JP2007089052A - Communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a communication system capable of suppressing ACPR deterioration even on adverse terminal use conditions. <P>SOLUTION: At an output side of a power amplifier 10 of a terminal 1, an ACPR detection circuit 14 is provided for detecting ACPR. Furthermore, the ACPR detection circuit 14 is connected to a baseband processing section 11, and the baseband processing section 11 comprises a modulation scheme selection section 12 and a deterioration condition determination section 13. The deterioration condition determination section 13 then determines whether ACPR is deteriorated or not using a detection result of the ACPR detection circuit 14. If the deterioration condition determination section 13 determines the deterioration of ACPR, the modulation scheme selection section 12 changes a modulation scheme of the terminal 1 from 16QAM of high peak rate to QPSK of low peak rate. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a communication system (communication system) that performs communication between a terminal and a base station using signals of a plurality of transmission systems having different peak rates.

  Generally, in mobile radio communication systems such as mobile phone systems and PHS (Personal Handyphone System), such as 16QAM (Quadrature Amplitude Modulation), 8PSK (8 Phase Shift Keying), π / 4 shift QPSK (Quadrature Phase Shift Keying), etc. In some cases, signals of a plurality of modulation schemes having different modulation multi-level numbers are used. In this case, for example, when the position of the terminal is close to the base station and the radio wave condition is good, high-speed data communication is performed using a high-efficiency modulation method such as 16QAM. On the other hand, for example, when the position of the terminal moves away from the base station and the radio wave condition deteriorates, a modulation scheme that is resistant to fading, interference waves, and noise is used, such as 8PSK and π / 4 shift QPSK.

  In addition, regarding a terminal that supports a plurality of modulation schemes, a configuration of a transmission circuit in which a bias voltage (gate voltage) of a power amplifier (PA) is changed according to the modulation scheme is also known (see, for example, Patent Documents 1 and 2). ). In this case, the maximum transmission efficiency can be obtained according to each modulation method.

JP 2001-285385 A JP 2004-356729 A

  By the way, when the transmission method such as the modulation method, the number of multiplexing in CDMA (Code Division Multiple Access), the number of carriers in OFDM (Orthogonal Frequency Division Multiplex), etc. is changed, the average power and the maximum between signals of a plurality of transmission methods are changed. The peak rate, which is the ratio with power, changes. When a signal with a high peak rate is used, the power amplifier of the terminal tends to use a non-linear region (gain saturation region). Therefore, the adjacent channel leakage power ratio (hereinafter referred to as ACPR) is used. ) Tends to deteriorate.

  On the other hand, in the communication system according to the prior art, one transmission method is selected from a plurality of transmission methods according to the radio wave condition. For this reason, even when the terminal usage conditions are poor, such as when the terminal power supply voltage is low or when the terminal temperature is high, the terminal is required to transmit in a transmission method with a high peak rate (for example, 16QAM). There was something to be done. At this time, since the usage condition of the terminal is bad, the linearity between the input power and the output power of the power amplifier of the terminal is deteriorated. As a result, the communication system according to the prior art has a problem that the ACPR deteriorates as the use condition of the terminal deteriorates.

  The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to provide a communication system capable of suppressing deterioration of ACPR even when the use condition of the terminal is bad.

  In order to solve the above-described problem, the invention of claim 1 is directed to transmission method selection means for selecting any one of a plurality of transmission methods having different peak rates, and transmission selected by the transmission method selection means. In a communication system that performs communication between a terminal and a base station using a signal of a scheme, the transmission scheme includes a degradation condition determination unit that determines whether or not a degradation condition that degrades the adjacent channel leakage power rate of the terminal The selecting means is characterized in that, when the deterioration condition determining means determines that the deterioration condition is satisfied, the transmission from the terminal to the base station selects a transmission method having a low peak rate.

  In the invention of claim 2, the terminal or base station is provided with ACPR detection means for detecting an adjacent channel leakage power rate of the terminal, and the deterioration condition determination means is configured to detect the adjacent channel leakage power detected by the ACPR detection means. When the rate is high, the deterioration condition is determined, and when the adjacent channel leakage power rate is low, the deterioration condition is not determined.

