JP2013168692A - Acoustic wave demultiplexer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an acoustic wave demultiplexer which can prevent generation of ripple in the passband of a transmission filter while enhancing steepness of filter characteristics.SOLUTION: The acoustic wave demultiplexer includes: a reception filter 10 connected between an antenna terminal 2 and first and second reception terminals 3, 4 and consisting of a longitudinal coupling resonator type acoustic wave filter; and a transmission filter 20 connected between the antenna terminal 2 and a transmission terminal 5. The reception filter 10 has first and second longitudinal coupling resonator type surface acoustic wave filters 101, 102. In the first and second longitudinal coupling resonator type surface acoustic wave filters 101, 102, a relation of λ1<λ2 is satisfied, where λ1 is the wavelength of an acoustic wave which is determined by the period of electrode fingers of second IDTs 112, 122 that are the IDTs connected with the antenna terminal 2, and λ2 is the wavelength of an acoustic wave which is determined by the period of electrode fingers of first and third IDTs 111, 113, 121, 123 that are the IDTs not connected with the antenna terminal 2.

Description

  The present invention relates to an elastic wave demultiplexer using an elastic wave such as a surface acoustic wave, and more particularly to an elastic wave demultiplexer in which a reception filter is a longitudinally coupled resonator type elastic wave filter.

  For example, in a cellular phone that supports a CDMA (Code Division Multiple Access) system such as UMTS (Universal Mobile Telecommunications System), an RF (Radio Frequency) circuit is equipped with a duplex in order to simultaneously transmit and receive signals. Yes. The duplexer is a duplexer including a transmission filter, a reception filter, and a matching circuit. As the transmission filter and the reception filter, surface acoustic wave filters are widely used.

  Patent Document 1 below discloses an example of such a duplexer.

  FIG. 13 is a schematic configuration diagram for explaining the duplexer described in Patent Document 1. In FIG.

  The duplexer 1001 has an antenna terminal 1003 connected to the antenna 1002. A transmission filter 1005 is connected between the antenna terminal 1003 and the transmission terminal 1004. A reception filter 1008 is connected between the antenna terminal 1003 and the first and second reception terminals 1006 and 1007. Further, a matching circuit 1009 is connected between the antenna terminal 1003 and the reception filter 1008.

  The transmission filter 1005 and the reception filter 1008 are surface acoustic wave filters. In order to reduce the size, the reception filter 1008 has a balanced-unbalanced conversion function. That is, in the reception filter 1008, an unbalanced signal is input from the input terminal 1010, and a balanced signal is output from the first and second reception terminals 1006 and 1007. In Patent Document 1, a balanced longitudinally coupled resonator type surface acoustic wave filter having a balanced-unbalanced conversion function is used as the receiving filter 1008. Thereby, it is possible to omit baluns and interstage filters in the RF circuit of the mobile phone.

JP 2003-347964 A

  However, it has been found that in the duplexer 1001 using the longitudinally coupled resonator type surface acoustic wave filter as the reception filter 1008, a ripple may occur in the pass band of the transmission filter 1005. It is considered that this ripple appears due to the influence of the longitudinally coupled resonator type surface acoustic wave filter which is the reception filter 1008. In a duplexer used in a communication system in which the frequency interval between the pass band of the transmission filter and the pass band of the reception filter, such as UMTS-BAND 2, 3, and 8, is used, there is a problem that the ripple is particularly likely to appear.

  An object of the present invention is to provide an elastic wave demultiplexer that eliminates the above-mentioned drawbacks of the prior art and is unlikely to cause ripples in the passband of a transmission filter.

  An acoustic wave duplexer according to the present invention is an acoustic wave duplexer including an antenna terminal, a reception terminal, and a transmission terminal, and is connected between the antenna terminal and the reception terminal, and is longitudinally coupled resonance A reception filter including a child-type elastic wave filter; and a transmission filter connected between the antenna terminal and the transmission terminal. In the present invention, the longitudinally coupled resonator type elastic wave filter has at least three IDTs arranged along the elastic wave propagation direction, and at least one IDT is connected to the antenna terminal among the at least three IDTs. The remaining IDTs are not connected to the antenna terminals. When the wavelength of the elastic wave in the IDT connected to the antenna terminal is λ1, and the wavelength of the elastic wave in the IDT not connected to the antenna terminal is λ2, λ1 <λ2.

  In the elastic wave demultiplexer according to the present invention, the ratio λ1 / λ2 of λ1 and λ2 is preferably 0.998 or less. In that case, ripples are less likely to occur in the pass band of the transmission filter.

  In another specific aspect of the acoustic wave duplexer according to the present invention, the reception terminal has first and second reception terminals, and the longitudinally coupled resonator type acoustic wave filter is connected in parallel to the antenna terminal. The first and second 3IDT type longitudinally coupled resonator type acoustic wave filter units and the third and fourth 3IDTs cascaded to the first and second 3IDT type longitudinally coupled resonator type acoustic wave filter units, respectively. And a longitudinally coupled resonator type acoustic wave filter section. Third and fourth 3IDT type longitudinally coupled resonator type acoustic wave filter sections are connected to the first and second receiving terminals, respectively. Then, when the three IDTs of the first and second 3IDT type longitudinally coupled resonator type elastic wave filter units are respectively set to the first to third IDTs along the elastic wave propagation direction, the first and second IDTs are used. Each of the second IDTs of the 3IDT type longitudinally coupled resonator type acoustic wave filter section is connected to the antenna terminal, and each of the first and third IDTs is not connected to the antenna terminal.

  In still another specific aspect of the acoustic wave duplexer according to the present invention, the reception terminal has first and second reception terminals, and the longitudinally coupled resonator type acoustic wave filter is connected in parallel to the antenna terminal. The first and second 3IDT type longitudinally coupled resonator type acoustic wave filter sections are provided. First and second 3IDT type longitudinally coupled resonator type acoustic wave filter sections are connected to the first and second receiving terminals, respectively. When the three IDTs of the first and second 3IDT type longitudinally coupled resonator type elastic wave filter units are first to third IDTs along the elastic wave propagation direction, the first and second 3IDT types The first and third IDTs of the longitudinally coupled resonator type acoustic wave filter section are connected to the antenna terminals, and the second IDTs are not connected to the antenna terminals. Is connected to the receiving terminal.

  In still another specific aspect of the elastic wave duplexer according to the present invention, the reception terminal has first and second reception terminals, and the longitudinally coupled resonator type elastic wave filter is along the elastic wave propagation direction. 5 IDT type longitudinally coupled resonator type elastic wave filter in which five IDTs are arranged.

  In still another specific aspect of the elastic wave duplexer according to the present invention, when five IDTs in the 5IDT type longitudinally coupled resonator type elastic wave filter are first to fifth IDTs along the elastic wave propagation direction. In addition, the first, third and fifth IDTs are connected to the antenna terminal, the second and fourth IDTs are not connected to the antenna terminal, and the second IDT is connected to the first receiving terminal. The fourth IDT is connected to the second receiving terminal.

  The elastic wave duplexer according to the present invention is used in various frequency bands, and is particularly preferably used in the frequency band of the UMTS-BAND2, 3 or 8 standard. In the frequency band of the UMTS-BAND2, 3 or 8 standard, the transmission-side passband and the reception-side passband are close to each other. In such a case, the present invention is particularly effective.

  In the present invention, the longitudinally coupled resonator type surface acoustic wave filter may be a longitudinally coupled resonator type surface acoustic wave filter using surface acoustic waves, or a longitudinally coupled resonator type elastic boundary using acoustic boundary waves. A wave filter may be used.

