JPH03184408A - Band-pass filter - Google Patents

Abstract

PURPOSE:To eliminate limitation on miniaturization, to stabilize filtering characteristic, and to respond to surface packaging by comprising the filter by forming a resonator by arranging resonator electrodes at both sides of a coupling control electrode, respectively, and embedding all the shield electrodes in a dielectric after arranging outside the resonator. CONSTITUTION:The band-pass filter 1 used in a high frequency area is comprised by arranging first and second resonator electrodes 3, 4 with the same constitution as that of the resonator of a conventional band-pass filter so as to form the resonators at both upper and lower plane sides of the coupling control electrode 2, respectively at the upper and lower plane sides of the coupling electrode 2 so as to be confornted with each other. A pair of shield electrodes 5, 6 are arranged at a position where those coupling control electrode and both resonators electrodes 3, 4 can be sandwiched from the outside in upper and lower directions. All those electrodes are arranged by embedding in the inside of the dielectric 7. Also, plural terminal electrodes 8a-8d are formed at the outer peripheral plane of the dielectric 7, and the draw-out electrodes of the resonators formed at both plane sides of the coupling control electrode 2, respectively are connected to the terminal electrodes 8a-8d, respectively.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a bandpass filter used in a high frequency region, and particularly to a bandpass filter in which a resonator electrode of a resonator constituting the bandpass filter is embedded in a dielectric. The present invention relates to a bandpass filter.

(Prior Art) Conventionally, as this type of bandpass filter, a configuration shown in FIG. 4 has been proposed.

The bandpass filter shown in FIG. 4 is constructed by arranging a pair of resonators 21 and 21 formed using dielectric substrates so as to face each other with a predetermined spatial distance a between them.

Resonator 21.2 that constitutes this bandpass filter
1 is a first resonator consisting of two capacitor electrodes 23.24 and a connecting electrode 25 connecting the capacitor electrodes 23.24 on one surface of a dielectric substrate 22, as shown in FIGS. 5 and 6, respectively. A device electrode 26 is provided, and 2 electrodes are provided on the other surfaces.
capacitor electrodes 27 and 28 and this capacitor electrode 2
7.28 is provided with a second resonator electrode 30 consisting of a connection electrode 29 that connects 7.28.

In the eleventh second resonator electrode 26.30, the capacitor electrode 23.24 and the capacitor electrode 27.28 respectively face each other with the dielectric substrate 22 in between, and the connection electrodes 25 and 29 respectively face the dielectric substrate 22. They are provided so as not to face each other via 22.

The resonators 21.21 are connected to respective capacitor electrodes 24.21.
Lead terminal 31.3 serving as an input/output terminal connected to 28
2. In a bandpass filter constructed by arranging a pair of resonators 21 and 21 so as to face each other, each of the connecting electrodes 25 and 29 functions as an inductor in a high frequency region, so that a bandpass filter as shown in FIG. It has an equivalent circuit. That is, each resonator 21.21 has a capacitor C1 formed between capacitor electrodes 23 and 27, and an inductor L1. L2 are connected respectively, and these capacitors CI and inductors Ll
, capacitor electrodes 24 and 28 in parallel in series circuit with L2.
The circuit configuration is such that the capacitor C2 formed between the
are combined by a coupling coefficient M.

Note that terminals a and b in the figure are lead terminals 31.
This corresponds to No. 32.

(Problems to be Solved by the Invention) In the conventional band-pass filter having the above configuration, if the pair of resonators 21 and 21 are brought too close to each other, the coupling becomes strong and it becomes impossible to obtain the desired filter characteristics. In this case, a predetermined spatial distance a is required between the resonators 21 and 21, which imposes restrictions on miniaturization.

Further, since no other members exist between the resonators 21 and 21, it is difficult to maintain the spatial distance a accurately, and the filter characteristics are likely to fluctuate.

Furthermore, since it is a type that requires lead terminals, it cannot be used for surface mounting, where it is attached directly to the surface of a wiring board.

SUMMARY OF THE INVENTION An object of the present invention is to provide a bandpass filter that has stable filter characteristics and is compatible with surface mounting without restrictions on miniaturization.

