WO2006040927A1

WO2006040927A1 - Splitter

Info

Publication number: WO2006040927A1
Application number: PCT/JP2005/017808
Authority: WO
Inventors: Ryoichi Omote
Original assignee: Murata Manufacturing Co., Ltd.
Priority date: 2004-10-08
Filing date: 2005-09-28
Publication date: 2006-04-20
Also published as: JPWO2006040927A1

Abstract

A splitter exhibiting an improved attenuation amount in a lower frequency range than the passing bands of first and second bandpass filters and further exhibiting a less insertion loss in the passing bands. A splitter (1) has a first bandpass filter (F1), which exhibits a relatively low passing band, and also has a second bandpass filter (F2), which exhibits a relatively high passing band. The splitter also has a first capacitance (CS) connected in series with and between a common terminal (3) and an antenna (2), a second capacitance (Cp) connected between a ground potential and a junction between the first capacitance (CS) and the antenna (2), and a inductance (Lp) connected between the foregoing junction and the ground potential and also connected in parallel to the second capacitance (Cp). The resonance frequency of a parallel resonance circuit constituted by the second capacitance (Cp) and inductance (Lp) is established such that it is higher than the passing band of the second bandpass filter (F2).

Description

Duplexer

Technical field

TECHNICAL FIELD [0001] The present invention relates to a duplexer used in a communication device such as a mobile phone, and more specifically, the first and second band pass filters are configured using a surface acoustic wave filter (SAW filter). This relates to the demultiplexer.

Background art

Conventionally, there has been a strong demand for downsizing and low profile in communication devices such as mobile phones. For this reason, mobile phones use a single antenna for transmission and reception. In this case, since the transmission frequency and reception frequency are different, a duplexer is connected to the antenna.

[0003] Patent Document 1 below discloses an example of a duplexer used for such a purpose. FIG. 11 is a diagram showing a circuit configuration of the duplexer described in Patent Document 1. In FIG.

[0004] As shown in FIG. 11, the duplexer 101 has an antenna terminal 102 connected to the antenna. The antenna terminal 102 has a first bandpass filter F and a second bandpass filter.

1

Is connected to F. Here, the first bandpass filter F is the transmission side band filter.

twenty one

And is connected to the transmission terminal 103. The second band pass filter F is used as a receiving side band filter and is connected to the receiving terminal 104. No

2

The center frequency of the second pass filter F is f and the center frequency f of the second band pass filter F is

1 1 2 2 Then f ≥ f.

twenty one

[0005] The bandpass filter F is in parallel with the force series arm resonator S shown schematically in FIG.

1

It is constituted by a ladder type SAW filter having a row arm resonator P. Similarly, the second bandpass filter F is also a ladder type SA having a series arm resonator S and a parallel arm resonator P.

2

It is composed of a W filter. Here, the series arm resonator S and the parallel arm resonator P are composed of SAW resonators.

[0006] In the duplexer 101, a matching circuit 105 is connected between the antenna terminal and the bandpass filter F in order to achieve matching with the antenna. Matching circuit 105 is connected to antenna terminal 102. Capacitor C inserted in series between bandpass filter F, antenna terminal 102 and capacitor C

2

And an inductance L connected between the connection point and the ground potential.

[0007] The duplexer 101 is a resonator closest to the antenna terminal 102 of the bandpass filter F.

2

When the series arm resonator S is a coupling-side resonator, the impedance of the coupling-side resonator is a capacitive high impedance at the frequency f. The coupling-side resonator

1

Is also capacitive in the passband of the bandpass filter F2, but the resonance frequency of the coupling-side resonator is close to the frequency f, so

2

The frequency f is extremely low impedance. And this capacitive impedance

2

Impedance matching is achieved by adjusting the inductance value of inductance L. Therefore, at the center frequency f, the antenna

1 1 It is easy for current to flow through the terminal 102.

2

The current easily flows through the bandpass filter F.

2

Patent Document 1: JP-A-5-167388

Disclosure of the invention

[0008] In recent years, 3GPP, which is an international standard for mobile communication devices, is required to attenuate spurious signals of various frequencies generated on the transmission side in order to avoid interference on the reception-side bandpass filter. . When the reception frequency is Rx and the transmission frequency is Tx, attenuation of spurious signals with frequencies such as Rx Tx, 2Τχ—Rx, and Rx + Tx is required. There is a strong demand for it.