  In the acoustic wave duplexer according to the present invention, in the longitudinally coupled resonator type acoustic wave filter which is a reception filter, the wavelength of the elastic wave in the IDT connected to the antenna terminal is λ1, and the IDT not connected to the antenna terminal When the wavelength of the elastic wave is λ2, since λ1 <λ2, it is difficult for ripples to occur in the pass band of the transmission filter. Therefore, it is possible to improve the pass characteristic of the transmission filter.

1 is a schematic circuit diagram of a duplexer which is an elastic wave duplexer according to a first embodiment of the present invention. It is a figure which shows the filter characteristic of the transmission filter in the duplexer of the 1st Embodiment of this invention, and the filter characteristic of the transmission filter in the duplexer of a 1st comparative example. It is a figure which shows the filter characteristic of the transmission filter in the duplexer of the 1st Embodiment of this invention, and the filter characteristic of the transmission filter in the duplexer of the 2nd comparative example. It is a figure which expands and shows the principal part of the filter characteristic of FIG. It is a figure which shows the filter characteristic of the transmission filter in the duplexer of the 1st Embodiment of this invention, and the filter characteristic of the transmission filter in the duplexer of a 1st modification. It is a figure which shows the filter characteristic of the transmission filter in the duplexer of the 1st Embodiment of this invention, and the filter characteristic of the transmission filter in the duplexer of a 2nd modification. It is a figure which shows the filter characteristic of the transmission filter in the duplexer of the 1st Embodiment of this invention, and the filter characteristic of the transmission filter in the duplexer of a 3rd modification. FIG. 5 is a diagram illustrating a relationship between λ1 / λ2 and steepness in filter characteristics of a transmission filter in the duplexer reception filter according to the first exemplary embodiment of the present invention. It is a schematic circuit diagram of a duplexer which is an elastic wave duplexer according to a second embodiment of the present invention. It is a schematic circuit diagram of a duplexer which is an elastic wave duplexer according to a third embodiment of the present invention. It is a schematic circuit diagram of a duplexer which is an elastic wave duplexer according to a fourth embodiment of the present invention. It is a schematic circuit diagram of a duplexer which is an elastic wave duplexer according to a fifth embodiment of the present invention. It is a schematic block diagram for demonstrating the conventional duplexer.

  Hereinafter, the present invention will be clarified by describing specific embodiments of the present invention with reference to the drawings.

  FIG. 1 is a schematic circuit diagram of a duplexer 1 which is an elastic wave duplexer according to a first embodiment of the present invention. The duplexer 1 corresponds to UMTS-BAND2. In UMTS-BAND2, the transmission-side passband is 1850 to 1910 MHz, and the reception-side passband is 1930 to 1990 MHz.

  The duplexer 1 includes an antenna terminal 2, first and second reception terminals 3 and 4, and a transmission terminal 5.

  A matching circuit including an inductor 6 is connected to the antenna terminal 2. One end of the inductor 6 is connected to the antenna terminal 2 and the other end is connected to the ground potential.

  A transmission filter 20 is connected between the antenna terminal 2 and the transmission terminal 5. The transmission filter 20 is a surface acoustic wave filter having a ladder circuit configuration. That is, the transmission filter 20 includes the first, second, and third series arm resonators 201, 202, and 203 disposed on the series arm 211 that connects the antenna terminal 2 and the transmission terminal 5, the series arm 211, and the ground. First, second, and third parallel arm resonators 204, 205, and 206, inductors 207 to 209, and a capacitor 210, which are arranged on parallel arms 212, 213, and 214 that connect the potential, respectively. The first series arm resonator 201 includes surface acoustic wave resonators 201a, 201b, and 201c. The second series arm resonator 202 includes surface acoustic wave resonators 202a, 202b, and 202c. The third series arm resonator 203 includes surface acoustic wave resonators 203a, 203b, and 203c. The first parallel arm resonator 204 includes surface acoustic wave resonators 204a and 204b. The second parallel arm resonator 205 includes surface acoustic wave resonators 205a and 205b. The third parallel arm resonator 206 includes surface acoustic wave resonators 206a and 206b. The surface acoustic wave resonators 201a, 201b, 201c, 202a, 202b, 202c, 203a, 203b, 203c, 204a, 204b, 205a, 205b, 206a, and 206b each have one IDT and the surface acoustic wave propagation direction of the IDT. A pair of reflectors arranged on both sides. One end of the inductor 207 is connected to the ground potential, and the other end is connected to a common connection point between the first parallel arm resonator 204 and the second parallel arm resonator 205. One end of the inductor 208 is connected to the ground potential, and the other end is connected to the third parallel arm resonator 206. The inductor 209 and the capacitor 210 are connected between the third series arm resonator 203 and the transmission terminal 5.

  On the other hand, a reception filter 10 is connected between the antenna terminal 2 and the first and second reception terminals 3 and 4. The reception filter 10 includes a balanced longitudinally coupled resonator type surface acoustic wave filter having a balanced-unbalanced conversion function. That is, in the reception filter 10, an unbalanced signal is input from the antenna terminal 2 side, and a balanced signal is output from the first and second reception terminals 3 and 4.

  The reception filter 10 is configured so that the input impedance is 50Ω and the output impedance is 100Ω. That is, the reception filter 10 also has an impedance conversion function.

  The reception filter 10 is configured as follows so as to have the balance-unbalance conversion function and the impedance conversion function.

The reception filter 10 includes a first longitudinally coupled resonator type surface acoustic wave filter unit 101, a second longitudinally coupled resonator type surface acoustic wave filter unit 102, and a third longitudinally coupled resonator type surface acoustic wave filter unit. 103, a fourth longitudinally coupled resonator type surface acoustic wave filter unit 104, and a surface acoustic wave resonator 105. The first to fourth longitudinally coupled resonator type surface acoustic wave filter units 101 to 104 and the surface acoustic wave resonator 105 are configured by forming electrodes made of Al on a piezoelectric substrate. Although not particularly limited, in the present embodiment, the piezoelectric substrate is a 40 ° ± 5 ° Y-cut X-propagating LiTaO ₃ substrate.

  One end of a surface acoustic wave resonator 105 is connected to the antenna terminal 2. The surface acoustic wave resonator 105 includes an IDT 151 and reflectors 152 and 153 disposed on both sides of the IDT 151 in the surface acoustic wave propagation direction.

  First and second longitudinally coupled resonator type surface acoustic wave filter portions 101 and 102 are connected to the end of the surface acoustic wave resonator 105 opposite to the side connected to the antenna terminal 2. .

  The first longitudinally coupled resonator-type surface acoustic wave filter unit 101 includes first, second, and third IDTs 111, 112, and 113 arranged along the surface acoustic wave propagation direction, and the first, second, and second IDTs. And reflectors 114 and 115 arranged on both sides of the surface acoustic wave propagation direction of the portion where the three IDTs 111, 112 and 113 are provided. That is, the first longitudinally coupled resonator type surface acoustic wave filter unit 101 is a 3IDT type longitudinally coupled resonator type surface acoustic wave filter.

  The second longitudinally coupled resonator-type surface acoustic wave filter unit 102 includes first, second, and third IDTs 121, 122, and 123 disposed along the surface acoustic wave propagation direction, and the first, second, and second IDTs. And reflectors 124 and 125 arranged on both sides of the surface acoustic wave propagation direction of the portion where the three IDTs 121, 122 and 123 are provided. That is, the second longitudinally coupled resonator type surface acoustic wave filter unit 102 is also a 3IDT type longitudinally coupled resonator type surface acoustic wave filter.

  In the present embodiment, the third longitudinally coupled resonator type surface acoustic wave filter unit 103 is cascade-connected to the first longitudinally coupled resonator type surface acoustic wave filter unit 101. Similarly, the third longitudinally coupled resonator type surface acoustic wave filter unit 103 is also a 3IDT type longitudinally coupled resonator type surface acoustic wave filter. Accordingly, the third longitudinally coupled resonator type surface acoustic wave filter unit 103 includes the first, second, and third IDTs 131, 132, and 133 disposed along the surface acoustic wave propagation direction, and the first and second IDTs. And reflectors 134 and 135 disposed on both sides of the surface acoustic wave propagation direction of the portion where the third IDTs 131, 132 and 133 are provided.

