Patent Publication Number: US-11043983-B2

Title: Radio frequency module and communication device including the same

Description:
This is a continuation of International Application No. PCT/JP2019/012477 filed on Mar. 25, 2019 which claims priority from Japanese Patent Application No. 2018-070039 filed on Mar. 30, 2018. The contents of these applications are incorporated herein by reference in their entireties. 
    
    
     BACKGROUND 
     The present disclosure generally relates to a radio frequency module and a communication device including the radio frequency module. The present disclosure particularly relates to a radio frequency module that supports the second-generation mobile communication system (2G) and the fourth or fifth-generation mobile communication system (4G or 5G), and to a communication device including the radio frequency module. 
     Electronic systems using carrier aggregation have been known (see, e.g., Japanese Unexamined Patent Application Publication No. 2017-17691). 
     FIG. 2B in Japanese Unexamined Patent Application Publication No. 2017-17691 illustrates an electronic system that includes one antenna, one diplexer, two antenna switches, eight duplexers, two band select switches, two directional couplers, and two power amplifiers (first and second power amplifiers). 
     In the electronic system described above, the diplexer is connected to the antenna. Also, in this electronic system, the two power amplifiers are each connected, through a corresponding one of the two directional couplers, to a corresponding one of the two band select switches. 
     There have been occasions where a communication device including a low-band radio frequency module and a mid-band radio frequency module is required. The low-band radio frequency module includes a transmitting circuit (first transmitting circuit) having a power amplifier (first power amplifier) for a 2G low-band (first frequency band) and a transmitting circuit (third transmitting circuit) having a power amplifier (third power amplifier) for a 4G or 5G low-band (third frequency band). The mid-band radio frequency module is for a 4G or 5G mid-band. 
     There have also been occasions where, in the communication device described above, the low-band radio frequency module smaller in size than the mid-band radio frequency module is required to include a transmitting circuit (second transmitting circuit) having a power amplifier (second power amplifier) for a 2G mid-band (second frequency band). 
     In this case, in the communication device, a signal path on the output side of the power amplifier for the 2G mid-band needs to be connected through a bypass to the antenna switch of the mid-band radio frequency module. 
     However, for example, when the first frequency band for the first transmitting circuit of the low-band radio frequency module is Band 8 and a receiving circuit for Band 3 is included in the mid-band radio frequency module to perform carrier aggregation, the frequency of a second harmonic wave, which is one of harmonic waves of a transmission signal of the transmission frequency band of Band 8, overlaps the frequency band of the 2G mid-band. As a result, the harmonic wave (or radiation of the harmonic wave) jumps to the second transmitting circuit. There have been cases where the harmonic wave of the transmission signal of Band 8 passes through a bypass to the receiving circuit and this degrades the reception performance of the receiving circuit. 
     BRIEF SUMMARY 
     The present disclosure provides a radio frequency module that can prevent the harmonic wave of a transmission signal of a transmitting circuit supporting 4G or 5G from jumping to a transmitting circuit supporting 2G, and to also provide a communication device that includes the radio frequency module. 
     A radio frequency module according to embodiments of the present disclosure includes a first transmitting circuit, a second transmitting circuit, a bypass terminal, a third transmitting circuit, and a substrate. The first transmitting circuit includes a first power amplifier and a first matching circuit connected to a first output terminal of the first power amplifier. The first transmitting circuit transmits a first transmission signal of a first frequency band for 2G. The second transmitting circuit includes a second power amplifier and a second matching circuit connected to a second output terminal of the second power amplifier. The second transmitting circuit transmits a second transmission signal of a second frequency band for 2G. The second frequency band is higher than the first frequency band. The bypass terminal is connected to an output end of the second transmitting circuit. The third transmitting circuit includes a third power amplifier and a third matching circuit connected to a third output terminal of the third power amplifier. The third transmitting circuit transmits a third transmission signal of a third frequency band for 4G or 5G. The substrate has a first principal surface and a second principal surface opposite each other. The substrate has the first transmitting circuit, the second transmitting circuit, and the third transmitting circuit. A frequency of a harmonic wave of the third transmission signal overlaps the second frequency band. The substrate includes a ground layer. The ground layer is disposed between part of the second transmitting circuit and part of the third transmitting circuit. 
     A communication device according to embodiments of the present disclosure includes a first radio frequency module and a second radio frequency module. The first radio frequency module is the radio frequency module described above. The second radio frequency module includes a fourth transmitting circuit. The fourth transmitting circuit includes a fourth power amplifier. The fourth transmitting circuit transmits a fourth transmission signal of a fourth frequency band for 4G or 5G. The fourth frequency band is higher than the third frequency band. At least part of the second frequency band overlaps at least part of the fourth frequency band. 
     With the radio frequency module and the communication device including the radio frequency module according to embodiments of the present disclosure, the harmonic wave of the third transmission signal of the third transmitting circuit that supports 4G or 5G can be prevented from jumping to the second transmitting circuit that supports 2G. 
     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 diagram of a radio frequency module according to a first embodiment of the present disclosure; 
         FIG. 2  relates to the radio frequency module illustrated in  FIG. 1  and illustrates a detailed circuit configuration of a major part A in  FIG. 1 ; 
         FIG. 3  is a circuit diagram of a communication device including the radio frequency module illustrated in  FIG. 1 ; 
         FIG. 4  is a plan view of the radio frequency module illustrated in  FIG. 1 ; 
         FIG. 5  relates to the radio frequency module illustrated in  FIG. 1  and illustrates a cross-section taken along line Y-Y in  FIG. 4 ; 
         FIG. 6  is a cross-sectional view of a radio frequency module according to a second embodiment of the present disclosure; 
         FIG. 7  is a plan view of a radio frequency module according to a third embodiment of the present disclosure; and 
         FIG. 8  is a plan view of a radio frequency module according to a fourth embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 4  to  FIG. 8  that are referred to in the following description of first to fourth embodiments are schematic diagrams, in which the sizes and thicknesses of illustrated components and their ratios do not necessarily reflect the actual dimensional ratios. 
     First Embodiment 
     A radio frequency module and a communication device including the radio frequency module according to a first embodiment will now be described with reference to the drawings. 
     (1) Circuit Configurations of Radio Frequency Module and Communication Device Including the Same 
     A radio frequency module  1  and a communication device  400  including the radio frequency module  1  according to the first embodiment will now be described with reference to  FIG. 1  to  FIG. 3 . The radio frequency module  1  according to the first embodiment constitutes, for example, a radio frequency front end circuit  250  of a mobile communication device (e.g., mobile phone) which is a multiband device that supports simultaneous use of two frequency bands (e.g., carrier aggregation). The radio frequency module  1  is a module that can support carrier aggregation of a 2G mid-band and a 4G low-band, but the radio frequency module  1  is not limited to this. For example, the radio frequency module  1  may be a module that can support dual connectivity of a 2G mid-band and a 5G low-band. For example, 2G is the Global System for Mobile Communications (GSM) (registered trademark), 4G is the Third Generation Partnership Project Long-Term Evolution (3GPP LTE), and 5G is the 5G New Radio (5G NR). Examples of a GSM (registered trademark) low-band include GSM 850 and GSM 900. Examples of a GSM (registered trademark) mid-band include GSM 1800 and GSM 1900. Examples of a 3GPP LTE mid-band include Band 3. The downlink frequency band of Band 3 ranges from about 1805 MHz to about 1880 MHz, and the uplink frequency band of Band 3 ranges from about 1710 MHz to about 1785 MHz. 
     The communication device  400  including the radio frequency module  1  can support carrier aggregation (downlink carrier aggregation) that enables simultaneous use of a plurality of (or two, in the first embodiment) frequency bands in downlink. The communication device  400  including the radio frequency module  1  can also support carrier aggregation (uplink carrier aggregation) that enables simultaneous use of a plurality of (or two, in the first embodiment) frequency bands in uplink. Examples of a 3GPP LTE low-band include Band 8. The downlink frequency band of Band 8 ranges from about 925 MHz to about 960 MHz, and the uplink frequency band of Band 8 ranges from about 880 MHz to about 915 MHz. The communication device  400  including the radio frequency module  1  may support dual connectivity, instead of carrier aggregation. In this case, a 5G NR low-band is, for example, n8. The downlink frequency band of n8 ranges from about 925 MHz to about 960 MHz, and the uplink frequency band of n8 ranges from about 880 MHz to about 915 MHz. 