By the way, in the W-CDMA system in Japan, for example, the reception side passband is 2110 to 217 OMHz, and the transmission side passband is 1920 to 1980 MHz. Therefore, Rx-Tx is 19 OMHz, which is a frequency much lower than the frequency of the transmission side passband. That is, Rx — Tx is a frequency that is orders of magnitude lower than the passband frequency! /.

[0010] When the duplexer 101 described in Patent Document 1 is used, a low-frequency signal such as Rx—Tx is sufficiently reduced in the second bandpass filter F that is a reception-side bandpass filter.

2

It was difficult to fade.

The object of the present invention is considerably higher than the passbands of the respective bandpass filters of the duplexer having the first and second bandpass filters having different passbands in view of the current state of the prior art described above. A duplexer is provided in which the attenuation at a low frequency can be made sufficiently large on the side of the second bandpass filter having a relatively high passband, and the force is not easily deteriorated in the insertion loss in the passband. There is.

[0012] According to the first invention of the present application, the first bandpass filter having a relatively low passband frequency and the second bandpass filter having a relatively high passband frequency are provided. 1. A duplexer in which one end of a second bandpass filter is connected to a common terminal on the antenna side, a first capacitor connected in series between the common terminal and the antenna, the antenna and the antenna A matching circuit having a second capacitor connected between a connection point between the first capacitor and the ground potential, and a first inductance connected in parallel to the second capacitor; A duplexer is provided, wherein a resonance frequency of a parallel resonance circuit of the second capacitor and the first inductance is higher than a pass band of the second band-pass filter. Is done.

[0013] According to the second invention of the present application, the first bandpass filter having a relatively low passband frequency and the second bandpass filter having a relatively high passband frequency are provided. 1, in a duplexer in which one end of the second bandpass filter is connected to a common terminal on the antenna side, and is connected between a connection point between the antenna and the common terminal and a ground potential A matching circuit having a capacitor and a first inductance connected in parallel to the capacitor, wherein a resonance frequency by a parallel resonance circuit of the capacitor and the first inductance is the second band; A duplexer is provided which is characterized by being higher than the pass band of the pass filter.

[0014] In a specific aspect of the present invention (first and second inventions), the second band-pass filter includes a coupling-side resonator connected in series on the common terminal side.

[0015] Further, in another specific aspect of the present invention, there is provided a ladder-type SAW filter in which the second band-pass filter force has a plurality of SAW resonators connected so as to have a ladder-type circuit configuration.

[0016] In another specific aspect of the present invention, a second inductance is further provided, and the ladder-type SAW filter constitutes a ladder-type circuit, and among the plurality of SAW resonators, The at least one series arm resonator disposed on the series arm has the second inductance Are connected in parallel.

[0017] In another specific aspect of the duplexer of the present invention, the second bandpass filter is a longitudinally coupled resonator type SAW filter.

[0018] In still another specific aspect of the duplexer according to the present invention, the duplexer further includes a packaging material on which the first and second bandpass filters are mounted, and the capacitance and the inductance are each provided. The matching circuit is configured by a chip-type capacitor and a chip-type inductance element and connected outside the package material.

[0019] In still another specific aspect of the duplexer according to the present invention, the first and second bandpass filters are mounted, further comprising a knocking material, and one of the capacitance and the inductance. The above is constituted by using an electrode pattern in the package material.

[0020] In still another specific aspect of the duplexer according to the present invention, the duplexer further includes a filter substrate on which the first and Z or second bandpass filters are configured, and the capacitance and the inductance are controlled. One or more of them are formed on the filter substrate.

