JP2004254257A - Wiring board with built-in low-pass filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wiring board with a built-in low-pass filter in which double or triple higher harmonic wave of a pass-band of a surface acoustic wave (SAW) filter element can be attenuated over a wide band and a low-pass filter that reduces a loss, can be realized by connecting the built-in low-pass filter to a transmission output side of the SAW filter element. <P>SOLUTION: The wiring board with the built-in low-pass filter is provided with a substrate configured by laminating a plurality of dielectric layers 1-5, a cavity 6 formed on an upper surface of the substrate for housing the SAW filter element, and the low-pass filter built in the substrate and composed of strip lines 12, 13, a ground electrode 7 and ground capacitive electrodes 10, 11 electrically connected to a transmission input side of the SAW filter element. The higher harmonic wave can be attenuated over the wide band and the low-pass filter of a low loss can be realized. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a multilayer wiring board containing a surface acoustic wave filter element having a filter, and in particular, a wiring board with a built-in low-pass filter having a low-pass filter for attenuating an electric signal having a frequency higher than a pass band of the surface acoustic wave filter element. It is about.
[0002]
[Prior art]
As the demand for miniaturization, higher density, and lower cost of electronic devices used for mobile phones and mobile communications has increased, the number of components has been reduced by incorporating filters into the board, and the size and density have been reduced. There is a wiring board to be realized.
[0003]
As such a wiring board, for example, Japanese Unexamined Patent Application Publication No. 11-147571 discloses a laminate formed by laminating a dielectric layer and a conductor layer, forming a concave portion on at least one main surface of the laminate, and forming an external portion on at least a side surface. A composite filter in which terminals are provided, an LC filter is constituted by an inductance element and a capacitance element formed by a conductor layer of the laminate, a surface acoustic wave filter is disposed in a concave portion of the laminate, and the concave portion is sealed by a cap. Wherein two of the external terminals serve as input terminals of the surface acoustic wave filter and the LC filter, and two of the external terminals serve as output terminals of the surface acoustic wave filter and the LC filter, respectively. A composite filter is disclosed in which the wave filter and the LC filter are electrically independent without being connected in the laminate. There.
[0004]
According to this, since the surface acoustic wave filter and the LC filter are integrated via one laminated body, the number of parts can be reduced, the assembly process can be facilitated, and almost the same as the case of discrete chip parts And a composite filter having two functions of a surface acoustic wave filter and an LC filter, having a size substantially equal to that of a conventional surface acoustic wave filter which is a discrete chip component. Since the surface acoustic wave filter and the LC filter have independent input and output terminals, other electronic components can be inserted between the surface acoustic wave filter and the LC filter, and the composite filter is mounted. That is, the degree of freedom in designing a wireless device can be expanded.
[0005]
For example, if both the surface acoustic wave filter and the LC filter are band-pass filters, and the other filter is disposed after one of the filters, the amount of attenuation for frequencies other than these pass-bands can be increased. Therefore, the attenuation can be increased over a relatively wide band.
[0006]
When the pass band of the LC filter includes the pass band of the surface acoustic wave filter, an LC filter having a pass band wider than that of the surface acoustic wave filter may be disposed after the surface acoustic wave filter having a narrow pass band. Since the high-frequency signal passes through the surface acoustic wave filter and then passes through the LC filter, the attenuation of frequencies other than the pass band of the surface acoustic wave filter can be further increased, and the attenuation can be further increased over a relatively wide band. be able to.
[0007]
In addition, when the pass band of the surface acoustic wave filter and the pass band of the LC filter are not overlapped, the pass band can be used when different frequencies are used, and the degree of freedom of use can be expanded.
[0008]
Further, when the surface acoustic wave filter and the LC filter constituting the composite filter are used for the filter constituting the transmission side radio signal section or the reception side radio signal section of the radio apparatus, the number of parts constituting the radio apparatus is reduced. The size of the wireless device can be reduced.
[0009]
[Patent Document 1]
JP-A-11-145577
[0010]
[Problems to be solved by the invention]
However, in the composite filter disclosed in Japanese Patent Application Laid-Open No. H11-1475771, the surface acoustic wave filter and the LC filter are electrically independent without being connected inside the laminate, and the input terminal and the output terminal are provided. Therefore, by incorporating these filters inside the laminate, the number of components can be reduced and the size can be reduced. However, when the surface acoustic wave filter and the LC filter are connected inside the laminate, In comparison, there is a problem that the number of input terminals and output terminals increases.
[0011]
Further, when both the surface acoustic wave filter and the LC filter are band-pass filters, a sufficient amount of attenuation near the pass band can be easily obtained due to the characteristics of the band-pass filter. There is also a problem that it is not suitable for use in attenuating harmonics twice or three times the pass band generated by a power amplifier over a wide band.
