JP2616070B2 - Bandpass filter - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a band-pass filter used in a high-frequency region, and more particularly, to a band-pass filter in which a resonator electrode of a resonator constituting the band-pass filter is embedded in a dielectric. A bandpass filter.

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

The bandpass filter shown in FIG. 4 is configured by arranging a pair of resonators 21 and 21 formed using a dielectric substrate so as to face each other with a predetermined space distance a.

Resonators 21 and 21 constituting this bandpass filter
Is a dielectric substrate 22 as shown in FIGS. 5 and 6, respectively.
A first resonator electrode 26 comprising two capacitor electrodes 23 and 24 and a connection electrode 25 connecting the capacitor electrodes 23 and 24 is provided on one surface, and two capacitor electrodes 27 and 28 are similarly provided on the other surface. Connection electrode for connecting these capacitor electrodes 27 and 28
29, and is provided with a second resonator electrode 30 consisting of

In the first and second resonator electrodes 26 and 30, the capacitor electrodes 23 and 24 and the capacitor electrodes 27 and 28 respectively oppose each other via the dielectric substrate 22, and the connection electrodes 25 and 29 are respectively They are provided so as not to face each other with the substrate 22 interposed therebetween.

The resonators 21, 21 have lead terminals 31, 32 serving as input / output terminals connected to the respective capacitor electrodes 24, 28. Such a band-pass filter in which the pair of resonators 21 and 21 are arranged so as to face each other has a structure as shown in FIG. 7 because the connection electrodes 25 and 29 each function as an inductor in a high-frequency region. It has an equivalent circuit. That is, the resonators 21 and 21 are respectively connected to the capacitor electrode 2
A capacitor C1 is formed between 3 and 27, and an inductor L1, formed by connecting electrodes 25 and 29 at both ends of the capacitor C1,
L2 are connected respectively, and capacitor electrodes 24 and 28 are connected in parallel with a series circuit of these capacitors C1 and inductors L1 and L2.
And a capacitor C2 formed between the resonators 21 and 21, and the inductors L1 and L2 of the resonators 21 and 21 are coupled with a coupling coefficient M, respectively.

The terminals a and b in the figure correspond to the lead terminals 31 and 32, respectively.

(Problem to be Solved by the Invention) In the conventional bandpass filter having the above-described configuration, if the pair of resonators 21 and 21 are too close to each other, the coupling becomes strong and a predetermined filter characteristic cannot be obtained. In addition, a predetermined space distance a is required between the resonators 21, 21, which limits the miniaturization.

Further, since there is no other member between the resonators 21 and 21, it is difficult to accurately maintain the spatial distance a, and the filter characteristics tend to fluctuate.

Furthermore, since the lead terminals are of a required type, they cannot be used for surface mounting directly mounted on the wiring board surface.

SUMMARY OF THE INVENTION An object of the present invention is to provide a band-pass filter which has stable filter characteristics without restriction on miniaturization and can be used for surface mounting.

(Means for Solving the Problems) In order to achieve such an object, in a bandpass filter of the present invention, a coupling control sheet comprising a dielectric and having a coupling control electrode formed on a surface thereof, A resonator provided on each of both sides of the sheet, and a shield sheet made of a dielectric, disposed outside each of the resonators and having a shield electrode formed on the surface thereof, wherein the resonator is A dielectric sheet on which a resonator electrode having a capacitor electrode and an inductor electrode is formed, and is configured to stack and integrate the coupling control sheet, the resonator, and the shield sheet. A terminal electrode is formed on the outer peripheral surface of the laminate, and a part of each of the resonator electrodes is pulled out to the outer peripheral surface of the laminate and connected to the terminal electrode. I have.

(Operation) A coupling control electrode is interposed between the resonators, and the filter characteristics can be adjusted by adjusting the area of the coupling control electrode. That is, increasing the area of the junction control electrode weakens the magnetic coupling between the resonators, and decreasing the area increases the magnetic coupling. Therefore, by adjusting the area of the coupling control electrode so as to obtain a predetermined filter characteristic, the resonators can be arranged close to each other, so that the bandpass filter can be downsized. In addition, since the resonator electrode and the coupling control electrode are embedded in the laminate, the positional relationship between the electrodes is fixed, and the influence of the shield electrode prevents external influence. Characteristics are stabilized. Further, since the terminal electrodes connected to the respective resonance electrodes are formed on the outer peripheral surface of the laminate, the laminate 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 an internal structure.

As described with reference to these drawings, reference numeral 1 denotes a band-pass filter, and the band-pass filter 1 has a configuration in which resonators are formed on both upper and lower surfaces of a coupling control electrode 2 (prior art). The first and second resonator electrodes 3 and 4 having the same configuration as described above are arranged on the upper and lower surfaces of the coupling control electrode 2 so as to face each other. A pair of shield electrodes 5 and 6 are arranged so as to sandwich the coupling control electrode 2 and the two resonator electrodes 3 and 4 from outside in the vertical direction.

These electrodes are all buried and disposed inside the laminate 7. A plurality of terminal electrodes 8a to 8d are formed on the outer peripheral surface of the dielectric 7, and lead electrodes of resonators formed on both sides of the coupling control electrode 2 are connected to the respective terminal electrodes 8a to 8d. It is connected.

The bandpass filter 1 having such a configuration is manufactured, for example, by the following procedure described with reference to FIG.

