WO2007129696A1

WO2007129696A1 - Transmission/reception switching device

Info

Publication number: WO2007129696A1
Application number: PCT/JP2007/059482
Authority: WO
Inventors: Hiroshi Tsuchiya
Original assignee: Ube Industries, Ltd.
Priority date: 2006-05-09
Filing date: 2007-05-08
Publication date: 2007-11-15
Also published as: JP2009182368A

Abstract

A transmission/reception switching device includes: a reception filter (7) having a first terminal (2) and a second terminal (4); a transmission filter (8) having a third terminal (3) and a fourth terminal (5); and an antenna terminal (1) connected to the first terminal (2) and the third terminal (3). The reception filter (7) and the transmission filter (8) are both ladder-type filters having a thin film bulk sound wave resonator (11). A phase matching inductor (9) has one end connected to the ground and the other end connected to a transmission line (10) which connects the first terminal (2), the third terminal (3), and the antenna terminal (1). When the phase matching inductor (9) is not connected to the transmission line (10), the reception filter (7) and the transmission filter (8) have a frequency with an admittance real part value 1 in the respective pass bands and a frequency with the same admittance imaginary part value in four bands, i.e., the pass band and a cut-off band of the reception filter (7) and the pass band and a cut-off band of the transmission filter (8), and have a capacitance in the four bands.

Description

Specification

Duplexer

Technical field

The present invention relates to a duplexer that is an electronic device, and more specifically, a duplexer using a thin film Balta acoustic resonator (FBAR) filter configured using a thin film Balta acoustic resonator (FBAR). About.

Background art

In recent years, development of small communication devices typified by mobile phones has been actively promoted. These small communication devices use a duplexer for branching transmission / reception signals. In order to realize a smaller and higher performance communication device, a smaller duplexer and higher performance are required. I'm going. In recent wireless communications, a high-frequency band is often used, and a thin film Balta acoustic resonator (FBAR) filter that can control the use frequency by changing the thickness of the piezoelectric region, that is, the piezoelectric layer. The use of is being considered.

[0003] Normally, the reception filter and the transmission filter of the duplexer need to control the phase at a predetermined frequency. For this reason, in a duplexer using a thin film Balta acoustic resonator (FBAR) filter, a 90 ° phase shifter has been conventionally connected in series between the reception filter and the antenna terminal (Patent Document 1). reference).

Patent Document 1: Japanese Patent Application Laid-Open No. 2001-24476

Disclosure of the invention

Problems to be solved by the invention

[0005] The use of a 90 ° phase shifter as a phase matching circuit causes an increase in the thickness of the duplexer package or an increase in the mounting area, which is an obstacle to downsizing the duplexer.

[0006] The present invention has been made in view of the above circumstances, and a thin film Balta acoustic resonator (FBAR) filter in which the thickness and mounting area of the package are reduced by improving the phase matching circuit. An object of the present invention is to provide a small duplexer used.

Means for solving the problem [0007] According to the present invention, the above-mentioned object is achieved as follows:

A reception filter having a first terminal and a second terminal, a transmission filter having a third terminal and a fourth terminal, and a common terminal connected to the first terminal and the third terminal A duplexer with and comprising:

Each of the reception filter and the transmission filter is a ladder filter having a thin film Balta acoustic resonator,

The other end of the phase matching inductor having one end connected to the ground is connected to the transmission line connecting the first terminal, the third terminal, and the common terminal,

The reception filter and the transmission filter have a frequency at which the value of the real part of admittance is 1 in each pass band when the phase matching inductor is not connected to the transmission line, and the reception filter The imaginary part of the admittance has the same frequency in the four bands of the pass band and stop band of the transmission filter and the pass band and stop band of the transmission filter, and the four bands have the capacity. A transmission / reception switch,

Is provided.

In the present invention, the inductance of the phase matching inductor is set so that the transmission filter and the reception filter are phase matched when it is connected to the transmission line.

The invention's effect

[0009] According to the present invention, the length of the phase matching circuit can be reduced, the mounting area of the duplexer and the package thickness can be reduced, and the duplexer can be reduced in size. .

Brief Description of Drawings

FIG. 1 is a circuit diagram showing an embodiment of a duplexer according to the present invention.

FIG. 2 is a circuit diagram showing a duplexer for comparison using a 90 ° phase shifter.

FIG. 3 is a schematic cross-sectional view for explaining the structure of a thin film Balta acoustic resonator having a cavity portion.

