JPH03262313A - Band pass filter - Google Patents

Abstract

PURPOSE:To attain the miniaturization of this filter by connecting one terminal and other terminal of each printed coil to a nearby capacitor electrode layer and split shielding electrode layer respectively to constitute an LC resonance circuit and coupling adjacent LC resonance circuits through magnetic coupling of the printed coils. CONSTITUTION:Both terminals of a printed coil 4a(4b) are connected to connection terminals 12a, 12b(12c, 12d), a capacitor electrode layer 8a(8b) is connected to one 12a(12c) of the terminals and a shield electrode layer 10a(10b) is connected to the other terminal 12b(12d). Since a capacitor forming layer 9 composed of a dielectric substance is interposed to a part between the shielding electrode layer 10a(10b) and the capacitor electrode layer 8a(8b), a capacitor C2(C4) is formed, and the capacitor C2(C4) and a coil L1(L2) formed by the printed coil 4a(4b) are connected by the connection terminals 12a, 12b(12c, 12d) to form the LC resonance circuit. Thus, the miniaturization of the filter is contrived.

Description

[Detailed description of the invention]

Ll Kamika■Ribun

[The present invention is a pandopass filter equipped with an LC resonant circuit]
For example, as a bandpass filter equipped with two stages of LC resonant circuits, one constructed of the equivalent circuit shown in FIG. 11 is known. There are two types of structures for this filter: One is to connect a capacitor part and a coil part with a wire or the like to obtain two resonant circuits, and make these resonant circuits magnetically coupled between the coil parts, and connect an input capacitor to one of the resonant circuits. This is a so-called discrete type in which an output capacitor is connected to the other resonant circuit. The other method is to form two pairs of partially opposing electrodes on both sides of a dielectric substrate by printing, etc., and form a capacitor in the opposing part of each electrode, and a coil in the non-facing part. A 2ML resonant circuit was obtained by this method, and counter electrodes for input/output capacitors were placed around the two pairs of electrodes constituting these resonant circuits, connected to the respective electrodes, for matching the impedance. This is a type in which the equivalent circuit shown in FIG. 11 is created by printing simultaneously at the time of formation. However, in the case of the former discrete type, separate electronic components are connected by wires, etc., which makes it large and difficult to shield the outside. In the latter case, two resonant circuits are formed along the surface of the dielectric substrate, and the capacitor section and coil section of each resonant circuit are arranged side by side, so there is no need for shielding. Also, like the former, there was the problem of increasing the size. The present invention has been made to solve such problems,
The purpose of the present invention is to provide a bandpass filter that has a shield structure and is miniaturized. In the bandpass filter according to the present invention for the purpose of One of these shield electrode layers is divided into the same number of printed coils, and a capacitor electrode layer that constitutes a capacitor is formed between each divided shield electrode layer and the divided shield electrode layer. One end and the other end of the printed coil are connected to the nearest capacitor electrode layer and split shield electrode layer, respectively, to form one LC resonant circuit, and adjacent LC resonant circuits are coupled by magnetic coupling between the printed coils. In the present invention, both outer sides are covered with shield electrode layers, so that the inside is shielded. A capacitor is formed between the capacitor electrode layer, that is, the split shield electrode layer serves as one electrode of the capacitor, and the capacitor having this electrode is laminated to the printed coil corresponding to the inductor of the LC resonant circuit. Figure 1 shows a bandpass filter (two-stage LC) according to the present invention.
FIG. 2 is a cross-sectional view showing an example of a resonant circuit (including a resonant circuit). This filter is made by appropriately laminating a green sheet made of an unfired dielectric material, etc., and an electrode layer made of a conductive material formed on one side of the green sheet by printing, etc., and the side surface is also made of a conductive material. The external connection terminal is formed by printing or the like and then fired. A protective layer 1 is formed at the bottom in the thickness direction, and a shield electrode layer 2, a dielectric layer 3, a printed coil 4,
