JP2011097320A - Transmitter, and detection circuit sharing method therein - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transmitter capable of effectively preventing interference of a transmission system to reduce loss of transmission power with a simple configuration, and to provide a detection circuit sharing method therein. <P>SOLUTION: The transmitter shares a detection circuit (107) between a plurality of transmission circuits (101, 104) with different use frequency bands, and has: a plurality of couplers (103, 106) which input output signals of the plurality of transmission circuits, respectively, and output branching signals to corresponding branch output terminals, respectively; and a plurality of resistors (R1, R2) which are connected between each branch output terminal of the plurality of couplers and an input terminal of the detection circuit to attenuate each branch signal level. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a transmitter having a plurality of transmission systems having different operating frequencies, and more particularly to a method of sharing a detection circuit among a plurality of transmission systems.

  Various circuit configurations have been proposed in which a plurality of transmission systems share a circuit for detecting a transmission wave in a wireless communication device having a plurality of transmission systems with different operating frequencies.

  For example, the AGC circuit disclosed in Patent Document 1 includes a changeover switch that selectively connects one detection circuit that generates a control signal for automatic gain control (AGC) to one of two transmission systems, The connection is switched depending on which of the transmission systems is operating.

  Patent Document 2 discloses a circuit configuration in which each transmission power is demultiplexed and detected by one detection circuit in a multiband mobile communication terminal that switches and controls transmission power in a plurality of frequency bands. (See FIG. 1 of Patent Document 2). Here, the demultiplexing circuit is a circuit that functions as a directional coupler, and a configuration including only a capacitor is described as a specific example (see paragraph 0021 of Patent Document 2). Patent Document 3 discloses a transmitter in which one detection circuit is shared by a plurality of transmission circuits, and a coil is inserted between an RF coupler composed of a capacitor and an input end of the detection circuit (Patent). (Refer FIG. 1 (b) of FIG. 3, FIG. 5).

JP 2006-080810 A Japanese Patent Application No. 2007-158873 International Publication No. WO2008 / 015898 Pamphlet

  However, the provision of the changeover switch as disclosed in Patent Document 1 has the advantage that the two transmission systems can be completely separated, but the changeover switch needs to be controlled separately, which complicates the circuit configuration. There is a demerit.

  On the other hand, Patent Document 2 discloses a configuration in which transmission power is demultiplexed by a directional coupler and connected to a detection circuit, but a specific example of a directional coupler is a circuit including only a capacitor. It ’s just that. However, in a configuration in which a detection circuit is connected to a coupler consisting only of a capacitor, the two transmission systems interfere with each other to generate a frequency characteristic in the detection voltage. If the coupling capacitance is increased to prevent this, transmission power loss (See Comparative Example 1 described later). Further, in the transmitter disclosed in Patent Document 3, the capacitor and the coil form a notch-type resonance circuit, and therefore, a fluctuation in loss depending on the frequency occurs (see Comparative Example 2 described later).

  SUMMARY OF THE INVENTION An object of the present invention is to provide a transmitter and a detection circuit sharing method that can effectively prevent transmission system interference with a simple configuration and can reduce transmission power loss without depending on frequency.

  The transmitter according to the present invention is a transmitter that shares a detection circuit among a plurality of transmission circuits having different operating frequency bands, and each of the output signals of the plurality of transmission circuits is input to a corresponding branch output terminal. A plurality of couplers for outputting branch signals; a plurality of resistors connected between respective branch output terminals of the plurality of couplers and an input terminal of the detection circuit; and attenuating each branch signal level; It is characterized by having.

  A detection circuit sharing method according to the present invention is a detection circuit sharing method in a transmitter that shares a detection circuit among a plurality of transmission circuits that use different frequency bands, and includes a plurality of couplers each having a branch output terminal. A plurality of resistors connected between a branch output terminal of each of the plurality of couplers and an input terminal of the detection circuit; The level of the branch signal is attenuated, respectively.

  According to the present invention, it is possible to effectively prevent interference of a transmission system with a simple configuration, and it is possible to reduce transmission power loss without depending on frequency.