[Fig.4] Schematic for explaining the structure of a thin-film Balta acoustic resonator with an acoustic mirror layer It is sectional drawing.

FIG. 5 is a circuit diagram showing a ladder filter.

Fig. 6 is a circuit diagram showing a ladder filter.

7] An admittance diagram showing filter characteristics before phase matching.

8] An admittance diagram showing the filter characteristics after phase matching.

9A] is a schematic configuration diagram of the duplexer in FIG.

9B] is a schematic configuration diagram of the duplexer in FIG.

10] FIG. 10 is an admittance diagram showing filter characteristics before phase matching of the reception filter according to the embodiment of the present invention.

11] FIG. 11 is an admittance diagram showing filter characteristics after phase matching of the reception filter according to the embodiment of the present invention.

FIG. 12 is an admittance diagram showing filter characteristics before phase matching of a transmission filter for comparison.

13] FIG. 13 is an admittance diagram showing filter characteristics before phase matching of the transmission filter according to the embodiment of the present invention.

FIG. 14 is an admittance diagram showing filter characteristics after phase matching of a transmission filter for comparison.

15] FIG. 15 is an admittance diagram showing the filter characteristics after phase matching of the transmission filter according to the embodiment of the present invention.

Explanation of symbols

1 Antenna terminal

2 Receive filter first terminal

3 Transmit filter third terminal

4 Receive filter second terminal

5 Transmit filter fourth terminal

6 90 ° phase shifter

7 Receive filter

8 Transmit filter 9 Phase matching inductor

9A Inductor

10 1 Transmission

11 Thin-film Balta acoustic resonator

12 Ladder filter

13 Upper electrode

14 Piezoelectric layer

15 Bottom electrode

16 substrate

17 Caviarity

18 Acoustic mirror layer

19 Resonant part

20 Passband

21 Stop band

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a circuit diagram showing an embodiment of a transmission / reception switching device of the present invention. The transmission / reception switching device of the present embodiment includes a reception thin film banolek acoustic resonator filter (hereinafter sometimes referred to as a “reception filter”) 7 having a first terminal 2 and a second terminal 4, Transmitting thin film banoroke sonic resonator filter (hereinafter sometimes referred to as “transmitting filter”) 8 having terminal 3 of 3 and fourth terminal 5 and first terminal 2 of receiving filter 7 through transmission line 10 And an antenna terminal 1 as a common terminal connected to the third terminal 3 of the transmission filter 8. A reception circuit (not shown) is connected to the second terminal 4 of the reception filter 7, a transmission circuit (not shown) is connected to the fourth terminal 5 of the transmission filter 8, and an antenna (not shown) is connected to the antenna terminal 1. Is connected. Each of the reception filter 7 and the transmission filter 8 is a ladder filter having a thin film Balta acoustic resonator (FBAR) 11.

[0013] One end of a phase matching inductor 9 is connected to the transmission line 10. The other end of the phase matching inductor 9 is connected to the ground. The reception filter 7 and transmission filter 8 are It has specific characteristics as described below. By adopting such a combination of the reception filter 7, the transmission filter 8, and the phase matching inductor 9, the small size characteristic of the thin film Baltha acoustic wave resonator can be utilized as described later, and a small size can be achieved. It is possible to provide a duplexer.

FIG. 3 is a schematic cross-sectional view for explaining the structure of the thin film Balta acoustic resonator 11. Figure

As shown in FIG. 3, the thin film Baltha acoustic resonator 11 includes a substrate 16 having a cavity portion 17 formed thereon by a concave portion, a patterned lower electrode 15 formed in order on the substrate 16, a piezoelectric layer 14 and a pattern. And a laminated body composed of the upper electrode 13 having the shape. The laminate is formed so as to straddle the cavity part 17 and has a resonance part 19 formed in a region corresponding to the cavity part 17. The resonance part 19 has a laminated structure in which the upper electrode 13, the piezoelectric layer 14, and the lower electrode 15 are overlapped when viewed in the film thickness direction. In the thin film Balta acoustic resonator 11, a passivation layer, a support layer, and the like may be provided on the upper surface of the upper electrode 13 and the lower surface of the lower electrode 15.

The upper electrode 13 is made of a suitable material such as molybdenum (Mo), gold (Au), aluminum (A1), ruthenium (Ru), platinum (Pt), tungsten (W), and titanium (Ti). Can be used.

