JP2010192974A - Branching filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a branching filter for reducing deterioration in isolation characteristics even if the branching filter is miniaturized, and especially for reducing deterioration in the isolation characteristics in a transmission signal band. <P>SOLUTION: A first filter 2 has: a first series section configured by connecting first series resonators S11 to S1n in series; a first parallel section configured by connecting respective first parallel resonators P11 to P1n to the first series section in parallel with each other; and first inductors L11 to L1n connected between the first parallel resonators and ground. A second filter 3 has: a second series section configured by connecting second series resonators S21 to S2m in series; a second parallel section configured by connecting respective second parallel resonators P21 to P2n to the second series section in parallel with each other; and second inductors L21 to L2m respectively connected between the second parallel resonators and ground. A capacitive coupling 7 is formed between the first inductor L12 and the second inductor L22. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a duplexer that is used in a communication device and includes a transmission filter and a reception filter.

  In recent years, in mobile communication devices, the demand for miniaturization and higher frequencies associated with higher functionality have been increasing. From such a background, a surface acoustic wave filter and a thin film piezoelectric filter, which can reduce the outer size as compared with conventional dielectric filters and ceramic filters, are often used in high frequency communication filters.

  Surface acoustic wave filters and thin film piezoelectric filters can be configured as ladder filters to change the number of filter stages and resonator capacity, and to install an extension inductor between the parallel resonator and the ground. The insertion loss and attenuation characteristics of the filter can be easily changed.

  As an application part using the surface acoustic wave filter or the thin film piezoelectric filter, there is a duplexer capable of dividing a transmission / reception signal according to frequency.

  The duplexer passes a signal with low loss in the pass band of one of the transmission filter and the reception filter, does not input the signal to the other filter, and increases the pass band signal of the other filter. There is a need for a duplexer that attenuates and increases the amount of isolation between the input terminal pair and the output terminal pair of the two filters. In particular, transmission signals with a large signal level are strongly required to suppress leakage to the reception terminal, and improvement of isolation characteristics in the frequency band of the transmission signals is important.

  For example, in the technique described in Patent Document 1, two ladder filters having different passbands are configured using a plurality of thin film piezoelectric resonators, and one of the input / output terminals of these ladder filters is a common terminal. In addition, a duplexer is configured by inserting a phase shifter between the ladder-type filter and the common terminal, and an extension inductor is connected to the parallel resonator. Furthermore, in the technique described in Patent Document 2, two ladder filters having different pass bands are configured using a plurality of surface acoustic wave resonators, and one of the input / output terminals of these ladder filters is shared. A duplexer is configured by connecting to a terminal and further connecting a matching inductor to a common terminal.

  On the other hand, with miniaturization and high functionality of mobile communication devices, very small duplexers are required. However, when the duplexer is downsized, the distance between the antenna terminal and the input / output terminal pair of the two filters is shortened, the attenuation in the passband of the other filter is reduced, and the input terminals of the two filters are As the distance to the output terminal is shortened, the aforementioned isolation amount is reduced.

  Therefore, for example, in the technique described in Patent Document 3 relating to a duplexer using a thin film piezoelectric resonator, a ladder-type filter is configured, and a pattern arrangement of extended inductors connected between the parallel resonator and the ground is used. By taking this into account, the amount of isolation is increased.

JP 2001-24476 A JP 10-313229 A JP 2007-259296 A

  In recent years, the demand for downsizing of mobile communication devices has become more severe, and further downsizing of duplexers is desired. However, with miniaturization, the components used in the matching circuit or phase shifter that make up the duplexer, and the elements such as the extension inductor that make up the ladder filter are closer together. In this case, in the techniques described in Patent Documents 1 and 2, signal crosstalk occurs, resulting in a decrease in attenuation in the stop band and deterioration in isolation characteristics. In addition, as disclosed in Patent Document 3, when considering the pattern arrangement of the elongated inductor constituting the ladder filter, the design freedom of the duplexer is reduced and the size is reduced. It was a disadvantage.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a duplexer with little deterioration in isolation characteristics, particularly in a transmission signal band, even when downsized. There is to do.