It is a circuit diagram showing an example of a transmitter by a 1st embodiment of the present invention. 2 is a graph showing frequency characteristics of loss from a power amplifier to a detection circuit in the circuit shown in FIG. 1. 3 is a graph showing frequency characteristics of loss from a power amplifier to a detection circuit when a constant deviation of resistance in the circuit shown in FIG. 1 is −5%. 3 is a graph showing frequency characteristics of loss from a power amplifier to a detection circuit when a constant deviation of resistance in the circuit shown in FIG. 1 is + 5%. FIG. 2 is a circuit diagram illustrating an example of a transmitter in which a detection circuit is shared only through a capacitor without a resistor as a first comparative example with the circuit illustrated in FIG. 1. 6 is a graph showing frequency characteristics of loss from the power amplifier to the detection circuit in the comparative example shown in FIG. 5. FIG. 7 is a circuit diagram illustrating an example of a transmitter in which a detection circuit is shared via a capacitor and a coil as a second comparative example with the circuit illustrated in FIG. 1. It is a graph which shows the frequency characteristic of the loss from the power amplifier in the comparative example shown in FIG. 7 to a detection circuit. It is a graph which shows the frequency characteristic of the loss from a power amplifier when a constant deviation of a coil in a circuit shown in Drawing 7 becomes -5%. It is a graph which shows the frequency characteristic of the loss from a power amplifier when a constant deviation of a coil in a circuit shown in Drawing 7 becomes + 5%. It is a circuit diagram which shows an example of the transmitter by 2nd Embodiment of this invention. 12 is a flowchart showing an initial adjustment procedure of a variable resistance value of the circuit shown in FIG. 12 is a flowchart showing a variable resistance control procedure during a transmission operation of the circuit shown in FIG. 12 is a flowchart showing a dynamic range expansion control procedure of the circuit shown in FIG. 12 is a graph for explaining expansion of a dynamic range of the circuit shown in FIG. 11.

  Hereinafter, as an example, a case will be described in which two transmission systems having a use frequency band of 800 MHz and 2 GHz share one detection circuit. The present invention can be similarly applied to a case where a detection circuit is shared by three or more transmission systems.

1. 1. First Embodiment 1.1) Circuit Configuration As shown in FIG. 1, the first transmission system includes a transmission wave generation circuit 101, a power amplifier 102, and a coupler 103, and the second transmission system is a transmission wave generation circuit. 104, a power amplifier 105, and a coupler 106. Here, in accordance with control of a control system (not shown), the two transmission systems perform transmission operations exclusively, and the transmission wave generation circuits 101 and 104 generate transmission waves of different frequency bands at different timings.

  The branch output terminal of the coupler 103 is connected to the input terminal of the detection circuit 107 via the resistor R1, and the branch output terminal of the coupler 106 is connected to the input terminal of the detection circuit 107 via the resistor R2. In the coupler 103, a capacitor C1 as a coupling capacitor is connected between the output line of the power amplifier 102 and the branch output terminal. Similarly, in the coupler 106, a capacitor C2 serving as a coupling capacitor is connected between the output line of the power amplifier 105 and the branch output terminal. The detection output voltage from the detection circuit 107 is output to the calculation unit 108 and used for AGC control and the like.

1.2) Operation The transmission wave generation circuit 101 generates a transmission wave, and the generated transmission wave is amplified by the power amplifier 102 and output as a transmission wave output. The amplified transmission wave is also output to the branch output terminal that is capacitively coupled by the capacitor C1 of the coupler 103, and is input to the detection circuit 107 through the resistor R1. Similarly, the transmission wave generation circuit 104 generates a transmission wave, and the generated transmission wave is amplified by the power amplifier 105 and output as a transmission wave output. The amplified transmission wave is also output to the branch output terminal capacitively coupled by the capacitor C2 of the coupler 106, and is input to the detection circuit 107 through the resistor R2.

  As described above, since the transmission wave generation circuit 101 and the transmission wave generation circuit 104 generate transmission waves exclusively at different timings, transmission waves in two frequency bands are not input to the detection circuit 107 at the same time. Hereinafter, specific characteristics of the present embodiment when the used frequency bands are 800 MHz and 2 GHz will be described.

