Composite filter and communication device

Abstract

Provided is a composite filter, wherein first to third filters are connected to any ports of a first hybrid that is constituted by 90° hybrid couplers. The first filter has a first passband. The second and third filters have passbands that do not overlap the first passband. An electrical interval from the first filter to the first hybrid is referred to as a first portion. A combination of an electrical interval from the second filter to the first hybrid and an electrical interval from the third filter to the first hybrid is referred to as a second portion. Here, at least one of the first portion and the second portion does not have a matching circuit having an inductor that is constituted by conductors of a multilayer substrate.

Description

Composite filter and communication device

[0001] The present disclosure relates to a composite filter having two or more filters, and a communication device having the composite filter.

[0002] A composite filter including two or more filters and a 90° hybrid coupler (hereinafter sometimes simply referred to as a "hybrid") connected to the two or more filters is known (see, for example, Patent Document 1 below). The composite filter disclosed in Patent Document 1 is configured as a duplexer. In this duplexer, an antenna, a transmit filter, a first receive filter, and a second receive filter are connected to each of the four ports of the hybrid. In Patent Document 1, the use of the hybrid improves isolation between the transmit side and the receive side.

[0003] Generally, a matching circuit for impedance matching is provided between each port of the hybrid and an electronic element (a filter in Patent Document 1) connected to each port. Patent Document 1 does not mention whether or not a matching circuit is provided.

[0004] International Publication No. 2009 / 078095

[0005] A composite filter according to one aspect of the present disclosure includes a first hybrid, a first filter, a second filter, and a third filter. The first hybrid is configured as a 90-degree hybrid coupler having a first port, a second port, and a third port and a fourth port to which a signal input to the first port or the second port is distributed. The first filter is connected to the second port and has a first passband. The second filter is connected to the third port and has a second passband that does not overlap with the first passband. The third filter is connected to the fourth port and has the second passband. An electrical section from the first filter to the first hybrid is defined as a first part. A combination of an electrical section from the second filter to the first hybrid and an electrical section from the third filter to the first hybrid is defined as a second part. In this case, at least one of the first part and the second part does not include a matching circuit having an inductor formed by a conductor of a multilayer substrate.

[0006] A composite filter according to one aspect of the present disclosure includes a first hybrid, a first filter, a second filter, and a third filter. The first hybrid is configured as a 90° hybrid coupler having a first port, a second port, and a third port and a fourth port to which a signal input to the first port or the second port is distributed. The first filter is connected to the second port and has a first passband. The second filter is connected to the third port and has a second passband that does not overlap with the first passband. The third filter is connected to the fourth port and has the second passband. An electrical section from the first filter to the first hybrid is defined as a first section. A combination of an electrical section from the second filter to the first hybrid and an electrical section from the third filter to the first hybrid is defined as a second section. In this case, at least one of the first section and the second section includes a matching circuit having a capacitor.

[0007] A communication device according to one aspect of the present disclosure includes any of the composite filters described above, an antenna connected to the first port, and integrated circuit elements connected to the first filter, the second filter, and the third filter on the electrically opposite side of the first hybrid.

[0008] FIG. 1 is a circuit diagram showing the configuration of a composite filter according to a first embodiment. FIG. 2 is a diagram showing an example of the reflection characteristics of a receive filter included in a composite filter according to an example. FIG. 3 is a diagram showing the pass characteristics of composite filters according to a comparative example and an example. FIG. 4 is a circuit diagram showing the configuration of a composite filter according to a second embodiment. FIG. 5 is a circuit diagram showing the configuration of a composite filter according to a third embodiment. FIG. 6 is a schematic cross-sectional view showing an example of the structure of a composite filter. FIG. 7 is a plan view showing an example of the configuration of a resonator included in a composite filter. FIG. 8 is a circuit diagram showing an example of the configuration of a transmit filter and a receive filter included in a composite filter. FIG. 9 is a block diagram showing an example of the configuration of a communication device including a composite filter.

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The drawings used in the following description are schematic. Therefore, for example, the dimensional ratios in the drawings do not necessarily correspond to the actual ones. Furthermore, the dimensional ratios may not match between drawings. Certain shapes and / or dimensions may be exaggerated, and details may be omitted. However, the above does not deny that the actual shapes and / or dimensions may be as shown in the drawings, or that features of shapes and / or dimensions may be extracted from the drawings.

[0010] In the description of multiple aspects, for the later-described aspects, basically, only the differences from the previously described aspects will be described. Matters not specifically mentioned may be considered to be the same as the previously described aspects or may be inferred from the previously described aspects. Furthermore, for convenience, the same reference numerals may be used for corresponding components in multiple aspects, even if there are differences. Conversely, for convenience of explanation, different reference numerals may be used for the same components.

[0011] In the present disclosure, when the phase of a signal is "shifted," the phase may be advanced or delayed. However, for convenience, when referring to the above, unless a contradiction arises, "shift" or the like will mean only one of the two terms commonly used for various components and various signals. For example, when it is said that the phase of a second signal is shifted by 90° relative to the phase of a first signal, and the phase of a fourth signal is shifted by 90° relative to the phase of a third signal, the former and latter shifts are both shifts in phase that are advanced by 90°, or both shifts in phase that are delayed by 90°.

[0012] (Outline of the Embodiment) FIG. 1 is a circuit diagram showing the configuration of a composite filter 1 according to a first embodiment.

[0013] The composite filter 1 is configured as a duplexer and includes, for example, a transmission path 2T that filters a transmission signal from a transmission terminal 7 and outputs the filtered signal to an antenna terminal 5, and a reception path 2R that filters a reception signal from the antenna terminal 5 and outputs the reception signal to a reception terminal 9.

[0014] The transmission path 2T has a transmission filter system 12 that is directly responsible for filtering the transmission signal. The transmission filter system 12 includes a transmission filter 13. The reception path 2R has a reception filter system 14 that is directly responsible for filtering the reception signal. The reception filter system 14 has reception filters 15A and 15B (hereinafter, the two may be simply referred to as reception filters 15 without distinguishing between them).

[0015] The transmit filter system 12 (transmit filter 13) passes signals in the transmit band (attenuates signals outside the transmit band). The receive filter system 14 (receive filter 15) passes signals in the receive band (attenuates signals outside the receive band). The transmit band and receive band are different frequency bands (they do not overlap). That is, the transmit filter 13 and receive filter 15 have pass bands that do not overlap. Note that the portion of the composite filter 1 that includes the transmit filter 13 and receive filter 15 and directly contributes to filtering is sometimes referred to as the duplexer main body 3.

[0016] A first hybrid 17, which is a 90° hybrid coupler, is interposed between the antenna terminal 5, the transmitting filter 13, and the receiving filters 15A and 15B. The first hybrid 17 contributes to reducing nonlinear distortion (distorted signals), for example, as will be described later.

[0017] The first hybrid 17 has four ports 17a to 17d. To put it simply based on common technical knowledge, the relationship between the ports 17a to 17d is such that a signal input to port 17a or 17b is distributed to ports 17c and 17d. The antenna terminal 5 and the transmit filter 13 are connected to ports 17a and 17b, respectively, and the receive filters 15A and 15B are connected to ports 17c and 17d, respectively.

[0018] When a transmission signal is input to the transmission terminal 7 from outside the composite filter 1, the transmission signal is filtered by the transmission filter 13 and input to the first hybrid 17. The transmission signal input to the first hybrid 17 is split into two transmission signals that are 90° out of phase with each other and distributed to the two reception filters 15. Because the transmission band and the reception band do not overlap, the two distributed transmission signals are reflected by the two reception filters 15 and input again to the first hybrid 17. The two input transmission signals are made into in-phase signals by the first hybrid 17, combined, and output to the antenna terminal 5.

[0019] The electrical section (first section 10A) from the transmit filter 13 to the first hybrid 17 will be referred to as the first section P1. The combination of the electrical section (second section 10B) from the receive filter 15A to the first hybrid 17 and the electrical section (third section 10C) from the receive filter 15B to the first hybrid 17 will be referred to as the second section P2. The term "electrical" is used because the "spatial" positional relationship is arbitrary. However, for convenience, this notation may be omitted. As can be understood from the description of the transmit signal in the previous paragraph, the first section P1 and the second section P2 are included in the transmit path 2T for outputting the transmit signal input to the transmit terminal 7 to the antenna terminal 5.

[0020] At least one of the first section P1 and the second section P2 does not have a matching circuit having an inductor formed by a conductor of a multilayer substrate. Specific examples of this include the following.

[0021] For example, the composite filter 1 may not have any portion formed by a multilayer substrate. Alternatively, the composite filter 1 may have a portion formed by a multilayer substrate, but the multilayer substrate does not have an inductor located in the first portion P1 and / or the second portion P2. From another perspective (regardless of whether the composite filter 1 includes a multilayer substrate), for example, the first portion P1 and / or the second portion P2 may not have a matching circuit at all (as in the example of FIG. 1 ), or may have a matching circuit that does not include an inductor. Alternatively, the first portion P1 and / or the second portion P2 may have a matching circuit that includes an inductor, but the inductor is not built into the multilayer substrate. Examples of inductors that are not built into the multilayer substrate include chip inductors mounted on the surface of the multilayer substrate and chip inductors embedded inside the multilayer substrate.

[0022] In the following description, an electronic element (e.g., an inductor) made up of the conductors of a multilayer substrate may be referred to as a "built-in" electronic element. An electronic element mounted on the surface of a multilayer substrate may be referred to as a "mounted" electronic element. A chip-type electronic element embedded inside a multilayer substrate may be referred to as an "embedded" electronic element. "Built-in" is sometimes used as a broader term (antonym of "mounted") for "built-in" and "embedded." "Built-in" does not require that the element be hidden inside the multilayer substrate. For example, a built-in electronic element may be partially or entirely composed of a conductor layer that the multilayer substrate has on its surface.

[0023] Generally, a matching circuit for impedance matching is provided between the hybrid and another electronic element (here, a filter) (for example, the first section P1 and the second section P2). However, by not providing a built-in inductor in the first section P1 and / or the second section P2 as described above, the pass characteristics of the transmission path 2T can be improved. More specifically, the insertion loss can be reduced. The reason for this is that, for example, built-in inductors generally have a low Q value (Quality Factor), which can cause insertion loss.

