JP2002344274A - Balanced lc filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small balanced LC filter having superior and stable electrical characteristics. SOLUTION: Coil conductors 3a to 3d, made as spirally wound patterns, are connected electrically in series through a via hole 25 formed into insulation sheets 2b, 2c, and 2d to constitute a coil L1. Similarly, coil conductors 4a and 4b are of spirally wound patterns are connected electrically in series, through a via hole 25 formed in an insulating sheet 2r to constitute a coil L2. The coil L1 on the input-side LC parallel resonator and the coil L2 on the output-side LC parallel resonator are arranged on different layers in the laminating direction of the laminate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a balanced LC filter, and more particularly, to a balanced LC filter used for a wireless communication device such as a portable telephone or a car telephone.

[0002]

2. Description of the Related Art Generally, in a wireless communication device such as a portable telephone or a car telephone, an input / output balance having a filter function and an impedance conversion function is provided between a mixer stage and a modulation stage of a transmission system circuit. A differential filter called a type filter is used.

Conventionally, as this type of balanced LC filter, those described in JP-A-11-205065 and JP-A-11-317603 have been known. In these balanced LC filters, a first LC filter circuit section and a second LC filter circuit section are electrically connected to each other between a pair of balanced input terminals and a pair of balanced output terminals via a common line or ground. It is provided in a connected state. Each of the first and second LC filter circuit sections is configured by cascade-connecting two LC resonators. More specifically, a coil conductor and a capacitor conductor of an LC resonator are arranged inside a laminate formed by stacking insulator layers, with the insulator layers interposed therebetween.

[0004]

By the way, in the conventional balanced LC filter, for example, in order to make each of the first and second LC filter circuit sections a two-stage band-pass filter, four LC parallel resonance filters are required. Vessel was needed.
For this reason, it was difficult to obtain a small balanced LC filter.

A conventional balanced LC filter is:
In the stacking direction of the insulator layers, the coil conductor of the input-side LC resonator and the coil conductor of the output-side LC resonator are arranged on the same layer. For this reason, both are easily electromagnetically coupled,
In some cases, the filter characteristics deteriorated. Further, when the input impedance is different from the output impedance, it is difficult to cope with the conventional balanced LC filter.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a small-sized balanced LC filter having stable and excellent electric characteristics.

[0007]

In order to achieve the above object, a balanced LC filter according to the present invention comprises:
(A) a laminate formed by stacking a plurality of insulator layers, a coil conductor, and a capacitor conductor; (b) a pair of balanced input terminals and a pair of balanced output terminals provided on the surface of the laminate; A) a plurality of LC resonators constituted by the coil conductor and the capacitor conductor in the laminate;
(D) the plurality of LC resonators are cascaded electrically, and the coil conductor of the LC resonator on the balanced input terminal side and the coil conductor of the LC resonator on the balanced output terminal side are:
It is characterized by being arranged in different layers in the stacking direction of the laminate.

Here, the coil conductor is formed of a spiral pattern provided on the surface of the insulator layer, or formed by connecting via holes provided in the insulator layer in the laminating direction. Further, no ground terminal is provided on the laminate. Further, between the coil conductors of the LC resonators on the balanced input terminal side and the balanced output terminal side, it is preferable that the capacitor conductors of the LC resonators on the balanced input terminal side and the balanced output terminal side are arranged. Further, it is preferable that the coil conductor and the capacitor conductor are arranged in different layers in the stacking direction of the laminate. Preferably, the plurality of LC resonators are electrically connected in cascade via a coupling capacitor.

With the above configuration, the resonator is of a lumped constant type, and the size of the balanced LC filter can be reduced.
For example, when a two-stage band-pass filter is configured, the conventional balanced LC filter requires four LC resonators, but according to the present invention, only two LC resonators are required. Further, since the coil conductor of the input-side LC resonator and the coil conductor of the output-side LC resonator are arranged in different layers in the stacking direction of the stacked body, they are hardly electromagnetically coupled. Further, even when the input impedance and the output impedance are different, it can be easily handled.

In the balanced LC filter according to the present invention, at least one of the balanced input terminal and the balanced output terminal is electrically connected to the LC resonator via one of the capacitor and the coil. It is characterized by doing. Thus, the input / output impedance can be adjusted even with a capacitor or a coil connected to the input / output terminal.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a balanced type L according to the present invention will be described.
An embodiment of the C filter will be described with reference to the accompanying drawings.

