Multiplexer and communication device

Abstract

A multiplexer (1) includes filters (11-13) and low-pass filters (14 and 15), a second frequency band and a third frequency band are at least partially different, a first frequency band does not overlap with the second and third frequency bands, one end of the filter (11) is connected to a common terminal (100), the other end is connected to an input / output terminal (110), one end of the low-pass filter (14) is connected to the common terminal (100), the other end is connected to one end of the filter (12), the other end of the filter (12) is connected to one end of the low-pass filter (15), the other end of the low-pass filter (15) is connected to an input / output terminal (120), one end of the filter (13) is connected to a connection node (n1) of the other end of the low-pass filter (14) and one end of the filter (12), the other end of the filter (13) is connected to an input / output terminal (130).

Description

Technical Field

[0001] This invention relates to multiplexers and communication devices. Background Technology

[0002] In mobile communication devices such as mobile phones, multiplexers that are positioned directly below the antenna are required to be small and have low loss.

[0003] Patent Document 1 discloses a multiplexer having a first circuit consisting of a low-pass filter (LPF) and a high-pass filter (HPF) and a second circuit consisting of a band-pass filter (BPF) and a band-stop filter (BEF) connected in common with the HPF.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2018-170755

[0005] In Patent Document 1, the HPF of the first circuit has the function of attenuating the passband of the LPF. The HPF ensures isolation between the signal passing through the HPF and the signal passing through the LPF.

[0006] Here, because the passband attenuation function of the BEF in the second circuit is relatively low, the HPF is required on the signal path where the BEF is configured. On the other hand, the passband attenuation function of the BPF in the second circuit is higher than that of the BEF. Therefore, if the HPF is configured on the signal path where the BPF is configured, the passband attenuation function of the LPF becomes excessive (overkill). As a result, the transmission loss in the signal path deteriorates because the HPF is configured on the signal path where the BPF is configured. That is, the following problem occurs: between the two filters (BPF and BEF in Patent Document 1) that are connected to the HPF (or LPF), the transmission loss of the signal path with one of the two filters configured deteriorates due to the difference in the required attenuation amount of the LPF (or HPF) passband. Summary of the Invention

[0007] Therefore, the object of the present invention is to provide a multiplexer and communication device that achieves low loss and high isolation.

[0008] To achieve the above objectives, a multiplexer according to one embodiment of the present invention includes: a common terminal, a first input / output terminal, a second input / output terminal, and a third input / output terminal; a first filter that uses a first frequency band as a passband; a second filter that uses a second frequency band as a passband and a third frequency band as an attenuation band; a third filter that uses the third frequency band as a passband and the first and second frequency bands as attenuation bands; a fourth filter that uses the second and third frequency bands as passbands and the first frequency band as an attenuation band; and a fifth filter that uses the second and third frequency bands as passbands and the first frequency band as an attenuation band, wherein the frequencies of the second and third frequency bands are at least partially... Unlike other filters, the frequencies of the first frequency band do not overlap with the frequencies of the second and third frequency bands. One end of the first filter is connected to the common terminal, and the other end of the first filter is connected to the first input / output terminal. One end of the fourth filter is connected to the common terminal, and the other end of the fourth filter is connected to one end of the second filter. The other end of the second filter is connected to one end of the fifth filter, and the other end of the fifth filter is connected to the second input / output terminal. One end of the third filter is connected to the connection node between the other end of the fourth filter and the first end of the second filter, and the other end of the third filter is connected to the third input / output terminal.

[0009] According to the present invention, it is possible to provide multiplexers and communication devices that achieve low loss and high isolation. Attached Figure Description

[0010] Figure 1A This is a circuit block diagram of the multiplexer and communication device in Embodiment 1.

[0011] Figure 1B This is the circuit structure diagram of the multiplexer in Example 1.

[0012] Figure 1C This is a schematic diagram showing the pass characteristics of each filter in the multiplexer of Embodiment 1.

[0013] Figure 2A This is the circuit block diagram of the multiplexer in Comparative Example 1.

[0014] Figure 2B This is the circuit diagram of the multiplexer in Comparative Example 1.

[0015] Figure 3A This is the circuit diagram of the multiplexer in variation example 1.

[0016] Figure 3B This is a schematic diagram showing the pass characteristics of each filter in the multiplexer of Modified Example 1.

[0017] Figure 4A This is the circuit block diagram of the multiplexer in variation example 2.

[0018] Figure 4B This is a schematic diagram showing the pass characteristics of each filter in the multiplexer of Modified Example 2.

[0019] Figure 5A This is a circuit block diagram of the multiplexer in Implementation Method 2.

[0020] Figure 5B This is the circuit structure diagram of the multiplexer in Embodiment 2.

[0021] Figure 5C This is a schematic diagram showing the pass characteristics of each filter in the multiplexer of Embodiment 2.

[0022] Figure 6A This is the circuit block diagram of the multiplexer in variation example 3.

[0023] Figure 6B This is the circuit diagram of the multiplexer in variation example 3.

[0024] Figure 6C This is a schematic diagram showing the pass characteristics of each filter in the multiplexer of Modified Example 3.

[0025] Figure 7 This is the circuit diagram of the multiplexer in Comparative Example 2.

[0026] Figure 8 This is a graph comparing the throughput characteristics of the third signal path in Modified Example 3 and Comparative Example 2.

[0027] Figure 9 This is the circuit block diagram of the multiplexer in variation example 4.

[0028] Figure 10 This is a circuit block diagram of the multiplexer in Implementation Method 3.

[0029] Figure 11 This is the circuit block diagram of the multiplexer in Comparative Example 3.

[0030] Figure 12 This is the circuit block diagram of the multiplexer in variation example 5.

[0031] Figure 13 This is the circuit block diagram of the multiplexer in variation example 6.

[0032] Figure 14 This is the circuit block diagram of the multiplexer in variation example 7.

[0033] Figure 15 This is the circuit block diagram of the multiplexer in variation example 8.

[0034] Figure 16 This is a diagram showing the first example of the circuit structure of the multiplexer in variation 8.

[0035] Figure 17 This is a diagram of the second example of the circuit structure of the multiplexer in Modified Example 8. Detailed Implementation

[0036] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Furthermore, the embodiments, examples, and modifications described below are general or specific examples. The numerical values, shapes, materials, constituent elements, arrangements of constituent elements, and connection methods shown in the following embodiments, examples, and modifications are merely examples and do not limit the scope of the present invention. Constituent elements in the following embodiments, examples, and modifications that are not described in the independent claims are described as arbitrary constituent elements. Additionally, the sizes or size ratios of the constituent elements shown in the drawings are not necessarily strict.

[0037] In addition, the term "signal path" as used below refers to a transmission line consisting of wiring that transmits high-frequency signals, electrodes directly connected to the wiring, and terminals directly connected to the wiring or electrodes.

[0038] (Implementation Method 1)

[0039] [1.1 Structure of Multiplexer 1 and Communication Device 90]

[0040] Figure 1A This is a circuit block diagram of the multiplexer 1 and the communication device 90 in Embodiment 1. Figure 1A As shown, the communication device 90 includes a multiplexer 1, an antenna 92, and an RF signal processing circuit (RFIC) 91.

[0041] RFIC 91 is an example of an RF signal processing circuit that processes high-frequency signals transmitted and received by antenna 92. Specifically, RFIC 91 processes the received signal input via multiplexer 1 through down-conversion or the like, and outputs the received signal generated by this signal processing to a baseband signal processing circuit (BBIC: not shown). In addition, RFIC 91 outputs a transmit signal to multiplexer 1 based on the signal processed from the BBIC.

[0042] Antenna 92 ​​is connected to the common terminal 100 of multiplexer 1, radiates high-frequency signals output from multiplexer 1, and receives high-frequency signals from the outside and outputs them to multiplexer 1.

[0043] Furthermore, amplifiers, switches, and filters can be appropriately configured on the signal path connecting multiplexer 1 and RFIC 91, depending on the number and frequency band of signals transmitted in that signal path.

[0044] Multiplexer 1 is configured between antenna 92 ​​and RFIC 91 to perform waveform splitting on the received signal input from antenna 92 ​​and multiplexing on the transmitted signal input from RFIC 91.

[0045] [1.2 Structure of Multiplexer 1 in Embodiment 1]

[0046] Next, the detailed structure of multiplexer 1 will be described. For example... Figure 1A As shown, the multiplexer 1 includes a common terminal 100, input / output terminals 110, 120 and 130, filters 11, 12 and 13, and low-pass filters 14 and 15.

[0047] The common terminal 100 is connected to the antenna 92. Alternatively, the common terminal 100 may not be directly connected to the antenna 92, or a switch, impedance matching circuit, circulator, or distributor may be inserted and installed between the antenna 92 ​​and the common terminal 100.

[0048] Filter 11 is an example of a first filter, which uses the first frequency band as the passband. Filter 12 is an example of a second filter, which uses the second frequency band as the passband and the third frequency band as the attenuation band. Filter 13 is an example of a third filter, which uses the third frequency band as the passband and the first and second frequency bands as attenuation bands.

[0049] Furthermore, the first frequency band is, for example, a frequency band that includes communication frequency band A, the second frequency band is, for example, a frequency band that includes communication frequency band B, and the third frequency band is, for example, a frequency band that includes communication frequency band C.

[0050] Low-pass filter 14 is an example of a fourth filter, which is a low-pass filter that uses the second and third frequency bands as passbands and the first frequency band as attenuation band.

[0051] Low-pass filter 15 is an example of a fifth filter, which is a low-pass filter that uses the second and third frequency bands as passbands and the first frequency band as attenuation band.

[0052] Here, the frequencies of the second and third frequency bands are at least partially different. In addition, the frequency of the first frequency band does not overlap with the frequencies of the second and third frequency bands, and is located at a higher frequency than the second and third frequency bands.

[0053] One end of filter 11 is connected to common terminal 100, and the other end of filter 11 is connected to input / output terminal 110. Additionally, one end of low-pass filter 14 is connected to common terminal 100, and the other end of low-pass filter 14 is connected to one end of filter 12. The other end of filter 12 is connected to one end of low-pass filter 15, and the other end of low-pass filter 15 is connected to input / output terminal 120. Furthermore, one end of filter 13 is connected to the connection node n1 between the other end of low-pass filter 14 and the end of filter 12, and the other end of filter 13 is connected to input / output terminal 130.

[0054] [1.3 Specific structure of the multiplexer 1A in Embodiment 1]

[0055] Figure 1B This is a circuit diagram of the multiplexer 1A of Embodiment 1. Embodiment 1 discloses a specific circuit structure example of the low-pass filter 14 and low-pass filter 15 of the multiplexer 1 of Embodiment 1. The multiplexer 1A includes a common terminal 100, input / output terminals 110, 120, and 130, filters 11, 12, and 13, and low-pass filters 14A and 15A.

[0056] Low-pass filter 14A includes inductor 81a, inductor 81b, and capacitor 85a. Inductor 81a is connected in series in the signal path connecting common terminal 100 and node n1. The series connection circuit of inductor 81b and capacitor 85a is connected between the node on the signal path connecting inductor 81a and node n1 and ground. That is, low-pass filter 14A mainly provides low-pass function through inductor 81a in the series arm and capacitor 85a in the parallel arm.

[0057] The low-pass filter 15A includes an inductor 81c, capacitors 85b and 85c. A parallel connection circuit of inductor 81c and capacitor 85b is connected in series in the signal path connecting filter 12 and input / output terminal 120. Capacitor 85c is connected between the node in the signal path connecting the parallel connection circuit to filter 12 and ground. In other words, the low-pass filter 15A primarily achieves its low-pass function through the inductor 81c configured in the series arm and the capacitor 85c configured in the parallel arm.

[0058] Figure 1C This is a schematic diagram showing the pass characteristics of each filter included in the multiplexer 1A of Embodiment 1. Filter 11 is a bandpass filter that uses the first frequency band as the passband and the second and third frequency bands as attenuation bands; filter 12 is a bandpass filter that uses the second frequency band as the passband; and filter 13 is a bandpass filter that uses the third frequency band as the passband. Figure 1CAs shown, in this embodiment, the passbands are, in order from the high-frequency side, filter 11 (passband), filter 12 (passband), and filter 13 (passband). That is, they are located in the first frequency band, the second frequency band, and the third frequency band, in order from the high-frequency side. Furthermore, as... Figure 1C As shown, for the pass characteristics of the circuit formed by connecting the low-pass filter 14 and the low-pass filter 15 in series, the passband (second frequency band) of filter 12 and the passband (third frequency band) of filter 13 are used as the passband, and the passband (first frequency band) of filter 11 is used as the attenuation frequency band.

[0059] Figure 2A This is the circuit block diagram of the multiplexer 500 in Comparative Example 1. Additionally, Figure 2B This is the circuit diagram of the 500A multiplexer in Comparative Example 1.

[0060] Figure 2A The multiplexer 500 shown includes a common terminal 100, input / output terminals 110, 120, and 130, filters 11, 12, and 13, a low-pass filter 514, and an impedance matching circuit 520. Compared to the multiplexer 1 of Embodiment 1, the multiplexer 500 of Comparative Example 1 has a different pass-through characteristic of the low-pass filter 514. Furthermore, a low-pass filter 15 is not provided after filter 12; instead, an impedance matching circuit 520 is provided. Hereinafter, for the multiplexer 500 of Comparative Example 1, descriptions of points identical to those of the multiplexer 1 of Embodiment 1 will be omitted, and descriptions will focus on the differences.

[0061] The low-pass filter 514 is a low-pass filter that uses the second and third frequency bands as passbands and the first frequency band as an attenuation band. Furthermore, the low-pass filter 514 has the same pass characteristics as the series connection circuit of the low-pass filters 14 and 15 included in the multiplexer 1 of Embodiment 1. That is, the attenuation in the first frequency band of the low-pass filter 514 is greater than the attenuation in the first frequency band of the low-pass filter 14, and also greater than the attenuation in the first frequency band of the low-pass filter 15. On the other hand, the insertion loss in the second and third frequency bands of the low-pass filter 514 is greater than the insertion loss in the second and third frequency bands of the low-pass filter 14, and also greater than the insertion loss in the second and third frequency bands of the low-pass filter 15.

[0062] One end of filter 11 is connected to common terminal 100, and the other end of filter 11 is connected to input / output terminal 110. Additionally, one end of low-pass filter 514 is connected to common terminal 100, and the other end of low-pass filter 514 is connected to one end of filter 12. The other end of filter 12 is connected to one end of impedance matching circuit 520, and the other end of impedance matching circuit 520 is connected to input / output terminal 120. Furthermore, one end of filter 13 is connected to the connection node n1 between the other end of low-pass filter 514 and one end of filter 12, and the other end of filter 13 is connected to input / output terminal 130.

