JP4245265B2 - Multilayer wiring board having a plurality of filters - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention belongs to a multilayer wiring board having a plurality of filters, particularly a multilayer wiring board having a composite filter of a triplate structure multilayer filter and a surface acoustic wave filter.
[0002]
[Prior art]
With the recent development of mobile communications, the frequency band used has increased to the quasi-microwave region. For example, in systems such as “PCS” in the United States and “DCS” in Europe, the conventional 800 MHz band and one of the quasi-microwaves are used. .8-1.9 GHz dual band is being used.
[0003]
In these dual-band mobile communication devices, a duplexer that demultiplexes two frequency bands is used in addition to a filter of each frequency band. A duplexer combined with a laminated dielectric filter is generally used. On the other hand, a surface acoustic wave filter (hereinafter referred to as a SAW filter) is used as a filter in each frequency band in addition to a dielectric filter.
[0004]
FIG. 8 is a block diagram showing a filter configuration of a conventional mobile communication device. After the duplexer 21, 800 MHz band filters 22a and 22b and 1.8 to 1.9 GHz band filters 23a and 23b are separately provided. It is arranged as a body part. Each frequency band filter is a multilayer dielectric filter or a composite filter of a multilayer dielectric filter and a SAW filter.
[0005]
Of these, an arrangement example of the duplexer 21 and the filters 23a and 23b is shown as a perspective view in FIG. In FIG. 9, a duplexer 115 and a dielectric block 101 corresponding to the duplexer 21 of FIG. 8 are mounted on a printed circuit board 100 made of epoxy resin or the like. The duplexer 115 has one terminal 121 connected to an unillustrated antenna, and the other terminal 123b connected to the terminal 123a of the laminated dielectric filter that becomes the filter 23a in the dielectric block 101, and remains. The terminal 122 is connected to another filter (22 in FIG. 8) not shown.
[0006]
The dielectric block 101 is formed by laminating a plurality of dielectric layers, forming strip lines, internal wirings, internal electrodes, etc. between the layers, and forming ground electrodes 102, 103 over almost the entire main surface and end surface, and at predetermined locations. A cavity 112 is provided. In relation to FIG. 8, a plurality (five in the figure) strip lines 105 are formed side by side between the input / output electrodes 109 and 110 and the coupling electrode 108 inside the dielectric block 101, and the filter 23a in FIG. A corresponding multilayer dielectric filter is provided, and a SAW filter 113 serving as the filter 23b of FIG. The input / output terminals 124 and 125 are connected to a receiving circuit (not shown).
[0007]
[Problems to be solved by the invention]
In the conventional communication device, as described above, the duplexer and the filter of each frequency band are separate components and are connected on the printed circuit board. For this reason, there is a problem that reflection due to impedance mismatch occurs at each connection portion, and transmission loss as a total of the duplexer and the filter increases. In addition, the dual band increases the number of filters, and as the area occupied by the filters increases, the entire communication device is obstructed.
[0008]
SUMMARY OF THE INVENTION An object of the present invention is to provide a multilayer wiring board having a plurality of small, low-loss, high-attenuation filters, particularly a multilayer wiring board having a duplexer and filters for each frequency band. .
[0009]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides:
Multilayer wiring having a dielectric block having a plurality of dielectric layers are laminated, and a cavity formed in the stacking direction of the dielectric layer from a portion of the principal surface of the dielectric block for mounting the electronic component In the substrate,
The lower dielectric layers of the cavity a interlayer dielectric layer that does not form the cavity, a low-pass filter including a stripline and a capacitor component, connected to one electrode of the capacitive component is in the stripline is a b-pass filter through said lower dielectric layer connected to the other electrode there over the ground potential between,
Between adjacent dielectric layer adjacent to the cavity a interlayer dielectric layer that forms the cavity, and the strip line short rather one end than the strip line is connected to the ground potential and the capacitive component of the low-pass filter a high-pass filter including the capacitor one electrode of the component is connected to the short strip line, through said adjacent dielectric layers other electrode and connected to high-pass filter to the input circuit between < It is characterized by providing .