In the duplexer according to the first invention, the matching circuit includes the first capacitor and a second capacitor and an inductance connected in parallel to each other, and the second capacitor and the inductance Since the resonant frequency of the parallel resonant circuit is higher than the passband of the second bandpass filter, the impedance of the parallel resonant circuit is induced in the passband of the first and second bandpass filters. Therefore, the inductance is equivalent to the inductance L in the prior art described above. On the other hand, since the second capacitor is connected in a frequency range much lower than the passband of the first bandpass filter, such as 190 MHz, the inductance value of the above inductance can be reduced. Therefore, a large attenuation can be obtained. As will be described later, in the attenuation frequency characteristic by the parallel resonant circuit, the inductance value of the inductance, / J, where the capacitance of the second capacitor is large, the larger the attenuation, the greater the amount of attenuation. It depends on what you can do.

[0022] Therefore, according to the first invention, the frequency of the second bandpass filter is lower than the passband of the first bandpass filter, particularly at least one digit lower than the passband. The amount can be increased.

Therefore, by adjusting the circuit constant of the matching circuit, for example, 190 MHz It is possible to make the attenuation in the frequency range on the order of one or more orders of magnitude smaller than the passband of the first bandpass filter sufficiently large. However, according to the present invention, the insertion loss is hardly deteriorated in the pass band!

In the duplexer according to the second invention, the matching circuit includes the inductance and the capacitance, and the resonance frequency of the parallel resonance circuit of the capacitance and the inductance is the passband of the second bandpass filter. Therefore, in the passbands of the first and second bandpass filters, the impedance by the parallel resonant circuit is inductive, and is equivalent to the inductance L in the prior art described above. On the other hand, in the frequency range much lower than the pass band of the first band pass filter, such as 190 MHz, the capacitance is connected, so that the inductance value of the inductance can be reduced, thereby increasing the capacitance. Attenuation can be obtained. This is because, as will be described later, in the attenuation frequency characteristics of the parallel resonance circuit, the larger the capacitance value of the capacitance and the smaller the inductance value of the inductance, the larger the attenuation amount can be obtained.

Therefore, according to the second invention, the frequency of the second bandpass filter in the frequency region is lower than the passband of the first bandpass filter, and in particular the frequency is one digit or more lower than the passband. The amount of attenuation can be increased.

[0026] In the present invention, when the second band-pass filter force has a coupling-side resonator connected in series on the common terminal side, the first band-pass filter The impedance of the second band-pass filter in the pass band can be a large capacitive impedance. Therefore, the insertion loss of the first bandpass filter can be reduced.

[0027] When the first and second bandpass filters are ladder-type SAW filters in which a plurality of SAW resonators are connected so as to have a ladder-type circuit configuration, they are lower than the passband. Since it is difficult to secure an attenuation amount of a certain frequency, the attenuation amount in a frequency region that is much lower than the pass band can be surely made sufficiently large by using the present invention in particular.

[0028] In the present invention, a second inductance is further provided, and at least one SAW arranged in a series arm among the plurality of SAW resonators of the ladder-type SAW filter. When the second inductance is connected in parallel to the resonator, it is possible to increase the isolation of the duplexer compared to the case where the inductance is not connected in parallel to the series arm resonator. Become.

When the second bandpass filter is a longitudinally coupled resonator type SAW filter, the attenuation in the frequency range an order of magnitude lower than the passband of the second bandpass filter is wide, and the bandwidth is sufficiently large. It can be.

[0029] A package material on which the first and second band-pass filters are mounted is further provided, and the capacitance and the inductance are configured by a chip capacitor and a chip inductor, respectively. When a matching circuit is configured by connecting components outside the package material, the inductance value and capacitance of these chip-type electronic components can be easily changed according to the passband and application. . Therefore, it is possible to easily change the circuit constant of the matching circuit, thereby reliably improving the attenuation in a frequency region lower than the passband.

[0030] When one or more of the capacitance and the inductance are configured using an electrode pattern in the package material, the duplexer including the matching circuit can be reduced in size.

[0031] When one or more of the capacitance and the inductance are formed on the filter substrate on which the first and / or second bandpass filter is configured, the duplexer is further increased. Miniaturization can be achieved.

Brief Description of Drawings

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

[Fig. 2] Fig. 2 shows the attenuation frequency characteristics on the transmission side of the duplexer of the embodiment shown in Fig. 1, and the attenuation frequency characteristics on the transmission side of the conventional duplexer prepared for comparison. FIG.

