JP2011199809A - Acoustic wave demultiplexer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve an isolation characteristic in an acoustic wave demultiplexer having a transmitting side filter chip and a receiving side filter chip.SOLUTION: The acoustic wave demultiplexer 1 includes the transmitting side filter chip 30 and the receiving side filter chip 20. The receiving side filter chip 20 includes a receiving side piezoelectric substrate 21, and a receiving side acoustic wave filter 23 formed on the receiving side piezoelectric substrate 21. The transmitting side filter chip 30 includes a transmitting side piezoelectric substrate 31, and a transmitting side filter 33 formed on the transmitting side piezoelectric substrate 31. The thickness Tof the transmitting side piezoelectric substrate 31 is smaller than the thickness Tof the receiving side piezoelectric substrate 21.

Description

  The present invention relates to an elastic wave duplexer. In particular, the present invention relates to an acoustic wave duplexer having a transmission side filter chip and a reception side filter chip.

  In recent years, an elastic device using an elastic wave such as a surface acoustic wave or a boundary acoustic wave is used as a demultiplexer for separating a transmission signal and a reception signal between an antenna terminal and a transmission-side signal terminal and a reception-side signal terminal. Wave demultiplexers are becoming widely used.

  The elastic wave duplexer generally includes a transmission side filter chip and a reception side filter chip mounted on a mounting substrate. The transmission-side filter chip is provided with a transmission-side elastic wave filter portion connected between the antenna terminal and the transmission-side signal terminal. On the other hand, the reception-side filter chip is provided with a reception-side acoustic wave filter portion connected between the antenna terminal and the reception-side signal terminal.

  For example, from the viewpoint of downsizing the acoustic wave duplexer, it is preferable to integrally form the piezoelectric substrate of the transmission side acoustic wave filter unit and the piezoelectric substrate of the reception side acoustic wave filter unit. However, in this case, there is a problem that the isolation characteristic of the elastic wave duplexer tends to deteriorate.

  In view of such a problem, for example, in Patent Document 1 below, an acoustic wave duplexer in which a piezoelectric substrate of a transmission-side elastic wave filter unit and a piezoelectric substrate of a reception-side elastic wave filter unit are separately provided Is disclosed.

JP-A-2005-318128

  However, even when the piezoelectric substrate of the transmission-side elastic wave filter unit and the piezoelectric substrate of the reception-side elastic wave filter unit are provided separately, a sufficiently good isolation characteristic cannot be obtained.

  The present invention has been made in view of such a point, and an object thereof is to improve isolation characteristics in an acoustic wave duplexer having a transmission filter chip and a reception filter chip.

The elastic wave duplexer according to the present invention includes an antenna terminal, a transmission side signal terminal, a reception side signal terminal, a transmission side filter chip, and a reception side filter chip. The reception-side filter chip has a reception-side piezoelectric substrate and a reception-side elastic wave filter unit. The reception-side elastic wave filter unit is formed on the reception-side piezoelectric substrate. The reception side acoustic wave filter unit is connected between the antenna terminal and the reception side signal terminal. The transmission-side filter chip has a transmission-side piezoelectric substrate and a transmission-side elastic wave filter unit. The transmission-side elastic wave filter unit is formed on the transmission-side piezoelectric substrate. The transmission-side acoustic wave filter unit is connected between the antenna terminal and the transmission-side signal terminal. The thickness T _Tx of the transmission side piezoelectric substrate is smaller than the thickness T _Rx of the reception side piezoelectric substrate.

In a specific aspect of the acoustic wave duplexer according to the present invention, the thickness T _Tx of the transmission-side piezoelectric substrate is 0.2 mm or less. According to this configuration, the isolation characteristic between the transmission side signal terminal and the reception side signal terminal in the transmission side frequency band can be further improved.

In another specific aspect of the acoustic wave duplexer according to the present invention, the thickness T _Tx of the transmission-side piezoelectric substrate is 0.1 mm or more. According to this configuration, it is possible to increase the rigidity of the transmission-side filter chip without deteriorating the isolation characteristics between the transmission-side signal terminal and the reception-side signal terminal in the transmission-side frequency band.