[0010]
Conventionally, a portion below the cavity or adjacent to the cavity among the layers of the dielectric layer is a dead space that exists to form the cavity. On the other hand, the conductor length of the strip line constituting the filter varies depending on the frequency band. Therefore, according to the present invention, a low-pass filter that requires a long strip line and a predetermined capacitance component at the lower part of the cavity that can secure a relatively large area, and a short strip line and a predetermined capacitance component adjacent to a cavity with a small area are configured. A high-pass filter that can be used was formed to effectively use the dead space. Accordingly, it is possible to avoid an increase in the size of the entire communication device as the number of filters increases.
[0011]
In the multilayer wiring board of the present invention, the in a plan view seen from above the cavity has been arranged so as to overlap a part of the low-pass filter and the high pass filter, among the surfaces including a bottom surface of the cavity, before Symbol lowpass filter as said to form a substantially entire surface ground conductor regions and the high-pass filter overlap is one preferred configuration.
[0012]
By forming a ground conductor necessary for the electronic component over the entire overlap area between the low-pass filter and the high-pass filter, it is possible to separate the upper and lower filters and serve as a shield structure that eliminates mutual interference. Furthermore, it is possible to prevent breakage of the electronic component by disposing it in the cavity.
[0013]
Another preferable configuration is a plurality of dielectric filters that are stacked dielectric filters at positions between the dielectric layers that do not overlap with the two low-pass filters and the high-pass filter in a plan view as viewed from above the cavity . A strip line is formed. This is because the distance between the connection between the filter of each frequency band connected to the duplexer and the duplexer is shortened, and the transmission loss is remarkably reduced.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment in which the multilayer wiring board of the present invention is applied to a duplexer and a filter of each frequency band will be described with reference to the drawings. FIG. 1 is a block diagram illustrating a configuration of a duplexer 21 including a low-pass filter 17 and a high-pass filter 18 and filters 22a, 22b, 23a, and 23b in each frequency band. The filters 22a and 22b are 800 MHz band filters, and the filter 23 is a 1.8 to 1.9 GHz band filter, which are parts integrated with the duplexer 21 unlike conventional ones.
[0015]
2 is a perspective view showing a part of the duplexer 21 and the filters 23a and 23b, FIG. 3 is a plan view, FIG. 4 is a sectional view taken along line AA 'in FIG. 3, and FIG. .
The duplexer 21 and the filter 23a are configured in a single dielectric block 1 as will be described in detail below, and the filter 23b is disposed in the cavity 12 provided on the main surface on one side of the dielectric block 1. It is housed as a SAW filter 13.
[0016]
The dielectric block 1 is formed by laminating nine dielectric layers 1a to 1i each having a predetermined conductor formed on the main surface. Each of the dielectric blocks 1 is provided on a large area adjacent to one side of the cavity 12 between predetermined layers. Five strip lines 5a, 5b,... 5e are formed side by side as resonators and a filter 23a as a whole. Although not shown, a ground electrode is formed in the regions of both main surfaces of the dielectric block facing all the strip lines 5a to 5e, and one end of each of the strip lines 5a to 5b is short-circuited to the ground electrode. Is open.
[0017]
Above the strip line 5a located at the end opposite to the cavity 12, an input / output electrode 9 is formed in a twisted arrangement with the strip line and extends to the end face of the dielectric block 1. Further, the internal wiring 10 is similarly formed in a twisted arrangement above the strip line e located at the end on the cavity 12 side, and is connected to the high-pass filter 18 via a connection point 27 described later. On the other hand, an inter-resonator coupling electrode 8 is formed below the five strip lines 5a to 5e in a direction perpendicular to the strip lines. The ground electrode 2 and the ground electrode 3 are formed on almost all main surfaces and end surfaces of the dielectric block 1 except for the terminal portions, respectively, and one ends of the strip lines 5 a to 5 e are short-circuited with the ground electrode 3. However, one end of the strip lines 5a to 5e may be short-circuited to the ground electrode 2 via a via-hole conductor (not shown) instead of short-circuiting to the ground electrode 3.
[0018]
A low-pass filter 17 and a high-pass filter 18 shown as an exploded perspective view in FIG. 6 and an equivalent circuit diagram in FIG. 7 are arranged in the narrow area portion adjacent to the lower side of the cavity 12 and the other side of the cavity 12 of the dielectric block 1. ing. The low-pass filter 17 is designed to pass the 800 MHz band, and the high-pass filter 18 is designed to pass the 1.8 to 1.9 GHz band.