  According to a third aspect of the present invention, the deterioration condition determining means determines that the deterioration condition is determined when the temperature of the terminal is high, and determines that the deterioration condition is not determined when the temperature of the terminal is low.

  According to a fourth aspect of the present invention, the deterioration condition determining means determines that the deterioration condition is determined when the power supply voltage of the terminal is low, and determines that the deterioration condition is not satisfied when the power supply voltage of the terminal is high.

  According to a fifth aspect of the present invention, there is provided use request detecting means for detecting whether or not there is a request for use of a transmission method having a high peak rate from the terminal or base station, and the transmission method selecting means is provided from the terminal to the base station. When a transmission request with a low peak rate is selected for transmission, when the use request detecting means detects that there is a use request, the drive voltage of the power amplifier of the terminal is increased to achieve a transmission method with a high peak rate. The configuration is changed.

  According to a sixth aspect of the present invention, there is provided use request detecting means for detecting whether or not there is a request for use of a transmission method having a high peak rate from the terminal or base station, and the transmission method selecting means is provided from the terminal to the base station. When a transmission request with a low peak rate is selected for transmission, when the use request detecting means detects that there is a use request, the terminal is cooled and changed to a transmission method with a high peak rate.

  According to the first aspect of the invention, when the transmission method selection means determines that the deterioration condition is the deterioration condition by the deterioration condition determination means, transmission from the terminal to the base station selects a transmission method with a low peak rate. The deterioration condition determining means can determine a deterioration condition in which the adjacent channel leakage power rate (ACPR) of the terminal deteriorates, and the transmission method selecting means can select a transmission method having a low peak rate when the terminal is in the deterioration condition. It is possible to suppress the deterioration of ACPR.

  According to the invention of claim 2, since the terminal or base station is provided with the ACPR detection means for detecting the adjacent channel leakage power rate of the terminal, the deterioration condition determination means uses the detection result of the ACPR detection means. It can be directly determined whether or not the ACPR has deteriorated.

  According to the invention of claim 3, since the deterioration condition determining means determines whether or not the deterioration condition is in accordance with the temperature of the terminal, the deterioration condition determining means is such that the terminal temperature is high and the linearity of the power amplifier of the terminal is When it gets worse, it can be determined that the deterioration condition is met. On the other hand, when the terminal temperature is low and the linearity of the power amplifier of the terminal is good, the deterioration condition determining means can determine that the deterioration condition is not met. As a result, since the deterioration condition determination means only needs to detect the temperature of the terminal, for example, it is possible to determine the deterioration condition using a simple circuit as compared with the case where ACPR is directly detected.

  According to the invention of claim 4, since the deterioration condition determining means determines whether or not the deterioration condition is in accordance with the power supply voltage of the terminal, the deterioration condition determining means has a low power supply voltage of the terminal and the bias of the power amplifier of the terminal When the voltage decreases, it can be determined that the degradation condition is such that the linearity of the power amplifier deteriorates. On the other hand, when the terminal power supply voltage is high and the bias voltage of the terminal power amplifier is sufficiently high, the deterioration condition determining means can determine that the linearity of the terminal power amplifier is good and not in the deterioration condition. As a result, since the deterioration condition determination means only needs to detect the power supply voltage of the terminal, it is possible to determine the deterioration condition using a simple circuit as compared with the case where ACPR is directly detected, for example.

  According to the invention of claim 5, when the transmission method selection means detects that there is a use request by the use request detection means in a state where a transmission method with a low peak rate is selected for transmission from the terminal to the base station, The configuration is such that the drive voltage of the terminal power amplifier is increased to change to a transmission method with a high peak rate. Thereby, even when the terminal is in a deterioration condition, the linearity of the power amplifier can be compensated by increasing the drive voltage of the power amplifier of the terminal. For this reason, transmission from a terminal to a base station can be performed using a signal of a transmission method with a high peak rate without degrading ACPR.

  According to the invention of claim 6, when the transmission method selection means detects that there is a use request by the use request detection means in a state where a transmission method with a low peak rate is selected for transmission from the terminal to the base station, The terminal is cooled and changed to a transmission method with a high peak rate. Thereby, even when the terminal is in the deterioration condition, the linearity of the power amplifier can be compensated by cooling the terminal. For this reason, transmission from a terminal to a base station can be performed using a signal of a transmission method with a high peak rate without degrading ACPR.

