Patent Publication Number: US-11664830-B2

Title: Radio frequency module and communication device

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This is a continuation of U.S. application Ser. No. 17/071,112 filed on Oct. 15, 2020, which is a continuation of International Application No. PCT/JP2019/014578 filed on Apr. 2, 2019 which claims priority from Japanese Patent Application No. 2018-135476 filed on Jul. 19, 2018. The contents of these applications are incorporated herein by reference in their entireties. 
    
    
     BACKGROUND 
     The present disclosure relates to radio frequency modules and communication devices. 
     In recent communication services, carrier aggregation (hereinbelow, referred to as CA) is performed using a plurality of communication bands simultaneously with a goal of increasing the communication throughput. 
     A radio frequency module capable of performing CA using two communication bands (for example, Japanese Unexamined Patent Application Publication No. 2016-42696) includes, for example, a filter whose pass band is a first frequency band (for example, Band 39), a filter whose pass band is a second frequency band (for example, Band 41), a switch circuit that switches between a transmit path and a receive path, and a transmit amplifier. According to this configuration, with switching operations of the foregoing switch circuit, it becomes possible to perform CA using at least one of a transmit signal and a receive signal of the first frequency band and at least one of a transmit signal and a receive signal of the second frequency band. 
     BRIEF SUMMARY 
     In the radio frequency module described in Japanese Unexamined Patent Application Publication No. 2016-42696, the filters are respectively installed for the communication bands to be used irrespective of an inclusion relationship and an overlapping relationship of frequencies among different communication bands. However, for example, in a system that uses two or more communication bands, in the case where a receive band of a first communication band is included in a transmit band of a second communication band, it is conceivable to use a transmit filter of the second communication band also as a receive filter of the first communication band for downsizing. This eliminates the necessity to install a dedicated filter for the receive band of the first communication band and enables to achieve the downsizing of the radio frequency module. 
     However, in this case, a receive filter of a third communication band is a filter that allows a receive signal to pass. Therefore, when the third communication band is used, it is suitable to connect the transmit filter of the second communication band and a receive amplifier. Here, when CA is performed using a transmit signal of the first communication band and a receive signal of the third communication band, it is suitable to, using the switch circuit, connect the transmit amplifier and a transmit filter of the first communication band and connect the receive amplifier and the transmit filter of the second communication band. At this time, there is a possibility that a transmit signal from the transmit amplifier may be leaked into the foregoing receive amplifier via the switch circuit. Because of this, there is a problem of decreasing reception sensitivity even when downsizing of the radio frequency module is achieved. 
     The present disclosure provides a radio frequency module and a communication device, each of which is capable of performing CA using a plurality of communication bands including two communication bands in which a transmit band of one of the two communication bands and a receive band of the other communication band are in an inclusion relationship and in which the decrease in reception sensitivity is suppressed while downsizing. 
     A radio frequency module according to one aspect of the present disclosure is a radio frequency module that transmits radio frequency signals of a first communication band, a second communication band, and a third communication band, which are frequency bands different from one another, a transmit band of the second communication band including a receive band of the third communication band, a transmit signal of the first communication band and a receive signal of the third communication band being able to be simultaneously transmitted and received, the radio frequency module including: a first transmit filter whose pass band is a transmit band of the first communication band; a second transmit filter whose pass band is the transmit band of the second communication band; a transmit amplifier that amplifies radio frequency signals of the transmit band of the first communication band and the transmit band of the second communication band; and a first switch circuit, wherein the first switch circuit includes a first common terminal, a first selection terminal, a second selection terminal, and a third selection terminal, a first switch that switches between being electrically continuous and electrically discontinuous between the first common terminal and the first selection terminal, a second switch that switches between being electrically continuous and electrically discontinuous between the first common terminal and the second selection terminal, and a third switch that switches between being electrically continuous and electrically discontinuous between the second selection terminal and the third selection terminal, the first common terminal is connected to an output terminal of the transmit amplifier, the first selection terminal is connected to an input terminal of the first transmit filter, the second selection terminal is connected to an input terminal of the second transmit filter, and the third selection terminal is connected to a receive path that transmits the receive signal of the third communication band. 
     Other features, elements, characteristics and advantages of the present disclosure will become more apparent from the following detailed description of embodiments of the present disclosure with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG.  1    is a circuit configuration diagram of a communication device according to an embodiment 1; 
         FIG.  2    is a diagram illustrating one example of frequency allocation of communication bands that can be used in the radio frequency module according to the embodiment 1; 
         FIG.  3    is a circuit configuration diagram of a radio frequency module according to a comparative example; 
         FIG.  4 A  is a diagram illustrating a circuit state of the radio frequency module according to the embodiment 1 when CA of Band A and Band B is performed; 
         FIG.  4 B  is a diagram illustrating a circuit state of the radio frequency module according to the embodiment 1 when CA of Band A and Band C is performed; 
         FIG.  5    is a circuit configuration diagram of a radio frequency module according to a modified example 1 of the embodiment; 
         FIG.  6    is a graph that compares bandpass characteristics of the radio frequency modules according to the modified example 1 and the embodiment; 
         FIG.  7    is a circuit configuration diagram of a radio frequency module according to a modified example 2 of the embodiment; and 
         FIG.  7 A  is a circuit configuration diagram of a radio frequency module according to a modified example 3 of the embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the drawings. Note that the embodiment and modified examples, which will be described below, each illustrates a comprehensive or specific example. Numeric values, shapes, materials, constituting elements, arrangements and connection modes of the constituting elements, and the like illustrated in the following embodiment and modified examples are mere examples, and not intended to limit the present disclosure. Of constituting elements in the following embodiment and modified examples, the constituting elements that are not described in an independent claim will be described as optional constituting elements. Furthermore, dimensions or ratios of dimensions of constituting elements illustrated in the drawings are not necessarily be precise. 