[0063] Figure 2B This is the circuit diagram of the 500A multiplexer in Comparative Example 1. Figure 2B The multiplexer 500A shown illustrates Figure 2A The specific circuit structure of the low-pass filter 514 of the multiplexer 500A is shown.

[0064] The low-pass filter 514A includes inductors 82a, 82b, and 82c, and capacitors 87a, 87b, and 87c. Inductor 82a is connected in series in the signal path connecting common terminal 100 and node n1. A series connection circuit of inductor 82b and capacitor 87a is connected between the node on the signal path connecting inductor 82a and node n1 and ground. Additionally, a parallel connection circuit of inductor 82c and capacitor 87b is connected in series in the signal path connecting common terminal 100 and node n1. Capacitor 87c is connected between the node on the signal path connecting the aforementioned parallel connection circuit and node n1 and ground. In other words, the low-pass filter 514A has a low-pass function mainly through the inductor 82a arranged in the series arm and the capacitor 87a arranged in the parallel arm, and also through the inductor 82c arranged in the series arm and the capacitor 87c arranged in the parallel arm, and has the same pass characteristics as the series connection circuit of the low-pass filter 14 and low-pass filter 15 provided in the multiplexer 1 of Embodiment 1.

[0065] In addition, the impedance matching circuit 520 is composed of inductors 520A arranged in series.

[0066] Based on the above-described structure of the multiplexer 500 (and 500A) in Comparative Example 1, isolation between filter 11 and filters 12 and 13 can be ensured by using the low-pass filter 514. Here, as... Figure 1C As shown, since the attenuation function of filter 12 in the first frequency band is relatively low (the attenuation in the first frequency band is small), a low-pass filter 514 is required on the second signal path connecting the common terminal 100 and the input / output terminal 120. On the other hand, as Figure 1CAs shown, filter 13 has a higher attenuation capability in the first frequency band compared to filter 12 (the attenuation amount in the first frequency band is larger). Therefore, if a low-pass filter 514 is configured on the third signal path connecting the common terminal 100 and the input / output terminal 130, the attenuation capability in the first frequency band becomes excessive (overkill). Consequently, the transmission loss in the third signal path deteriorates due to the configuration of the low-pass filter 514. In other words, the following problem arises: because of the difference in the required attenuation amount in the first frequency band between the two filters 12 and 13, which are commonly connected to the low-pass filter 514, the transmission loss of the third signal path with filter 13 configured deteriorates.

[0067] In contrast, according to the structure of the multiplexer 1A in Embodiment 1, a low-pass filter 14 is connected between filters 12 and 13 and the common terminal 100, and a low-pass filter 15 is connected to the other end of filter 12. That is, the filter functions that allow the second and third frequency bands to pass through and attenuate the first frequency band are divided and arranged in the pre-stage (between the common terminal 100 and filters 12 and 13) and the post-stage (between filter 12 and input / output terminal 120) of filters 12 and 13. Here, the low-pass filter 14 has the function of shifting the impedance in the first frequency band when viewed from the common terminal 100 and the impedance in the first frequency band when viewed from the common terminal 100 towards the open-circuit side. In other words, the low-pass filter 14 has the function of increasing the reflection coefficient in the first frequency band of the second and third signal paths. Furthermore, the low-pass filter 14 has the function of increasing the attenuation in the first frequency band of the second and third signal paths. On the other hand, the low-pass filter 15 has the function of increasing the reflection coefficient in the first frequency band of the second and third signal paths. Furthermore, low-pass filter 15 has the function of increasing the attenuation in the first frequency band of the second signal path. Also, low-pass filter 15 functions as an impedance matching circuit disposed after filter 12. Moreover, low-pass filter 15 is less effective than low-pass filter 14 in increasing the reflection coefficient in the first frequency band when viewed from common terminal 100 for both filters 12 and 13. This is because the low-pass filter, which is more closely connected to common terminal 100, contributes more to increasing the reflection coefficient in the first frequency band.

[0068] In other words, by placing the low-pass filter 14 before filters 12 and 13, sufficient isolation between filter 11 and filters 12 and 13 can be ensured. Furthermore, since the low-pass filter 14 is placed on the third signal path connecting the common terminal 100 and the input / output terminal 130, but the low-pass filter 15 is not placed, compared to a multiplexer 500 that places a filter circuit (low-pass filter 514) formed by connecting the low-pass filters 14 and 15 in series before filters 12 and 13, the transmission loss of the third signal path can be reduced by the amount of insertion loss of the low-pass filter 15. That is, isolation between filter 11 and filters 12 and 13 can be ensured, and the attenuation in the first frequency band of the second and third signal paths can be sufficiently ensured, while the transmission loss of the third signal path can be reduced. Moreover, since the low-pass filter 15 is placed after filter 12, the circuit elements constituting the low-pass filter 15 can also serve as impedance matching elements between filter 12 and the circuit elements connected to the stage after filter 12. In other words, in the multiplexer 1 of Embodiment 1, the impedance matching circuit 520 configured in the multiplexer 500 of Comparative Example 1 is not required. Therefore, the transmission loss of the multiplexer 1 is reduced, and the number of circuit elements can be reduced to achieve miniaturization.

[0069] [1.4 Specific structure of the multiplexer 2 in variation 1]

[0070] Figure 3A This is a circuit diagram of multiplexer 2 in Modified Example 1. Multiplexer 2 includes a common terminal 100, input / output terminals 110, 120, and 130, filters 21, 22, and 23, and high-pass filters 24 and 25. Compared to multiplexer 1 in Embodiment 1, multiplexer 2 in Modified Example 1 differs in the frequency relationships of the first, second, and third frequency bands, and in the fact that a high-pass filter is provided instead of a low-pass filter. Hereinafter, for multiplexer 2 in Modified Example 1, descriptions of points identical to those in multiplexer 1 in Embodiment 1 will be omitted, and descriptions will focus on the differences.

[0071] Filter 21 is an example of a first filter, which uses the first frequency band as the passband and the second and third frequency bands as attenuation bands. Filter 22 is an example of a second filter, which uses the second frequency band as the passband and the third frequency band as the attenuation band. Filter 23 is an example of a third filter, which uses the third frequency band as the passband and the first and second frequency bands as attenuation bands.

[0072] High-pass filter 24 is an example of a fourth filter, which is a high-pass filter that uses the second and third frequency bands as passbands and the first frequency band as attenuation band.

[0073] High-pass filter 25 is an example of a fifth filter, which is a high-pass filter that uses the second and third frequency bands as passbands and the first frequency band as attenuation band.

[0074] Here, the frequencies of the second and third frequency bands are at least partially different. In addition, the frequency of the first frequency band does not overlap with the frequencies of the second and third frequency bands, and it is located on the lower frequency side than the second and third frequency bands.

[0075] One end of filter 21 is connected to common terminal 100, and the other end of filter 21 is connected to input / output terminal 110. Additionally, one end of high-pass filter 24 is connected to common terminal 100, and the other end of high-pass filter 24 is connected to one end of filter 22. The other end of filter 22 is connected to one end of high-pass filter 25, and the other end of high-pass filter 25 is connected to input / output terminal 120. Furthermore, one end of filter 23 is connected to the connection node n1 between the other end of high-pass filter 24 and the first end of filter 22, and the other end of filter 23 is connected to input / output terminal 130.

[0076] Figure 3B This is a schematic diagram showing the pass characteristics of each filter in the multiplexer 2 of Modified Example 1. Filter 21 is a bandpass filter with the first frequency band as its passband, filter 22 is a bandpass filter with the second frequency band as its passband, and filter 23 is a bandpass filter with the third frequency band as its passband. Figure 3B As shown, in this modified example, from the low-frequency side, the passbands are filter 21 (passband), filter 22 (passband), and filter 23 (passband). That is, from the low-frequency side, they are located in the first frequency band, the second frequency band, and the third frequency band, respectively. Furthermore, as... Figure 3B As shown, for the pass characteristics of the circuit formed by connecting high-pass filter 24 and high-pass filter 25 in series, the passband (second frequency band) of filter 22 and the passband (third frequency band) of filter 23 are used as the passband, and the passband (first frequency band) of filter 21 is used as the attenuation frequency band.

[0077] According to the structure of the multiplexer 2 in this modified example, a high-pass filter 24 is connected between filters 22 and 23 and the common terminal 100, and a high-pass filter 25 is connected to the other end of filter 22. That is, the filter functions that allow the second and third frequency bands to pass through and attenuate the first frequency band are divided and arranged in the pre-stage (between the common terminal 100 and filters 22 and 23) and the post-stage (between filter 22 and input / output terminal 120) of filters 22 and 23. Here, the high-pass filter 24 has the function of shifting the impedance in the first frequency band when viewing filter 22 from the common terminal 100 and the impedance in the first frequency band when viewing filter 23 from the common terminal 100 towards the open-circuit side. In other words, the high-pass filter 24 has the function of increasing the reflection coefficient in the first frequency band of the second and third signal paths. Furthermore, the high-pass filter 24 has the function of increasing the attenuation in the first frequency band of the second and third signal paths. On the other hand, the high-pass filter 25 has the function of increasing the reflection coefficient in the first frequency band of the second and third signal paths. Furthermore, the high-pass filter 25 has the function of increasing the attenuation in the first frequency band of the second signal path. Also, the high-pass filter 25 functions as an impedance matching circuit disposed after the filter 22. Moreover, in terms of increasing the reflection coefficient in the first frequency band when viewing filters 22 and 23 from the common terminal 100, the high-pass filter 25 is less effective than the high-pass filter 24. This is because the high-pass filter, which is more closely connected to the common terminal 100, contributes more to increasing the reflection coefficient in the first frequency band.

[0078] In other words, by placing the high-pass filter 24 before filters 22 and 23, sufficient isolation between filter 21 and filters 22 and 23 can be ensured. Furthermore, since the high-pass filter 24 is placed in the third signal path connecting the common terminal 100 and the input / output terminal 130, but not the high-pass filter 25, the transmission loss of the third signal path is reduced by the amount of insertion loss of the high-pass filter 25 compared to a multiplexer that places the filter circuit consisting of the high-pass filters 24 and 25 connected in series before filters 22 and 23. That is, isolation between filter 21 and filters 22 and 23 can be ensured, and the attenuation in the first frequency band of the second and third signal paths can be sufficiently ensured, while the transmission loss of the third signal path is reduced. Moreover, since the high-pass filter 25 is placed after filter 22, the circuit elements constituting the high-pass filter 25 can also serve as impedance matching elements between filter 22 and the circuit elements connected to the stage after filter 22. In other words, in the multiplexer 2 of Modified Example 1, the impedance matching circuit 520 configured in the multiplexer 500 of Comparative Example 1 is not required. Therefore, the transmission loss of the multiplexer 2 is reduced, and the number of circuit elements can be reduced to achieve miniaturization.

[0079] [1.5 Specific structure of the multiplexer 3 in variation 2]

[0080] Figure 4A This is a circuit diagram of multiplexer 3 in Modified Example 2. Multiplexer 3 includes a common terminal 100, input / output terminals 110, 120, and 130, filters 31, 32, and 33, and low-pass filters 34 and 35. Modified Example 2 differs from Multiplexer 1 in Embodiment 1 in that filter 32 is a band-stop filter instead of a band-pass filter. Hereinafter, for Multiplexer 3 of Modified Example 2, descriptions of points identical to those of Multiplexer 1 of Embodiment 1 will be omitted, and descriptions will focus on the differences.

[0081] Filter 31 is an example of a first filter, which uses the first frequency band as the passband and the second and third frequency bands as attenuation bands. Filter 32 is an example of a second filter, which is a band-stop filter that uses the third frequency band as the attenuation band. Filter 33 is an example of a third filter, which uses the third frequency band as the passband and the first and second frequency bands as attenuation bands. Filters 32 and 33 use the third frequency band as the attenuation band and passband, respectively, and together form an extractor.

[0082] Low-pass filter 34 is an example of a fourth filter, which is a low-pass filter that uses the second and third frequency bands as passbands and the first frequency band as attenuation band.

[0083] Low-pass filter 35 is an example of a fifth filter, which is a low-pass filter that uses the second and third frequency bands as passbands and the first frequency band as attenuation band.

[0084] Here, the frequencies of the second and third frequency bands are at least partially different. In addition, the frequency of the first frequency band does not overlap with the frequencies of the second and third frequency bands, and is located at a higher frequency than the second and third frequency bands.

[0085] One end of filter 31 is connected to common terminal 100, and the other end of filter 31 is connected to input / output terminal 110. Additionally, one end of low-pass filter 34 is connected to common terminal 100, and the other end of low-pass filter 34 is connected to one end of filter 32. The other end of filter 32 is connected to one end of low-pass filter 35, and the other end of low-pass filter 35 is connected to input / output terminal 120. Furthermore, one end of filter 33 is connected to the connection node n1 between the other end of low-pass filter 34 and the first end of filter 32, and the other end of filter 33 is connected to input / output terminal 130.

[0086] Figure 4B This is a schematic diagram showing the pass characteristics of each filter in the multiplexer 3 of Modified Example 2. Filter 31 is a bandpass filter with the first frequency band as its passband, filter 32 is a bandstop filter with the third frequency band as its attenuation band, and filter 33 is a bandpass filter with the third frequency band as its passband. Figure 4B As shown, in this modified example, from the high-frequency side, the filters are, in order, filter 31 (passband), filter 32 (part of passband), filter 33 (passband), and filter 32 (another part of passband). That is, from the high-frequency side, they are located in the first frequency band, a part of the second frequency band, the third frequency band, and another part of the second frequency band. Furthermore, as... Figure 4BAs shown, regarding the pass-through characteristics of the circuit formed by connecting low-pass filter 34 and low-pass filter 35 in series, the passband (second frequency band) of filter 32 and the passband (third frequency band) of filter 33 are used as passbands, and the passband (first frequency band) of filter 31 is used as the attenuation frequency band. Here, since filter 32 is a band-stop filter that uses the third frequency band as the attenuation frequency band, the attenuation function of the first frequency band is relatively low (the attenuation amount in the first frequency band is small). Therefore, low-pass filter 34 and low-pass filter 35 are needed on the second signal path connecting common terminal 100 and input / output terminal 120. On the other hand, since filter 33 is a band-pass filter that uses the third frequency band as the passband, the attenuation function of the first frequency band is higher than that of filter 32 (the attenuation amount in the first frequency band is large). Therefore, if both low-pass filter 34 and low-pass filter 35 are configured on the third signal path connecting common terminal 100 and input / output terminal 130, the attenuation function of the first frequency band becomes excessive (overkill).