[0016] As the piezoelectric layer 14, a layer made of an appropriate material such as aluminum nitride (A1N) and zinc oxide (ZnO) can be used.

[0017] As the lower electrode 15, molybdenum (Mo), gold (Au), aluminum (A1), ruthenium (

A material made of a suitable material such as Ru), platinum (Pt), tungsten (W) and titanium (Ti) can be used.

[0018] The substrate 16 includes silicon (Si), silicon oxide (SiO), gallium arsenide (GaAs), and gallium arsenide.

2

What consists of suitable materials, such as a lath, can be used.

In addition, as shown in FIG. 4, the thin film Balta acoustic resonator 11 is a layer having a high acoustic impedance between the substrate 16 and the laminate composed of the lower electrode 15, the piezoelectric layer 14, and the upper electrode 13. Or an acoustic mirror layer 18 formed by alternately laminating layers having low acoustic impedance. As a result, the energy generated by the resonance part 19 can be confined in the same manner as in the structure provided with the cavity part 17 as shown in FIG. In the acoustic mirror layer 18, gold (Au), molybdenum (Mo), and tungsten (W) forces can be used as the high acoustic impedance layer, and silicon (Si), an oxidation layer can be used as the low acoustic impedance layer. Using silicon (SiO 2) and aluminum (A1)

2

Can power s.

Next, a method for manufacturing the thin film Balta acoustic resonator 11 will be described. The thin film Balta acoustic resonator 11 having the cavity portion 17 as shown in FIG. 3 includes depositing the lower electrode 15 on the upper surface of the substrate 16 by a vapor deposition method such as sputtering, and patterning the desired shape. The piezoelectric layer 14 is deposited by a vapor deposition method such as sputtering, and a patterning is performed in a desired shape as necessary, and the upper electrode 13 is deposited by a vapor deposition method such as sputtering, and the patterning is performed in a desired shape. And the step of providing the cavity portion 17 on the substrate 16 by etching or the like. Further, this manufacturing method may include a step of providing a passivation layer, a support layer, or the like on the upper surface of the upper electrode 13 or the lower surface of the lower electrode 15.

[0022] A thin-film banolek acoustic resonator 11 having an acoustic mirror layer 18 as shown in FIG. 4 is formed by depositing a layer having a high acoustic impedance and a layer having a low acoustic impedance on a substrate 16 by a deposition method such as sputtering. The process of forming the acoustic mirror layer 18 by alternately laminating, the process of depositing the lower electrode 15 by a vapor deposition method such as sputtering, and patterning it into a desired shape, and the process of depositing the piezoelectric layer 14 by a vapor deposition method such as sputtering. Then, it is manufactured by a process of patterning a desired shape as required, and a process of depositing the upper electrode 13 by a vapor deposition method such as sputtering and patterning the desired shape. The manufacturing method may include a step of providing a passivation layer, a support layer, or the like on the upper surface of the upper electrode 13 or the lower surface of the lower electrode 15.

As shown in FIG. 1, in the reception filter 7, a plurality of thin film Balta acoustic resonators (hereinafter referred to as “the first terminal 2 and the second terminal 4”) connected in series. 11) and a plurality of thin film Balta acoustic resonators (hereinafter also referred to as “parallel resonators”) 11 connected in parallel. The parallel resonator 11 is connected to the ground via the inductor 9A. These series resonators 11 or parallel resonators 11 may have the same frequency characteristic or may have different frequency characteristics. The transmission filter 8 includes a plurality of series resonators 11 connected in series between the first terminal 3 and the second terminal 5 and a parallel resonator 11 connected in parallel. The parallel resonator 1 1 is connected to the ground via an inductor 9A. These series resonators 11 or parallel resonators 11 may have the same frequency characteristics or may have different frequency characteristics.

[0025] The reception filter 7 and the transmission filter 8 may be a ladder filter 12 as shown in FIG. In this ladder filter 12, the parallel resonator 11 is directly connected to the ground.

In addition, the reception filter 7 and the transmission filter 8 may be a ladder filter 12 as shown in FIG. In this ladder type filter 12, at least one of the thin film Balta acoustic resonators 11 in the ladder filter 12 shown in FIG. 5 is replaced with two thin film Balta acoustic resonators 11 connected in series.