     (1.1) Circuit Configuration of Radio Frequency Module 
     As illustrated in  FIG. 1 , the radio frequency module  1  includes a first transmitting circuit  110 , a second transmitting circuit  120 , and a third transmitting circuit  130 . The first transmitting circuit  110  includes a first power amplifier  11  and a first matching circuit  14 . The second transmitting circuit  120  includes a second power amplifier  12  and a second matching circuit  15 . The third transmitting circuit  130  includes a third power amplifier  13  and a third matching circuit  16 . The radio frequency module  1  also includes a low-band antenna terminal T 10 , a first low-band signal input terminal T 11 , a mid-band signal input terminal T 12 , and a second low-band signal input terminal T 13 . The radio frequency module  1  also includes a bypass terminal T 15  and a low-band antenna switch  19 . The radio frequency module  1  also includes a plurality of low-band signal output terminals T 81 , T 82 , and T 83 . 
     The first power amplifier  11  has a first input terminal  111  and a first output terminal  112 . The first power amplifier  11  amplifies a first transmission signal of the 2G low-band received as input through the first input terminal  111 , and outputs the amplified first transmission signal from the first output terminal  112 . The first transmission signal is a transmission signal of a first frequency band for 2G. The first input terminal  111  is connected to the first low-band signal input terminal T 11 . The first output terminal  112  is connected to the first matching circuit  14 . 
     The second power amplifier  12  has a second input terminal  121  and a second output terminal  122 . The second power amplifier  12  amplifies a second transmission signal of the 2G mid-band received as input through the second input terminal  121 , and outputs the amplified second transmission signal from the second output terminal  122 . The second transmission signal is a transmission signal of a second frequency band for 2G. The lower limit frequency of the second frequency band is higher than the upper limit frequency of the first frequency band. The second input terminal  121  is connected to the mid-band signal input terminal T 12 . The second output terminal  122  is connected to the second matching circuit  15 . 
     The third power amplifier  13  has a third input terminal  131  and a third output terminal  132 . The third power amplifier  13  amplifies a third transmission signal of the 4G or 5G low-band received as input through the third input terminal  131 , and outputs the amplified third transmission signal from the third output terminal  132 . The third transmission signal is a transmission signal of a third frequency band for 4G or 5G. The third input terminal  131  is connected to the second low-band signal input terminal T 13 . The third output terminal  132  is connected to the third matching circuit  16 . 
     The frequency band (first frequency band) of the first transmission signal includes, for example, the frequency band of GSM 850 and the frequency band of GSM 900. The frequency band (second frequency band) of the second transmission signal includes, for example, the frequency band of GSM 1800 and the frequency band of GSM 1900. The frequency band (third frequency band) of the third transmission signal includes, for example, the frequency band of LTE Band 8. 
     The low-band antenna terminal T 10  is electrically connected to an antenna  200  (see  FIG. 3 ). 
     The bypass terminal T 15  is electrically connected to the second output terminal  122  of the second power amplifier  12 . More specifically, the bypass terminal T 15  is electrically connected through the second matching circuit  15  to the second output terminal  122  of the second power amplifier  12 . 
     The low-band antenna switch  19  is disposed between the low-band antenna terminal T 10  and the first output terminal  112  of the first power amplifier  11  and the third output terminal  132  of the third power amplifier  13 . The low-band antenna switch  19  has one common terminal  190  and a plurality of (four) selection terminals  191 ,  192 ,  193 , and  194 . The common terminal  190  of the low-band antenna switch  19  is connected to the low-band antenna terminal T 10 . 
     The first matching circuit  14  is disposed between the first output terminal  112  of the first power amplifier  11  and the selection terminal  191  of the low-band antenna switch  19 . The first matching circuit  14  is an impedance matching circuit for matching the output impedance of a circuit disposed before the first matching circuit  14  and the input impedance of a circuit disposed after the first matching circuit  14 . More specifically, on one side of the first power amplifier  11  adjacent to the low-band antenna terminal T 10 , the first matching circuit  14  adjusts the impedance at the fundamental frequency of the first transmission signal (i.e., the output impedance of the first power amplifier  11 ) to, for example, about 50Ω. 
     The second matching circuit  15  is disposed between the second output terminal  122  of the second power amplifier  12  and the bypass terminal T 15 . The second matching circuit  15  is an impedance matching circuit for matching the output impedance of a circuit disposed before the second matching circuit  15  and the input impedance of a circuit disposed after the second matching circuit  15 . More specifically, on one side of the second power amplifier  12  adjacent to the bypass terminal T 15 , the second matching circuit  15  adjusts the impedance at the fundamental frequency of the second transmission signal (i.e., the output impedance of the second power amplifier  12 ) to, for example, about 50Ω. 
     The third matching circuit  16  is disposed between the third output terminal  132  of the third power amplifier  13  and the selection terminals  192  to  194  of the low-band antenna switch  19 . The radio frequency module  1  includes a low-band band switch  17  and a plurality of (three) low-band duplexers  81 ,  82 , and  83  between the third matching circuit  16  and the low-band antenna switch  19 . This means that the third matching circuit  16  is disposed between the third output terminal  132  of the third power amplifier  13  and the low-band band switch  17 . The third matching circuit  16  is an impedance matching circuit for matching the output impedance of a circuit disposed before the third matching circuit  16  and the input impedance of a circuit disposed after the third matching circuit  16 . More specifically, on one side of the third power amplifier  13  adjacent to the low-band antenna terminal T 10 , the third matching circuit  16  adjusts the impedance at the fundamental frequency of the third transmission signal (i.e., the output impedance of the third power amplifier  13 ) to, for example, about 50Ω. 
     The low-band duplexers  81  to  83 , each includes a reception filter and a transmission filter. The reception filter is a filter that allows signals of a reception frequency band to pass therethrough and attenuates signals of frequencies outside the reception frequency band. The transmission filter is a filter that allows signals of a transmission frequency band to pass therethrough and attenuates signals of frequencies outside the transmission frequency band. Although the reception filter and the transmission filter described herein are both, for example, surface acoustic wave (SAW) filters, they do not necessarily need to be SAW filters. For example, the reception filter and the transmission filter may be bulk acoustic wave (BAW) filters or dielectric filters. 
     The low-band duplexers  81  to  83  have different transmission frequency bands and different reception frequency bands. 
     The low-band duplexers  81 ,  82 , and  83  have antenna-side terminals Ax 1 , Ax 2 , and Ax 3 , respectively. At the same time, the low-band duplexers  81 ,  82 , and  83  have transmitting terminals Tx 1 , Tx 2 , and Tx 3 , respectively, and have receiving terminals Rx 1 , Rx 2 , and Rx 3 , respectively. The antenna-side terminals Ax 1  to Ax 3  of the low-band duplexers  81  to  83  are connected to the low-band antenna switch  19 . In the low-band duplexers  81  to  83 , the output terminals of the reception filters are used as the receiving terminals Rx 1 , Rx 2 , and Rx 3 , which are connected to the low-band signal output terminals T 81 , T 82 , and T 83 , respectively. Also, in the low-band duplexers  81  to  83 , the input terminals of the transmission filters are used as the transmitting terminals Tx 1 , Tx 2 , and Tx 3 , which are connected to selection terminals  171 ,  172 , and  173 , respectively, of the low-band band switch  17 . Also, in the low-band duplexers  81  to  83 , terminals (ANT terminals), each connected to the output terminal of the transmission filter and the input terminal of the reception filter, are used as the antenna-side terminals Ax 1 , Ax 2 , and Ax 3 , which are connected to the selection terminals  192 ,  193 , and  194 , respectively, of the low-band antenna switch  19 . 
