JP3466400B2 - filter - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a filter provided in a multilayer substrate used for a communication device or the like. 2. Description of the Related Art In recent years, a filter used for a communication device such as a wireless telephone has been required to be downsized. From now on, it has been developed to a built-in type constituted by embedding a resonance electrode in a wiring board. [0003] Such a built-in type filter has three insulating layers 11a, 11b and 11 as shown in FIG.
c, the large-area ground electrodes 12a and 12b are provided on the lower surface of the insulating layer 11a and the upper surface of the insulating layer 11c, and the two resonant electrodes 13a and 13b having an open end and a ground end are provided on the upper surface of the insulating layer 11a. On the upper surface of the layer 11b, two capacitor electrodes 14a, 14b opposed to the resonance electrodes 13a, 13b, respectively, are arranged, and the ground electrodes 12a, 12b and the ground end side of the resonance electrodes 13a, 13b are connected to via holes 15a. , 15b, 15c, 15
d, 15e, 15f, and the capacitor electrodes 14a, 14b
It has a structure electrically led to the outside through g and 15h. In the drawing, L is a land pattern. FIG. 6 shows an equivalent circuit of this filter. In FIG. 6, Y1 is self-admittance on the open end side of the resonance electrode 13a, Y2 is self-admittance on the ground end side of the resonance electrode 13a, Y3 is self-admittance on the open end side of the resonance electrode 13b, and Y4 is ground on the resonance electrode 13b. Self admittance at the end, Y13 is the mutual admittance between the open end of the resonance electrode 13a and the open end of the resonance electrode 13b, Y24 is the mutual admittance between the ground end of the resonance electrode 13a and the ground end of the resonance electrode 13b, C1 indicates the capacitance formed between the resonance electrode 13a and the capacitor electrode 14a, and C2 indicates the capacitance formed between the resonance electrode 13b and the capacitor electrode 14b, and these constitute a filter circuit. Is done. One of the characteristics required of a filter is to selectively pass only a predetermined frequency. For this purpose, it is necessary that the pass band is narrow and has a frequency pass characteristic such that the pass band has a steep attenuation pole near the pass band. In such a filter, in order to narrow the pass band and form a large attenuation pole near the pass band, the self admittances Y1 and Y2 of the resonance electrode 13a and the self admittance Y of the resonance electrode 13b are required.
3, Y4 and the mutual admittance Y13, Y24 of the resonance electrodes 13a, 13b must be large with respect to the input / output admittance. However, according to the above-described filter, the resonance electrodes 13a and 13b are two-dimensionally arranged on the same plane.
The resonance electrode 3a and the resonance electrode 13b are mainly coupled between the side end of the resonance electrode 13a and the side end of the resonance electrode 13b, and the coupling between the resonance electrode 13a and the resonance electrode 13b is small because the coupling is small. The admittances Y13 and Y24 could not be made large, and as a result, it was not possible to obtain a frequency pass characteristic having a narrow pass band and a steep attenuation pole near the pass band. Further, according to this filter, stray capacitances C3 and C4 are formed between the capacitor electrode 14a and the capacitor electrode 14b and the ground electrode 12b, and between the capacitor electrode 14a and the capacitor electrode 14b and the ground electrode 12b. The formed floating capacitances C3 and C4 reduce the attenuation of the attenuation pole formed in the vicinity of the pass band, so that it is not possible to obtain a frequency pass characteristic having a steep attenuation pole in the vicinity of the pass band. Was. [0009] The filter of the present invention comprises:
Two resonance electrodes, one end of which is electrically connected to the ground electrode and the other end of which is electrically open, are disposed inside the insulating base sandwiched between a pair of ground electrodes so as to face each other. And a filter in which two capacitor electrodes facing each of the two resonance electrodes are disposed inside the insulating base, wherein the two resonance electrodes are each a pair of counter electrodes and the pair of counter electrodes. And a common electrode electrically connected to the common electrode, and the capacitor electrode smaller than the counter electrode is disposed between the pair of counter electrodes so as to be cut off from the ground conductor by the pair of counter electrodes. It is characterized by being provided. According to the filter of the present invention, since the two resonance electrodes are arranged side by side inside the insulating base so as to face each other, the facing area between the two resonance electrodes is large, and the two resonance electrodes are large. The mutual admittance between them can be large. Further, according to the filter of the present invention, each resonance electrode is formed by a pair of opposed electrodes and a common electrode electrically connected to the pair of opposed electrodes in common, and Since the capacitor electrode is disposed between the electrodes, the capacitor electrode is hardly interrupted from the ground electrode by the pair of opposed electrodes, and has no unnecessary stray capacitance between the capacitor electrode and the ground electrode. Next, a filter according to the present invention will be described with reference to the accompanying drawings. FIG. 1 is a cross-sectional view showing one embodiment of the filter of the present invention, wherein 1 is an insulating base, 2a, 2a
b is a ground electrode, 3a and 3b are resonance electrodes, and 4a and 4b are capacitor electrodes. The insulating substrate 1 is made of glass ceramic,
Insulating layer 1 made of an electrically insulating material such as alumina and mullite
a, 1b, 1c, 1d, 1e, 1f, and 1g are laminated in multiple layers, and ground electrodes 2a and 2b are provided on upper and lower surfaces thereof, and resonance electrodes 3a and 3b and a capacitor electrode 4 are provided therein.