[0024] The above is an overview of the first embodiment. Although the first embodiment and the other embodiments differ in overall configuration, they have in common the fact that they include a first hybrid 17 and three filters (13 and 15) connected to the first hybrid 17, and that the first section P1 and / or the second section P2 do not have built-in inductors. Various embodiments according to the present disclosure will be described below in the following order: 1. First Embodiment 1.1. Configuration of the Composite Filter 1 (FIG. 1) 1.1.1. Filter 1.1.2. Hybrid 1.1.3. Termination Resistor 1.1.4. Matching Circuit 1.2. Operation of the Composite Filter 1 1.2.1. Transmission of Transmitted Signal 1.2.2. Transmission of Received Signal 1.2.3. Example of Reduction of Nonlinear Distortion 1.3. Characteristics of Comparative Examples and Examples (FIGS. 2 and 3) 2. Second Embodiment (FIG. 4) 3. Third Embodiment (FIG. 5) 4. Other Embodiments 5. 6. Structural example of composite filter 1 (FIG. 6) 6. Configuration examples of transmit filter 13 and receive filter 15 6.1. Example of acoustic wave element (FIG. 7) 6.2. Configuration example of duplexer main body using acoustic wave filter (FIG. 8) 7. Example of communication device including composite filter 1 (FIG. 9) 8. Summary of embodiments

[0025] In Section 5 and subsequent sections, the reference numerals of a specific embodiment (mainly the first embodiment) among multiple embodiments may be used. However, unless a contradiction or the like arises, the explanations in Section 5 and subsequent sections may be applied to embodiments other than the specific embodiment.

[0026] (1. First Embodiment) (1.1. Configuration of Composite Filter 1) The outline of the configuration of the composite filter 1 according to the first embodiment has already been described. In addition to the components already described, the composite filter 1 also has a second hybrid 19. The second hybrid 19 is interposed between the receiving terminal 9 and the receiving filters 15A and 15B. The composite filter 1 may also have a termination resistor 23 connected to an unused port 19c of the second hybrid 19, and one or more matching circuits 24 provided at appropriate positions.

[0027] In the description of the outline of the embodiment, the first section 10A to the third section 10C, the first section P1, and the second section P2 are defined. Similarly, the combination of the electrical section (fourth section 10D) from the receive filter 15A to the second hybrid 19 and the electrical section (fifth section 10E) from the receive filter 15B to the second hybrid 19 is referred to as the third section P3.

[0028] Each of the first section 10A through the fifth section 10E is sandwiched between one filter (13 or 15) and one hybrid (17 or 15). Each section does not include the filter or hybrid, but refers to the entire area between the filter and the hybrid. Therefore, for example, when it is said that the second section 10B does not have a matching circuit, it does not mean that there is no matching circuit between the receive filter 15A and the first hybrid 17. In other words, when it is said that the second section 10B does not have a matching circuit, it is not interpreted as meaning that there is another section between the receive filter 15A and the first hybrid 17 in series with the second section 10B, and that this other section may have a matching circuit. The same applies to the first section P1 through the third section P3.

[0029] Furthermore, each of the first section 10A to the fifth section 10E is considered to be a broad concept that includes not only the components (components connected in series) connecting the filter and the hybrid, but also components connected in other ways between the filter and the hybrid. For example, not only the wiring connecting the filter and the hybrid, but also the electronic element (e.g., inductor) connecting the wiring to the reference potential unit 11 constitutes the section between the filter and the hybrid. Therefore, for example, if the electronic element constitutes a matching circuit, the section is considered to have the matching circuit. The same applies to the first section P1 to the third section P3.

[0030] The reference potential portion 11 is a portion (conductor) to which a reference potential is applied. More specifically, the reference potential portion 11 may be, for example, a terminal to which a reference potential is applied, or may be a configuration other than a terminal (for example, a shield).

[0031] The components of the composite filter 1 will be described below in order.

[0032] (1.1.1. Filter) The transmit filter 13 is a band-pass filter with a predetermined transmit band as its pass band. Similarly, the receive filter 15 is a band-pass filter with a predetermined receive band as its pass band. The transmit band and receive band may conform to, for example, various standards. Furthermore, the transmit band may include two or more transmit bands that conform to predetermined standards. The same applies to the receive band.

[0033] The receive filters 15A and 15B correspond to the same receive band. That is, the passbands of the receive filters 15A and 15B are substantially and / or design-wise identical. The receive filters 15A and 15B have the same or similar configurations and substantially or design-wise identical characteristics. However, the receive filters 15A and 15B may be fine-tuned so that their passbands and / or characteristics are slightly different.

[0034] The specific configurations of the transmit filter 13 and the receive filter 15 may be, for example, known configurations or applications of known configurations. For example, the transmit filter 13 and / or the receive filter 15 may be piezoelectric filters including piezoelectric elements, dielectric filters utilizing electromagnetic waves in a dielectric, LC filters combining inductors and capacitors, or a combination of two or more of these. The piezoelectric filter may utilize elastic waves or may not (e.g., utilize a piezoelectric vibrator). The elastic waves may be, for example, surface acoustic waves (SAWs), bulk acoustic waves (BAWs), boundary acoustic waves, plate waves, or bulk waves (however, these elastic waves are not necessarily distinguishable). Plate waves and bulk waves may propagate in the direction of expansion of the plate (piezoelectric element) or in the thickness direction of the plate.

[0035] (1.1.2. Hybrid) The first hybrid 17 has four ports 17a to 17d for inputting and / or outputting signals, and also functions as a distributor, a combiner, and a 90° phase shifter. The configuration of the first hybrid 17 may be, for example, a known configuration or an application of a known configuration. For example, although not specifically shown, the first hybrid 17 may be a distributed constant type or a lumped constant type. A branch-line coupler is well known as the first hybrid 17.

[0036] Ports 17a and 17b on the left side of the drawing are electrically connected to ports 17c and 17d on the right side of the drawing. "Electrical connection" here means that a signal can flow. For example, a signal input to port 17a can be output from ports 17c and 17d.

[0037] For convenience, the description of this embodiment may be based on the positional relationship of the ports 17a to 17d in the diagram showing the first hybrid 17. However, the positional relationship of the four ports 17a to 17d on the diagram does not have to match the positional relationship of the four actual ports 17a to 17d.

[0038] A signal input to port 17a on the left side of the drawing is distributed to ports 17c and 17d on the right side of the drawing. The distribution ratio (ratio of the intensities of the two distributed signals) is 1:1. The intensities may be, for example, voltage, current, and / or power. The phases of the two distributed signals are shifted by 90° from each other.

[0039] The phase of the signal before distribution (for example, the signal input to port 17a) may be the same as the phase of one of the two signals after distribution (for example, the signal output from port 17c). Also, unlike the above, the phase of the signal before distribution may be different from the phase of both of the two signals after distribution. However, for convenience, in the description of this embodiment, the phase of the signal before distribution may be described as if the phase of one of the two signals after distribution is the same. Specifically, the phase of the signals of ports (for example, ports 17a and 17c) located at the same vertical position on the page may be described as if the signals are the same.

[0040] Although the above explanation takes the case where a signal is input to port 17a as an example, the above operation is similar when signals are input to the other ports 17b to 17d. That is, a signal input to one of the two ports located on one side of the paper is distributed at a distribution ratio of 1:1 and output from the two ports located on the other side of the paper. At this time, the phases of the two distributed signals are shifted by 90° from each other.

[0041] As mentioned above, when a phase is shifted, for convenience, it refers to either an advance or a delay in phase, common to various components and various signals, etc. In the illustration of the drawings, it is assumed that a signal output from a port (e.g., 17d) located in a different position in the vertical direction from the port to which the signal was input (e.g., 17a) is shifted in phase by 90° with respect to a signal output from a port (e.g., 17c) located in the same vertical direction as the port to which the signal was input (e.g., 17a).

[0042] Since a hybrid operating as described above is called a 90° hybrid, the relationship between the four ports of the first hybrid 17 can be determined from a description of only some of the ports. For example, assume that port 17d is described as a port from which a signal with a phase shift of 90° relative to the phase of the signal distributed from port 17a to port 17c is distributed from port 17a. From this description, it follows that port 17a and the remaining port 17b are located on the same horizontal side of the paper, and ports 17c and 17d are located on the opposite side, and that port 17a and port 17c are located on the same vertical side of the paper, and ports 17b and 17d are located on the opposite side. When the relationship between the four ports is described using the signal distributed from port 17a as described above, the first hybrid 17 does not necessarily need to be configured in such a way that a signal is actually input from port 17a. The same applies when a signal is distributed from other ports.

[0043] Furthermore, for example, when there is no need to particularly distinguish between two ports (e.g., 17c and 17d) located on the same left-right side of the paper, a more concise explanation can be provided. For example, as described in the overview of the embodiment, assume that ports 17c and 17d are described as ports to which a signal input to port 17a or 17b is distributed. From this explanation, it follows that port 17a and the remaining port 17b are located on the same left-right side of the paper, and ports 17c and 17d are located on the opposite side. When the relationship between the four ports is described using a signal distributed from port 17a or 17b as described above, the first hybrid 17 does not actually need to be provided in a manner in which a signal is input from port 17a or 17b. The same applies when a signal is distributed from another port.

[0044] When signals are input to ports 17a and 17b on the left side of the drawing, each signal is distributed as described above, and the distributed signals are then combined. For example, the signal input to port 17a is the first signal, and the signal input to port 17b is the second signal. The signals obtained by distributing the first signal to ports 17c and 17d are the third and fourth signals. The fourth signal is 90° out of phase with the third signal. The signals obtained by distributing the second signal to ports 17c and 17d are the fifth and sixth signals. The fifth signal is 90° out of phase with the sixth signal. In this case, a signal obtained by combining the third and fifth signals is output to port 17c, and a signal obtained by combining the fourth and sixth signals is output to port 17d. While the example has been given of signals being input to the two ports 17a and 17b on the left side of the drawing, the same applies to signals being input to the two ports 17c and 17d on the right side of the drawing.

[0045] As described above, for example, there may be a phase difference between the first signal (input to port 17a) and the third signal (distributed to port 17c without phase shift), and there may be a phase difference between the second signal (input to port 17b) and the sixth signal (distributed to port 17d without phase shift). In this case, the two phase differences are the same. The two phase differences when the signals are in opposite directions are also the same as the two phase differences.

[0046] Although the first hybrid 17 has been described, the above description may be applied to the second hybrid 19 by replacing the term first hybrid 17 with the term second hybrid 19 and by replacing the terms ports 17a to 17d with the terms ports 19a to 19d. The specific configuration of the first hybrid 17 (e.g., the shape and dimensions of the conductors) and the specific configuration of the second hybrid 19 may be the same as or different from each other.

[0047] In the first hybrid 17, the connections between the ports 17a to 17d and the other elements (the antenna terminal 5, the transmit filter 13, and the two receive filters 15) are as already described. In the second hybrid 19, the port 19a is connected to the receive filter 15A. The port 19b is connected to the receive filter 15B. The port 19c is connected to the termination resistor 23 as already described. The port 19d is connected to the receive terminal 9.