[0012]
The present invention has been devised in view of the above-described problems of the related art, and has as its object to form a low-pass filter inside a base body made of a laminated body, and to reduce the transmission output of a surface acoustic wave filter element. By connecting this low-pass filter to the side, the number of connection terminals with the outside can be reduced, and the low-pass filter can attenuate the high-frequency band higher than the pass band of the surface acoustic wave filter element, so that the transmission of the wireless device can be reduced. Wiring with built-in low-pass filter that can attenuate harmonics twice or three times the pass band generated by the power amplifier required on the side over a wide band, and realize a low-pass filter with low loss inside the substrate. It is to provide a substrate.
[0013]
[Means for Solving the Problems]
A wiring board with a built-in low-pass filter according to the present invention includes a base formed by laminating a plurality of dielectric layers, a cavity formed on an upper surface of the base for accommodating a surface acoustic wave filter element, and a wiring board built in the substrate. And a low-pass filter electrically connected to the transmission input side of the surface acoustic wave filter element.
[0014]
In the wiring board with a built-in low-pass filter according to the present invention, the low-pass filter has a strip line, a ground electrode and a ground capacitance electrode forming a ground capacitance, and the ground electrode and the ground capacitance. The electrode is arranged on the lower surface side from the bottom surface of the cavity, and the strip line is arranged at a part other than the lower part of the cavity.
[0015]
Further, the wiring board with a built-in low-pass filter according to the present invention, in each of the above-mentioned configurations, includes a strip line for phase adjustment, which is built in the base and electrically connected to the surface acoustic wave filter element. It is assumed that.
[0016]
Further, in the wiring board with a built-in low-pass filter according to the present invention, in each of the above-described configurations, the strip line is arranged on the upper surface side of the base with respect to the ground electrode and the ground capacitance electrode.
[0017]
Further, in the wiring board with a built-in low-pass filter of the present invention, in each of the above-described configurations, the strip line and the phase adjusting strip line are respectively arranged at portions of the base opposed to each other across the cavity. It is assumed that.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a wiring board with a built-in low-pass filter of the present invention will be described with reference to the drawings.
[0019]
FIG. 1 is an exploded perspective view showing an example of an embodiment of a wiring board with a built-in low-pass filter according to the present invention. In FIG. 1, 1 is a first dielectric layer, 2 is a second dielectric layer, 3 is a third dielectric layer, 4 is a fourth dielectric layer, 5 is a fifth dielectric layer, 6 Is a cavity, 7 is a first ground electrode, 8 is a second ground electrode, 9 is a strip line for phase adjustment, 10 is a first ground capacitance electrode, 11 is a second ground capacitance electrode, and 12 is a first ground capacitance electrode. Strip line, 13 is a second strip line, 14 is a first through conductor, 15 is a second through conductor, 16 is a third through conductor, 17 is a fourth through conductor, and 18 is housed in the cavity. A transmission side output terminal electrically connected to the transmission input side of the surface acoustic wave filter element, and 19 is a transmission side input terminal electrically connected to the transmission output side of the surface acoustic wave filter element housed in the cavity. .
[0020]
In the example shown in FIG. 1, the first ground electrode 7 formed on the lower surface of the first dielectric layer 1 and the first dielectric layer 1 and the second dielectric layer 2 are formed between the first dielectric layer 1 and the second dielectric layer 2. Let C1 be the ground capacitance generated between the first ground capacitance electrode 10 and the first ground electrode 7 formed on the lower surface of the first dielectric layer 1, and the first dielectric layer 1 and the second A ground capacitance generated between the second ground capacitance electrode 11 formed between the dielectric layers 2 is defined as C2, and a ground capacitance formed between the third dielectric layer 3 and the fourth dielectric layer 4 is defined as C2. 1 strip line 12, a second strip line 13 formed between the fourth dielectric layer 4 and the fifth dielectric layer 5, and a first strip line 12 and a second strip line 13. This is caused by the first penetrating conductor 14 that connects one end to the other by penetrating the fourth dielectric layer 4. When the conductance is L1, the other end of the first strip line 12 is connected to the first ground capacitance electrode 10 via the second through conductor 15, and the other end of the second strip line 13 is the third end. By being connected to the second ground capacitance electrode 11 via the through conductor 16, a π-type low-pass filter composed of L1, C1, and C2 is configured.
[0021]
Further, a first ground electrode 7 formed on the lower surface of the first dielectric layer 1 between the first dielectric layer 1 and the second dielectric layer 2, and the first dielectric layer 1 A phase shifter S is formed by a phase adjusting strip line 9 sandwiched between a second ground electrode 8 formed between the second dielectric layers 2. The transmission-side output terminal 18 is connected to the output side of the low-pass filter, that is, the connection point between L1 and C2 via the third through conductor 16, and the transmission-side input terminal 19 is connected to the phase adjustment strip line 9 through the fourth through-hole. Each is electrically connected via a conductor 17.