a, 4b are provided. The insulating substrate 1 is made of, for example, alumina 18.
0 to 24.0% by weight, 8.0 to 17.0% by weight of quartz, 13.0 to 25.0% by weight of cordierite, the balance being formed of glass ceramics of borosilicate glass, and 72.0 to 76. 0% by weight silicon oxide, 15.0
To 17.0% by weight of boron oxide, 2.0 to 4.0% by weight of alumina, 1.5% by weight or less of magnesium oxide, 1.1 to 1.4% by weight of zirconium oxide. 1 to borosilicate glass powder composed of 0 to 3.0% by weight of lithium oxide, potassium oxide and sodium oxide
8.0 to 24.0 wt% alumina powder, 8.0 to 17.0 wt% quartz powder, 13.0 to 25.0 wt% cordierite powder and a suitable organic binder, solvent, plasticizer, A green sheet (raw sheet) is obtained by adding and mixing a dispersing agent or the like to form a slurry, and forming the slurry into a sheet by employing a conventionally known doctor blade method or calender roll method. The sheet is subjected to an appropriate punching process, and a plurality of sheets are vertically stacked to form a green sheet laminate. Finally, the green sheet laminate is fired at a temperature of about 900 ° C. Ground electrodes 2a and 2b are provided on the upper and lower surfaces of the insulating base 1, and a resonance electrode 3 is provided inside the insulating base 1.
a, 3b and capacitor electrodes 4a, 4b are provided respectively, and the ground electrodes 2a, 2b, the resonance electrodes 3a, 3b and the capacitor electrodes 4a, 4b are provided at predetermined positions on the surface and inside of the insulating base 1. This forms the filter of the equivalent circuit shown in FIG. The ground electrodes 2a, 2b, the resonance electrodes 3a,
3b and the capacitor electrodes 4a and 4b are made of a metal material such as copper, silver, or a silver-palladium alloy. When made of copper, they are obtained by adding a suitable organic binder, a solvent, and the like to copper powder and mixing. The metal paste is printed and applied in a predetermined pattern on the upper and lower surfaces of the green sheets to be the respective insulating layers 1a to 1g of the insulating substrate 1 by using a thick film method such as a screen printing method in advance. Are arranged in a predetermined pattern on the upper and lower surfaces and inside. The ground electrodes 2a and 2b provided on the upper and lower surfaces of the insulating base 1 apply a ground potential to the filter, and provide resonance electrodes 3a and 3b and a capacitor electrode 4a.
4b is electromagnetically shielded from the outside, and FIG.