(Means for Solving the Problems) In order to achieve such an object, in the bandpass filter of the present invention, the first... The second resonator electrodes are arranged on both sides of the coupling control electrode so as to face each other, and a pair of shield electrodes are arranged so as to sandwich these electrodes from the outside. In a band-pass filter configured entirely embedded in a dielectric, both of the resonator electrodes each consist of two capacitor electrodes and a connection electrode that connects the two capacitor electrodes, and each of the capacitor electrodes faces each other. , and the respective connection electrodes are arranged so as not to face each other, and extraction electrodes connected to the respective resonators formed on both surfaces of the coupling control electrode by the two resonator electrodes are formed on the outer peripheral surface of the dielectric body. It is characterized by being connected to a plurality of terminal electrodes, respectively.

(Function) Since the coupling control electrode is interposed between the resonators, filter characteristics can be adjusted by adjusting the area of the coupling control electrode. That is, by increasing the area of the coupling control electrode, the magnetic coupling between the resonators is weakened, and by decreasing it, the magnetic coupling is strengthened. Therefore, by adjusting the area of the coupling control electrode so as to obtain predetermined filter characteristics, the resonators can be arranged in contact with each other by δ, so that the bandpass filter can be made smaller. In addition, since the resonator electrode and the coupling control electrode are buried within the dielectric, the positional relationship of each electrode is fixed, and the presence of the shield electrode blocks external influences, resulting in stable filter characteristics. become Furthermore, since terminal electrodes are formed on the outer peripheral surface of the dielectric, it is suitable for surface mounting.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings. FIG. 1 is a perspective view of a bandpass filter according to an embodiment of the present invention, FIG. 2 is a longitudinal sectional view thereof, and FIG. 3 is an exploded perspective view showing the internal structure.

As will be explained with reference to these figures, ■ is a band-pass filter, and this band-pass filter l is designed to form resonators on both upper and lower surfaces of the coupling control electrode 2 (prior art). The first one has the same configuration as described in
, second resonator electrodes 3.4 are arranged to face each other on both upper and lower surfaces of the coupling control electrode 2. A pair of shield electrodes 5 and 6 are arranged at positions sandwiching the coupling control electrode 2 and both resonator electrodes 3 and 4 from the outside in the vertical direction.

All of these electrodes are embedded inside the dielectric 7. Further, a plurality of terminal electrodes 8a to 8d are formed on the outer peripheral surface of the dielectric 7, and the resonator extraction electrodes formed on both surfaces of the coupling control electrode 2 are connected to the respective terminal electrodes 8a to 8d. It is connected.

The bandpass filter l having such a configuration is, for example, a third filter.
It is manufactured by the following procedure explained with reference to the drawings.

First, dielectric green sheet 7 made of ceramic material
3 to 71 are stacked in the order shown. The dielectric green sheets 7a, 7c, 7f, 7h, 7k, and 7m are plain and have no electrodes formed thereon. Dielectric green sheet 7b, l! A shield electrode 5.6 is formed on the upper surface of each. A first resonator electrode 3 is formed on the upper surface of each of the dielectric green sheets 7d and 74. The first resonator electrode 3 consists of two capacitor electrodes 9, 10 and a connecting electrode 11 that connects the two capacitor electrodes 9.degree.IO to each other, as in the prior art. One capacitor electrode 9 of the first resonator electrode 3
Extracting electrodes 12 are formed extending to the edges of the dielectric green sheets 7d and 7i.

A second resonator electrode 4 is formed on the upper surface of each of the dielectric green sheets 7e and 7j.

The second resonator electrode 4 similarly has two capacitor electrodes 13.
．． 14 and a connecting electrode 15 that connects both capacitor electrodes 13 and 14 to each other.

An extraction electrode I6 is formed on one capacitor electrode 13 of the second resonator electrode 4 and extends to the edges of the dielectric green channels 7e and 7j.

These two resonator electrodes 3.4 are capacitor electrodes 9°13;
10.14 are respectively dielectric green sheets 7e,
facing each other via 7j and connecting electrodes II,
15 is dielectric green sea) 7e.

They are arranged so as not to face each other via 7j, and form resonators on both surfaces of the coupling control electrode 2, respectively.

Further, a coupling control electrode 2 is formed on the upper surface of the dielectric green root 7g. The area of the coupling control electrode 2 is adjusted so that the bandpass filter 1 can obtain predetermined filter characteristics.

Note that the dielectric green sheet portion below the shield electrode 5 and the dielectric green sheet portion above the shield electrode 6 have a dielectric thickness of, for example, 20 mm after being fired.
The thickness is adjusted so that the weight is approximately 50μ. Usually, in order to obtain the predetermined thickness, a plurality of plain dielectric green sheets 7a and 7m are stacked.