[0048] (1.1.3. Termination Resistor) The termination resistor 23 has, for example, a predetermined resistance value, and connects the port 19c of the second hybrid 19 to a reference potential section (not shown). This reduces, for example, reflection of signals flowing from the ports 19a and / or 19b to the port 19c. The resistance value of the termination resistor 23 may be set appropriately depending on the impedance on the second hybrid 19 side relative to the termination resistor 23, but is generally 50Ω.

[0049] The termination resistor 23 may have a known configuration or may be an application of a known configuration. For example, although not specifically shown, the termination resistor 23 may be a mounted, embedded, or built-in resistor located on a circuit board (e.g., a multilayer board 61 described later). The termination resistor 23 may also be a built-in resistor (e.g., a conductor pattern overlapping an upper surface 31a of a piezoelectric element 31b described later) located on a piezoelectric substrate 31 described later. The termination resistor 23 may also be provided outside the composite filter 1.

[0050] (1.1.4. Matching Circuit) The matching circuit 24 is for improving impedance matching and may be provided at any position and in any configuration. However, as described above, at least one of the first section P1 and the second section P2 does not have a matching circuit 24 with a built-in inductor.

[0051] 1, the second section P2 does not include the matching circuit 24. For example, the second section P2 does not include a built-in inductor or any other type of inductor, nor does it include various types of capacitors or resistors. In other words, only a wire is interposed between the port 17c and the receive filter 15A, and only a wire is interposed between the port 17d and the receive filter 15B.

[0052] When each part (P1 to P3) or each section (10A to 10E) does not have a matching circuit, it may not have any electronic elements (inductors, capacitors, resistors, etc.), or it may have electronic elements that do not constitute a matching circuit. Furthermore, with regard to the presence or absence of a matching circuit, the resistance, capacitance, and inductance that the wiring itself inevitably contains are ignored.

[0053] In the example of Fig. 1, the composite filter 1 has a matching circuit 24 at a position other than the second section P2. More specifically, the matching circuits 24 are provided in three locations: the first section 10A, the fourth section 10D, and the fifth section 10E. However, these locations are merely examples of locations where the matching circuits 24 may be provided. For example, the matching circuits 24 may be provided at a location other than the above three locations, or may not be provided at any of the above three locations. Furthermore, the matching circuits 24 may not be provided at all.

[0054] 1 shows the matching circuit 24 configured by an inductor L that connects the path through which the signal flows and the reference potential unit 11. However, this is merely an example. For example, the components that configure the matching circuit 24 may be capacitors or resistors. The matching circuit 24 may also be a combination of two or more components. Each of the one or more components that configure the matching circuit 24 may connect the path through which the signal flows and the reference potential unit 11, or may be connected in series to the path through which the signal flows.

[0055] 1, the three matching circuits 24 (inductors L) are denoted by the same reference numerals, but they may of course have different configurations. Furthermore, each of the one or more components constituting the matching circuit 24 may be of a built-in type, a mounted type, or an embedded type.

[0056] The matching circuit 24 in the first section 10A may contribute to, for example, setting the impedance when looking from the port 17b of the first hybrid 17 toward the transmit filter 13 to a reference value (e.g., 50Ω; the same applies below). Instead of or in addition to such impedance matching, the matching circuit 24 in the first section 10A may contribute to setting the impedance when looking from the transmit terminal 7 toward the transmit filter 13 to a reference value.

[0057] The matching circuit 24 in the fourth section 10D contributes to, for example, setting the impedance when looking toward the receive filter 15A from the port 19a of the second hybrid 19 to a reference value. Instead of or in addition to such impedance matching, the matching circuit 24 in the fourth section 10D may contribute to setting the impedance when looking toward the receive filter 15A from the port 17c of the first hybrid 17 to a reference value.

[0058] The matching circuit 24 in the fifth section 10E contributes to, for example, setting the impedance when looking toward the receive filter 15B from the port 19b of the second hybrid 19 to a reference value. Instead of or in addition to such impedance matching, the matching circuit 24 in the fifth section 10E may contribute to setting the impedance when looking toward the receive filter 15B from the port 17d of the first hybrid 17 to a reference value.

[0059] The contribution of a specific matching circuit 24 to impedance matching as viewed from a specific position can be determined, for example, by the impedance as viewed from the specific position being closer to a reference value when the specific matching circuit 24 is provided than when the specific matching circuit 24 is not provided. For example, if the impedance as viewed from the receive filter 15A side when the matching circuit 24 of the fourth section 10D is provided is closer to a reference value (ideally, equal to the reference value) than when the matching circuit 24 is not provided, then the matching circuit 24 can be considered to be contributing to impedance matching as viewed from the port 17c of the first hybrid 17. The reference value may be determined from the specifications of the composite filter 1, or may be determined by measuring the impedance as viewed from various positions.

[0060] (1.2. Operation of the Composite Filter) (1.2.1. Transmission of Transmission Signal) We have already described the outline of the operation in which a signal (transmission signal) input from outside the composite filter 1 to the transmission terminal 7 is transmitted to the antenna terminal 5. More details are as follows.

[0061] The signal filtered by the transmit filter 13 and having a frequency within the passband of the transmit filter 13 is input to port 17b of the first hybrid 17. The signal input to port 17b is distributed to ports 17c and 17d. The phase of the signal distributed to port 17c is shifted by 90° from the phase of the signal distributed to port 17d.

[0062] The signal distributed to and output from port 17c has a frequency within the pass band (transmission band) of the transmission filter 13, and is therefore reflected by the reception filter 15A, which has a pass band (reception band) different from the transmission band. Therefore, the signal output from port 17c returns to port 17c. Similarly, the signal distributed to and output from port 17d is reflected by the reception filter 15B and returns to port 17d.

[0063] The signal returning to port 17c is distributed to ports 17a and 17b. At this time, the phase of the signal distributed to port 17b is shifted by 90° from the phase of the signal distributed to port 17a. Similarly, the signal returning to port 17d is distributed to ports 17a and 17b. At this time, the phase of the signal distributed to port 17a is shifted by 90° from the phase of the signal distributed to port 17b.

[0064] The signal that passes from the transmit filter 13 through ports 17b and 17c in this order, is reflected by the receive filter 15A, returns to port 17c and is transmitted to port 17a, and the signal that passes from the transmit filter 13 through ports 17b and 17d in this order, is reflected by the receive filter 15B, returns to port 17d and is transmitted to port 17a are both in phase because they have a phase shift of 90° once. Therefore, the two signals are combined and output from port 17a to the antenna terminal 5.

[0065] On the other hand, the signal that passes from the transmit filter 13 through ports 17b and 17d in this order, is reflected by the receive filter 15B, returns to port 17d, and is transmitted to port 17b does not have a 90° phase shift. Similarly, the signal that passes from the transmit filter 13 through ports 17b and 17c in this order, is reflected by the receive filter 15A, returns to port 17c, and is transmitted to port 17b has a 90° phase shift twice. Therefore, the two signals are out of phase with each other and cancel each other out, so they are not output from port 17b.

[0066] For convenience of explanation, it has been stated that the signal returned to port 17c or 17d is distributed to port 17b, but the fact that no signal is output from port 17b means that no signal is actually distributed to port 17b. In other words, ignoring insertion loss, the strength of the signal output to antenna terminal 5 is the same as the strength of the signal input to transmission terminal 7.

[0067] When focusing only on the first hybrid 17, there is no electrical continuity between the port 17b to which the transmit filter 13 is connected and the port 17a to which the antenna terminal 5 is connected. As described above, the signal from the transmit filter 13 is transmitted to the antenna terminal 5 by utilizing reflection at the receive filter 15. Even in this case, the transmit filter 13 is said to be connected to the antenna terminal 5 via the first hybrid 17.

[0068] (1.2.2. Transmission of Received Signal) A signal (received signal) input from the antenna terminal 5 to port 17a of the first hybrid 17 is distributed to ports 17c and 17d. The phase of the signal distributed to port 17d is shifted by 90° from the phase of the signal distributed to port 17c.

[0069] The signal distributed to port 17c and output from port 17c passes through receiving filter 15A and is input to port 19a of second hybrid 19. The signal distributed to port 17d and output from port 17d passes through receiving filter 15B and is input to port 19b of second hybrid 19.

[0070] A signal input to port 19a is distributed to ports 19c and 19d. At this time, the phase of the signal distributed to port 19d is shifted by 90° from the phase of the signal distributed to port 19c. Similarly, a signal input to port 19b is distributed to ports 19c and 19d. At this time, the phase of the signal distributed to port 19c is shifted by 90° from the phase of the signal distributed to port 19d.

[0071] The signal transmitted from antenna terminal 5 to port 19d via ports 17a and 17c, receiving filter 15A, and port 19a in this order, and the signal transmitted from antenna terminal 5 to port 19d via ports 17a and 17d, receiving filter 15B, and port 19b in this order, are both in phase because they have a phase shift of 90° once. Therefore, the two signals are combined and output from port 19d to receiving terminal 9.

[0072] On the other hand, the signal transmitted from antenna terminal 5 to port 19c via ports 17a and 17c, receiving filter 15A, and port 19a in this order does not have a 90° phase shift. Also, the signal transmitted from antenna terminal 5 to port 19c via ports 17a and 17d, receiving filter 15B, and port 19b in this order has a 90° phase shift twice. Therefore, the two signals are out of phase and cancel each other out, so they are not output from port 19c.

[0073] For convenience of explanation, it has been stated that a signal input to port 19a or 19b is distributed to port 19c, but the fact that no signal is output from port 19c means that no signal is actually distributed to port 19c. In other words, ignoring insertion loss, the strength of the signal output to receiving terminal 9 is the same as the strength of the signal input to antenna terminal 5.

[0074] (1.2.3. Example of Reduction of Nonlinear Distortion) Nonlinear distortion (distorted signal) such as intermodulation distortion may occur due to the nonlinearity of the transmit filter 13 and / or the receive filter 15. An example of how the nonlinear distortion is reduced by using a hybrid will be described.

[0075] It is assumed that two signals are input to the transmitting terminal 7 and that nonlinear distortion occurs in the transmitting filter 13. It is assumed that this nonlinear distortion has a frequency within the receiving band of the receiving filter 15 and can pass through the receiving filter 15.

[0076] The nonlinear distortion input from the transmit filter 13 to the port 17b is distributed to the ports 17c and 17d. The phase of the nonlinear distortion distributed to the port 17c is shifted by 90° from the phase of the nonlinear distortion distributed to the port 17d.