[0022]
According to such an example of the wiring board with a built-in low-pass filter of the present invention shown in FIG. 1, the equivalent circuit diagram is as shown in FIG. In FIG. 2, a portion surrounded by a broken line is a portion corresponding to the equivalent circuit of the example of the wiring board with a built-in low-pass filter of the present invention shown in FIG.
[0023]
The capacitances C1 and C2 are adjusted by the first to fifth dielectric layers 1 to 5 and the first ground electrode 7, the first and second ground capacitance electrodes 10 and 11, and the first and second By adjusting the inductance L1 by the strip lines 12 and 13, a wiring board having a built-in low-pass filter having desired low-pass characteristics can be obtained.
[0024]
Further, according to the wiring board with a built-in low-pass filter of the present invention, a wiring board with a built-in low-pass filter electrically connected to the transmission-side output terminal 18 electrically connected to the transmission input side of the surface acoustic wave filter element. As a result, the number of input terminals and output terminals of the wiring board with a built-in low-pass filter can be reduced to one, and the number of terminals required when the wiring board with a built-in low-pass filter is secondarily mounted on another board is reduced. Since the size of the base can be reduced, the size of the base is not limited by the number of terminals, the size of the wiring board with a built-in low-pass filter can be easily reduced, and the distance between the terminals can be increased. The ratio can also be improved. Further, since the terminal area per terminal can be increased, mounting reliability can be improved.
[0025]
In addition, by electrically connecting a low-pass filter having a higher cut-off frequency than the pass band of the surface acoustic wave filter element to the transmission input side of the surface acoustic wave filter element, the band can be broadened in a higher frequency band than the pass band of the surface acoustic wave filter element. It compensates for the problem of the conventional composite filter, which cannot take a sufficient amount of attenuation, and can obtain a sufficiently high amount of attenuation in a high frequency band. For example, harmonics twice or three times the pass band of a power amplifier are also effective. Can be attenuated. In addition, since the low-pass filter as described above is built in the base, the number of components can be reduced.
[0026]
Also, the ground electrode 7 and the ground capacitance electrodes 10 and 11 forming the ground capacitances C1 and C2 of the low-pass filter are arranged on the lower surface side of the base from the bottom surface of the cavity 6, and the inductance L1 of the low-pass filter is located below the cavity 6 of the base. By arranging them around the cavity 6 other than the above, the distance between the ground electrodes 7 and the ground capacitance electrodes 10 and 11 and the strip lines 12 and 13 can be increased, and the stray capacitance of the strip lines 12 and 13 can be reduced. And the interaction between the ground electrode 7 and the ground capacitance electrodes 10 and 11 and the inductance L1 can be reduced, so that a low-loss low-pass filter can be configured. In addition, a large capacitance is formed by disposing the ground capacitors C1 and C2, which require a relatively large area in the low-pass filter, on the lower surface side of the bottom surface of the cavity 6 having the largest area inside the wiring board with a built-in low-pass filter. Therefore, it is not necessary to newly increase the number of dielectric layers or to make the dielectric layer 1 between the ground electrode 7 and the ground capacitance electrodes 10 and 11 extremely thin.
[0027]
Further, by incorporating a phase adjusting strip line 9 which is electrically connected to the transmission output side of the surface acoustic wave filter element and functions as a phase shifter S for adjusting the phase of a signal, the surface acoustic wave filter element The phase on the output side can be adjusted appropriately. In addition, when the phase adjusting strip line 9 is disposed on the lower surface side of the base from the bottom surface of the cavity 6, the phase adjusting strip line 9 having a sufficient length can be incorporated without making the base unnecessarily large.
[0028]
In addition, by disposing the strip lines 12 and 13 at positions other than the lower part of the cavity 6 of the base and by disposing them on the upper surface side of the base with respect to the ground electrode 7 and the ground capacitance electrodes 10 and 11, the ground electrode 7 and the ground capacitance Since the distance from the electrodes 10 and 11 can be increased, the stray capacitance of the inductance L1 can be further reduced, and the distance between the ground electrode 7 and the ground capacitance electrodes 10 and 11 can be further increased. Since the interaction with L1 can be reduced, a low-loss low-pass filter can be configured.
[0029]
FIG. 3 is a diagram showing frequency characteristics of the low-pass filter in the example of the wiring board with a built-in low-pass filter of the present invention shown in FIG. In FIG. 3, the horizontal axis represents frequency (unit: GHz), the vertical axis represents signal transmission amount S (2, 1) (unit: dB) on the transmission side, and the solid characteristic curve represents the wiring with built-in low-pass filter of the present invention. The frequency characteristic when the surface acoustic wave filter element is mounted on the substrate, and the characteristic curve indicated by the broken line indicates the frequency characteristic of only the surface acoustic wave filter element. From the results shown in FIG. 3, according to the wiring board with a built-in low-pass filter of the present invention, the pass band of the surface acoustic wave filter element (1.85 GHz to 1.85 GHz) is obtained due to the signal attenuation effect of the built-in low-pass filter at high frequencies. It can be seen that a large amount of attenuation is obtained on the high frequency side (99 GHz) as compared with the frequency characteristic of only the surface acoustic wave filter element.