[First Embodiment, FIGS. 1 to 4] In the first embodiment, a two-stage balanced LC filter will be described. As shown in FIG. 1, the balanced LC filter 1
Insulator sheets 2b to 2e each having a coil conductor 3a, 3b, 3c, 3d provided on the surface, and coil conductors 4a, 4b
Are provided on the surface, respectively, and insulator sheets 2g-2p provided with capacitor conductors 5-20 on the surface, respectively. Insulator sheet 2a
２2t is a sheet obtained by kneading dielectric powder or magnetic powder together with a binder or the like.

Each of the coil conductors 3a to 3d has a spiral pattern, and is electrically connected in series via via holes 25 provided in the insulating sheets 2b, 2c, and 2d to form a coil L1. Similarly, the coil conductors 4a, 4
b is also a spiral pattern, and is electrically connected in series via a via hole 25 provided in the insulator sheet 2r to form a coil L2.

The capacitor conductors 5 and 6 are made of an insulating sheet 2
It faces the capacitor conductors 7 and 8 with j interposed therebetween, and constitutes the resonator coupling capacitors C1a and C1b, respectively.
Capacitor conductors 5, 11, and 15 are made of insulating sheets 2k,
Opposing to the capacitor conductors 9 and 13 with 21, 2m and 2n interposed therebetween, an impedance adjusting capacitor C2a is formed. The capacitor conductors 6, 12, and 16 are formed by sandwiching the capacitor conductors 1 with the insulating sheets 2k, 2l, 2m, and 2n therebetween.
0, 14 and a capacitor C for impedance adjustment
2b.

The capacitor conductors 17 and 18 are opposed to the capacitor conductor 19 with the insulating sheet 2g interposed therebetween, and constitute resonance capacitors C3a and C3b, respectively. The resonance capacitors C3a and C3b are electrically connected in series. Capacitor conductors 15 and 16 are made of insulating sheet 2o
Are opposed to the capacitor conductor 20 with interposing therebetween to form resonance capacitors C4a and C4b, respectively. The resonance capacitors C4a and C4b are electrically connected in series.

The capacitors 21 are made of insulating sheets 2h and 2h.
Opposing the capacitor conductors 7 and 17 with i interposed therebetween, a pole adjustment input / output capacitor C5a is formed. The capacitor 22 faces the capacitor conductors 8 and 18 with the insulator sheets 2h and 2i interposed therebetween, and forms a pole adjustment input / output capacitor C5b. Conductors 3a to 3d, 4a, 4
b, 5 to 20 are respectively a sputtering method, a vapor deposition method,
It is formed by a method such as a printing method or a photolithography method, and is made of a material such as Ag-Pd, Ag, Pd, or Cu.

The sheets 2a to 2t are stacked and integrally fired to form a rectangular laminate 30 as shown in FIG. Six external electrodes 31 to 36 are formed on the laminate 30. The ground terminals are not included in the external electrodes 31 to 36. These external electrodes 3
Ag-Pd, Ag, P are formed by a method such as a sputtering method, a vapor deposition method, a coating method, and a printing method.
It is made of a material such as d, Cu, and Cu alloy.

The external electrode 31 is electrically connected to the coil conductor 3a and the capacitor conductors 7 and 17, and the external electrode 32
Are electrically connected to the coil conductor 3d and the capacitor conductors 8,18. The external electrodes 31 and 32 function as a pair of balanced input terminals. The external electrode 33 is electrically connected to the capacitor conductors 9, 13, 21 and the external electrode 34 is electrically connected to the capacitor conductors 10, 14, 22. The external electrodes 33 and 34 function as a pair of balanced output terminals. The external electrode 35 is electrically connected to the coil conductor 4a and the capacitor conductors 5, 11, 15. The external electrode 36 is connected to the coil conductor 4b and the capacitor conductors 6,1.
2 and 16 are electrically connected. External electrodes 35, 3
Reference numeral 6 functions as a relay terminal.