  On the other hand, a fourth longitudinally coupled resonator type surface acoustic wave filter unit 104 is cascade-connected to the second longitudinally coupled resonator type surface acoustic wave filter unit 102. Similarly, the fourth longitudinally coupled resonator type surface acoustic wave filter unit 104 is also a 3IDT type longitudinally coupled resonator type surface acoustic wave filter. Accordingly, the fourth longitudinally coupled resonator type surface acoustic wave filter unit 104 includes the first, second, and third IDTs 141, 142, and 143 disposed along the surface acoustic wave propagation direction, and the first and second IDTs. And reflectors 144 and 145 disposed on both sides of the surface acoustic wave propagation direction of the portion where the third IDTs 141, 142 and 143 are provided.

  One end of the second IDT 112 of the first longitudinally coupled resonator type surface acoustic wave filter unit 101 is connected to the surface acoustic wave resonator 105 and the other end is connected to the ground potential. That is, the second IDT 112 of the first longitudinally coupled resonator type surface acoustic wave filter unit 101 is an IDT connected to the antenna terminal 2 via the surface acoustic wave resonator 105. One end of the first IDT 111 of the first longitudinally coupled resonator type surface acoustic wave filter unit 101 is connected to the ground potential, and the other end is the first of the third longitudinally coupled resonator type surface acoustic wave filter unit 103. Connected to the IDT 131. One end of the third IDT 113 of the first longitudinally coupled resonator type surface acoustic wave filter unit 101 is connected to the ground potential, and the other end is the third of the third longitudinally coupled resonator type surface acoustic wave filter unit 103. Connected to the IDT 133. Accordingly, the first IDT 111 and the third IDT 113 of the first longitudinally coupled resonator type surface acoustic wave filter unit 101 are IDTs on the side not connected to the antenna terminal 2.

  The third longitudinally coupled resonator type surface acoustic wave filter unit 103 has a first IDT 131 opposite to the side connected to the first IDT 111 of the first longitudinally coupled resonator type surface acoustic wave filter unit 101. The end is connected to the ground potential. Similarly, the side connected to the third IDT 113 of the first longitudinally coupled resonator type surface acoustic wave filter unit 101 of the third IDT 133 of the third longitudinally coupled resonator type surface acoustic wave filter unit 103 The opposite end is connected to ground potential. One end of the second IDT 132 of the third longitudinally coupled resonator type surface acoustic wave filter unit 103 is connected to the first receiving terminal 3, and the other end is connected to the second receiving terminal 4.

  One end of the second IDT 122 of the second longitudinally coupled resonator type surface acoustic wave filter unit 102 is connected to the surface acoustic wave resonator 105, and the other end is connected to the ground potential. That is, the second IDT 122 of the second longitudinally coupled resonator type surface acoustic wave filter unit 102 is an IDT connected to the antenna terminal 2 through the surface acoustic wave resonator 105. One end of the first IDT 121 of the second longitudinally coupled resonator type surface acoustic wave filter unit 102 is connected to the ground potential, and the other end is the first of the fourth longitudinally coupled resonator type surface acoustic wave filter unit 104. The IDT 141 is connected. One end of the third IDT 123 of the second longitudinally coupled resonator type surface acoustic wave filter unit 102 is connected to the ground potential, and the other end is the third length of the fourth longitudinally coupled resonator type surface acoustic wave filter unit 104. Connected to the IDT 143. Accordingly, the first IDT 121 and the third IDT 123 of the second longitudinally coupled resonator type surface acoustic wave filter unit 102 are IDTs on the side not connected to the antenna terminal 2.

  The fourth longitudinally coupled resonator type surface acoustic wave filter unit 104 has a first IDT 141 opposite to the side connected to the first IDT 121 of the second longitudinally coupled resonator type surface acoustic wave filter unit 102. The end is connected to the ground potential. Similarly, what is the side connected to the third IDT 123 of the second longitudinally coupled resonator type surface acoustic wave filter unit 102 of the third IDT 143 of the fourth longitudinally coupled resonator type surface acoustic wave filter unit 104? The opposite end is connected to ground potential. One end of the second IDT 142 of the fourth longitudinally coupled resonator type surface acoustic wave filter unit 104 is connected to the first receiving terminal 3, and the other end is connected to the second receiving terminal 4. More specifically, one end of the second IDT 142 of the fourth longitudinally coupled resonator type surface acoustic wave filter unit 104 is one end of the second IDT 132 of the third longitudinally coupled resonator type surface acoustic wave filter unit 103. And is connected to the first receiving terminal 3. Similarly, the other end of the second IDT 142 of the fourth longitudinally coupled resonator type surface acoustic wave filter unit 104 is connected to the other end of the second IDT 132 of the third longitudinally coupled resonator type surface acoustic wave filter unit 103. Commonly connected and connected to the second receiving terminal 4.

  In the present embodiment, one end of the second IDTs 132 and 142 of the third and fourth longitudinally coupled resonator-type surface acoustic wave filter units 103 and 104 is the first receiving terminal 3 and the other end is the second receiving terminal. 4, it is possible to output a balanced signal from the first and second receiving terminals 3 and 4.

  In FIG. 1, it should be pointed out that the IDTs of the first to fourth longitudinally coupled resonator type surface acoustic wave filter units 101 to 104 are schematically shown. In the present embodiment, in the first to fourth longitudinally coupled resonator type surface acoustic wave filter units 101 to 104, narrow pitch electrode finger portions are provided at the end portions of the IDTs in the portions where the IDTs are adjacent to each other. . A narrow pitch electrode finger part is a part where the period of the electrode finger which comprises IDT is smaller than the period of the electrode finger of the other part of the said IDT in which the narrow pitch electrode finger part is formed.

  In the reception filter 10, the IDTs connected to the antenna terminals 2 of the first and second longitudinally coupled resonator type surface acoustic wave filter units 101 and 102 are the second IDTs 112 and 122 as described above. The wavelength of the acoustic wave determined by the period of the electrode fingers of the second IDTs 112 and 122 of the first and second longitudinally coupled resonator type surface acoustic wave filter units 101 and 102 is λ1. The IDTs that are not connected to the antenna terminals 2 of the first and second longitudinally coupled resonator type surface acoustic wave filter units 101 and 102 are the first IDTs 111 and 121 and the third IDTs 113 and 123, as described above. is there. The wavelength of the acoustic wave determined by the period of the electrode fingers of the first IDTs 111 and 121 and the third IDTs 113 and 123 of the first and second longitudinally coupled resonator type surface acoustic wave filter units 101 and 102 is λ2. A feature of the present embodiment is that λ1 <λ2, so that ripples can be hardly generated in the passband of the transmission filter 20. This will be specifically described by the following experimental example.

  The reception filter 10 was designed according to the following design parameters. Note that the wavelength of the elastic wave determined by the period of the electrode fingers is λI.

1) First longitudinally coupled resonator type surface acoustic wave filter unit 101
Cross width of the first, second and third IDTs 111, 112 and 113: 19.1λI
Number of electrode fingers of the first IDT 111 and the third IDT 113: 33. However, three of the 33 narrow pitch electrode fingers are provided adjacent to the second IDT 112.
Number of electrode fingers of second IDT 112: 36. However, eight narrow pitch electrode fingers are provided in portions adjacent to the first and third IDTs 111 and 113 among the 36.
Number of electrode fingers of reflectors 114 and 115: 75 Metallization ratio of first, second and third IDTs 111, 112 and 113 and reflectors 114 and 115: 0.70
Electrode film thickness of the first, second and third IDTs 111, 112, 113 and reflectors 114, 115: 0.087λI

  The wavelength λI of the elastic wave in the second IDT 112 corresponds to the above-described λ1, and its value is 1.999 μm. In addition, the wavelength λI of the elastic wave in the first and third IDTs 111 and 113 corresponds to the above-described λ2, and its value is 2.001 μm. Therefore, λ1 <λ2.

