JPH06140803A - Dielectric filter - Google Patents

Abstract

PURPOSE:To miniaturize the entire dielectric filter even in the case of constituting a multi-step filter, to facilitate the control of a band width and the adjustment of filter characteristics and to easily integrate the filter into a mounting substrate. CONSTITUTION:Plural 1/4 wavelength resonance strip line type dielectric resonators are longitudinally piled and integrated. Dielectric resonators 10a...10c are provided with internal electrodes 22 in the internally central lengthwise direction of a slip-shaped dielectric substrate 20 and external electrodes 24 at the outer peripheral parts excepting for one end face. The respective dielectric resonators are longitudinally piled through non-electrode parts 26 for coupling provided at the outer peripheral parts and integrated by arranging outside substrates 12a and 12b on both sides in their thickness-wise directions. Electrodes 42 are provided on the outside main surfaces of the outside substrates and at the outer peripheral parts. Further, independent island-shaped electrodes 14a and 14b are formed at the outer peripheral parts of dielectric resonators at both terminals and used as input/output coupling electrodes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure in which a plurality of dielectric resonators each having a 1/4 wavelength resonance type strip line are vertically stacked via electrode coupling portions so that their outer peripheral portions are in contact with each other. The present invention relates to a dielectric filter. This dielectric filter is suitable for various types of radio equipment for microwaves, for example.

[0002]

2. Description of the Related Art As a microwave filter, there is a type in which a resonator is composed of a strip line. For example, in the case of a quarter-wave resonator, a linear stripline resonator conductor is provided on a dielectric substrate, one end of which is open and the other end is short-circuited to an external electrode. Here, the resonator conductor is set to have a length that is an odd multiple of a quarter wavelength of the resonance wavelength.
When constructing an actual filter, a plurality of the above-mentioned resonator conductors are arranged on a dielectric substrate, the short-circuit side is commonly connected, and the distance between adjacent resonator conductors is a predetermined value that provides a coupling strength corresponding to the filter characteristics. Set to distance.

In such a stripline filter, the resonator conductors are arranged in a plane. For example, a conductive paste is attached in a predetermined shape on the dielectric substrate by screen printing, or the surface of the dielectric substrate is slightly recessed so that the electrode formation portion has a predetermined shape, and the conductive paste is placed inside thereof. To fill. After that, the dielectric substrate is heat-treated to bake the conductive paste to form a desired electrode pattern. As another example, there is also a tri-plate structure in which a thin conductive plate (resonator conductor) which is previously formed into a predetermined shape by punching or etching is sandwiched between two dielectric substrates.

[0004]

In any of these conventional stripline filters, the resonator conductors are arranged in a plane on the dielectric substrate, so that the area cannot be made very small. Particularly when the resonator conductors are connected in multiple stages to form a filter, the height dimension is inevitably large even if the height dimension is not increased. Further, since the resonator conductors are formed on the same dielectric substrate and the band of the filter is determined by the coupling state due to the spacing of the resonator conductors, it is possible to control the desired band especially when downsizing the filter. difficult.

Forming a resonator pattern by screen printing generally has poor printing accuracy and changes in frequency and coupling, so trimming is required. Further, when forming a concave portion on the dielectric substrate and filling the conductive material with the conductive material, the conductive material adheres to unnecessary portions as well, so that the conductive material must be removed and complicated work is required. Further, in the case of the triplate structure, the presence of the conductive plate causes a gap between the two dielectric substrates by the thickness of the conductive plate, so that the equivalent dielectric constant is lowered and the size cannot be reduced so much. In addition, it is necessary to take measures to shield the thickness of the conductive plate. When the dielectric substrates are superposed on each other, dimensional deviation easily occurs, and it is difficult to obtain desired characteristics.

The object of the present invention is the above-mentioned drawbacks of the prior art, that is, the problem of variations in electrode size due to screen printing, the difficulty of applying the conductive paste to the recesses, and the thickness of the conductive plate electrode in the triplate structure. Due to
Dielectric filter that can solve the dimensional deviation at the time of stacking, can be downsized even when configuring a multi-stage filter, can easily control the bandwidth and adjust the filter characteristics, and can be easily incorporated into the mounting board. Is to provide.