First, a dielectric green sheet made of ceramic material
7a to 7m are stacked in the order shown. Dielectric green sheet
7a, 7c, 7f, 7h, 7k, and 7m are plain without any electrodes. Shield electrodes 5 and 6 are formed on the upper surfaces of the dielectric green sheets (shield sheets) 7b and 7l. The first resonator electrode 3 is formed on the upper surface of each of the dielectric green sheets 7d and 7i. The first resonator electrode 3 has two capacitor electrodes as in the prior art.
9, 10 and an inductor electrode 11 for connecting the two capacitor electrodes 9, 10 to each other. One capacitor electrode 9 of the first resonator electrode 3 has dielectric green sheets 7d and 7d.
An extraction electrode 12 extending to the edge of i is formed. The second resonator electrodes 4 are formed on the upper surfaces of the dielectric green sheets 7e and 7j. Similarly, the second resonator electrode 4 includes two capacitor electrodes 13 and 14 and an inductor electrode 15 connecting the capacitor electrodes 13 and 14 to each other.
It consists of On one capacitor electrode 13 of the second resonator electrode 4, a lead electrode 16 extending to the edge of the dielectric green sheets 7e and 7j is formed.

These two resonator electrodes 3 and 4 are capacitor electrodes 9, 13; 10, 14
Are opposed to each other via the dielectric green sheets 7e, 7j, and the inductor electrodes 11, 15 are arranged so as not to face each other via the dielectric green sheets 7e, 7j,
Resonators are formed on both sides of the bonding control electrode 2 respectively.

A coupling control electrode 2 is formed on the upper surface of the dielectric green sheet (coupling control sheet) 7g. The area of the coupling control electrode 2 is adjusted so that the bandpass filter 1 can obtain a predetermined filter characteristic.

The lower dielectric green sheet portion of the shield electrode 5 and the upper dielectric green sheet portion of the shield electrode 6 have a dielectric thickness of, for example, 20 after firing.
The thickness is adjusted to be about 50 μm.
Usually, a plurality of plain dielectric green sheets 7a and 7m are stacked to obtain the predetermined thickness.

Further, a dielectric green sheet portion between the shield electrode 5 and the first resonator electrode 3 above the shield electrode 5 and a dielectric green sheet portion between the shield electrode 6 and the second resonator electrode 4 below the shield electrode 6 The thickness of the portions is adjusted so that the thickness of the dielectric after firing them is, for example, about 1.0 to 1.5 mm. Usually, a plurality of plain dielectric green sheets 7c and 7k are stacked to obtain the predetermined thickness.

The dielectric green sheet portions between the first resonator electrode 3 and the second resonator electrode 4 on the upper and lower sides of the coupling control electrode 2 have a dielectric thickness of, for example, 20 after firing. The thickness is adjusted to be about 50 μm. Although not shown in the drawing, the dielectric green sheets 7d and 7e and 7i and
A plurality of plain dielectric green sheets are stacked between the sheet and 7j.

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

Then, by pressing the dielectric green sheets 7a to 7m stacked as described above from above and below and firing at a predetermined temperature, the respective dielectric green sheets 7a to 7m
To obtain a laminated body 7 (see FIGS. 1 and 2) in which each electrode is embedded. The first and second resonator electrodes are provided on the outer peripheral surface of the laminate 7 thus obtained.
The end faces of the four lead electrodes 12, 16 connected to the respective resonators formed by 3, 4 are exposed.

Then, on the outer peripheral surface of the laminated body 7, the terminal electrodes 8 a to 8 d (first
(See the figure). Thereby, the bandpass filter 1 is obtained.

The means for obtaining the band-pass filter 1 is not limited to a method of sequentially stacking the dielectric green sheets as described above, but may be a method of printing and stacking a dielectric paste and an electrode paste in a predetermined order. The system may be used.

Although the band-pass filter in the above embodiment is composed of a pair of resonators facing each other, it may be configured by using three or more resonators. In this case, a coupling control electrode may be interposed.

(Effects of the Invention) As is apparent from the above description, according to the present invention, the resonators can be arranged close to each other due to the presence of the coupling control electrode between the resonators, and the size can be reduced.
In addition, since the resonator electrode and the coupling control electrode are buried in the laminate and the shield electrode is present, the filter characteristics are stabilized. Further, the structure in which the terminal electrode is formed on the outer peripheral surface of the laminate is suitable for surface mounting.

[Brief description of 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 an internal structure thereof. FIG. 4 is a perspective view of a bandpass filter of a conventional example, FIGS. 5 and 6 are plan views showing one side and the other side of a resonator constituting the bandpass filter, and FIG. It is an equivalent circuit diagram. 1 ... band-pass filter, 2 ... coupling control electrode, 3 ...
... first resonator electrode, 4 ... second resonator electrode, 5,6 ...
... Shield electrode, 7 ... Laminated body, 7a-7m ... Dielectric green sheet, 8a-8d ... Terminal electrode, 9,10,13,14 ... Capacitor electrode, 11,15 ... Inductor electrode, 12, 16 …… Drawer electrode.

Claims (1)

(57) [Claims] 1. A coupling control sheet made of a dielectric and having a coupling control electrode formed on the surface thereof, resonators provided on both sides of the coupling control sheet, and a dielectric made of a dielectric material outside the resonators. And a shield sheet on the surface of which a shield electrode is formed, wherein the resonator is formed by laminating a dielectric sheet on which a resonator electrode having a capacitor electrode and an inductor electrode is formed. The coupling control sheet, the resonator, and the shield sheet are laminated and integrated, and a terminal electrode is formed on an outer peripheral surface of the laminate, and a part of each of the resonator electrodes is formed. A band-pass filter, wherein the band-pass filter is pulled out to the outer peripheral surface of the laminate and connected to a terminal electrode.