According to one aspect of the invention,
An antenna terminal, a first terminal, a second terminal, a first filter connected between the antenna terminal and the first terminal, and a first filter connected between the antenna terminal and the second terminal A duplexer comprising a second filter having a higher pass frequency than
The first filter is connected between the antenna terminal and the first terminal and includes a first series unit formed by connecting a plurality of first series resonators in series, and a plurality of first parallel resonators. And a plurality of first inductors connected between the plurality of first parallel resonators and the ground, respectively.
The second filter is connected between the antenna terminal and the second terminal and includes a second series unit formed by connecting a plurality of second series resonators in series, and a plurality of second parallel resonators. And a plurality of second inductors respectively connected between the plurality of second parallel resonators and the ground;
Capacitive coupling is formed between a specific first inductor that is any one of the plurality of first inductors and a specific second inductor that is any one of the plurality of second inductors. Has been
The specific first inductor is connected to the first parallel resonator connected to the first series part at a position where the proximity of the path to the antenna terminal is any one after the second,
The specific second inductor is connected to the second parallel resonator connected to the second series unit at a position where the path to the antenna terminal is any second or later. A duplexer,
Is provided.

  According to this, it is possible to provide a duplexer with excellent isolation characteristics even when it is downsized.

  In the above configuration, preferably, the capacitive coupling is formed by a capacitor, one electrode of the capacitor is connected to the specific first inductor, and the other electrode of the capacitor is connected to the specific second inductor. It is connected. According to this, it is possible to provide a duplexer with excellent isolation characteristics without increasing the size.

According to another aspect of the invention,
An antenna terminal, a first terminal, a second terminal, a first filter connected between the antenna terminal and the first terminal, and a first filter connected between the antenna terminal and the second terminal A duplexer comprising a second filter having a higher pass frequency than
The first filter is connected between the antenna terminal and the first terminal and includes a first series unit formed by connecting a plurality of first series resonators in series, and a plurality of first parallel resonators. And a plurality of first inductors connected between the plurality of first parallel resonators and the ground, respectively.
The second filter is connected between the antenna terminal and the second terminal and includes a second series unit formed by connecting a plurality of second series resonators in series, and a plurality of second parallel resonators. And a plurality of second inductors respectively connected between the plurality of second parallel resonators and the ground;
The specific first inductor, which is any one of the plurality of first inductors, and the specific second inductor, which is any one of the plurality of second inductors, form inductive coupling. And
The specific first inductor is connected to the first parallel resonator connected to the first series part at a position where the proximity of the path to the antenna terminal is any one after the second,
The specific second inductor is connected to the second parallel resonator connected to the second series unit at a position where the path to the antenna terminal is any second or later. A duplexer,
Is provided.

  According to this, it is possible to provide a duplexer with excellent isolation characteristics even when it is downsized.

  In the above configuration, preferably, the inductive coupling is formed so that current directions are opposite between the specific first inductor and the specific second inductor. According to this, it is possible to reduce the mutual inductance between the specific first inductor and the specific second inductor, and it is possible to provide a duplexer with excellent isolation characteristics.

  In the above configuration, preferably, at least one of the first filter and the second filter is a ladder filter. According to this, the attenuation characteristic in the vicinity of the pass band can be increased.

  In the above configuration, the duplexer preferably further includes a third inductor connected between the antenna terminal, the connection between the first filter and the second filter, and the ground. According to this, since the duplexer can be configured without using a matching circuit composed of a plurality of elements or a phase shifter having a long line length, a smaller duplexer can be realized.

  In the above configuration, preferably, the first series part, the first parallel part, the second series part, and the second parallel part are formed on a chip, and the chip is mounted on a substrate, The first inductors and the plurality of second inductors are constituted by line patterns formed on the substrate. According to this, further miniaturization can be realized by incorporating the inductor element in the substrate.

  In the above configuration, preferably, the distance between the specific first inductor and the specific second inductor is smaller than the distance between any combination of the plurality of first inductors and the plurality of second inductors. . According to this, capacitive coupling or inductive coupling can be formed without adding new elements other than the first inductor and the second inductor, or without adding new elements, A smaller duplexer can be realized.

  In the above configuration, preferably, the first series resonator, the first parallel resonator, the second series resonator, and the second parallel resonator are surface acoustic wave resonators or thin film piezoelectric resonators. According to this, a much smaller duplexer can be realized.