     The low-band antenna switch  19  is disposed between the low-band antenna terminal T 10  and the plurality of (three) low-band duplexers  81  to  83 . Of the four selection terminals  191  to  194  of the low-band antenna switch  19 , one selection terminal  191  is connected to the first matching circuit  14 , and the remaining three selection terminals  192 ,  193 , and  194  are connected one-to-one to the low-band duplexers  81 ,  82 , and  83 , respectively. The low-band antenna switch  19  is, for example, a switch integrated circuit (IC). 
     The low-band band switch  17  is disposed between the third output terminal  132  of the third power amplifier  13  and the transmitting terminals Tx 1  to Tx 3  of the low-band duplexers  81  to  83 . The low-band band switch  17  allows one of the low-band duplexers  81  to  83  to be connected to the third output terminal  132  of the third power amplifier  13 . 
     The radio frequency module  1  further includes a control circuit  100 . For example, the control circuit  100  receives a control signal from a baseband signal processing circuit  402  (see  FIG. 3 ) and controls the first power amplifier  11 , the second power amplifier  12 , the third power amplifier  13 , the low-band antenna switch  19 , and the low-band band switch  17  on the basis of the control signal. The control circuit  100  is, for example, an IC. 
     As illustrated in  FIG. 2 , the second matching circuit  15  includes a plurality of (six) inductors L 1 , L 2 , L 3 , L 4 , L 5 , and L 6 . The second matching circuit  15  also includes a plurality of (five) capacitors C 1 , C 2 , C 3 , C 4 , and C 5 . In the second matching circuit  15 , the inductor L 1  is connected at one end thereof to the second output terminal  122  of the second power amplifier  12 , and is connected at the other end thereof to the bypass terminal T 15  through a series circuit of the two inductors L 2  and L 3  and the capacitor C 1 . In the second matching circuit  15 , the capacitor C 2  is connected between a node of the two inductors L 1  and L 2  and the ground. Also, in the second matching circuit  15 , a series circuit of the capacitor C 3  and the inductor L 4  is connected in parallel to the capacitor C 2 . Also, in the second matching circuit  15 , a series circuit of the capacitor C 4  and the inductor L 5  is connected between the node of the two inductors L 2  and L 3  and the ground. Also, in the second matching circuit  15 , a series circuit of the capacitor C 5  and the inductor L 6  is connected between the node of the inductor L 3  and the capacitor C 1  and the ground. The second matching circuit  15  also serves as a filter. The first matching circuit  14  includes a plurality of (two) inductors L 11  and L 12  and a plurality of (two) capacitors C 11  and C 12  (see  FIG. 4 ). The first matching circuit  14  also serves as a filter. The third matching circuit  16  includes a plurality of (two) inductors L 21  and L 22  and a plurality of (two) capacitors C 21  and C 22  (see  FIG. 4 ). 
     The radio frequency module  1  further includes a bias circuit  18  (see  FIG. 2 ). The bias circuit  18  is a circuit for supplying a bias voltage Vcc from the control circuit  100  to the second power amplifier  12 . The bias circuit  18  includes an inductor L 0  and a capacitor C 0 . The inductor L 0  is electrically connected at one end thereof to the control circuit  100 , and is electrically connected at the other end thereof to the second output terminal  122  of the second power amplifier  12 . For example, the control circuit  100  controls the second power amplifier  12  by varying the voltage value of the operating voltage Vcc supplied through the bias circuit  18  to the second power amplifier  12 . 
     (1.2) Circuit Configuration of Communication Device 
     As illustrated in  FIG. 3 , the communication device  400  includes a diplexer  300 , the radio frequency module  1  (which may hereinafter be also referred to as “first radio frequency module  1 ”), and a second radio frequency module  2 . The communication device  400  further includes an RF signal processing circuit  401  and the baseband signal processing circuit  402 . 
     The diplexer  300  includes a low-band filter  301  and a mid-band filter  302 , and is connected to the antenna  200 . The low-band filter  301  is a low-pass filter, and the mid-band filter  302  is a high-pass filter. 
     The first radio frequency module  1  is electrically connected to the low-band filter  301  of the diplexer  300 . This allows the first radio frequency module  1  to be electrically connected to the antenna  200  through the low-band filter  301 . 
     The second radio frequency module  2  is electrically connected to the mid-band filter  302  of the diplexer  300 . This allows the second radio frequency module  2  to be electrically connected to the antenna  200  through the mid-band filter  302 . 
     In the first radio frequency module  1 , the low-band antenna terminal T 10  is connected to the low-band filter  301 . 
     The first low-band signal input terminal T 11 , the mid-band signal input terminal T 12 , the second low-band signal input terminal T 13 , and the low-band signal output terminals T 81 , T 82 , and T 83  of the first radio frequency module  1  are connected to the RF signal processing circuit  401 . 
     The second radio frequency module  2  includes a mid-band antenna terminal T 20 , a fourth transmitting circuit  210  including a fourth power amplifier  21 , a mid-band signal input terminal T 21 , and a mid-band antenna switch  24 . The second radio frequency module  2  also includes a mid-band transmission path MT 1 , a plurality of (three) mid-band duplexers  31 ,  32 , and  33 , a mid-band band switch  22 , and a plurality of (three) mid-band signal output terminals T 31 , T 32 , and T 33 . The second radio frequency module  2  further includes a relay terminal T 25  connected to the mid-band transmission path MT 1 . 
     The mid-band antenna terminal T 20  is connected to the mid-band filter  302  of the diplexer  300 . 
     The fourth power amplifier  21  has a fourth input terminal  211  and a fourth output terminal  212 . The fourth power amplifier  21  amplifies a fourth transmission signal of the 4G or 5G mid-band received as input through the fourth input terminal  211 , and outputs the amplified fourth transmission signal from the fourth output terminal  212 . The fourth transmission signal is a transmission signal of a fourth frequency band for 4G or 5G. The fourth input terminal  211  of the fourth power amplifier  21  is connected to the mid-band signal input terminal T 21 . 
     The mid-band antenna switch  24  is disposed between the fourth output terminal  212  of the fourth power amplifier  21  and the mid-band antenna terminal T 20 . The mid-band antenna switch  24  is disposed between the mid-band antenna terminal T 20  and the plurality of (three) mid-band duplexers  31  to  33 . The mid-band antenna switch  24  has one common terminal  240  and a plurality of (four) selection terminals  241 ,  242 ,  243 , and  244 . The common terminal  240  of the mid-band antenna switch  24  is connected to the mid-band antenna terminal T 20 . Of the four selection terminals  241  to  244  of the mid-band antenna switch  24 , three selection terminals  241 ,  242 , and  243  are connected one-to-one to the mid-band duplexers  31 ,  32 , and  33 , respectively, and the remaining one selection terminal  244  is connected through the mid-band transmission path MT 1  to the relay terminal T 25 . The mid-band antenna switch  24  is, for example, a switch IC. The mid-band antenna switch  24  has an isolation of, for example, about 20 dB to 30 dB. 
     The mid-band transmission path MT 1  is connected to the mid-band antenna switch  24 , and connected also to the bypass terminal T 15  of the first radio frequency module  1 . More specifically, the mid-band transmission path MT 1  is connected through the relay terminal T 25  to the bypass terminal T 15  of the first radio frequency module  1 . 