  Hereinafter, as an example of a communication system according to an embodiment of the present invention, a wireless communication system using two modulation schemes of 16QAM having a modulation multilevel number of 16 and π / 4 shift QPSK having a modulation multilevel number of 4 is taken as an example. Detailed description will be given with reference to the accompanying drawings.

  1 to 4 show a first embodiment of the present invention, in which 1 is a terminal such as a mobile phone, and the terminal 1 includes an antenna 2, a transmission circuit 3, a local oscillator 8, The baseband processing unit 11 is configured.

  Reference numeral 2 denotes an antenna that transmits and receives a high-frequency signal RF, and the antenna 2 is connected to a transmission circuit 3 and a reception circuit (not shown) described later. For example, a duplexer or a switch (not shown) is provided between the antenna 2 and the transmission circuit 3 and the reception circuit.

  Reference numeral 3 denotes a transmission circuit that outputs a high-frequency signal RF based on a transmission signal TS composed of, for example, an I signal (in-phase signal) and a Q signal (quadrature signal). The transmission circuit 3 is connected to a local oscillator 8 (described later) and baseband processing. Connected to the unit 11. The transmission circuit 3 includes a quadrature modulator 4, a mixer 7, a power amplifier 10, and the like which will be described later. Then, the transmission circuit 3 orthogonally modulates the transmission signal TS to generate an intermediate frequency signal IF, and upconverts the intermediate frequency signal IF using the oscillation signal LO output from the local oscillator 8 to transmit a high frequency signal for transmission. The signal RF is output.

  Reference numeral 4 denotes a quadrature modulator connected to the output side of the baseband processing unit 11, and the quadrature modulator 4 is constituted by, for example, a mixer, a local oscillator, or the like. Then, the quadrature modulator 4 modulates the transmission signal TS using a local oscillation signal from the local oscillator and outputs an intermediate frequency signal IF. The output side of the quadrature modulator 4 is connected to a mixer 7 via an AGC amplifier 5 (automatic gain control amplifier) and a band pass filter 6. As a result, the intermediate frequency signal IF is removed by using the band pass filter 6 and unnecessary signals are amplified by the AGC amplifier 5 and input to the mixer 7.

  Reference numeral 7 denotes an up-conversion mixer connected to the output side of the band-pass filter 6. The mixer 7 is connected to the local oscillator 8 and uses the local oscillation signal LO from the local oscillator 8 to generate an intermediate frequency signal IF. Is up-converted to a high-frequency signal RF. The output side of the mixer 7 is connected to a power amplifier 10 described later via a band-pass filter 9 that removes unnecessary signals from the high-frequency signal RF.

  Here, the local oscillator 8 is configured by a voltage controlled oscillator (VCO) or the like, and is connected to the baseband processing unit 11. Then, the local oscillator 8 has its oscillation frequency variably set according to the control voltage Vc from the baseband processing unit 11 and outputs a local oscillation signal LO having the oscillation frequency.

  Reference numeral 10 denotes a power amplifier (PA) connected to the output side of the band-pass filter 9. The power amplifier 10 is connected to, for example, a baseband processing unit 11, and the baseband processing unit 11 determines the driving voltage of the power amplifier 10. A bias voltage Vb (base voltage) is set. The power amplifier 10 amplifies the high frequency signal RF and supplies the amplified signal to the antenna 2. As a result, the antenna 2 transmits the power-amplified high-frequency signal RF toward the base station 21.

  The power amplifier 10 always has a gain characteristic as indicated by a solid line in FIG. 3 between the input signal and the output signal. The power amplifier 10 is configured to amplify the power using the linear region in FIG. 3 for both the π / 4 shift QPSK and 16QAM high frequency signals RF. However, when the bias voltage Vb decreases, the temperature of the terminal 1 rises, etc., the gain characteristic of the power amplifier 10 deteriorates and the linear region decreases as shown by the dotted line in FIG. In this case, the π / 4 shift QPSK high-frequency signal RF can be amplified in the linear region, but a part of the 16QAM high-frequency signal RF deviates from the linear region (enters the non-linear region).