  According to the present invention, there is provided a duplexer that is excellent in attenuation characteristics in the pass band of the other filter in one of the transmission filter and the reception filter even when downsized, and in which the isolation characteristics are not easily deteriorated. be able to.

It is a circuit diagram which shows embodiment of the splitter of this invention. It is a circuit diagram which shows embodiment of the splitter of this invention. It is a longitudinal cross-sectional view of a thin film piezoelectric resonator. It is a top view of a surface acoustic wave resonator. It is a longitudinal cross-sectional view which shows the structure of embodiment of the splitter of this invention. FIG. 3 is a circuit diagram of the duplexer according to the first embodiment. FIG. 3 is a configuration diagram of a multilayer substrate in the duplexer according to the first embodiment. FIG. 6 is a diagram showing pass characteristics in the duplexers of Example 1 and Comparative Example 1. 6 is a diagram showing isolation characteristics in the duplexers of Example 1 and Comparative Example 1. FIG. FIG. 6 is a circuit diagram of a duplexer according to a fifth embodiment. FIG. 6 is a configuration diagram of a multilayer substrate in a duplexer according to a fifth embodiment. It is a figure which shows the passage characteristic in the duplexer of Example 5 and Comparative Example 1. It is a figure which shows the isolation characteristic in the splitter of Example 5 and the comparative example 1. FIG. 6 is a circuit diagram of a duplexer in Comparative Example 1. FIG. 6 is a circuit diagram of a duplexer in Comparative Example 2. FIG. It is a figure which shows the passage characteristic in the duplexer of the comparative example 2 and the comparative example 1. It is a figure which shows the isolation characteristic in the duplexer of the comparative example 2 and the comparative example 1. 10 is a circuit diagram of a duplexer in Comparative Example 3. FIG. It is a figure which shows the passage characteristic in the duplexer of the comparative example 3 and the comparative example 1. It is a figure which shows the isolation characteristic in the duplexer of the comparative example 3 and the comparative example 1.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a circuit diagram showing an embodiment of the duplexer of the present invention. The duplexer of this embodiment is connected between the antenna terminal (ANT) 1, the first terminal (transmitter connection terminal) TX, the second terminal (receiver connection terminal) RX, and between the antenna terminal and the first terminal. A first filter (transmission filter) 2, a second filter (reception filter) 3 connected between the antenna terminal and the second terminal and having a higher pass frequency than the first filter, and an antenna terminal and the first filter A third inductor 6 is connected between the connection part of the second filter and the ground and functions as a matching circuit or a phase shifter.

  The first filter 2 is a ladder-type filter, and is composed of n (where n is an integer of 2 or more) first series resonators S11 including piezoelectric resonators such as surface acoustic wave resonators and thin film piezoelectric resonators. S1... S1n and n first parallel resonators P11, P12,. The first series resonators S11, S12,... S1n are connected in series to form a first series portion, and the first parallel resonators P11, P12,. Are connected to each other to constitute a first parallel portion. The connection positions of the first parallel resonators P11, P12,... P1n with respect to the first series part are between the adjacent ones of the first series resonators S11, S12,. Or a node between the first series resonator S1n and the first terminal TX. The first filter 2 further includes n first inductors L11, L12,... L1n connected between the first parallel resonators P11, P12,. Here, the first inductor L12 includes two portions L12-1 and L12-2.

  Similarly, the second filter 3 is a ladder-type filter, and m (where m is an integer of 2 or more) second series resonances composed of piezoelectric resonators such as surface acoustic wave resonators and thin film piezoelectric resonators. ... S2m and m second parallel resonators P21, P22, ... P2m. The second series resonators S21, S22,... S2m are connected in series to form a second series portion, and the second parallel resonators P21, P22,. Are connected to each other to form a second parallel portion. As shown in the figure, the connection positions of the second parallel resonators P21, P22,... P2m with respect to the second series part are between the adjacent ones of the second series resonators S21, S22,. Or a node between the second series resonator S2m and the second terminal RX. The second filter 3 further includes m second inductors L21, L22,... L2m connected between the second parallel resonators P21, P22,. Here, the second inductor L22 includes two portions L22-1 and L22-2.