FIG. 3 shows an electrical equivalent circuit diagram of the balanced LC filter 1 having a laminated structure. The balanced LC filter 1 connects an LC parallel resonator Q1 composed of a coil L1 and capacitors C3a and C3b and an LC parallel resonator Q2 composed of a coil L2 and capacitors C4a and C4b via coupling capacitors C1a and C1b between the resonators. The circuit configuration is cascade-connected. That is, the LC parallel resonator Q
1 and Q2 are not connected via a coupling coil. L
The C parallel resonator Q2 is electrically connected to the balanced output terminals 33 and 34 via the impedance adjusting capacitors C2a and C2b.

The inductance values of the coils L1 and L2 of the LC parallel resonators Q1 and Q2 and the capacitor C3
By adjusting the capacitance values of a, C3b, C4a, and C4b, the center frequency and impedance of the balanced LC filter 1 can be adjusted. Further, the impedance can be adjusted by adjusting the capacitance values of the capacitors C2a and C2b. Note that this impedance adjustment capacitor C2
It is also possible to design by changing a and C2b to coils.

The balanced LC filter 1 having the above configuration is composed of two lumped constant type LC parallel resonators Q1 and Q2.
And can be miniaturized. Further, since the coil L1 of the input-side LC parallel resonator Q1 and the coil L2 of the output-side LC parallel resonator Q2 are arranged in different layers in the stacking direction of the stacked body 30, the coils L1 and L2 are electromagnetically coupled. Hard to do. Therefore, the input terminals 31, 32
The noise that has entered is prevented from directly propagating to the output terminals 33 and 34 via the coils L1 and L2 (not passing through the resonators Q1 and Q2), thereby preventing the filter 1 from deteriorating its characteristics. The inductances of the coils L1 and L2 can be individually designed by increasing or decreasing the number of insulator sheets provided with coil conductors, so that the values of the input impedance and the output impedance of the filter 1 are made different. And the degree of freedom of design is improved.

Further, in the first embodiment, the coils L1,
L2 and the capacitors C1a to C5b are arranged in different layers in the stacking direction of the multilayer body 30. Therefore,
The inductance of the coils L1 and L2 and the capacitor C1a
To C5b can be designed independently. FIG. 4 is a graph showing the pass characteristic S21, the input reflection characteristic S11, and the output reflection characteristic S22 of the filter 1. In the first embodiment, the capacitors C1 to C5 are disposed between the coils L1 and L2 in the stacking direction. However, since the coils L1 and L2 are hardly magnetically coupled and the characteristics of the filter 1 are not deteriorated. If present, coils L1 and L
2 may be arranged vertically.

[Second Embodiment, FIGS. 5 to 8] In a second embodiment, a three-stage balanced LC filter using via inductors will be described. As shown in FIG. 5, the balance type LC filter 41 includes lead-out conductors 43a, 43b,
Insulator sheets 42b, 42d, 42e, 42g, 42 each having 44a, 44b, 45a, 45b provided on the surface.
h, 42j and inductor via holes 46b, 47
b, 48b provided with insulator sheets 42c, 42b, respectively.
f, 42i, and insulator sheets 42l, 42m, 42o to 42 provided with capacitor conductors 51 to 75 on their surfaces, respectively.
r etc.

Via holes 46a and 46b for inductors,
47a, 47b, 48a, and 48b are respectively connected in the stacking direction of the insulator sheets 42a to 42s to form columnar inductors L11, L12, and L13 having a length of substantially λ / 4 (λ: wavelength of center frequency). I do. The inductors L11 to L13 referred to here mean that they are mainly constituted by connected via holes 46a, 46b, 47a, 47b, 48a, 48b. For example,
The lead conductors 43a to 45b also have an inductance component, and the inductors L11 to L13 are mainly constituted by via holes 46a to 48b, and the via holes 46a to 48b are designed as inductors in an equivalent circuit. In the second embodiment, the length of each of the columnar inductors L11 to L13 is substantially equal to λ.
/ 4, but the columnar inductors L11, L1
2. The length of L13 does not necessarily have to be substantially λ / 4.

The sheets 42c, 42f and 42i are set thicker than the other sheets. At this time, the sheet 42
The thicknesses of c, 42f and 42i may be secured by stacking a plurality of sheets having the same sheet thickness as the other sheets 42a or the like, or may be secured by using one thick sheet.