[0030]
The low-pass filter in the wiring board with a built-in low-pass filter of the present invention, for example, when the dielectric layer is made of ceramics, performs a predetermined perforation process on a dielectric ceramic green sheet to be each dielectric layer after firing. It is manufactured by applying a conductive paste to the pattern shape of each electrode, a through hole serving as a through conductor, a side surface of a green sheet, and the like, laminating these, and firing. Alternatively, if the dielectric layer is made of a resin such as a fluororesin or a glass epoxy resin / polyimide resin, a resin substrate is used, and the copper foil adhered to the surface is etched to form each electrode pattern. It is manufactured by forming a via conductor for interlayer connection and performing lamination pressing.
[0031]
The dielectric layers including the first to fifth dielectric layers 1 to 5 are made of ceramic materials such as alumina ceramics and mullite ceramics, inorganic materials such as glass ceramics, or ethylene tetrafluoride resin (polyethylene). Tetrafluoroethylene; PTFE) / tetrafluoroethylene-ethylene copolymer resin (tetrafluoroethylene-ethylene copolymer resin; ETFE) / tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin (tetrafluoroethylene-perfluteroalkyl) Fluororesins such as vinyl ether copolymer resin (PFA) and resin materials such as glass epoxy resin and polyimide are used. In addition, the first and second ground electrodes 7.8, the first and second ground capacitance electrodes 10 and 11, the first and second strip lines 12 and 13, the phase adjustment strip line 9, the transmission-side output terminal 18. The transmission-side input terminal 19 has a conductor layer of a metal material for transmitting a high-frequency signal, for example, a Cu layer, a Mo-Mn metallized layer with a Ni plating layer and an Au plating layer adhered, and a W metallization. Ni-plated layer and Au-plated layer adhered on the layer-Cr-Cu alloy layer-Ni-plated layer and Au-plated layer adhered on the Cr-Cu alloy layer-Ta ₂ Ni-Cr alloy layer and Au plating layer deposited on N layer-Pt layer and Au plating layer deposited on Ti layer-Pt layer and Au plating on Ni-Cr alloy layer A layer having a layer attached thereto is used, and is formed by a thick film printing method, various thin film forming methods, a plating method, or the like. The thickness and width are set according to the frequency of the high frequency signal to be transmitted, the application, and the like.
[0032]
Next, FIG. 4 shows another example of the embodiment of the wiring board with a built-in low-pass filter of the present invention in an exploded perspective view similar to FIG. 4, 1a is a first dielectric layer, 2a is a second dielectric layer, 3a is a third dielectric layer, 4a is a fourth dielectric layer, 5a is a fifth dielectric layer, 6a Is a cavity, 7a is a first ground electrode electrode, 8a is a second ground electrode electrode, 9a is a strip line for phase adjustment, 10a is a first ground capacitance electrode, 11a is a second ground capacitance electrode, and 12a is a second ground capacitance electrode. One strip line, 13a is a second strip line, 14a is a first through conductor, 15a is a second through conductor, 16a is a third through conductor, 17a is a fourth through conductor, and 18a is housed in the cavity. A transmission-side output terminal electrically connected to the transmission input side of the surface acoustic wave filter element to be formed, and a transmission-side input terminal 19a electrically connected to the transmission output side of the surface acoustic wave filter element housed in the cavity. , 20a are capacitance electrodes
[0033]
In the example shown in FIG. 4, the first ground electrode 7a formed on the lower surface of the first dielectric layer 1a and the first dielectric layer 1a and the second dielectric layer 2a are formed between the first dielectric layer 1a and the second dielectric layer 2a. A ground capacitance generated between the first ground capacitance electrode 10a and the first ground electrode 7a formed on the lower surface of the first dielectric layer 1a, the first dielectric layer 1a and the second The ground capacitance generated between the second ground capacitance electrode 11a formed between the dielectric layers 2a is C2a, and the capacitance formed between the second dielectric layer 2a and the third dielectric layer 3a is C2a. The capacitance generated between the electrode 20a and the first ground capacitance electrode 10a formed between the first dielectric layer 1a and the second dielectric layer 2a is C3a, and the third dielectric layer 3a A first strip line 12a formed between the fourth dielectric layers 4a; The second strip line 13a formed between the layer 4a and the fifth dielectric layer 5a, one end of the first strip line 12a and one end of the second strip line 13a are connected to a fourth dielectric layer. The inductance caused by the first through conductor 14a connected by penetrating the layer 4a is defined as L1a, and the other end of the first strip line 12a is connected to the first ground capacitance electrode 10a via the second through conductor 15a. The other end of the second strip line 13a is connected to the second ground capacitance electrode 11a via the third through conductor 16a, so that a π-type low-pass filter including L1a, C1a, C2a, and C3a is formed. Is composed.