[0077] The nonlinear distortion distributed to port 17c and output from port 17c is input to port 19a of second hybrid 19 via receive filter 15A. The nonlinear distortion distributed to port 17d and output from port 17d is input to port 19b of second hybrid 19 via receive filter 15B.

[0078] Nonlinear distortion input to port 19a is distributed to ports 19c and 19d. At this time, the phase of the nonlinear distortion distributed to port 19d is shifted by 90° from the phase of the nonlinear distortion distributed to port 19c. Similarly, nonlinear distortion input to port 19b is distributed to ports 19c and 19d. At this time, the phase of the nonlinear distortion distributed to port 19c is shifted by 90° from the phase of the nonlinear distortion distributed to port 19d.

[0079] The nonlinear distortion propagated from the transmit filter 13 to port 19d via ports 17b and 17c, receive filter 15A, and port 19a in this order has a phase shift of 90° twice. The nonlinear distortion propagated from the transmit filter 13 to port 19d via ports 17b and 17d, receive filter 15B, and port 19b in this order does not have a phase shift of 90°. Therefore, the two nonlinear distortions are out of phase with each other, cancel each other out, and are not output from port 19d. In other words, the nonlinear distortion is not input to the receive terminal 9.

[0080] On the other hand, the nonlinear distortion transmitted from transmit filter 13 to port 19c via ports 17b and 17c, receive filter 15A, and port 19a in this order, and the nonlinear distortion transmitted from transmit filter 13 to port 19c via ports 17b and 17d, receive filter 15B, and port 19b in this order, are both in phase because they are shifted by 90 degrees once. Therefore, the two signals are combined and input from port 19c to termination resistor 23. Consequently, the nonlinear distortion is released to the reference potential section or the like via termination resistor 23.

[0081] Next, assume that nonlinear distortion occurs in receive filter 15 when a transmit signal that is input from outside to transmit terminal 7 and passes through transmit filter 13 and first hybrid 17 is reflected by receive filter 15. The phase relationship of the nonlinear distortion that occurs in receive filter 15A and receive filter 15B at this time is the same as the phase relationship of the nonlinear distortion that occurs in transmit filter 13 and propagates to receive filters 15A and 15B described above. Therefore, using the same principle as above, the nonlinear distortion is absorbed by termination resistor 23 (it is not input to receive terminal 9).

[0082] 2 is a diagram showing the reflection characteristics of the second section 10B and the receiving filter 15A in the comparative example. This diagram was obtained by measuring the characteristics of a prototype.

[0083] In the comparative example, although not specifically shown, the second section 10B has a matching circuit 24. This matching circuit 24 has (only) an inductor. One end of the inductor is connected between the port 17c of the first hybrid 17 and the receive filter 15A, and the other end is connected to the reference potential unit 11. The fourth section 10D does not have a matching circuit. The inductor is a built-in type.

[0084] In Figure 2, the horizontal axis represents frequency (MHz). The vertical axis represents reflection characteristics (dB). Line Ln1 represents the reflection characteristics (S11 parameter) when viewed from port 17c toward the receiving filter 15A. Line Ln2 represents the reflection characteristics (S22 parameter) when viewed from the end of the receiving filter 15A on the second hybrid 19 side toward the receiving filter 15A. The range of approximately 1700 MHz to approximately 1800 MHz corresponds to the receiving band. The range of approximately 1800 MHz to approximately 1900 MHz corresponds to the transmitting band.

[0085] As shown in this figure, the S11 parameter (line Ln1) is lower than the S22 parameter (line Ln2) in the transmission band. That is, in the comparative example, the second section 10B has a matching circuit with a built-in inductor, which reduces the reflection characteristics when viewed from the first hybrid 17 toward the receive filter 15A. On the other hand, as described above, a transmit signal input to the transmit terminal 7 from outside the composite filter 1 is reflected by the receive filter 15 and output to the antenna terminal 5. Therefore, the reduction in reflection characteristics as described above causes insertion loss and reduces the pass characteristics of the transmit path 2T.

[0086] 3 is a diagram showing the transmission characteristics of the comparative example and the example, which are obtained by simulation calculation.

[0087] 1 , the first section 10A, the fourth section 10D, and the fifth section 10E have matching circuits 24, while the second section 10B and the third section 10C do not have matching circuits 24. In the comparative example, the first section 10A, the second section 10B, and the third section 10C have matching circuits 24, while the fourth section 10D and the fifth section 10E do not have matching circuits 24. Each matching circuit 24 has (only) an inductor L that connects the signal path and the reference potential section 11, similar to the matching circuit 24 illustrated in FIG.

[0088] In Figure 3, the horizontal axis represents frequency (MHz). The vertical axis represents pass characteristics (dB). Line LnE represents the characteristics of the example. Line LnC represents the characteristics of the comparative example. The range of approximately 1700 MHz to approximately 1800 MHz corresponds to the receive band. The range of approximately 1800 MHz to approximately 1900 MHz corresponds to the transmit band.

[0089] As shown in this figure, in the transmit band, the pass characteristics of the example are improved compared to those of the comparative example. In the receive band, the pass characteristics of the example are deteriorated compared to those of the comparative example. However, the degree of deterioration is small compared to the degree of improvement in the pass characteristics in the transmit band. In this way, by not providing the matching circuit 24 in the second section P2 and concentrating the matching circuit 24 in the third section P3, the pass characteristics of the entire pass band of the composite filter 1 (the entire transmit band and receive band) are improved on average.

[0090] 2. Second Embodiment FIG. 4 is a circuit diagram showing the configuration of a composite filter 201 according to a second embodiment.

[0091] In short, the composite filter 201 has a configuration in which the transmit filter 13 and the receive filter 15 are swapped and the transmit terminal 7 and the receive terminal 9 are swapped in the composite filter 1 of the first embodiment. The position of the matching circuit 24 is also different from that of the first embodiment. For ease of explanation, the first section 10A to the fifth section 10E and the first section P1 to the third section P3 refer to the same positions as in FIG. 1, with the first hybrid 17 and the second hybrid 19 as reference points.

[0092] The transmission path 202T includes, in order from the transmission terminal 7 to the antenna terminal 5, a second hybrid 19, a transmission filter system 212, and a first hybrid 17. Unlike the first embodiment, the transmission filter system 212 includes two transmission filters 13 (13A and 13B). The connection relationship between these filters can be explained using the same explanation for the connection relationship in the reception path 2R in the first embodiment. However, the terms reception filters 15A and 15B (15) are replaced with the terms transmission filters 13A and 13B (13), and the term reception terminal 9 is replaced with the term transmission terminal 7.

[0093] The two transmit filters 13 correspond to the same pass band (however, unlike the first embodiment, the transmit band), similar to the two receive filters 15 in the first embodiment. The two transmit filters 13 may have the same configuration and characteristics, similar to the two receive filters 15 in the first embodiment.

[0094] The receiving path 202R includes, in order from the antenna terminal 5 to the receiving terminal 9, a receiving filter system 214 and a first hybrid 17. Unlike the first embodiment, the receiving filter system 214 includes one receiving filter 15. The connection relationship between these elements may be the same as that described for the transmitting path 2T in the first embodiment, except that the term "transmitting filter 13" is replaced with the term "receiving filter 15" and the term "transmitting terminal 7" is replaced with the term "receiving terminal 9."

[0095] The strength of the transmitted signal and the received signal is maintained even in this composite filter 201. On the other hand, the nonlinear distortion caused by the transmit filter 13A and the nonlinear distortion caused by the transmit filter 13B cancel each other out.

[0096] Specifically, for example, a signal (e.g., a received signal) input from outside the composite filter 201 to the antenna terminal 5 is input to the first hybrid 17 and distributed to the two transmit filters 13 by the first hybrid 17. The two distributed signals are reflected by the two transmit filters 13 and input again to the first hybrid 17. The two signals input to the first hybrid 17 are combined and output to the receive filter 15 (but are not output to the antenna terminal 5).

[0097] Furthermore, for example, of the signals (e.g., transmission signals) input from the transmission terminal 7 to port 19d, the signal that passes through port 19a, transmission filter 13A, and port 17c in this order to reach port 17a and the signal that passes through port 19b, transmission filter 13B, and port 17d in this order to reach port 17a are made into in-phase signals, combined, and output to the antenna terminal 5. Of the signals input from the transmission terminal 7 to port 19d, the signal that passes through port 19a, transmission filter 13A, and port 17c in this order to reach port 17b and the signal that passes through port 19b, transmission filter 13B, and port 17d in this order to reach port 17b are opposite-phase signals to each other and are not output from port 17b.

[0098] Furthermore, for example, even if two signals are input to port 19d from the transmitting terminal 7 and nonlinear distortion occurs in each of the transmitting filters 13A and 13B, as in the previous paragraph, the signals input to ports 17c and 17d and heading toward port 17b are made to be in opposite phase and are not output from port 17b.

[0099] In the composite filter 201, the matching circuit 24 is not provided in the second section P2, nor in the first section P1. In the composite filter 201, the matching circuit 24 is provided in the section between the receiving filter 15 and the receiving terminal 9. As described above, the matching circuit 24 may have various configurations, and Fig. 4 illustrates an inductor L that connects the signal path and the reference potential section 11, as in Fig. 1 .

[0100] The matching circuit 24 between the receive filter 15 and the receive terminal 9 contributes to, for example, setting the impedance when looking toward the receive filter 15 from the receive terminal 9 (or, from another perspective, an external circuit connected to the receive terminal 9) to a reference value. Instead of or in addition to this impedance matching, the matching circuit 24 may also contribute to setting the impedance when looking toward the receive filter 15 from the port 17b of the first hybrid 17 to a reference value. Note that the matching circuit 24 between the receive filter 15 and the receive terminal 9 can also be provided between the receive terminal 9 and an external circuit connected to the receive terminal 9.

[0101] In the second embodiment, at least one of the first part P1 and the second part P2 (both in the illustrated example) does not have a matching circuit with a built-in inductor, thereby reducing insertion loss and improving pass characteristics.

[0102] 3. Third Embodiment FIG. 5 is a circuit diagram showing the configuration of a composite filter 301 according to a third embodiment.

[0103] In short, the composite filter 301 is configured by eliminating the second hybrid 19 from the composite filter 1 of the first embodiment, providing receive terminals 9A and 9B corresponding to the receive filters 15A and 15B, respectively, and further providing a 90° phase shifter 20 (hereinafter simply referred to as the "phase shifter 20") between the receive filter 15B and the receive terminal 9B. The matching circuit 24 also differs from that of the first embodiment. For ease of explanation, the first section 10A to the fifth section 10E and the first section P1 to the third section P3 refer to the same positions as in FIG. 1, with the first hybrid 17 and the receive filters 15A and 15B as reference points.

