JPH1075143A - LC bandpass filter - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide an LC bandpass filter with less waveform disturbance. SOLUTION: An auxiliary ground electrode 40 is formed on the lower surface of an insulating substrate 1 provided at the lowermost layer, and a ground electrode 26 formed on an upper conductive layer 21 is connected to an auxiliary ground electrode via a conductive path 41 formed in the thickness direction. Since it is connected to 40, the area of the ground electrode is increased, external noise can be cut off, and the waveform is stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an LC bandpass filter used for various wireless communication devices such as a portable telephone and a car telephone.

[0002]

2. Description of the Related Art As an LC bandpass filter, a filter having a parallel resonance circuit in which an input / output capacitor and an inductor are connected in parallel by a thin, plural or single insulating substrate such as alumina is generally used. ing. This L
The C bandpass filter is an integrated dielectric filter in which a plurality of through-hole-shaped resonance conductors are formed in a dielectric block, or a three-conductor stripline filter in which a foil-shaped resonance conductor is sandwiched between two dielectric substrates. It is being favorably used in mobile phones and the like because of its advantages such as easy thinning and miniaturization as compared with.

On the other hand, in recent years, there has been a growing demand for downsizing, high performance, and high-density mounting of electronic devices and the like. Therefore, further downsizing of LC bandpass filters has been strongly demanded. ing. In order to respond to this demand, it is required to reduce the size of the capacitance portion that occupies most of the filter. In order to achieve this reduction, the capacitance portion has a multilayer structure by a thin film forming technique such as a sputtering method or a CVD method. Things have been suggested.

[0004]

In the above-described LC bandpass filter having a multilayer structure, the area of the ground electrode is insufficient because the ground electrode is conventionally formed only in a part of the uppermost layer. Therefore, there is a problem that the stabilization is not performed, the noise from the outside cannot be sufficiently shut off, and the waveform is likely to be disturbed. It is an object of the present invention to correct the problems of the conventional LC bandpass filter having a multilayer structure.

[0005]

According to the present invention, there is provided a multilayer structure having at least a ground electrode provided on an upper conductive layer provided on an uppermost layer thereof, and an auxiliary electrode provided on a lower surface of an insulating substrate provided on a lowermost layer. An LC band-pass filter, wherein a ground electrode is formed, and the ground electrode of the upper conductive layer is connected to an auxiliary ground electrode via a conductive path formed through each layer.

An auxiliary ground electrode is formed on the lower surface of the lowermost insulating substrate by utilizing the lower surface thereof, and this is connected to the ground electrode of the uppermost layer via a conductive path formed in the thickness direction. . Therefore, the area of the ground electrode is increased, and the waveform is stabilized.

As a filter having such a structure, as illustrated in FIG. 1, a lower conductive layer 2 is formed on the surface of an insulating substrate 1 which is a lowermost layer, and two common capacitor electrodes 3a are formed on the lower conductive layer 2. , 3b, a dielectric thin film layer 10 is formed on the lower conductive layer 2, and the dielectric thin film layer 10
An intermediate conductive layer 11 is formed thereon, and the other side capacitor electrodes 12a and 13a of the input / output capacitor C ₁ and the resonance capacitor C ₃ are respectively provided on portions of the intermediate conductive layer 11 facing the common capacitor electrode 3a. Provided, common capacitor electrode 3
b, the other side capacitor electrodes 12b and 13b of the input / output capacitor C ₂ and the resonance capacitor C ₄ are further provided, and an insulating layer 20 is further provided on the intermediate conductive layer 11. To form an upper conductive layer 21;

The upper conductive layer 21 has a ground electrode 26,
Inductors L ₁ and L ₂ extending from the ground electrode 26;
Furthermore, the input capacitor C _1, C ₂ of the other side capacitor electrodes 12a, 12b and respectively connected to input and output electrodes 22a, as well as arranged and 22b, inductor L _1,
The end of L _2, the common capacitor electrode 3 of the lower conductive layer 2
a, 3b, and the ground electrode 26 is connected to the other capacitor electrodes 13a, 13b of the lower conductive layer 2, respectively. Further, the auxiliary ground electrode 40 is connected to the lower surface of the insulating substrate 1 provided at the lowermost layer. The LC bandpass filter formed by connecting the ground electrode 26 of the upper conductive layer 21 to the auxiliary ground electrode 40 via the conductive path 41 formed in the thickness direction is small and has a small ground electrode area. As a result, a stable filtering characteristic can be obtained.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 shows an LC band-pass filter according to the present invention, in which a dimension example is formed on a rectangular insulating substrate 1 such as alumina having a thickness of about 0.635 mm and a length and width of about 2 mm. lower conductive layer 2 (thickness 3 [mu] m), a dielectric thin film layer 10 made of SiO ₂ comprising (thickness 2
μm), an intermediate conductive layer 11 made of aluminum (thickness 3 μm), an insulating layer 20 made of an organic insulating film such as a polyimide resin (thickness 3 μm), and an upper conductive layer 21 made of Cu (thickness 5 μm). They are sequentially laminated. Moreover, almost half of the surface area of the filter and the capacitor formation region S _1, are another half an inductor forming area S _2. As can be understood from the sum, the total thickness of the whole becomes an extremely thin shape of 0.7 mm or less.