  The resistance values of the resistors R1 and R2 can be easily adjusted such that the losses from the output terminals of the power amplifiers 102 and 105 to the input terminal of the detection circuit 107 are equal to each other. According to the present embodiment, as shown in FIG. 2, the frequency bands are 800 MHz and 2 GHz, and the attenuation is -28.2 dB.

  According to the present embodiment, the variation in loss is small with respect to the deviation between the resistance values of the resistors R1 and R2. As shown in FIGS. 3 and 4, when the simulation is performed with the constant deviation of the resistance being −5% and when the resistance is + 5%, the loss at 2 GHz is as small as about ± 0.4 dB. It can be seen that the loss variation with respect to the constant deviation of the element can be suppressed sufficiently small.

  In order to increase the detection voltage level, it is necessary to increase the capacitor capacity of the system. However, increasing the resistance value increases the impedance of the coupler, increasing the loss of the transmitted wave output from the coupler. Can be minimized. That is, according to the present embodiment, it is possible to share the detection circuit 107 with the same loss as when a detection circuit is provided separately for each transmission system.

1.3) Comparative Example 1
Since the comparative example 1 shown in FIG. 5 has a circuit configuration in which the resistors R1 and R2 are removed from the circuit shown in FIG. 1, the other circuit elements are denoted by the same reference numerals as those in FIG. Note that the circuit shown in FIG. 5 corresponds to a configuration based on the description of Patent Document 2 described above.

  However, in the circuit configuration of Comparative Example 1, interference occurs between the transmission wave outputs, and the detection sensitivity fluctuation depending on the frequency occurs due to resonance. Therefore, in order to obtain the lowest detection voltage at the same level as the circuit configuration not sharing the detection circuit, the capacitances of the capacitors C1 and C2 are adjusted according to the frequency characteristics, respectively, to increase the level of the high-frequency signal input to the detection circuit 107. However, this attenuates the transmission wave output of the couplers 103 and 106, and in order to compensate for this, the output of the transmission wave generation circuits 101 and 104 is increased and / or the gain of the power amplifiers 102 and 105 is increased. There is a problem that the current consumption of the transmitter increases.

  If the capacitors C1 and C2 of Comparative Example 1 have the same capacitance, the loss from the output of the power amplifiers 102 and 105 to the input of the detection circuit 107 changes as shown in FIG. In this example, a difference of 3 dB occurs in the power level input to the detection circuit 107 at 2 GHz and 800 MHz. Therefore, in order to obtain an equivalent detection voltage, for example, a coupler that extracts a branch output from a transmission wave generation circuit in the 800 MHz band It is necessary to increase the number of capacitors C.

1.4) Comparative Example 2
In Comparative Example 2 shown in FIG. 7, a low-pass filter (LPF) is configured by connecting coils L1 and L2 instead of the resistors R1 and R2 of the circuit shown in FIG. Other circuit elements are denoted by the same reference numerals as in FIG.

  In the circuit configuration of the comparative example 2, since the coil L1, the capacitor C1, the coil L2, and the capacitor C2 form a notch type resonance circuit, loss variation depending on the frequency occurs. FIG. 8 shows the result of simulation with the loss from the power amplifiers 102 and 105 to the detection circuit 107 equal by adjusting the constants of the coils L1 and L2. It can be seen that fluctuations in loss due to resonance occur in the 2 GHz band.

  Since the frequency dependence of the loss due to resonance occurs in this way, the resonance frequency fluctuates due to variations in the coil and capacitor used, the wiring capacity of the printed circuit board, and the like, thereby causing variations in the detection voltage. In order to suppress the variation in the detection voltage, a coil and a capacitor with a narrow deviation are used. However, such a coil and a capacitor are expensive and expensive.

  According to Comparative Example 2, as shown in FIG. 9, when the constant deviation of the coil is -5%, as shown in FIG. 10, when the constant deviation of the coil is + 5%, a loss of 2 GHz is obtained. It is understood that the fluctuation of the loss due to the fluctuation of the resonance frequency due to the constant deviation of the element is large.