In another specific aspect of the acoustic wave duplexer according to the present invention, the thickness T _Tx of the transmission-side piezoelectric substrate is 0.1 mm or less. According to this configuration, the isolation characteristic between the transmission side signal terminal and the reception side signal terminal in the reception side frequency band can be improved.

In still another specific aspect of the elastic wave duplexer according to the present invention, the thickness T _Tx of the transmission-side piezoelectric substrate is 0.05 mm or less. According to this configuration, the isolation characteristic between the transmission side signal terminal and the reception side signal terminal in the reception side frequency band can be further improved.

In yet another specific aspect of the acoustic wave duplexer according to the present invention, the thickness T _Rx of the receiving side piezoelectric substrate is 0.3mm or less. According to this configuration, the isolation characteristic between the transmission side signal terminal and the reception side signal terminal can be further improved.

  In another specific aspect of the elastic wave duplexer according to the present invention, one of the reception-side elastic wave filter and the transmission-side elastic wave filter is a balanced filter.

  In another specific aspect of the elastic wave duplexer according to the present invention, the reception-side elastic wave filter is a balanced filter.

  In still another specific aspect of the elastic wave duplexer according to the present invention, the reception-side piezoelectric substrate and the transmission-side piezoelectric substrate are made of different materials.

In still another specific aspect of the elastic wave duplexer according to the present invention, the reception-side piezoelectric substrate is made of a LiTaO ₃ substrate, and the transmission-side piezoelectric substrate is made of a LiNbO ₃ substrate.

In the present invention, the thickness T _Tx of the transmission side piezoelectric substrate is smaller than the thickness T _Rx of the reception side piezoelectric substrate. For this reason, the isolation characteristic between the transmission side signal terminal and the reception side signal terminal in the transmission side frequency band can be improved.

1 is a schematic diagram of an acoustic wave duplexer according to an embodiment of the present invention. 1 is an equivalent circuit diagram of an elastic wave duplexer according to an embodiment of the present invention. It is a typical sectional view of the receiving side filter chip in one embodiment of the present invention. It is typical sectional drawing of the transmission side filter chip | tip in one Embodiment of this invention. It is a graph showing the isolation characteristic between the transmission side signal terminal and the 1st reception side signal terminal in each of Examples 1-3 and a comparative example. It is a graph showing the isolation characteristic between the transmission side signal terminal in each of Example 1 and Example 4, and the 1st reception side signal terminal. It is an equivalent circuit diagram for demonstrating a direct wave. It is an equivalent circuit diagram for demonstrating a direct wave. It is an equivalent circuit diagram for demonstrating a direct wave.

  Hereinafter, a preferred embodiment in which the present invention is implemented will be described taking the surface acoustic wave duplexer 1 shown in FIGS. 1 and 2 as an example. However, the surface acoustic wave duplexer 1 is merely an example. The elastic wave duplexer according to the present invention is not limited to the surface acoustic wave duplexer 1. The elastic wave duplexer according to the present invention may be, for example, a boundary acoustic wave duplexer using boundary acoustic waves.

  The surface acoustic wave duplexer 1 of the present embodiment has a transmission frequency band (Tx band) of 1850 MHz to 1910 MHz and a reception frequency band (Rx band) of 1930 MHz to 1990 MHz.

  FIG. 1 is a schematic diagram of an acoustic wave duplexer according to the present embodiment. FIG. 2 is an equivalent circuit diagram of the acoustic wave duplexer according to the present embodiment. FIG. 3 is a schematic cross-sectional view of the reception-side filter chip. FIG. 4 is a schematic cross-sectional view of the transmission-side filter chip.

  As shown in FIG. 1, the surface acoustic wave duplexer 1 includes a wiring board 10, a reception-side filter chip 20, and a transmission-side filter chip 30. The reception-side filter chip 20 and the transmission-side filter chip 30 are flip-chip mounted on the wiring board 10. A resin layer 11 is formed on the wiring substrate 10. The resin layer 11 seals the reception side filter chip 20 and the transmission side filter chip 30.