The axial directions of the inductors L11 to L13 are perpendicular to the surfaces of the sheets 42a to 42c. When a current flows through the inductors L11 to L13, the inductor L11
Around inductors L11 to L13
A magnetic field orbiting a plane perpendicular to the axial direction of the magnetic field is generated.
One ends (via holes 46a, 47a, 48a) of the inductors L11 to L13 are connected to the lead-out conductors 43a to 43a.
45a. The other ends of the inductors L11 to L13 (via holes 46b, 47b, 48b)
Are connected to the lead conductors 43b to 45b.

The capacitor conductors 57, 58, 59 are connected to the capacitor conductors 51, 52, 5
3, 54, 55, and 56 respectively constitute resonance capacitors C11, C12, and C13. Capacitor conductors 70, 71 are formed by capacitor conductors 66, 68, 72, 74, 67, 6 with insulator sheets 42p, 42q interposed therebetween.
9, 73, and 75, respectively, constitute pole adjustment input / output capacitors C14a and C14b. The capacitor conductors 66, 68 are opposed to the capacitor conductors 60, 62, 64 with the insulator sheet 42o interposed therebetween, and constitute the inter-resonator coupling capacitors C15a, C15b, C15c, C15d. The capacitor conductors 67 and 69 are opposed to the capacitor conductors 61, 63 and 65 with the insulator sheet 42o interposed therebetween, and the inter-resonator coupling capacitors C16a, C16b and C
16c and C16d.

Each of the sheets 42a to 42s is stacked,
By being integrally fired, a rectangular laminate 80 is formed as shown in FIG. Six external electrodes 81 to 86 are formed on the laminate 80. External electrodes 81-86
Does not include ground terminals.

The external electrode 81 is electrically connected to the lead conductor 43a and the capacitor conductors 51 and 60, and the external electrode 82 is connected to the lead conductor 43b and the capacitor conductors 52 and 60.
61 are electrically connected. External electrodes 81, 82
Function as a pair of balanced input terminals. External electrode 83
Is electrically connected to the lead conductor 45a and the capacitor conductors 55 and 64, and the external electrode 84 is connected to the lead conductor 45b.
And are electrically connected to the capacitor conductors 56 and 65. The external electrodes 83 and 84 function as a pair of balanced output terminals. The external electrode 85 is electrically connected to the lead conductor 44a and the capacitor conductors 53 and 62. The external electrode 86 is connected to the lead-out conductor 44b and the capacitor conductor 5
4, 63 are electrically connected. External electrodes 85, 8
Reference numeral 6 functions as a relay terminal.

FIG. 7 shows an electric equivalent circuit diagram of the balanced LC filter 41 having a laminated structure. The balanced LC filter 41 includes an LC parallel resonator Q1 including a coil L11 and a capacitor C11, an LC parallel resonator Q2 including a coil L12 and a capacitor C12, and a coil L13.
And an LC parallel resonator Q3 including a capacitor C13 and an inter-resonator coupling capacitor C15a to C15d, C1.
It has a circuit configuration cascaded through 6a to C16d. That is, the LC parallel resonators Q1 to Q3 are not connected via the coupling coil.

The center frequency and the impedance of the balanced LC filter 41 are adjusted by adjusting the inductance values of the coils L11 to L13 and the capacitance values of the capacitors C11 to C13 of the LC parallel resonators Q1, Q2, Q3. Can be. FIG. 8 is a graph showing the pass characteristic S21, the input reflection characteristic S11, and the output reflection characteristic S22 of the filter 41.

The balance type LC filter 41 having the above-described configuration can provide the same operation and effect as the filter 1 of the first embodiment. In the second embodiment, capacitors C11 to C13 may be arranged between the coils L11, L12, and L13.

[Other Embodiments] The balanced LC filter according to the present invention is not limited to the above-described embodiment, but can be variously modified within the scope of the gist. For example, the coil conductor of the first embodiment may have a meandering shape or a linear shape in addition to the spiral shape.

Further, in the above embodiment, the insulator sheets on which the conductors are formed are stacked and then integrally fired, but the invention is not necessarily limited to this. The sheet may be fired in advance. Further, an LC filter may be manufactured by a manufacturing method described below. After a paste-like insulator material is applied by printing or the like to form an insulator layer, an arbitrary conductor is formed by applying a paste-like conductor material to the surface of the insulator layer. Next, a paste-like insulator material is applied over the conductor. LC having a laminated structure by successively coating in this way
A filter is obtained.