     The plurality of (three) mid-band duplexers  31 ,  32 , and  33  have antenna-side terminals Ax 4 , Ax 5 , and Ax 6 , respectively. At the same time, the mid-band duplexers  31 ,  32 , and  33  have transmitting terminals Tx 4 , Tx 5 , and Tx 6 , respectively, and have receiving terminals Rx 4 , Rx 5 , and Rx 6 , respectively. The antenna-side terminals Ax 4  to Ax 6  of the mid-band duplexers  31  to  33  are connected to the mid-band antenna switch  24 . In the mid-band duplexers  31  to  33 , the output terminals of the reception filters are used as the receiving terminals Rx 4 , Rx 5 , and Rx 6 , which are connected to the mid-band signal output terminals T 31 , T 32 , and T 33 , respectively. Also, in the mid-band duplexers  31  to  33 , the input terminals of the transmission filters are used as the transmitting terminals Tx 4 , Tx 5 , and Tx 6 , which are connected to selection terminals  221 ,  222 , and  223 , respectively, of the mid-band band switch  22 . Also, in the mid-band duplexers  31  to  33 , terminals (ANT terminals), each connected to the output terminal of the transmission filter and the input terminal of the reception filter, are used as the antenna-side terminals Ax 4 , Ax 5 , and Ax 6 , which are connected to the selection terminals  241 ,  242 , and  243 , respectively, of the mid-band antenna switch  24 . 
     The mid-band band switch  22  is disposed between the fourth output terminal  212  of the fourth power amplifier  21  and the transmitting terminals Tx 4 , Tx 5 , and Tx 6  of the mid-band duplexers  31 ,  32 , and  33 . The mid-band band switch  22  allows one of the mid-band duplexers  31  to  33  to be connected to the fourth output terminal  212  of the fourth power amplifier  21 . 
     The plurality of (three) mid-band signal output terminals T 31 , T 32 , and T 33  are connected one-to-one to the receiving terminals Rx 4 , Rx 5 , and Rx 6 , respectively, of the plurality of (three) mid-band duplexers  31 ,  32 , and  33 . 
     The RF signal processing circuit  401  is connected to the first radio frequency module  1  and the second radio frequency module  2 . More specifically, the RF signal processing circuit  401  is connected to the first low-band signal input terminal T 11 , the mid-band signal input terminal T 12 , the second low-band signal input terminal T 13 , and the low-band signal output terminals T 81 , T 82 , and T 83  of the first radio frequency module  1 . At the same time, the RF signal processing circuit  401  is connected to the mid-band signal input terminal T 21  and the mid-band signal output terminals T 31 , T 32 , and T 33  of the second radio frequency module  2 . 
     The RF signal processing circuit  401  is, for example, a radio frequency IC (RFIC) and performs signal processing on a radio frequency signal (reception signal) output from the low-band signal output terminals T 81 , T 82 , and T 83  and the mid-band signal output terminals T 31 , T 32 , and T 33 . The RF signal processing circuit  401  also performs signal processing, such as downconversion, on a radio frequency signal (reception signal) received through the first radio frequency module  1  or the second radio frequency module  2  as input from the antenna  200 , and outputs the resulting reception signal (generated by the signal processing) to the baseband signal processing circuit  402 . 
     The baseband signal processing circuit  402  is, for example, a baseband IC (BBIC). A reception signal generated by processing in the baseband signal processing circuit  402  is used, for example, as an image signal for image display, or as an audio signal for conversation. 
     The RF signal processing circuit  401  also performs signal processing, such as upconversion, on a transmission signal output from the baseband signal processing circuit  402 , and outputs the resulting transmission signal (or radio frequency signal generated by the signal processing) to the first radio frequency module  1  or the second radio frequency module  2 . The baseband signal processing circuit  402  performs, for example, predetermined processing on a transmission signal from outside the communication device  400 . 
     The communication device  400  further includes a bypass  180  and a control circuit  20 . 
     The bypass  180  electrically connects the bypass terminal T 15  to the mid-band transmission path MT 1 . More specifically, the bypass  180  electrically connects the bypass terminal T 15  to the relay terminal T 25  connected to the mid-band transmission path MT 1 . The bypass  180  includes, for example, a wiring conductor on a printed wiring board having the first radio frequency module  1  and the second radio frequency module  2  mounted thereon. In this case, the communication device  400  includes the printed wiring board as its component. 
     The control circuit  20  switches the mid-band antenna switch  24  so as to enable one of the mid-band duplexers  31  to  33  and the mid-band transmission path MT 1  to be connected to the mid-band filter  302  of the diplexer  300 . 
     In the communication device  400 , the first frequency band of the first transmission signal includes the frequency band of GSM 850 and the frequency band of GSM 900. The second frequency band of the second transmission signal includes the frequency band of GSM 1800 and the frequency band of GSM 1900. The third frequency band of the third transmission signal includes the frequency band of LTE Band 8. The fourth frequency band of the fourth transmission signal includes the frequency band of LTE Band 3. Of the mid-band duplexers  31 ,  32 , and  33 , the mid-band duplexer  31  is a duplexer that supports 4G or 5G. For example, the mid-band duplexer  31  is a duplexer for Band 3 of LTE or n8 of 5G NR. In the second radio frequency module  2 , a signal path between the mid-band antenna switch  24  and the mid-band signal output terminal T 31  constitutes a mid-band reception path MR 1 . This enables the communication device  400  to support downlink carrier aggregation of Band 8 and Band 3 or dual connectivity of n8 and Band 3. The mid-band duplexer  32  is a duplexer that supports 4G or 5G. For example, the mid-band duplexer  32  is a duplexer for LTE Band 12. The mid-band duplexer  33  is a duplexer that supports 4G or 5G. For example, the mid-band duplexer  33  is a duplexer for LTE Band 20. 
     (2) Structure of Radio Frequency Module 
     A structure of the radio frequency module  1  will now be described with reference to  FIG. 4  and  FIG. 5 . 
     As described above, the radio frequency module  1  includes the first transmitting circuit  110  including the first power amplifier  11  and the first matching circuit  14 , the second transmitting circuit  120  including the second power amplifier  12  and the second matching circuit  15 , and the third transmitting circuit  130  including the third power amplifier  13  and the third matching circuit  16 . The radio frequency module  1  also includes the low-band antenna terminal T 10 , the bypass terminal T 15 , the low-band band switch  17 , and the low-band antenna switch  19 . Also, the radio frequency module  1  includes a substrate  5 . The substrate  5  has at least the first power amplifier  11 , the second power amplifier  12 , and the third power amplifier  13  mounted thereon. The substrate  5  also has the low-band antenna switch  19  mounted thereon. 
     In the radio frequency module  1 , the first power amplifier  11  and the second power amplifier  12  are integrated into a single semiconductor chip  10 . The third power amplifier  13  forms a semiconductor chip different from the semiconductor chip  10 . 
     In the radio frequency module  1 , the low-band band switch  17  is a switch IC, and the low-band antenna switch  19  is also a switch IC. The low-band band switch  17  and the low-band antenna switch  19  are mounted on the substrate  5 . An IC constituting the control circuit  100  is also mounted on the substrate  5 . 
     The inductors L 11  and L 12  of the first matching circuit  14  are, for example, chip inductors. The capacitors C 11  and C 12  of the first matching circuit  14  are chip capacitors. The inductors L 11  and L 12  and the capacitors C 11  and C 12  of the first matching circuit  14  are mounted on the substrate  5 . 
     Of the inductors L 1  to L 6  of the second matching circuit  15 , the inductors L 1 , L 2 , L 3 , L 5 , and L 6  are chip inductors mounted on the substrate  5 , whereas the inductor L 4  is an internal inductor formed in the substrate  5 . The capacitors C 1  to C 5  of the second matching circuit  15  are chip capacitors mounted on the substrate  5 . 
     The inductors L 21  and L 22  of the third matching circuit  16  are, for example, chip inductors. The capacitors C 21  and C 22  of the third matching circuit  16  are chip capacitors. The inductors L 21  and L 22  and the capacitors C 21  and C 22  of the third matching circuit  16  are mounted on the substrate  5 . 
     The substrate  5  is a multilayer substrate including a plurality of dielectric layers and a plurality of conductor pattern layers. More specifically, the substrate  5  is a printed wiring board. The dielectric layers and the conductor pattern layers are stacked in the direction of thickness (hereinafter referred to as “thickness direction D 1 ”) of the substrate  5 . The conductor pattern layers are each formed in a predetermined pattern. The conductor pattern layers, each includes one or more conductor portions in a plane orthogonal to the thickness direction D 1  of the substrate  5 . For example, the conductor pattern layers are made of copper. 