As shown in FIG. 3, the reception-side filter chip 20 includes a reception-side piezoelectric substrate 21. The receiving side piezoelectric substrate 21 is not particularly limited as long as it is a substrate having piezoelectricity. The reception-side piezoelectric substrate 21 can be constituted by, for example, a LiNbO ₃ substrate, a LiTaO ₃ substrate, a crystal substrate, a ZnO substrate, or the like.

  An electrode 22 including an IDT electrode for exciting a surface acoustic wave is formed on the reception-side piezoelectric substrate 21. The electrode 22 constitutes a reception-side surface acoustic wave filter unit 23. The electrode 22 can be formed of, for example, a metal such as Al, Pt, Au, Ag, Cu, Ti, Ni, Cr, Pd, Ni, and W, or an alloy containing one or more of these metals. For example, the electrode 22 may be composed of a laminate of a plurality of metal films or alloy films.

As shown in FIG. 4, the transmission-side filter chip 30 includes a transmission-side piezoelectric substrate 31. The transmission side piezoelectric substrate 31 is not particularly limited as long as it is a substrate having piezoelectricity. The transmission-side piezoelectric substrate 31 can be composed of, for example, a LiNbO ₃ substrate, a LiTaO ₃ substrate, a crystal substrate, a ZnO substrate, or the like. The transmission-side piezoelectric substrate 31 may be configured by the same type of piezoelectric substrate as the reception-side piezoelectric substrate 21 or may be configured by a different type of piezoelectric substrate.

  An electrode 32 including an IDT electrode for exciting a surface acoustic wave is formed on the transmission side piezoelectric substrate 31. The electrode 32 constitutes a transmission-side surface acoustic wave filter unit 33. The electrode 32 can be formed of, for example, a metal such as Al, Pt, Au, Ag, Cu, Ti, Ni, Cr, Pd, Ni, and W, or an alloy containing one or more of these metals. For example, the electrode 32 may be formed of a laminate of a plurality of metal films or alloy films.

  As shown in FIG. 2, the surface acoustic wave duplexer 1 includes an antenna terminal 12, a transmission-side signal terminal 13, and first and second reception-side signal terminals 14a and 14b.

  The transmission-side surface acoustic wave filter unit 33 is connected between the antenna terminal 12 and the transmission-side signal terminal 13. In the present embodiment, the transmission-side surface acoustic wave filter unit 33 is configured by a ladder-type surface acoustic wave filter unit that does not have a balanced-unbalanced conversion function, and one transmission-side signal terminal 13 is provided.

  The reception-side surface acoustic wave filter unit 23 is connected between the antenna terminal 12 and the first and second reception-side signal terminals 14a and 14b. In the present embodiment, the reception-side surface acoustic wave filter unit 23 includes a so-called balanced longitudinally coupled resonator type acoustic wave filter unit having a balanced-unbalanced conversion function.

  Note that the transmission-side surface acoustic wave filter unit and the reception-side surface acoustic wave filter unit are not limited to this combination. In this embodiment, the transmission-side surface acoustic wave filter unit is a ladder-type filter unit, and the reception-side surface acoustic wave filter is a longitudinally coupled resonator-type filter unit. However, the same effect as this embodiment can be obtained even if the configuration is changed. It is done.

In the present embodiment, the thickness T _Tx of the transmission side piezoelectric substrate 31 is smaller than the thickness T _Rx of the reception side piezoelectric substrate 21. Therefore, as is also supported in the embodiment, the isolation characteristic between the transmission side signal terminal 13 and the first reception side signal terminal 14a in the transmission side frequency band can be improved.