[0007]

SUMMARY OF THE INVENTION The present invention is basically
This is a dielectric filter of the type in which a plurality of / 4 wavelength resonance strip line type dielectric resonators are vertically stacked and integrated. Here, the dielectric resonator has a structure in which an internal electrode is formed in a central longitudinal direction of a strip-shaped dielectric substrate and an external electrode is formed on an outer peripheral portion excluding one end face. Then, a plurality of the dielectric resonators are vertically stacked via the coupling-free electrode portions provided on the outer peripheral portions thereof, and the outer substrates are arranged on both sides in the thickness direction thereof to be integrated. The outer substrate has electrodes on the outer main surface and the outer peripheral portion, and independent island electrodes are formed on the outer peripheral portions of the dielectric resonators located at both ends to serve as input / output coupling electrodes.

[0008] Adjacent dielectric resonators are coupled through the electrodeless portion for coupling formed on the outer peripheral surface of the dielectric resonator, and the degree of coupling and the filter characteristics depend on the size and formation position of these electrodeless portions. Adjust. In practice, it is preferable to provide an input / output electrode that is electrically connected to the island-shaped electrode of the dielectric resonator on one outer substrate and connect the input / output electrode to the circuit board. Normally, the open side of the dielectric resonator is
For example, it is covered with a shield such as a metal case, a metal plate, or a dielectric substrate coated with a conductor.

[0009]

Each dielectric resonator becomes a 1/4 wavelength resonance type strip line type resonator by the electrodes on the inner and outer peripheral surfaces. An electrode-free portion (one without an electrode) at one end of the outer peripheral surface is an open surface, and one with an electrode at the other end is a short-circuit surface. Coupling occurs between the adjacent dielectric resonators due to the coupling-free electrode portion existing on the joint surface between the dielectric resonators.

A plurality of the above-mentioned dielectric resonators are stacked vertically (in such a manner that their outer peripheral surfaces are in contact with each other).
As a result, a desired number of dielectric filters can be obtained. The filter characteristic is determined by the position and shape of the electrodeless portion for coupling between the adjacent dielectric resonators.

[0011]

1 is an exploded perspective view showing an embodiment of a dielectric filter according to the present invention, and FIG. 2 is an assembled perspective view thereof. This is the case with a three-stage filter. This dielectric filter is of a type in which three quarter-wave resonator stripline type dielectric resonators 10a, 10b, 10c are vertically stacked.
Further, the outer substrates 12a and 12b are arranged on the outside of them, and they are integrated by bonding with an adhesive or the like. Independent island electrodes 14a and 14b are provided on the outer peripheral portions of the dielectric resonators 10a and 10c located at both ends, and these are used as input / output coupling electrodes.

The all dielectric resonators 10a, ..., 10c basically have substantially the same shape, and the strip-shaped dielectric substrate 2 is used.
In this structure, the inner electrode 22 is formed in the inner central longitudinal direction of 0, and the outer electrode 24 is formed on the outer peripheral portion except one end face (the end face on the front side in FIG. 1). Here, the end surface on the electrodeless side is an open surface, and the end surface on the electrode formation side (the end surface on the back side in FIG. 1) is a short-circuit surface. Further, the dielectric resonators 10a and 10c at both ends are provided with island electrodes 14a and 14b. In this case, the dielectric resonators 10a and 10c are formed so as to be separated from the external electrodes in the outer peripheral portion near the open surface of the dielectric resonator and are respectively directed outward. (The dielectric resonators are not in contact with each other at the island electrodes). On the outer peripheral surfaces of the respective dielectric resonators which are in contact with each other, the electrodeless portions 26 for coupling are provided so as to correspond to each other.
To provide. In this embodiment, the external electrode is cut into a rectangular shape on the open surface side. Each dielectric resonator 1
.., 10c can finely adjust the resonance frequency or the input / output coupling by trimming the external electrode 24 or the island-shaped electrodes 14a, 14b.