  L1 of the first inductors L11, L12,... L1n is a specific first inductor, and L22 of the second inductors L21, L22,. The specific first inductor L12 is connected to the first parallel resonator P12 connected to the first series part at a position where the path to the antenna terminal 1 (path on the circuit) is second. . The first parallel resonator P11 is connected to the first series part at the position where the path to the antenna terminal 1 is first. The specific second inductor L22 is connected to the second parallel resonator P22 connected to the second series part at a position where the path to the antenna terminal 1 (path on the circuit) is second. . The second parallel resonator P21 is connected to the second series part at the position where the path to the antenna terminal 1 is first.

  A capacitive coupling 7 is formed between the specific first inductor L12 and the specific second inductor L22. The capacitive coupling 7 is formed by a capacitor, and one electrode of the capacitor is connected to the specific first inductor L12, and the other electrode of the capacitor is connected to the specific second inductor L22.

  FIG. 2 is a circuit diagram showing another embodiment of the duplexer of the present invention. 2, parts or elements having the same functions as those shown in FIG. 1 are denoted by the same reference numerals.

  In this embodiment, L12 of the first inductors L11, L12,... L1n is the specific first inductor, and L2m of the second inductors L21, L22,. It is said that. The specific first inductor L12 is connected to the first parallel resonator P12 connected to the first series part at a position where the path to the antenna terminal 1 (path on the circuit) is second. . The specific second inductor L2m is connected to the second parallel resonator P2m connected to the second series portion at a position where the path to the antenna terminal 1 (path on the circuit) is the mth position. .

  The specific first inductor L12 and the specific second inductor L2m form an inductive coupling 8. The inductive coupling is formed so that the current direction is opposite between the specific first inductor L12 and the specific second inductor L2m.

  The piezoelectric resonator constituting the first filter 2 and the second filter 3 in each of the embodiments shown in FIGS. 1 and 2 is a thin film piezoelectric resonator (FBAR) as shown in FIG. 3 or shown in FIG. Such a surface acoustic wave resonator is used.

A thin film piezoelectric resonator 9 whose longitudinal sectional view is shown in FIG. 3 is obtained by forming a lower electrode 11, a piezoelectric film 12, and an upper electrode 13 on a substrate 10 in this order. A portion where the lower electrode 11 and the upper electrode 13 overlap with each other with the piezoelectric film 12 interposed therebetween is a resonance portion 14, and a cavity portion 15 is formed between the substrate 10 and the resonance portion 14. The substrate 10 is made of any one of silicon (Si), silicon oxide (SiO ₂ ), gallium arsenide (GaAs), and glass, or a laminated structure thereof. Each of the lower electrode 11 and the upper electrode 13 is made of any one of molybdenum (Mo), gold (Au), aluminum (Al), ruthenium (Ru), platinum (Pt), tungsten (W), and titanium (Ti). Or a laminated structure of these. The piezoelectric film 12 is made of any one of aluminum nitride (AlN) and zinc oxide (ZnO), or has a laminated structure thereof.

  In addition to the membrane type thin film piezoelectric resonator having the cavity 15 between the flat surface of the substrate 10 and the lower electrode 11 as shown in FIG. Pit-type thin film piezoelectric resonator (not shown) having a recess for forming, Deep-RIE type thin film piezoelectric resonator (not shown) having a through hole for forming a cavity in the substrate 10, or a cavity An SMR type thin film piezoelectric resonator (not shown) using an acoustic mirror layer may be used instead of the portion 15.

  FIG. 4 is a plan view of the surface acoustic wave resonator. The surface acoustic wave resonator 16 is connected to an input terminal and an output terminal on a piezoelectric substrate 17 and has a pair of interdigital electrodes (IDT: Interdigital Transducer) having electrode fingers arranged to be intertwined with each other. 18 and reflectors 19 on both sides of the IDT are provided. The IDT 18 and the reflector 19 are made of a metal such as aluminum (Al), for example. Note that the number of electrode fingers of the reflector 19 and the IDT 18 in the drawing is smaller than the actual number.