  Reference numeral 11 denotes a baseband processing unit, and the baseband processing unit 11 is connected to a transmission circuit 3 and a reception circuit (not shown) as shown in FIG. At the time of transmission, the baseband processing unit 11 outputs, for example, a transmission signal TS modulated by one of two modulation methods of 16QAM and π / 4 shift QPSK using a baseband signal (digital signal). To do. On the other hand, at the time of reception, the baseband processing unit 11 decodes and outputs the baseband signal using the reception signal output from the reception circuit. The baseband processing unit 11 includes a modulation scheme selection unit 12 and a deterioration condition determination unit 13 which will be described later.

  Reference numeral 12 denotes a modulation method selection unit as a modulation method selection means provided in the baseband processing unit 11. The modulation method selection unit 12 is, for example, 16QAM as a modulation method of the high-frequency signal RF in accordance with the received electric field strength Er on the terminal 1 side. Or π / 4 shift QPSK is selected. Also, when the degradation condition determination unit 13 determines that the terminal 1 is in the degradation condition, the modulation scheme selection unit 12 is in a state where 16QAM is selected as the modulation scheme of the high-frequency signal RF transmitted from the terminal 1 to the base station 21. Even if it exists, this modulation system is changed to π / 4 shift QPSK having a low peak rate.

  Reference numeral 13 denotes a deterioration condition determination unit as a deterioration condition determination unit provided in the baseband processing unit 11. The deterioration condition determination unit 13 has an input side connected to an ACPR detection circuit 14 described later. Then, the degradation condition determination unit 13 uses the detection signals S1 and S2 output from the ACPR detection circuit 14 to transmit a desired signal corresponding to the transmission signal TS and to the power amplifier 10 for the sideband signal based on the nonlinear region. The ratio with the transmission output is calculated, and the ACPR is directly detected. Thereby, the deterioration condition determination unit 13 determines whether or not the detected ACPR is larger than a predetermined determination value, and determines whether or not the deterioration condition is that the ACPR of the terminal 1 deteriorates.

  Reference numeral 14 denotes an ACPR detection circuit as an ACPR detection means for detecting the ACPR of the transmission circuit 3. The ACPR detection circuit 14 includes a mixer 15, first and second detection circuits 16, 19 and first, second, which will be described later. The A / D converters 17 and 20 and the band rejection filter 18 are configured.

  Reference numeral 15 denotes a down-conversion mixer connected to the output side of the power amplifier 10 and the local oscillator 8. The mixer 15 uses the same local oscillation signal LO as that for the input (up-conversion) of the mixer 7 to generate power. The high-frequency signal RF output from the amplifier 10 is down-converted. Thereby, the mixer 15 outputs the intermediate frequency signal IF ′ for ACPR detection obtained by restoring the intermediate frequency signal IF (see FIG. 4). The output side of the mixer 15 is connected to the first detection circuit 16 and is also connected to the second detection circuit 19 via the band rejection filter 18.

  Reference numeral 16 denotes a first detection circuit connected to the output side of the mixer 15, and the first detection circuit 16 is composed of, for example, a mixer, a local oscillator, and the like, and the output side thereof is the first A / D converter 17. Is connected to the deterioration condition determination unit 13 of the baseband processing unit 11. Then, the first detection circuit 16 outputs a first detection signal S1 obtained by restoring the transmission signal TS from the intermediate frequency signal IF ′. At this time, the first A / D converter 17 converts the first detection signal S1 into a digital signal and inputs the digital signal to the deterioration condition determination unit 13. Thereby, the degradation condition determination part 13 compares the 1st detection signal S1 with the value previously memorize | stored in the memory | storage part (not shown), for example, The transmission output (transmission of the desired signal (transmission signal TS)) (Electric power).

  Reference numeral 18 denotes a band rejection filter connected to the output side of the mixer 15. The band rejection filter 18 blocks a band corresponding to a desired signal (transmission signal TS) from the ACPR detection intermediate frequency signal IF ′. Pass sidebands. Thereby, the band rejection filter 18 allows only the sideband signal generated by the nonlinearity of the power amplifier 10 to pass therethrough.