As shown in (a) to (h), it is formed on substantially the entire lower surface of the insulating layer 1a and the upper surface of the insulating layer 1g, and when viewed in a plan view, the resonance electrodes 3a and 3b and the capacitor electrode 4
a, 4b. The ground electrodes 2a and 2b are electrically connected to each other via via holes 5a provided on the outer peripheral portions of the insulating layers 1a to 1g forming the insulating base 1. Further, as shown in FIG. 3H, openings 6a and 6b are formed in a part of the ground electrode 2b disposed on the upper surface of the insulating base 1, and the ground electrodes 2b are formed in the openings 6a and 6b. Are provided with input / output pads 9a and 9b connected to capacitor electrodes 4a and 4b described later. The input / output pads 9a, 9b function as terminals for inputting / outputting signals to / from the filter, and signals are input / output to / from the filter via the input / output pads 9a, 9b. Further, two resonance electrodes 3a and 3b are embedded in the insulating base 1, and the respective resonance electrodes 3a and 3b are opposed to each other with an insulating layer interposed therebetween. The one resonance electrode 3a has one end connected to the ground electrodes 2a and 2b via the via hole 5a, and one end connected to the common electrode 7a via the via hole 5b.
And the other end is formed of a pair of electrically opposed electrodes 8aa and 8ab whose other end is electrically open, and one end of the other resonance electrode 3b is connected to the ground electrodes 2a and 2b through the via hole 5a. A common electrode 7b, and one end of the common electrode 7b is connected to the common electrode 7b through a via hole 5c.
A pair of opposing electrodes 8ba, 8 whose other ends are electrically open
bb. The common electrode 7a of the resonance electrodes 3a, 3b,
Reference numeral 7b functions as a ground end side portion of each of the resonance electrodes 3a and 3b, and as shown in FIGS. 3C and 3F, a substantially rectangular shape having frame portions 6c and 6d surrounding the capacitor electrodes 4a and 4b on one end side. The common electrodes 7a and 7b are opposed to each other with the insulating layers 1c, 1d and 1e interposed therebetween. The common electrode 7a of the resonance electrodes 3a, 3b,
7b is electrically connected at one end to the ground electrodes 2a and 2b through via holes 5a provided in the insulating layers 1a to 1g of the insulating base 1, and is connected to the via holes 5b at the frame portions 6c and 6d at the other end. , 5c via a pair of opposing electrodes 8aa, 8aa
ab and 8ba, 8bb are electrically connected. The opposite electrodes 8aa, 8ab and 8ba, 8b connected to the frame portions 6c, 6d formed on the other ends of the common electrodes 7a, 7b through via holes 5b, 5c.
b has a substantially rectangular shape as shown in FIGS. 3B, 3D, 3E, and 3G, with one end opened, and the opposing electrodes 8aa, 8ab having the insulating layers 1b, 1c therebetween. The opposing electrodes 8ba and 8bb are opposed to each other with the insulating layers 1e and 1f interposed therebetween. The pair of opposed electrodes 8aa, 8ab and 8
Since ba and 8bb are open at one end, they act as open end portions. Further, between the pair of opposed electrodes 8aa and 8ab, the capacitor electrode 4a is inserted into the frame 6c of the common electrode 7a.
However, a capacitor electrode 4b is formed in the frame 6d of the common electrode 7b between the pair of counter electrodes 8ba, 8bb, and the capacitor electrode 4a is formed of a pair of the counter electrodes 8a.
a and 8ab with the insulating layers 1b and 1c interposed therebetween, and the capacitor electrode 4b is formed of a pair of counter electrodes 8ba and 8b.
and b with the insulating layers 1e and 1f interposed therebetween. The capacitor electrode 4a has insulating layers 11c, 11d, 11e, 11f and 11f as shown in FIG.
g is connected to the input / output pad 9a formed on the outer surface of the insulating layer 11g via a via hole 5d provided in the insulating layer 11g. The capacitor electrode 4b is connected to the insulating layer 11g via a via hole 5e provided in the insulating layers 11f and 11g. It is connected to an input / output pad 9b formed on the outer surface. The capacitor electrodes 4a and 4b are provided between the pair of opposed electrodes 8aa and 8ab of the resonance electrode 3a and between the two electrodes 8ba and 8bb of the opposed electrode 8b of the resonance electrode 3b, respectively, as shown in FIG. Capacitance C1 in the circuit
C2 is formed, and the resonance electrodes 3a and 3b and the input / output pad 9 are formed.