     Embodiment 
     1. Circuit Configurations of Radio Frequency Module and Communication Device 
       FIG.  1    is a circuit configuration diagram of a communication device  5  according to an embodiment. As illustrated in  FIG.  1   , the communication device  5  includes an antenna element  2 , a radio frequency module  1 , a receive amplifier circuit  50 , and a RF signal processing circuit (RFIC)  3 . 
     The RFIC  3  is an RF signal processing circuit that performs processing on radio frequency signals to be transmitted from and received by the antenna element  2 . Specifically, the RFIC  3  performs signal processing on a radio frequency signal input via a receive path of the radio frequency module  1  using down-converting and the like, and outputs a receive signal generated by this signal processing to a baseband signal processing circuit (not illustrated). Furthermore, the RFIC  3  performs signal processing on a transmit signal input from the baseband signal processing circuit using up-converting and the like, and outputs a radio frequency signal generated by this signal processing to a transmit path of the radio frequency module  1 . 
     Furthermore, the RFIC  3  also functions as a control unit that controls connections of switch circuits  20  and  30  included in the radio frequency module  1  based on a communication band (frequency band) to be used. Specifically, the RFIC  3  switches the connections of the switch circuits  20  and  30  included in the radio frequency module  1  using control signals (not illustrated). The control unit may alternatively be provided outside the RFIC  3 , or may be provided, for example, inside the radio frequency module  1  or the baseband signal processing circuit. 
     The receive amplifier circuit  50  is made up of receive amplifiers  51  and  52 . Of receive signals output from the radio frequency module  1 , the receive amplifier  51  preferentially amplifies a receive signal of Band A (first communication band) and outputs the amplified receive signal to the RFIC  3 . Of the receive signals output from the radio frequency module  1 , the receive amplifier  52  preferentially amplifies receive signals of Band B (second communication band) and Band C (third communication band) and outputs these amplified receive signals to the RFIC  3 . 
     The antenna element  2  is connected to a common terminal  20   a  of the switch circuit  20 , emits a radio frequency signal output from the radio frequency module  1 , and receives a radio frequency signal from outside and outputs to the radio frequency module  1 . 
     Note that in the communication device  5  according to the present embodiment, the antenna element  2  is an optional constituting element. 
     Next, the configuration of the radio frequency module  1  is described in detail. 
     As illustrated in  FIG.  1   , the radio frequency module  1  includes transmit filters  11  and  13 , receive filters  12  and  14 , a transmit amplifier  40 , and the switch circuits  20  and  30 . 
     The radio frequency module  1  according to the present embodiment is a radio frequency module capable of transmitting a transmit signal and a receive signal of Band A (first communication band), a transmit signal and a receive signal of Band B (second communication band), and a receive signal of Band C (third communication band). Furthermore, the radio frequency module  1  is capable of performing (1) CA that simultaneously transmits a transmit signal of Band A and a transmit signal of Band B (two uplink), (2) CA that simultaneously transmits and receives a transmit signal of Band A and a receive signal of Band C (one uplink one downlink), (3) CA that simultaneously receives a receive signal of Band A and a receive signal of Band B (two downlink), (4) CA that simultaneously receives a receive signal of Band A and a receive signal of Band C (two downlink), (5) CA that simultaneously transmits and receives a transmit signal and a receive signal of Band A and a transmit signal and a receive signal of Band B (two uplink two downlink), and (6) CA that simultaneously transmits and receives a transmit signal and a receive signal of Band A and a receive signal of Band C (one uplink two downlink). 
       FIG.  2    is a diagram illustrating one example of frequency allocation of communication bands that can be used in the radio frequency module  1  according to the embodiment. Band A (first communication band) in the present embodiment is, for example, Band 26 (transmit band: 814-849 MHz, receive band: 859-894 MHz) of Long Term Evolution (LTE). Band B (second communication band) is, for example, Band 28 (transmit band: 703-748 MHz, receive band: 758-803 MHz) of LTE. Band C (third communication band) is, for example, Band 29 (receive band: 717-727 MHz) of LTE. 
     As illustrated in  FIG.  2   , Band A (Band 26) and Band B (Band 28) each has a transmit band (Tx) and a receive band (Rx). Furthermore, Band C (Band 29) has only a receive band (Rx). Here, the transmit band of Band B (Band 28) includes the receive band of Band C (Band 29). 
     The radio frequency module  1  according to the present embodiment includes the filters that allow Bands A to C, which have the frequency relationship described above, to pass and the switches that switch signal paths of the respective communication bands. 
     The transmit filter  11  is a first transmit filter whose pass band is the transmit band of Band A (A-Tx). The receive filter  12  is a first receive filter whose pass band is the receive band of Band A (A-Rx). 