Since the isolation characteristics of the thickness T _Tx is thinner is better transmission side piezoelectric substrate 31 is obtained, the thickness T _Tx transmission side piezoelectric substrate 31 is preferably 0.2mm or less. However, when the thickness T _Tx of the transmission-side piezoelectric substrate 31 is 0.1 mm or less, the surface acoustic wave duplexer 1 is isolated in the transmission frequency band even if the thickness T _Tx of the transmission-side piezoelectric substrate 31 is reduced. Characteristics will not change significantly. For this reason, from the viewpoint of improving the isolation characteristics of the surface acoustic wave duplexer 1 in the transmission frequency band, the thickness T _Tx of the transmission-side piezoelectric substrate 31 does not need to be less than 0.1 mm. If the thickness T _Tx transmission side piezoelectric substrate 31 is too thin, the mechanical strength of the transmission side piezoelectric substrate 31 tends to decrease. For this reason, it is preferable that the thickness T _Tx of the transmission-side piezoelectric substrate 31 is 0.1 mm or more.

However, the isolation characteristic of the surface acoustic wave duplexer 1 in the reception-side frequency band is improved by setting the thickness T _Tx of the transmission-side piezoelectric substrate 31 to 0.1 mm or less. Specifically, by setting the thickness T _Tx transmission side piezoelectric substrate 31 with 0.1mm or less, it is possible to increase the maximum value of the isolation characteristic in the reception-side frequency band. For this reason, the thickness T _Tx of the transmission-side piezoelectric substrate 31 is preferably 0.1 mm or less, and more preferably 0.05 mm or less.

From the viewpoint of obtaining better isolation characteristics, it is preferable that the receiving side piezoelectric substrate 21 has a smaller thickness _TRx . Therefore, the thickness _{T Rx} of the receiving side piezoelectric substrate 21 is preferably 0.3mm or less, more preferably 0.25mm or less.

In addition, by making the thickness T _Tx of the transmission-side piezoelectric substrate 31 smaller than the thickness T _Rx of the reception-side piezoelectric substrate 21, the space between the transmission-side signal terminal 13 and the first reception-side signal terminal 14a in the transmission-side frequency band. The reason why the isolation characteristics can be improved is considered to be as follows. When an electrical signal is applied to the surface acoustic wave duplexer, electromagnetic field leakage occurs. As a result, electrical coupling of inductance and capacitance occurs between the transmission-side piezoelectric substrate 31, the reception-side piezoelectric substrate 21, the antenna terminal 12, the transmission-side signal terminal 13, and the reception-side signal terminals 14a and 14b and the ground. . As a result, a part of the signal may reach directly through the generated inductance or capacitance without going through the IDT electrode formed on the piezoelectric substrate. Hereinafter, a phenomenon in which a part of the signal reaches directly will be described.

  The surface acoustic wave filter chip for transmission and the surface acoustic wave filter chip for reception are flip-chip mounted on a substrate and sealed with a sealing resin. That is, in the surface acoustic wave filter chip, one main surface on which the IDT electrode is formed is opposed to the substrate, and a sealing portion made of a polymer material (resin) is provided on the other main surface on the opposite side. Existing. Due to the sealing portion and the piezoelectric substrate portion, a direct wave due to the capacitance existing on the other main surface of the surface acoustic wave filter chip is generated.

  For example, as shown in the circuit diagram of FIG. 7, a two-terminal-pair surface acoustic wave filter 60 having input terminals 61 and 62 and output terminals 63 and 64 is considered. At this time, as indicated by arrows 70 and 72 in the circuit diagram of FIG. 8, there are signals transmitted directly from the input terminals 61 and 62 to the output terminals 63 and 64 without passing through the surface acoustic wave filter 60. This signal is called a direct wave.

  As shown in the equivalent circuit diagram of FIG. 9, the direct wave is generated by a component 74 due to mutual inductance between the input terminals 61 and 62 and the output terminals 63 and 64, and between the input terminals 61 and 62 and the output terminals 63 and 64. A component 76 due to capacitive coupling between the two and a component 78 due to floating of the ground are included.