  Reference numeral 19 denotes a second detection circuit connected to the output side of the band rejection filter 18, and the second detection circuit 19 is configured in substantially the same manner as the first detection circuit 16, and its output is the second A / A. The degradation condition determination unit 13 of the baseband processing unit 11 is connected via the D converter 20. Then, the second detection circuit 19 outputs a second detection signal S2 obtained by detecting the sideband component of the intermediate frequency signal IF ′. At this time, the second A / D converter 20 converts the second detection signal S2 into a digital signal and inputs the digital signal to the deterioration condition determination unit 13. Thereby, the deterioration condition determination unit 13 compares the second detection signal S2 with a value stored in advance in a storage unit (not shown), for example, to thereby calculate the sideband signal (signal other than the transmission signal TS). Recognized as transmission output (transmission power).

  Reference numeral 21 denotes a base station that is a counterpart to the terminal 1, and the base station 21 selects either 16QAM or π / 4 shift QPSK from the terminal 1 according to the radio wave condition, and selects the selected modulation Communication (transmission and reception) is performed using a high-frequency signal RF according to the method. Specifically, when the received electric field strength Er on the terminal 1 side is strong, high-speed data communication using 16QAM is performed, and when the received electric field strength Er on the terminal 1 side is weak, noise using π / 4 shift QPSK, etc. It is intended to perform low-speed data communication that is strong against damage.

  The communication system according to the present embodiment is configured as described above. Next, modulation method selection processing by this communication system will be described with reference to FIGS.

  First, in step 1, the terminal 1 or the base station 21 detects the received electric field strength Er on the terminal 1 side. Next, in step 2, it is determined whether or not the received electric field strength Er is a strong electric field capable of communication by 16QAM. When it is determined as “NO” in Step 2, since the received electric field strength Er on the terminal 1 side is weak, the process proceeds to Step 3 where the terminal 1 and the base station 21 select π / 4 shift QPSK as the modulation method, Move to step 9 and return. As a result, communication is performed between the terminal 1 and the base station 21 using the high-frequency signal RF modulated by π / 4 shift QPSK.

  On the other hand, if “YES” is determined in step 2, the received electric field strength Er on the terminal 1 side is sufficiently strong, so the process proceeds to step 4 and the terminal 1 and the base station 21 select 16QAM as the modulation method. Thereby, communication between the terminal 1 and the base station 21 is performed using the high-frequency signal RF modulated by 16QAM.

  Next, in step 5, it is determined whether or not the ACPR of the terminal 1 is deteriorated (whether or not it is a deterioration condition) using the deterioration condition determination unit 13. Specifically, the deterioration condition determination unit 13 calculates the ratio between the transmission output of the desired signal and the transmission output of the sideband signal using the first and second detection signals S1 and S2 by the ACPR detection circuit 14, ACPR is detected directly. Then, the deterioration condition determination unit 13 determines whether or not the detected ACPR is larger than a predetermined determination value.

  When it is determined as “NO” in Step 5, the ACPR is smaller than the determination value, so that the ACPR is not deteriorated. For this reason, since the use conditions of the terminal 1 are good, the process proceeds to step 9 while returning with 16QAM being selected as the modulation method.

  On the other hand, when “YES” is determined in Step 5, the ACPR is larger than the determination value, and the ACPR is deteriorated. At this time, the use condition of the terminal 1 deteriorates due to the temperature rise of the terminal 1, the power supply voltage drop (decrease of the bias voltage Vb of the power amplifier 10), etc. Is considered to have deteriorated. Therefore, the process proceeds to step 6, and the terminal 1 (modulation method selection unit 12) notifies the base station 21 that the modulation method of the high-frequency signal RF transmitted from the terminal 1 is changed.

  Next, in step 7, it is confirmed whether or not the base station 21 has permitted the change of the modulation method. If it is determined as “NO” in step 7, the base station 21 does not permit the change of the modulation scheme, and therefore stands by as it is. On the other hand, if “YES” is determined in step 7, the base station 21 permits the modulation scheme to be changed, and thus the process proceeds to step 8 where the modulation scheme selection unit 12 modulates the transmission from the terminal 1 to the base station 21. Change the system to π / 4 shift QPSK. Thereafter, the process proceeds to step 9 and returns.

