JP2011199810A - 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 has 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 has a transmitting side piezoelectric substrate 31, and a transmitting side acoustic wave filter 33 formed on the transmitting side piezoelectric substrate 31. The thickness Tof the receiving side piezoelectric substrate 21 is smaller than the thickness Tof the transmitting side piezoelectric substrate 31.

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 _Rx of the reception side piezoelectric substrate is smaller than the thickness T _Tx of the transmission side piezoelectric substrate.

In a specific aspect of the acoustic wave duplexer according to the present invention, the thickness T _Rx of the receiving side piezoelectric substrate is 0.2mm 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 _Rx of the receiving side piezoelectric substrate is 0.1mm or more. According to this configuration, it is possible to increase the rigidity of the reception-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 0.3 mm 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 still 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 still another specific aspect of the acoustic wave duplexer according to the present invention, the reception-side acoustic wave filter is a balanced filter.

  In 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 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 this configuration, since the relatively thin receiving-side piezoelectric substrate is made of the LiTaO ₃ substrate having relatively high rigidity, it is possible to improve the isolation characteristics while suppressing deterioration in durability of the acoustic wave duplexer.

In the present invention, the thickness T _Rx of the reception side piezoelectric substrate is smaller than the thickness T _Tx of the transmission 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. In addition, the reception-side piezoelectric substrate of the reception-side filter chip with low required power resistance can be made smaller than the transmission-side piezoelectric substrate of the transmission-side filter chip with high required power resistance, and thus is not easily damaged. Therefore, even if less than the thickness T _Tx transmission side piezoelectric substrate thickness T _Rx of the receiving side piezoelectric substrate, is not significantly deteriorated durability. Therefore, according to the present invention, an elastic wave duplexer having excellent isolation characteristics and high durability can be provided.

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. Among them, the receiving side piezoelectric substrate 21 is preferably made of a LiTaO ₃ substrate. When the receiving side piezoelectric substrate 21 is composed of a LiTaO ₃ substrate, transverse mode ripple can be suppressed, and a filter having excellent temperature characteristics can be obtained.

  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. Among them, the transmission side piezoelectric substrate 31 is preferably formed of a LiNbO ₃ substrate. When the transmission-side piezoelectric substrate is composed of a LiNbO ₃ substrate, it is possible to obtain a filter having a broadband pass characteristic with reduced insertion loss. However, the transmission-side piezoelectric substrate 31 may be formed of the same type of piezoelectric substrate as the reception-side piezoelectric substrate 21.

  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.

  The transmission-side surface acoustic wave filter unit and the reception-side surface acoustic wave filter unit are not limited to the above combinations. 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 unit is a longitudinally coupled resonator-type filter unit. However, the same effect as this embodiment can be obtained even if the configuration is changed. can get.

In the present embodiment, the thickness T _Rx of the reception side piezoelectric substrate 21 is smaller than the thickness T _Tx of the transmission side piezoelectric substrate 31. 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.

In addition, the receiving-side filter chip 20 having lower power durability than the transmitting-side filter chip 30 can make the piezoelectric substrate smaller. For this reason, the receiving side piezoelectric substrate 21 is smaller than the transmitting side piezoelectric substrate 31 and is not easily damaged. Therefore, even if less than the thickness T _Tx transmission side piezoelectric substrate 31 and the thickness T _Rx of the receiving side piezoelectric substrate 21, is not significantly reduced durability of the surface acoustic wave duplexer 1. Therefore, the surface acoustic wave duplexer 1 according to this embodiment has excellent isolation characteristics and high mechanical durability.

In the present embodiment, the thin receiving-side piezoelectric substrate 21 is composed of a highly rigid LiTaO ₃ substrate. For this reason, higher durability can be realized.

Since the isolation characteristics of better thickness T _Rx of the receiving side piezoelectric substrate 21 is thin is better is obtained, the thickness T _Rx of the receiving side piezoelectric substrate 21 is preferably 0.2mm or less. However, when the thickness T _Rx of the receiving side piezoelectric substrate 21 is 0.1mm or less, even thinner thickness T _Rx of the receiving side piezoelectric substrate 21, isolation characteristics of the surface acoustic wave duplexer 1 is greatly changed No longer. Therefore, from the viewpoint of improving the isolation characteristic it is not required to be less than 0.1mm thickness T _Rx of the receiving side piezoelectric substrate 21. If the thickness T _Rx of the receiving side piezoelectric substrate 21 is too thin, the mechanical strength of the received side piezoelectric substrate 21 tends to decrease. Therefore, the thickness _{T Rx} of the receiving side piezoelectric substrate 21 is preferably 0.1mm or more.