     The transmit filter  13  is a second transmit filter whose pass band is the transmit band of Band B (B-Tx). The receive filter  14  is a second receive filter whose pass band is the receive band of Band B (B-Rx). Note that the pass band of the transmit filter  13  includes the receive band of Band C (C-Rx). 
     The switch circuit  20  is a multi-connection type second switch circuit that includes the common terminal  20   a  (second common terminal), a selection terminal  20   b  (fifth selection terminal), and a selection terminal  20   c  (sixth selection terminal) and is capable of simultaneously forming a connection between the common terminal  20   a  and the selection terminal  20   b  and a connection between the common terminal  20   a  and the selection terminal  20   c.    
     The selection terminal  20   b  is connected to an output terminal of the transmit filter  11  and an input terminal of the receive filter  12 , and the selection terminal  20   c  is connected to an output terminal of the transmit filter  13  and an input terminal of the receive filter  14 . 
     In the switch circuit  20 , when at least one of the transmission of a transmit signal of Band A and the reception of a receive signal of Band A is performed, the common terminal  20   a  and the selection terminal  20   b  are in an electrically continuous state. Furthermore, when at least one of the transmission of a transmit signal of Band B, the reception of a receive signal of Band B, and the reception of a receive signal of Band C is performed, the common terminal  20   a  and the selection terminal  20   c  are in the electrically continuous state. This enables to disconnect the output terminal of the transmit filter  11  from the output terminal of the transmit filter  13  at the time of non-CA, thereby improving bandpass characteristics of a signal path selected at the time of non-CA. 
     The switch circuit  30  is a first switch circuit that includes a common terminal  30   a  (first common terminal), a selection terminal  30   b  (first selection terminal), a selection terminal  30   c  (second selection terminal), a selection terminal  30   d  (third selection terminal), and switches  31 ,  32 , and  33 . 
     The switch  31  is connected to the common terminal  30   a  at one terminal and to the selection terminal  30   b  at the other terminal and is a first switch that switches between being electrically continuous and electrically discontinuous between the common terminal  30   a  and the selection terminal  30   b . The switch  31  is, for example, a single pole single throw (SPST) type switch element. 
     The switch  32  is connected to the common terminal  30   a  at one terminal and to the selection terminal  30   c  at the other terminal and is a second switch that switches between being electrically continuous and electrically discontinuous between the common terminal  30   a  and the selection terminal  30   c . The switch  32  is, for example, a SPST type switch element. 
     The switch  33  is connected to the selection terminal  30   c  at one terminal and to the selection terminal  30   d  at the other terminal and is a third switch that switches between being electrically continuous and electrically discontinuous between the selection terminal  30   c  and the selection terminal  30   d . The switch  33  is, for example, a SPST type switch element. 
     According to the foregoing configuration of the switch circuit  30 , the switch circuit  30  is a multi-connection type switch circuit capable of simultaneously connecting two or more of four terminals, which are the common terminal  30   a  and the selection terminals  30   b ,  30   c , and  30   d.    
     Of transmit signals output from the RFIC  3 , the transmit amplifier  40  preferentially amplifies transmit signals of Bands A and B and outputs these amplified transmit signals to the common terminal  30   a  of the switch circuit  30 . 
     The common terminal  30   a  is connected to an output terminal of the transmit amplifier  40 . The selection terminal  30   b  is connected to an input terminal of the transmit filter  11  and an output terminal of the receive filter  12 . The selection terminal  30   c  is connected to an input terminal of the transmit filter  13  and an output terminal of the receive filter  14 . The selection terminal  30   d  is connected to a receive path  61  that transmits a receive signal of Band C and is connected to the receive amplifier  52  via the receive path  61 . 
     The selection terminal  20   b  is connected to the output terminal of the transmit filter  11  and the input terminal of the receive filter  12 . The selection terminal  20   c  is connected to the output terminal of the transmit filter  13  and the input terminal of the receive filter  14 . An input terminal of the receive amplifier  51  is connected to the output terminal of the receive filter  12 . An input terminal of the receive amplifier  52  is connected to the output terminal of the receive filter  14 . 
     Note that in the radio frequency module  1  according to the present embodiment, the receive filters  12  and  14  and the switch circuit  20  are optional constituting elements. Furthermore, in the communication device  5  according to the present embodiment, the antenna element  2  is an optional constituting element. 
       FIG.  3    is a circuit configuration diagram of a radio frequency module  500  according to a comparative example. As illustrated in  FIG.  3   , the radio frequency module  500  is a radio frequency module that is typically assumed and includes transmit filters  11  and  13 , receive filters  12 ,  14 , and  15 , transmit amplifiers  41  and  42 , and the switch circuits  520  and  530 . The radio frequency module  500  according to the present comparative example is different from the radio frequency module  1  according to the embodiment in that the receive filter  15  is added, two transmit amplifiers are installed, and the switch circuits  520  and  530  have different configurations. Hereinafter, the radio frequency module  500  according to the present comparative example is described with the emphasis on points different from the radio frequency module  1  according to the embodiment while omitting the description regarding the same point. 
     The receive filter  15  is a filter whose pass band is the receive band of Band C (C-Rx). 
     The switch circuit  520  is a multi-connection type switch circuit that includes a common terminal  520   a  and selection terminals  520   b ,  520   c , and  520   d  and is capable of simultaneously forming at least two of a connection between the common terminal  520   a  and the selection terminal  520   b , a connection between the common terminal  520   a  and the selection terminal  520   c , and a connection between the common terminal  520   a  and the selection terminal  520   d.    