1.5) Effect The problems described in the first and second comparative examples, such as frequency-dependent detection voltage fluctuation, loss fluctuation due to resonance, increase in power consumption when avoiding them, and increase in cost, are affected by this embodiment. Eliminate.

  That is, according to the present embodiment, by inserting a resistor between the coupler and the detection circuit, the voltage amplitude after coupling of the coupler is uniformly reduced in all frequency bands. As a result, resonance can be eliminated, and at the same time, the input level of the detection circuit shared by the two transmission systems can be balanced. In order to increase the detection voltage level, it is necessary to increase the capacitance of the capacitor C. However, since the impedance of the coupler increases by increasing the resistance value, the increase in transmission wave output loss from the coupler is minimized. To the limit.

2. Second Embodiment In the first embodiment described above, the case where the resistors R1 and R2 have fixed resistance values has been described. However, the present invention is not limited to this, and the resistors R1 and R2 are variable resistors. By doing so, it is possible to further suppress the loss of the transmission system, and it is possible to further expand the dynamic range of the detection circuit. Details will be described below.

2.1) Circuit Configuration As shown in FIG. 11, the first transmission system includes a transmission wave generation circuit 101, a power amplifier 102, and a coupler 103, and the second transmission system includes a transmission wave generation circuit 104, a power amplifier. 105 and a coupler 106. Here, in accordance with control of a control system (not shown), the two transmission systems perform transmission operations exclusively, and the transmission wave generation circuits 101 and 104 generate transmission waves of different frequency bands at different timings.

  The branch output terminal of the coupler 103 is connected to the input terminal of the detection circuit 107 via the variable resistor R1, and the branch output terminal of the coupler 106 is connected to the input terminal of the detection circuit 107 via the variable resistor R2. Yes. In the coupler 103, a capacitor C1 as a coupling capacitor is connected between the output line of the power amplifier 102 and the branch output terminal. Similarly, in the coupler 106, a capacitor C2 serving as a coupling capacitor is connected between the output line of the power amplifier 105 and the branch output terminal. The detection output voltage Vdet from the detection circuit 107 is output to the control unit 201, and is used for AGC control, for example.

  As will be described later, the control unit 201 inputs the detection output voltage Vdet, the transmission power information TP1 and TP2 from the transmission wave generation circuits 101 and 104, and the adjustment value stored in the adjustment value memory 202, respectively. Signals S1 and S2 are generated to control the resistance values of the variable resistors R1 and R2, respectively. The adjustment value memory 202 is a nonvolatile memory, for example.

  A function equivalent to that of the control unit 201 can also be realized by executing a program stored in a memory on a program control processor such as a central processing unit (CPU).

2.2) Operation The transmission wave generation circuit 101 generates a transmission wave, and the generated transmission wave is amplified by the power amplifier 102 and output as a transmission wave output. The amplified transmission wave is also output to the branch output terminal that is capacitively coupled by the capacitor C1 of the coupler 103, and is input to the detection circuit 107 through the variable resistor R1. Similarly, the transmission wave generation circuit 104 generates a transmission wave, and the generated transmission wave is amplified by the power amplifier 105 and output as a transmission wave output. The amplified transmission wave is also output to a branch output terminal capacitively coupled by the capacitor C2 of the coupler 106, and is input to the detection circuit 107 through the variable resistor R2.

  As described above, since the transmission wave generation circuit 101 and the transmission wave generation circuit 104 generate transmission waves exclusively at different timings, transmission waves in two frequency bands are not input to the detection circuit 107 at the same time. Hereinafter, a specific operation of the present embodiment will be described in detail.

2.3) Initial Adjustment FIG. 12 shows an adjustment algorithm for the variable resistor Ri (i = 1, 2). The variable resistor Ri is preferably adjusted by an inspection adjustment line or the like before product shipment. By performing this adjustment, it is possible to absorb variations in the capacitors C1 and C2, variations in the detection circuit 107, variations in additional capacitance of the substrate, and the like. Hereinafter, the control of the variable resistor R1 on the transmission wave generation circuit 101 side will be described, but the same applies to the variable resistor R2.