[FIG. 3] FIG. 3 shows the frequency characteristics on the receiving side of the duplexer of the embodiment shown in FIG. 1 and the frequency characteristics on the receiving side of the conventional duplexer prepared for comparison. FIG.

[FIG. 4] FIG. 4 shows the attenuation frequency characteristics of the passband of the duplexer of the embodiment shown in FIG. It is a figure which shows the attenuation frequency characteristic of the pass band of the conventional duplexer prepared for the comparison.

FIG. 5 is a diagram showing attenuation frequency characteristics of a parallel resonance circuit of a second capacitor Cp and an inductance L in the first embodiment.

FIG. 6 is a circuit diagram showing a modification of the duplexer of the present invention.

FIG. 7 is a circuit diagram showing another modification of the duplexer of the present invention.

FIG. 8 is a diagram showing a circuit configuration of a conventional duplexer prepared for comparison with the embodiment shown in FIG. 1.

[FIG. 9] FIGS. 9 (a), (b) and (c) are a front view, a front sectional view and a plan view showing a modification of the specific structure of the duplexer of the present invention.

FIG. 10 is a schematic plan view for explaining still another structural example of the duplexer of the present invention.

FIG. 11 is a circuit diagram showing an example of a conventional duplexer.

Explanation of symbols

1 ... Branch

2 ... Antenna

3 Common terminal

4 ... Transmission terminal

5 ... Receiving terminal

6, 7… Connection point

8 ... Matching circuit

20 ... Branch

21 to SAW resonator

22… Resonator type SAW filter

31 ...

32 ... Packaging material

33… Chip type capacitor

34… Chip type capacitor 35… Chip type inductor

35 Α Inductor

41 ··· Branch

42 ... Packaging material

42a… Package inner layer

51… Finoleta substrate

52 ··· Conductor coil

53 ··· Conductor coil

54 ... Comb electrode

Cs… capacity (first capacity)

Cp ... capacity (second capacity)

F ... 1st bandpass filter

1

F ... Second bandpass filter

2

Lp ... Inductance

BEST MODE FOR CARRYING OUT THE INVENTION

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

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

The duplexer 1 of the present embodiment has a common terminal 3 connected to the antenna 2. One end of the first bandpass filter F is electrically connected to the common terminal 3. Also, common terminal

1

3 is also connected to one end of a second bandpass filter F having a relatively high passband.

2

The

The duplexer 1 of this embodiment is used as a duplexer for a W-CDMA mobile phone. The first bandpass filter F is a transmitting bandpass filter, and its passband

1

The range is 1920-1980MHz. On the other hand, the second bandpass filter F is a band on the receiving side.

2

It is a pass filter, and its passband is 2110-2170MHz.

[0038] The end of the first bandpass filter F opposite to the side connected to the common terminal 3 is

1

Connected to transmit terminal 4. The first bandpass filter F includes a plurality of series arm resonators. This is a ladder type SAW filter having Sla, Sib, S2a, S2b, S3 and parallel lj arm resonators PI, P2. Here, the series arm resonators Sla to S3 are arranged in order from the common terminal 3 to the transmission terminal 4. The parallel arm resonator P1 is connected between the connection point between the series arm resonator Sib and the series arm resonator S2a and the ground potential. In the parallel arm, the parallel arm resonator P1 is connected to the parallel arm resonator P1. An inductance L is connected to P1 directly to U!

1

[0039] The parallel arm resonator P2 is connected in series between the connection point between the series arm resonator S2b and the series arm resonator S3 and the ground potential. In this parallel arm, an inductance L is connected in series with the parallel arm resonator P2.

2

[0040] The series arm resonators Sla to S3 and the parallel arm resonators PI and P2 are composed of SAW resonators, and are configured as shown in Table 1 below in this embodiment.

[0041] [Table 1]

[0042] On the other hand, connected to the common terminal 3 of the second bandpass filter F, the end on the opposite side to the opposite side

2

Is connected to the receiving terminal 5, but in the second bandpass filter F, the common terminal 3 side

2

The series arm resonators S4a, S4b, S5, and S6 are connected in series toward the force receiving terminal 5. The parallel arm resonator P3 is connected between the connection point 6 between the series arm resonator S4b and the series arm resonator S5 and the ground potential. A parallel arm resonator P4 is connected between a connection point 7 between the series arm resonator S5 and the series arm resonator S6 and the ground potential. In addition, an inductance L is connected between the connection points 6 and 7 in parallel with the series arm resonator S5.