     The selection terminal  520   b  is connected to an output terminal of the transmit filter  11  and an input terminal of the receive filter  12 , the selection terminal  520   c  is connected to an output terminal of the transmit filter  13  and an input terminal of the receive filter  14 , and the selection terminal  520   d  is connected to an input terminal of the receive filter  15 . 
     The switch circuit  530  is a switch circuit that includes terminals  530   a ,  530   b ,  530   c , and  530   d  and switches  531  and  532 . The switch  531  is connected to the terminal  530   a  at one terminal and to the terminal  530   c  at the other terminal and switches between being electrically continuous and electrically discontinuous between the terminal  530   a  and the terminal  530   c . The switch  532  is connected to the terminal  530   b  at one terminal and to the terminal  530   d  at the other terminal and switches between being electrically continuous and electrically discontinuous between the terminal  530   b  and the terminal  530   d.    
     According to the foregoing configuration of the switch circuit  530 , the switch circuit  530  is a multi-connection type switch circuit capable of simultaneously forming a connection between the terminal  530   a  and the terminals  530   c  and a connection between the terminal  530   b  and the terminal  530   d.    
     Of radio frequency signals output from the RFIC  3 , the transmit amplifier  41  preferentially amplifies a radio frequency signal of Band A and outputs this amplified transmit signal to the terminal  530   a . Of radio frequency signals output from the RFIC  3 , the transmit amplifier  42  preferentially amplifies a radio frequency signal of Band B and outputs this amplified transmit signal to the terminal  530   b.    
     The terminal  530   a  is connected to an output terminal of the transmit amplifier  41 . The terminal  530   b  is connected to an output terminal of the transmit amplifier  42 . The terminal  530   c  is connected to an input terminal of the transmit filter  11 . The terminal  530   d  is connected to an input terminal of the transmit filter  13 . 
     According to the foregoing configuration of the radio frequency module  500  according to the comparative example, it becomes possible to transmit a transmit signal and a receive signal of Band A, a transmit signal and a receive signal of Band B, and a receive signal of Band C. Furthermore, the radio frequency module  500  can perform (1) CA that simultaneously transmits a transmit signal of Band A and a transmit signal of Band B (two uplink) and (5) CA that simultaneously transmits and receives a transmit signal and a receive signal of Band A and a transmit signal and a receive signal of Band B (two uplink two downlink) by setting the switches  531  and  532  to the electrically continuous state, connecting the common terminal  520   a  and the selection terminal  520   b , and connecting the common terminal  520   a  and the selection terminal  520   c . Furthermore, by setting the switch  531  to the electrically continuous state, connecting the common terminal  520   a  and the selection terminal  520   b , and connecting the common terminal  520   a  and the selection terminal  520   d , (2) CA that simultaneously transmits and receives a transmit signal of Band A and a receive signal of Band C (one uplink one downlink) and (6) CA that simultaneously transmits and receives a transmit signal and a receive signal of Band A and a receive signal of Band C (one uplink two downlink) can be performed. Furthermore, by connecting the common terminal  520   a  and the selection terminal  520   b  and connecting the common terminal  520   a  and the selection terminal  520   c , (3) CA that simultaneously receives a receive signal of Band A and a receive signal of Band B (two downlink) can be performed. Furthermore, by connecting the common terminal  520   a  and the selection terminal  520   b  and connecting the common terminal  520   a  and the selection terminal  520   d , (4) CA that simultaneously receives a receive signal of Band A and a receive signal of Band C (two downlink) can be performed. 
     However, in the radio frequency module  500  according to the comparative example, two transmit amplifiers are respectively installed for Bands A and B, and furthermore, the receive filter  15  only for use in the receive band of Band C is installed. This increases the size of the radio frequency module  500 . 
     Whereas, since the receive band of Band C (C-Rx) is included in the transmit band of Band B (B-Tx), as a downsizing measure, it is conceivable to use the transmit filter of Band B also as the receive filter of Band C. Furthermore, in the case where a transmit amplifier capable of amplifying radio frequency signals of Band A and Band B is used, the number of the transmit amplifiers can be reduced compared with the radio frequency module  500  according to the comparative example, thereby achieving further downsizing. 
     The receive filter of Band C is a filter that allows a receive signal to pass. Therefore, in the case where the transmit filter of Band B is used also as the receive filter of Band C, it is suitable to connect the transmit filter of Band B and a receive amplifier circuit using a switch circuit at the time of using the transmit filter of Band B as the receive filter of Band C. 
     Furthermore, in the case where a transmit amplifier capable of amplifying radio frequency signals of Band A and Band B is installed, it is suitable to connect both the transmit filter of Band A and the transmit filter of Band B to the transmit amplifier. 
     Here, when a transmit signal of Band A and a receive signal of Band C are simultaneously transmitted and received, it is suitable to connect the transmit amplifier and the transmit filter of Band A and connect the transmit filter of Band B and a receive path that transmits a receive signal of Band C using the foregoing switch circuit. However, when the state where both the transmit filter of Band A and the transmit filter of Band B are connected to the transmit amplifier and the state where the transmit filter of Band B and a receive path of Band C are connected coexist, a transmit signal from the transmit amplifier is leaked into the foregoing receive path via the switch circuit. This leads to a problem of decreasing reception sensitivity in the receive path. 