  In FIG. 12, the control unit 201 drives the transmission wave generation circuit 101 for adjustment to generate a transmission wave having a predetermined transmission power P0 (step 301). The control unit 201 receives the transmission power information TP1 of the transmission wave generated by the transmission wave generation circuit 101 (step 302), sets the resistance value of the variable resistor R1 to be adjusted to the initial value R0 at the time of adjustment, The resistance value of the variable resistor R2 is set to the maximum value (step 303).

  Subsequently, when the detection output voltage Vdet of the detection circuit 107 for the transmission wave with the transmission power P0 is input, the control unit 201 determines whether or not the detection output voltage Vdet exceeds the detection voltage upper limit value V1 at the time of adjustment ( If Vdet> V1 (step 304: YES), the resistance value of the variable resistor R1 is increased by a predetermined step width dR by the control signal S1 (step 305). The step 305 for increasing the resistance value of the variable resistor R1 is repeated until the detection output voltage Vdet becomes equal to or lower than the detection voltage upper limit value V1.

  When the detection output voltage Vdet becomes equal to or lower than the detection voltage upper limit value V1 (step 304: NO), the control unit determines whether or not the detection output voltage Vdet is lower than the detection voltage lower limit value V2 at the time of adjustment (step 306). If Vdet <V2 (step 306: YES), the resistance value of the variable resistor R1 is lowered by a predetermined step width dR by the control signal S1 (step 307). The step 307 of decreasing the resistance value of the variable resistor R1 is repeated until the detection output voltage Vdet becomes equal to or higher than the detection voltage lower limit value V1.

  When the detection output voltage Vdet falls between the upper limit value V1 and the lower limit value V2 at the time of adjustment (step 306: NO), the control unit 201 uses the value of the control signal S1 at that time as the adjustment value of the transmission wave generation circuit 101. It is stored in the adjustment value memory 202 as S1_adj. Similarly, the adjustment value S2_adj of the transmission wave generation circuit 104 is also stored in the adjustment value memory 202, and the adjustment algorithm is terminated. By previously determining the adjustment value in this way, it is possible to eliminate the operation imbalance caused by the variation in circuit elements.

2.4) Variable resistance control during transmission As described above, the transmission wave generation circuit 101 and the transmission wave generation circuit 104 generate transmission waves exclusively at different timings during transmission operation. Transmission waves are not input to the detection circuit 107 at the same time. Using this exclusive operation, the presence / absence of a transmission wave is determined, and the resistance values of the variable resistors R1 and R2 are controlled by coarseness so that the loss is minimized. Here, it is assumed that the adjustment values S1_adj and S2_adj of the transmission wave generation circuits 101 and 104 are stored in the adjustment value memory 202 by the initial adjustment.

  As shown in FIG. 13, the control unit 201 inputs transmission power information TP1 and TP2 from the transmission wave generation circuits 101 and 104, respectively (step 401). If the transmission power information TP1 is larger than 0 [mW] (step 402: YES), it is determined that the transmission wave generation circuit 101 is generating a transmission wave, the branch output by the coupler 103 is most efficient, and the other The variable resistors R1 and R2 are controlled so as to be input to the detection circuit 107 without being influenced by the transmission system. That is, the corresponding variable resistor R1 is controlled by the control signal S1 of the adjustment value S1_adj stored in the adjustment value memory 202, and the other variable resistor R2 is controlled by the control signal S2 having the maximum resistance value (step 403). ). When the resistance value setting at this timing is completed, the control unit 201 returns to step 401 again and inputs transmission power information TP1 and TP2 from the transmission wave generation circuits 101 and 104, respectively.