[0010] The insulating substrate there 1 to the lower conductive layer 2 formed on, in its capacitor formation region S _1, rectangular two common capacitor electrode 3a adjacent to the left and right, 3b
There are juxtaposed, it extends the connection passage 4, 4 to each inductor forming area S ₂ side. A border 5 is formed around the upper surface of the insulating substrate 1 and along the center line thereof, and the border 5 forms a laminated surface with the dielectric thin film layer 10 and has no difference in thickness at the periphery. In this manner, uniform surface contact is ensured.

[0011] In the intermediate conductive layer 11 formed on the dielectric thin film layer 10, wherein the common capacitor electrode 3a facing the site, and the other side capacitor electrode 12a of the input and output capacitors C _1, which and another-side capacitor electrodes 13a of the resonance capacitor C ₃ adjacent is provided surrounding the L-shaped, the part facing the common capacitor electrode 3b is the other side capacitor electrodes 12 of the input and output capacitors C ₂
b and an adjacent resonance capacitor C surrounding the L shape
_{And four} other-side capacitor electrodes 13b.

An insulating layer 20 made of an organic insulating film such as a polyimide resin is laminated on the intermediate conductive layer 11 by a spin coating method or the like. The upper conductive layer 21 formed on the insulating layer 20 is formed by a copper plating method or the like. In the the upper conductive layer 21, the capacitor formation region S _1, input and output electrodes 22a is provided at a position facing the other side capacitor electrodes 12a, also the other side capacitor electrodes 12
An input / output electrode 22b is provided at a position opposing b. Further, input and output electrodes 22a, the inter-22b, which are coupling electrodes 24 for capacitively coupling is formed at the insulating gap 25, 25, the insulating gap, the coupling capacitor C ₅
Is formed.

Further, the capacitor formation region S _1, these input and output electrodes 22a, 22b, so as to surround the coupling electrode 24, the ground electrode 26 is formed. From the center of the inner edge of the ground electrode 26, the inductor forming region S
_A straight path is formed on the _two sides. This straight path is the inductor L
₃ , and the reflection loss can be adjusted by adjusting the length as described later. Then, from the end of the inductor inductor L _3, the inductor forming area S _2, is branched into two on both sides, the two spiral inductors L _1, L ₂ which is wound toward the center from the outside Coupling Will be done.

The centers of the spiral inductors L ₁ and L ₂ are connected to the common capacitor electrodes 3 a and 3 b on the insulating substrate 1 via a conductive path 30 formed through the insulating layer 20 and the dielectric thin film layer 10. The roads 4 and 4 are connected. Further, the ground electrode 26 is connected to the other-side capacitor electrodes 13a and 13b of the resonance capacitors C ₃ and C ₄ via the conduction path 31 formed in the insulating layer 20. Similarly, input / output electrode 2
2a and 22b are connected to the other-side capacitor electrodes 12a and 12b by a conduction path 32 formed in the insulating layer 20.

As described above, the dielectric thin film layer 1
Through 0, the common capacitor electrode 3a, output capacitor C ₁ between the other side capacitor electrode 12a is formed, the common capacitor electrode 3b, output capacitor C ₂ between the other side capacitor electrode 12b is formed, further common capacitor electrode 3a, the resonance capacitor C ₃ is formed between the other side capacitor electrodes 13a, the common capacitor electrode 3b, the resonant capacitor C ₄ is formed between the other side capacitor electrodes 13b, further, through the coupling electrodes 24 , Input / output electrode 2
2a, together with the coupling capacitor C ₅ may be formed between 22b, to the ground, the inductor L _3, a resonance capacitor C
_3, relative to the spiral inductor L ₁ of the resonant capacitor C ₄ is connected, and branched from the inductor L _3,
A resonance capacitor C ₃ is connected in parallel, and a spiral inductor L ₂ branched from the inductor L ₃ ,
Resonant capacitor C ₄ is connected in parallel, it constitutes the equivalent circuit of FIG.