As shown in FIG. 1, the antenna terminal 1, the first terminal 2 of the reception filter 7, and the third terminal 3 of the transmission filter 8 are connected by a transmission line 10 to obtain a desired filter characteristic. Therefore, the phase matching inductor 9 is interposed between the transmission line 10 and the ground. The transmission line 10 is provided in a package of a transmission / reception switch, and a reception signal and a transmission signal are transmitted. The phase matching inductor 9 may be provided in a line pattern on the package, or may be formed as a concentrated inductor.

The phase matching between the reception filter 7 and the transmission filter 8 is achieved by providing the phase matching inductor 9. Here, as the reception filter 7 and the transmission filter 8, a combination of those having the following characteristics is adopted.

[0029] FIG. 7 is an admittance diagram of the reception filter 7 or the transmission filter 8 before the phase matching inductor 9 is provided, that is, when the phase matching inductor 9 is not connected to the transmission line 10, and FIG. 3 is an admittance diagram of the reception filter 7 or the transmission filter 8 when the inductor 9 is provided, that is, when the phase matching inductor 9 is connected to the transmission line 10 as shown in FIG.

As shown in FIG. 7, in the transmission filter 7 and the reception filter 8, when the phase matching inductor 9 is not connected to the transmission line 10, the value of the real part of admittance is 1 in the passband 20. (I.e., the value of the real part of the admittance at any frequency in the passband 20 is 1 and the passband 20 is on the circle line indicating that the real part of the admittance is 1) In the four bands, the pass band 20 and stop band 21 of the reception filter 7 and the pass band 20 and stop band 21 of the transmission filter 8, the frequencies where the imaginary part of the admittance has the same value 0.5 are shown. (I.e., the imaginary part of the admittance at any frequency in the passband 20 and any frequency in the stopband 21 has the same value 0.5, and the imaginary part of the admittance value 0.5 line) Passes through passband 20 and stopband 21). Here, admittance is a numerical value normalized by setting the admittance value of the entire duplexer (specifically, for example, the admittance value corresponding to an impedance of 50 Ω) to 1 [the same applies below].

For example, in the case of the reception filter 7, the passband (1920 — 1980 MHz) has a frequency in which the real part of the admittance is 1 in the passband 20 and the stopband (2110 — 2170 MHz) 21. The imaginary part of the admittance has a frequency indicating the same value 0.5. Further, regarding the transmission filter 8, the pass band (2110-2170MHz) 20 has a frequency where the value of the real part of the admittance is 1, and the pass band 20 and the stop band (1920-1980MHz) 20 The imaginary part of the admittance has a frequency indicating the same value 0.5.

As shown in FIG. 8, the transmission filter 7 and the reception filter 8 have an admittance (for example, impedance) of the entire circuit in the passband 20 when the phase matching inductor 9 is connected to the transmission line 10. (Corresponding to 50 Ω) or an admittance or impedance value close to impedance, and in the cutoff band 21 has an admittance value much smaller than that of the entire duplexer, that is, an impedance value much larger than the impedance of the entire duplexer It has. In the transmission filter 7 and the reception filter 8, the value of the imaginary part of the admittance is sufficiently small in both the pass band 20 and the stop band 21.

[0033] For example, with respect to the reception filter 7, the passband (1920_1980) ζ) 20 has an admittance or impedance value close to that of the entire circuit, and the stopband (21 10_2170ΜΗζ) 21 is much more than that of the entire circuit. It has a small admittance value, that is, a very large impedance value. Furthermore, for the transmission filter 8, the passband In the region (2110-2170MHz) 20, the admittance or impedance value is close to that of the entire circuit, and in the stopband (1920—1980MHz) 21, the admittance value is much smaller than that of the entire circuit, that is, the impedance value is much larger. It has.

The reception filter 7 and the transmission filter 8 are capacitive in the pass band 20 and the stop band 21, respectively. This means that in FIG. 7, the pass band 20 and the stop band 21 of the reception filter 7 and the transmission filter 8 are located in the lower half of the chart. According to this, it is possible to obtain a duplexer having good characteristics as shown in FIG. 8 by performing phase matching with the addition of the phase matching inductor 9.

[0035] The inductance L of the phase matching inductor 9 can be determined as follows.

[0036] In passband 20, admittance Y is

In Figure 7, Y = 1.0 + 0.5j

In Figure 8, Y = 1.0 + 0. Oj

It becomes.

[0037] In stopband 21, admittance Y is

2

In Figure 7, Y = X + 0.5i

2

In Figure 8, Y = X + 0.Oj

2

It becomes.