2) Second longitudinally coupled resonator type surface acoustic wave filter unit 102
The second longitudinally coupled resonator type surface acoustic wave filter unit 102 has the same design as the first longitudinally coupled resonator type surface acoustic wave filter unit 101. Therefore, the wavelength λI of the elastic wave in the second IDT 122 corresponds to the above-described λ1, and its value is 1.999 μm. In addition, the wavelength λI of the elastic wave in the first and third IDTs 121 and 123 corresponds to the above-described λ2, and its value is 2.001 μm. Therefore, λ1 <λ2.

3) Third longitudinally coupled resonator type surface acoustic wave filter unit 103
Cross width of the first, second and third IDTs 131, 132 and 133: 16.0λI
Number of electrode fingers of the first IDT 131 and the third IDT 133: 33. However, three of the 33 narrow pitch electrode fingers are provided adjacent to the second IDT 132.
Number of electrode fingers of second IDT 132: 38. However, six narrow-pitch electrode fingers are provided in portions adjacent to the first and third IDTs 131 and 133 among the 38.
Number of electrode fingers of reflectors 134 and 135: 75 Metallization ratio of first, second and third IDTs 131, 132 and 133 and reflectors 134 and 135: 0.70
Electrode film thickness of the first, second and third IDTs 131, 132, 133 and reflectors 134, 135: 0.087λI

4) Fourth longitudinally coupled resonator type surface acoustic wave filter unit 104
The fourth longitudinally coupled resonator type surface acoustic wave filter unit 104 was designed in the same manner as the third longitudinally coupled resonator type surface acoustic wave filter unit 103.

5) Surface acoustic wave resonator 105
Also in the surface acoustic wave resonator 105, the wavelength of the elastic wave determined by the period of the electrode finger of the IDT 151 is λI.

Cross width of IDT 151: 14.4λI
Number of electrode fingers of IDT 151: 201 Number of electrode fingers of reflectors 152 and 153: 18 Metallization ratio of IDT 151 and reflectors 152 and 153: 0.60
Electrode film thickness of IDT 151 and reflectors 152 and 153: 0.089λI

6) Design of Transmission Filter As the transmission filter 20, a surface acoustic wave filter having the circuit configuration shown in FIG. The design parameters are as follows. Note that the wavelength of the elastic wave determined by the period of the electrode fingers is λII.

First series arm resonator 201
IDT electrode finger pairs in surface acoustic wave resonators 201a, 201b, and 201c: 177 pairs IDT crossover width in surface acoustic wave resonators 201a, 201b, and 201c: 13.15λII
Number of electrode fingers of reflectors in the surface acoustic wave resonators 201a, 201b, and 201c: 21 The surface acoustic wave resonators 201a, 201b, and 201c have the same design parameters.

Second series arm resonator 202
IDT electrode finger pairs in surface acoustic wave resonators 202a, 202b, 202c: 190 pairs IDT crossover width in surface acoustic wave resonators 202a, 202b, 202c: 25.21λII
Number of electrode fingers of reflectors in the surface acoustic wave resonators 202a, 202b, 202c: 21 The surface acoustic wave resonators 202a, 202b, 202c have the same design parameters.

Third series arm resonator 203
IDT electrode finger pairs in the surface acoustic wave resonators 203a, 203b, and 203c: 161 pairs IDT crossover width in the surface acoustic wave resonators 203a, 203b, and 203c: 20.48λII
Number of electrode fingers of reflectors in the surface acoustic wave resonators 203a, 203b, 203c: 21 The surface acoustic wave resonators 203a, 203b, 203c have the same design parameters.

First parallel arm resonator 204
IDT electrode finger pairs in surface acoustic wave resonators 204a and 204b: 167 pairs IDT crossover width in surface acoustic wave resonators 204a and 204b: 26.77λII
Number of electrode fingers of reflectors in surface acoustic wave resonators 204a and 204b: 21 The surface acoustic wave resonators 204a and 204b have the same design parameters.

Second parallel arm resonator 205
Number of electrode fingers of IDT in surface acoustic wave resonators 205a and 205b: 166 pairs Cross width of IDT in surface acoustic wave resonators 205a and 205b: 25.12λII
Number of electrode fingers of reflectors in surface acoustic wave resonators 205a and 205b: 21 The surface acoustic wave resonators 205a and 205b have the same design parameters.

Third parallel arm resonator 206
IDT electrode finger pairs in surface acoustic wave resonators 206a and 206b: 127 pairs IDT crossover width in surface acoustic wave resonators 206a and 206b: 20.47λII
Number of electrode fingers of reflectors in surface acoustic wave resonators 206a and 206b: 21 The surface acoustic wave resonators 206a and 206b have the same design parameters.

  For comparison, a duplexer of the first comparative example was prepared. In the duplexer of the first comparative example, in the first longitudinally coupled resonator type surface acoustic wave filter unit 101, the wavelength λ2 of the acoustic wave in the first and third IDTs 111 and 113 is 2.001 μm, and in the second IDT 112 The wavelength λ1 of the elastic wave was set to 2.013 μm. Further, in the second longitudinally coupled resonator type surface acoustic wave filter unit 102, the wavelength λ2 of the elastic wave in the first and third IDTs 121 and 123 is 2.001 μm, and the wavelength λ1 of the elastic wave in the second IDT 122 is 2 013 μm. About the other point, it carried out similarly to the duplexer 1 of 1st Embodiment, and formed the duplexer of the 1st comparative example.

  Therefore, in the duplexer of the first comparative example, in the reception filter 10, the wavelength λ1 of the elastic wave in the second IDTs 112 and 122 connected to the antenna terminal 2 is the IDT that is not connected to the antenna terminal. And the third IDT 111, 121, 113, 123 is made larger than the wavelength λ2 of the elastic wave. That is, λ1> λ2.

  FIG. 2 shows the filter characteristics of the transmission filter 20 in the duplexer 1 of the first embodiment and the filter characteristics of the transmission filter in the duplexer of the first comparative example. In FIG. 2, a solid line shows the filter characteristic of the transmission filter 20 in the duplexer 1 of the first embodiment, and a broken line shows the filter characteristic of the transmission filter in the duplexer of the first comparative example.

  As is apparent from FIG. 2, in the duplexer of the first comparative example, ripple A is generated on the high pass band side of the transmission filter, and steepness is reduced on the high pass band side. On the other hand, in the duplexer 1 of the first embodiment, no ripple is observed on the high pass band side of the transmission filter 20, and the steepness on the high pass band side is excellent.

  Next, a duplexer of a second comparative example was prepared. In the second comparative example, in the first longitudinally coupled resonator type surface acoustic wave filter unit 101, the wavelength λ2 of the elastic wave in the first and third IDTs 111 and 113 and the wavelength λ1 of the elastic wave in the second IDT 112 are used. In the second longitudinally coupled resonator-type surface acoustic wave filter unit 102, the wavelength λ2 of the elastic wave in the first and third IDTs 121 and 123 and the wavelength λ1 of the elastic wave in the second IDT 122 And 2.001 μm. That is, λ1 = λ2. About the other point, it carried out similarly to the duplexer 1 of 1st Embodiment, and comprised the duplexer of the 2nd comparative example.