As described above, the above-described multilayer structure makes it possible to reduce the size of the capacitance portion and to form a very small filter.

Next, the main part of the present invention will be described. An auxiliary ground electrode 40 is formed on the entire lower surface of the insulating substrate 1 disposed at the lowermost layer. Then, the ground electrode 26 of the upper conductive layer 21 is connected to the insulating substrate 1, the dielectric thin film layer 1
0 and conductive holes (conductive paths) formed through the insulating layer 20
A connection is made to the auxiliary ground electrode 40 via 41. In this case, the conduction hole 41 is connected to the edge portion 5 but is not connected to other conductive layers of each layer. As described above, the auxiliary ground electrode 40 is formed on the lower surface of the insulating substrate 1 which has been conventionally solid, and is connected to the ground electrode 26 on the uppermost layer. Spread significantly.

In the above-described configuration, the auxiliary ground electrode 40 and the ground electrode 26 are connected by the conduction hole 41. However, as shown in FIG.
And applying a conductive material along the side edges of the insulating layer 20,
Thus, the conductive path 50 may be formed.

[0019]

As described above, in the LC bandpass filter of the present invention, the auxiliary ground electrode is formed on the lower surface of the insulating substrate provided on the lowermost layer, and the ground electrode formed on the upper conductive layer is
Since the ground electrode is connected to the auxiliary ground electrode via the conductive path formed in the thickness direction, the area of the ground electrode increases, external noise can be cut off, and the filtering characteristics are stabilized. For this reason,
There is an excellent effect that the filtering characteristics can be improved without impairing the miniaturization of the LC bandpass filter.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of an LC bandpass filter according to the present invention.

FIG. 2 is a partial longitudinal side view showing a conduction path 50 having another configuration.

FIG. 3 is an equivalent circuit diagram.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Insulating substrate 2 Lower conductive layer 3a, 3b Common capacitor electrode 10 Dielectric thin film layer 11 Intermediate conductive layer 12a, 12b Other-side capacitor electrode 13a, 13b Other-side capacitor electrode 20 Insulating layer 21 Upper conductive layer 22a, 22b Input / output electrode 24 Coupling electrode 26 ground electrode L ₃ inductor L ₁ , L ₂ spiral inductor C ₁ , C ₂ input / output capacitor C ₃ , C ₄ resonance capacitor S ₁ capacitor formation area S ₂ inductor formation area 40 auxiliary ground electrode 41 conduction hole 50 Conductive path

Claims (2)

[Claims] An upper conductive layer provided on an uppermost layer thereof, at least a ground electrode, and an auxiliary ground electrode formed on a lower surface of an insulating substrate provided on a lowermost layer;
An LC bandpass filter, wherein the ground electrode of the upper conductive layer is connected to an auxiliary ground electrode via a conductive path formed in a thickness direction. 2. A lower conductive layer 2 is formed on the surface of an insulating substrate 1 serving as a lowermost layer, and two common capacitor electrodes 3a and 3b are provided on the lower conductive layer 2 in parallel. A dielectric thin-film layer 10 is formed on the dielectric thin-film layer 10, and an intermediate conductive layer 11 is formed on the dielectric thin-film layer 10. An input / output capacitor C is provided on the intermediate conductive layer 11 at a position facing the common capacitor electrode 3a. _1, the other side capacitor electrode 12a of the resonance capacitor C _3, the 13a provided respectively, the common capacitor electrode 3b
The other side capacitor electrodes 12b and 13b of the input / output capacitor C ₂ and the resonance capacitor C ₄ are provided on the portion opposed to, and the insulating layer 20 is further provided on the intermediate conductive layer 11. , An upper conductive layer 21, and a ground electrode 26 and the ground electrode 2
An inductor L _1, L ₂ extending from 6, further, the input capacitor C _1, C ₂ of the other side capacitor electrodes 12a, 12b and respectively connected to input and output electrodes 22a, 22
b, the ends of the inductors L ₁ and L ₂ are connected to the common capacitor electrodes 3 a and 3 b of the lower conductive layer 2, respectively, and the ground electrode 26 is connected to the other capacitor electrode of the lower conductive layer 2. 13a, 1
3b, and an auxiliary ground electrode 40 is formed on the lower surface of the insulating substrate 1 disposed on the lowermost layer.
2. The LC bandpass filter according to claim 1, wherein the first and second electrodes are connected to an auxiliary ground electrode via a conductive path formed in the thickness direction.