     Whereas, according to the foregoing configuration of the radio frequency module  1  according to the present embodiment, the switch  32  is installed between the common terminal  30   a  and the selection terminal  30   c  and the switch  33  is installed between the selection terminal  30   c  and the selection terminal  30   d . Therefore, when a transmit signal of Band A and a receive signal of Band C are simultaneously transmitted and received, the isolation between a transmit signal of Band A and a receive signal of Band C can be improved while using the transmit filter  13  as the filter that allows a transmit signal of Band C to pass by setting the switch  32  to an electrically discontinuous state and setting the switch  33  to the electrically continuous state. Furthermore, when a transmit signal of Band A and a transmit signal of Band B are non-simultaneously transmitted, even in the case where the single transmit amplifier  40  is used as both a transmit amplifier amplifying a radio frequency signal of Band A and a transmit amplifier amplifying a radio frequency signal of Band B by using switching operations of the switches  31  and  32 , the isolation between a transmit signal of Band A and a transmit signal of Band B can be ensured. Accordingly, it becomes possible to suppress the decrease in reception sensitivity in Band C while downsizing the radio frequency module  1  and the communication device  5 , each of which simultaneously transmits and receives a transmit signal of Band A and a receive signal of Band C and in which the receive band of Band C is included in the transmit band of Band B. That is to say, it becomes possible to provide a radio frequency module and a communication device, each of which is capable of performing CA using a plurality of communication bands including two communication bands in which a transmit band of one of the two communication bands and a receive band of the other communication band are in an inclusion relationship and in which the decrease in reception sensitivity is suppressed while downsizing. 
     The switch circuit  30  may alternatively be formed within a single switch IC. In the case where the switch circuit  30  is formed inside a single switch IC, downsizing can be achieved. However, in this case, gaps between the common terminal  30   a  and selection terminals  30   b  to  30   d  become narrower, and the isolation among radio frequency signals of the communication bands degrade. Whereas, according to the foregoing configuration of the switch circuit  30 , the isolation between a transmit signal of Band A and a receive signal of Band C can be improved by setting the switch  32  to the electrically discontinuous state. Accordingly, it becomes possible to improve the reception sensitivity in Band C while downsizing the radio frequency module  1 . 
     Furthermore, the switch circuits  20  and  30  and the foregoing control unit may constitute a single switch IC. This enables to shorten control wiring lines connecting the control unit and the switch circuits  20  and  30 , and thus the degradation of control accuracy caused by interference between a control signal and a radio frequency signal can be suppressed. Furthermore, the radio frequency module  1  can be fabricated inexpensively by forming the switch IC using Si-based complementary metal oxide semiconductor (CMOS). 
     2. Circuit Operation of Radio Frequency Module 
       FIG.  4 A  is a diagram illustrating a circuit state of the radio frequency module  1  according to the embodiment 1 when CA of Band A and Band B is performed.  FIG.  4 A  illustrates the circuit state when CA is performed using a transmit signal and a receive signal of Band A and a transmit signal and a receive signal of Band B. 
     When a transmit signal and a receive signal of Band A and a transmit signal and a receive signal of Band B are simultaneously transmitted and received, the switches  31  and  32  are in the electrically continuous state, and the switch  33  is in the electrically discontinuous state. Furthermore, the common terminal  20   a  and the selection terminal  20   b  are connected, and the common terminal  20   a  and the selection terminal  20   c  are connected. 
     This allows a transmit signal of Band A to be transmitted to the antenna element  2  via the transmit amplifier  40 , the common terminal  30   a , the switch  31 , the selection terminal  30   b , the transmit filter  11 , the selection terminal  20   b , and the common terminal  20   a . Furthermore, a transmit signal of Band B is transmitted to the antenna element  2  via the transmit amplifier  40 , the common terminal  30   a , the switch  32 , the selection terminal  30   c , the transmit filter  13 , the selection terminal  20   c , and the common terminal  20   a.    
     Here, since the switch  33  is in the electrically discontinuous state, it becomes possible to suppress the leakage of a transmit signal of Band A and a transmit signal of Band B into the receive path of Band C. Thus, a transmit signal of Band A and a transmit signal of Band B can be transmitted to the antenna element  2  with less loss. 
     Furthermore, a receive signal of Band A is transmitted to the RFIC  3  via the antenna element  2 , the common terminal  20   a , the selection terminal  20   b , the receive filter  12 , and the receive amplifier  51 . Furthermore, a receive signal of Band B is transmitted to the RFIC  3  via the antenna element  2 , the common terminal  20   a , the selection terminal  20   c , the receive filter  14 , and the receive amplifier  52 . 
       FIG.  4 B  is a diagram illustrating a circuit state of the radio frequency module  1  according to the embodiment 1 when CA of Band A and Band C is performed.  FIG.  4 B  illustrates the circuit state when CA is performed using a transmit signal and a receive signal of Band A and a receive signal of Band C. 
     When a transmit signal and a receive signal of Band A and a receive signal of Band C are simultaneously transmitted and received, the switches  31  and  33  are in the electrically continuous state, and the switch  32  is in the electrically discontinuous state. Furthermore, the common terminal  20   a  and the selection terminal  20   b  are connected, and the common terminal  20   a  and the selection terminal  20   c  are connected. 
