)

[Scope of utility model registration request] 1. A notch such that a part of the resonator hole located at the outermost end is cut off at both end faces on the open surface side of a λ / 4 resonance type dielectric coaxial resonator having a plurality of resonator holes. A flat type input / output capacitor having electrodes on both sides is formed by forming each of the stepped portions, and the electrode on one side is connected to the conductor film of the resonator hole lacking the part. A dielectric filter which is attached to an end surface of a cutout step portion and whose electrode on the opposite surface of the input / output capacitor serves as an external connection portion. 2. The input / output capacitor has an L-shape so that the electrode on the opposite surface covers one side surface of the input / output capacitor, and the input / output capacitor is connected to the electrode surface on one side surface and a dielectric resonator. The dielectric filter according to claim 1, wherein the dielectric filter is attached to a notched step portion so as to coincide with one side surface of the notch to be a surface mounting type.