Three

[0043] The series arm resonators S4a to S6 and the parallel arm constituting the second bandpass filter F

2

Each of the pendulums P3 and P4 is composed of a SAW resonator. That is, the second bandpass filter F is also a ladder type SAW filter. Each resonator S4a ~ S6 and P3, P4

2

Is designed as shown in Table 2 below. [0044] [Table 2]

Note that in the second bandpass filter F, the series arm resonator 2 on the common terminal 3 side 2

2

The reason why the wavelength λ ί of each of the series arm resonators S4a and S4b is made smaller than the wavelength λ of the other series arm resonators S5 and S6 is to increase the bandwidth.

[0046] In the present specification, the second bandpass filter F constitutes a plurality of resonators! /

2

Of these, the resonator closest to the common terminal 3 will be appropriately abbreviated as a coupled resonator in the following. In the present embodiment, the series arm resonator S4a is a coupling side resonator.

Further, a matching circuit 8 is connected between the antenna 2 and the common terminal 3. The matching circuit 8 is connected between the first capacitor Cs connected in series between the antenna 2 and the common terminal 3, and the connection point between the first capacitor C s and the antenna 2 and the ground potential. The second capacitance Cp, and the inductance connected between the connection point between the antenna 2 and the first capacitance Cs and the ground potential, and connected in parallel with the second capacitance Cp. Lp. That is, the second capacitor Cp and the inductance Lp are connected so as to resonate in parallel. In this embodiment, the resonance frequency of this parallel resonance is set higher than the passband of the second bandpass filter F.

2

It is characterized by.

[0048] Since the matching circuit 8 is configured as described above, it passes through the first bandpass filter F.

Attenuation in the frequency range an order of magnitude lower than 1 band can be greatly increased, especially in the vicinity of 190 MHz. In this way the bandpass filter F passes

The reason why the attenuation in the frequency range one digit lower than one band can be expanded is considered to be as follows.

That is, in the passbands of the first and second bandpass filters F 1 and F 2,

1 2

The impedance of the parallel resonant circuit of the capacitance Cp and the inductance Lp is an inductive force. This is an equivalent of the inductance L in the prior art described in Patent Document 1 described above. Dactance. On the other hand, the passband of the first bandpass filter F, such as 190MHz

1

In the frequency range that is more than an order of magnitude lower, the inductance value of the inductance Lp can be reduced by adding the second capacitor Cp. As a result, the attenuation in the vicinity of 190 MHz can be increased. The insertion force and the insertion loss in the pass band are hardly reduced. This will be specifically described with reference to FIGS.

[0050] First, in fabricating the above duplexer, on a LiNbO substrate with 55 ° rotation Y-cut X-propagation

Third, after forming a 10 nm-thick Ti base electrode layer, a 94-nm thick A1 electrode layer was formed, and the first and second band-pass filters F 1 and F 2 were formed by turning. this

1 2

Thus, a filter substrate was obtained. Then, this filter substrate was mounted on a package material having a ceramic force, and an electrode pad provided on the package material and an electrode node on the filter substrate were joined by a bonding wire.

[0051] It should be noted that the inductances L, L and the second band pass in the first band pass filter F are shown.

1 1 2

For the inductance L in the filter F, the coil pattern in the package material

twenty three

The inductance values were as follows.

[0052] Inductance L = 3.3 nH, Inductance L = 3.3 nH, and Inductance L = 2.

one two Three

5nH.

[0053] On the other hand, in order to form the matching circuit 8 on the mounting board outside the knocking material, the first and second chip capacitors constituting the first capacitor Cs, the second capacitor Cp, and the inductance Lp are provided. And a chip type inductor was mounted and electrically connected. In this case, the capacitance value of the first capacitor Cs was 7. OpF, the capacitance of the second capacitor Cp was 1.4 pF, and the inductance value of the inductance Lp was 2.2 nH.