  In the present invention, as shown in FIG. 5, the constituent parts composed of the piezoelectric resonators of the first filter (that is, the first series part and the first parallel part) and the constituent parts composed of the piezoelectric resonators of the second filter (ie, the first part). The second series part and the second parallel part) are each formed in the form of a filter chip 22 formed on a semiconductor, insulator, or piezoelectric substrate as described above, and these filter chips 22 are used as the first filter of the first filter. It is desirable to mount the inductor and the second inductor of the second filter on the multilayer substrate 21 such as a low temperature fired ceramic substrate (LTCC: Low Temperature Co-fired Ceramics) formed by the line pattern 20. Thereby, a much smaller duplexer can be realized. Further, as shown in FIG. 5, it is desirable that the filter chip 22 be mounted face-down using the metal bumps 23 to realize a duplexer with a lower profile. A cap 24 is attached to the multilayer substrate 21 so as to cover the filter chip 22.

  In the present invention, as shown in FIGS. 1 and 2, by using a third inductor 6 connected between the antenna terminal 1 and the ground, a matching circuit composed of a plurality of electric elements or a long line is used. There is no need to use a phase shifter having a long length, and an even smaller duplexer can be realized.

In the present invention, the specific first inductor is not limited to L12 in FIGS. 1 and 2, and may be any one of L13 to L1n, and the specific second inductor is L22 in FIG. It is not limited to L2m in 2, and any one of L23 to L2m or L22 to L2 (m-1) may be used.
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Example 1
FIG. 6 is a circuit diagram of the duplexer of the present embodiment. The duplexer of the present example corresponds to that of n = 3 and m = 3 in the embodiment of FIG.

  In the present embodiment, the second first inductors L12-1 and L12-2 constituting the first filter, and the second second inductors L22-1 and L22 constituting the second filter. The capacitor 7 that realizes capacitive coupling is connected between the terminal 2 and the terminal 2. As described above, the first parallel resonator P12 and the second parallel resonator P22 connected to the first series portion and the second series portion, respectively, at the position where the path to the antenna terminal 1 is the second position, By inserting capacitive coupling between the specific first inductor and the specific second inductor connected to each other, the transmission wave input port (TX port) of the first filter and the reception wave output port (RX port) of the second filter Even in a small duplexer that is close to each other, a duplexer with good isolation characteristics can be realized.

  FIG. 7 is a schematic exploded view showing a wiring configuration in the present embodiment. The multilayer substrate 21 shown in FIG. 5 has a first layer (denoted as one layer in FIG. 7), a second layer (denoted as two layers in FIG. 7) and a third layer (denoted as three layers in FIG. 7) in order from the top. ) Are stacked in this order. Two filter chips 22 corresponding to the first and second filters are mounted face down on the multilayer substrate 21. The first and second layers have first inductors L11, L12, and L13, second inductors L21, L22, and L23, and a third inductor 6 (indicated by symbol L3 in FIG. 7) depending on the line pattern. Is formed. The specific first inductor L12 and the specific second inductor L22 are arranged in close proximity, and the pattern electrodes C11 and C12 constituting the capacitor 7 connected to these inductors are opposed to each other through the first layer. In this manner, the first layer and the second layer are formed. The multilayer substrate of FIG. 7 is made of LTCC having a relative dielectric constant (εr) of 7.5, the thickness of the layer forming the gap between the pattern electrodes of the capacitor 7 is 50 μm, and the pattern electrodes C11 and C12 The dimension is 400 μm × 200 μm, and therefore the capacitance of the capacitor 7 is 0.1 [pF]. In the third layer, an antenna terminal (Ant) 1, a first terminal (transmitter connection terminal) Tx, a second terminal (receiver connection terminal) Rx, and a ground pattern that occupies most of the other regions are formed. Yes.

  This embodiment is a Band I band demultiplexer of W-CDMA (Wide Band Code Division Multiple Access). The first filter 2 is a transmission filter, and the passband frequency is 1920 to 1980 MHz. The second filter 3 is a reception filter, and the passband frequency is 2110 to 2170 MHz.

  FIG. 8 shows the pass characteristics of this embodiment. In the present embodiment, it can be seen that the attenuation characteristic in the transmission band of the second filter (reception filter) is improved as compared with that of Comparative Example 1 described later.

  Further, FIG. 9 is a diagram showing the isolation characteristics of this example. It can be seen that the isolation characteristics in the pass band of the first filter (transmission filter) of 1920-1980 MHz are good.

  Further, Table 1 shows the attenuation characteristics and isolation characteristics in the present embodiment. Similar to FIGS. 8 and 9, the attenuation characteristics and the transmission bands in the transmission band of the reception filter of the first embodiment compared to the first comparative example. It can be seen that the isolation characteristics at are improved.