     This allows a transmit signal of Band A to be transmitted to the antenna element  2  via the transmit amplifier  40 , the common terminal  30   a , the switch  31 , the selection terminal  30   b , the transmit filter  11 , the selection terminal  20   b , and the common terminal  20   a.    
     Here, since the switch  32  is in the electrically discontinuous state, it becomes possible to suppress the leakage of a transmit signal output from the transmit amplifier  40  into a transmit path of Band B and the receive path of Band C. Therefore, it becomes possible to suppress the coupling of a radio frequency component of Band B (and Band C), which is transmitted in the transmit path of Band B, with a transmit signal of Band A, which is transmitted through the transmit path of Band A and output to the antenna element  2 , within the switch circuit  20 . Furthermore, it becomes possible to suppress the inflow of a transmit signal output from the transmit amplifier  40  into the receive path of Band C. 
     Furthermore, a receive signal of Band A is transmitted to the RFIC  3  via the antenna element  2 , the common terminal  20   a , the selection terminal  20   b , the receive filter  12 , and the receive amplifier  51 . Furthermore, a receive signal of Band C is transmitted to the RFIC  3  via the antenna element  2 , the common terminal  20   a , the selection terminal  20   c , the transmit filter  13 , the selection terminal  30   c , the switch  33 , the selection terminal  30   d , and the receive amplifier  52 . 
     As illustrated in  FIG.  4 A  and  FIG.  4 B , with the foregoing connection states of the switch circuits  20  and  30 , it become possible to switch between CA that uses a transmit signal and a receive signal of Band A and a transmit signal and a receive signal of Band B (two uplink two downlink) and CA that uses a transmit signal and a receive signal of Band A and a receive signal of Band C (one uplink two downlink). 
     Although it is not illustrated, when a transmit signal of Band A and a transmit signal of Band B are simultaneously transmitted, the switches  31  and  32  are in the electrically continuous state, and the switch  33  is in the electrically discontinuous state. Furthermore, when a transmit signal of Band A and a receive signal of Band C are simultaneously transmitted and received, the switches  31  and  33  are in the electrically continuous state, and the switch  32  is in the electrically discontinuous state. In either case, the common terminal  20   a  and the selection terminal  20   b  are connected, and the common terminal  20   a  and the selection terminal  20   c  are connected. 
     Because of this, it becomes possible to switch between CA that uses a transmit signal of Band A and a receive signal of Band C (one uplink one downlink) and CA that uses a transmit signal of Band A and a transmit signal of Band B (two uplink) using the switch circuits  20  and  30 . 
     Although it is not illustrated, when a receive signal of Band A and a receive signal of Band B are simultaneously received, the switch  33  is in the electrically discontinuous state. Furthermore, when a receive signal of Band A and a receive signal of Band C are simultaneously received, the switch  33  is in the electrically continuous state. In either case, the common terminal  20   a  and the selection terminal  20   b  are connected, and the common terminal  20   a  and the selection terminal  20   c  are connected. 
     Because of this, it becomes possible to switch between CA that uses a receive signal of Band A and a receive signal of Band B (two downlink) and CA that uses a receive signal of Band A and a receive signal of Band C (two downlink) using the switch circuits  20  and  30 . 
     3. Radio Frequency Module According to Modified Example 1 
       FIG.  5    is a circuit configuration diagram of a radio frequency module  1 A according to a modified example 1 of the embodiment. As illustrated in  FIG.  5   , the radio frequency module  1 A includes transmit filters  11  and  13 , receive filters  12  and  14 , a transmit amplifier  40 , and the switch circuits  20  and  60 . The radio frequency module  1 A according to the present modified example is different from the radio frequency module  1  according to the embodiment in the configuration of the switch circuit  60 . Hereinafter, the radio frequency module  1 A according to the present modified example is described with the emphasis on points different from the radio frequency module  1  according to the embodiment while omitting the description regarding the same points. 
     The switch circuit  60  is a first switch circuit that includes a common terminal  30   a  (first common terminal), a selection terminal  30   b  (first selection terminal), a selection terminal  30   c  (second selection terminal), a selection terminal  30   d  (third selection terminal), and switches  31 ,  32 ,  33 , and  34 . 
     The switch  31  is connected to the common terminal  30   a  at one terminal and to the selection terminal  30   b  at the other terminal and is a first switch that switches between being electrically continuous and electrically discontinuous between the common terminal  30   a  and the selection terminal  30   b . The switch  31  is, for example, a SPST type switch element. 
     The switch  32  is connected to the switch  34  at one terminal and to the selection terminal  30   c  at the other terminal and is part of a second switch that switches between being electrically continuous and electrically discontinuous between the common terminal  30   a  and the selection terminal  30   c . The switch  32  is, for example, a SPST type switch element. 
     The switch  34  is connected to the common terminal  30   a  at one terminal and to the switch  32  at the other terminal and is part of the second switch that switches between being electrically continuous and electrically discontinuous between the common terminal  30   a  and the selection terminal  30   c . The switch  34  is, for example, a SPST type switch element. 