In addition, the shield electrode 5 and the first resonator electrode 3 above it
The dielectric green sheet portion between the shield electrode 6 and the second resonator electrode 4 below the shield electrode 6 has a dielectric thickness of, for example, 1 after firing. The thickness is adjusted to about .0 to 1.5 em. Normally, a plurality of plain dielectric green sheets 7c and 7k are stacked to obtain a predetermined thickness.

Further, each dielectric green sheet portion between the first resonator electrode 3 and the second resonator electrode 4 on both upper and lower sides of the coupling IIJ control electrode has a dielectric thickness of, for example, 20 mm after firing them. The thickness is adjusted to approximately 50μ. Although not shown in the drawings, a plurality of plain dielectric green sheets are usually stacked between the dielectric green sheets 7d and 70 and between the dielectric green sheets 71 and 7j in order to obtain the predetermined thickness.

Further, a dielectric green sheet portion between the coupling control electrode 2 and the second resonator electrode 4 below it, and a dielectric green sheet portion between the coupling control electrode 2 and the first resonator electrode 3 above it. The thickness of the sheet portion is adjusted so that the thickness of the dielectric material after firing the sheet portion is, for example, about 70 to 80 μm. Normally, a plurality of plain dielectric green sheets 7f and 7h are stacked to obtain a predetermined thickness.

Next, the dielectric green sheets 7a to 7m stacked as described above are pressed from above and below and fired at a predetermined temperature, thereby forming each dielectric green sheet 7a.
-7I11 are integrated to obtain the dielectric body 7 (see FIGS. 1 and 2) in which the respective electrodes are embedded. The outer circumferential surface of the dielectric 7 thus obtained has the first. Second
The end faces of the four extraction electrodes 12.16 connected to the respective resonators formed by the resonator electrodes 3.4 are exposed.

Next, terminal electrodes 8a to 8d are connected to the four exposed extraction electrodes 12.16 on the outer peripheral surface of the dielectric 7.
(See Figure 1). Thereby, a bandpass filter l is obtained.

Note that the method for obtaining the bandpass filter l is not limited to the method of stacking dielectric green sheets in order as described above, but also methods such as printing dielectric paste and electrode paste in a predetermined order and stacking them. It may be a method.

Furthermore, although the bandpass filter in the above embodiment consists of a pair of resonators facing each other, three resonators are used.
It is also possible to use more than one resonator, in which case a coupling control electrode may be interposed between the respective resonators facing each other.

(Effects of the Invention) As is clear from the above explanation, according to the present invention,
The presence of coupling control electrodes between the resonators allows the resonators to be placed close to each other, resulting in miniaturization. Further, since the structure is such that the resonator electrode and the coupling control electrode are embedded in the dielectric body, and the shield electrode is present, the filter characteristics are stable. Furthermore, since the structure has terminal electrodes formed on the outer peripheral surface of the dielectric, it is suitable for surface mounting.

[Brief explanation of drawings]

FIG. 11 is a perspective view of a bandpass filter according to an embodiment of the present invention, FIG. 2 is a longitudinal sectional view thereof, and FIG. 3 is an exploded perspective view showing its internal structure. FIG. 4 is a perspective view of a conventional band-pass filter, FIGS. 5 and 6 are plan views showing one side and the other side of a resonator constituting the band-pass filter, and FIG. 7 is a perspective view of a band-pass filter. It is an equivalent circuit diagram. G...Band pass filter, 2...Coupling control electrode, 3
...first resonator electrode, 4...second resonator electrode,
5.6... Shield electrode, 7... Dielectric material, 7a-7
I11...Dielectric green sheet, 8a to 8d...
Terminal electrode, 9.10, 13.14... Capacitor electrode, 11, 15... Connection electrode, 12.16... Extraction electrode.

Claims (1)

[Claims] (1) First and second resonator electrodes are arranged so as to face each other on both sides of the coupling control electrode so as to form resonators on both sides of the coupling control electrode, and these electrodes are In a bandpass filter constructed by arranging a pair of shield electrodes at positions sandwiching them from the outside and embedding these electrodes in a dielectric, both of the resonator electrodes are connected to two capacitor electrodes and the corresponding electrodes. It consists of a connection electrode that connects both capacitor electrodes, and is arranged so that each capacitor electrode faces each other and each connection electrode does not face each other, and is formed on both sides of a coupling control electrode by both resonator electrodes. A bandpass filter characterized in that extraction electrodes connected to each resonator are connected to a plurality of terminal electrodes formed on an outer peripheral surface of the dielectric.