     The substrate  5  includes a dielectric substrate  51  and a ground layer  52 . The substrate  5  has a first principal surface  511  and a second principal surface  512  opposite each other. The first principal surface  511  and the second principal surface  512  are surfaces that intersect the thickness direction D 1  of the substrate  5 . The ground layer  52  is separated from the first principal surface  511 . More specifically, in the dielectric substrate  51 , the ground layer  52  is separated from the first principal surface  511  in the thickness direction D 1  of the substrate  5 . In a plane orthogonal to the thickness direction D 1 , the ground layer  52  has substantially the same area as the dielectric substrate  51 . The ground layer  52  has a hole  520  for avoiding short circuit with a through electrode  53  (described below). Accordingly, in the plane orthogonal to the thickness direction D 1 , the area of the ground layer  52  is smaller than the area of the dielectric substrate  51  by the opening area of the hole  520 . With the ground layer  52 , the substrate  5  can enhance isolation, for example, between the conductor pattern layers adjacent to the first principal surface  511  and the conductor pattern layers adjacent to the second principal surface  512 . In other words, it is possible to enhance isolation between the first principal surface  511  and the second principal surface  512  of the substrate  5 . 
     The dielectric substrate  51  includes a plurality of dielectric layers. The dielectric substrate  51  is electrically insulating and substantially in the shape of a plate. In plan view from the thickness direction D 1  of the substrate  5 , the dielectric substrate  51  and the substrate  5  are, for example, substantially rectangular in shape. However, the shape is not limited to this and the dielectric substrate  51  and the substrate  5  may be substantially square in shape. 
     The ground layer  52  is constituted by one of the plurality of conductor pattern layers. For example, the ground layer  52  is a ground electrode to which a ground potential is applied. The ground layer  52  is disposed closer to the second principal surface  512  of the substrate  5  than to the first principal surface  511  of the substrate  5 . 
     In the radio frequency module  1 , the low-band antenna terminal T 10 , the first low-band signal input terminal T 11 , the mid-band signal input terminal T 12 , the second low-band signal input terminal T 13 , the bypass terminal T 15 , and the low-band signal output terminals T 81 , T 82 , and T 83  are disposed to protrude from the second principal surface  512  of the substrate  5  to serve as external connection terminals. Also, in the radio frequency module  1 , a ground terminal  59  connected to the ground layer  52  through a via conductor  55  is disposed to protrude from the second principal surface  512  of the substrate  5  to serve as an external connection terminal. 
     In the radio frequency module  1 , the semiconductor chip  10  (i.e., the first power amplifier  11  and the second power amplifier  12 ), the third power amplifier  13 , and the third matching circuit  16  are disposed on the first principal surface  511  of the substrate  5 . The semiconductor chip  10  and the third power amplifier  13  are flip-chip mounted on the substrate  5 . As for the second matching circuit  15  connected to the second output terminal  122  of the second power amplifier  12 , at least the inductor L 1  of the inductors L 1  to L 6  is disposed closer to the second principal surface  512  of the substrate  5  than to the first principal surface  511  of the substrate  5 . More specifically, at least the inductor L 1  of the inductors L 1  to L 6  is disposed on one side of the ground layer  52  adjacent to the second principal surface  512 , in the thickness direction D 1  of the substrate  5 . In the radio frequency module  1  according to the first embodiment, the inductors L 1  to L 6  are disposed closer to the second principal surface  512  of the substrate  5  than to the first principal surface  511  of the substrate  5 . 
     The inductor L 1  is disposed on the second principal surface  512  of the substrate  5  opposite the first principal surface  511 . That is, the inductor L 1  is surface-mounted on the substrate  5 . In the radio frequency module  1  of the first embodiment, the second power amplifier  12  overlaps the inductor L 1  in the thickness direction D 1  of the substrate  5 . The substrate  5  of the radio frequency module  1  includes the through electrode  53 . The through electrode  53  penetrates the dielectric substrate  51  in the thickness direction D 1  to connect the inductor L 1  to the second output terminal  122  of the second power amplifier  12 . The second principal surface  512  of the substrate  5  includes the surface of a conductor pattern layer including a wiring conductor  54  that connects the inductor L 1  to the capacitor C 3 . 
     The inductor L 4  of the second matching circuit  15  is disposed inside the substrate  5 . 
     The radio frequency module  1  further includes a cover layer  6  (see  FIG. 5 ) on the first principal surface  511  of the substrate  5 . The cover layer  6  covers, for example, a plurality of electronic components mounted on the substrate  5 . Examples of the electronic components include the semiconductor chip  10  (i.e., the semiconductor chip including the first power amplifier  11  and the second power amplifier  12 ), the third power amplifier  13 , the two inductors L 11  and L 12  and the two capacitors C 11  and C 12  of the first matching circuit  14 , the two inductors L 21  and L 22  and the two capacitors C 21  and C 22  of the third matching circuit  16 , the low-band duplexers  81  to  83 , the low-band antenna switch  19 , the low-band band switch  17 , and the control circuit  100 . Note that the cover layer  6  is not shown in  FIG. 4 . 
     The cover layer  6  is electrically insulating and configured to seal the electronic components. For example, the cover layer  6  is made of an electrically insulating resin (e.g., epoxy resin). The cover layer  6  has a principal surface  611  that intersects the thickness direction D 1  of the substrate  5  and a side face  613  that extends along the thickness direction D 1 . 
     (3) Advantageous Effects 
     The radio frequency module  1  according to the first embodiment includes the first power amplifier  11 , the second power amplifier  12 , the third power amplifier  13 , the low-band antenna terminal T 10 , the bypass terminal T 15 , the second matching circuit  15 , the third matching circuit  16 , and the substrate  5 . The first power amplifier  11  has the first input terminal  111  and the first output terminal  112 . The first power amplifier  11  amplifies the first transmission signal of the 2G low-band received as input through the first input terminal  111 , and outputs the amplified first transmission signal from the first output terminal  112 . The second power amplifier  12  has the second input terminal  121  and the second output terminal  122 . The second power amplifier  12  amplifies the second transmission signal of the 2G mid-band received as input through the second input terminal  121 , and outputs the amplified second transmission signal from the second output terminal  122 . The third power amplifier  13  has the third input terminal  131  and the third output terminal  132 . The third power amplifier  13  amplifies the third transmission signal of the 4G or 5G low-band received as input through the third input terminal  131 , and outputs the amplified third transmission signal from the third output terminal  132 . The bypass terminal T 15  is electrically connected to the second output terminal  122 . The second matching circuit  15  is electrically connected to the second output terminal  122  and includes one or more inductors L 1  to L 6 . The third matching circuit  16  is electrically connected to the third output terminal  132  and includes one or more inductors L 21  and L 22 . The substrate  5  has thereon the first power amplifier  11 , the second power amplifier  12 , the third power amplifier  13 , the second matching circuit  15 , and the third matching circuit  16  and includes therein the ground layer  52 . The ground layer  52  is disposed between at least the inductor L 1  of the inductors L 1  to L 6  of the second matching circuit  15  and at least one of the inductors L 21  and L 22  of the third matching circuit  16 . 
     The radio frequency module  1  according to the first embodiment can prevent radiation on the output side of the third power amplifier  13 , which is a power amplifier for the 4G or 5G low-band, from jumping to the output side of the second power amplifier  12 , which is a power amplifier for the 2G mid-band. For example, when transmitting the third transmission signal of Band 8 using the third power amplifier  13  for the 4G or 5G low-band, the radio frequency module  1  of the first embodiment can prevent radiation from the at least one of the inductors L 21  and L 22  of the third matching circuit  16  (i.e., harmonic wave of the third transmission signal) from jumping to at least the inductor L 1  of the second matching circuit  15  adjacent to the second output terminal  122  of the second power amplifier  12  for the 2G mid-band. That is, the radio frequency module  1  can prevent magnetic coupling between the at least one of the inductors L 21  and L 22  of the third matching circuit  16  and at least the inductor L 1  of the second matching circuit  15  from causing jumping of radiation. 