[0034]
Also, a first ground electrode 7a formed on the lower surface of the first dielectric layer 1a, between the first dielectric layer 1a and the second dielectric layer 2a, and the first dielectric layer 1a A phase shifter Sa is formed by a phase adjusting strip line 9a sandwiched between a second ground electrode 8a formed between the second dielectric layers 2a. The transmission-side output terminal 18a is connected to the output side of the low-pass filter, that is, the connection point between L1a, C2a, and C3a via the third through conductor 16a, and the transmission-side input terminal 19a is connected to the phase adjustment strip line 9a. Are electrically connected via the through conductors 17a.
[0035]
The example shown in FIG. 4 forms a parallel resonance circuit with the inductance L1a and the capacitance C3a by providing a new capacitor C3a as compared with the example shown in FIG. 1, and has a larger attenuation at a specific frequency of this parallel resonance circuit. It's about getting the amount.
[0036]
According to such an example of the wiring board with a built-in low-pass filter of the present invention shown in FIG. 4, the equivalent circuit diagram is as shown in FIG. In FIG. 5, a portion surrounded by a broken line is a portion corresponding to an equivalent circuit of the example of the wiring board with a built-in low-pass filter of the present invention shown in FIG.
[0037]
Then, the capacitances C1a to C3a are adjusted by the first to fifth dielectric layers 1a to 5a, the first ground electrode 7a, the first and second ground capacitance electrodes 10a and 11a, and the first capacitance electrode 17a. Further, by adjusting the inductance L1a by the first and second striplines 12a and 13a, it is possible to obtain a wiring board having a built-in low-pass filter having desired low-pass characteristics.
[0038]
The inductance L1a formed by the first and second strip lines 12a and 13a and the capacitance C3a formed by the first ground capacitance electrode 10a and the first capacitance electrode 20a form a parallel resonance circuit. By making the resonance frequency of the parallel resonance circuit correspond to a frequency twice or three times the pass band, it is possible to remove harmonics twice or three times the pass band.
[0039]
FIG. 6 is a diagram similar to FIG. 3, showing the frequency characteristics of the low-pass filter in the example of the wiring board with a built-in low-pass filter of the present invention shown in FIG. In FIG. 6, the horizontal axis represents the frequency (unit: GHz), the vertical axis represents the signal passing amount S (2, 1) (unit: dB) on the transmission side, and the dashed characteristic curve shows the characteristic of only the surface acoustic wave filter element. The characteristics and the solid characteristic curve show the characteristics when the surface acoustic wave filter element is mounted and the low-pass filter is electrically connected. According to the results shown in FIG. 6, according to the wiring board with a built-in low-pass filter of the present invention, the pass band (1. It can be seen that a large amount of attenuation is obtained at twice the frequency (3.7 GHz to 3.95 GHz) of 85 GHz to 1.99 GHz.
[0040]
Next, FIG. 7 shows another example of the embodiment of the wiring board with a built-in low-pass filter of the present invention in an exploded perspective view similar to FIG. In FIG. 7, 1b is a first dielectric layer, 2b is a second dielectric layer, 3b is a third dielectric layer, 4b is a fourth dielectric layer, 5b is a fifth dielectric layer, 6b Is a cavity, 7b is a first ground electrode, 8b is a second ground electrode, 9b is a strip line for phase adjustment, 10b is a first ground capacitance electrode, 11b is a second ground capacitance electrode, and 12b is a first ground capacitance electrode. A strip line, 13b is a second strip line, 14b is a first through conductor, 15b is a second through conductor, 16b is a third through conductor, and 17b is a reception input of a surface acoustic wave filter element housed in a cavity. The receiving output terminal 18b is electrically connected to the transmitting side, 18b is a transmitting output terminal electrically connected to the transmitting input side of the surface acoustic wave filter element accommodated in the cavity, and 19b is an elastic surface accommodated in the cavity. Wave filter element Transmission-side input terminal electrically connected to the signal output side, 20b is the capacitance electrodes.