[0019]
That is, the cavity 12 is a space surrounded by the rectangular through-holes in which the dielectric layers 1 a to 1 f are punched and the dielectric layer 1 g, and a capacitance between the dielectric layers 1 a and 1 b in a portion adjacent to the cavity 12. Between the electrode 33a and the dielectric layers 1b and 1c, between the capacitive electrode 33b and the dielectric layers 1c and 1d, one end is connected to the ground electrode 3, and the strip line 34 is bent in a relatively short bowl shape and between the dielectric layers 1d and 1e. The capacitor electrode 35a is formed between the capacitor electrode 35a and the dielectric layers 1e and 1f.
[0020]
The strip line 34 becomes an inductor component of the high-pass filter 18, and a predetermined capacitance component is generated by the capacitive electrodes 33 a and 33 b and the dielectric layer 1 b sandwiched between these electrodes, and the open end of the strip line 34 in the high-pass filter 18. And the antenna connection terminal 25. Similarly, the capacitive electrodes 35 a and 35 b and the dielectric layer 1 e sandwiched between these electrodes serve as a coupling capacitor 35 between the open end of the strip line 34 and the filter connection terminal 27. The capacitive electrode 33b, the strip line 34, and the capacitive electrode 35a are connected via a via-hole conductor 36 located near the open end of the strip line 34.
[0021]
Next, a ground electrode 16 is formed on the main surface of the dielectric layer 1g serving as the bottom surface of the cavity 12 over almost the entire surface excluding the connection electrodes 14 and 15 of the SAW filter 13 and these electrode forming portions. Accordingly, the input / output terminals (not shown) of the SAW filter 13 are connected to the connection electrodes 14 and 15, and the ground terminal is connected to the ground electrode 16.
[0022]
Subsequently, a strip line 31 meandering relatively long from the antenna connection terminal 25 to the filter connection terminal 26 is formed between the dielectric layers 1g and 1h, and a capacitive electrode 32a is formed between the dielectric layers 1h and 1i. The strip line 31 becomes an inductor component of the low-pass filter 17, and a capacitance component that becomes the coupling capacitor 32 is generated by the capacitance electrode 32 a and the ground electrode 2 and the dielectric layer 1 i on the back surface of the dielectric layer 1 i. The strip line 31 and the capacitor electrode 32 a are connected via a via-hole conductor 37 located near the filter connection terminal 26.
[0023]
The reason why the high-pass filter 18 is formed in a relatively narrow portion adjacent to the cavity 12 and the low-pass filter 17 is formed in a relatively wide portion below the cavity 12 is as follows. As shown in FIG. 7, the low-pass filter 17 includes a strip line 31 and a capacitor 32, which are inductor components. Since the frequency is low, both the inductor component and the capacitance component must be increased, and a large area is required. And On the other hand, the high-pass filter 18 includes capacitors 33 and 35 and a strip line 34, and has a high frequency. Therefore, when a high-frequency technique is used, the inductor component and the capacitance component are small, and a small area is sufficient.
[0024]
Although the filters 22a and 22b are not shown in FIG. 2 and subsequent figures, a laminated dielectric filter can be used for both of them, so that they can be accommodated in the dielectric block 1 similarly to the filter 23a.
[0025]
The dielectric layers 1a to 1i are made of a dielectric ceramic material and an oxide or low-melting glass material that enables low-temperature firing. Examples of dielectric ceramic materials include BaO—TiO ₂ , Ca—TiO ₂ , MgO—TiO _2, etc. Examples of oxides that enable low-temperature firing include BiVO ₄ , CuO, Examples include Li ₂ O and B ₂ O ₃ . Dielectric layers 1a to 1i have a thickness of about 50 to 300 μm per layer.