  FIG. 3 shows the filter characteristics of the transmission filter 20 in the duplexer 1 of the first embodiment and the filter characteristics of the transmission filter in the duplexer of the second comparative example. In FIG. 3, the solid line indicates the filter characteristic of the transmission filter 20 in the duplexer 1 of the first embodiment, and the broken line indicates the filter characteristic of the transmission filter in the duplexer of the second comparative example. FIG. 4 is an enlarged view of a portion surrounded by X in FIG. As is apparent from FIGS. 3 and 4, in the duplexer of the second comparative example, a ripple B is generated on the high pass band side of the transmission filter, and the steepness on the high pass band side is reduced. On the other hand, in the duplexer 1 of the first embodiment, no ripple is recognized on the high pass band side of the transmission filter 20, and the steepness on the high pass band side is excellent.

  As described above, in the duplexer 1 of the first embodiment, no ripple is generated on the high pass band side of the transmission filter 20. The reason for this will be described below.

  In the receiving filter 10, the second IDT 112 of the first longitudinally coupled resonator type surface acoustic wave filter unit 101 and the second IDT 122 of the second longitudinally coupled resonator type surface acoustic wave filter unit 102 are the surface acoustic wave. The antenna terminal 2 is connected via a wave resonator 105. Therefore, the second IDT 112 of the first longitudinally coupled resonator type surface acoustic wave filter unit 101 and the second IDT 122 of the second longitudinally coupled resonator type surface acoustic wave filter unit 102 are also included in the transmission filter 20. It will be electrically connected. Therefore, the characteristics of the second IDT 112 of the first longitudinally coupled resonator type surface acoustic wave filter unit 101 and the characteristics of the second IDT 122 of the second longitudinally coupled resonator type surface acoustic wave filter unit 102 are transmitted. The filter characteristics of the filter 20 will be affected.

  The response by the second IDT 112 of the first longitudinally coupled resonator type surface acoustic wave filter unit 101 and the response by the second IDT 122 of the second longitudinally coupled resonator type surface acoustic wave filter unit 102 are the reception filter 10. It occurs on the lower frequency side than the passband. As described above, the second IDT 112 of the first longitudinally coupled resonator type surface acoustic wave filter unit 101 and the second IDT 122 of the second longitudinally coupled resonator type surface acoustic wave filter unit 102 are connected to the transmission filter 20. Are also electrically connected, and if the response is located at a frequency within the pass band of the transmission filter 20, a ripple occurs within the pass band.

  The transmission-side passband of UMTS-BAND2 is 1850 to 1910 MHz, and the reception-side passband is 1930 to 1990 MHz. Therefore, the frequency interval between the transmission side passband and the reception side passband is 20 MHz.

  The transmission-side passband of UMTS-BAND3 is 1710 to 1795 MHz, and the reception-side passband is 1805 to 1880 MHz. Therefore, the frequency interval between the transmission side passband and the reception side passband is 20 MHz.

  The transmission side passband of UMTS-BAND8 is 880 to 915 MHz, and the reception side passband is 925 to 960 MHz. Therefore, the frequency interval between the transmission side passband and the reception side passband is 10 MHz.

  When the frequency interval between the transmission-side passband and the reception-side passband is as narrow as 10 to 20 MHz as in UMTS-BAND2, 3, 8, the above ripple occurs in the passband of the transmission filter 20. It becomes easy.

  In the duplexer 1 of the present embodiment, in the first longitudinally coupled resonator type surface acoustic wave filter unit 101 of the reception filter 10, the wavelength λ1 of the elastic wave in the second IDT 112 is the same as that in the first and third IDTs 111 and 113. The wavelength is smaller than the wavelength λ2 of the elastic wave. Also in the second longitudinally coupled resonator type surface acoustic wave filter unit 102, the wavelength λ1 of the acoustic wave in the second IDT 122 is made smaller than the wavelength λ2 of the acoustic wave in the first and third IDTs 121 and 123. ing. That is, in the duplexer 1 of the present embodiment, in the reception filter 10, the wavelength λ1 of the elastic wave in the second IDTs 112 and 122 that are IDTs connected to the antenna terminal 2 is the IDT that is not connected to the antenna terminal 2. The first and third IDTs 111, 113, 121, and 123 are set to be smaller than the wavelength λ2 of the elastic wave.

  As a result, the response by the second IDT 112 of the first longitudinally coupled resonator type surface acoustic wave filter unit 101 and the response by the second IDT 122 of the second longitudinally coupled resonator type surface acoustic wave filter unit 102 are: It is located higher than the pass band of the transmission filter 20. Thereby, no ripple is generated in the pass band of the transmission filter 20.

  In other words, the wavelength λ1 is made smaller than λ2 so that the response of the second IDTs 112 and 122, which are IDTs connected to the antenna terminal 2, appears on the higher side of the pass band of the transmission filter 20. ing.

  Note that the first and third IDTs 111 and 113 of the first longitudinally coupled resonator type surface acoustic wave filter unit 101 are acoustically coupled to the second IDT 112. Similarly, the first and third IDTs 121 and 123 of the second longitudinally coupled resonator-type surface acoustic wave filter unit 102 are acoustically coupled to the second IDT 122.

  That is, the first and third IDTs 111 and 113 of the first longitudinally coupled resonator type surface acoustic wave filter unit 101 and the first and third IDTs 121 and 113 of the second longitudinally coupled resonator type surface acoustic wave filter unit 102, 123 is only connected to the transmission filter 20 via acoustic coupling. Therefore, the wavelengths of the first and third IDTs 111 and 113 of the first longitudinally coupled resonator type surface acoustic wave filter unit 101 and the first and third of the second longitudinally coupled resonator type surface acoustic wave filter unit 102 are used. Even if the wavelengths of the IDTs 121 and 123 are increased, the influence on the transmission filter 20 is very small. Therefore, according to the duplexer 1 of the present embodiment, in the reception filter 10, the elastic wave wavelength λ <b> 1 in the second IDTs 112 and 122 that are IDTs connected to the antenna terminal 2 is not connected to the antenna terminal 2. Since the wavelength λ2 of the elastic wave in the first and third IDTs 111, 113, 121, and 123 which are IDTs is λ1 <λ2, ripples are generated on the high pass band side of the transmission filter 20. It can be surely prevented.

  When the IDT has a narrow pitch electrode finger as in the present embodiment, the wavelength of the elastic wave in the narrow pitch electrode finger is much smaller than the wavelength of the elastic wave in the other electrode finger portions of the IDT. Therefore, the response due to the narrow pitch electrode finger is located on the higher frequency side than the pass band of the transmission filter 20. Therefore, even if the narrow pitch electrode fingers are provided, the pass band of the transmission filter 20 is not affected.

  Next, as a modification of the first embodiment, duplexers of the following first to third modifications were produced, and the filter characteristics of the transmission filter 20 were measured.

  As a duplexer of the first modified example, in the first longitudinally coupled resonator type surface acoustic wave filter unit 101 in the first embodiment, the wavelength λ2 of the acoustic wave in the first and third IDTs 111 and 113 is set to 2. The wavelength λ1 of the elastic wave in the second IDT 112 was 1.999 μm. In the second longitudinally coupled resonator type surface acoustic wave filter unit 102, the wavelength λ2 of the elastic wave in the first and third IDTs 121 and 123 is set to 2.015 μm, and the wavelength λ1 of the elastic wave in the second IDT 122 is set to 1. It was set to 999 micrometers. Except for these, the duplexer 1 was the same as that of the first embodiment.