[0087] According to the structure of the multiplexer 3 in this modified example, a low-pass filter 34 is connected between filters 32 and 33 and the common terminal 100, and a low-pass filter 35 is connected to the other end of filter 32. That is, the filter functions that allow the second and third frequency bands to pass through and attenuate the first frequency band are divided and arranged in the pre-stage (between the common terminal 100 and filters 32 and 33) and the post-stage (between filter 32 and input / output terminal 120) of filters 32 and 33. Here, the low-pass filter 34 has the function of shifting the impedance in the first frequency band when viewed from the common terminal 100 and the impedance in the first frequency band when viewed from the common terminal 100 towards the open-circuit side. In other words, the low-pass filter 34 has the function of increasing the reflection coefficient in the first frequency band of the second and third signal paths. Furthermore, the low-pass filter 34 has the function of increasing the attenuation in the first frequency band of the second and third signal paths. On the other hand, the low-pass filter 35 has the function of increasing the reflection coefficient in the first frequency band of the second and third signal paths. Furthermore, the low-pass filter 35 has the function of increasing the attenuation in the first frequency band of the second signal path. Also, the low-pass filter 35 functions as an impedance matching circuit disposed after the filter 32. Moreover, in terms of increasing the reflection coefficient in the first frequency band when viewing filters 32 and 33 from the common terminal 100, the low-pass filter 35 is less effective than the low-pass filter 34. This is because the low-pass filter, which is more closely connected to the common terminal 100, contributes more to increasing the reflection coefficient in the first frequency band.

[0088] In other words, by placing the low-pass filter 34 before filters 32 and 33, sufficient isolation between filter 31 and filters 32 and 33 can be ensured. Furthermore, since the low-pass filter 34 is placed on the third signal path connecting the common terminal 100 and the input / output terminal 130, but the low-pass filter 35 is not placed, compared to a multiplexer that places a filter circuit consisting of a series-connected low-pass filter 34 and low-pass filter 35 before filters 32 and 33, the transmission loss of the third signal path can be reduced by the amount of insertion loss of the low-pass filter 35. That is, isolation between filter 31 and filters 32 and 33 can be ensured, and the attenuation in the first frequency band of the second and third signal paths can be sufficiently ensured, while the transmission loss of the third signal path is reduced. Moreover, since the low-pass filter 35 is placed after filter 32, the circuit elements constituting the low-pass filter 35 can also serve as impedance matching elements between filter 32 and the circuit elements connected to the stage after filter 32. In other words, in the multiplexer 3 of Modified Example 2, the impedance matching circuit 520 configured in the multiplexer 500 of Comparative Example 1 is not required. Therefore, the transmission loss of the multiplexer 3 is reduced, and the number of circuit elements can be reduced to achieve miniaturization.

[0089] Furthermore, as a variation of the multiplexer 3 of Variation Example 2, a multiplexer with different frequency relationships in the first frequency band, the second frequency band, and the third frequency band, and equipped with a high-pass filter instead of a low-pass filter, is also included in the present invention.

[0090] That is, in the modified multiplexer 3, the frequencies of the second and third frequency bands are at least partially different, the frequency of the first frequency band does not overlap with the frequencies of the second and third frequency bands, and is located at a lower frequency than the second and third frequency bands. Furthermore, instead of the low-pass filters 34 and 35 in the modified multiplexer 3, high-pass filters are configured in the pre- and post-stages of filter 32, respectively, using the second and third frequency bands as passbands and the first frequency band as an attenuation band.

[0091] Therefore, sufficient isolation between filter 31 and filters 32 and 33 can be ensured, the transmission loss of the third signal path can be reduced by the amount of insertion loss of the high-pass filter configured in the subsequent stage, and the circuit elements constituting the high-pass filter configured in the subsequent stage can also serve as impedance matching elements connected to the subsequent stage of filter 32. Thus, the transmission loss of the multiplexer is reduced, and the number of circuit elements can be reduced to achieve miniaturization.

[0092] (Implementation Method 2)

[0093] In Embodiment 1, a multiplexer with a structure that divides and arranges a low-pass filter or a high-pass filter in the pre-stage and post-stage of the second filter was described. However, in this embodiment, a multiplexer with a structure that divides and arranges both a low-pass filter and a high-pass filter in the pre-stage and post-stage of the second filter is described.

[0094] [2.1 Structure of Multiplexer 4]

[0095] Figure 5A This is a circuit block diagram of the multiplexer 4 in Embodiment 2. As shown in the figure, the multiplexer 4 includes a common terminal 100, input / output terminals 110, 120 and 130, filters 41, 42 and 43, low-pass filters 44 and 45, and high-pass filters 46 and 47.

[0096] Filter 41 is an example of a first filter, which uses the first frequency band as the passband and the second and third frequency bands as attenuation bands. Filter 42 is an example of a second filter, which is a band-stop filter that uses the third frequency band as the attenuation band. Filter 43 is an example of a third filter, which uses the third frequency band as the passband and the first and second frequency bands as attenuation bands. Filters 42 and 43, using the third frequency band as the attenuation band and passband respectively, constitute an extractor.

[0097] Low-pass filter 44 is an example of a sixth filter, which is a low-pass filter that uses the second and third frequency bands as passbands and the first frequency band as attenuation band.

[0098] High-pass filter 46 is an example of a seventh filter, which is a high-pass filter that uses the second and third frequency bands as passbands.

[0099] Low-pass filter 45 is an example of an eighth filter, which is a low-pass filter that uses the second and third frequency bands as passbands and the first frequency band as attenuation band.

[0100] High-pass filter 47 is an example of the ninth filter, which is a high-pass filter that uses the second and third frequency bands as passbands.

[0101] Here, the frequencies of the second and third frequency bands are at least partially different. In addition, the frequencies of the first, second, and third frequency bands do not overlap, and the first frequency band is located at a higher frequency than the second and third frequency bands.

[0102] One end of filter 41 is connected to common terminal 100, and the other end of filter 41 is connected to input / output terminal 110. Additionally, one end of low-pass filter 44 is connected to common terminal 100, and the other end of low-pass filter 44 is connected to one end of high-pass filter 46. The other end of high-pass filter 46 is connected to one end of filter 42. The other end of filter 42 is connected to one end of low-pass filter 45, and the other end of low-pass filter 45 is connected to one end of high-pass filter 47. The other end of high-pass filter 47 is connected to input / output terminal 120. Furthermore, one end of filter 43 is connected to the connection node n1 between the other end of high-pass filter 46 and one end of filter 42, and the other end of filter 43 is connected to input / output terminal 130.

[0103] [2.2 Specific structure of the multiplexer 4A in Embodiment 2]

[0104] Figure 5B This is a circuit diagram of the multiplexer 4A in Embodiment 2. Embodiment 2 discloses a specific circuit structure example of the multiplexer 4A in Embodiment 2. The multiplexer 4A includes a common terminal 100, input / output terminals 110, 120, and 130, filters 41, 42, and 43, low-pass filters 44 and 45, and high-pass filters 46 and 47.

[0105] Filter 41 includes an inductor 73a and capacitors 77a, 77b, and 77c. Capacitors 77a and 77b are connected in series in the first signal path connecting the common terminal 100 and the input / output terminal 110, respectively. An LC series resonant circuit of inductor 73a and capacitor 77c is connected between the connection node of capacitors 77a and 77b and ground. With the above structure, filter 41 constitutes an LC filter with the first frequency band (communication band A) as the passband.

[0106] Filter 42 includes a series arm resonator 65s, parallel arm resonators 65p and 66p, an inductor 72a, and a capacitor 76a. The series arm resonator 65s is an elastic wave resonator connected in series in the second signal path connecting node n1 and input / output terminal 120. The parallel arm resonators 65p and 66p are elastic wave resonators connected between a node on the aforementioned second signal path and ground, respectively. An LC parallel resonant circuit of inductor 72a and capacitor 76a is connected in series in the second signal path connecting node n1 and series arm resonator 65s. With this structure, filter 42 constitutes a trapezoidal elastic wave filter that uses the third frequency band (communication band C) as its attenuation band.

[0107] Filter 43 includes series arm resonators 60s, 61s, 62s, 63s, and 64s, parallel arm resonators 60p, 61p, 62p, 63p, and 64p, inductors 71a and 71b, and capacitor 75a. The series arm resonators 60s to 64s are elastic wave resonators connected in series in the third signal path connecting node n1 and input / output terminal 130. The parallel arm resonators 60p to 64p are elastic wave resonators connected between a node on the aforementioned third signal path and ground. Inductor 71a is connected between the connection node of parallel arm resonators 60p to 62p and ground. Inductor 71b is connected between the connection node of parallel arm resonators 63p and 64p and ground. Capacitor 75a is connected in series between node n1 and series arm resonator 60s. With the above structure, filter 43 constitutes a trapezoidal elastic wave filter with the third frequency band (communication band C) as the passband.

[0108] The low-pass filter 44 includes inductors 83a and 83b and a capacitor 88a. Inductor 83a is connected in series in the signal path connecting common terminal 100 and node n1. The series connection circuit of inductor 83b and capacitor 88a is connected between the node on the signal path connecting inductor 83a and node n1 and ground. In other words, the low-pass filter 44 primarily functions as a low-pass filter through the inductor 83a in the series arm and the capacitor 88a in the parallel arm.

[0109] The high-pass filter 46 has an inductor 83c. The inductor 83c is connected between the node and ground on the signal path connecting the common terminal 100 and node n1. The high-pass filter 46 has a high-pass function through the inductor 83c configured in the parallel arm.

[0110] The low-pass filter 45 includes an inductor 83d and capacitors 88b and 88c. A parallel connection circuit of inductor 83d and capacitor 88b is connected in series in the second signal path connecting filter 42 and input / output terminal 120. Capacitor 88c is connected between a node on the second signal path and ground. In other words, the low-pass filter 45 primarily functions as a low-pass filter through the inductor 83d in the series arm and the capacitor 88c in the parallel arm.

[0111] The high-pass filter 47 includes an inductor 83e and capacitors 88d and 88e. Capacitor 88d is connected in series in the second signal path connecting filter 42 and input / output terminal 120. The series connection circuit of inductor 83e and capacitor 88e is connected between a node on the second signal path and ground. In other words, the high-pass filter 47 primarily achieves its high-pass function through capacitor 88d in the series arm and inductor 83e in the parallel arm.

[0112] In the multiplexer 4A of this embodiment, the first frequency band (communication band A) is, for example, the ultra-high frequency band (3300-5000MHz), the second frequency band (communication band B) is, for example, the mid-high frequency band (1710-2370MHz and 2496-2690MHz), and the third frequency band is, for example, WLAN (Wireless Local Area Network, 2400-2483MHz).

[0113] Figure 5C This is a schematic diagram showing the pass characteristics of each filter in the multiplexer 4A of Embodiment 2. Filter 41 is a bandpass filter with the first frequency band as its passband, filter 42 is a bandstop filter with the third frequency band as its attenuation band, and filter 43 is a bandpass filter with the third frequency band as its passband. Figure 5C As shown, in this embodiment, from the high-frequency side, the filters are sequentially: filter 41 (passband), filter 42 (part of passband), filter 43 (passband), and filter 42 (another part of passband). That is, from the high-frequency side, they are sequentially located in the first frequency band, a part of the second frequency band, the third frequency band, and another part of the second frequency band. Furthermore, as... Figure 5C As shown, for the pass-through characteristics of the circuit formed by connecting low-pass filters 44 and 45 in series, the passband (second frequency band) of filter 42 and the passband (third frequency band) of filter 43 are used as passbands, and the passband (first frequency band) of filter 41 is used as the attenuation frequency band. Similarly, for the pass-through characteristics of the circuit formed by connecting high-pass filters 46 and 47 in series, the passband (second frequency band) of filter 42 and the passband (third frequency band) of filter 43 are used as passbands. Here, since filter 42 is a band-stop filter that uses the third frequency band as the attenuation frequency band, its attenuation function in the first frequency band is relatively low (the attenuation amount in the first frequency band is small). Therefore, low-pass filters 44 and 45 are needed in the second signal path connecting the common terminal 100 and the input / output terminal 120. On the other hand, since filter 43 is a band-pass filter that uses the third frequency band as the passband, its attenuation function in the first frequency band is higher than that of filter 42 (the attenuation amount in the first frequency band is large). Therefore, if low-pass filters 44 and 45 are configured in the third signal path connecting the common terminal 100 and the input / output terminal 130, the function of attenuating the first frequency band becomes excessive (overkill).

[0114] Furthermore, since filter 42 has a lower attenuation function for frequencies lower than the second and third frequency bands, high-pass filters 46 and 47 are required in the second signal path connecting the common terminal 100 and the input / output terminal 120. On the other hand, since filter 43 is a bandpass filter that uses the third frequency band as its passband, its attenuation function for frequencies lower than the second and third frequency bands is higher than that of filter 42. Therefore, if high-pass filters 46 and 47 are configured in the third signal path connecting the common terminal 100 and the input / output terminal 130, the attenuation function of the first frequency band becomes excessive (overkill).

[0115] According to the structure of the multiplexer 4A in this embodiment, a low-pass filter 44 and a high-pass filter 46 are connected between filters 42 and 43 and the common terminal 100, and a low-pass filter 45 and a high-pass filter 47 are connected to the other end of filter 42. That is, the low-pass filter function, which allows the second and third frequency bands to pass and attenuates the first frequency band, is divided and configured in the pre-stage (between the common terminal 100 and filters 42 and 43) and the post-stage (between filter 42 and input / output terminal 120) of filters 42 and 43. Similarly, the high-pass filter function, which allows the second and third frequency bands to pass and attenuates frequency bands lower than the second and third frequency bands, is divided and configured in the pre-stage (between the common terminal 100 and filters 42 and 43) and the post-stage (between filter 42 and input / output terminal 120) of filters 42 and 43. Here, the low-pass filter 44 has the function of shifting the impedance in the first frequency band when viewed from the common terminal 100 (filter 42) and the impedance in the first frequency band when viewed from the common terminal 100 (filter 43) towards the open-circuit side. In other words, the low-pass filter 44 has the function of increasing the reflection coefficient in the first frequency band of the second and third signal paths. Additionally, the low-pass filter 44 has the function of increasing the attenuation in the first frequency band of the second and third signal paths. On the other hand, the low-pass filter 45 has the function of increasing the reflection coefficient in the first frequency band of the second and third signal paths. Additionally, the low-pass filter 45 has the function of increasing the attenuation in the first frequency band of the second signal path. Furthermore, the low-pass filter 45 also functions as an impedance matching circuit disposed after the filter 42. Moreover, the low-pass filter 45 is less effective than the low-pass filter 44 in increasing the reflection coefficient in the first frequency band when viewed from the common terminal 100. This is because the low-pass filter connected more closely to the common terminal 100 contributes more to increasing the reflection coefficient in the first frequency band.