[0026]
Each strip line, each capacitor electrode, via-hole conductor, and the ground electrode between layers are screen-printed in a predetermined shape with a conductor material mainly composed of Ag, Ag-Pd, Cu, etc. on each green sheet to be the dielectric layers 1a to 1i. And it is formed by baking simultaneously with a dielectric material layer. The ground electrode 2 and the ground electrode 3 are made of a conductive material mainly composed of Ag, Cu or the like (Ag simple substance or Ag alloy such as Ag-Pd, Ag-Pt, Cu simple substance or Cu alloy) in the fired body. It is formed by screen printing in a predetermined shape and firing again. In addition to the metal component, a glass component is added to these conductor materials as necessary.
[0027]
In this embodiment, since the duplexer 21, the filter 23a (laminated dielectric filter) and the filter 23b (SAW filter) are housed in a single dielectric block 1, the filter of each frequency band is separated from the filter. The size can be reduced as compared with a conventional configuration using a duplexer. In particular, since the dead space at the lower part of the cavity 12 and adjacent position provided for arranging the SAW filter 13 is utilized as the low-pass filter 17 and the high-pass filter 18 of the duplexer 21, the volume of the dielectric block 1 is reduced. There is almost no need to change.
[0028]
In addition, since the connection distance between the duplexer and each frequency band filter is short, there is less reflection loss compared to the conventional configuration in which the duplexer and each frequency band filter are connected via a strip line on the printed circuit board. A composite filter with good performance as a whole can be obtained. Further, since the low-pass filter 17 and the high-pass filter 18 can be completely separated by the ground electrode 16 necessary for the SAW filter 13, a duplexer with good performance can be formed without mutual interference between the filters.
[0029]
【The invention's effect】
As described above, in the multilayer wiring board according to the present invention, the filters of each frequency band are formed at the lower part of the cavity and the adjacent positions, respectively, which were set as dead spaces, so the number of filters as separate parts is reduced and the whole is reduced in size. Therefore, it is possible to provide a composite filter with good performance and low reflection loss.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a filter configuration of a multilayer wiring board according to an embodiment.
FIG. 2 is a perspective view showing a multilayer wiring board according to the embodiment.
FIG. 3 is a plan view of the same.
4 is a cross-sectional view taken along the line AA ′ of FIG.
FIG. 5 is a sectional view taken along the line BB ′.
6 is an exploded perspective view showing portions of a low-pass filter 17 and a high-pass filter 18 constituting the duplexer of the multilayer wiring board. FIG.
FIG. 7 is an equivalent circuit diagram of the duplexer.
FIG. 8 is an equivalent circuit diagram of a conventional duplexer.
FIG. 9 is a perspective view showing a combination of a conventional duplexer and a filter.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1,101 Dielectric block 2, 3, 16, 102, 103 Ground electrode 5a-5e Strip line 8, 108 Resonator coupling electrode 9, 109, 10, 110 Input / output electrode 12, 112 Cavity 13, 113 SAW filter 21, 115 Demultiplexer 17 Low-pass filter 18 High-pass filter

Claims (3)

Multilayer wiring having a dielectric block having a plurality of dielectric layers are laminated, and a cavity formed in the stacking direction of the dielectric layer from a portion of the principal surface of the dielectric block for mounting the electronic component In the substrate,
The lower dielectric layers of the cavity a interlayer dielectric layer that does not form the cavity, a low-pass filter including a stripline and a capacitor component, connected to one electrode of the capacitive component is in the stripline is a b-pass filter through said lower dielectric layer connected to the other electrode there over the ground potential between,
Between adjacent dielectric layer adjacent to the cavity a interlayer dielectric layer that forms the cavity, and the strip line short rather one end than the strip line is connected to the ground potential and the capacitive component of the low-pass filter a high-pass filter including the capacitor one electrode of the component is connected to the short strip line, through said adjacent dielectric layers other electrode and connected to high-pass filter to the input circuit between < multi-layer wiring board, characterized in that it comprises a br />. It is arranged so as to overlap a portion of the low-pass filter and the high pass filter in a plan view seen from above the cavity, of the plane containing the bottom surface of the cavity overlaps the previous SL low pass filter and the high pass filter 2. The multilayer wiring board according to claim 1, wherein a ground conductor is formed on substantially the entire area. A plurality of strip lines serving as a multilayer dielectric filter are formed at a position between the dielectric layers and in a plan view as viewed from above the cavity so as not to overlap any of the two types of low-pass filters and high-pass filters. The multilayer wiring board according to claim 1 or 2.

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