[0104] The operation related to the transmission of a transmission signal input to the transmitting terminal 7 from outside the composite filter 301 is the same as in the first embodiment. The operation related to the transmission of a reception signal input to the antenna terminal 5 from outside the composite filter 301 is the same as in the first embodiment until the signal passes through the receiving filters 15A and 15B. Thereafter, the phase of the reception signal that passes through the receiving filter 15B is shifted by 90° by the phase shifter 20. As a result, the phase of the reception signal that passes through the receiving filter 15B is shifted by 180° relative to the phase of the reception signal that passes through the receiving filter 15A, taking into account the phase shift caused by the first hybrid 17. As a result, the two reception signals are output from the two receiving terminals 9 (9A and 9B) as balanced signals that indicate the signal strengths based on the potential difference between them.

[0105] In the composite filter 301, the signal (e.g., nonlinear distortion) distributed from the transmit filter 13 to the receive filters 15A and 15B by the first hybrid 17 is finally converted into an in-phase signal by the phase shifter 20 and output to the receive terminals 9A and 9B. Therefore, in principle, the signal from the transmit filter 13 does not affect the potential difference of the balanced signal described in the previous paragraph.

[0106] At least one of the first part P1 and the second part P2 (both in the illustrated example) does not have a matching circuit with a built-in inductor, as in the first embodiment, and furthermore, in the illustrated example, does not have a matching circuit with an inductor (regardless of type). However, here, an example is shown in which the first part P1 and the second part P2 have a matching circuit 24 with a capacitor C.

[0107] The matching circuit 24 in the first section 10A contributes to, for example, bringing the impedance seen from port 17b toward the transmit filter 13 closer to a reference value. The matching circuit 24 in the second section 10B contributes to, for example, bringing the impedance seen from port 17c toward the receive filter 15A closer to a reference value. The matching circuit 24 in the third section 10C contributes to, for example, bringing the impedance seen from port 17d toward the receive filter 15B closer to a reference value.

[0108] (4. Other Embodiments) Although not particularly shown, the composite filter may have various circuit configurations other than those of the above-described embodiments.

[0109] For example, the arrangement and / or configuration of the matching circuit 24 in each of the first to third embodiments may be applied to other embodiments (or may be combined with configurations other than the matching circuit 24 in other embodiments). Specifically, the configuration in which the matching circuit 24 is not provided in either the first section P1 or the second section P2 in the second embodiment may be applied to the first or third embodiment. The configuration in which the matching circuit 24 is not provided in the second section P2 of the first section P1 and the second section P2 in the first embodiment (the matching circuit 24 is provided in the first section P1) may be applied to the second or third embodiment. The configuration in which at least one of the first section P1 and the second section P2 in the third embodiment has a matching circuit 24 having a capacitor C may be applied to the first or second embodiment.

[0110] As described above, at least one of the first part P1 and the second part P2 does not have a matching circuit 24 having a built-in inductor L. In the explanations of the first to third embodiments, an example was given in which the second part P2 does not have a matching circuit 24 having a built-in inductor L (first embodiment), and an example was given in which neither the first part P1 nor the second part P2 has a matching circuit 24 having a built-in inductor L (second and third embodiments). Unlike these examples, the first part P1 does not have to have a matching circuit 24 having a built-in inductor L (the second part P2 may have a matching circuit 24 having a built-in inductor L).

[0111] As long as at least one of the first part P1 and the second part P2 does not have a matching circuit 24 with a built-in inductor L, the presence or absence of various matching circuits 24 in the first part P1 and the second part P2 is optional. For example, the first part P1 may have four matching circuit 24 configurations: a matching circuit 24 with a built-in inductor L (hereinafter referred to as "Configuration A"); a matching circuit 24 without a built-in inductor L but with an inductor other than a built-in inductor L (hereinafter referred to as "Configuration B"); a matching circuit 24 without an inductor L (regardless of type) but with an element other than an inductor (hereinafter referred to as "Configuration C"); and no matching circuit at all (hereinafter referred to as "Configuration D"). The same applies to the second part P2. Therefore, the total number of configurations for the first part P1 and the second part P2 is 4 × 4 = 16. Of these 16 configurations, any of 15 configurations may be adopted, excluding the one configuration in which both the first part P1 and the second part P2 are Configuration A.

[0112] Some of the above 15 aspects will be selected. For example, the second part P2 may be the D aspect, and the first part P1 may be the A, B, or C aspect. The second part P2 may be the C aspect, and the first part P1 may be the A or B aspect. The second part P2 may be the B aspect, and the first part P1 may be the A aspect. In this way, the second part P2 may be configured so that the matching circuit 24, the inductor L (regardless of type) included in the matching circuit 24, or the built-in inductor L included in the matching circuit 24 is not provided in preference to the first part P1.

[0113] (5. Structural Examples of Composite Filter) The circuit configuration of the composite filter 1 described above may be realized by various structures. An example is shown below.

[0114] Fig. 6 is a schematic cross-sectional view showing an example of the structure of the composite filter 1. Because this is a schematic view, parts that are not actually located on the same cross section may be shown. For convenience, Fig. 6 includes an xyz Cartesian coordinate system. In the composite filter 1, any direction may be used as the upper side, but in the following description, for convenience, the +z side may be expressed as the upper side.

[0115] The composite filter 1 is configured as, for example, a surface-mount chip component. Its overall shape is, for example, roughly a thin rectangular parallelepiped (with the thickness being shorter than the length of the short side in a plan view) with the vertical direction as the thickness direction. A plurality of external terminals 65 are provided on the underside of the composite filter 1 for mounting the composite filter 1. The plurality of external terminals 65 include, for example, the antenna terminal 5, the transmitting terminal 7, and the receiving terminal 9 described above, as well as a GND terminal to which a reference potential is applied. The GND terminal is an example of the reference potential unit 11 described above. Although not specifically shown, the composite filter 1 is mounted on a circuit board by joining the plurality of external terminals 65 to a plurality of pads on the circuit board with a plurality of conductive bumps (e.g., solder).

[0116] The composite filter 1 includes, for example, a multilayer substrate 61 and at least one chip 63 (in the illustrated example, multiple chips) fixed to the multilayer substrate 61. Although not specifically illustrated, the composite filter 1 may include an insulating sealant (e.g., resin) or an insulating cover that covers the illustrated configuration from the +z side. The sealant or cover may or may not cover the side surface of the multilayer substrate 61.

[0117] The multilayer substrate 61 constitutes, for example, the portions of the composite filter 1 other than the transmit filter 13 and the receive filter 15. For example, the multilayer substrate 61 has the following components (some components are not shown in FIG. 6 ): an external terminal 65 (in other words, the antenna terminal 5, the transmit terminal 7, the receive terminal 9, and the reference potential section 11), a first hybrid 17, a second hybrid 19, a termination resistor 23, and a matching circuit 24. Note that some of the above components (for example, the termination resistor 23) may be provided on the chip 63. One or more chips 63 constitute, for example, the transmit filter 13 and the receive filter 15.

[0118] The multilayer substrate 61 is formed, for example, in the shape of a thin rectangular parallelepiped with its thickness extending in the vertical direction. The basic structure and materials of the multilayer substrate 61 (excluding the specific conductor patterns and dimensions for forming the composite filter 1) may be similar to the structures and materials of various known printed circuit boards. For example, the multilayer substrate 61 may be a low temperature co-fired ceramic (LTCC) substrate, a high temperature co-fired ceramic (HTCC) substrate, an integrated passive device (IPD) substrate, or an organic multilayer substrate.

[0119] An example of an LTCC substrate is one made by adding a glass-based material to alumina, which allows firing at a low temperature (for example, around 900°C). In an LTCC substrate, for example, Cu or Ag may be used as the conductive material. An example of an HTCC substrate is one made by using ceramics mainly composed of alumina or aluminum nitride. In an HTCC substrate, for example, tungsten or molybdenum may be used as the conductive material. An example of an IPD substrate is one made by forming passive elements on a Si substrate. An example of an organic multilayer substrate is one made by laminating a prepreg impregnated with resin onto a base material made of glass or the like.

[0120] The multilayer substrate 61 includes, for example, a substantially insulating plate-shaped base 67 and conductors 69 located inside and / or on the surface of the base 67. The base 67 may include, for example, a plurality of insulating layers 67a stacked on top of each other. The conductors 69 may include, for example, conductor layers 69a located on the main surfaces of the insulating layers 67a and via conductors 69b penetrating the insulating layers 67a.

[0121] The chip 63 is configured as, for example, a surface-mount chip component. Its overall shape is, for example, roughly a thin rectangular parallelepiped with its thickness extending vertically. When the transmit filter 13 and / or the receive filter 15 are acoustic wave filters, the basic structure and materials of the chip 63 (excluding the specific conductor patterns, dimensions, etc.) may be similar to the structures and materials of various known acoustic wave filter chips.

[0122] Chip 63 is disposed so as to face the upper surface of multilayer substrate 61. Chip 63 has terminals (not shown) on the surface facing multilayer substrate 61. Although not specifically designated by reference numerals, the terminals are joined to pads on the upper surface of multilayer substrate 61 with conductive bumps (e.g., solder), thereby mounting chip 63 on multilayer substrate 61.

[0123] The three filters (13 and 15) included in the composite filter 1 may be provided, for example, on separate chips 63, or may be provided on a common chip 63. Also, two filters of the same type (e.g., receive filters 15A and 15B) may be provided on a common chip 63, and another filter may be provided on another chip 63. Furthermore, part of one filter and part of another filter may be provided on a common chip 63, and another part of the one filter and another part of the other filter may be provided on another common chip 63.

[0124] The first hybrid 17 and the second hybrid 19 are, for example, built into a multilayer substrate 61, and more specifically, are built into the multilayer substrate 61. In other words, these hybrids are formed by conductors 69. Such built-in hybrids may be of a distributed parameter type or a lumped parameter type. FIG. 6 illustrates a distributed parameter type hybrid formed by two layers of coils that roughly overlap each other. Note that the elements (e.g., inductors and capacitors) that constitute a lumped parameter type hybrid may be similar to the elements described below for the elements that constitute the matching circuit 24. Unlike the illustrated example, the first hybrid 17 and / or the second hybrid 19 may be embedded in the multilayer substrate 61 or mounted on the multilayer substrate 61.