  FIG. 5 shows the filter characteristics of the transmission filter 20 in the duplexer 1 of the first embodiment and the filter characteristics of the transmission filter 20 in the duplexer of the first modification. In FIG. 5, a solid line indicates the filter characteristic of the transmission filter 20 in the duplexer 1 of the first embodiment, and a broken line indicates the filter characteristic of the transmission filter 20 in the duplexer of the first modification. As is apparent from FIG. 5, the transmission filter 20 in the duplexer of the first modification example has a slightly worse steepness in filter characteristics than the transmission filter 20 in the duplexer 1 of the first embodiment. Ripple does not appear on the high pass band side of the transmission filter 20. Therefore, also from the result of the first modification, in the reception filter 10, the wavelength λ1 of the elastic wave in the second IDTs 112 and 122 that are IDTs connected to the antenna terminal 2 is not connected to the antenna terminal 2. By setting λ1 <λ2 as the wavelength λ2 of the elastic wave in the first and third IDTs 111, 113, 121, and 123 that are IDTs, it is ensured that ripples are generated on the high pass band side of the transmission filter 20. It can be seen that it can be prevented.

  As a duplexer of the second modification, in the third longitudinally coupled resonator-type surface acoustic wave filter unit 103 in the first embodiment, the wavelength of the elastic wave in the second IDT 132 is set to the first and third IDTs 131, It was made smaller than the wavelength of the elastic wave at 133. Further, in the fourth longitudinally coupled resonator type surface acoustic wave filter unit 104, the wavelength of the elastic wave in the second IDT 142 is made smaller than the wavelength of the elastic wave in the first and third IDTs 141 and 143. Except for these, the duplexer 1 was the same as that of the first embodiment. Therefore, in the duplexer of the second modification, the second and second IDTs connected to the antenna terminal 2 in the first and second longitudinally coupled resonator-type surface acoustic wave filter portions 101 and 102 of the reception filter 10 are also used. The wavelength λ1 of the elastic wave in the IDTs 112 and 122 and the wavelength λ2 of the elastic wave in the first and third IDTs 111, 113, 121, and 123 that are not connected to the antenna terminal 2 are λ1 <λ2. ing.

  FIG. 6 shows the filter characteristics of the transmission filter 20 in the duplexer 1 of the first embodiment and the filter characteristics of the transmission filter 20 in the duplexer of the second modification. In FIG. 6, a solid line indicates the filter characteristic of the transmission filter 20 in the duplexer 1 of the first embodiment, and a broken line indicates the filter characteristic of the transmission filter 20 in the duplexer of the second modification. As apparent from FIG. 6, no ripple appears on the high pass band side of the transmission filter 20 in the duplexer of the second modified example.

  As a duplexer of the third modification, in the third longitudinally coupled resonator type surface acoustic wave filter unit 103 in the first embodiment, the wavelength of the elastic wave in the second IDT 132 is set to the first and third IDTs 131, It was larger than the wavelength of the elastic wave at 133. Further, in the fourth longitudinally coupled resonator type surface acoustic wave filter unit 104, the wavelength of the elastic wave in the second IDT 142 is made larger than the wavelength of the elastic wave in the first and third IDTs 141 and 143. Except for these, the duplexer 1 was the same as that of the first embodiment. Therefore, in the duplexer of the third modified example, the second and second IDTs connected to the antenna terminal 2 in the first and second longitudinally coupled resonator type surface acoustic wave filter units 101 and 102 of the reception filter 10 are also used. The wavelength λ1 of the elastic wave in the IDTs 112 and 122 and the wavelength λ2 of the elastic wave in the first and third IDTs 111, 113, 121, and 123 that are not connected to the antenna terminal 2 are λ1 <λ2. ing.

  FIG. 7 shows the filter characteristics of the transmission filter 20 in the duplexer 1 of the first embodiment and the filter characteristics of the transmission filter 20 in the duplexer of the third modification. In FIG. 7, the solid line indicates the filter characteristic of the transmission filter 20 in the duplexer 1 of the first embodiment, and the broken line indicates the filter characteristic of the transmission filter 20 in the duplexer of the third modification. As is apparent from FIG. 7, no ripple appears on the high pass band side of the transmission filter 20 even in the duplexer of the third modification.

  The first to third IDTs 131 to 133 of the third longitudinally coupled resonator type surface acoustic wave filter unit 103 and the first to third IDTs 141 of the fourth longitudinally coupled resonator type surface acoustic wave filter unit 104. ˜143 are connected to the transmission filter 20 through acoustic coupling. Therefore, the influence on the transmission filter 20 by the first to third IDTs 131 to 133 and 141 to 143 of the third and fourth longitudinally coupled resonator type surface acoustic wave filter units 103 and 104 is very small. Therefore, also in the duplexers of the second and third modified examples, similarly to the duplexer 1 of the first embodiment, the second IDT 112 that is the IDT connected to the antenna terminal 2 in the reception filter 10. , 122, and the wavelength λ2 of the elastic wave in the first and third IDTs 111, 113, 121, 123, which are IDTs not connected to the antenna terminal 2, are set as λ1 <λ2. It can be seen that ripples can be reliably prevented from occurring on the high band side of the transmission filter 20.

  Next, in the reception filter 10 of the duplexer 1 according to the first embodiment, the wavelength λ1 of the elastic wave in the second IDTs 112 and 122 that are IDTs connected to the antenna terminal 2 is connected to the antenna terminal 2. It was examined how much smaller than the wavelength λ2 of the elastic wave in the first and third IDTs 111, 113, 121, and 123 that are not IDTs. The results are shown in FIG.

  FIG. 8 shows the wavelength of the acoustic wave in the first and third IDTs 111 and 113 in the first longitudinally coupled resonator type surface acoustic wave filter 101 of the reception filter 10 of the duplexer 1 of the first embodiment. 4 shows the result of measuring the steepness of the transmission filter 20 on the high pass band side by changing the wavelength λ1 of the elastic wave in the second IDT 112. FIG. The horizontal axis of FIG. 8 is the ratio λ1 / λ2, and the vertical axis is the frequency position where the attenuation is 3.4 dB and the frequency position where the attenuation is 40 dB on the high side of the pass band of the transmission filter 20. The frequency difference is shown. In the second longitudinally coupled resonator type surface acoustic wave filter unit 102, the ratio λ1 / λ2 is changed in the same manner as the first longitudinally coupled resonator type surface acoustic wave filter unit 101.

  The frequency interval between the transmission-side passband and the reception-side passband of UMTS-BAND2 is 20 MHz. In consideration of frequency variation due to frequency temperature characteristics and processing variation, the steepness is preferably 11 MHz or less.

  As can be seen from FIG. 8, when λ1 / λ2 is smaller than 1.0, the steepness is almost saturated, and when λ1 / λ2 is 0.998 or less, a steepness of 11 MHz or less is obtained. . Therefore, it is preferable that λ1 / λ2 is 0.998 or less.

  In the duplexer 1 of the first embodiment, the reception filter 10 includes the first to fourth longitudinally coupled resonator type surface acoustic wave filter units 101 to 104 and the surface acoustic wave resonator 105. In the duplexer according to the present invention, the reception filter is not limited to such a configuration.

  Hereinafter, second to fifth embodiments having different reception filter forms will be described. In addition, in FIG. 9 to FIG. 12 which will be described later showing the second to fifth embodiments, the transmission filter 20 is not shown. In the second to fifth embodiments, the transmission filter 20 can be configured similarly to the first embodiment.

  FIG. 9 is a schematic circuit diagram of the duplexer 21 according to the second embodiment of this invention.

  In the duplexer 21 of the second embodiment, similarly to the duplexer 1 of the first embodiment, the reception filter 22 includes first to fourth longitudinally coupled resonator type surface acoustic wave filter units 101 to 104, and an elastic surface. And a wave resonator 105. The duplexer 21 of the second embodiment is different from the duplexer 1 of the first embodiment in that the third and fourth longitudinally coupled resonator type surface acoustic wave filter units 103 and 104 and the first and second receiving terminals. 3 and 4 are connected. That is, in the present embodiment, one end of the second IDT 132 of the third longitudinally coupled resonator type surface acoustic wave filter unit 103 is connected to the first receiving terminal 3, and the other end is connected to the ground potential. Yes. Similarly, one end of the second IDT 142 of the fourth longitudinally coupled resonator type surface acoustic wave filter unit 104 is connected to the second receiving terminal 4, and the other end is connected to the ground potential. Thus, the connection structure for outputting a balanced signal can be modified as appropriate.