     The switches  32  and  34  are two switch elements connected in series to each other and constitute the second switch that switches between being electrically continuous and electrically discontinuous between the common terminal  30   a  and the selection terminal  30   c . Note that in the radio frequency module  1 A according to the present modified example 1, the switches connected in series between the common terminal  30   a  and the selection terminal  30   c  are not limited to two switch elements, such as the switches  32  and  34  and may be any two or more switch elements connected in series. 
     The switch  33  is connected to the selection terminal  30   c  at one terminal and to the selection terminal  30   d  at the other terminal and is a third switch that switches between being electrically continuous and electrically discontinuous between the selection terminal  30   c  and the selection terminal  30   d . The switch  33  is, for example, a SPST type switch element. 
     According to the foregoing configuration of the switch circuit  60 , the switch circuit  60  is a multi-connection type switch circuit capable of simultaneously connecting two or more of four terminals, which are the common terminal  30   a  and the selection terminals  30   b ,  30   c , and  30   d.    
     Note that the switches  32  and  34  are in the electrically continuous state simultaneously or in the electrically discontinuous state simultaneously. That is to say, the switches  32  and  34  function as the single second switch. 
     According to the foregoing configuration, the second switch is installed between the common terminal  30   a  and the selection terminal  30   c . However, this second switch is made up of two switches  32  and  34  that are connected in series. This enables further suppression of the leakage of a radio frequency signal output from the transmit amplifier  40  into the transmit path of Band B and the receive path of Band C when the second switch is set to the electrically discontinuous state. Therefore, it becomes possible to further improve the isolation between a transmit signal of Band A and a receive signal of Band C. Accordingly, it becomes possible to further improve the reception sensitivity in Band C while downsizing the radio frequency module  1 A. 
       FIG.  6    is a graph that compares bandpass characteristics of the radio frequency modules according to the modified example 1 and the embodiment.  FIG.  6    illustrates bandpass characteristics from the common terminal  30   a  to the common terminal  20   a  inclusive of the transmit filter  11  in the radio frequency module  1  according to the embodiment and the radio frequency module  1 A according to the modified example 1. Note that the switch  31  is in the electrically continuous state, the switches  32  and  34  are in the electrically discontinuous state, and the common terminal  20   a  and the selection terminal  20   b  are connected. Furthermore, Band 26 of LTE is used as Band A, Band 28 of LTE is used as Band B, and Band 29 of LTE is used as Band C. 
     In the radio frequency modules according to the embodiment and the modified example 1, no difference can be seen in the insertion loss in the transmit band of Band A (B26-Tx). Whereas, with regard to the attenuation characteristic in Band C (B29-Rx), the radio frequency module  1 A according to the modified example 1 provides a better performance than the radio frequency module  1  according to the embodiment. The radio frequency module  1  according to the embodiment provides an attenuation of about 25 dB in Band C (B29-Rx), whereas the radio frequency module  1 A according to the modified example 1 provides an attenuation of about 38 dB in Band C (B29-Rx). 
     When a transmit signal of Band A and a receive signal of Band C are simultaneously transmitted and received, the switches  31  and  33  are in the electrically continuous state, and the switch  32  (second switch) is in the electrically discontinuous state. In this case, a transmit signal output from the transmit amplifier  40  is output to the antenna element  2  after passing the transmit path of Band A and the transmit filter  11  via the switch  31  in the electrically continuous state. At the same time, here, part of the transmit signal output from the transmit amplifier  40  flows into the transmit path of Band B and the receive path of Band C via the switch  32  (second switch) in the electrically discontinuous state, and an unwanted wave having a frequency component of Band B (and Band C) that has entered therein flows further into the transmit path of Band A via the switch circuit  20  and the like. That is to say, in the bandpass characteristics from the common terminal  30   a  to the common terminal  20   a  inclusive of the transmit filter  11 , the attenuation characteristic in Band B (and Band C) is affected by isolation performance of the switch  32  in the electrically discontinuous state. 
     The radio frequency module  1 A according to the modified example 1 improves the isolation performance of the second switch in the electrically discontinuous state by making up the second switch, which switches the connection between the common terminal  30   a  and the selection terminal  30   c , from two switches  32  and  34  connected in series. This enables to suppress the inflow of a transmit signal output from the transmit amplifier  40  into the transmit path of Band B and the receive path of Band C via the second switch in the electrically discontinuous state. 
     Accordingly, when a transmit signal of Band A and a receive signal of Band C are simultaneously transmitted and received, it becomes possible to further improve the isolation between the transmit signal of Band A and the receive signal of Band C. Accordingly, it becomes possible to further improve the reception sensitivity in Band C while downsizing the radio frequency module  1 A. 
     4. Radio Frequency Module According to Modified Example 2 
       FIG.  7    is a circuit configuration diagram of a radio frequency module  1 B according to a modified example 2 of the embodiment. As illustrated in  FIG.  7   , the radio frequency module  1 B includes transmit filters  11  and  13 , receive filters  12  and  14 , a transmit amplifier  40 , the switch circuits  20  and  70 , and an inductor  80 . The radio frequency module  1 B according to the present modified example is different from that radio frequency module  1 A according to the modified example 1 in that the switch circuit  70  has a different configuration and the inductor  80  is added. Hereinafter, the radio frequency module  1 B according to the present modified example is described with the emphasis on points different from the radio frequency module  1 A according to the modified example 1 while omitting the description regarding the same points. 