[0125] The inductor L, capacitor C, and / or resistors (not shown) that constitute the matching circuit 24 are, for example, built into the multilayer substrate 61, or more specifically, are built into the multilayer substrate 61. The specific configuration of these elements is arbitrary. For example, the inductor L may be formed by a meandering or spiral conductor pattern included in the conductor layer 69a, or may be formed by a spiral conductor formed by appropriately combining the conductor layer 69a and the via conductors 69b. The pair of electrodes of the capacitor may be formed by the same conductor layer 69a or by different conductor layers 69a. Examples of the former include a pair of strip-shaped electrodes facing each other in a planar view, and a pair of comb-shaped electrodes that interdigitate with each other in a planar view (see the comb-shaped electrodes of the acoustic wave resonator 29 described below). Examples of the latter include flat plate electrodes facing each other across the insulating layer 67a in the thickness direction. Unlike the above description, the elements that make up the matching circuit 24 may be embedded in the multi-layer substrate 61 or may be mounted on the multi-layer substrate 61 .

[0126] The composite filter 1 may be part of a module rather than a chip component as in the illustrated example. More specifically, for example, the multilayer substrate 61 may have a larger area than in the illustrated example, or may have mounted and / or built-in elements (electronic components) that do not constitute the composite filter 1. In such a case, the composite filter 1 may be connected to other elements via wiring formed by conductors 69 of the multilayer substrate 61. From another perspective, there may not be any part that clearly matches the concept of the terminals of the composite filter 1 (terminals 5, 7, and 9, as well as the GND terminal as an example of the reference potential unit 11). Examples of elements mounted on or built into the multilayer substrate 61 include an integrated circuit (IC) and an antenna.

[0127] 6. Example of the Configuration of the Transmit Filter and the Receive Filter 15 As described above, the transmit filter 13 and / or the receive filter 15 may be an elastic wave filter that uses elastic waves. An example of the configuration of an elastic wave filter will be described below.

[0128] (6.1. Examples of Acoustic Wave Element) FIG. 7 is a plan view schematically illustrating the configuration of an acoustic wave resonator 29 (hereinafter, sometimes simply referred to as "resonator 29") as an example of an acoustic wave element included in an acoustic wave filter.

[0129] Although either direction of the resonator 29 may be considered to be the up or down direction, in the following description, for convenience, an orthogonal coordinate system consisting of the D1-axis, D2-axis, and D3-axis is attached to the drawings, and the +D3 side (the side facing the page) is considered to be the up direction, and terms such as the top surface or the bottom surface may be used. The D1-axis is defined to be parallel to the propagation direction of an elastic wave propagating along the top surface of the piezoelectric body (described later), the D2-axis is defined to be parallel to the top surface of the piezoelectric body and perpendicular to the D1-axis, and the D3-axis is defined to be perpendicular to the top surface of the piezoelectric body.

[0130] The resonator 29 is configured as a so-called one-port acoustic wave resonator. The resonator 29 receives a signal from one of two terminals 28, which are shown schematically on both sides of the drawing, and outputs the signal from the other of the two terminals 28. In this case, the resonator 29 converts the electrical signal into an acoustic wave and the acoustic wave into an electrical signal. As will be understood from the description of FIG. 8 , which will be described later, the terminal 28 may correspond to, for example, any of the antenna terminal 5, the transmitting terminal 7, the receiving terminal 9, and the reference potential unit 11.

[0131] The resonator 29 includes, for example, a piezoelectric substrate 31 (at least a part of its upper surface 31a), an excitation electrode 33 located on the upper surface 31a, and a pair of reflectors 35 located on both sides of the excitation electrode 33. Note that a configuration in which the pair of reflectors 35 are removed from the resonator 29 (one-port resonator) is also a type of resonator.

[0132] A plurality of resonators 29 may be formed on one piezoelectric substrate 31. That is, the piezoelectric substrate 31 may be shared by a plurality of resonators 29. In the following description, in order to distinguish between a plurality of resonators 29 sharing the same piezoelectric substrate 31, the combination of an excitation electrode 33 and a pair of reflectors 35 (electrode portions of the resonator 29) may be expressed as if it were the resonator 29 (as if the resonator 29 does not include the piezoelectric substrate 31).

[0133] The piezoelectric substrate 31 has piezoelectricity at least in the region of its upper surface 31a where the resonator 29 is provided. Examples of such piezoelectric substrates 31 include those in which the entire substrate is made of a piezoelectric material. Examples of other types of piezoelectric substrates include so-called bonded substrates. A bonded substrate includes a substrate (piezoelectric substrate) made of a piezoelectric material having an upper surface 31a, and a support substrate bonded to the surface opposite the upper surface 31a of the piezoelectric substrate, with or without an adhesive. The support substrate may have a recess on its upper surface to form a cavity overlapping at least a portion of the resonator 29 in a planar perspective view, or it may not have such a recess. Examples of other types of piezoelectric substrates 31 include those in which a film made of a piezoelectric material (piezoelectric film) or multiple films including a piezoelectric film are formed on a partial region of the main surface on the +D3 side of the support substrate or on the entire main surface.

[0134] The piezoelectric body 31b, which constitutes at least the region of the piezoelectric substrate 31 where the resonator 29 is provided, is made of, for example, a single crystal having piezoelectricity. Examples of materials that constitute such single crystal include lithium tantalate (LiTaO ３ ), lithium niobate (LiNbO ３ ) and quartz (SiO ２ The cut angle, planar shape and various dimensions may be set appropriately.

[0135] The excitation electrode 33 and the reflector 35 are composed of layered conductors provided on the piezoelectric substrate 31. The excitation electrode 33 and the reflector 35 are composed of, for example, the same material and thickness. The layered conductors that compose them are, for example, metal. The metal is, for example, Al or an alloy containing Al as a main component (Al alloy). The Al alloy is, for example, an Al-Cu alloy. The layered conductor may be composed of multiple metal layers. The thickness of the layered conductor is set appropriately depending on the electrical characteristics required of the resonator 29, etc. As an example, the thickness of the layered conductor is 50 nm to 600 nm.

[0136] The excitation electrode 33 is configured by a so-called IDT (Interdigital Transducer) electrode and has a pair of comb-tooth electrodes 37 (one of which is hatched for ease of visibility). Each comb-tooth electrode 37 has, for example, a bus bar 39, a plurality of electrode fingers 41 extending in parallel from the bus bar 39, and a plurality of dummy electrodes 43 protruding from the bus bar 39 between the plurality of electrode fingers 41. The pair of comb-tooth electrodes 37 is arranged so that the plurality of electrode fingers 41 interdigitate with (intersect with) each other.

[0137] The bus bars 39 are formed, for example, in elongated shapes that have a substantially constant width and extend linearly in the propagation direction of the elastic waves (direction D1). The pair of bus bars 39 face each other in a direction (direction D2) perpendicular to the propagation direction of the elastic waves. Note that the width of the bus bars 39 may vary or they may be inclined with respect to the propagation direction of the elastic waves.

[0138] Each electrode finger 41 is formed, for example, in an elongated shape extending linearly in a direction (direction D2) perpendicular to the propagation direction of the elastic wave with a substantially constant width. Note that the width of the electrode fingers 41 may vary. In each comb-tooth electrode 37, the multiple electrode fingers 41 are arranged in the propagation direction of the elastic wave. Furthermore, the multiple electrode fingers 41 of one comb-tooth electrode 37 and the multiple electrode fingers 41 of the other comb-tooth electrode 37 are basically arranged alternately.

[0139] The pitch p of the electrode fingers 41 (e.g., the distance between the centers of two adjacent electrode fingers 41) is basically constant within the excitation electrode 33. The excitation electrode 33 may have a portion that is unique in terms of the pitch p. Examples of unique portions include a narrow pitch portion where the pitch p is narrower than the majority (e.g., 80% or more), a wide pitch portion where the pitch p is wider than the majority, and a thinned-out portion where a small number of electrode fingers 41 are essentially thinned out.

[0140] In the following, unless otherwise specified, the pitch p refers to the pitch of the portion excluding the above-described unique portion (the majority of the plurality of electrode fingers 41). Furthermore, if the pitch varies even in most of the plurality of electrode fingers 41 excluding the unique portion, the average value of the pitches of most of the plurality of electrode fingers 41 may be used as the value of the pitch p.

[0141] The number of electrode fingers 41 may be set appropriately depending on the electrical characteristics required of the resonator 29. Since Fig. 7 is a schematic diagram, the number of electrode fingers 41 is shown as being smaller than that shown. In reality, more electrode fingers 41 may be arranged than shown. The same applies to the strip electrode 47 of the reflector 35, which will be described later.

[0142] The lengths of the electrode fingers 41 are, for example, equal to each other. The excitation electrode 33 may be apodized, in which the lengths of the electrode fingers 41 (or, from another perspective, the cross width W) vary depending on the position in the propagation direction. The length and width of the electrode fingers 41 may be set appropriately depending on the required electrical characteristics, etc.

[0143] The dummy electrode 43 protrudes, for example, with a generally constant width in a direction perpendicular to the propagation direction of the elastic wave. The width is, for example, equal to the width of the electrode fingers 41. The multiple dummy electrodes 43 are arranged at the same pitch as the multiple electrode fingers 41, and the tips of the dummy electrodes 43 of one comb-tooth electrode 37 face the tips of the electrode fingers 41 of the other comb-tooth electrode 37 across a gap. Note that the excitation electrode 33 may not include the dummy electrodes 43.

[0144] The pair of reflectors 35 are located on both sides of the excitation electrode 33 in the propagation direction of the elastic wave. Each reflector 35 may be, for example, electrically floating or may be applied with a reference potential. Each reflector 35 is formed, for example, in a lattice shape. That is, the reflector 35 includes a pair of bus bars 45 facing each other and a plurality of strip electrodes 47 extending between the pair of bus bars 45. The pitch of the plurality of strip electrodes 47 and the pitch between the adjacent electrode fingers 41 and strip electrodes 47 are basically the same as the pitch of the plurality of electrode fingers 41.

[0145] When a voltage is applied to the pair of comb-tooth electrodes 37, the voltage is applied to the piezoelectric body 31 b by the multiple electrode fingers 41, causing the piezoelectric body 31 b to vibrate. That is, an elastic wave is excited. Of the elastic waves of various wavelengths that propagate in various directions, the elastic waves that propagate in the arrangement direction of the multiple electrode fingers 41 with the pitch p of the multiple electrode fingers 41 being approximately half the wavelength (λ / 2) tend to have large amplitudes because the multiple waves excited by the multiple electrode fingers 41 overlap in phase.

[0146] Furthermore, the elastic waves propagating through the piezoelectric body 31b are converted into electrical signals by the plurality of electrode fingers 41. At this time, similar to when elastic waves are excited, the intensity of the electrical signals converted from the elastic waves propagating in the arrangement direction of the plurality of electrode fingers 41, with the pitch p of the plurality of electrode fingers 41 being approximately half the wavelength (λ / 2), tends to be strong.