The dielectric substrate is a sintered body of a high dielectric constant material for microwaves, which is usually used for a microwave filter, such as barium titanate. Dielectric resonator 10
The assembly of a, ..., 10c is formed, for example, by the method shown in FIGS. A sintered body substrate made of a high dielectric constant material for microwaves having a predetermined thickness and width is prepared. On the uppermost sintered substrate 30a, the silver paste 33 is applied to the entire lower surface, one end surface, and most of the upper surface that is continuous with the lower surface. Separately, the silver paste 34 is applied to the opposite end surface of the upper surface and applied in a strip shape. And then bake. The silver paste 34 is applied to the entire upper surface, one end surface, and most of the lower surface continuous to it (however, the end surface on the opposite side has a comb pattern) on the lower sintered substrate 30b and baked. The lower sintered body substrates 30c, 30d, 30e are the same as the sintered body substrate 30b. The lowermost sintered body substrate 30f is similar to the uppermost sintered body substrate 30a. Then, the entire upper surface of the sintered body substrate 30a and the entire lower surface of the sintered substrate 30b, the entire upper surface of the sintered body substrate 30c and the entire lower surface of the sintered substrate 30d, the entire upper surface of the sintered body substrate 30e and the sintered substrate 30f. The adhesive silver paste 35 is applied to the entire lower surface and bonded together, and baked and integrated. Further, as shown in FIG. 3B, the bonded sintered body substrates are bonded and integrated. Then, as shown in FIG. 3C, the dielectric resonator assembly shown in FIG. 1 is completed by cutting into a predetermined thickness.

Returning to FIG. 1, the outer substrates 12a and 12b.
The electrode 42 is formed on the outer main surface of the dielectric substrate 40 and the outer peripheral portion (excluding a part thereof). Here, on one of the outer substrates 12a, an input / output electrode 44 that is electrically connected to the island-shaped electrodes 14a and 14b of the dielectric resonators 10a and 10b.
The a and 44b are provided from the outer peripheral surface to the outer main surface to enable surface mounting on the circuit board. These outer substrates 12a and 12b do not necessarily have to be made of the same material as the dielectric resonator. For example, a material having a lower dielectric constant than a dielectric resonator such as forsterite may be used.

As described above, the dielectric resonators 10a, 10
b and 10c are arranged in the same direction, the outer substrates 14a and 14b are arranged on both sides, and they are integrated by using an adhesive or the like. In this embodiment, the conductor film 4 which is electrically connected to the external electrodes from both sides is also provided in each of the dielectric resonator joints on the open surface side.
6 is extended. In order to make the drawing easier to understand,
In each figure, the electrode forming portion is shaded, and the non-electrode portion (the portion where the base material of the dielectric is exposed) is shown with fine dots.

In this dielectric filter, when assembled, the island-shaped electrodes 14 of the dielectric resonators 10a and 10c.
a and 14b are electrodes 42 outside the outer substrates 12a and 12b.
It is needless to say that an electrodeless portion is formed in the vicinity so as not to be electrically connected to. Usually, such a dielectric filter has
It is mounted on a circuit board by covering it with a metal case and shielding it. Instead of the metal case, the open end face may be covered with a metal plate or a substrate coated with a conductive paste and baked. As a result, unnecessary coupling due to radio wave skipping between the input and output can be prevented, and deterioration of attenuation characteristics can be prevented.

The strip line type dielectric resonator as described above has a 1/1 size due to the internal electrodes formed in the dielectric substrate.
A four-wavelength resonator is formed, which is short-circuited at the external electrode. Therefore, the resonance wavelength (in other words, the resonance frequency) is basically determined by the length dimension (length of the internal electrode) of the dielectric resonator. Further, the larger the thickness (dimension in the stacking direction) of the dielectric resonator, the lower the resonance frequency, and the smaller the height (distance between the inner electrode and the outer electrode), the lower the resonance frequency. In each of the dielectric resonators, the coupling adjustment between the stages is performed depending on the position and area of the coupling-free electrode portions that are in contact with each other, whereby desired filter characteristics are exhibited. Therefore, various desired filter characteristics can be adjusted without changing the position of the island-shaped electrodes for input / output coupling. The input and output are coupled by the capacitance between the internal electrode of the dielectric resonator and the island electrode.