(Example 2)
The present embodiment is the same as the first embodiment except that the dimensions of the pattern electrodes C11 and C12 constituting the capacitor 7 are 400 μm × 550 μm and the capacitance of the capacitor 7 is 0.3 [pF]. As shown in Table 1, it can be seen that the attenuation characteristic in the transmission band and the isolation characteristic in the transmission band of the reception filter of Example 2 are improved as compared with Comparative Example 1.

(Example 3)
In the present embodiment, L23 is used as the specific second inductor, the specific first inductor L12 and the specific second inductor L23 are arranged in close proximity to each other, and the pattern electrodes C11 and C12 constituting the capacitor 7 are connected to these inductors. Except for being connected, it is the same as the first embodiment. As shown in Table 1, it can be seen that the attenuation characteristic in the transmission band and the isolation characteristic in the transmission band of the reception filter of Example 3 are improved as compared with Comparative Example 1.

Example 4
In the present embodiment, L13 is used as the specific first inductor, and the specific first inductor L13 and the specific second inductor L22 are disposed in close proximity to each other, and the pattern electrodes C11 and C12 constituting the capacitor 7 are arranged in these inductors. Is the same as the first embodiment except that is connected. As shown in Table 1, it can be seen that the attenuation characteristics in the transmission band and the isolation characteristics in the transmission band of the reception filter of Example 4 are improved as compared with Comparative Example 1.

(Example 5)
FIG. 10 is a circuit diagram of the duplexer of the present embodiment. The duplexer of the present example corresponds to that of n = 3 and m = 3 in the embodiment of FIG.

  In the present embodiment, the second first inductor L12 constituting the first filter and the third second inductor L23 constituting the second filter form an inductive coupling 8. Yes. Further, the currents flowing through the two inductively coupled inductors are arranged in opposite directions. Thus, the first parallel resonator P12 and the second parallel connected to the first series part and the second series part at positions where the paths to the antenna terminal 1 are the second and third positions, respectively. The specific first inductor and the specific second inductor respectively connected to the resonator P23 are inductively coupled, whereby the transmission wave input port (TX port) of the first filter and the reception wave output port (RX) of the second filter Even in a small duplexer close to the port, a duplexer with good isolation characteristics can be realized.

  FIG. 11 is a schematic exploded view showing a wiring configuration in the present embodiment. In FIG. 11, parts or elements having the same functions as those shown in FIG.

  In the present embodiment, the specific first inductor L12 and the specific second inductor L23 are arranged in close proximity, and the distance between them, that is, the space G, is the first inductor L11 to L13 and the second inductor L21 to L23. It is smaller than the distance between any other combinations and is set to 200 μm. Thereby, the mutual inductance of the inductive coupling 8 is controlled well. Further, the inductor pattern is arranged so that the current flowing through the line pattern is opposite in the specific first inductor L12 and the specific second inductor L23.

  This embodiment is a Band I band demultiplexer of W-CDMA (Wide Band Code Division Multiple Access). The first filter 2 is a transmission filter, and the passband frequency is 1920 to 1980 MHz. The second filter 3 is a reception filter, and the passband frequency is 2110 to 2170 MHz.

  FIG. 12 shows the pass characteristic of this embodiment. In the present embodiment, it can be seen that the attenuation characteristic in the transmission band of the second filter (reception filter) is improved as compared with that of Comparative Example 1 described later.

  Further, FIG. 13 is a diagram showing the isolation characteristics of this example. It can be seen that the isolation characteristics in the pass band of the first filter (transmission filter) of 1920-1980 MHz are good.

  Further, Table 1 shows the attenuation characteristics and isolation characteristics in the present embodiment. Similar to FIGS. 12 and 13, the attenuation characteristics and the transmission bands in the transmission band of the reception filter of the fifth embodiment compared to the first comparative example. It can be seen that the isolation characteristics at are improved.

(Example 6)
The present embodiment is the same as the fifth embodiment except that the space (G) between the specific first inductor L12 and the specific second inductor L23 that are inductively coupled is set to 100 μm. As shown in Table 1, it can be seen that the attenuation characteristics in the transmission band and the isolation characteristics in the transmission band of the reception filter of Example 6 are improved as compared with Comparative Example 1.