[0116] On the other hand, high-pass filters 46 and 47 have the function of increasing the attenuation of the second and third signal paths compared to the lower frequency side of the first, second, and third frequency bands.

[0117] In other words, by placing the low-pass filter 44 before filters 42 and 43, sufficient isolation between filter 41 and filters 42 and 43 can be ensured. Furthermore, since the low-pass filter 44 is placed in the third signal path connecting the common terminal 100 and the input / output terminal 130, but the low-pass filter 45 is not placed, compared to a multiplexer that places a filter circuit consisting of a series-connected low-pass filter 44 and low-pass filter 45 before filters 42 and 43, the transmission loss of the third signal path can be reduced by the amount of insertion loss of the low-pass filter 45. That is, isolation between filter 41 and filters 42 and 43 is ensured, and the attenuation in the first frequency band of the second and third signal paths can be sufficiently ensured, while the transmission loss of the third signal path is reduced. Moreover, since the low-pass filter 45 and high-pass filter 47 are placed after filter 42, the circuit elements constituting the low-pass filter 45 and high-pass filter 47 can also serve as impedance matching elements for filter 42 and the circuit elements connected to the stage after filter 42. In other words, in the multiplexer 4A of Embodiment 2, there is no need to configure a separate impedance matching circuit after the filter 42. Therefore, the transmission loss of the multiplexer 4A is reduced, and the number of circuit elements can be reduced to achieve miniaturization.

[0118] [2.3 Specific structure of the multiplexer 5 in variation 3]

[0119] Furthermore, as a variation of the multiplexer 4 in Embodiment 2, multiplexers with different frequency relationships in the first, second, and third frequency bands are also included in this invention.

[0120] Figure 6A This is a circuit diagram of the multiplexer 5 in Modified Example 3. The multiplexer 5 in Modified Example 3 includes a common terminal 100, input / output terminals 110, 120, and 130, filters 51, 52, and 53, low-pass filters 54 and 55, and high-pass filters 56 and 57. Compared to the multiplexer 4 in Embodiment 2, the frequency relationships of the first, second, and third frequency bands in the multiplexer 5 of Modified Example 3 are different. Hereinafter, for the multiplexer 5 of Modified Example 3, descriptions of points identical to those in the multiplexer 4 of Embodiment 2 will be omitted, and the description will focus on the differences.

[0121] Filter 51 is an example of a first filter, which uses the first frequency band as the passband and the second and third frequency bands as attenuation bands. Filter 52 is an example of a second filter, which is a band-stop filter that uses the third frequency band as the attenuation band. Filter 53 is an example of a third filter, which uses the third frequency band as the passband and the first and second frequency bands as attenuation bands. Filters 52 and 53, using the third frequency band as the attenuation band and passband respectively, constitute an extractor.

[0122] Low-pass filter 54 is an example of a sixth filter, which is a low-pass filter that uses the second and third frequency bands as passbands.

[0123] High-pass filter 56 is an example of a seventh filter, which is a high-pass filter that uses the second and third frequency bands as passbands and the first frequency band as attenuation band.

[0124] Low-pass filter 55 is an example of an eighth filter, which is a low-pass filter that uses the second and third frequency bands as passbands.

[0125] High-pass filter 57 is an example of the ninth filter, which is a high-pass filter that uses the second and third frequency bands as passbands and the first frequency band as attenuation band.

[0126] Here, the frequencies of the second and third frequency bands are at least partially different. In addition, the frequency of the first frequency band does not overlap with the frequencies of the second and third frequency bands, and it is located on the lower frequency side than the second and third frequency bands.

[0127] One end of filter 51 is connected to common terminal 100, and the other end of filter 51 is connected to input / output terminal 110. Additionally, one end of high-pass filter 56 is connected to common terminal 100, and the other end of high-pass filter 56 is connected to one end of low-pass filter 54. The other end of low-pass filter 54 is connected to one end of filter 52. The other end of filter 52 is connected to one end of low-pass filter 55, and the other end of low-pass filter 55 is connected to one end of high-pass filter 57. The other end of high-pass filter 57 is connected to input / output terminal 120. Furthermore, one end of filter 53 is connected to the connection node n1 between the other end of low-pass filter 54 and one end of filter 52, and the other end of filter 53 is connected to input / output terminal 130.

[0128] [2.4 Specific structure of the multiplexer 5A in variation 3]

[0129] Figure 6BThis is a circuit diagram of the multiplexer 5A in Modified Example 3. Modified Example 3 discloses a specific circuit structure example of the multiplexer 5A. The multiplexer 5A includes a common terminal 100, input / output terminals 110, 120 and 130, filters 51, 52 and 53, low-pass filters 54 and 55, and high-pass filters 56 and 57.

[0130] Filter 51 includes series arm resonators 66s, 67s, and 68s, parallel arm resonators 67p and 68p, an inductor 74a, and a capacitor 78a. The series arm resonators 66s to 68s are elastic wave resonators connected in series in the first signal path connecting the common terminal 100 and the input / output terminal 110. The parallel arm resonators 67p to 68p are elastic wave resonators connected between a node on the first signal path and ground. The inductor 74a is connected in series between the common terminal 100 and the series arm resonator 66s. The capacitor 78a is connected between a node on the first signal path and ground. With this structure, filter 51 constitutes a trapezoidal elastic wave filter with a first frequency band (communication band A) as its passband.

[0131] Since filter 52 has the same circuit structure as filter 42 in embodiment 2, its description is omitted. Filter 52 is configured as a trapezoidal elastic wave filter that uses the third frequency band (communication band C) as the attenuation frequency band.

[0132] Since filter 53 has the same circuit structure as filter 43 in embodiment 2, its description is omitted. Filter 53 is configured as a trapezoidal elastic wave filter with the third frequency band (communication band C) as the passband.

[0133] The low-pass filter 54 has an inductor 84b and a capacitor 89b. The series connection circuit of the inductor 84b and the capacitor 89b is connected between the node and ground on the signal path connecting the common terminal 100 and node n1. That is, the low-pass filter 54 mainly has a low-pass function through the capacitor 89b arranged in the parallel arm.

[0134] The high-pass filter 56 includes an inductor 84a and a capacitor 89a. The capacitor 89a is connected in series in the signal path connecting the common terminal 100 and node n1. The inductor 84a is connected between the node and ground in the signal path connecting the common terminal 100 and node n1. The high-pass filter 56 thus provides a high-pass function.

[0135] The low-pass filter 55 includes an inductor 84c and capacitors 89c and 89d. A parallel connection circuit of inductor 84c and capacitor 89c is connected in series in the second signal path connecting filter 52 and input / output terminal 120. Capacitor 89d is connected between a node on the second signal path and ground. In other words, the low-pass filter 55 primarily functions as a low-pass filter through the inductor 84c in the series arm and the capacitor 89d in the parallel arm.

[0136] The high-pass filter 57 includes an inductor 84d and capacitors 89e and 89f. Capacitor 89e is connected in series in the second signal path connecting filter 52 and input / output terminal 120. The series connection circuit of inductor 84d and capacitor 89f is connected between a node on the second signal path and ground. In other words, the high-pass filter 57 primarily achieves its high-pass function through capacitor 89e in the series arm and inductor 84d in the parallel arm.

[0137] In the multiplexer 5A of this embodiment, the first frequency band (communication band A) is, for example, GNSS (Global Navigation Satellite System) L5 (1164.4-1187.95MHz), the second frequency band (communication band B) is, for example, the mid-to-high frequency band (1710-2370MHz and 2496-2690MHz), and the third frequency band (communication band C) is, for example, WLAN (2400-2483MHz).

[0138] Figure 6C This is a schematic diagram showing the pass characteristics of each filter in the multiplexer 5A of Modified Example 3. Filter 51 is a bandpass filter with the first frequency band as its passband, filter 52 is a bandstop filter with the third frequency band as its attenuation band, and filter 53 is a bandpass filter with the third frequency band as its passband. Figure 6C As shown, in this modified example, from the low-frequency side, the filters are, in sequence, the passband of filter 51, a portion of the passband of filter 52, the passband of filter 53, and another portion of the passband of filter 52. That is, from the low-frequency side, they are located in the first frequency band, a portion of the second frequency band, the third frequency band, and another portion of the second frequency band. Furthermore, as... Figure 6CAs shown, for the pass-through characteristics of the circuit formed by connecting low-pass filter 54 and low-pass filter 55 in series, the passband (second frequency band) of filter 52 and the passband (third frequency band) of filter 53 are used as the passbands. Furthermore, for the pass-through characteristics of the circuit formed by connecting high-pass filter 56 and high-pass filter 57 in series, the passband (second frequency band) of filter 52 and the passband (third frequency band) of filter 53 are used as the passbands, and the passband (first frequency band) of filter 51 is used as the attenuation frequency band. Here, since filter 52 is a band-stop filter that uses the third frequency band as the attenuation frequency band, the attenuation function of the first frequency band is relatively low (the attenuation amount in the first frequency band is small). Therefore, high-pass filter 56 and high-pass filter 57 are required in the second signal path connecting the common terminal 100 and the input / output terminal 120. Furthermore, since filter 52 has a lower attenuation function for frequency bands higher than the second and third frequency bands, low-pass filters 54 and 55 are required in the second signal path connecting the common terminal 100 and the input / output terminal 120. On the other hand, since filter 53 is a bandpass filter that uses the third frequency band as its passband, its attenuation function for the first frequency band is higher than that of filter 52 (the attenuation in the first frequency band is larger). Therefore, if high-pass filters 56 and 57 are configured in the third signal path connecting the common terminal 100 and the input / output terminal 130, the attenuation function for the first frequency band becomes excessive (overkill). Similarly, if low-pass filters 54 and 55 are configured in the third signal path connecting the common terminal 100 and the input / output terminal 130, the attenuation function for frequency bands higher than the second and third frequency bands becomes excessive (overkill).

[0139] Figure 7 This is a circuit diagram of the multiplexer 600A in Comparative Example 2. The multiplexer 600A shown in the diagram includes a common terminal 100, input / output terminals 110, 120, and 130, filters 51, 52, and 53, a high-pass filter 601, and a low-pass filter 602. Compared to the multiplexer 5A in Modified Example 3, the multiplexer 600A in Comparative Example 2 has different pass characteristics for the high-pass filter 601 and the low-pass filter 602. Furthermore, it differs in that a low-pass filter 55 and a high-pass filter 57 are not configured after filter 52. Hereinafter, for the multiplexer 600A in Comparative Example 2, descriptions of points identical to those in the multiplexer 5A in Modified Example 3 will be omitted, and the description will focus on the differences.

[0140] The high-pass filter 601 includes inductors 84a and 84e, and capacitors 89a and 89g. A parallel connection circuit of capacitor 89g and inductor 84e is connected in series in the signal path connecting common terminal 100 and node n1. Capacitor 89a is connected in series in the signal path connecting common terminal 100 and node n1. Inductor 84a is connected between the node on the signal path connecting common terminal 100 and node n1 and ground. The high-pass filter 601, through this structure, has a high-pass function.

[0141] The low-pass filter 602 includes an inductor 84c and capacitors 89c, 89h, and 89j. A parallel connection circuit of inductor 84c and capacitor 89c is connected in series on the signal path connecting common terminal 100 and node n1. Capacitors 89h and 89j are respectively connected between the node and ground on the signal path connecting common terminal 100 and node n1. The low-pass filter 602 thus provides a low-pass function.

[0142] Furthermore, the high-pass filter 601 has the same pass characteristics as the series connection circuit of the high-pass filters 56 and 57 in the multiplexer 5A of Modified Example 3. That is, the attenuation in the first frequency band of the high-pass filter 601 is greater than the attenuation in the first frequency band of the high-pass filter 56, and also greater than the attenuation in the first frequency band of the high-pass filter 57. On the other hand, the insertion loss in the second and third frequency bands of the high-pass filter 601 is greater than the insertion loss in the second and third frequency bands of the high-pass filter 56, and also greater than the insertion loss in the second and third frequency bands of the high-pass filter 57.

[0143] Furthermore, the low-pass filter 602 has the same pass characteristics as the series connection circuit of the low-pass filter 54 and low-pass filter 55 in the multiplexer 5A of Modified Example 3. That is, the insertion loss in the second and third frequency bands of the low-pass filter 602 is greater than the insertion loss in the second and third frequency bands of the low-pass filter 54, and is also greater than the insertion loss in the second and third frequency bands of the low-pass filter 55.

[0144] Based on the above-described structure of the multiplexer 600A in Comparative Example 2, the high-pass filter 601 ensures isolation between filter 51, filter 52, and filter 53. Here, as... Figure 6C As shown, the filter 52 has a low attenuation function in the first frequency band (the attenuation in the first frequency band is small), therefore a high-pass filter 601 is needed in the second signal path connecting the common terminal 100 and the input / output terminal 120. On the other hand, as Figure 6CAs shown, filter 53 has a higher attenuation capability in the first frequency band compared to filter 52 (the attenuation amount in the first frequency band is larger). Therefore, if a high-pass filter 601 is configured on the third signal path connecting the common terminal 100 and the input / output terminal 130, the attenuation capability in the first frequency band becomes excessive (overkill). Consequently, the transmission loss in the third signal path deteriorates due to the configuration of the high-pass filter 601. In other words, because there is a difference in the required attenuation amount in the first frequency band between the two filters 52 and 53 commonly connected to the high-pass filter 601, the transmission loss of the third signal path with filter 53 configured deteriorates.

[0145] In contrast, according to the structure of the multiplexer 5A in this modified example, a low-pass filter 54 and a high-pass filter 56 are connected between filters 52 and 53 and the common terminal 100, and a low-pass filter 55 and a high-pass filter 57 are connected to the other end of filter 52. That is, the filter functions that allow the second and third frequency bands to pass through and attenuate the first frequency band are divided and arranged in the pre-stage (between the common terminal 100 and filters 52 and 53) and the post-stage (between filter 52 and input / output terminal 120) of filters 52 and 53. Here, the high-pass filter 56 has the function of shifting the impedance in the first frequency band when viewing filter 52 from the common terminal 100 and the impedance in the first frequency band when viewing filter 53 from the common terminal 100 towards the open-circuit side. In other words, the high-pass filter 56 has the function of increasing the reflection coefficient in the first frequency band of the second and third signal paths. Furthermore, the high-pass filter 56 has the function of increasing the attenuation in the first frequency band of the second and third signal paths. On the other hand, the high-pass filter 57 has the function of increasing the reflection coefficient in the first frequency band of the second and third signal paths. Additionally, the high-pass filter 57 has the function of increasing the attenuation in the first frequency band of the second signal path. Furthermore, the high-pass filter 57 also functions as an impedance matching circuit disposed after the filter 52. Moreover, in terms of increasing the reflection coefficient in the first frequency band when viewing filters 52 and 53 from the common terminal 100, the high-pass filter 57 is less effective than the high-pass filter 56. This is because the high-pass filter, which is more closely connected to the common terminal 100, contributes more to increasing the reflection coefficient in the first frequency band.