  Also in the present embodiment, since the first and second longitudinally coupled resonator type surface acoustic wave filter portions 101 and 102 are configured in the same manner as in the first embodiment, the IDT connected to the antenna terminal 2 is also used. The wavelength λ1 of the elastic wave in the second IDTs 112 and 122, and the wavelength λ2 of the elastic wave in the first and third IDTs 111, 113, 121, and 123 that are not connected to the antenna terminal 2 are expressed as λ1. By setting <λ2, ripples can be reliably prevented from occurring on the high pass band side of the transmission filter 20.

  FIG. 10 is a schematic circuit diagram of the duplexer 31 according to the third embodiment of this invention.

  In the duplexer 31 of the third embodiment, the reception filter 32 includes a surface acoustic wave resonator 105 and first and second longitudinally coupled resonator type surface acoustic wave filter units 33 and 34. The first longitudinally coupled resonator type surface acoustic wave filter unit 33 includes first, second, and third IDTs 331, 332, and 333 disposed along the surface acoustic wave propagation direction, and the first, second, and second IDTs. And reflectors 334 and 335 disposed on both sides of the surface acoustic wave propagation direction of the portion where the three IDTs 331, 332 and 333 are provided. That is, the first longitudinally coupled resonator type surface acoustic wave filter unit 33 is a 3IDT type longitudinally coupled resonator type surface acoustic wave filter. Similarly, the second longitudinally coupled resonator type surface acoustic wave filter unit 34 is also a 3IDT type longitudinally coupled resonator type surface acoustic wave filter. Accordingly, the second longitudinally coupled resonator type surface acoustic wave filter unit 34 includes the first, second and third IDTs 341, 342, 343 arranged along the surface acoustic wave propagation direction, and the first, second. And reflectors 344 and 345 disposed on both sides of the surface acoustic wave propagation direction of the portion where the third IDTs 341, 342 and 343 are provided. A second longitudinally coupled resonator type surface acoustic wave filter unit 34 is cascade-connected to the first longitudinally coupled resonator type surface acoustic wave filter unit 33.

  In the present embodiment, one end of the second IDT 332 of the first longitudinally coupled resonator type surface acoustic wave filter unit 33 is connected to the antenna terminal 2 via the surface acoustic wave resonator 105, and the other end is ground potential. It is connected to the. One end of each of the first and third IDTs 331 and 333 is connected to the ground potential. The other end of the first IDT 331 is connected to one end of the first IDT 341 of the second longitudinally coupled resonator type surface acoustic wave filter unit 34. The other end of the first IDT 341 is connected to the ground potential. Similarly, the other end of the third IDT 333 is connected to one end of the third IDT 343 of the second longitudinally coupled resonator type surface acoustic wave filter unit 34. The other end of the third IDT 343 is connected to the ground potential.

  The second IDT 342 of the second longitudinally coupled resonator type surface acoustic wave filter unit 34 is divided in the surface acoustic wave propagation direction, and has first and second divided IDT units 342a and 342b. The first divided IDT unit 342 a is connected to the first receiving terminal 3. The second divided IDT unit 342 b is connected to the second reception terminal 4.

  Even in such a configuration, the wavelength λ1 of the acoustic wave in the second IDT 332 of the first longitudinally coupled resonator type surface acoustic wave filter unit 33, which is the IDT connected to the antenna terminal 2, and the antenna terminal 2 By setting λ1 <λ2 as the wavelength λ2 of the elastic wave in the first and third IDTs 331 and 333, which are not connected IDTs, the generation of ripples on the high pass band side of the transmission filter 20 is ensured. Can be prevented.

  FIG. 11 is a schematic circuit diagram of a duplexer 41 according to the fourth embodiment of the present invention.

  In the duplexer 41 of the fourth embodiment, the reception filter 42 includes a surface acoustic wave resonator 105 and first and second longitudinally coupled resonator type surface acoustic wave filter units 43 and 44.

  The first longitudinally coupled resonator-type surface acoustic wave filter unit 43 includes first, second, and third IDTs 431, 432, and 433 disposed along the surface acoustic wave propagation direction, and the first, second, and second IDTs. And reflectors 434 and 435 disposed on both sides of the surface acoustic wave propagation direction of the portion where the three IDTs 431, 432 and 433 are provided. That is, the first longitudinally coupled resonator type surface acoustic wave filter unit 43 is a 3IDT type longitudinally coupled resonator type surface acoustic wave filter. Similarly, the second longitudinally coupled resonator type surface acoustic wave filter unit 44 is also a 3IDT type longitudinally coupled resonator type surface acoustic wave filter. Accordingly, the second longitudinally coupled resonator type surface acoustic wave filter unit 44 includes the first, second, and third IDTs 441, 442, 443, and the first, second, arranged along the surface acoustic wave propagation direction. And reflectors 444 and 445 disposed on both sides of the surface acoustic wave propagation direction of the portion where the third IDTs 441, 442 and 443 are provided. The first longitudinally coupled resonator type surface acoustic wave filter unit 43 and the second longitudinally coupled resonator type surface acoustic wave filter unit 44 are connected in parallel.

  In the present embodiment, the first and third IDTs 431 and 433 of the first longitudinally coupled resonator type surface acoustic wave filter unit 43 are connected in common to the antenna terminal 2 via the surface acoustic wave resonator 105. Each other end is connected to a ground potential. One end of the second IDT 432 is connected to the ground potential, and the other end is connected to the first receiving terminal 3.

  Similarly, one end of each of the first and third IDTs 441 and 443 of the second longitudinally coupled resonator type surface acoustic wave filter unit 44 is connected in common and connected to the antenna terminal 2 via the surface acoustic wave resonator 105. Each other end is connected to a ground potential. One end of the second IDT 442 is connected to the ground potential, and the other end is connected to the second receiving terminal 4.

  Even in such a configuration, the first and third IDTs 431 and 433 and the second longitudinally coupled resonance of the first longitudinally coupled resonator type surface acoustic wave filter unit 43, which are IDTs connected to the antenna terminal 2, are used. The first longitudinally coupled resonator type surface acoustic wave filter, which is the wavelength λ1 of the elastic wave in the first and third IDTs 441 and 443 of the child type surface acoustic wave filter unit 44 and the IDT not connected to the antenna terminal 2 By setting the wavelength λ2 of the acoustic wave in the second IDT 432 of the unit 43 and the second IDT 442 of the second longitudinally coupled resonator type surface acoustic wave filter unit 44 to λ1 <λ2, the pass band of the transmission filter 20 is obtained. The occurrence of ripples on the high frequency side can be reliably prevented.

  FIG. 12 is a schematic circuit diagram of the duplexer 51 according to the fifth embodiment of this invention.

  In the duplexer 51 of the fifth embodiment, the reception filter 52 includes a surface acoustic wave resonator 105 and a longitudinally coupled resonator type surface acoustic wave filter unit 53.

  The longitudinally coupled resonator type surface acoustic wave filter unit 53 is provided with first to fifth IDTs 531 to 535 and first to fifth IDTs 531 to 535 arranged along the surface acoustic wave propagation direction. Reflectors 536 and 537 arranged on both sides of the surface acoustic wave propagation direction. That is, the longitudinally coupled resonator type surface acoustic wave filter unit 53 is a 5IDT type longitudinally coupled resonator type surface acoustic wave filter.