  If the transmission power information TP1 is 0 [mW] or less (step 402: NO), it is determined that the transmission wave generation circuit 101 has stopped generating the transmission wave, and then the transmission power information TP2 is 0 [mW]. It is determined whether it is larger (step 404). If the transmission power information TP2 is greater than 0 [mW] (step 404: YES), it is determined that the transmission wave generation circuit 104 is generating a transmission wave, the branch output by the coupler 106 is most efficient, and the other The variable resistors R1 and R2 are controlled so as to be input to the detection circuit 107 without being influenced by the transmission system. That is, the corresponding variable resistor R2 is controlled by the control signal S2 of the adjustment value S2_adj stored in the adjustment value memory 202, and the other variable resistor R1 is controlled by the control signal S1 having the maximum resistance value (step 405). ). When the resistance value setting at this timing is completed, the control unit 201 returns to step 401 again and inputs transmission power information TP1 and TP2 from the transmission wave generation circuits 101 and 104, respectively.

  If both the transmission power information TP1 and TP2 are 0 [mW] or less (step 404: NO), it is determined that no transmission system is transmitting, and the control unit 201 changes the resistance value of the variable resistor. Without returning to step 401, transmission power information TP1 and TP2 are input from the transmission wave generation circuits 101 and 104, respectively.

  As described above, the resistance values of the variable resistors R1 and R2 can be changed between the adjustment value and the maximum resistance value in synchronization with the transmission timing. The loss up to 107 can be reduced to a level equivalent to a circuit configuration in which a detection circuit is provided separately for each transmission system.

2.5) Dynamic Range Expansion Control According to the present embodiment, it is possible to increase the dynamic range of the detection circuit 107 by controlling the variable resistors R1 and R2. Hereinafter, a description will be given with reference to FIGS. 14 and 15.

Here, the high gain detection mode resistance value R _HIGH-G and the low gain detection mode resistance value R _LOW-G of the variable resistors R1 and R2 are determined by the initial adjustment algorithm described in FIG. It is assumed that it is stored in the adjustment value memory 202. Further, it is assumed that the adjustment value memory 202 stores an upper limit value P _H and a lower limit value P _{L of} transmission power for switching the variable resistance value.

In FIG. 14, the control unit 201 inputs transmission power information TPi (assumed to be transmission power Pi here) from the transmission wave generation circuit 101 or 104 (step 501). When the transmission power Pi is smaller than the resistance value switching power lower limit value P _L (step 502: YES), the control unit 201 sets the variable resistor Ri to a predetermined high gain detection mode resistance value R _HIGH-G by the control signal Si. It is recognized that the offset V _offset is added to the detection voltage Vdet that is set and input from the detection circuit 107 (step 503). As long as Pi <P _L , the control unit 201 performs processing based on the detection voltage on the assumption that the offset is added in the high gain detection mode.

When the transmission power Pi is equal to or greater than the resistance value switching power lower limit value P _L (step 502: NO), the control unit 201 further determines the transmission power Pi is whether resistance value larger than the switching power upper limit value P _H (step 504 ). If Pi> P _H (Step 504: YES), the control unit 201 sets a variable resistor Ri to a predetermined low gain detection mode resistance R _LOW-G by the control signal Si (step 505). Be the transmission power Pi is equal to or less than the resistance value switching power upper limit value P _H (Step 504: NO), as long as Pi is equal to or greater than P _L (step 502: NO), the control unit 201 changing the low gain detection mode Continue processing as is. Then, when Pi becomes smaller than P _L (step 502: YES), the variable resistor Ri is switched to the high gain detection mode resistance value R _HIGH-G (step 503).

By controlling the variable resistors R1 and R2 in this way, the detection circuit 107 operates with hysteresis as shown in FIG. 15, and as a result, the dynamic range can be increased. That is, in FIG. 15, operates in the Pi <P _L is long if the high gain detection mode 601, the Pi rises further to reach the P _H switched to the low gain detection mode 602. Conversely, when Pi decreases and reaches P _L , the mode is switched to the high gain detection mode 601.

  As described above, according to the present embodiment, the detection mode is switched depending on the transmission power. Therefore, as shown in FIG. 15, the expanded dynamic range 604 is increased with respect to the dynamic range 603 of the original detection circuit 107. Obtainable.

  Further, the detection mode switching operation depending on the transmission power has hysteresis as shown in FIG. By having this hysteresis, it is possible to effectively prevent the detection mode from being switched due to temporary fluctuations in transmission power and to stabilize the operation. Further, even when the transmission power fluctuates finely, power amplifier loss and output impedance fluctuation can be suppressed.