From the viewpoint of obtaining better isolation characteristics, it is preferable that the thickness T _Tx of the transmission-side piezoelectric substrate 31 is also thin. For this reason, the thickness T _Tx of the transmission-side piezoelectric substrate 31 is preferably 0.3 mm or less, and more preferably 0.25 mm or less.

Incidentally, to be smaller than the thickness T _Tx transmission side piezoelectric substrate 31 and the thickness T _Rx of the receiving side piezoelectric substrate 21, between the transmission-side signal terminal 13 at the transmitting side frequency band and the first reception-side signal terminal 14a 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 thickness of the reception-side piezoelectric substrate 21 is reduced, it is possible to suppress direct signal arrival at the reception-side surface acoustic wave filter unit 23. As a result, it is considered that deterioration of isolation characteristics can be suppressed.

Hereinafter, to be smaller than the thickness T _Tx transmission side piezoelectric substrate 31 and the thickness T _Rx of the receiving side piezoelectric substrate 21, between the transmission-side signal terminal 13 at the transmitting side frequency band and the first reception-side signal terminal 14a 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 the first embodiment, in which the thickness T _Tx of the transmission-side piezoelectric substrate 31 is 0.25 mm and the thickness T _Rx of the reception-side piezoelectric substrate 21 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 indicates an elastic surface according to the second embodiment in which the thickness T _Tx of the transmission-side piezoelectric substrate 31 is 0.25 mm and the thickness T _Rx of the reception-side piezoelectric substrate 21 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 Example 3 in which the thickness T _Tx of the transmission-side piezoelectric substrate 31 is 0.25 mm and the thickness T _Rx of the reception-side piezoelectric substrate 21 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 the fourth embodiment in which the thickness T _Tx of the transmission-side piezoelectric substrate 31 is 0.25 mm and the thickness T _Rx of the reception-side piezoelectric substrate 21 is 0.05 mm. 4 is a graph showing the isolation characteristics of the wave splitter 1.

As shown in FIG. 5, the thickness T _Rx of the reception-side piezoelectric substrate 21 is smaller than that of the comparative example in which the thickness T _Rx of the reception-side piezoelectric substrate 21 is equal to the thickness T _Tx of the transmission-side piezoelectric substrate 31. In Examples 1 to 4 smaller than the thickness T _{Tx of} 31, 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 the thickness T _Rx of the receiving side piezoelectric substrate 21 is thin, it can be seen isolation characteristic is more favorable between the transmission-side signal terminal 13 at the transmitting side frequency band and the first reception-side signal terminal 14a . However, as shown in FIG. 6, and when the thickness _{T Rx} of the receiving side piezoelectric substrate 21 is 0.1 mm, in the case the thickness _{T Rx} of the receiving side piezoelectric substrate 21 is 0.05 mm, the surface acoustic wave component The isolation characteristics of the waver were similar. From the above results, the thickness _{T Rx} of the receiving side piezoelectric substrate 21 is preferably, it can be seen more preferably 0.15mm or less 0.2mm or less. The thickness _{T Rx} of the receiving side piezoelectric substrate 21, it is understood that it is preferable that the 0.1mm or more.

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 (8)

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
An elastic wave _{duplexer in} which a thickness T _Rx of the reception-side piezoelectric substrate is smaller than a thickness T _Tx of the transmission-side piezoelectric substrate. The thickness _{T Rx} of the receiving side piezoelectric substrate is 0.2mm or less, the acoustic wave duplexer according to claim 1. The thickness _{T Rx} of the receiving side piezoelectric substrate is 0.1mm or more, the acoustic wave duplexer according to claim 2. The thickness T _Tx transmission side piezoelectric substrate is 0.3mm or less, the acoustic wave duplexer according to any one of claims 1-3.   The elastic wave duplexer according to any one of claims 1 to 4, wherein 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 5, 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 acoustic wave duplexer according to claim 1, 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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