  The communication system according to the present embodiment selects a modulation method using the above-described processing.

  Thus, in the present embodiment, when the reception electric field strength Er on the terminal 1 side is strong, communication is performed between the terminal 1 and the base station 21 using the high-frequency signal RF modulated by 16QAM. On the other hand, when the reception electric field strength Er on the terminal 1 side is weak, communication is performed between the terminal 1 and the base station 21 using a high-frequency signal RF modulated by π / 4 shift QPSK.

  When 16QAM is selected as the modulation method, the degradation condition determination unit 13 detects the ACPR of the terminal 1 using the detection signals S1 and S2 from the ACPR detection circuit 14 as shown in step 5 in FIG. Then, it is determined whether or not the ACPR has deteriorated. When the degradation condition determination unit 13 determines that the ACPR has deteriorated, the modulation scheme selection unit 12 changes the modulation scheme for transmission from the terminal 1 to the base station 21 to π / 4 shift QPSK. Thus, even when communication is performed between the terminal 1 and the base station 21 using the 16QAM modulation scheme, when the ACPR of the terminal 1 deteriorates due to, for example, heating of the terminal 1 or a decrease in power supply voltage, The terminal 1 can perform transmission using the modulation method (π / 4 shift QPSK) with a low peak rate toward the base station 21.

  Thus, according to the present embodiment, when the deterioration condition determining unit 13 determines that the use condition of the terminal 1 is deteriorated, the modulation scheme selecting unit 12 transmits the peak rate from the terminal 1 to the base station 21. Π / 4 shift QPSK is selected as the low modulation method. For this reason, the deterioration condition determination unit 13 can be used to determine a deterioration condition in which the ACPR of the terminal 1 deteriorates, and the modulation scheme selection unit 12 uses the determination result of the deterioration condition determination unit 13 to determine whether the terminal 1 When the deterioration condition is satisfied, π / 4 shift QPSK having a low peak rate can be selected. That is, even when the linearity of the power amplifier 10 deteriorates due to, for example, heating of the terminal 1 or a decrease in power supply voltage, the terminal 1 uses the π / 4 shift QPSK with a low peak rate to transmit a high-frequency signal for transmission. Modulate RF. Thus, even when the nonlinear region (saturation region) between the input power and the output power of the power amplifier 10 increases, the possibility of using the nonlinear region when amplifying the high-frequency signal RF can be reduced. Deterioration can be suppressed.

  As a result, it is not necessary to increase the bias voltage Vb in advance considering the deterioration condition of the terminal 1 or to use the power amplifier 10 having excellent linearity, so that the power consumption and manufacturing cost of the terminal 1 can be reduced.

  Further, since the terminal 1 is provided with the ACPR detection circuit 14 for detecting ACPR, the deterioration condition determination unit 13 directly determines whether or not the ACPR of the terminal 1 has deteriorated using the detection result of the ACPR detection circuit 14. Can be determined. For this reason, the degradation condition determination unit 13 can accurately and quickly detect the degradation of the ACPR of the terminal 1, so that when the ACPR of the terminal 1 is degraded, the transmission from the terminal 1 is quickly changed to a modulation method with a low peak rate. Can do.

  Next, FIG. 5 shows a second embodiment according to the present invention. The feature of this embodiment is that the deterioration condition determination unit determines that the deterioration condition is present when the terminal temperature is high, and the terminal temperature is low. In some cases, it is determined that the deterioration condition is not satisfied. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  Reference numeral 31 denotes a deterioration condition determination unit as a deterioration condition determination unit according to the present embodiment. The deterioration condition determination unit 31 is connected to a temperature detector 32 that detects the temperature T of the terminal 1. At this time, the temperature detector 32 detects, for example, the temperature near the power amplifier 10 or the temperature near the drive circuit of the power amplifier 10. Then, the deterioration condition determination unit 31 uses, for example, the temperature T of the terminal 1 as the determination value T0 (threshold value) for determining whether or not the terminal 1 is in the deterioration condition, and the linearity of the power amplifier 10 deteriorates. The temperature at which the ACPR falls below the desired value is stored in advance. Therefore, the deterioration condition determination unit 31 compares the detection value Ts of the temperature T of the terminal 1 with the determination value T0, and determines that the terminal 1 is in the deterioration condition when the detection value Ts is higher than the determination value T0. When the detection value Ts is equal to or less than the determination value T0, it is determined that the terminal 1 is not in the deterioration condition.