For comparison, as shown in FIG. 8, it is configured in the same manner as in the above embodiment except that it has a matching circuit 111 consisting only of a series capacitor Cs and an inductance Lp. A duplexer 112 was prepared as a conventional duplexer. Note that the capacitance value of the series capacitor Cs and the inductance value of the inductance Lp in the duplexer 112 of this conventional example were 10. OpF and the inductance Lp were 5. OnH.

[0055] Fig. 2 shows the attenuation-frequency characteristics of the transmission side of the duplexers of the embodiment and the conventional example prepared as described above, and Fig. 3 shows the attenuation-frequency characteristics of the reception side. Attenuation amount Figure 4 shows the frequency characteristics. In FIGS. 2 to 4, the solid line shows the result of the example, and the broken line shows the result of the conventional example. In Fig. 4, the expanded frequency response is the characteristic expanded by the starboard j scale.

As is clear from FIG. 3, according to the present embodiment, compared with the conventional example, it is 190 MHz, that is, on the low band side, which is an order of magnitude lower than the pass band of the first bandpass filter F. frequency

1

The attenuation in the band has been greatly expanded. In other words, the attenuation at 190 MHz corresponding to the frequency of Rx-Tx is increased to 61.6 dB in this example compared to 53.8 dB in the conventional example, and thus the attenuation at 190 MHz is 7.8 dB. Improved.

As is apparent from FIG. 4, the insertion loss degradation amount of the passband compared to the conventional example is 0.13 dB on the transmitting side and 0.07 dB on the receiving side, both of which are very small. . In other words, in this embodiment, the insertion loss in the passband on the transmission side stays at 1.29 dB, and the insertion loss on the reception side also stays at 2. OldB.

[0058] As described above, in the present embodiment, the passband of the first bandpass filter F is larger than that of the first bandpass filter F.

1

The reason why the attenuation can be improved in a much lower frequency range is that the attenuation by the parallel resonance circuit of the second capacitor Cp and the inductance Lp is large in the frequency range. This will be described with reference to FIG. FIG. 5 is a diagram showing the attenuation frequency characteristics of the parallel resonant circuit when the values of the capacitance of the second capacitor Cp and the inductance Lp are changed. Figure 5 shows the characteristics of a parallel resonant circuit with the following three combinations.

[0059] l) Cp = 2.8 pF and Lp = l. InH

2) Cp = l .4pF and Lp = 2.2nH

3) Cp = 0.7pF and Lp = 4.4nH

As is apparent from FIG. 5, it can be understood that the attenuation value at 190 MHz increases as the inductance value of the inductance Lp, which increases the capacitance of the second capacitor Cp, decreases. In this embodiment, since the resonant frequency of the parallel resonant circuit is set higher than the passbands of the first and second bandpass filters F, F,

1 2

The impedance of the column resonant circuit is inductive, and is equivalent to the inductance L of the prior art. Therefore, decrease the inductance Lp and increase the second capacitance Cp. As a result, the attenuation in a low frequency range such as 190 MHz can be expanded and impedance matching can be improved, so that the insertion loss is hardly degraded.

[0061] In the passbands of the first and second bandpass filters F 1 and F, the first inductance Lp and

1 2

The parallel circuit of the second capacitor Cp is equivalent to the inductance Lpl, whose inductance value is larger than the inductance Lp. Therefore, it can be considered that a matching circuit composed of the inductance Lpl and the first capacitor is connected between the antenna 2 and the common terminal 3. The first and second bandpass filters F and F and the antenna are impedance matched.

1 2

In addition, since the inductance value of the first inductance Lp 1 and the capacitance value of the first capacitor are determined, there is almost no deterioration in insertion loss.

[0062] In the pass band, the inductance value of the first inductance Lp and the capacitance value of the second capacitor Cp that can be made equal to the inductance Lpl can be set as appropriate.

[0063] Note that the upper limit of the resonance frequency by the parallel resonance circuit of the first inductance Lp and the second capacitor Cp is appropriately determined according to the allowable range of the insertion loss deterioration amount in the passband.