This direct wave may deteriorate the isolation characteristics between the transmission terminal and the reception terminal in the elastic wave duplexer. Here, the size of the capacitance generated between the transmission side piezoelectric substrate, the reception side piezoelectric substrate, the antenna terminal, the transmission side signal terminal and the reception side signal terminal, and the ground depends on the thickness of the piezoelectric substrate. Specifically, the smaller the thickness of the piezoelectric substrate, the smaller the capacitance generated between the piezoelectric substrate and each terminal. For this reason, as the thickness of the piezoelectric substrate decreases, the direct achievement of the signal through the generated capacitance decreases. In the present embodiment, since the transmission side piezoelectric substrate 31 has a small thickness T _Tx , direct transmission of signals in the transmission side surface acoustic wave filter unit 33 can be suppressed. As a result, it is considered that deterioration of isolation characteristics can be suppressed.

Hereinafter, by making the thickness T _Tx of the transmission-side piezoelectric substrate 31 smaller than the thickness T _Rx of the reception-side piezoelectric substrate 21, between the transmission-side signal terminal 13 and the first reception-side signal terminal 14a in the transmission-side frequency band. The fact that the isolation characteristics can be improved will be described in more detail based on examples.

5 and 6 show the isolation characteristics of the surface acoustic wave duplexers according to Examples 1 to 4 having substantially the same configuration as that of the surface acoustic wave duplexer 1 according to the embodiment, and the comparative example. The isolation characteristics of a surface acoustic wave duplexer are shown. Incidentally, surface acoustic wave duplexer according to the comparative example, the the thickness T _Rx of the receiving side piezoelectric substrate 21 and the thickness T _Tx transmission side piezoelectric substrate 31 together, except for a 0.25 mm, the above-described embodiment The surface acoustic wave duplexer 1 has the same configuration.

5 and 6, the graphs indicated by the solid lines indicate the elasticity according to Example 1 in which the thickness T _Rx of the reception-side piezoelectric substrate 21 is 0.25 mm and the thickness T _Tx of the transmission-side piezoelectric substrate 31 is 0.1 mm. 4 is a graph showing the isolation characteristics of the surface wave duplexer 1.

In FIG. 5, a graph indicated by a one-dot broken line shows an elastic surface according to Example 2 in which the thickness T _Rx of the reception-side piezoelectric substrate 21 is 0.25 mm and the thickness T _Tx of the transmission-side piezoelectric substrate 31 is 0.15 mm. 4 is a graph showing the isolation characteristics of the wave splitter 1.

In FIG. 5, the graph indicated by a two-dot broken line indicates the elasticity according to the third embodiment, in which the thickness T _Rx of the reception-side piezoelectric substrate 21 is 0.25 mm and the thickness T _Tx of the transmission-side piezoelectric substrate 31 is 0.2 mm. 4 is a graph showing the isolation characteristics of the surface wave duplexer 1.

5, the graph shown by a dotted line, and the thickness T _Rx of the receiving side piezoelectric substrate 21 and the thickness T _Tx transmission side piezoelectric substrate 31 are equal, the graph showing the isolation characteristics of the surface acoustic wave duplexer according to the comparative example It is.

In FIG. 6, a graph indicated by a one-dot broken line shows an elastic surface according to Example 4 in which the thickness T _Rx of the reception-side piezoelectric substrate 21 is 0.25 mm and the thickness T _Tx of the transmission-side piezoelectric substrate 31 is 0.05 mm. 4 is a graph showing the isolation characteristics of the wave splitter 1.

As shown in FIG. 5, as compared to the thickness T _Rx of the receiving side piezoelectric substrate 21 and the thickness T _Tx transmission side piezoelectric substrate 31 is equal to Comparative Example, the thickness T _Tx transmission side piezoelectric substrate 31, the receiving side piezoelectric substrate In Examples 1 to 4 smaller than the thickness _{TRx of} 21, it can be seen that the isolation characteristic between the transmission side signal terminal 13 and the first reception side signal terminal 14a in the transmission side frequency band is good. Further, it can be seen that the thinner the thickness T _Tx of the transmission side piezoelectric substrate 31 is, the better the isolation characteristic between the transmission side signal terminal 13 and the first reception side signal terminal 14a in the transmission side frequency band is. . However, as shown in FIG. 6, in the case where the thickness T _Tx of the transmission side piezoelectric substrate 31 is 0.1 mm and the case where the thickness T _Rx of the reception side piezoelectric substrate 21 is 0.05 mm, the transmission side frequency band The isolation characteristics of the surface acoustic wave branching filter at are the same.