[0147] Due to the above-described effects (and other effects not described here), the resonator 29 functions as a resonator having a resonance frequency equal to the frequency of an elastic wave whose pitch p is approximately half the wavelength (λ / 2). The pair of reflectors 35 contributes to confining the elastic wave.

[0148] Although the above example uses an elastic wave propagating in the arrangement direction of the multiple electrode fingers 41, the elastic wave may also propagate in the thickness direction of the piezoelectric body 31b. For example, a thickness shear wave may be used in which the piezoelectric body 31b vibrates so that the upper and lower surfaces slide relative to each other. In this embodiment, a cavity may be provided between the lower surface of the piezoelectric body 31b and the support substrate that supports the piezoelectric body 31b. The wavelength is highly dependent on the thickness of the piezoelectric body 31b and less dependent on the pitch p. The reflector 35 may be omitted.

[0149] Although not shown in particular, the resonator 29 may have a protective film (not shown) that covers the upper surface 31a of the piezoelectric substrate 31 from above the excitation electrode 33 and the reflector 35. Such a protective film may be made of, for example, SiO ２The additional film is made of an insulating material such as copper or nickel, and contributes to reducing the likelihood of corrosion of the excitation electrode 33 and other components and / or compensating for changes in characteristics of the resonator 29 due to temperature changes. The resonator 29 may also have an additional film that overlaps the upper or lower surfaces of the excitation electrode 33 and the reflector 35 and has a shape that basically fits within the excitation electrode 33 and the reflector 35 in a planar perspective view. Such an additional film is made of, for example, an insulating material or a metal material that has acoustic properties different from those of the material of the excitation electrode 33 and other components, and contributes to improving the reflection coefficient of elastic waves.

[0150] The chip 63 shown in FIG. 6 may be primarily composed of, for example, a piezoelectric substrate 31. For example, the chip 63 may be a bare chip essentially consisting of only the configuration described with reference to FIG. 7 . The +D3 side of the piezoelectric substrate 31 may be positioned opposite the top surface of the multilayer substrate 61, and layer-like terminals (not shown) located on the top surface of the piezoelectric substrate 31 may be bonded to pads located on the top surface of the multilayer substrate 61 by bumps. Alternatively, for example, the chip 63 may be a WLP (Wafer Level Package) type having a cover (not shown) covering the +D3 side of the piezoelectric substrate 31. The top surface (the +D3 side) of the cover may be positioned opposite the top surface of the multilayer substrate 61, and post-shaped terminals (not shown) penetrating the cover may be bonded to pads located on the top surface of the multilayer substrate 61 by bumps. Alternatively, for example, the chip 63 may be a FO (Fan Out)-WLP type having a molded portion covering the side surfaces of the bare chip.

[0151] 8 is a circuit diagram showing a schematic configuration of the duplexer main body 3 (a portion including the transmit filter 13 and receive filter 15, which directly contributes to filtering). In this diagram, only the duplexer main body 3 and terminals of the composite filter 1 are shown. In other words, the first hybrid 17, the second hybrid 19, and the like are not shown. Also, only one of the receive filters 15A and 15B is shown.

[0152] As can be seen from the symbols in the upper left corner of this figure, the comb electrode 37 is shown schematically as a two-pronged fork, and the reflector 35 is represented by a single line bent at both ends. In the following description, the term "branching filter main body 3" may be replaced with the term "composite filter 1" unless a contradiction arises.

[0153] As described above, the duplexer main body 3 has an antenna terminal 5, a transmission terminal 7, a reception terminal 9, a reference potential unit 11, a transmission filter 13, and a reception filter 15. The antenna terminal 5 and the filters (13 and 15) are connected via a first hybrid 17. For convenience, in Fig. 8, the first hybrid 17 is omitted and the connection between the antenna terminal 5 and the filter is shown by a dotted line. The reception terminal 9 and the reception filter 15 are connected via a second hybrid 19. For convenience, in the following explanation, the connection relationship may be described as if the hybrids (17 and 19) were not provided.

[0154] The transmit filter 13 is configured, for example, as a ladder filter in which a plurality of resonators 29 (29S and 29P) are connected in a ladder configuration. That is, the transmit filter 13 has a plurality of series resonators 29S (one resonator is sufficient) connected in series between the transmit terminal 7 and the antenna terminal 5, and a plurality of parallel resonators 29P (one parallel resonator is sufficient) connecting the series line (series arm) to the reference potential unit 11.

[0155] The receiving filter 15 is configured to include, for example, a resonator 29 and a multimode filter 49 (which includes a double-mode filter; hereinafter, this may be referred to as an MM filter 49). The MM filter 49 has a plurality of excitation electrodes 33 (three in the illustrated example) arranged in the propagation direction of the elastic wave, and a pair of reflectors 35 arranged on both sides of the excitation electrodes 33.

[0156] The above-described configurations of the transmit filter 13 and receive filter 15 are merely examples and may be modified as appropriate. For example, the receive filter 15 may be configured with a ladder filter like the transmit filter 13, or conversely, the transmit filter 13 may include an MM filter 49.

[0157] 7. Example of a Communication Device Including a Composite Filter The composite filter may be used, for example, in a communication module and / or a communication device.

[0158] 9 is a block diagram showing the main parts of a communication device 151 as an example of using the composite filter 1. The communication device 151 has a module 171 and a housing 173 that houses the module 171. The module 171 performs wireless communication using radio waves and includes the composite filter 1. Here, only the transmit filter system 12 and the receive filter system 14 of the composite filter 1 are shown, and hybrids and other components are not shown.

[0159] In module 171, a transmission information signal TIS containing information to be transmitted is modulated and frequency-raised (converted into a high-frequency signal having a carrier frequency) by an RF-IC (Radio Frequency Integrated Circuit) 153 to generate a transmission signal TS. Unwanted components outside the transmission passband are removed from the transmission signal TS by a bandpass filter 155, amplified by an amplifier 157, and input to a composite filter 1 (transmission terminal 7). The composite filter 1 (transmission filter system 12) then removes unwanted components outside the transmission passband from the input transmission signal TS, and outputs the removed transmission signal TS from antenna terminal 5 to an antenna 159. The antenna 159 converts the input electrical signal (transmission signal TS) into a radio signal (radio wave) and transmits it.

[0160] Furthermore, in module 171, a radio signal (radio wave) received by antenna 159 is converted by antenna 159 into an electrical signal (received signal RS) and input to composite filter 1 (antenna terminal 5). Composite filter 1 (receive filter system 14) removes unnecessary components outside the receive passband from the input received signal RS and outputs the signal from receive terminal 9 to amplifier 161. The output received signal RS is amplified by amplifier 161, and unnecessary components outside the receive passband are removed by bandpass filter 163. The received signal RS is then frequency-downshifted and demodulated by RF-IC 153 to generate received information signal RIS.

[0161] The transmit information signal TIS and the receive information signal RIS may be low-frequency signals (baseband signals) containing appropriate information, such as analog audio signals or digitized audio signals. The passband of the radio signal may be set as appropriate. The modulation method may be phase modulation, amplitude modulation, frequency modulation, or a combination of two or more of these. Although the direct conversion method is illustrated, other appropriate circuit methods may be used, such as a double superheterodyne method. Furthermore, FIG. 9 is a schematic diagram illustrating only the essential parts; low-pass filters, isolators, etc. may be added at appropriate positions, and the positions of amplifiers, etc. may be changed.

[0162] The module 171 has, for example, components from the RF-IC 153 to the antenna 159 on the same circuit board. That is, the composite filter 1 is combined with other components to form a module. The circuit board may be the multilayer board 61, or may be a board on which the multilayer board 61 (composite filter 1) is mounted. The composite filter 1 may be included in the communication device 151 without being modularized. Furthermore, the components exemplified as components of the module 171 may be located outside the module or may not be housed in the housing 173. For example, the antenna 159 may be exposed to the outside of the housing 173.

[0163] (8. Summary of the Embodiments) As described above, the composite filter 1 (or 201 or 301) includes the first hybrid 17, a first filter (e.g., the transmit filter 13 in the first embodiment), and second and third filters (e.g., the receive filters 15A and 15B in the first embodiment). The first hybrid 17 is configured as a 90° hybrid coupler having first and second ports (ports 17a and 17b) and third and fourth ports (ports 17c and 17d) to which a signal input to port 17a or port 17b is distributed. The first filter is connected to port 17b and has a first passband (e.g., the transmit band in the first embodiment). The second filter is connected to port 17c and has a second passband (e.g., the receive band in the first embodiment) that does not overlap with the first passband. The third filter is connected to port 17d and has a second passband. The electrical section (first section 10A) from the first filter to the first hybrid 17 will be referred to as the first section P1. The combination of the electrical section (second section 10B) from the second filter to the first hybrid 17 and the electrical section (third section 10C) from the third filter to the first hybrid 17 will be referred to as the second section P2. In this case, at least one of the first section P1 and the second section P2 does not have a matching circuit having an inductor formed by a conductor of a multilayer substrate (in other words, a built-in inductor).

[0164] Therefore, as mentioned above, the likelihood of insertion loss caused by an inductor with a low Q value is reduced, and pass characteristics can be improved. Note that the "multilayer substrate" in the "inductor constructed from the conductors of a multilayer substrate" in the previous paragraph does not refer to a specific multilayer substrate (e.g., the multilayer substrate 61), but refers to multilayer substrates in general. In other words, the presence of the multilayer substrate 61 in the composite filter 1 is not a prerequisite for the configuration described in the previous paragraph.

[0165] At least one of the first part P1 and the second part P2 does not need to have a matching circuit including the inductor L (whether it is a built-in type or not).

[0166] In this case, for example, even if a chip inductor (mounted type or embedded type) with a relatively high Q value is not provided, the likelihood of insertion loss occurring can be further reduced and the transmission characteristics can be improved.

[0167] The second section P2 does not need to have a matching circuit.

[0168] In this case, for example, by not providing any matching circuit in the second section P2, the likelihood of insertion loss can be further reduced and the pass characteristics can be improved. Furthermore, as described with reference to Figures 2 and 3, the matching circuit in the second section P2 affects the reflection characteristics when a signal in the first pass band (e.g., the transmission signal in the first embodiment) is input to the second and third filters (e.g., the receive filters 15A and 15B) having the second pass band. This not only reduces the insertion loss simply due to the presence of the matching circuit 24, but also reduces the insertion loss due to the deterioration of the reflection characteristics. Furthermore, while the signal in the first pass band passes through the first section P1 only once, from the first filter (e.g., the transmit filter 13 in the first embodiment) to the first hybrid 17, the signal passes through the second section P2 twice: once when it travels from the first hybrid 17 to the second and third filters, and once when it is reflected by the second and third filters and travels to the first hybrid 17. For the above reasons, the matching circuit 24 in the second section P2 has a greater effect on the degradation of the pass characteristics than the matching circuit 24 in the first section P1. By not providing the matching circuit 24 in the second section P2, the effect of improving the pass characteristics by not providing the matching circuit 24 is enhanced.