  As a result, when the temperature T of the terminal 1 is high, the deterioration condition determination unit 31 can determine that the deterioration condition is such that the linearity of the power amplifier 10 is deteriorated. On the other hand, when the temperature T of the terminal 1 is low, the deterioration condition determination unit 31 can determine that the linearity of the power amplifier 10 of the terminal 1 is good and is not in the deterioration condition. As a result, since the deterioration condition determination unit 31 can determine the deterioration condition of the terminal 1 based on the increase in the temperature T of the terminal 1, the modulation scheme selection unit 12 determines the terminal based on the determination result of the deterioration condition determination unit 31. Either one of 16 QAM and π / 4 shift QPSK can be selected as one modulation method.

  Thus, also in this embodiment, it is possible to obtain substantially the same operational effects as those in the first embodiment. In particular, in the present embodiment, the deterioration condition determination unit 31 only needs to detect the temperature T of the terminal 1, so that it is determined whether or not the deterioration condition is satisfied using a simple circuit as compared with, for example, the case where ACPR is directly detected. can do.

  Next, FIG. 6 shows a third embodiment according to the present invention. The feature of this embodiment is that the deterioration condition determination unit determines that the deterioration condition is a terminal power supply voltage when the terminal power supply voltage is low. When the value is high, it is determined that the deterioration condition is not satisfied. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  Reference numeral 41 denotes a deterioration condition determination unit as a deterioration condition determination unit according to the present embodiment. The deterioration condition determination unit 41 is connected to a voltage detector 42 that detects the power supply voltage V0 of the terminal 1. Then, the deterioration condition determination unit 41 reduces, for example, the bias voltage Vb of the power amplifier 10 corresponding to the power supply voltage V0 as the determination value Vt (threshold value) for determining whether or not the terminal 1 is in the deterioration condition. The value of the power supply voltage V0 when the ACPR falls below a desired value is stored in advance. For this reason, the deterioration condition determination unit 41 compares the detection value Vs of the power supply voltage V0 by the voltage detector 42 with the determination value Vt. When the detection value Vs is lower than the determination value Vt, the terminal 1 is in the deterioration condition. When the detection value Vs is greater than or equal to the determination value Vt, it is determined that the terminal 1 is not in the deterioration condition.

  Thereby, the degradation condition determination unit 41 determines that the degradation condition that the linearity of the power amplifier 10 is deteriorated when the power supply voltage V0 of the terminal 1 is low and the bias voltage Vb of the power amplifier 10 of the terminal 1 is decreased. can do. On the other hand, when the power supply voltage V0 of the terminal 1 is high and the bias voltage Vb of the power amplifier 10 of the terminal 1 is sufficiently high, the deterioration condition determination unit 41 has good linearity of the power amplifier 10 of the terminal 1 and is not in the deterioration condition. Can be determined. As a result, since the deterioration condition determination unit 41 can determine the deterioration condition of the terminal 1 based on the decrease in the power supply voltage V0 of the terminal 1, the modulation scheme selection unit 12 is based on the determination result of the deterioration condition determination unit 41. Either 16QAM or π / 4 shift QPSK can be selected as the modulation scheme of the terminal 1.

  Thus, also in this embodiment, it is possible to obtain substantially the same operational effects as those in the first embodiment. In particular, in the present embodiment, the deterioration condition determination unit 41 only needs to detect the power supply voltage V0 of the terminal 1, and therefore, for example, compared with the case of directly detecting ACPR, whether or not the deterioration condition is satisfied using a simple circuit. Can be determined.