[0041]
In the example shown in FIG. 4, a first ground electrode 7b formed on the lower surface of the first dielectric layer 1b and the first ground electrode 7b are formed between the first dielectric layer 1b and the second dielectric layer 2b. The ground capacitance generated between the first ground capacitance electrode 10b and C1b is defined as C1b, the first ground electrode 7b formed on the lower surface of the first dielectric layer 1b, the first dielectric layer 1b and the second The ground capacitance generated between the second ground capacitance electrode 11b formed between the dielectric layers 2b is C2b, and the capacitance formed between the second dielectric layer 2b and the third dielectric layer 3b is defined as C2b. The capacitance generated between the electrode 20b and the first ground capacitance electrode 10b formed between the first dielectric layer 1b and the second dielectric layer 2b is C3b, and the third dielectric layer 3b A first strip line 12b formed between the fourth dielectric layers 4b and a fourth dielectric layer 4b; A second strip line 13b formed between the layer 4b and the fifth dielectric layer 5b, one end of the first strip line 12b and one end of the second strip line 13b are connected to a fourth dielectric layer. The inductance generated by the first through conductor 14b connected by penetrating the layer 4b is defined as L1b, and the other end of the first strip line 12b is connected to the first ground capacitance electrode 10b through the second through conductor 15b. The other end of the second strip line 13b is connected to the second ground capacitance electrode 11b via the third through conductor 16b, so that a π-type low-pass filter including L1b, C1b, C2b, and C3b is formed. Is composed.
[0042]
Further, between the first dielectric layer 1b and the fourth dielectric layer 4b, a first ground electrode 7b formed on the lower surface of the first dielectric layer 1b, a fourth dielectric layer 4b, The phase shifter Sb is formed by the strip line 9b for phase adjustment sandwiched between the second ground electrode 8b formed between the fifth dielectric layers 5b. The transmission-side output terminal 18b is electrically connected to the output side of the low-pass filter, that is, the connection point between L1b, C2b, and C3b via the third through conductor 16b, and the reception-side output terminal 17b is electrically connected to the phase adjustment strip line 9b. Connected.
[0043]
The example shown in FIG. 7 is intended to appropriately adjust the phase on the receiving side by providing the phase shifter Sb on the receiving side as compared with the example shown in FIG.
[0044]
According to such an example of the wiring board with a built-in low-pass filter of the present invention shown in FIG. 7, the equivalent circuit diagram is as shown in FIG. In FIG. 8, a portion surrounded by a broken line is a portion corresponding to the equivalent circuit of the example of the wiring board with a built-in low-pass filter of the present invention shown in FIG.
[0045]
By arranging the first and second strip lines 12b and 13b and the phase adjusting strip line 9b at opposing portions with the cavity 6b of the base therebetween, the distance between the strip lines 12b and 13b-9b is obtained. Is sufficiently separated and the cavity 6b is interposed to improve the isolation between the low-pass filter and the phase shifter Sa, so that it is possible to obtain a wiring board incorporating a low-pass filter with less loss.
[0046]
9 is a diagram similar to FIG. 3, showing the frequency characteristics of the low-pass filter in the example of the wiring board with a built-in low-pass filter of the present invention shown in FIG. In FIG. 9, the horizontal axis represents the frequency (unit: GHz), the vertical axis represents the signal passing amount S (2, 1) (unit: dB) on the transmission side, and the characteristic curve indicated by the broken line is only for the surface acoustic wave filter element. The characteristics when the low-pass filter whose thin solid characteristic curve has a short distance between the first and second strip lines 12b and 13b and the phase adjusting strip line 9b are electrically connected to the surface acoustic wave filter element. And a low pass filter in which the first and second strip lines 12b and 13b and the phase adjusting strip line 9b are arranged at positions opposed to each other with the cavity 6b of the base therebetween. It shows the characteristics when electrically connected to. According to the results shown in FIG. 9, according to the wiring board with a built-in low-pass filter of the present invention, the pass band (1. It can be seen that a large amount of attenuation is obtained at twice the frequency (3.7 GHz to 3.95 GHz) of 85 GHz to 1.99 GHz. If the distance between the first and second strip lines 12b and 13b and the strip line 9b for phase adjustment is short, the signal on the transmission side flows to the reception side, and thus the signal passing amount S (2, 1) on the transmission side. However, by arranging the first and second strip lines 12b and 13b and the phase-adjusting strip line 9b in opposition to each other across the cavity 6b of the base, signal attenuation on the transmission side can be reduced. It turns out that you can not see it.
[0047]
It should be noted that the present invention is not limited to the above-described embodiments, and various changes may be made without departing from the spirit of the present invention. For example, according to the wiring board with a built-in low-pass filter of the present invention, the thickness of the first to fifth dielectric layers 1 to 5 and 1a to 5a, 1b to 5b can be reduced, or a high dielectric material can be used for these. By mixing a magnetic substance into the third and fourth dielectric layers 3, 4 and 3a, 4a, 3b, 4b, it is possible to further improve characteristics and reduce the size.
[0048]
Further, a shield electrode may be provided on the upper surface of the fifth dielectric layer 5, 5a, 5b, or the first to fourth through conductors 14 to 17 and 14a to 17a, and the first to third through conductors 14b to 16b may be formed. Alternatively, a connection conductor for each electrode may be formed on the side surface of the dielectric layer to electrically connect the electrodes.