(Example 7)
The present embodiment is the same as the fifth embodiment except that L22 is used as the specific second inductor. As shown in Table 1, it can be seen that the attenuation characteristic in the transmission band and the isolation characteristic in the transmission band of the reception filter of Example 7 are improved as compared with Comparative Example 1.

(Example 8)
The present embodiment is the same as the seventh embodiment except that L13 is used as the specific first inductor. As shown in Table 1, it can be seen that the attenuation characteristic in the transmission band and the isolation characteristic in the transmission band of the reception filter of Example 8 are improved as compared with Comparative Example 1.

(Comparative Example 1)
FIG. 14 is a circuit diagram showing the duplexer of the first comparative example. This comparative example is the same as Example 1 except that it does not have capacitive coupling connected between the first inductor and the second inductor.

  As shown in FIGS. 8 and 12 and Table 1, it can be seen that the attenuation characteristics of the second filter (reception filter) are degraded as compared with those of the first to eighth embodiments. Further, as shown in FIGS. 9 and 13 and Table 1, the isolation characteristics in the pass band of the first filter (transmission filter) of 1920-1980 MHz are deteriorated compared to those of the first to eighth embodiments. .

(Comparative Example 2)
FIG. 15 is a circuit diagram showing the duplexer of the second comparative example. This comparative example is the same as Example 5 except that the first inductor L11 is inductively coupled to the third second inductor L23.

  FIG. 16 shows the pass characteristics of Comparative Example 1 and Comparative Example 2. In Comparative Example 2, it can be seen that the attenuation characteristics of the second filter (reception filter) are deteriorated as compared with Comparative Example 1. Further, FIG. 17 is a diagram showing the isolation characteristics of Comparative Example 1 and Comparative Example 2. It can be seen that the isolation characteristics in the pass band of the first filter (transmission filter) of 1920-1980 MHz are degraded. Further, Table 1 shows the attenuation characteristics and isolation characteristics in Comparative Example 2. Similar to FIGS. 16 and 17, the attenuation characteristics and transmission bands in the transmission band of the reception filter of Comparative Example 2 compared to Comparative Example 1 are shown. It can be seen that the isolation characteristics in the are degraded.

  In this way, the first first inductor and the second and subsequent second inductors are inductively coupled, so that the reception filter in the transmission band can be compared with Comparative Example 1 that does not have inductive coupling. It can be seen that the attenuation characteristics and the isolation characteristics in the transmission band deteriorate.

(Comparative Example 3)
FIG. 18 is a circuit diagram showing the duplexer of the third comparative example. In this comparative example, the second inductor that forms capacitive coupling with the second first inductors L12-1 and L12-2 is the first first inductor L21 (ie, L21-1, L21-2). Other than the above, this embodiment is the same as the first embodiment.

  FIG. 19 shows the pass characteristics of Comparative Example 1 and Comparative Example 3. In Comparative Example 3, it can be seen that the attenuation characteristic of the second filter (reception filter) is deteriorated as compared with Comparative Example 1. Further, FIG. 20 is a diagram showing the isolation characteristics of Comparative Example 1 and Comparative Example 3. It can be seen that the isolation characteristics in the pass band of the first filter (transmission filter) of 1920-1980 MHz are degraded. Further, Table 1 shows the attenuation characteristics and isolation characteristics in Comparative Example 3. As in FIG. 19 and FIG. 20, the attenuation characteristics and transmission bands in the transmission band of the reception filter of Comparative Example 3 compared to Comparative Example 1 are shown. It can be seen that the isolation characteristics in the are degraded.

  In this way, by introducing capacitive coupling between the first second inductor and the second and subsequent first inductors, the transmission band is higher than that of Comparative Example 1 that does not have capacitive coupling. It can be seen that the attenuation characteristic of the reception filter and the isolation characteristic in the transmission band are degraded.