4 and 5 show the relationship between the position of the electrodeless portion for coupling and the filter characteristic. The way of coupling between the resonators (C coupling or L coupling) changes depending on the position where the electrodeless portion for coupling is formed, and the filter characteristics change. When the electrodeless portion 60 for coupling is provided on the open surface side of the dielectric resonator as shown in A of FIG. 4, the pole p appears on the low frequency side as shown in B. On the other hand, when the electrodeless portion 62 for coupling is provided on the short-circuit surface side of the dielectric resonator as shown in A of FIG. 5, the pole p appears on the high frequency side as shown in B. Both of these electrodeless portions 60 and 62 have a rectangular window shape, but may have any shape. In addition, the degree of coupling differs depending on the area of the electrodeless portion, and the larger the area, the stronger the coupling and the wider the band. As can be seen from the above, it is possible to realize the desired filter characteristics by adjusting the coupling between the dielectric resonators depending on the formation position and the area of the electrodeless portion for coupling.

Although both of the above embodiments are examples of a three-stage filter using three dielectric resonators, it goes without saying that the present invention can be applied to a multi-stage dielectric filter having two or four or more stages. The directions of the dielectric resonators do not necessarily have to be the same. The island electrodes may be arranged on both outer substrates.

[0020]

As described above, the present invention uses the strip line type dielectric resonator having a structure in which electrodes are formed inside and outside the dielectric substrate and short-circuited only at one end face. Therefore, this dielectric resonator is used. It is possible to fabricate a filter having a desired number of stages by closely stacking a plurality of the above through the electrodeless portion for coupling formed on the outer peripheral surface. As a result, the filter can be further downsized, and the occupied area can be reduced during mounting, which is advantageous for downsizing the device. By changing the position or area of the electrodeless portion for coupling formed on the outer peripheral surface of each dielectric resonator, the degree of coupling can be easily adjusted to control the bandwidth and the position of the pole can be determined.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing an embodiment of the present invention.

FIG. 2 is an assembled perspective view thereof.

FIG. 3 is an explanatory view showing a method for manufacturing a dielectric resonator used in the present invention.

FIG. 4 is an explanatory diagram showing a relationship between a formation position of an electrodeless portion for coupling and a filter characteristic.

FIG. 5 is an explanatory diagram showing a relationship between a formation position of an electrodeless portion for coupling and a filter characteristic.

[Explanation of symbols]

 10a, 10b, 10c Dielectric resonator 12a, 12b Outer substrate 14a, 14b Island electrode 20 Dielectric substrate 22 Internal electrode 24 External electrode 26 Electrode-free part for coupling

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical display location H01P 7/08 (72) Inventor Hisao Sato 5-3-11 Shimbashi, Minato-ku, Tokyo Fuji Electric Chemical Within the corporation

Claims (3)

[Claims] 1. A plurality of dielectric resonators in which a quarter-wave resonant strip line is configured by forming an internal electrode in the inner central longitudinal direction of a dielectric substrate and forming an external electrode on the outer peripheral portion excluding one end face. Are stacked vertically through electrodeless portions for coupling provided on their outer peripheral portions, and outer substrates are arranged on both sides in the thickness direction thereof to form an integrated structure. And a dielectric filter having electrodes on the outer peripheral portion, and independent island electrodes are formed on the outer peripheral portions of the dielectric resonators located at both ends to serve as input / output coupling electrodes. 2. An electrodeless portion for coupling is formed at a position closer to the open surface or a position closer to the short-circuited surface of the outer peripheral surface of the dielectric resonator, and the adjacent dielectric resonators are coupled via the electrodeless portion. Item 2. The dielectric filter according to item 1. 3. The input / output electrode that is electrically connected to the island-shaped electrode of the dielectric resonator is provided on one of the outer substrates, and the input / output electrode is connected to the circuit board. Dielectric filter.