A dielectric layer 5, an input/output capacitor layer 6, a capacitor forming layer 7, a capacitor electrode layer 8, a capacitor forming layer 9, a shield electrode layer 10, and a protective layer 11 are formed in this order. As shown in FIG. 2, the printed coil 4 includes two printed coils 4a and 4b, and these printed coils 4a and 4b are arranged in parallel with an appropriate distance apart so that they can be magnetically coupled. The shield electrode layer lO on the upper side of the printed coils 4a, 4b consists of two shield electrode layers 10a, 10b separated from each other, as shown by solid lines in FIG. As shown by the broken line in , it consists of two capacitor electrode layers 8a and 8b that face the shield electrode layers 10a and 10b and have a smaller area than the shield electrode layers 10a and 10b. Note that the shield electrode layer 2 below the printed coils 4a and 4b is also composed of two separated layers as shown by solid lines in FIG. 3, but these are not separated but integrated. It's okay. The printed coil 4a has connection terminals 12a, 1 at both ends.
2b, the capacitor electrode layer 8a is connected to one side 12a, and the shield electrode layer 10 is connected to the other side 12b.
a is connected. At the portion where the shield electrode layer 10a and the capacitor electrode layer 8a face each other, a capacitor forming layer 9 made of a dielectric material is interposed between the shield electrode layer 10a and the capacitor electrode layer 8a, so that a capacitor C2 is formed. The formed coil L1 is the connection terminal 1
2a and 12b to form an LC resonant circuit. On the other hand, the printed coil 4b has connection terminals 12c at both ends,
12d, the capacitor electrode layer 8b is connected to one side 12C, and the shield electrode layer 1 is connected to the other 12d.
0b is connected. In the portion where the shield electrode layer 10b and the capacitor electrode layer 8b face each other, a capacitor forming layer 9 made of a dielectric material is interposed between them, so a capacitor C4 is formed, and the capacitor C4 and the printed coil 4b are connected to each other. The formed coil L2 is the connection terminal 12
c and 12d to form an LC resonant circuit. The input/output capacitor layer 6 located below the capacitor electrode layers 8a and 8b, which are one electrodes of these capacitors C2 and C4, has two input capacitor layers 6a as shown by the dashed line in FIG. Consists of an output capacitor layer 6b, an input capacitor layer 6a and a capacitor electrode layer 8a.
A capacitor CI is formed between the capacitor C1 and the capacitor forming layer 7 made of a dielectric material, and this capacitor C1 is connected to the input connection terminal 13a. On the other hand, between the output capacitor layer 6b and the capacitor electrode layer 8b, the capacitor C3
is formed, and this capacitor C3 is connected to the output connection terminal 13.
connected to b. Therefore, as shown in FIG. 4, the band-pass filter having the above-mentioned configuration has a first L which consists of a coil L1 and a capacitor C2.
A C resonance circuit Q1 and a second LC resonance circuit Q2 consisting of a coil L2 and a capacitor C4 are coupled with a magnetic amount M between the coils LL and L2, and an input capacitor CI is connected to the first LC resonance circuit Ql. The circuit has a circuit configuration in which an output capacitor C3 is connected to the second LC resonant circuit Q2, and both sides of the circuit are covered with shield electrode layers 2.10.
The printed coil 4a,
It has a structure in which capacitors C2 and C4 and input/output capacitors CI and C3 are present on one side of 4b. In addition,
L3. L4 is the inductance of the connection terminals 12b and 12d that connect the shield electrode layers 10a and 10b. FIG. 5 shows the frequency characteristics of the bandpass filter having this configuration. Figure 6.7.8 is a diagram showing another embodiment of the present invention,
6 is a cross-sectional view thereof, FIG. 7 is a plan view showing the printed coil 4 portion, and FIG. 8 is a plan view showing the vicinity of the shield electrode layer 10. 4 in the figure indicates a printed coil, and this printed coil 4
are three printed coils 4a, 4b, 4c tilted diagonally.
(see Fig. 7), and both ends of these printed coils 4a, 4b, 4c are connected to terminals 12a, 12c, 12e of 12 connection terminals 12a-121 formed on the side surface.
, 12h, 12j, and 1242 as appropriate. The shield electrode layers 10a, 10b, 10c on the upper side of each printed coil 4a, 4b, 4c are also divided into three parts as shown by solid lines in FIG.
a, 10b, and 10c have capacitor electrode layers (