  In the present embodiment, the first, third, and fifth IDTs 531, 533, and 535 of the longitudinally coupled resonator-type surface acoustic wave filter unit 53 are connected in common, and the antenna terminal is connected via the surface acoustic wave resonator 105. 2 and each other end is connected to a ground potential. On the other hand, one end of the second IDT 532 is connected to the ground potential, and the other end is connected to the first receiving terminal 3. One end of the fourth IDT 534 is connected to the ground potential, and the other end is connected to the second reception terminal 4.

  Even in such a configuration, the wavelengths of the acoustic waves in the first, third, and fifth IDTs 531, 533, and 535 of the longitudinally coupled resonator-type surface acoustic wave filter unit 53 that is the IDT connected to the antenna terminal 2 By setting λ1 and the wavelength λ2 of the acoustic wave in the second and fourth IDTs 532 and 534, which are IDTs not connected to the antenna terminal 2, λ1 <λ2, the transmission filter 20 has a high passband side. It is possible to reliably prevent the occurrence of ripples.

  In the second to fifth embodiments, the configuration of the transmission filter 20 is omitted, but the transmission filter 20 can be configured in the same manner as in the first embodiment. Further, as described above, the present invention is characterized in the relationship between the wavelength λ1 of the elastic wave in the IDT connected to the antenna terminal and the wavelength λ2 of the elastic wave in the IDT not connected to the antenna terminal, as described above. The transmission filter structure itself is not particularly limited.

  In the first to fifth embodiments and the first to third comparative examples, the reception filter is configured by the longitudinally coupled resonator type surface acoustic wave filter using the surface acoustic wave. However, the longitudinal filter using the boundary acoustic wave is used. The reception filter may be configured by a coupled resonator type boundary acoustic wave filter.

DESCRIPTION OF SYMBOLS 1 ... Duplexer 2 ... Antenna terminal 3, 4 ... 1st, 2nd receiving terminal 5 ... Transmission terminal 6 ... Inductor 10 ... Reception filter 20 ... Transmission filter 21 ... Duplexer 22 ... Reception filter 31 ... Duplexer 32 ... Reception filter 33 ... First longitudinally coupled resonator type surface acoustic wave filter unit 34 ... Second longitudinally coupled resonator type surface acoustic wave filter unit 41 ... Duplexer 42 ... Reception filter 43 ... First longitudinally coupled resonator type surface acoustic wave filter unit 44 ... 2nd longitudinally coupled resonator type surface acoustic wave filter unit 51 ... Duplexer 52 ... receiving filter 53 ... longitudinally coupled resonator type surface acoustic wave filter unit 101 ... 1st longitudinally coupled resonator type surface acoustic wave filter unit 102 2nd longitudinally coupled resonator type surface acoustic wave filter unit 103 3rd longitudinally coupled resonator type surface acoustic wave filter unit 104 4th longitudinal direction If resonator type surface acoustic wave filter unit 105 ... surface acoustic wave resonators 111 to 113 ... first to third IDT
114, 115 ... reflectors 121-123 ... first to third IDTs
124, 125 ... reflectors 131-133 ... first to third IDTs
134, 135 ... reflectors 141 to 143 ... first to third IDTs
144, 145 ... reflector 151 ... IDT
DESCRIPTION OF SYMBOLS 152,153 ... Reflector 201 ... 1st series arm resonator 201a-201c ... Surface acoustic wave resonator 202 ... 2nd series arm resonator 202a-202c ... Surface acoustic wave resonator 203 ... 3rd series arm resonance Child 203a-203c ... Surface acoustic wave resonator 204 ... First parallel arm resonator 204a, 204b ... Surface acoustic wave resonator 205 ... Second parallel arm resonator 205a, 205b ... Surface acoustic wave resonator 206 ... Third Parallel arm resonators 206a, 206b ... Surface acoustic wave resonators 207-209 ... Inductors 210 ... Capacitors 211 ... Series arms 212-214 ... Parallel arms 331-333 ... First to third IDTs
334, 335 ... reflectors 341-343 ... first to third IDTs
342a, 342b ... 1st and 2nd divided IDT sections 344, 345 ... Reflectors 431-433 ... 1st-3rd IDT
434, 435 ... reflectors 441-443 ... first to third IDTs
444, 445 ... reflectors 531 to 535 ... first to fifth IDTs
536, 537 ... Reflector

Claims (8)

An elastic wave demultiplexer comprising an antenna terminal, a receiving terminal, and a transmitting terminal,
A receiving filter connected between the antenna terminal and the receiving terminal, comprising a longitudinally coupled resonator type acoustic wave filter;
A transmission filter connected between the antenna terminal and the transmission terminal;
The longitudinally coupled resonator type acoustic wave filter has at least three IDTs arranged along an acoustic wave propagation direction, and at least one of the at least three IDTs is connected to the antenna terminal. The remaining IDT is not connected to the antenna terminal,
Elastic wave demultiplexing where λ1 <λ2 where λ1 is the wavelength of the elastic wave in the IDT connected to the antenna terminal and λ2 is the wavelength of the elastic wave in the IDT not connected to the antenna terminal. vessel.   The elastic wave duplexer according to claim 1, wherein a ratio λ1 / λ2 of λ1 and λ2 is 0.998 or less. The receiving terminal has first and second receiving terminals;
The longitudinally coupled resonator type acoustic wave filter includes first and second 3IDT type longitudinally coupled resonator type acoustic wave filter units connected in parallel to the antenna terminal, and the first and second 3IDT type longitudinally coupled waves. A third and a fourth 3IDT type longitudinally coupled resonator type elastic wave filter unit connected in cascade to a resonator type elastic wave filter unit, respectively, and the third and fourth 3IDT type longitudinally coupled resonator type elastic waves. A wave filter unit is connected to each of the first and second receiving terminals, and the three IDTs of the first and second 3IDT type longitudinally coupled resonator type elastic wave filter units are arranged along an elastic wave propagation direction. When the first to third IDTs are used, the second IDTs of the first and second 3IDT type longitudinally coupled resonator type acoustic wave filter sections are connected to the antenna terminals, 1, the third IDT is connected to the antenna terminal Are not even, the acoustic wave duplexer according to claim 1 or 2. The receiving terminal has first and second receiving terminals;
The longitudinally coupled resonator type acoustic wave filter includes first and second 3IDT type longitudinally coupled resonator type acoustic wave filter portions connected in parallel to the antenna terminal, and the first and second 3IDT types. Longitudinal coupled resonator type acoustic wave filter units are connected to the first and second receiving terminals, respectively, and the three IDTs of the first and second 3IDT type longitudinally coupled resonator type acoustic wave filter units are provided. Is the first to third IDTs along the elastic wave propagation direction, the first and third IDTs of the first and second 3IDT type longitudinally coupled resonator type elastic wave filter units are: 3. The device according to claim 1, wherein the second IDT is connected to the antenna terminal and is not connected to the antenna terminal, and is connected to the first and second receiving terminals, respectively. Elastic wave splitter. The receiving terminal has first and second receiving terminals;
3. The acoustic wave component according to claim 1, wherein the longitudinally coupled resonator type acoustic wave filter is a 5 IDT type longitudinally coupled resonator type acoustic wave filter in which five IDTs are arranged along an acoustic wave propagation direction. Waver.   When the five IDTs in the 5IDT type longitudinally coupled resonator type acoustic wave filter are first to fifth IDTs along the acoustic wave propagation direction, the first, third, and fifth IDTs are the antenna terminals. The second IDT is not connected to the antenna terminal, the second IDT is the first receiving terminal, and the fourth IDT is the second receiving terminal. The elastic wave duplexer according to claim 5, connected to   The elastic wave duplexer according to any one of claims 1 to 6, which is a duplexer corresponding to a UMTS-BAND2, 3 or 8 standard.   The acoustic wave duplexer according to claim 1, wherein the longitudinally coupled resonator type acoustic wave filter is a longitudinally coupled resonator type surface acoustic wave filter.

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