However, with respect to the reception side frequency band, the case where the thickness T _Tx of the transmission side piezoelectric substrate 31 is 0.1 mm or less is less than the case where the thickness T _Tx of the transmission side piezoelectric substrate 31 is 0.25 mm. The maximum value of the oscillation characteristics was large.

From the above results, it can be seen that the thickness T _Tx of the transmission-side piezoelectric substrate 31 is preferably 0.2 mm or less, and more preferably 0.15 mm or less. Further, from the viewpoint of improving the durability of the acoustic wave duplexer while maintaining good isolation characteristics in the transmission side frequency band, the thickness T _Tx of the transmission side piezoelectric substrate 31 is preferably 0.1 mm or more. I understand that. On the other hand, in order to improve the isolation characteristics in both the transmission-side frequency band and the reception-side frequency band, the thickness T _Tx of the transmission-side piezoelectric substrate 31 is preferably 0.1 mm or less. It can be seen that the thickness T _Tx is more preferably 0.05 mm or less.

DESCRIPTION OF SYMBOLS 1 ... Surface acoustic wave duplexer 10 ... Wiring board 11 ... Resin layer 12 ... Antenna terminal 13 ... Transmission side signal terminal 14a ... 1st reception side signal terminal 14b ... 2nd reception side signal terminal 20 ... Reception side filter chip DESCRIPTION OF SYMBOLS 21 ... Reception side piezoelectric substrate 22 ... Electrode 23 ... Reception side surface acoustic wave filter part 30 ... Transmission side filter chip 31 ... Transmission side piezoelectric substrate 32 ... Electrode 33 ... Transmission side surface acoustic wave filter part

Claims (10)

An antenna terminal;
A transmitter signal terminal;
A receiving signal terminal;
An elastic wave demultiplexer comprising a transmission side filter chip and a reception side filter chip,
The reception-side filter chip includes a reception-side piezoelectric substrate and a reception-side acoustic wave filter portion formed on the reception-side piezoelectric substrate and connected between the antenna terminal and the reception-side signal terminal. Have
The transmission-side filter chip includes a transmission-side piezoelectric substrate and a transmission-side acoustic wave filter portion formed on the transmission-side piezoelectric substrate and connected between the antenna terminal and the transmission-side signal terminal. Have
The elastic wave duplexer, wherein a thickness T _Tx of the transmission side piezoelectric substrate is smaller than a thickness T _Rx of the reception side piezoelectric substrate. The elastic wave duplexer according to claim 1, wherein a thickness T _Tx of the transmission-side piezoelectric substrate is 0.2 mm or less. The elastic wave duplexer according to claim 2, wherein a thickness T _Tx of the transmission-side piezoelectric substrate is 0.1 mm or more. The elastic wave duplexer according to claim 2, wherein a thickness T _Tx of the transmission-side piezoelectric substrate is 0.1 mm or less. The elastic wave duplexer according to claim 4, wherein a thickness T _Tx of the transmission-side piezoelectric substrate is 0.05 mm or less. The thickness T _Rx of the receiving side piezoelectric substrate is 0.3mm or less, the acoustic wave duplexer according to any one of claims 1-5.   The elastic wave duplexer according to any one of claims 1 to 6, wherein any one of the reception-side elastic wave filter and the transmission-side elastic wave filter is a balanced filter.   The elastic wave duplexer according to claim 7, wherein the reception-side elastic wave filter is a balanced filter.   The elastic wave duplexer according to claim 1, wherein the reception-side piezoelectric substrate and the transmission-side piezoelectric substrate are made of different materials. The elastic wave duplexer according to any one of claims 1 to 9, wherein the reception-side piezoelectric substrate is made of a LiTaO ₃ substrate, and the transmission-side piezoelectric substrate is made of a LiNbO ₃ substrate.

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