dashed line) 8a. 8b and 8c are provided. Furthermore, 2) 8a of these capacitor electrode layers 8a, 8b, and 8c. Input/output capacitor layers (6a, 6c) are formed opposite to 8c, and input/output capacitors CI are formed between these input/output capacitors 6a, 6c and capacitor electrode layers 8a, 8C. , C5 are formed. The input/output capacitor layers 6a, 6c have connection terminals 12b, 12d, 12f, 12g, 12i that are not connected to the printed coil 4a, etc. or the capacitor electrode layer 8a, etc.
, 12, etc., two of which are connected to 12f, 12g. These human/output capacitor layers 6a, 6c are input/output capacitor layers 6a, 6c.
This is for matching the impedance of the output terminal portion, and may be omitted. This also applies to the configuration shown in FIG. 1 described above. Note that the shield electrode layer 2 under the printed coils 4a, 4b, and 4c also has three separated layers as shown by the solid line in FIG. 8, but these are not separated but integrated. It is also possible. Therefore, as shown in FIG. 9, the bandpass filter with this configuration has a first L made of a coil L1 and a capacitor C2.
A C resonant circuit Q1, a second LC resonant circuit Q2 consisting of a coil 2 and a capacitor C3, and a third LC resonant circuit Q3 consisting of a coil L3 and a capacitor C4 are connected to a coil Ll.
, L2. The input capacitor C1 is connected to the first LC resonant circuit Q1, and the third L
The circuit has a circuit configuration in which an output capacitor C5 is connected to a C resonant circuit Q3, and both sides of this circuit are shielded with shield electrode layers 2.10, and the thickness of printed coils 4a, 4b, and 4c is Capacitors C2, C3, C4 are on one side of the direction, and input/output capacitors CI, C5
It has a structure in which there is In addition, L4. L5. L6
is the inductance of the connection terminals 12a, 12c, 121 connecting the shield electrode layers 10a, 10b, 10c. The frequency characteristics of this filter are shown in FIG. 1O, in which the solid line is the attenuation characteristic and the broken line is the return loss characteristic. Further, in this bandpass filter, since the printed coil 4a and the like are tilted diagonally, it is possible to mount it on a wiring board etc. even when the left and right sides are reversed. In this three-stage bandpass filter, the second LC resonant circuit Q2 may or may not be grounded, and similar frequency characteristics can be obtained in both cases. Furthermore, although the above two embodiments show cases of two stages and three stages, the present invention is of course not limited to this, and can of course be similarly applied to bandpass filters of four stages, five stages or more. . As described in detail above, in the case of the present invention, both outer sides are covered with shield electrode layers, so that there is little external electromagnetic influence. Further, since the capacitor is laminated on the printed coil, there is an effect that the size can be reduced. Further, since it has a laminated structure, it can be set by soldering connection terminals formed on its side surfaces to wiring on a wiring board, etc., and has the advantage that surface mounting is also possible.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of a bandpass filter according to the present invention, FIG. 2 is a plan view showing a printed coil portion of the filter, FIG. 3 is a plan view showing a capacitor portion of the filter, and FIG. Fig. 4 is an equivalent circuit diagram of the filter shown in Fig. 1, Fig. 5 is a frequency characteristic diagram of the filter, Fig. 6 is a sectional view showing another embodiment of the present invention, and Fig. 7 is a 11.1 diagram of the filter. Fig. 8 is a plan view showing the capacitor part of the filter, Fig. 9 is an equivalent circuit diagram of the filter, Fig. 10 is a frequency characteristic diagram of the filter, and Fig. 11 is a conventional band diagram. FIG. 3 is an equivalent circuit diagram of a pass filter. Figure 1 Figure 2 2.10 (10a, 10b, 10c)...Shield electrode layer, 3.5-...Dielectric layer, 4 (4a, 4b)
. 4c)...Printed coil (inductor), 12a~
12j! , 13a, 13b... connection terminals.

Claims (1)

[Claims] (1) Printed coils are arranged in parallel in a mutually magnetically coupled state in the middle part of the dielectric layer, and shield electrode layers are formed on both sides of the dielectric layer, and one of these shield electrode layers is connected to the printed coil. A capacitor electrode layer that constitutes a capacitor is formed between each divided shield electrode layer and the divided shield electrode layer, and one end and the other end of each printed coil connect to the nearest capacitor. A bandpass filter characterized in that one LC resonant circuit is configured by being connected to an electrode layer and a split shield electrode layer, and adjacent LC resonant circuits are coupled by magnetic coupling between printed coils.