     The radio frequency module  1  according to the first embodiment further includes the low-band antenna switch  19  and the reception filter. The low-band antenna switch  19  is disposed between the low-band antenna terminal T 10  and the first output terminal  112  of the first power amplifier  11  and the third output terminal  132  of the third power amplifier  13 . The reception filter is disposed between the low-band antenna switch  19  and the third matching circuit  16  and is for the 4G or 5G low-band. That is, the reception filter allows passage of reception signals of the third frequency band for 4G or 5G. Thus, for example, in two-downlink carrier aggregation of Band 8 and Band 3, the communication device  400  of the first embodiment can prevent the harmonic wave of Band 8 from flowing through the bypass terminal T 15  into the mid-band duplexer  31  of the second radio frequency module  2 , and thus can improve communication performance. The combination of two bands for two-downlink carrier aggregation does not necessarily need to be the combination of Band 8 and Band 3. 
     Note that the communication device  400  does not simultaneously perform transmission in the 2G mid-band and reception in the 4G or 5G mid-band. 
     Second Embodiment 
     A radio frequency module  1   a  according to a second embodiment will now be described with reference to  FIG. 6 . For the radio frequency module  1   a  according to the second embodiment, components that are similar to those of the radio frequency module  1  according to the first embodiment will be denoted by the same reference numerals and their description will be omitted. 
     The radio frequency module  1   a  of the second embodiment differs from the radio frequency module  1  of the first embodiment in that the radio frequency module  1   a  includes a shielding layer  7  that covers the cover layer  6 . 
     The shielding layer  7  is made of metal. The shielding layer  7  covers the principal surface  611  and the side face  613  of the cover layer  6  and part of a side face  513  of the substrate  5 . The shielding layer  7  is in contact with the ground layer  52 . This can make the potential of the shielding layer  7  equal to the potential of the ground layer  52 . 
     Like the radio frequency module  1  of the first embodiment, the radio frequency module  1   a  of the second embodiment can prevent radiation on the output side of the third power amplifier  13 , which is a power amplifier for the 4G or 5G low-band, from jumping to the output side of the second power amplifier  12 , which is a power amplifier for the 2G mid-band. With the shielding layer  7 , the radio frequency module  1   a  of the second embodiment can more effectively reduce the effect of radiation than the radio frequency module  1  of the first embodiment does. The first radio frequency module  1  of the communication device  400  according to the first embodiment may be replaced by the radio frequency module  1   a.    
     Third Embodiment 
     A radio frequency module  1   b  according to a third embodiment will now be described with reference to  FIG. 7 . For the radio frequency module  1   b  according to the third embodiment, components that are similar to those of the radio frequency module  1  according to the first embodiment will be denoted by the same reference numerals and their description will be omitted. 
     Like the radio frequency module  1  of the first embodiment, the radio frequency module  1   b  of the third embodiment includes the semiconductor chip  10 . The semiconductor chip  10  includes the first power amplifier  11  (see  FIG. 1  and  FIG. 5 ) and the second power amplifier  12  (see  FIG. 1  and  FIG. 5 ). The radio frequency module  1   b  of the third embodiment differs from the radio frequency module  1  of the first embodiment in that the second output terminal  122  of the second power amplifier  12  of the semiconductor chip  10  is connected through a bonding wire W 1  to an electrode  150  on the substrate  5 . Like the radio frequency module  1  of the first embodiment, the radio frequency module  1   b  of the third embodiment can prevent radiation on the output side of the third power amplifier  13 , which is a power amplifier for the 4G or 5G low-band, from jumping to the output side of the second power amplifier  12 , which is a power amplifier for the 2G mid-band. The first radio frequency module  1  of the communication device  400  according to the first embodiment may be replaced by the radio frequency module  1   b.    
     Fourth Embodiment 
     A radio frequency module  1   c  according to a fourth embodiment will now be described with reference to  FIG. 8 . For the radio frequency module  1   c  according to the fourth embodiment, components that are similar to those of the radio frequency module  1  according to the first embodiment will be denoted by the same reference numerals and their description will be omitted. 
     The radio frequency module  1   c  of the fourth embodiment differs from the radio frequency module  1  of the first embodiment in that the third output terminal  132  of the third power amplifier  13  is connected through a bonding wire W 2  to an electrode  160  on the substrate  5 . 
     Like the radio frequency module  1  of the first embodiment, the radio frequency module  1   c  of the fourth embodiment includes, as illustrated in  FIG. 1 , the first power amplifier  11 , the second power amplifier  12 , the third power amplifier  13 , the low-band antenna terminal T 10 , the bypass terminal T 15 , the second matching circuit  15 , the third matching circuit  16 , and the substrate  5  (see  FIG. 8 ). The first power amplifier  11  has the first input terminal  111  and the first output terminal  112 . The first power amplifier  11  amplifies the first transmission signal of the 2G low-band received as input through the first input terminal  111 , and outputs the amplified first transmission signal from the first output terminal  112 . The second power amplifier  12  has the second input terminal  121  and the second output terminal  122 . The second power amplifier  12  amplifies the second transmission signal of the 2G mid-band received as input through the second input terminal  121 , and outputs the amplified second transmission signal from the second output terminal  122 . The third power amplifier  13  has the third input terminal  131  and the third output terminal  132 . The third power amplifier  13  amplifies the third transmission signal of the 4G or 5G low-band received as input through the third input terminal  131 , and outputs the amplified third transmission signal from the third output terminal  132 . The bypass terminal T 15  is electrically connected to the second output terminal  122 . The second matching circuit  15  is electrically connected to the second output terminal  122  and includes one or more inductors L 1  to L 6  (see  FIG. 2  and  FIG. 5 ). The third matching circuit  16  is electrically connected to the third output terminal  132  through the bonding wire W 2 , as illustrated in  FIG. 8 , and includes one or more inductors L 21  and L 22 . The substrate  5  has thereon the first power amplifier  11 , the second power amplifier  12 , the third power amplifier  13 , the second matching circuit  15 , and the third matching circuit  16  and includes therein the ground layer  52 . The ground layer  52  is disposed between at least the inductor L 1  of the inductors L 1  to L 6  of the second matching circuit  15  and the bonding wire W 2 . 
     Like the radio frequency module  1  of the first embodiment, the radio frequency module  1   c  of the fourth embodiment can prevent radiation on the output side of the third power amplifier  13 , which is a power amplifier for the 4G or 5G low-band, from jumping to the output side of the second power amplifier  12 , which is a power amplifier for the 2G mid-band. The first radio frequency module  1  of the communication device  400  according to the first embodiment may be replaced by the radio frequency module  1   c.    
     The first to fourth embodiments are merely examples of various embodiments of the present disclosure. As long as the object of the present disclosure is achievable, the first to fourth embodiments may be variously modified, for example, as the design changes. 
     In the radio frequency module  1  of the first embodiment, all the inductors L 1  to L 6  of the second matching circuit  15 , except the inductor L 4 , are mounted on the second principal surface  512  of the substrate  5 . The inductors L 1  to L 6  are all disposed on one side of the ground layer  52  adjacent to the second principal surface  512  in the thickness direction D 1  of the substrate  5 . However, the configuration is not limited to this, and it is suitable, in the radio frequency module  1 , that at least one of the inductors L 1  to L 6  of the second matching circuit  15  be disposed on one side of the ground layer  52  adjacent to the second principal surface  512  in the thickness direction D 1  of the substrate  5 . In the radio frequency module  1 , of the inductors L 1  to L 6 , the inductor L 1  electrically closest to the second output terminal  122  of the second power amplifier  12  can be disposed on the side of the ground layer  52  adjacent to the second principal surface  512  in the thickness direction D 1  of the substrate  5 . 