[0146] On the other hand, low-pass filter 54 and low-pass filter 55 have the function of increasing the attenuation of the second signal path and the third signal path at higher frequencies than the first frequency band, the second frequency band and the third frequency band.

[0147] In other words, by configuring the high-pass filter 56 before the filters 52 and 53, the isolation between the filter 51 and the filters 52 and 53 can be fully ensured.

[0148] Figure 8 This is a graph comparing the transmission characteristics of the third signal path in Modified Example 3 and Comparative Example 2. The graph shows the transmission characteristics of the third signal path (common terminal 100 – input / output terminal 130) in the multiplexer 5A of Modified Example 3 and the third signal path (common terminal 100 – input / output terminal 130) in the multiplexer 600A of Comparative Example 2. As shown in the graph, it can be seen that the insertion loss in the third frequency band (2400-2483MHz) of the multiplexer 5A of Modified Example 3 is less than the insertion loss in the third frequency band (2400-2483MHz) of the multiplexer 600A of Comparative Example 2. This is because, in the multiplexer 5A of Modified Example 3, compared to the multiplexer 600A of Comparative Example 2, the transmission loss of the third signal path can be reduced by the amount of insertion loss of the high-pass filter 57 and the low-pass filter 55. In other words, it ensures isolation between filter 51 and filters 52 and 53, and sufficiently ensures attenuation in the first frequency band of the second and third signal paths, reducing transmission loss in the third signal path. Furthermore, since the low-pass filter 55 and high-pass filter 57 are positioned after filter 52, the circuit elements constituting the low-pass filter 55 and high-pass filter 57 can also serve as impedance matching elements for filter 52 and the circuit elements connected to the stage following filter 52. That is, in the multiplexer 5A of Modified Example 3, it is not necessary to separately configure an impedance matching circuit after filter 52. Therefore, the transmission loss of the multiplexer 5A is reduced, and the number of circuit elements can be reduced to achieve miniaturization.

[0149] Furthermore, in each of the multiplexers in Modified Example 1 (multiplexer 2), Modified Example 2 (multiplexer 3), and Modified Example 3 (multiplexer 5), the first frequency band (communication band A) is, for example, a low frequency band (617-960MHz), the second frequency band (communication band B) is, for example, a mid-low frequency band (1427.9-1510.9MHz) and a mid-high frequency band (1710-2690MHz), and the second frequency band (communication band B) is, for example, GNSS L1 (1559.072-1605.92MHz).

[0150] [2.5 Specific structure of the multiplexer 6 in variation 4]

[0151] Figure 9This is a circuit block diagram of the multiplexer 6 in Modification Example 4. The multiplexer 6 includes a common terminal 100, input / output terminals 110, 120, 130, and 140, filters 41, 42, 43, and 61, low-pass filters 44 and 45, and high-pass filters 46 and 47. The multiplexer 6 in Modification Example 4 differs from the multiplexer 4 in Embodiment 2 in that it includes an additional filter 61. Hereinafter, for the multiplexer 6 in this modification example, descriptions of points identical to those in the multiplexer 4 of Embodiment 2 will be omitted, and the description will focus on the differences.

[0152] Filter 61 is an example of the tenth filter, which is a filter that uses the fourth frequency band as the passband.

[0153] Low-pass filter 44 is an example of a sixth filter, which is a low-pass filter that uses the second, third and fourth frequency bands as passbands and the first frequency band as attenuation band.

[0154] High-pass filter 46 is an example of a seventh filter, which is a high-pass filter that uses the first, second, and third frequency bands as passbands and the fourth frequency band as attenuation band.

[0155] Low-pass filter 45 is an example of an eighth filter, which is a low-pass filter that uses the second, third and fourth frequency bands as passbands and the first frequency band as attenuation band.

[0156] High-pass filter 47 is an example of the ninth filter, which is a high-pass filter that uses the first, second, and third frequency bands as passbands and the fourth frequency band as attenuation band.

[0157] Here, the frequencies of the second and third frequency bands are at least partially different. Furthermore, the frequency of the first frequency band does not overlap with the frequencies of the second and third frequency bands, and is located at a higher frequency than the second and third frequency bands. Additionally, the frequency of the fourth frequency band does not overlap with the frequencies of the second and third frequency bands, and is located at a lower frequency than the second and third frequency bands.

[0158] One end of filter 61 is connected to common terminal 100, and the other end of filter 61 is connected to input / output terminal 140 (fourth input / output terminal).

[0159] According to the structure of the multiplexer 6 in this modified example, low-pass filters 44 and 45, which allow the second and third frequency bands to pass through and attenuate the first frequency band, are separately arranged in the pre-stage (between the common terminal 100 and filters 42 and 43) and the post-stage (between filter 42 and input / output terminal 120) of filters 42 and 43, respectively. Here, low-pass filter 44 has the function of shifting the impedance in the first frequency band when viewed from the common terminal 100 and the impedance in the first frequency band when viewed from the common terminal 100 towards the open-circuit side. Furthermore, low-pass filter 44 has the function of increasing the attenuation in the first frequency band of the second and third signal paths. On the other hand, low-pass filter 45 has the function of increasing the reflection coefficient in the first frequency band of the second and third signal paths. Additionally, low-pass filter 45 has the function of increasing the attenuation in the first frequency band of the second signal path. Moreover, low-pass filter 45 also functions as an impedance matching circuit arranged in the post-stage of filter 42.

[0160] Furthermore, according to the structure of the multiplexer 6 in this modified example, high-pass filters 46 and 47, which allow the second and third frequency bands to pass through and attenuate the fourth frequency band, are separately arranged in the pre-stage (between the common terminal 100 and filters 42 and 43) and the post-stage (between filter 42 and input / output terminal 120) of filters 42 and 43, respectively. Here, high-pass filter 46 has the function of shifting the impedance in the fourth frequency band when viewed from the common terminal 100 and the impedance in the fourth frequency band when viewed from the common terminal 100 towards the open-circuit side. Additionally, high-pass filter 46 has the function of increasing the attenuation in the fourth frequency band of the second and third signal paths. On the other hand, high-pass filter 47 has the function of increasing the reflection coefficient in the fourth frequency band of the second and third signal paths. Additionally, high-pass filter 47 has the function of increasing the attenuation in the fourth frequency band of the second signal path. Furthermore, high-pass filter 47 also functions as an impedance matching circuit arranged in the post-stage of filter 42.

[0161] In other words, by placing the low-pass filter 44 before filters 42 and 43, sufficient isolation between filter 41 and filters 42 and 43 can be ensured. Similarly, by placing the high-pass filter 46 before filters 42 and 43, sufficient isolation between filter 61 and filters 42 and 43 can be ensured. Furthermore, since the low-pass filter 44 is placed in the third signal path connecting the common terminal 100 and the input / output terminal 130, but the low-pass filter 45 is not placed, the transmission loss of the third signal path is reduced by the amount of insertion loss of the low-pass filter 45 compared to a multiplexer that places a filter circuit consisting of a series-connected low-pass filter 44 and low-pass filter 45 before filters 42 and 43. Furthermore, since a high-pass filter 46 is configured in the third signal path connecting the common terminal 100 and the input / output terminal 130, but no high-pass filter 47 is configured, the transmission loss of the third signal path can be reduced by the amount of insertion loss of the high-pass filter 47 compared to a multiplexer that configures a filter circuit consisting of a series-connected high-pass filter 46 and a high-pass filter 47 in the preceding stages of filters 42 and 43. In other words, isolation between filters 41 and 42 and 43, as well as isolation between filters 61 and 42 and 43, can be ensured, and the attenuation in the first and fourth frequency bands of the second and third signal paths can be sufficiently ensured, while reducing the transmission loss of the third signal path. Moreover, since the low-pass filter 45 and the high-pass filter 47 are configured after the filter 42, the circuit elements constituting the low-pass filter 45 and the high-pass filter 47 can also serve as impedance matching elements between the filter 42 and the circuit elements connected to the following stages of the filter 42. In other words, in the multiplexer 6 of variant 4, there is no need to separately configure an impedance matching circuit after the filter 42. Therefore, the transmission loss of the multiplexer 6 is reduced, and the number of circuit elements can be reduced to achieve miniaturization.

[0162] (Implementation Method 3)

[0163] In Embodiments 1 and 2, a multiplexer was described that includes a first filter using a first frequency band (communication band A) as the passband, a second filter using a second frequency band (communication band B) as the passband and a third frequency band (communication band C) as the attenuation band, and a third filter using the third frequency band as the passband and the first and second frequency bands as attenuation bands. In contrast, in this embodiment, a multiplexer is described that includes a second filter using the second frequency band (communication band B) as the passband and the third frequency band (communication band C) as the attenuation band, and a third filter using the third frequency band as the passband and the second frequency band as the attenuation band, but does not include a first filter using the first frequency band as the passband.

[0164] [3.1 Structure of Multiplexer 7]

[0165] Figure 10 This is a circuit block diagram of the multiplexer 7 according to Embodiment 3. As shown in the figure, the multiplexer 7 includes a common terminal 100, input / output terminals 120 and 130, filters 12 and 13, and low-pass filters 114 and 115. The multiplexer 7 of Embodiment 3 differs from the multiplexer 1 of Embodiment 1 in that it does not include a filter 11. Hereinafter, for the multiplexer 7 of this embodiment, the points that are the same as those of the multiplexer 1 of Embodiment 1 will be omitted, and the description will focus on the differences.

[0166] Filter 12 is an example of a second filter, which uses the second frequency band as the passband and the third frequency band as the attenuation band. Filter 13 is an example of a third filter, which uses the third frequency band as the passband and the second frequency band as the attenuation band.

[0167] Furthermore, the second frequency band is, for example, a frequency band that includes communication frequency band B, and the third frequency band is, for example, a frequency band that includes communication frequency band C.

[0168] Low-pass filter 114 is an example of a fourth filter, which is a low-pass filter that uses the second and third frequency bands as passbands and uses frequency bands higher than the second and third frequency bands as attenuation bands. Low-pass filter 114 specifically uses the frequency bands of the higher harmonics of the signal in the second frequency band or the higher harmonics of the signal in the third frequency band as attenuation bands.

[0169] Low-pass filter 115 is an example of a fifth filter, which is a low-pass filter that uses the second and third frequency bands as passbands and uses frequency bands higher than the second and third frequency bands as attenuation bands. In addition, low-pass filter 115 has the function of impedance matching with external circuitry connected to input / output terminals 120.

[0170] Here, the frequencies of the second and third frequency bands are at least partially different.

[0171] One end of low-pass filter 114 is connected to common terminal 100, and the other end of low-pass filter 114 is connected to one end of filter 12. The other end of filter 12 is connected to one end of low-pass filter 115, and the other end of low-pass filter 115 is connected to input / output terminal 120. Additionally, one end of filter 13 is connected to the connection node n1 between the other end of low-pass filter 114 and the other end of filter 12, and the other end of filter 13 is connected to input / output terminal 130.

[0172] Figure 11 This is the circuit block diagram of the multiplexer 700 in Comparative Example 3. Figure 11The multiplexer 700 shown includes a common terminal 100, input / output terminals 120 and 130, filters 12 and 13, a low-pass filter 714, and an impedance matching circuit 720. Compared to the multiplexer 7 of Embodiment 3, the multiplexer 700 of Comparative Example 3 has a different pass-through characteristic of the low-pass filter 714. Furthermore, a low-pass filter 115 is not provided after filter 12; instead, an impedance matching circuit 720 is provided. Hereinafter, for the multiplexer 700 of Comparative Example 3, descriptions of points identical to those of the multiplexer 7 of Embodiment 3 will be omitted, and descriptions will focus on the differences.

[0173] Low-pass filter 714 is a low-pass filter that uses the second and third frequency bands as passbands and uses the frequency bands higher than the second and third frequency bands as attenuation bands. Furthermore, the attenuation in the frequency bands higher than the second and third frequency bands of low-pass filter 714 is greater than the attenuation in the frequency bands higher than the second and third frequency bands of low-pass filter 114, and is also greater than the attenuation in the frequency bands higher than the second and third frequency bands of low-pass filter 115. On the other hand, the insertion loss in the second and third frequency bands of low-pass filter 714 is greater than the insertion loss in the second and third frequency bands of low-pass filter 114, and is also greater than the insertion loss in the second and third frequency bands of low-pass filter 115.

[0174] One end of the low-pass filter 714 is connected to the common terminal 100, and the other end of the low-pass filter 714 is connected to one end of the filter 12. The other end of the filter 12 is connected to one end of the impedance matching circuit 720, and the other end of the impedance matching circuit 720 is connected to the input / output terminal 120. In addition, one end of the filter 13 is connected to the connection node n1 between the other end of the low-pass filter 714 and the one end of the filter 12, and the other end of the filter 13 is connected to the input / output terminal 130.

[0175] According to the above-described structure of the multiplexer 700 in Comparative Example 3, the high-order harmonics of the output signal in the second frequency band and the high-order harmonics of the signal in the third frequency band can be suppressed by the low-pass filter 714. Here, since the filter 12 has a lower attenuation function for the frequency bands higher than the second and third frequency bands, the low-pass filter 714 is needed in the second signal path connecting the common terminal 100 and the input / output terminal 120. On the other hand, the filter 13 has a higher attenuation function for the frequency bands higher than the second and third frequency bands compared to the filter 12. Therefore, if the low-pass filter 714 is configured in the third signal path connecting the common terminal 100 and the input / output terminal 130, the attenuation function for the frequency bands higher than the second and third frequency bands becomes excessive (overkill). As a result, the transmission loss in the third signal path deteriorates because the low-pass filter 714 is configured in the third signal path. In other words, due to the difference in the amount of attenuation required for the higher frequency bands than the second and third frequency bands between the two filters 12 and 13 that are commonly connected to the low-pass filter 714, the transmission loss of the third signal path configured with filter 13 deteriorates.