[0035]

As is clear from the above description, according to the present invention, the number of resonators can be reduced, and the balance type L
The size of the C filter can be reduced. Further, since the coil conductor of the input-side LC resonator and the coil conductor of the output-side LC resonator are arranged on different layers in the stacking direction of the laminate, the coil of the input-side LC resonator and the output-side LC resonator The coil of the vessel is less likely to be electromagnetically coupled, thereby preventing a decrease in filter characteristics. Further, since the coil of the input-side LC resonator and the inductor of the coil of the output-side LC resonator can be individually designed, the input and output impedance values of the filter can be different.
The degree of freedom in design is improved. Moreover, even if the shape of the coil conductor is changed, the electromagnetic coupling between the coils does not change, so that the coupling between the resonators can be easily controlled.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing a first embodiment of a balanced LC filter according to the present invention.

FIG. 2 is a perspective view showing the appearance of the balanced LC filter shown in FIG.

FIG. 3 is an electric equivalent circuit diagram of the balanced LC filter shown in FIG. 2;

FIG. 4 is a graph showing transmission characteristics and input / output reflection characteristics of the balanced LC filter shown in FIG. 2;

FIG. 5 is an exploded perspective view showing a second embodiment of the balanced LC filter according to the present invention.

FIG. 6 is a perspective view showing the appearance of the balanced LC filter shown in FIG. 5;

FIG. 7 is an electric equivalent circuit diagram of the balanced LC filter shown in FIG. 6;

FIG. 8 is a graph showing transmission characteristics and input / output reflection characteristics of the balanced LC filter shown in FIG. 6;

[Explanation of symbols]

1, 41: Balanced LC filter 2a to 2t, 42a to 42s: Insulating sheet 3a to 3d, 4a, 4b: Coil conductor 5 to 20: Capacitor conductor 30, 80: Laminated body 31, 32, 81, 82: Balanced Input terminals 33, 34, 83, 84 ... balanced output terminals 43a, 43b, 44a, 44b, 45a, 45b ... lead-out conductors 46a, 46b, 47a, 47b, 48a, 48b ... via holes 51 to 75 ... capacitor conductors L1, L2 , L11, L12, L13 ... coils C1a, C1b, C15a to C15d, C16a to C1
6d: coupling capacitors between resonators C2a, C2b: capacitors for impedance adjustment C3a, C3b, C4a, C4b, C11, C12, C
13. Resonant capacitor Q1, Q2, Q3 ... LC parallel resonator

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5E070 AA05 AB01 BA01 CB13 CB17 EA01 5J024 AA01 BA00 BA11 DA04 DA29 DA35 EA08

Claims (8)

[Claims] 1. A laminated body formed by stacking a plurality of insulator layers, a coil conductor, and a capacitor conductor; a pair of balanced input terminals and a pair of balanced output terminals provided on a surface of the laminated body; A plurality of LC resonators configured by the coil conductor and the capacitor conductor, wherein the plurality of LC resonators are electrically cascaded, and a coil conductor of the LC resonator on the balanced input terminal side. The balanced LC filter, wherein the coil conductor of the LC resonator on the balanced output terminal side is arranged in a different layer in the stacking direction of the laminate. 2. The balanced LC filter according to claim 1, wherein the coil conductor is formed by a spiral pattern provided on a surface of the insulator layer. 3. The balanced LC filter according to claim 1, wherein the coil conductor is formed by connecting via holes provided in the insulator layer in a stacking direction. 4. A capacitor conductor of the LC resonators on the balanced input terminal side and the balanced output terminal side is disposed between the coil conductors of the LC resonators on the balanced input terminal side and the balanced output terminal side. The balanced LC filter according to any one of claims 1 to 3, wherein: 5. The balanced LC filter according to claim 1, wherein the coil conductor and the capacitor conductor are arranged in different layers in the stacking direction of the laminated body. . 6. The balanced LC filter according to claim 1, wherein a ground terminal is not provided on the laminate. 7. The device according to claim 1, wherein at least one of the balanced input terminal and the balanced output terminal is electrically connected to the LC resonator via one of a capacitor and a coil. The balanced LC filter according to any one of claims 1 to 6. 8. The balanced LC according to claim 1, wherein the plurality of LC resonators are electrically connected in cascade via a coupling capacitor.
filter.