Therefore, according to the present invention, it is possible to provide a duplexer that can easily satisfy the filter characteristics required by the 3GPP standard and can greatly improve the communication quality of the communication device. I ’ll be able to speak

In the duplexer 1 of the embodiment shown in FIG. 1, the first capacitor Cs is connected in series to the antenna 2, but in the present invention, the first capacitor Cs is not connected. Also good. Figure 6 shows the circuit configuration of such a modification. In the duplexer 1A shown in FIG. 6, as described above, the duplexer 1 of the first embodiment is the same as the duplexer 1 except that the capacitor Cs connected in series to the antenna terminal 2 is not connected. It is constituted similarly. In this case, the capacitance value of the capacitance Cp is 1.4 P F, and the inductance value of the inductance Lp is 2.4 nH! Even in this case, the parallel resonance of the inductance Lp and the capacitance Cp connected in parallel to the inductance Lp is used, as in the case of the first embodiment.

1 Attenuation at a frequency lower than the passband, especially in the vicinity of 190 MHz, which is a frequency that is an order of magnitude or more lower, can be made sufficiently large. In the above embodiment, the first bandpass filter F and the second bandpass filter

1

Each F is composed of a ladder type filter that connects multiple SAW resonators.

2

However, in the present invention, the first and second band pass filters may be configured by a filter other than the ladder-type SAW filter. For example, as shown in the circuit diagram of FIG. 7, the first band-pass filter F force is composed of a ladder-type SAW filter as in the first embodiment.

1

The second bandpass filter F is configured with a resonator-type SAW filter.

2

May be. In this duplexer 20, the SAW resonator 21 and the resonator type SAW filter 22 are connected to the common terminal 3 in this order, and are connected to the SAW resonator 21 of the resonator type SAW filter 22. The end opposite to the side is connected to the receiving terminal 5.

[0067] Thus, the second bandpass filter F is configured using a resonator-type SAW filter.

2

May be. In FIG. 7, the coupling-side resonator is the SAW resonator 21, and the resonance frequency of the SAW resonator 21 is set within the pass band of the second bandpass filter F.

2

Therefore, in the passband of the bandpass filter F, the bandpass filter

2

In the pass band of the bandpass filter F, the SAW resonator 21

twenty one

Using a capacitive high impedance, current is passed through the antenna 2 from the bandpass filter F

1

It can be made easy.

[0068] The resonance frequency of the SAW resonator 21 is higher than the center frequency of the second bandpass filter F.

2

Increase the bandwidth of the second bandpass filter F, which is preferable to set

2

be able to.

[0069] Also in the duplexer 20 shown in FIG. 7, the matching circuit 8 is configured in the same manner as the matching circuit 8 of the first embodiment, and therefore, the first band as in the first embodiment. Pass filter F

Attenuation in a frequency range much lower than 1 can be greatly improved, and deterioration of insertion loss hardly occurs.

[0070] When configuring the duplexer according to the present invention, the filter substrates constituting the first and second band-pass filters and the first and second band-pass filters are mounted on or housed. Appropriate structures can be used for the electronic component elements constituting the package material and the matching circuit.

For example, in the duplexer 31 shown in FIG. 9A, the package material mounted on the mounting substrate 36 The filter substrate on which the first and second band pass filters are configured is housed in 32, and a chip is formed to form the matching circuit 8 on the mounting substrate 36 outside the package material 32. Capacitors 33 and 34 and a chip inductor 35 are mounted. The chip capacitor 33 forms a first capacitor Cs, the chip capacitor 34 forms a second capacitor Cp, and the chip inductor 35 forms an inductance Lp. As described above, each chip-type electronic component constituting the first capacitor Cs, the second capacitor Cp, and the inductance Lp may be mounted on the mounting substrate 36 outside the package material.

[0072] Further, as shown in FIGS. 9 (b) and 9 (c), the filter substrate on which the first and second band-pass filters are configured is housed in the knock member 42, and further, The inductor 35A constituting the matching circuit may be configured using an electrode pattern on the inner layer 42a inside the package 42. In this duplexer, chip capacitors 33 and 34 constituting a matching circuit are mounted on the mounting board 36 outside the package 42.