[0038] The real part of the admittance Y does not change before and after the transition from the state of FIG. 7 to the state of FIG. 8 (that is, the addition of the phase matching inductor 9). The change of the imaginary part is

Y Y = 0.0j-0.5j = -0.5j

twenty one

And therefore

j _W L / 50 = l / (-0.5j)

WL / 50 = 2.0

L = 100 / _W = 100 / (2 πΐ) = 100 / (2 π X2045X10 ⁶ ) = 7.8 [nH]

It becomes. Here, the center frequency 2045 [MHz] between the pass band and the stop band was used as the value of the frequency f.

[0039] Each of the reception filter and the transmission filter is provided with this inductance. If these inductors are shared, the inductance of inductor 9 should be 3 · 9 [nH]. If the length of the inductor 9 is formed with a typical line width and pattern, it can be set to approximately 6.0 mm [mm] as described later.

[0040] Similarly, based on the imaginary part change, which is the difference between the imaginary part of admittance Y in the target phase matching state and the imaginary part of admittance Y before adding phase matching inductor 9. It will be understood that the required inductance of the phase matching inductor 9 can be set.

As described above, by using the reception filter 7 and the transmission filter 8 as described above, the phase matching amounts of the reception filter 7 and the transmission filter 8 can be made the same. Therefore, the other end of the phase matching inductor 9 whose one end is connected to the ground is connected to the transmission line 10 that connects the antenna terminal 1, the first terminal 2 of the reception filter 7, and the third terminal 3 of the transmission filter 8. By connecting, the phases of the reception filter 7 and the transmission filter 8 can be set to desired values.

Example

[0042] Hereinafter, the present invention will be described by way of examples. In this embodiment, the transmission / reception switch belonging to the present invention is compared with the tray / transmission / reception switch belonging to the present invention.

[0043] First, FIG. 2 shows a circuit diagram of a transmission / reception switch for comparison using a 90 ° phase shifter as described in Patent Document 1. In this figure, elements similar to those shown in FIG. 1 are given the same reference numerals. A 90 ° phase shifter 6 is interposed between the antenna terminal 1 and the third terminal 3 of the transmission filter 8 and the first terminal 2 of the reception filter 7.

FIG. 9A shows a schematic configuration diagram of this duplexer. In FIG. 9A, a plurality of dielectric substrates constituting the duplexer package and stacked are shown separated from each other. On the uppermost substrate, the chip of the reception filter 7 and the chip of the transmission filter 8 are mounted, and a conductor pattern constituting a part of the inductor 9A is formed. On the second layer substrate from the top, a conductor pattern constituting the other part of the inductor 9A is formed. The conductor pattern that forms the ground G is formed on the substrate in the third layer from the top. A through hole is formed in the fourth layer from the top. On the fifth layer from the top, the line conductor pattern of λ / 4 length that forms the 90 ° phase shifter 6 is formed. It is. A through-hole is formed in the sixth layer substrate from the top. On the seventh layer from the top, the conductor pattern that forms the ground G is formed.

[0045] Table 1 shows the line length necessary to form the / 4 length line-shaped conductor pattern constituting the 90 ° phase shifter 6. As shown in Table 1, in the duplexer shown in Fig. 2, the line length of the line conductor pattern of 90 ° phase shifter 6 needs to be 13.8 mm, and above and below this line conductor pattern. In addition, a ground G conductor pattern is required, and a distance of 0.2 mm is required between them. For this reason, the required number of substrates increases, the package becomes thicker and cannot be made smaller.

[0046] [Table 1]

[0047] On the other hand, FIG. 9B shows a schematic configuration diagram of the duplexer in FIG. In FIG. 9B, a plurality of dielectric substrates constituting the duplexer package and stacked are shown separated from each other. On the uppermost substrate, the chip of the reception filter 7 and the chip of the transmission filter 8 are mounted, and a conductor pattern constituting a part of the inductor 9A is formed. On the substrate of the second layer from the top, a conductor pattern that forms the other part of the inductor 9A is formed. On the substrate of the third layer from the top, a conductor pattern constituting the phase matching inductor 9 is formed, and a through hole is further formed. A conductive pattern composing the ground G is formed on the fourth layer from the top. [0048] In the duplexer shown in Fig. 1, the line length of the conductor pattern of the phase matching inductor 9 can be typically configured as 6. Omm, and the mounting area can be reduced. Since no ground pattern is required above and below the conductor pattern of the inductor 9, the number of substrates can be reduced and the thickness can be reduced to about 0.3 mm.