     The switch circuit  70  is a first switch circuit that includes a common terminal  70   a  (first common terminal), a selection terminal  70   b  (first selection terminal), a selection terminal  70   c  (second selection terminal), a selection terminal  70   d  (third selection terminal), a selection terminal  70   e  (fourth selection terminal), and switches  71 ,  72 ,  73 ,  74 , and  75 . 
     The switch  71  is connected to the common terminal  70   a  at one terminal and to the selection terminal  70   b  at the other terminal and is a first switch that switches between being electrically continuous and electrically discontinuous between the common terminal  70   a  and the selection terminal  70   b . The switch  71  is, for example, a SPST type switch element. 
     The switch  72  is connected to the switch  74  at one terminal and to the selection terminal  70   c  at the other terminal and is part of a second switch that switches between being electrically continuous and electrically discontinuous between the common terminal  70   a  and the selection terminal  70   c . The switch  72  is, for example, a SPST type switch element. 
     The switch  74  is connected to the common terminal  70   a  at one terminal and to the switch  72  at the other terminal and is part of the second switch that switches between being electrically continuous and electrically discontinuous between the common terminal  70   a  and the selection terminal  70   c . The switch  74  is, for example, a SPST type switch element. 
     The switch  73  is connected to the selection terminal  70   c  at one terminal and to the selection terminal  70   d  at the other terminal and is a third switch that switches between being electrically continuous and electrically discontinuous between the selection terminal  70   c  and the selection terminal  70   d . The switch  73  is, for example, a SPST type switch element. 
     The switch  75  is connected to a connection point of the switches  72  and  74  at one terminal and to the selection terminal  70   e  at the other terminal and is a fourth switch that switches between being electrically continuous and electrically discontinuous between this connection point and the selection terminal  70   e . The switch  75  is, for example, a SPST type switch element. 
     Note that the one terminal of the switch  75  is not necessarily connected to the foregoing connection point and may alternatively be connected to the common terminal  70   a  or the selection terminal  70   c.    
     The inductor  80  is connected to the selection terminal  70   e  at one terminal and to ground at the other terminal. Note that the other terminal of the inductor  80  may not necessarily be connected to the ground. 
     When a transmit signal of Band A and a receive signal of Band C are simultaneously transmitted and received, the switches  71  and  73  are in the electrically continuous state, and the switches  72  and  74  are in the electrically discontinuous state. In this case, a transmit signal output from the transmit amplifier  40  is output to the antenna element  2  after passing the transmit path of Band A and the transmit filter  11  via the switch  71  in the electrically continuous state. At the same time, here, part of the transmit signal output from the transmit amplifier  40  flows into the transmit path of Band B and the receive path of Band C via the switches  72  and  74  that are in the electrically discontinuous state, and an unwanted wave having a frequency component of Band B (and Band C) that has entered therein degrades the reception sensitivity in Band C. 
     Whereas, in the radio frequency module  1 B according to the present modified example, OFF capacitances of the switches  72  and  74  and the inductor  80  constitute a filter in a path connecting the common terminal  70   a  and the selection terminal  70   c . Here, adjusting the inductance value of the inductor  80  enables the foregoing filter to have the bandpass characteristics whose attenuation band is Band C. 
     Because of this, when CA is performed using a transmit signal of Band A and a receive signal of Band C, by setting the switches  71  and  73  to the electrically continuous state, setting the switches  72  and  74  to the electrically discontinuous state, and setting the switch  75  to the electrically continuous state, it becomes possible to attenuate an unwanted signal having a frequency component of Band C that has leaked through the switches  72  and  74  and is moving toward the selection terminal  70   c  using the filter made up of the inductor  80  and the switches  72  and  74 . Accordingly, it becomes possible to further improve the reception sensitivity in Band C. 
     Note that the circuit element connected to the selection terminal  70   e  is not limited to the inductor  80 . Any circuit element may be connected to the selection terminal  70   e  provided that the circuit element is a suitable circuit element to have a filter function that attenuates an unwanted signal in a frequency band of Band C in the path connecting the common terminal  70   a  and the selection terminal  70   c . The foregoing suitable circuit element is, for example, at least one of an inductor and a capacitor  80   a , as illustrated in modified example 3 in  FIG.  7 A . 
     OTHER EMBODIMENT 
     The radio frequency modules and the communication device according to the present disclosure are described using the embodiment and the modified examples. However, the present disclosure are not limited to the foregoing embodiment and the modified examples. Other embodiments realized by combining arbitrary constituting elements of the foregoing embodiment and modified examples, modified examples obtained by applying various modifications apparent to those skilled in the art to the foregoing embodiment and modified examples without necessarily departing the scope of the present disclosure, and various devices including a radio frequency module and a communication device according to the present disclosure may also be included in the present disclosure. 
     Furthermore, for example, in the radio frequency modules and the communication devices according to the embodiment and the modified examples, a matching element, such as an inductor, a capacitor, or the like, or a switch circuit may be connected between constituting elements. Note that the inductor may include a wiring line inductor formed by a wiring line connecting constituting elements. 
     The present disclosure can be widely used in communication equipment, such as cellular phones and the like as a radio frequency module and a communication device applicable to a multiband system performing CA. 
     While embodiments of the disclosure have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without necessarily departing from the scope and spirit of the disclosure. The scope of the disclosure, therefore, is to be determined solely by the following claims.