[0073] The mounting board 36 in Figs. 9 (a), (b), and (c) may be a duplexer module board or an RF board of a mobile phone.

In the modification shown in FIG. 10, first and second band pass filters F 1 and F 2 are configured in a region B indicated by a one-dot chain line on the filter substrate 51. And the same filter

1 2

On the upper surface of the substrate 51, a comb electrode 52 for forming the first capacitor Cs, a conductor coil 53 for forming the inductance Lp, and a comb electrode 54 for forming the second capacitor Cp are formed. Thereby, the matching circuit 8 is also formed on the filter substrate 51.

That is, in the circuit configurations shown in FIG. 1, FIG. 6 and FIG. 7, the first and second band-pass filter portions surrounded by the broken line A are configured on the filter substrate, and the matching circuit 8 is configured. Each electronic component element may be composed of an electronic component element different from the filter substrate, or an electronic component element itself constituting a matching circuit may be formed on the filter substrate. Further, in FIG. 10, the force in which the first and second band pass filters F, F are configured in the portion surrounded by the alternate long and short dash line B on the filter substrate 51.

1 2

The first and second band pass filters may be formed of different filter substrates. Each electronic component element constituting the matching circuit 8 may be formed on a V-deviation filter substrate. That is, the filter in which the first and / or second bandpass filter is configured. A capacitor and an inductance can be formed all over the data substrate.

In the above embodiment, as the piezoelectric substrate constituting the filter substrate, another piezoelectric single crystal substrate using a 55 ° rotated Y plate X propagation LiNbO substrate may be used. Also electrode

Three

In addition, the present invention is not limited to the one in which the A1 electrode layer is laminated on the Ti base electrode layer, and a Cu electrode layer may be used instead of the A1 electrode layer, or the base electrode layer may not be formed.

Claims

The scope of the claims

[1] a first bandpass filter having a relatively low passband frequency;

A second bandpass filter having a relatively high passband frequency, and one end of each of the first and second bandpass filters is connected to a common terminal on the antenna side and connected to a duplexer.

A first capacitor connected in series between the common terminal and the antenna;

A first point connected between a connection point between the antenna and the first capacitor and a ground potential.

A matching circuit having a capacitance of 2 and a first inductance connected in parallel to the second capacitance;

A duplexer characterized in that a resonance frequency due to parallel resonance between the second capacitor and the first inductance is higher than a pass band of the second bandpass filter.

[2] a first bandpass filter having a relatively low passband frequency;

A matching circuit having a capacitor connected between a connection point between the antenna and the common terminal and a ground potential, and a first inductance connected in parallel to the capacitor; A duplexer, wherein a resonance frequency due to parallel resonance of a capacitor and the first inductance is higher than a pass band of the second bandpass filter.

[3] The demultiplexing according to claim 1 or 2, wherein the second band-pass filter force has a coupling-side resonator connected to the common terminal side in series. vessel.

[4] The ladder-type SAW filter according to any one of claims 1 to 3, wherein the second band-pass filter is a ladder-type SAW filter formed by connecting a plurality of SAW resonators so as to have a ladder-type circuit configuration. Duplexer.

[5] It further includes a second inductance, and is arranged in a series arm of a ladder circuit among the plurality of SAW resonators constituting the ladder-type SAW filter! 5. The duplexer according to claim 4, wherein the second inductance is connected in parallel to a row arm SAW resonator.

6. The duplexer according to claim 1, wherein the second bandpass filter is a longitudinally coupled resonator type SAW filter.

[7] The apparatus further includes a packaging material on which the first and second band pass filters are mounted, and the capacitance and the first inductance are respectively configured by a chip capacitor and a chip inductance element, The duplexer according to any one of claims 1 to 6, wherein the matching circuit is configured by being connected outside the package material.

[8] It further includes a package material on which the first and second bandpass filters are mounted, and at least one of the capacitance and the first inductance uses an electrode pattern in the package material. The duplexer according to any one of claims 1 to 6, wherein the duplexer is configured.

[9] The first and / or second band pass filter is configured to further include a filter substrate, and one or more of the capacitor and the first inductance are formed on the filter substrate. The duplexer according to any one of claims 1 to 6.