[0176] In contrast, according to the structure of the multiplexer 7 in Embodiment 3, a low-pass filter 114 is connected between filters 12 and 13 and the common terminal 100, and a low-pass filter 115 is connected to the other end of filter 12. That is, the filter functions of allowing the second and third frequency bands to pass through and attenuating frequency bands higher than the second and third frequency bands are divided and arranged in the pre-stage (between the common terminal 100 and filters 12 and 13) and the post-stage (between filter 12 and input / output terminal 120) of filters 12 and 13. The low-pass filter 114 has the function of increasing the attenuation of the second and third signal paths in the frequency bands higher than the second and third frequency bands. Furthermore, the low-pass filter 115 has the function of increasing the attenuation of the second signal path in the frequency bands higher than the second and third frequency bands. Moreover, the low-pass filter 115 also functions as an impedance matching circuit arranged in the post-stage of filter 12.

[0177] By placing the low-pass filter 114 before filters 12 and 13, high-order harmonics of the output second frequency band signal and high-order harmonics of the third frequency band signal can be suppressed. Furthermore, since the low-pass filter 114 is placed in the third signal path connecting the common terminal 100 and the input / output terminal 130, but the low-pass filter 115 is not placed, the transmission loss of the third signal path can be reduced by the amount of insertion loss of the low-pass filter 115 compared to the multiplexer 700 which has the low-pass filter 714 placed before filters 12 and 13. In other words, high-order harmonics of the output second frequency band signal and high-order harmonics of the third frequency band signal can be suppressed, and the attenuation of the second and third signal paths compared to the higher frequency bands of the second and third frequency bands can be sufficiently ensured, while reducing the transmission loss of the third signal path. Moreover, since the low-pass filter 115 is placed after filter 12, the circuit elements constituting the low-pass filter 115 can also serve as impedance matching elements for filter 12 and the circuit elements connected to the stage after filter 12. In other words, in the multiplexer 7 of Embodiment 3, the impedance matching circuit 720 configured in the multiplexer 700 of Comparative Example 3 is not required. Therefore, the transmission loss of the multiplexer 7 is reduced, and the number of circuit elements can be reduced to achieve miniaturization.

[0178] [Circuit structure of multiplexer 8 in variation 5]

[0179] Figure 12 This is a circuit block diagram of the multiplexer 8 in Modification Example 5. The multiplexer 8 includes a common terminal 100, input / output terminals 120 and 130, filters 22 and 23, and high-pass filters 124 and 125. The multiplexer 8 in Modification Example 5 differs from the multiplexer 7 in Embodiment 3 in that it is equipped with a high-pass filter instead of a low-pass filter. Hereinafter, for the multiplexer 8 in Modification Example 5, descriptions of points identical to those in the multiplexer 7 of Embodiment 3 will be omitted, and the description will focus on the differences.

[0180] Filter 22 is an example of a second filter, which uses the second frequency band as the passband and the third frequency band as the attenuation band. Filter 23 is an example of a third filter, which uses the third frequency band as the passband and the second frequency band as the attenuation band.

[0181] High-pass filter 124 is an example of a fourth filter, which is a high-pass filter that uses the second and third frequency bands as the passband and the frequency bands that are lower than the second and third frequency bands as the attenuation band.

[0182] The high-pass filter 125 is an example of a fifth-generation filter. It is a high-pass filter that uses the second and third frequency bands as the passband and the frequency bands lower than the second and third frequency bands as the attenuation band. In addition, the high-pass filter 125 has the function of impedance matching with external circuits connected to the input / output terminals 120.

[0183] Here, the frequencies of the second and third frequency bands are at least partially different.

[0184] One end of high-pass filter 124 is connected to common terminal 100, and the other end of high-pass filter 124 is connected to one end of filter 22. The other end of filter 22 is connected to one end of high-pass filter 125, and the other end of high-pass filter 125 is connected to input / output terminal 120. Additionally, one end of filter 23 is connected to the connection node n1 between the other end of high-pass filter 124 and the other end of filter 22, and the other end of filter 23 is connected to input / output terminal 130.

[0185] According to the structure of the multiplexer 8 in this modified example, a high-pass filter 124 is connected between filters 22 and 23 and the common terminal 100, and a high-pass filter 125 is connected to the other end of filter 22. That is, the filter functions of allowing the second and third frequency bands to pass through and attenuating frequency bands lower than the second and third frequency bands are divided and arranged in the pre-stage (between the common terminal 100 and filters 22 and 23) and the post-stage (between filter 22 and input / output terminal 120) of filters 22 and 23. The high-pass filter 124 has the function of increasing the attenuation of the second and third signal paths in the frequency bands lower than the second and third frequency bands. Furthermore, the high-pass filter 125 has the function of increasing the attenuation of the second signal path in the frequency bands lower than the second and third frequency bands. Moreover, the high-pass filter 125 also functions as an impedance matching circuit arranged in the post-stage of filter 22.

[0186] In other words, since a high-pass filter 124 is configured in the third signal path connecting the common terminal 100 and the input / output terminal 130, but no high-pass filter 125 is configured, the transmission loss of the third signal path can be reduced by the amount of insertion loss of the high-pass filter 125. That is, the attenuation of the second and third signal paths compared to the lower frequency bands of the second and third frequency bands can be sufficiently ensured, and the transmission loss of the third signal path can be reduced. Furthermore, since the high-pass filter 125 is configured after the filter 22, the circuit elements constituting the high-pass filter 125 can also serve as impedance matching elements for the filter 22 and the circuit elements connected to the subsequent stage of the filter 22. That is, in this modified multiplexer 8, no additional impedance matching circuit is required. Therefore, the transmission loss of the multiplexer 8 is reduced, and the number of circuit elements can be reduced to achieve miniaturization.

[0187] [Circuit structure of multiplexer 9 in variation 6 of 3.3]

[0188] Figure 13 This is a circuit block diagram of the multiplexer 9 in Modification Example 6. The multiplexer 9 includes a common terminal 100, input / output terminals 120 and 130, filters 32 and 33, and low-pass filters 134 and 135. The multiplexer 9 in Modification Example 6 differs from the multiplexer 7 in Embodiment 3 in that filter 32 is a band-stop filter instead of a band-pass filter. Hereinafter, for the multiplexer 9 in Modification Example 6, descriptions of points identical to those in the multiplexer 7 of Embodiment 3 will be omitted, and the description will focus on the differences.

[0189] Filter 32 is an example of a second filter, which is a band-stop filter that uses the third frequency band as the attenuation band. Filter 33 is an example of a third filter, which is a filter that uses the third frequency band as the passband and the second frequency band as the attenuation band. Filters 32 and 33, using the third frequency band as the attenuation band and passband respectively, constitute an extractor.

[0190] Low-pass filter 134 is an example of a fourth filter, which is a low-pass filter that uses the second and third frequency bands as passbands and uses frequency bands higher than the second and third frequency bands as attenuation bands. Low-pass filter 134 specifically uses the frequency bands of the higher harmonics of the signal in the second frequency band or the higher harmonics of the signal in the third frequency band as attenuation bands.

[0191] Low-pass filter 135 is an example of a fifth type of filter, which uses the second and third frequency bands as passbands and uses frequency bands higher than the second and third frequency bands as attenuation bands. Furthermore, low-pass filter 135 has the function of impedance matching with external circuitry connected to input / output terminals 120.

[0192] Here, the frequencies of the second and third frequency bands are at least partially different.

[0193] One end of low-pass filter 134 is connected to common terminal 100, and the other end of low-pass filter 134 is connected to one end of filter 32. The other end of filter 32 is connected to one end of low-pass filter 135, and the other end of low-pass filter 135 is connected to input / output terminal 120. Additionally, one end of filter 33 is connected to the connection node n1 between the other end of low-pass filter 134 and the first end of filter 32, and the other end of filter 33 is connected to input / output terminal 130.

[0194] According to the structure of the multiplexer 9 in this modified example, a low-pass filter 134 is connected between filters 32 and 33 and the common terminal 100, and a low-pass filter 135 is connected to the other end of filter 32. That is, the filter functions of allowing the second and third frequency bands to pass and attenuating the frequency bands higher than the second and third frequency bands are divided and arranged in the pre-stage (between the common terminal 100 and filters 32 and 33) and the post-stage (between filter 32 and input / output terminal 120) of filters 32 and 33. The low-pass filter 134 has the function of increasing the attenuation of the second and third signal paths in the frequency bands higher than the second and third frequency bands. Furthermore, the low-pass filter 135 has the function of increasing the attenuation of the second signal path in the frequency bands higher than the second and third frequency bands. Moreover, the low-pass filter 135 also functions as an impedance matching circuit arranged in the post-stage of filter 32.

[0195] By configuring the low-pass filter 134 before filters 32 and 33, high-order harmonics of the output second frequency band signal and high-order harmonics of the third frequency band signal can be suppressed. Furthermore, since the low-pass filter 134 is configured in the third signal path connecting the common terminal 100 and the input / output terminal 130, but not the low-pass filter 135, compared to a multiplexer that configures a filter circuit consisting of a series-connected low-pass filter 134 and low-pass filter 135 before filters 32 and 33, the transmission loss of the third signal path can be reduced by the amount of insertion loss of the low-pass filter 135. In other words, high-order harmonics of the output second frequency band signal and high-order harmonics of the third frequency band signal can be suppressed, and the attenuation of the second and third signal paths compared to the higher frequency bands of the second and third frequency bands can be sufficiently ensured, while reducing the transmission loss of the third signal path. Furthermore, since the low-pass filter 135 is positioned after the filter 32, the circuit elements constituting the low-pass filter 135 can also serve as impedance matching elements for the filter 32 and the circuit elements connected to the subsequent stage of the filter 32. In other words, in this modified example of the multiplexer 9, no additional impedance matching circuit is required. Therefore, the transmission loss of the multiplexer 9 is reduced, and the number of circuit elements can be reduced to achieve miniaturization.

[0196] [Circuit structure of multiplexer 10 in variation 7 of 3.4]

[0197] Furthermore, as a modification of the multiplexer 9 of Modification Example 6, a multiplexer in which the frequency relationship between the second and third frequency bands is different from that of the multiplexer 9 of Modification Example 6, and a high-pass filter is provided instead of a low-pass filter, is also included in the present invention.

[0198] Figure 14 This is a circuit block diagram of the multiplexer 10 of Modified Example 7. The multiplexer 10 of Modified Example 7 includes a common terminal 100, input / output terminals 120 and 130, filters 32 and 33, and high-pass filters 136 and 137. The frequencies of the second frequency band and the third frequency band are at least partially different.

[0199] High-pass filter 136 is an example of a fourth filter, which is a high-pass filter that uses the second and third frequency bands as the passband and the frequency bands that are lower than the second and third frequency bands as the attenuation band.

[0200] High-pass filter 137 is an example of a fifth type of filter, which uses the second and third frequency bands as the passband and the frequency bands lower than the second and third frequency bands as the attenuation band. Furthermore, high-pass filter 137 has the function of impedance matching with external circuitry connected to input / output terminals 120.

[0201] Therefore, the transmission loss of the third signal path can be reduced by the amount of insertion loss of the high-pass filter 137 configured in the subsequent stage, and the circuit elements constituting the high-pass filter 137 configured in the subsequent stage can also serve as impedance matching elements connected to the subsequent stage of the filter 32. Thus, the transmission loss of the multiplexer 10 is reduced, and the number of circuit elements can be reduced to achieve miniaturization.

[0202] [Circuit structure of multiplexer 20 in variation 8 of 3.5]

[0203] Figure 15 This is a circuit block diagram of the multiplexer 20 in Modified Example 8. The multiplexer 20 in Modified Example 8 includes a common terminal 100, input / output terminals 120 and 130, filters 42 and 43, low-pass filters 144 and 145, and high-pass filters 146 and 147. The multiplexer 20 in Modified Example 8 differs from the multiplexer 7 in Embodiment 3 in that it has a structure that separately configures the low-pass and high-pass filters in the pre-stage and post-stage of filter 42. Hereinafter, for the multiplexer 20 in Modified Example 8, descriptions of points identical to those in the multiplexer 7 of Embodiment 3 will be omitted, and the description will focus on the differences.

[0204] Filter 42 is an example of a second filter, which is a band-stop filter that uses the third frequency band as the attenuation band. Filter 43 is an example of a third filter, which is a filter that uses the third frequency band as the passband and the second frequency band as the attenuation band. Filters 42 and 43, using the third frequency band as the attenuation band and passband respectively, constitute an extractor.

[0205] Low-pass filter 144 is an example of a sixth filter, which is a low-pass filter that uses the second and third frequency bands as passbands.

[0206] High-pass filter 146 is an example of a seventh filter, which is a high-pass filter that uses the second and third frequency bands as passbands.

[0207] Low-pass filter 145 is an example of an eighth filter, which is a low-pass filter that uses the second and third frequency bands as passbands.

[0208] High-pass filter 147 is an example of the ninth filter, which is a high-pass filter that uses the second and third frequency bands as passbands.

[0209] Here, the frequencies of the second and third frequency bands are at least partially different.

[0210] One end of low-pass filter 144 is connected to common terminal 100, and the other end of low-pass filter 144 is connected to one end of high-pass filter 146. The other end of high-pass filter 146 is connected to one end of filter 42. The other end of filter 42 is connected to one end of low-pass filter 145, and the other end of low-pass filter 145 is connected to one end of high-pass filter 147. The other end of high-pass filter 147 is connected to input / output terminal 120. Additionally, one end of filter 43 is connected to the connection node n1 between the other end of high-pass filter 146 and one end of filter 42, and the other end of filter 43 is connected to input / output terminal 130.

[0211] Figure 16 This is a diagram showing the first example of the circuit structure of the multiplexer 20 in Modified Example 8. Modified Example 8, multiplexer 20A, discloses a specific example of the circuit structure of the multiplexer 20.

[0212] Since filter 42 has the same structure as filter 42 of multiplexer 4A in embodiment 2, detailed description is omitted here.

[0213] Since filter 43 has the same structure as filter 43 of multiplexer 4A in Embodiment 2, detailed description is omitted here.

[0214] The low-pass filter 144 has an inductor 83b and a capacitor 88a. The series connection circuit of the inductor 83b and the capacitor 88a is connected between the node and ground on the signal path connecting the common terminal 100 and node n1. That is, the low-pass filter 144 mainly has a low-pass function through the capacitor 88a arranged in the parallel arm.