DESCRIPTION OF SYMBOLS 1 Antenna terminal 2 1st filter 3 2nd filter 6 3rd inductor 7 Capacitive coupling (capacitor)
8 Inductive coupling (two inductors coupled together)
DESCRIPTION OF SYMBOLS 9 Thin film piezoelectric resonator 10 Substrate 11 Lower electrode 12 Piezoelectric film 13 Upper electrode 14 Resonant part 15 Cavity part 16 Surface acoustic wave resonator 17 Piezoelectric substrate 18 Interdigital electrode (IDT)
19 reflector 20 line pattern 21 multilayer substrate 22 filter chip 23 metal bump 24 cap S11, S12, S13, S1n first series resonator S21, S22, S23, S2m second series resonator P11, P12, P13, P1n first Parallel resonators P21, P22, P23, P2m Second parallel resonators L11, L12, L13, L1n First inductors L21, L22, L23, L2m Second inductors C11, C12 Pattern electrodes of capacitors

Claims (10)

An antenna terminal, a first terminal, a second terminal, a first filter connected between the antenna terminal and the first terminal, and a first filter connected between the antenna terminal and the second terminal A duplexer comprising a second filter having a higher pass frequency than
The first filter is connected between the antenna terminal and the first terminal and includes a first series unit formed by connecting a plurality of first series resonators in series, and a plurality of first parallel resonators. And a plurality of first inductors connected between the plurality of first parallel resonators and the ground, respectively.
The second filter is connected between the antenna terminal and the second terminal and includes a second series unit formed by connecting a plurality of second series resonators in series, and a plurality of second parallel resonators. And a plurality of second inductors respectively connected between the plurality of second parallel resonators and the ground;
Capacitive coupling is formed between a specific first inductor that is any one of the plurality of first inductors and a specific second inductor that is any one of the plurality of second inductors. Has been
The specific first inductor is connected to the first parallel resonator connected to the first series part at a position where the proximity of the path to the antenna terminal is any one after the second,
The specific second inductor is connected to the second parallel resonator connected to the second series unit at a position where the path to the antenna terminal is any second or later. Characteristic duplexer.   The capacitive coupling is formed by a capacitor, and one electrode of the capacitor is connected to the specific first inductor, and the other electrode of the capacitor is connected to the specific second inductor. The duplexer according to claim 1. An antenna terminal, a first terminal, a second terminal, a first filter connected between the antenna terminal and the first terminal, and a first filter connected between the antenna terminal and the second terminal A duplexer comprising a second filter having a higher pass frequency than
The first filter is connected between the antenna terminal and the first terminal and includes a first series unit formed by connecting a plurality of first series resonators in series, and a plurality of first parallel resonators. And a plurality of first inductors connected between the plurality of first parallel resonators and the ground, respectively.
The second filter is connected between the antenna terminal and the second terminal and includes a second series unit formed by connecting a plurality of second series resonators in series, and a plurality of second parallel resonators. And a plurality of second inductors respectively connected between the plurality of second parallel resonators and the ground;
The specific first inductor, which is any one of the plurality of first inductors, and the specific second inductor, which is any one of the plurality of second inductors, form inductive coupling. And
The specific first inductor is connected to the first parallel resonator connected to the first series part at a position where the proximity of the path to the antenna terminal is any one after the second,
The specific second inductor is connected to the second parallel resonator connected to the second series unit at a position where the path to the antenna terminal is any second or later. Characteristic duplexer.   4. The duplexer according to claim 3, wherein the inductive coupling is formed so that current directions are opposite between the specific first inductor and the specific second inductor. 5.   5. The duplexer according to claim 1, wherein at least one of the first filter and the second filter is a ladder-type filter.   Furthermore, it has a 3rd inductor connected between the connection part of the said antenna terminal, the said 1st filter, and the said 2nd filter, and a ground, The Claim 1 thru | or 5 characterized by the above-mentioned. The duplexer described in 1.   The first series part, the first parallel part, the second series part, and the second parallel part are formed on a chip, and the chip is mounted on a substrate, and includes a plurality of the first inductors, The duplexer according to any one of claims 1 to 6, wherein the plurality of second inductors are configured by a line pattern formed on the substrate.   The distance between the specific first inductor and the specific second inductor is smaller than a distance between any combination of the plurality of first inductors and the plurality of second inductors. Item 8. The duplexer according to any one of Items 1 to 7.   The first series resonator, the first parallel resonator, the second series resonator, and the second parallel resonator are surface acoustic wave resonators, according to any one of claims 1 to 8. The duplexer according to one item.   The first series resonator, the first parallel resonator, the second series resonator, and the second parallel resonator are thin film piezoelectric resonators. The duplexer described in the paragraph.

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