[0169] In addition to the second part P2 not having a matching circuit of any kind, the first part P1 may not have a matching circuit of any kind (see FIG. 4).

[0170] In this case, for example, the matching circuits 24 are not provided between any of the three filters and the first hybrid 17, so the effect of improving the pass characteristics by not providing the matching circuits 24 is further enhanced.

[0171] At least one of the first section P1 and the second section P2 may include a matching circuit 24 having a capacitor C (see FIG. 5).

[0172] In this case, for example, by using a capacitor C that easily passes high frequency components, it is possible to reduce insertion loss and achieve impedance matching.

[0173] The composite filter 1 may have a matching circuit 24 connected to a second filter (e.g., the receive filter 15A in the first embodiment) on the electrically opposite side of the side where the first hybrid 17 is connected, and a matching circuit 24 connected to a third filter (e.g., the receive filter 15B in the first embodiment) on the electrically opposite side of the side where the first hybrid 17 is connected.

[0174] In this case, for example, as described above, the effect of improving the pass characteristics can be obtained by not providing a matching circuit 24 in at least one of the first part P1 and the second part P2 (particularly the second part P2), while the matching circuit 24 in the third part P3 can be used to match impedance, thereby further improving the pass characteristics.

[0175] The composite filter 1 may have a common terminal (antenna terminal 5), a first terminal (e.g., the transmit terminal 7 in the first embodiment), a second hybrid 19, a second terminal (e.g., the receive terminal 9 in the first embodiment), and a termination resistor 23. The antenna terminal 5 may be connected to a first port (port 17a). The first terminal may be connected to a first filter (e.g., the transmit filter 13 in the first embodiment) on the electrically opposite side of the side where the first hybrid 17 is connected. The second hybrid 19 may be configured as a 90° hybrid coupler having fifth to eighth ports (ports 19a to 19d). The port 19a may be connected to a second filter (e.g., the receive filter 15A in the first embodiment) on the electrically opposite side of the side where the first hybrid 17 is connected. The port 19b may be connected to a third filter (e.g., the receive filter 15B in the first embodiment) on the electrically opposite side of the side where the first hybrid 17 is connected. Ports 19c and 19d distribute signals from port 19a or 19b. The second terminal may be connected to one of ports 19c and 19d (port 19d in FIG. 1 etc.) where signals passing through ports 17a, 17c, and 19a in this order and signals passing through ports 17a, 17d, and 19b in this order are in phase with each other. Termination resistor 23 may be connected to the other of ports 19c and 19d.

[0176] In this case, for example, as described above, nonlinear distortion can be reduced. Note that the previous paragraph merely states that a signal input to port 19a or 19b is distributed to ports 19c and 19d as a means of explaining the relationship between the fifth to eighth ports (ports 19a to 19d), and in reality, the intended signal does not necessarily have to be input to port 19a or 19b (see FIG. 4). Similarly, the previous paragraph merely states that a signal input to the first port (port 17a) becomes in-phase at port 19d as a means of explaining the relationship between the fifth to eighth ports (ports 19a to 19d), and in reality, the intended signal does not necessarily have to reach port 19d from port 17a (see FIG. 4).

[0177] The composite filter 1 may include a first substrate (multilayer substrate 61) that is configured as a multilayer substrate, and a chip 63 that includes at least one acoustic wave filter and is mounted on the multilayer substrate 61. The at least one acoustic wave filter may include at least a part of the first filter, the second filter, and the third filter (e.g., the transmit filter 13 and the receive filters 15A and 15B in the first embodiment).

[0178] In this case, for example, the hybrid can reduce nonlinear distortion occurring in the acoustic wave filter. By incorporating or mounting the hybrid in the multilayer substrate 61, the composite filter 1 can be realized in a compact configuration in which the acoustic wave filter chip 63 is mounted on the multilayer substrate 61. Unlike the embodiment, further miniaturization can be achieved by incorporating the inductor L of the matching circuit 24 of the first section P1 and the second section P2 into the multilayer substrate 61. However, by deliberately avoiding such a configuration, the pass characteristics can be improved.

[0179] From another perspective, the composite filter 301 includes a first hybrid 17, a first filter (e.g., transmit filter 13), a second filter (e.g., receive filter 15A), and a third filter (e.g., receive filter 15B). The first hybrid 17 is configured as a 90° hybrid coupler having first and second ports (ports 17a and 17b) and third and fourth ports (ports 17c and 17d) to which a signal (e.g., a transmit signal) input to port 17a or 17b is distributed. The first filter is connected to port 17b and has a first passband (e.g., transmit band). The second filter is connected to port 17c and has a second passband (e.g., receive band) that does not overlap with the first passband. The third filter is connected to port 17d and has a second passband. The electrical section (first section 10A) from the first filter to the first hybrid 17 is referred to as a first section P1. The combination of the electrical section (second section 10B) from the second filter to the first hybrid 17 and the electrical section (third section 10C) from the third filter to the first hybrid 17 is referred to as a second section P2. In this case, at least one of the first section P1 and the second section P2 has a matching circuit 24 having a capacitor C.

[0180] In this case, for example, by using a capacitor C that easily passes high frequency components, it is possible to reduce insertion loss and achieve impedance matching. Note that although the symbols used in the third embodiment are used in the previous paragraph, as already mentioned, the above configuration may be applied to other embodiments.

[0181] The communication device 151 may also include a composite filter 1 (or 201 or 301), an antenna 159 connected to the first port (port 17a), and an integrated circuit element (RF-IC 153) connected to the electrically opposite side of the first hybrid 17 of each of the first filter, second filter, and third filter.

[0182] In this case, for example, the communication device 151 can utilize the effect of improving the pass characteristics of the composite filter 1. As a result, the communication characteristics are improved.

[0183] In the above embodiments, the antenna terminal 5 is an example of a common terminal. In the first and third embodiments, the transmit filter 13 is an example of a first filter, the receive filters 15A and 15B are examples of a second filter and a third filter, respectively, the transmit terminal 7 is an example of a first terminal, and the receive terminal 9 is an example of a second terminal. In the second embodiment, the receive filter 15 is an example of a first filter, the transmit filters 13A and 13B are examples of a second filter and a third filter, respectively, the receive terminal 9 is an example of a first terminal, and the transmit terminal 7 is an example of a second terminal. The multilayer substrate 61 is an example of a first substrate. The ports 17a to 17d and 19a to 19d are examples of first to eighth ports, respectively. The RF-IC 153 is an example of an integrated circuit element.

[0184] The technology according to the present disclosure is not limited to the above-described embodiment and may be implemented in various modes.

[0185] For example, the composite filter 1 may have only the second and third filters from the third section P3 of the composite filter 1, 201, or 301. The configuration on the right side of the third section P3 in Figures 1, 4, and 5 may be external to the composite filter 1.

[0186] The composite filter 1 may be part of a multiplexer such as a triplexer or a quadplexer. The composite filter 1 is not limited to a duplexer, and may be a diplexer (multiplexer) that filters two types of transmission signals or two types of reception signals having different frequencies (frequency bands).

[0187] The composite filter does not have to have a multilayer substrate, for example, the composite filter may be configured by mounting a filter or hybrid on a single-sided or double-sided substrate.

[0188] 1, 201, 301...composite filters, 13, 13A, 13B...transmitting filters (first filter, second filter or third filter), 15, 15A, 15B...receiving filters (first filter, second filter or third filter), 17...first hybrid, 17a...first port, 17b...second port, 17c...third port, 17d...fourth port.

Claims

1. a first hybrid configured by a 90° hybrid coupler having a first port and a second port, and a third port and a fourth port to which a signal input to the first port or the second port is distributed; a first filter connected to the second port and having a first passband; a second filter connected to the third port, the second filter having a second passband that does not overlap with the first passband; a third filter connected to the fourth port and having the second passband; It has an electrical section extending from the first filter to the first hybrid is defined as a first section; When a combination of an electrical section from the second filter to the first hybrid and an electrical section from the third filter to the first hybrid is defined as a second part, At least one of the first section and the second section does not have a matching circuit having an inductor formed by a conductor of a multilayer substrate. Compound filters.

2. At least one of the first section and the second section does not have a matching circuit having an inductor.

2. The composite filter of claim 1.

3. The second part does not have a matching circuit.

3. The composite filter of claim 2.

4. The first part does not have a matching circuit.

4. The composite filter of claim 3.

5. At least one of the first section and the second section has a matching circuit having a capacitor.

2. The composite filter of claim 1.

6. a matching circuit connected to the second filter on an electrically opposite side to a side to which the first hybrid is connected; a matching circuit connected to the third filter on an electrically opposite side to a side to which the first hybrid is connected, 2. The composite filter of claim 1.

7. a common terminal connected to the first port; a first terminal connected to the first filter on an electrically opposite side to a side to which the first hybrid is connected; a second hybrid configured by a 90° hybrid coupler having a fifth port connected to the second filter on the electrically opposite side to the side to which the first hybrid is connected, a sixth port connected to the third filter on the electrically opposite side to the side to which the first hybrid is connected, and a seventh port and an eighth port to which a signal from the fifth port or the sixth port is distributed; a second terminal connected to one of the seventh port and the eighth port, where a signal passing through the first port, the third port, and the fifth port in this order and a signal passing through the first port, the fourth port, and the sixth port in this order are in phase with each other; a termination resistor connected to the other of the seventh port and the eighth port; It has 2. The composite filter of claim 1.

8. A first substrate formed of a multi-layer substrate; a chip mounted on the first substrate and including at least one acoustic wave filter; It has the at least one acoustic wave filter includes at least a portion of the first filter, the second filter, and the third filter; 2. The composite filter of claim 1.

9. a first hybrid configured by a 90° hybrid coupler having a first port and a second port, and a third port and a fourth port to which a signal input to the first port or the second port is distributed; a first filter connected to the second port and having a first passband; a second filter connected to the third port, the second filter having a second passband that does not overlap with the first passband; a third filter connected to the fourth port and having the second passband; It has an electrical section extending from the first filter to the first hybrid is defined as a first section; When a combination of an electrical section from the second filter to the first hybrid and an electrical section from the third filter to the first hybrid is defined as a second part, At least one of the first section and the second section has a matching circuit having a capacitor. Compound filters.

10. A composite filter according to any one of claims 1 to 9; an antenna connected to the first port; an integrated circuit element connected to each of the first filter, the second filter, and the third filter on an electrically opposite side to the first hybrid, Communications equipment.