[0049]
In addition, the surface acoustic wave filter element to be mounted is not limited to only the transmitting side, and the surface acoustic wave filter element at the receiving side is mounted inside the same cavity 6, 6a, 6b, or the transmitting side and the receiving side are integrated. Surface acoustic wave filter element may be mounted.
[0050]
Further, the phase adjusting strip lines 9, 9a, 9b are not limited to those arranged on the upper surface side from the bottom surfaces of the cavities 6, 6a, 6b. Even if it is arranged on the lower surface side from the bottom surface, the isolation between the low-pass filter and the phase shifter can be improved.
[0051]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to the wiring board with a built-in low-pass filter of the present invention, a base formed by laminating a plurality of dielectric layers, a cavity formed on an upper surface of the base for accommodating a surface acoustic wave filter element, and a base housed inside the base. In addition, since a low pass filter electrically connected to the transmission input side of the surface acoustic wave filter element is provided, the number of connection terminals with the outside is reduced, and the low pass filter is used for the surface acoustic wave filter element. By making the attenuation of the high frequency band larger than that of the pass band, it is possible to attenuate harmonics twice or three times the pass band generated by the power amplifier required on the transmitting side of the wireless device over a wide band. , A low-pass filter with small loss can be realized.
[0052]
For example, first to fifth dielectric layers sequentially stacked, a first ground electrode formed on the lower surface of the first dielectric layer, and an upper surface formed on the third and fourth dielectric layers. First and second strip lines, and first and second ground capacitance electrodes formed between the first dielectric layer and the second dielectric layer 2. One ends of the second strip lines are connected to each other to electrically connect the other end of the first strip line to the first ground capacitance electrode, and the other end of the second strip line is connected to the second ground capacitance electrode. The first to fifth dielectric layers, the first ground electrode, and the first ground electrode are connected to the transmission surface of the surface acoustic wave filter element and electrically connected to the transmission input side of the surface acoustic wave filter element. And the ground capacitance is adjusted by the second ground capacitance electrode. By adjusting the inductance by addition first and second strip lines, it is possible to obtain a wiring board with a built-in π-type low-pass filter having a desired low-pass characteristic.
[0053]
Further, the number of input terminals and output terminals of the wiring board with a built-in low-pass filter can be reduced to one, and the number of terminals required when the wiring board with a built-in low-pass filter is secondarily mounted on another board is reduced. Since the size of the base is not limited by the number of terminals, the size of the wiring board with a built-in low-pass filter can be easily reduced, and the distance between the terminals can be increased. Can also be improved. Further, since the terminal area per terminal can be increased, mounting reliability can be improved.
[0054]
In addition, by electrically connecting a low-pass filter having a higher cut-off frequency than the pass band of the surface acoustic wave filter element to the transmission input side of the surface acoustic wave filter element, the band can be broadened in a higher frequency band than the pass band of the surface acoustic wave filter element. It compensates for the problem of the conventional composite filter, which cannot take a sufficient amount of attenuation, and can obtain a sufficiently high amount of attenuation in a high frequency band. For example, harmonics twice or three times the pass band of a power amplifier are also effective. Can be attenuated. In addition, since the low-pass filter as described above is built in the base, the number of components can be reduced.
[0055]
Further, according to the wiring board with a built-in low-pass filter of the present invention, the low-pass filter has a strip line, a ground electrode and a ground capacitance electrode forming a ground capacitance, and the ground electrode and the ground capacitance electrode are formed on the bottom surface of the cavity. When the strip line is disposed on the lower surface side and the strip line is disposed at a portion other than the lower portion of the cavity, the distance between the ground electrode and the ground capacitance electrode and the strip line can be increased, and the strip line can be separated. Since the stray capacitance of the line can be reduced, and the interaction between the ground electrode and the ground capacitance electrode and the inductance of the strip line can be reduced, a low-loss low-pass filter can be configured. In addition, by arranging the ground capacitance, which requires a relatively large area in the low-pass filter, on the lower surface side from the bottom surface of the cavity, it is arranged in a portion where the area can be maximized inside the low-pass filter built-in wiring board. It is not necessary to newly increase the number of dielectric layers in order to form a large ground capacitance, or to extremely thin the dielectric layer between the ground electrode and the ground capacitance electrode.
[0056]
Further, according to the wiring board with a built-in low-pass filter of the present invention, when a strip line for phase adjustment electrically connected to a surface acoustic wave filter element is provided inside the base, the By electrically connecting the phase shifter S using the adjustment stripline to the transmission output side of the surface acoustic wave filter element, the phase on the output side of the surface acoustic wave filter element can be appropriately adjusted. In addition, when the phase adjustment strip line is disposed on the lower surface side of the base from the bottom surface of the cavity, a relatively long phase adjustment strip line can be incorporated without unnecessarily increasing the size of the base.