     All the inductors L 1  to L 6  of the second matching circuit  15  may be disposed on the second principal surface  512  of the substrate  5  opposite the first principal surface  511 . That is, all the inductors L 1  to L 6  may be surface-mounted. 
     The physical configuration of the ground layer  52  is not limited to that in the first to fourth embodiments described above. It is suitable that the ground layer  52  be disposed between part of the second transmitting circuit  120  and part of the third transmitting circuit  130 . That is, in plan view from the thickness direction D 1  of the substrate  5 , the ground layer  52  disposed between part of the second transmitting circuit  120  and part of the third transmitting circuit  130  does not necessarily need to overlap all the components of the second transmitting circuit  120  (e.g., the second power amplifier  12  and the second matching circuit  15 ) and all the components of the third transmitting circuit  130  (e.g., the third power amplifier  13  and the third matching circuit  16 ). For example, the ground layer  52  may be disposed between the second power amplifier  12  or second matching circuit  15  and the third power amplifier  13  or third matching circuit  16 . Although each of the second matching circuit  15  and the third matching circuit  16  serves as a filter (transmission filter), the configuration is not limited to this. For example, the second transmitting circuit  120  may include a transmission filter along with the second matching circuit  15 , and the third transmitting circuit  130  may include a transmission filter along with the third matching circuit  16 . In this case, when the ground layer  52  is disposed between at least the transmission filter of the second transmitting circuit  120  and the transmission filter of the third transmitting circuit  130 , the harmonic wave of the third transmission signal from the third transmitting circuit  130  can be prevented from jumping to the second transmitting circuit  120 . Also, when the third transmitting circuit  130  includes the low-band duplexers  81  to  83 , if the ground layer  52  is disposed between the low-band duplexers  81  to  83  and the transmission filter of the second transmitting circuit  120 , the harmonic wave of the third transmission signal from the third transmitting circuit  130  can be prevented from jumping to the second transmitting circuit  120 . 
     In the radio frequency module  1   c  according to the fourth embodiment, the semiconductor chip  10  including the first power amplifier  11  and the second power amplifier  12  and the third matching circuit  16  are disposed on the first principal surface  511  of the substrate  5 . However, the configuration is not limited to this, and the semiconductor chip  10  and the third matching circuit  16  may be disposed on the second principal surface  512  of the substrate  5 . In this case, the third output terminal  132  of the third power amplifier  13  may be connected through a bonding wire to an electrode on the second principal surface  512  of the substrate  5 . 
     The low-band duplexers  81  to  83  of the radio frequency modules  1 ,  1   a ,  1   b , and  1   c  according to the first, second, third, and fourth embodiments may each be replaced by a transmission filter and a reception filter. The low-band duplexers  81  to  83  do not necessarily need to be mounted on the substrate  5 . The low-band duplexers  81  to  83  of the radio frequency modules  1 ,  1   a ,  1   b , and  1   c  according to the first, second, third, and fourth embodiments may each be replaced by a multiplexer. 
     Any of the radio frequency modules  1 ,  1   a ,  1   b , and  1   c  according to the first, second, third, and fourth embodiments may include some or all the components of the second radio frequency module  2 . Any of the radio frequency modules  1 ,  1   a ,  1   b , and  1   c  according to the first, second, third, and fourth embodiments may include some or all the components of the second radio frequency module  2  and the diplexer  300 . 
     The communication device  400  may have any configuration that supports at least two downlinks. For example, the communication device  400  may be configured to support three downlinks. In this case, the communication device  400  may include a triplexer, instead of the diplexer  300 . 
     SUMMARY 
     The embodiments described above disclose the following aspects of the present disclosure. 
     A radio frequency module ( 1 ,  1   a ,  1   b , or  1   c ) according to a first aspect includes a first transmitting circuit ( 110 ), a second transmitting circuit ( 120 ), a bypass terminal (T 15 ), a third transmitting circuit ( 130 ), and a substrate ( 5 ). The first transmitting circuit ( 110 ) includes a first power amplifier ( 11 ) and a first matching circuit ( 14 ) connected to a first output terminal ( 112 ) of the first power amplifier ( 11 ). The first transmitting circuit ( 110 ) transmits a first transmission signal of a first frequency band for 2G. The second transmitting circuit ( 120 ) includes a second power amplifier ( 12 ) and a second matching circuit ( 15 ) connected to a second output terminal ( 122 ) of the second power amplifier ( 12 ). The second transmitting circuit ( 120 ) transmits a second transmission signal of a second frequency band for 2G. The second frequency band is higher than the first frequency band. The bypass terminal (T 15 ) is connected to an output end of the second transmitting circuit ( 120 ). The third transmitting circuit ( 130 ) includes a third power amplifier ( 13 ) and a third matching circuit ( 16 ) connected to a third output terminal ( 132 ) of the third power amplifier ( 13 ). The third transmitting circuit ( 130 ) transmits a third transmission signal of a third frequency band for 4G or 5G. The substrate ( 5 ) has a first principal surface ( 511 ) and a second principal surface ( 512 ) opposite each other. The substrate ( 5 ) has the first transmitting circuit ( 110 ), the second transmitting circuit ( 120 ), and the third transmitting circuit ( 130 ). A frequency of a harmonic wave of the third transmission signal overlaps the second frequency band. The substrate ( 5 ) includes a ground layer ( 52 ). The ground layer ( 52 ) is disposed between part of the second transmitting circuit ( 120 ) and part of the third transmitting circuit ( 130 ). 
     The radio frequency modules ( 1 ,  1   a ,  1   b , and  1   c ) according to the first aspect can prevent the harmonic wave of the third transmission signal of the third transmitting circuit ( 130 ) supporting 4G or 5G from jumping to the second transmitting circuit ( 120 ) supporting 2G. 
     According to a second aspect, in the radio frequency module ( 1 ,  1   a ,  1   b , or  1   c ) according to the first aspect, the second matching circuit ( 15 ) of the second transmitting circuit ( 120 ) is mounted on the second principal surface ( 512 ) of the substrate ( 5 ) and the third matching circuit ( 16 ) of the third transmitting circuit ( 130 ) is mounted on the first principal surface ( 511 ) of the substrate ( 5 ). The ground layer ( 52 ) is disposed between the second matching circuit ( 15 ) and the third matching circuit ( 16 ). 
     According to a third aspect, in the radio frequency module ( 1 ,  1   a ,  1   b , or  1   c ) according to the first or second aspect, the second matching circuit ( 15 ) includes one or more inductors (L 1  to L 6 ) and the third matching circuit ( 16 ) includes one or more inductors (L 21  and L 22 ). The ground layer ( 52 ) is disposed between at least one (L 1 ) of the one or more inductors (L 1  to L 6 ) of the second matching circuit ( 15 ) and at least one (L 21  or L 22 ) of the one or more inductors (L 21  and L 22 ) of the third matching circuit ( 16 ). 
     The radio frequency modules ( 1 ,  1   a ,  1   b , and  1   c ) according to the third aspect can prevent the harmonic wave of the third transmission signal from jumping from the third matching circuit ( 16 ) of the third transmitting circuit ( 130 ) supporting 4G or 5G to the second matching circuit ( 15 ) of the second transmitting circuit ( 120 ) supporting 2G. 
     According to a fourth aspect, the radio frequency module ( 1 ,  1   a ,  1   b , or  1   c ) according to any one of the first to third aspects further includes a low-band antenna terminal (T 10 ), a low-band antenna switch ( 19 ), and a reception filter. The low-band antenna switch ( 19 ) is disposed between the low-band antenna terminal (T 10 ) and the first output terminal ( 112 ) of the first power amplifier ( 11 ) and the third output terminal ( 132 ) of the third power amplifier ( 13 ). The reception filter is disposed between the low-band antenna switch ( 19 ) and the third matching circuit ( 16 ), and configured to allow a reception signal of the third frequency band for 4G or 5G to pass therethrough. 