2.6) Effect As described above, according to the second embodiment, by controlling the variable resistor, it is possible to minimize variation in circuit elements and to expand the dynamic range of the detection circuit. In particular, the loss of the power amplifier and the fluctuation of the output impedance can be suppressed by changing the detection voltage value with respect to the transmission power with hysteresis.

  The present invention is applicable to a transmitter in which a detection circuit is shared by a plurality of transmission circuits.

101, 104 Transmission wave generation circuit 102, 105 Power amplifier 103, 106 Coupler 107 Detection circuit 108 Operation unit 201 Control unit 202 Adjustment value memory R1, R2 Resistor, Variable resistor C1, C2 Capacitor

Claims (14)

A transmitter that shares a detection circuit among a plurality of transmission circuits that use different frequency bands,
A plurality of couplers that respectively input output signals of the plurality of transmission circuits and output branch signals to the corresponding branch output terminals;
A plurality of resistors connected between each branch output terminal of the plurality of couplers and an input terminal of the detection circuit, and attenuating each branch signal level;
A transmitter characterized by comprising:   2. The transmitter according to claim 1, wherein each of the resistance values of the plurality of resistors is set in advance so that a power loss from an output of a corresponding transmission circuit to an input of the detection circuit becomes equal. .   The transmitter according to claim 1, wherein each of the plurality of resistors is a variable resistor.   When the plurality of transmission circuits perform transmission operations exclusively, and one transmission circuit operates and other transmission circuits do not operate, a variable resistor corresponding to the one transmission circuit is set to a predetermined resistance value. 4. The transmitter according to claim 3, further comprising control means for setting each of the variable resistors corresponding to the other transmission circuits to a maximum resistance value.   5. The transmitter according to claim 4, wherein the control unit determines and adjusts the predetermined resistance value in advance so that an output voltage of the detection circuit falls within a predetermined range.   When the transmission power falls below the first switching value, the control means sets the corresponding variable resistor to the high gain detection mode resistance value, and when the transmission power exceeds the second switching value higher than the first switching value. 6. The transmitter according to claim 4, wherein the variable resistor is controlled to be set to a low gain detection mode resistance value.   The transmitter according to claim 6, wherein the control unit gives hysteresis to a switching operation of a resistance value corresponding to transmission power of the variable resistor. A detection circuit sharing method in a transmitter that shares a detection circuit among a plurality of transmission circuits that use different frequency bands,
Output the branch signal from the branch output terminal by inputting the output signals of the plurality of transmission circuits to a plurality of couplers each having a branch output terminal,
A plurality of resistors connected between a branch output terminal of each of the plurality of couplers and an input terminal of the detection circuit respectively attenuate the level of the branch signal;
A method for sharing a detection circuit.   9. The detection circuit according to claim 8, wherein each resistance value of the plurality of resistors is set in advance so that a power loss from an output of a corresponding transmission circuit to an input of the detection circuit becomes equal. Sharing method.   The detection circuit sharing method according to claim 8 or 9, wherein each of the plurality of resistors is a variable resistor.   When the plurality of transmission circuits perform transmission operations exclusively, and one transmission circuit operates and other transmission circuits do not operate, a variable resistor corresponding to the one transmission circuit is set to a predetermined resistance value. 11. The detection circuit sharing method according to claim 10, wherein the variable resistors corresponding to the other transmission circuits are respectively set to a maximum resistance value.   12. The detection circuit sharing method according to claim 11, wherein the predetermined resistance value is determined in advance so that an output voltage of the detection circuit falls within a predetermined range.   When the transmission power falls below the first switching value, the corresponding variable resistor is set to the high gain detection mode resistance value, and when the transmission power exceeds the second switching value higher than the first switching value, the variable resistor The detection circuit sharing method according to claim 11 or 12, wherein the low gain detection mode resistance value is set.   14. The detection circuit sharing method according to claim 13, wherein a hysteresis is given to the switching operation of the resistance value according to the transmission power of the variable resistor.

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