[0057]
According to the wiring board with a built-in low-pass filter of the present invention, when the strip line is arranged on the upper surface side of the base rather than the ground electrode and the ground capacitance electrode, it is possible to further reduce the stray capacitance of inductance due to the strip line. In addition, the distance between the strip line and the ground electrode and the ground capacitance electrode can be further increased, and the interaction between the ground electrode and the ground capacitance electrode and the inductance can be reduced, so that a low-loss low-pass filter can be configured. be able to.
[0058]
Further, according to the wiring board with a built-in low-pass filter of the present invention, when the strip line and the phase adjustment strip line are respectively disposed at opposing portions across the cavity of the base, the strip line and the phase adjustment strip Since the distance from the line is sufficiently large and the isolation between the low-pass filter and the phase shifter can be improved, a low-loss low-pass filter can be configured.
[0059]
As described above, according to the present invention, the number of connection terminals with the outside is reduced by forming the low-pass filter inside the base body made of the laminated body and connecting the low-pass filter to the transmission output side of the surface acoustic wave filter. In addition, the attenuation of the high frequency band can be made larger than the pass band of the surface acoustic wave filter by the low pass filter, so that the harmonics twice or three times the pass band generated by the power amplifier required on the transmission side of the wireless device can be obtained. Can be attenuated over a wide band, and a wiring board with a built-in low-pass filter that can realize a low-pass filter with small loss inside the base can be provided.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view showing an example of an embodiment of a wiring board with a built-in low-pass filter of the present invention.
FIG. 2 is an equivalent circuit diagram of an example of the wiring board with a built-in low-pass filter shown in FIG. 1;
FIG. 3 is a diagram showing frequency characteristics of a low-pass filter in the example of the wiring board with a built-in low-pass filter shown in FIG. 1;
FIG. 4 is an exploded perspective view showing another example of the embodiment of the wiring board with a built-in low-pass filter of the present invention.
5 is an equivalent circuit diagram of an example of the wiring board with a built-in low-pass filter shown in FIG. 4;
6 is a diagram illustrating frequency characteristics of a low-pass filter in the example of the wiring board with a built-in low-pass filter illustrated in FIG. 4;
FIG. 7 is an exploded perspective view showing still another example of the embodiment of the wiring board with a built-in low-pass filter of the present invention.
8 is an equivalent circuit diagram of the example of the wiring board with a built-in low-pass filter shown in FIG. 7;
9 is a diagram showing frequency characteristics of the low-pass filter in the example of the wiring board with a built-in low-pass filter shown in FIG. 7;
[Explanation of symbols]
1, 1a, 1b ... first dielectric layer
2, 2a, 1b... Second dielectric layer
3, 3a, 3b... Third dielectric layer
4, 4a, 4b... Fourth dielectric layer
5, 5a, 5b... Fifth dielectric layer
6, 6a, 6b ... cavity
7, 7a, 7b... First ground electrode
8, 8a, 8b... Second ground electrode
9, 9a, 9b ... Strip line for phase adjustment
10, 10a, 10b... First ground capacitance electrode
11, 11a, 11b... Second ground capacitance electrode
12, 12a, 12b ... first strip line
13, 13a, 13b ... second strip line
14, 14a, 14b ... first through conductor
15, 15a, 15b ... second through conductor
16, 16a, 16b ... third through conductor
17, 17a... Fourth through conductor
17b ······ Reception-side output terminal electrically connected to reception input side of surface acoustic wave filter element
18, 18a, 18b... Transmission-side output terminals electrically connected to the transmission input of the surface acoustic wave filter element
19, 19a, 19b... Transmission-side input terminals electrically connected to the surface-acoustic-wave filter element transmission output
20a, 20b... Capacitance electrode

Claims (5)

A substrate formed by laminating a plurality of dielectric layers; a cavity formed on the upper surface of the substrate for accommodating a surface acoustic wave filter element; and a transmission input of the surface acoustic wave filter element incorporated inside the substrate. And a low-pass filter electrically connected to the side of the wiring board. The low-pass filter has a strip line, a ground electrode and a ground capacitance electrode forming a ground capacitance, and the ground electrode and the ground capacitance electrode are arranged on the lower surface side from the bottom surface of the cavity, 2. The wiring board with a built-in low-pass filter according to claim 1, wherein the strip line is arranged at a portion other than a lower portion of the cavity. 3. The wiring board with a built-in low-pass filter according to claim 1, further comprising a strip line for phase adjustment, which is built in the base and electrically connected to the surface acoustic wave filter element. 4. The wiring board with a built-in low-pass filter according to claim 1, wherein the strip line is arranged on an upper surface side of the base with respect to the ground electrode and the ground capacitance electrode. 5. 5. The wiring board with a built-in low-pass filter according to claim 3, wherein the strip line and the strip line for phase adjustment are respectively arranged in portions of the base body facing each other with the cavity interposed therebetween. 6.

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