[0215] The high-pass filter 146 includes an inductor 83e and capacitors 88d and 88e. Capacitor 88d is connected in series on the signal path connecting the common terminal 100 and node n1. The series connection circuit of inductor 83e and capacitor 88e is connected between the node on the signal path connecting the common terminal 100 and node n1 and ground. The high-pass filter 146 thus provides a high-pass function.

[0216] The low-pass filter 145 includes an inductor 83d and capacitors 88b and 88c. A parallel connection circuit of inductor 83d and capacitor 88b is connected in series in the second signal path connecting filter 42 and input / output terminal 120. Capacitor 88c is connected between a node on the second signal path and ground. In other words, the low-pass filter 145 primarily provides low-pass functionality through the inductor 83d in the series arm and the capacitor 88c in the parallel arm.

[0217] Furthermore, the high-pass filter 147 is not configured in the multiplexer 20A.

[0218] In the multiplexer 20A of this modified example, the second frequency band (communication band B) is, for example, a mid-to-high frequency band, and the third frequency band is, for example, WLAN.

[0219] According to the structure of the multiplexer 20A in this modified example, a low-pass filter 144 and a high-pass filter 146 are connected between filters 42 and 43 and the common terminal 100, and a low-pass filter 145 is connected to the other end of filter 42. That is, the low-pass filter function, which allows the second and third frequency bands to pass and attenuates the frequency bands higher than the second and third frequency bands, is divided and configured in the pre-stage (between the common terminal 100 and filters 42 and 43) and the post-stage (between the filter 42 and the input / output terminal 120) of filters 42 and 43.

[0220] Low-pass filter 144 increases the attenuation of the second and third signal paths in the higher frequency bands of the second and third frequency bands. Low-pass filter 145 also increases the attenuation of the second signal path in the higher frequency bands of the second and third frequency bands. Furthermore, low-pass filter 145 also functions as an impedance matching circuit disposed after filter 42.

[0221] On the other hand, the high-pass filter 146 has the function of increasing the attenuation of the second signal path and the third signal path compared to the lower frequency side of the second and third frequency bands.

[0222] In other words, since a low-pass filter 144 is configured on the third signal path connecting the common terminal 100 and the input / output terminal 130, but no low-pass filter 145 is configured, compared to a multiplexer that has a filter circuit consisting of a series-connected low-pass filter 144 and a low-pass filter 145 configured before filters 42 and 43, the transmission loss of the third signal path can be reduced by the amount of insertion loss of the low-pass filter 145. That is, the attenuation of the second and third signal paths compared to the higher frequency bands of the second and third frequency bands can be sufficiently ensured, and the transmission loss of the third signal path can be reduced. Furthermore, since the low-pass filter 145 is configured after filter 42, the circuit elements constituting the low-pass filter 145 can also serve as impedance matching elements for filter 42 and the circuit elements connected after filter 42. That is, in the multiplexer 20A of Modified Example 8, it is not necessary to configure a separate impedance matching circuit after filter 42. Therefore, the transmission loss of the multiplexer 20A is reduced, and the number of circuit elements can be reduced to achieve miniaturization.

[0223] Figure 17This is a second example of the circuit structure of the multiplexer 20 in Modified Example 8. Modified Example 8, multiplexer 20B, discloses a specific example of the circuit structure of the multiplexer 20.

[0224] Since filter 42 has the same structure as filter 42 of multiplexer 4A in embodiment 2, detailed description is omitted here.

[0225] Since filter 43 has the same structure as filter 43 of multiplexer 4A in Embodiment 2, detailed description is omitted here.

[0226] Since the low-pass filter 144 has the same structure as the low-pass filter 144 of the multiplexer 20A, detailed descriptions are omitted here.

[0227] The high-pass filter 146 includes an inductor 83c. The inductor 83c is connected between a node and ground on the signal path connecting the common terminal 100 and node n1. The high-pass filter 146 thus has a high-pass function through the above structure.

[0228] Since the low-pass filter 145 has the same structure as the low-pass filter 145 of the multiplexer 20A, detailed descriptions are omitted here.

[0229] Since the high-pass filter 147 has the same structure as the high-pass filter 47 of the multiplexer 4A in Embodiment 2, detailed description is omitted here.

[0230] In the multiplexer 20B of this modified example, the second frequency band (communication band B) is, for example, a mid-to-high frequency band, and the third frequency band is, for example, a WLAN.

[0231] According to the structure of the multiplexer 20B in this modified example, a low-pass filter 144 and a high-pass filter 146 are connected between filters 42 and 43 and the common terminal 100, and a low-pass filter 145 and a high-pass filter 147 are connected to the other end of filter 42. That is, the low-pass filter function, which allows the second and third frequency bands to pass through and attenuates frequency bands higher than the second and third frequency bands, is divided and arranged in the pre-stage and post-stage of filters 42 and 43. Similarly, the high-pass filter function, which allows the second and third frequency bands to pass through and attenuates frequency bands lower than the second and third frequency bands, is divided and arranged in the pre-stage and post-stage of filters 42 and 43. Here, the low-pass filter 144 has the function of increasing the reflection coefficient in the frequency bands of the second and third signal paths that are higher than the second and third frequency bands. Furthermore, the low-pass filter 144 has the function of increasing the attenuation in the frequency bands of the second and third signal paths that are higher than the second and third frequency bands. On the other hand, the low-pass filter 145 has the function of increasing the reflection coefficient in the frequency bands of the second and third signal paths that are higher than the second and third frequency bands. Additionally, the low-pass filter 145 has the function of increasing the attenuation in the frequency bands of the second signal path that are higher than the second and third frequency bands. Furthermore, the low-pass filter 145 also functions as an impedance matching circuit disposed after the filter 42. Moreover, in terms of increasing the reflection coefficient in the frequency bands of the second and third frequency bands that are higher than the second and third frequency bands when viewed from the common terminal 100, the low-pass filter 145 is less effective than the low-pass filter 144. This is because the low-pass filter connected more closely to the common terminal 100 contributes more to increasing the reflection coefficient in the frequency bands that are higher than the second and third frequency bands.

[0232] On the other hand, high-pass filters 146 and 147 have the function of increasing the attenuation of the second signal path and the third signal path compared to the lower frequency side of the second and third frequency bands.

[0233] In other words, a low-pass filter 144 is configured on the third signal path connecting the common terminal 100 and the input / output terminal 130, but a low-pass filter 145 is not configured. Similarly, a high-pass filter 146 is configured on the third signal path, but a high-pass filter 147 is not configured. Therefore, compared to a multiplexer that has low-pass filters 144 and 145, and high-pass filters 146 and 147 configured before filters 42 and 43, the transmission loss of the third signal path can be reduced by the amount of insertion loss of low-pass filters 145 and 147. In other words, the attenuation of the second and third signal paths in the higher frequency bands of the second and third frequency bands and in the lower frequency bands of the second and third frequency bands can be sufficiently ensured, and the transmission loss of the third signal path is reduced. Furthermore, since the low-pass filter 145 and the high-pass filter 147 are positioned after the filter 42, the circuit elements constituting the low-pass filter 145 and the high-pass filter 147 can also serve as impedance matching elements for the filter 42 and the circuit elements connected to the stage following the filter 42. In other words, in the multiplexer 20B of Modified Example 8, it is not necessary to separately configure an impedance matching circuit after the filter 42. Therefore, the transmission loss of the multiplexer 20B is reduced, and the number of circuit elements can be reduced to achieve miniaturization.

[0234] (Effects, etc.)

[0235] The multiplexer 1 of the present invention comprises: a first filter that uses a first frequency band as a passband; a second filter that uses a second frequency band as a passband and a third frequency band as an attenuation band; a third filter that uses a third frequency band as a passband and both the first and second frequency bands as attenuation bands; a fourth filter that uses both the second and third frequency bands as passbands and the first frequency band as an attenuation band; and a fifth filter that uses both the second and third frequency bands as passbands and the first frequency band as an attenuation band, wherein the frequencies of the second and third frequency bands are at least partially different, the frequency of the first frequency band does not overlap with the frequencies of the second and third frequency bands, one end of the first filter is connected to a common terminal, the other end of the first filter is connected to a first input / output terminal, one end of the fourth filter is connected to a common terminal, the other end of the fourth filter is connected to one end of the second filter, the other end of the second filter is connected to one end of the fifth filter, the other end of the fifth filter is connected to a second input / output terminal, one end of the third filter is connected to the connection node between the other end of the fourth filter and the one end of the second filter, and the other end of the third filter is connected to a third input / output terminal.

[0236] Therefore, the fourth and fifth filters, which allow the second and third frequency bands to pass through and attenuate the first frequency band, are separately configured before and after the second and third filters, respectively. In other words, the configuration of the fourth filter ensures sufficient isolation between the first filter and the second and third filters. Furthermore, since the fourth filter is configured on the third signal path through which the third frequency band signal passes, but not the fifth filter, the transmission loss of the third signal path is reduced by the amount of the fifth filter's insertion loss compared to a multiplexer with a filter circuit consisting of the fourth and fifth filters connected in series before the second and third filters. That is, isolation between the first filter and the second and third filters is ensured, and the transmission loss of the third signal path is reduced. Moreover, since the fifth filter is configured after the second filter, it can also serve as an impedance matching element between the second filter and the circuit components connected to the stage following the second filter. Therefore, the transmission loss of the multiplexer is reduced, and the number of circuit components can be reduced to achieve miniaturization.

[0237] Alternatively, in multiplexer 1, the frequencies of the second and third frequency bands may not overlap, and the first frequency band may be located at a higher frequency than the second and third frequency bands. Filter 11 uses the second and third frequency bands as attenuation bands, filter 12 uses the first and third frequency bands as attenuation bands, low-pass filter 14 uses the second and third frequency bands as passbands and the first frequency band as attenuation bands, and low-pass filter 15 uses the second and third frequency bands as passbands and the first frequency band as attenuation bands.

[0238] Therefore, by placing the low-pass filter 14 before filters 12 and 13, sufficient isolation between filter 11 and filters 12 and 13 can be ensured. Furthermore, since the low-pass filter 14 is placed on the third signal path connecting the common terminal 100 and the input / output terminal 130, but the low-pass filter 15 is not placed, compared to the multiplexer 500 which has a filter circuit (low-pass filter 514) formed by connecting the low-pass filters 14 and 15 in series placed before filters 12 and 13, the transmission loss of the third signal path can be reduced by the amount of insertion loss of the low-pass filter 15. In other words, isolation between filter 11 and filters 12 and 13 is ensured, and the attenuation in the first frequency band of the second and third signal paths can be sufficiently ensured, reducing the transmission loss of the third signal path. Moreover, since the low-pass filter 15 is placed after filter 12, the circuit elements constituting the low-pass filter 15 can also serve as impedance matching elements between filter 12 and the circuit elements connected to the stage after filter 12. Therefore, the transmission loss of multiplexer 1 is reduced, and the number of circuit elements can be reduced to achieve miniaturization.

[0239] Alternatively, in multiplexer 2, the frequencies of the second and third frequency bands may not overlap, and the first frequency band may be located at a lower frequency than the second and third frequency bands. Filter 11 uses the second and third frequency bands as attenuation bands, filter 12 uses the first and third frequency bands as attenuation bands, high-pass filter 24 uses the second and third frequency bands as passbands and the first frequency band as attenuation bands, and high-pass filter 25 uses the second and third frequency bands as passbands and the first frequency band as attenuation bands.

[0240] Therefore, by placing the high-pass filter 24 before filters 22 and 23, sufficient isolation between filter 21 and filters 22 and 23 can be ensured. Furthermore, since the high-pass filter 24 is placed on the third signal path connecting the common terminal 100 and the input / output terminal 130, but not the high-pass filter 25, the transmission loss of the third signal path is reduced, thus minimizing the insertion loss of the high-pass filter 25. Moreover, since the high-pass filter 25 is placed after filter 22, the circuit elements constituting the high-pass filter 25 can also serve as impedance matching elements for filter 22 and the circuit elements connected to the stage following filter 22. Therefore, the transmission loss of the multiplexer 2 is reduced, and the number of circuit elements can be reduced to achieve miniaturization.

[0241] In addition, in multiplexer 3, the second frequency band may include the third frequency band, and the first frequency band is located at a higher frequency than the second and third frequency bands. Filter 31 uses the second and third frequency bands as attenuation bands, filter 32 is a band-stop filter that uses the third frequency band as an attenuation band, low-pass filter 34 uses the second and third frequency bands as passbands and the first frequency band as an attenuation band, and low-pass filter 35 uses the second and third frequency bands as passbands and the first frequency band as an attenuation band.

[0242] Therefore, by placing the low-pass filter 34 before filters 32 and 33, sufficient isolation between filters 31 and 32 and 33 can be ensured. Furthermore, since the low-pass filter 35 is not placed on the third signal path connecting the common terminal 100 and the input / output terminal 130, the transmission loss of the third signal path is reduced, thus minimizing the insertion loss of the low-pass filter 35. Moreover, since the low-pass filter 35 is placed after filter 32, the circuit elements constituting the low-pass filter 35 can also serve as impedance matching elements between filter 32 and the circuit elements connected to the stage following filter 32. Therefore, the transmission loss of the multiplexer 3 is reduced, and the number of circuit elements can be reduced to achieve miniaturization.

[0243] In addition, in multiplexer 3, the second frequency band may include the third frequency band, the first frequency band is located at a lower frequency than the second and third frequency bands, filter 31 uses the second and third frequency bands as attenuation bands, filter 32 is a band-stop filter that uses the third frequency band as an attenuation band, low-pass filter 34 is a fourth filter with high-pass filter function, and low-pass filter 35 is a fifth filter with high-pass filter function.

[0244] Therefore, by placing the fourth filter before filters 32 and 33, sufficient isolation between filter 31 and filters 32 and 33 can be ensured. Furthermore, since the fifth filter is not placed on the third signal path connecting the common terminal 100 and the input / output terminal 130, the transmission loss of the third signal path is reduced by the amount of insertion loss of the fifth filter. Moreover, since the fifth filter is placed after filter 32, the circuit elements constituting the fifth filter can also serve as impedance matching elements between filter 32 and the circuit elements connected to the stage following filter 32. Therefore, the transmission loss of the multiplexer 3 is reduced, and the number of circuit elements can be reduced to achieve miniaturization.

[0245] In addition, in multiplexer 4, the second frequency band may include the third frequency band, and the first frequency band is located at a higher frequency than the second and third frequency bands. Filter 41 uses the second and third frequency bands as attenuation bands, filter 42 is a band-stop filter that uses the third frequency band as an attenuation band, low-pass filter 44 uses the second and third frequency bands as passbands and the first frequency band as an attenuation band, high-pass filter 46 uses the second and third frequency bands as passbands, low-pass filter 45 uses the second and third frequency bands as passbands and the first frequency band as an attenuation band, and high-pass filter 47 uses the second and third frequency bands as passbands.