a, 9b in a DC manner. According to this filter, when the ground electrodes 2a and 2b are connected to the ground potential and an input signal is input to the input / output pad 9a, the input signal is input to the resonance electrode 3a via the capacitor electrode 4a, At the electrode 3a, a signal of a predetermined frequency among the input signals selectively causes resonance, and the energy of the resonance is changed to the resonance electrode 3a.
is transmitted to the resonance electrode 3b by an electromagnetic coupling between the resonance electrode 3b and the resonance electrode 3b, resonance occurs at a predetermined frequency at the resonance electrode 3b, and the resonance is output from the input / output pad 9b via the capacitor electrode 4b. Can be selectively passed. In this case, the resonance electrodes 3a and 3b are
Since they are vertically opposed to each other with the insulating layers 1d, 1c, and 1e interposed therebetween, the mutual facing admittance between the resonant electrodes 3a and 3b is increased by increasing the mutually facing areas of the resonant electrodes 3a and 3b. As a result, the filter can be provided with a frequency pass characteristic having a narrow pass frequency band and a sharp attenuation pole near the pass frequency band. The capacitor electrodes 4a and 4b are
Since the upper and lower portions are sandwiched between the pair of opposing electrodes 8aa, 8ab and 8ba, 8bb of the resonance electrodes 3a, 3b, they are electromagnetically cut off from the ground electrodes 2a, 2b, and as a result, the capacitor electrode 4a Unnecessary stray capacitance is not formed between the ground electrodes 2a and 2b and the ground electrodes 2a and 2b, and the filter can be provided with a frequency pass characteristic having a steep attenuation pole near the pass band. It should be noted that the filter of the present invention is not limited to the above-described embodiment, and various changes can be made without departing from the scope of the present invention. The ground electrodes 2a, 2b are disposed on the upper and lower surfaces of the insulating base 1 and are exposed to the outside. However, as shown in FIG.
The insulating layers 1h and 1i may be further laminated on the substrate b and wiring may be performed inside the insulating base 1. According to the filter of the present invention, since the two resonance electrodes are arranged side by side inside the insulating base so as to face up and down, a large opposing area between the two resonance electrodes is obtained. As a result, it is possible to increase the mutual admittance between the two resonance electrodes, thereby achieving a frequency pass characteristic having a narrow pass frequency band and a sharp attenuation pole near the pass frequency band. Further, according to the filter of the present invention, since the capacitor electrode is sandwiched between the pair of resonance electrodes, the capacitor electrode is cut off from the ground electrode. There is almost no stray capacitance, and this also makes it possible to achieve a frequency pass characteristic having a narrow pass frequency band and a sharp attenuation pole near the pass frequency band.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view showing one embodiment of a filter of the present invention. FIG. 2 is an equivalent circuit diagram of the filter shown in FIG. 3 (a) to 3 (h) are plan views of each insulating layer of the filter shown in FIG. FIG. 4 is a sectional view showing another embodiment of the filter of the present invention. FIG. 5 is an exploded perspective view showing a conventional filter. FIG. 6 is an equivalent circuit diagram of the filter shown in FIG. [Description of Signs] 1 ... Insulating bases 1a to 1g ... Insulating layers 2a, 2b ... Ground electrodes 3a, 3b ... Resonant electrodes 4a, 4b ... Capacitor electrodes 7a ... Resonant electrodes Common electrodes 7a of 3a ··· Common electrodes 8aa and 8ab of resonant electrode 3b · · · Counter electrodes 8ba and 8bb of resonant electrode 3a · · · Counter electrodes of resonant electrode 3b

Claims (1)

(57) [Claim 1] Inside an insulating base sandwiched between a pair of ground electrodes, one end of each is electrically connected to the ground electrode, and the other end is electrically open. A filter having two resonance electrodes disposed so as to face each other, and two capacitor electrodes facing each of the two resonance electrodes disposed inside the insulating base. electrodes are formed by a common electrode each of which is electrically connected in common to a pair of opposed electrodes and the pair of opposed electrodes, the opposed between a pair of opposed electrodes
Small said capacitor electrode of the pair of pairs than electrodes
A filter disposed so as to be shielded from the ground conductor by a counter electrode .