     According to a fifth aspect, the radio frequency module ( 1 ,  1   a ,  1   b , or  1   c ) according to the fourth aspect further includes a plurality of low-band duplexers ( 81 ,  82 , and  83 ), a low-band band switch ( 17 ), and a plurality of low-band signal output terminals (T 81 , T 82 , and T 83 ). The low-band duplexers ( 81 ,  82 , and  83 ), each has a corresponding one of antenna-side terminals (Ax 1 , Ax 2 , and Ax 3 ), a corresponding one of transmitting terminals (Tx 1 , Tx 2 , and Tx 3 ), and a corresponding one of receiving terminals (Rx 1 , Rx 2 , and Rx 3 ). The antenna-side terminals (Ax 1 , Ax 2 , and Ax 3 ) are connected to the low-band antenna switch ( 19 ). The low-band band switch ( 17 ) is disposed between the third output terminal ( 132 ) and the transmitting terminals (Tx 1 , Tx 2 , and Tx 3 ) of the low-band duplexers ( 81 ,  82 , and  83 ). The low-band band switch ( 17 ) connects one of the low-band duplexers ( 81 ,  82 , and  83 ) to the third output terminal ( 132 ). The low-band signal output terminals (T 81 , T 82 , and T 83 ) are connected one-to-one to the respective receiving terminals (Rx 1 , Rx 2 , and Rx 3 ) of the low-band duplexers ( 81 ,  82 , and  83 ). 
     According to a sixth aspect, in the radio frequency module ( 1 ,  1   a ,  1   b , or  1   c ) according to any one of the first to fifth aspects, the first frequency band includes a frequency band of GSM 850 and a frequency band of GSM 900. The second frequency band includes a frequency band of GSM 1800 and a frequency band of GSM 1900. The third frequency band includes a frequency band of Band 8 of LTE or a frequency band of n8 of 5G NR. 
     According to a seventh aspect, in the radio frequency module ( 1 ,  1   a ,  1   b , or  1   c ) according to the third aspect, the first power amplifier ( 11 ) and the third power amplifier ( 13 ) are disposed closer to the first principal surface ( 511 ) of the substrate ( 5 ) than to the second principal surface ( 512 ) of the substrate ( 5 ). At least one inductor (L 1 ) of the second matching circuit ( 15 ) is disposed on the second principal surface ( 512 ) of the substrate ( 5 ) opposite the first principal surface ( 511 ). 
     The radio frequency modules ( 1 ,  1   a ,  1   b , and  1   c ) according to the seventh aspect can prevent radiation on the output side of the third power amplifier ( 13 ) from jumping to the output side (signal path LT 2 ) of the second power amplifier ( 12 ). 
     According to an eighth aspect, in the radio frequency module ( 1 ,  1   a ,  1   b , or  1   c ) according to the seventh aspect, the one or more inductors (L 1  to L 6 ) of the second matching circuit ( 15 ) are disposed on the second principal surface ( 512 ) of the substrate ( 5 ) opposite the first principal surface ( 511 ). 
     The radio frequency modules ( 1 ,  1   a ,  1   b , and  1   c ) according to the eighth aspect can more effectively prevent jumping of the radiation than the radio frequency modules ( 1 ,  1   a ,  1   b , and  1   c ) according to the seventh aspect do. 
     According to a ninth aspect, in the radio frequency module ( 1 ,  1   a ,  1   b , or  1   c ) according to the third aspect, at least one inductor (L 4 ) of the second matching circuit ( 15 ) is disposed inside the substrate ( 5 ). 
     In the radio frequency modules ( 1 ,  1   a ,  1   b , and  1   c ) according to the ninth aspect, the substrate ( 5 ) can be reduced in size. It is also possible to improve flexibility in laying out electronic components on the second principal surface ( 512 ) of the substrate ( 5 ). 
     According to a tenth aspect, in the radio frequency module ( 1 ,  1   a ,  1   b , or  1   c ) according to the first or second aspect, the second matching circuit ( 15 ) is electrically connected to the second output terminal ( 122 ) and includes one or more inductors (L 1  to L 6 ). The third matching circuit ( 16 ) is electrically connected to the third output terminal ( 132 ) through a bonding wire (W 2 ), and includes one or more inductors (L 21  and L 22 ). The ground layer ( 52 ) is disposed between at least one (L 1 ) of the inductors (L 1  to L 6 ) of the second matching circuit ( 15 ) and the bonding wire (W 2 ). 
     According to an eleventh aspect, the radio frequency module ( 1 ,  1   a ,  1   b , or  1   c ) according to any one of the first to tenth aspects further includes a fourth transmitting circuit ( 210 ). The fourth transmitting circuit ( 210 ) includes a fourth power amplifier ( 21 ). The fourth transmitting circuit ( 210 ) transmits a fourth transmission signal of a fourth frequency band for 4G or 5G. The fourth frequency band is higher than the third frequency band. At least part of the second frequency band overlaps at least part of the fourth frequency band. 
     According to a twelfth aspect, the radio frequency module ( 1 ,  1   a ,  1   b , or  1   c ) according to the eleventh aspect further includes a mid-band antenna terminal (T 20 ), a mid-band antenna switch ( 24 ), a mid-band reception path (MR 1 ), and a mid-band transmission path (MT 1 ). The mid-band antenna terminal (T 20 ) is electrically connected to an antenna ( 200 ). The mid-band antenna switch ( 24 ) is connected to the mid-band antenna terminal (T 20 ). The mid-band reception path (MR 1 ) is connected to the mid-band antenna switch ( 24 ) and supports the fourth frequency band. 
     The radio frequency modules ( 1 ,  1   a ,  1   b , and  1   c ) according to the twelfth aspect can support carrier aggregation or dual connectivity. 
     According to a thirteenth aspect, the radio frequency module ( 1 ,  1   a ,  1   b , or  1   c ) according to the fourth aspect further includes a fourth transmitting circuit ( 210 ), a mid-band antenna terminal (T 20 ), a mid-band antenna switch ( 24 ), a mid-band reception path (MR 1 ), a mid-band transmission path (MT 1 ), and a diplexer ( 300 ). The fourth transmitting circuit ( 210 ) includes a fourth power amplifier ( 21 ). The fourth transmitting circuit ( 210 ) transmits a fourth transmission signal of a fourth frequency band for 4G or 5G. The fourth frequency band is higher than the third frequency band. The mid-band antenna terminal (T 20 ) is electrically connected to an antenna ( 200 ). The mid-band antenna switch ( 24 ) is connected to the mid-band antenna terminal (T 20 ). The mid-band reception path (MR 1 ) is connected to the mid-band antenna switch ( 24 ) and supports the fourth frequency band. The diplexer ( 300 ) includes a low-band filter ( 301 ) and a mid-band filter ( 302 ). At least part of the second frequency band overlaps at least part of the fourth frequency band. The low-band antenna terminal (T 10 ) is connected to the low-band filter ( 301 ), and the mid-band antenna terminal (T 20 ) is connected to the mid-band filter ( 302 ). 
     According to a fourteenth aspect, in the radio frequency module ( 1 ,  1   a ,  1   b , or  1   c ) according to the thirteenth aspect, a fourth output terminal ( 212 ) of the fourth power amplifier ( 21 ) is connected to the mid-band antenna switch ( 24 ). 
     A communication device ( 400 ) according to a fifteenth aspect includes a first radio frequency module and a second radio frequency module ( 2 ). The first radio frequency module is one of the radio frequency modules ( 1 ,  1   a ,  1   b , and  1   c ) according to the first to tenth aspects. The second radio frequency module ( 2 ) includes a fourth transmitting circuit ( 210 ) that transmits a fourth transmission signal of a fourth frequency band. The fourth frequency band is higher than the third frequency band and is for 4G or 5G. At least part of the second frequency band overlaps at least part of the fourth frequency band. 
     In the communication device ( 400 ) according to the fifteenth aspect, the harmonic wave of the third transmission signal of the third transmitting circuit ( 130 ) supporting 4G or 5G can be prevented from jumping to the second transmitting circuit ( 120 ) supporting 2G. 
     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.