[0246] Therefore, by placing the low-pass filter 44 before filters 42 and 43, sufficient isolation between filters 41 and 42 and 43 can be ensured. Furthermore, since the low-pass filter 45 is not placed on the third signal path connecting the common terminal 100 and the input / output terminal 130, the transmission loss of the third signal path is reduced, thus minimizing the insertion loss of the low-pass filter 45. Moreover, since the low-pass filter 45 and high-pass filter 47 are placed after filter 42, the circuit elements constituting the low-pass filter 45 and high-pass filter 47 can also serve as impedance matching elements for filters 42 and the circuit elements connected to the stage following filter 42. Therefore, the transmission loss of the multiplexer 4 is reduced, and the number of circuit elements can be reduced to achieve miniaturization.

[0247] Alternatively, in multiplexer 5, the second frequency band may include the third frequency band, and the first frequency band may be located at a lower frequency than the second and third frequency bands. Filter 51 uses the second and third frequency bands as attenuation bands, filter 52 is a band-stop filter that uses the third frequency band as an attenuation band, high-pass filter 56 uses the second and third frequency bands as passbands and the first frequency band as an attenuation band, low-pass filter 54 uses the second and third frequency bands as passbands, high-pass filter 57 uses the second and third frequency bands as passbands and the first frequency band as an attenuation band, and low-pass filter 55 uses the second and third frequency bands as passbands.

[0248] Therefore, by placing the high-pass filter 56 before filters 52 and 53, sufficient isolation between filters 51 and 52 and 53 can be ensured. Furthermore, since the high-pass filter 57 is not placed on the third signal path connecting the common terminal 100 and the input / output terminal 130, the transmission loss of the third signal path is reduced, thus minimizing the insertion loss of the high-pass filter 57. Moreover, since the low-pass filter 55 and high-pass filter 57 are placed after filter 52, the circuit elements constituting the low-pass filter 55 and high-pass filter 57 can also serve as impedance matching elements for filter 52 and the circuit elements connected to the stage following filter 52. Therefore, the transmission loss of the multiplexer 5 is reduced, and the number of circuit elements can be reduced to achieve miniaturization.

[0249] In addition, the multiplexer 6, compared to the multiplexer 4, may also have input / output terminals 140 and a filter 61 that uses the fourth frequency band as a passband. The frequency of the fourth frequency band does not overlap with the frequencies of the second and third frequency bands and is located on the lower frequency side than the second and third frequency bands. One end of the filter 61 is connected to the common terminal 100, and the other end of the filter 61 is connected to the input / output terminal 140. The low-pass filter 44 uses the second, third, and fourth frequency bands as passbands and the first frequency band as an attenuation band. The high-pass filter 46 uses the first, second, and third frequency bands as passbands and the fourth frequency band as an attenuation band. The low-pass filter 45 uses the second, third, and fourth frequency bands as passbands and the first frequency band as an attenuation band. The high-pass filter 47 uses the first, second, and third frequency bands as passbands.

[0250] Therefore, by placing the low-pass filter 44 before filters 42 and 43, sufficient isolation between filters 41 and 42 and 43 can be ensured. Similarly, by placing the high-pass filter 46 before filters 42 and 43, sufficient isolation between filters 61 and 42 and 43 can be ensured. Furthermore, since the low-pass filter 45 and high-pass filter 47 are not placed on the third signal path connecting the common terminal 100 and the input / output terminal 130, the transmission loss of the third signal path is reduced, thus minimizing the insertion loss of the low-pass filter 45 and high-pass filter 47. Moreover, since the low-pass filter 45 and high-pass filter 47 are placed after filter 42, the circuit elements constituting the low-pass filter 45 and high-pass filter 47 can also serve as impedance matching elements between filter 42 and the circuit elements connected to the stage following filter 42. Therefore, the transmission loss of the multiplexer 6 is reduced, and the number of circuit elements can be reduced to achieve miniaturization.

[0251] In addition, the second frequency band can be a mid-to-high frequency band (1710-2370MHz and 2496-2690MHz), and the third frequency band can be WLAN (2400-2483MHz).

[0252] In addition, the first frequency band can be the ultra-high frequency band (3300-5000MHz).

[0253] In addition, the fourth frequency band can be L5 (1164.4-1187.95MHz) of GNSS (Global Navigation Satellite System).

[0254] Alternatively, the first frequency band can be GNSS L5 (1164.4–1187.95 MHz).

[0255] In addition, the communication device 90 includes an antenna 92, an RFIC 91 for processing high-frequency signals transmitted and received by the antenna 92, and the aforementioned multiplexer for transmitting high-frequency signals between the antenna 92 ​​and the RFIC 91.

[0256] Therefore, a communication device 90 that achieves low loss and high isolation can be provided.

[0257] (Other implementation methods)

[0258] The present invention has been described above with examples of embodiments, examples, and modifications, but the present invention is not limited to the above embodiments, examples, and modifications. Other embodiments implemented by combining any structural elements of the above embodiments, examples, and modifications, modifications that can be conceived by those skilled in the art by making various modifications to the above embodiments without departing from the spirit of the present invention, and various devices incorporating the multiplexer and communication device of the present invention are also included in the present invention.

[0259] For example, in the multiplexers, front-end circuits, and communication devices described in the above embodiments, examples, and variations, matching elements such as inductors and capacitors, as well as switching circuits, can be connected between circuit elements. Furthermore, the inductor may also include a wiring inductor formed by wiring connected between circuit elements.

[0260] Furthermore, an LC filter is defined as a filter whose passband is formed by one or more inductors and one or more capacitors. Therefore, an LC filter can also include an elastic wave resonator for forming an attenuation electrode that exists outside the passband.

[0261] This invention, as a multiplexer and communication device applicable to multi-band systems, can be widely used in communication devices such as mobile phones.

[0262] Explanation of reference numerals in the attached figures

[0263] 1. Multiplexers: 1, 1A; 2, 3, 4, 4A; 5, 5A; 6, 7, 8, 9; 10, 20, 20A; 20B; 500, 500A; 600A; 700... Multiplexers; 11, 12, 13, 21, 22, 23, 31, 32, 33, 41, 42, 43, 51, 52, 53, 61... Filters; 14, 14A; 15, 15A; 34, 35, 44, 45, 54, 55, 114, 115... 134, 135, 144, 145, 514, 514A, 602, 714... Low-pass filters; 24, 25, 46, 47, 56, 57, 124, 125, 136, 137, 146, 147, 601... High-pass filters; 60s, 61s, 62s, 63s, 64s, 65s, 66s, 67s, 68s... Series arm resonators; 60p, 61p, 62p, 63p, 64p... 65p, 66p, 67p, 68p... parallel arm resonators; 71a, 71b, 72a, 73a, 74a, 81a, 81b, 81c, 82a, 82b, 82c, 83a, 83b, 83c, 83d, 83e, 84a, 84b, 84c, 84d, 84e; 520A... inductors; 75a, 76a, 77a, 77b, 77c, 78a, 85a, 85b, 85c, 87a, 8... 7b, 87c, 88a, 88b, 88c, 88d, 88e, 89a, 89b, 89c, 89d, 89e, 89f, 89g, 89h, 89j... Capacitors; 90... Communication devices; 91... RF signal processing circuit (RFIC); 92... Antenna; 100... Common terminal; 110, 120, 130, 140... Input / output terminals; 520, 720... Impedance matching circuits.

Claims

1. A multiplexer comprising: a common terminal, a first input / output terminal, a second input / output terminal, and a third input / output terminal; a first filter having a first frequency band as a passband; a second filter being a bandpass filter or a band elimination filter having a second frequency band as a passband and a third frequency band as an attenuation band; a third filter having the third frequency band as a passband and the first frequency band and the second frequency band as attenuation bands; a fourth filter having the second frequency band and the third frequency band as passbands and the first frequency band as an attenuation band; and a fifth filter having the second frequency band and the third frequency band as passbands and the first frequency band as an attenuation band, the second frequency band and the third frequency band being at least partially different in frequency, the first frequency band not overlapping in frequency with the second frequency band and the third frequency band, one end of the first filter being connected to the common terminal, the other end of the first filter being connected to the first input / output terminal, one end of the fourth filter being connected to the common terminal, the other end of the fourth filter being connected to one end of the second filter, the other end of the second filter being connected to one end of the fifth filter, the other end of the fifth filter being connected to the second input / output terminal, one end of the third filter being connected to a connection node of the other end of the fourth filter and the one end of the second filter, the other end of the third filter being connected to the third input / output terminal.

2. The multiplexer according to claim 1, wherein the second frequency band and the third frequency band do not overlap in frequency, the first frequency band is located on a higher frequency side than the second frequency band and the third frequency band, the first filter has the second frequency band and the third frequency band as attenuation bands, the second filter has the first frequency band and the third frequency band as attenuation bands, the fourth filter is a lowpass filter having the second frequency band and the third frequency band as passbands and the first frequency band as an attenuation band, and the fifth filter is a lowpass filter having the second frequency band and the third frequency band as passbands and the first frequency band as an attenuation band.

3. The multiplexer according to claim 1, wherein the second frequency band and the third frequency band do not overlap in frequency, the first frequency band is located on a lower frequency side than the second frequency band and the third frequency band, the first filter has the second frequency band and the third frequency band as attenuation bands, the second filter has the first frequency band and the third frequency band as attenuation bands, the fourth filter is a highpass filter having the second frequency band and the third frequency band as passbands and the first frequency band as an attenuation band, and the fifth filter is a highpass filter having the second frequency band and the third frequency band as passbands and the first frequency band as an attenuation band.

4. The multiplexer according to claim 1, wherein the second frequency band includes the third frequency band, the first frequency band is located on a higher frequency side than the second frequency band and the third frequency band, and the fourth filter is a lowpass filter having the second frequency band and the third frequency band as passbands and the first frequency band as an attenuation band. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The first filter described above has the second and third frequency bands as attenuation bands, The second filter described above is a band elimination filter having the third frequency band as an attenuation band, The fourth filter described above is a high-pass filter having the second and third frequency bands as pass bands and the first frequency band as an attenuation band, The fifth filter described above is a high-pass filter having the second and third frequency bands as pass bands and the first frequency band as an attenuation band.

5. The multiplexer according to claim 1, wherein The second frequency band includes the third frequency band, The first frequency band is located on a lower frequency side than the second and third frequency bands, The first filter described above has the second and third frequency bands as attenuation bands, The second filter described above is a band elimination filter having the third frequency band as an attenuation band, The fourth filter described above is a high-pass filter having the second and third frequency bands as pass bands and the first frequency band as an attenuation band, The fifth filter described above is a high-pass filter having the second and third frequency bands as pass bands and the first frequency band as an attenuation band.

6. The multiplexer according to claim 1, wherein The second frequency band includes the third frequency band, The first frequency band is located on a higher frequency side than the second and third frequency bands, The first filter described above has the second and third frequency bands as attenuation bands, The second filter described above is a band elimination filter having the third frequency band as an attenuation band, The fourth filter described above is composed of a sixth filter and a seventh filter connected in series between the common terminal and the second filter, The fifth filter described above is composed of an eighth filter and a ninth filter connected in series between the second filter and the second input / output terminal, The sixth filter described above is a low-pass filter having the second and third frequency bands as pass bands and the first frequency band as an attenuation band, The seventh filter described above is a high-pass filter having the second and third frequency bands as pass bands, The eighth filter described above is a low-pass filter having the second and third frequency bands as pass bands and the first frequency band as an attenuation band, The ninth filter described above is a high-pass filter having the second and third frequency bands as pass bands.

7. The multiplexer according to claim 1, wherein The second frequency band includes the third frequency band, The first frequency band is located on a lower frequency side than the second and third frequency bands, The first filter described above has the second and third frequency bands as attenuation bands, The second filter described above is a band elimination filter having the third frequency band as an attenuation band, The fourth filter described above is composed of a sixth filter and a seventh filter connected in series between the common terminal and the second filter, The fifth filter described above is composed of an eighth filter and a ninth filter connected in series between the second filter and the second input / output terminal, The sixth filter described above is a low-pass filter having the second and third frequency bands as pass bands, The seventh filter is a high-pass filter having the second frequency band and the third frequency band as pass bands and the first frequency band as an attenuation frequency band. The eighth filter is a low-pass filter having the second frequency band and the third frequency band as pass bands. The ninth filter is a high-pass filter having the second frequency band and the third frequency band as pass bands and the first frequency band as an attenuation frequency band.

8. The multiplexer of claim 6, wherein, Further comprising: a fourth input / output terminal; and a tenth filter having a fourth frequency band as a pass band, the fourth frequency band does not overlap the second frequency band and the third frequency band in frequency, and the fourth frequency band is located on a lower frequency side than the second frequency band and the third frequency band, one end of the tenth filter is connected to the common terminal, and the other end of the tenth filter is connected to the fourth input / output terminal, the sixth filter is a low-pass filter having the second frequency band, the third frequency band, and the fourth frequency band as pass bands and the first frequency band as an attenuation frequency band, the seventh filter is a high-pass filter having the first frequency band, the second frequency band, and the third frequency band as pass bands and the fourth frequency band as an attenuation frequency band, the eighth filter is a low-pass filter having the second frequency band, the third frequency band, and the fourth frequency band as pass bands and the first frequency band as an attenuation frequency band, the ninth filter is a high-pass filter having the first frequency band, the second frequency band, and the third frequency band as pass bands and the fourth frequency band as an attenuation frequency band.

9. The multiplexer according to any one of claims 1 to 8, wherein the second frequency band is a mid-high frequency band, i.e., 1710-2370 MHz and 2496-2690 MHz, the third frequency band is WLAN, i.e., 2400-2483 MHz.

10. The multiplexer according to any one of claims 1, 2, 4, 6, and 8, wherein the first frequency band is an ultra-high frequency band, i.e., 3300-5000 MHz.

11. The multiplexer according to claim 8, wherein the fourth frequency band is L5 of GNSS, wherein GNSS is an abbreviation of Global Navigation Satellite System, and L5 is 1164.4-1187.95 MHz.

12. The multiplexer according to any one of claims 1, 3, 5, and 7, wherein the first frequency band is L5 of GNSS, wherein L5 is 1164.4-1187.95 MHz.

13. A communication apparatus comprising: an antenna; an RF signal processing circuit that processes a high-frequency signal transmitted and received by the antenna; and the multiplexer according to any one of claims 1 to 12, which transmits the high-frequency signal between the antenna and the RF signal processing circuit.

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