FIG. 10 is an admittance chart characteristic diagram of the reception filter 7 according to the present embodiment. The filter having the characteristic of Fig. 10 has a frequency where the value of the real part of the admittance is 1 in the pass band 20, and the imaginary part of the admittance is the same value in the pass band 20 and the stop band 21. It has a frequency of 5 and is capacitive in passband 20 and stopband 21. In other words, the reception filter 7 has an admittance real part of 1 at any frequency in the passband 20 and an imaginary admittance at any frequency in the passband 20 and any frequency in the stopband 21. The value of the part takes the same value of 0.5, and it has a capacity in the pass band 20 and the stop band 21. When a filter having such characteristics is used and a phase matching inductor 9 is further provided, the reception filter 7 has an admittance and impedance of the entire transmission / reception switch circuit in the passband 20 as shown in FIG. The stopband 21 has a much smaller admittance value and a much larger impedance value than those of the entire duplexer circuit. Also, the value of the imaginary part of the admittance at any frequency in the passband 20 and any frequency in the stopband 21 is zero.

On the other hand, FIG. 13 is an admittance chart characteristic diagram of the transmission filter 8 of the present embodiment, and FIG. 12 is an admittance chart characteristic diagram of the transmission filter 8 for comparison.

The filter having the characteristics shown in FIG. 12 has a admittance real part value of 1 at a certain frequency in the passband 20, but at any frequency in the passband 20 and any frequency in the stopband 21. The value of the imaginary part of admittance is not the same. When a filter exhibiting such characteristics is used and a phase matching inductor 9 is provided, the transmission filter 8 has the characteristics shown in FIG. In the force S where the value of the imaginary part of admittance is 0, there is no frequency in the stopband 21 where the value of the imaginary part of admittance is 0. Therefore, in this case, the phase matching is insufficient and the characteristics of the duplexer are insufficient. In the filter having the characteristics shown in FIG. 13, the real part of the admittance is 1 at a certain frequency in the passband 20, and the admittance at any frequency in the passband 20 and any frequency in the stopband 21. The value of the imaginary part is the same value of 0.5, and the passband 20 and the stopband 21 are capacitive. When a filter exhibiting such characteristics is used and a phase matching inductor 9 is further provided, the transmission filter 8 has the characteristics shown in FIG. It has admittance and impedance values that are close to the overall circuit admittance and impedance, and has a much smaller admittance value and a much larger impedance value in the stopband 21 than the entire circuit. Further, the value of the imaginary part of the admittance at any frequency in the pass band 20 and any frequency in the stop band 21 is zero.

As described above, in this embodiment, when the phase matching inductor 9 is not connected to the transmission line 10 as the reception filter 7 and the transmission filter 8, the value of the real part of the admittance in each passband 20 Is a frequency where the imaginary part of the admittance has the same value in the four bands of the pass band 20 and stop band 21 of the reception filter 7 and the pass band 20 and stop band 21 of the transmission filter 8. And have the capacities in the four bands. For this reason, the amount of phase matching in each of the reception filter 7 and the transmission filter 8 is the same. In addition, by providing a single phase matching inductor 9, even if the reception filter 7 and the transmission filter 8 are misaligned or misaligned, the passband 20 is important for the configuration of the duplexer. The admittance and impedance values are close to the admittance and impedance of the entire duplexer circuit. In the cutoff band, the admittance is much smaller and the impedance is much larger than the entire duplexer circuit. be able to. Therefore, in this case, the phase matching is sufficient and the characteristics of the duplexer are good.

Claims

The scope of the claims

[1] connected to a reception filter having a first terminal and a second terminal, a transmission filter having a third terminal and a fourth terminal, and the first terminal and the third terminal. A duplexer having a common terminal,

The reception filter and the transmission filter have a frequency at which the value of the real part of admittance is 1 in each pass band when the phase matching inductor is not connected to the transmission line, and the reception filter The imaginary part of the admittance has the same frequency in the four bands of the pass band and stop band of the transmission filter and the pass band and stop band of the transmission filter, and the four bands have the capacity. The handset switch.

[2] The inductance of the phase matching inductor is set so that the transmission filter and the reception filter are phase matched when it is connected to the transmission line. The duplexer according to claim 1.