  Next, FIG. 7 and FIG. 8 show a fourth embodiment according to the present invention. The feature of this embodiment is that it detects whether or not there is a request for using a modulation method with a high peak rate from a base station. In addition to including a request detection unit, when the use request detection unit detects a use request, the modulation method selection unit is configured to increase the bias voltage of the power amplifier of the terminal and perform transmission using a modulation method with a high peak rate. There is. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  Reference numeral 51 denotes a use request detection unit provided as a use request detection unit provided in the baseband processing unit 11. The use request detection unit 51 is connected to, for example, a receiving circuit (not shown), and the ACPR of the terminal 1 deteriorates. Under the condition, it is detected based on the signal from the base station 21 whether or not the transmission from the base station 21 is requested by 16QAM.

  Specifically, a case is considered where the received electric field strength Er on the terminal 1 side is strong, and communication between the terminal 1 and the base station 21 is performed by 16QAM. In this case, if the ACPR of the terminal 1 deteriorates, the terminal 1 requests the base station 21 to change to π / 4 shift QPSK. On the other hand, when the base station 21 does not permit the change of the modulation scheme and requests transmission by 16QAM having a high peak rate, the use request detection unit 51 detects that the transmission by the base station 21 is requested by 16QAM. To do.

  Reference numeral 52 denotes a modulation scheme selection unit as a transmission scheme selection unit according to the present embodiment. The modulation scheme selection unit 52 is substantially the same as the modulation scheme selection unit 12 according to the first embodiment. When the deterioration condition is determined, the transmission of the terminal 1 selects π / 4 shift QPSK. When the deterioration condition determination unit 13 determines that the deterioration condition is not the deterioration condition, the transmission of the terminal 1 selects 16 QAM.

  Even when the degradation condition determination unit 13 determines that the degradation condition is present, when the use request detection unit 51 detects a 16QAM transmission request, the modulation scheme selection unit 52 increases the bias voltage Vb. As a result, the linear region of the power amplifier 10 increases (see the two-dot chain line in FIG. 3), so that the terminal 1 performs 16QAM transmission without deteriorating the ACPR.

  The communication system according to the present embodiment uses the terminal 1 as described above. Next, modulation method selection processing by the communication system will be described with reference to FIGS.

  The communication system according to the present embodiment also performs the processing from step 1 to step 9 in substantially the same manner as the communication system according to the first embodiment, and the terminal 1 and the base station 21 according to the received electric field strength Er on the terminal 1 side. Select the modulation method between Even when 16QAM communication is performed between the terminal 1 and the base station 21, if the ACPR of the terminal 1 deteriorates, the modulation scheme of the terminal 1 is changed to π / 4 shift QPSK.

  However, in the present embodiment, the processing when it is determined “NO” in step 7 is first different from the embodiment. That is, in step 7, it is confirmed whether or not the base station 21 permits the change of the modulation method to π / 4 shift QPSK. If it is determined as “NO” in step 7, the base station 21 does not permit the modulation scheme to be changed. At this time, the use request detection unit 51 recognizes that the base station 21 has requested transmission by 16QAM. For this reason, since the use request detection unit 51 detects a 16QAM transmission request, the process proceeds to step 11 where the modulation scheme selection unit 52 boosts the bias voltage Vb of the power amplifier 10. Thereby, although power consumption increases and the communication possible time of the terminal 1 is shortened, the linearity of the power amplifier 10 is improved. For this reason, the terminal 1 performs 16QAM transmission in a state in which the degradation of ACPR is compensated. Thereafter, the process proceeds to step 9 and returns.

  On the other hand, when it is determined as “YES” in Step 7, the base station 21 permits the change of the modulation method to the π / 4 shift QPSK. For this reason, the use request detection unit 51 recognizes that there is no transmission request by 16QAM from the base station 21. Therefore, in step 8, the modulation scheme selection unit 52 changes the modulation scheme of transmission from the terminal 1 to the base station 21 to π / 4 shift QPSK, moves to step 9 and returns.

  Thus, also in this embodiment, it is possible to obtain substantially the same operational effects as those in the first embodiment. In particular, in the present embodiment, even when the terminal 1 performs transmission by π / 4 shift QPSK due to degradation of ACPR, when the use request detection unit 51 detects a transmission request by 16QAM from the base station 21, the terminal 1 The bias voltage Vb of the power amplifier 10 is increased, and the modulation scheme of the terminal 1 is changed to 16QAM having a high peak rate. Thereby, even when the terminal 1 is in the deterioration condition, the linearity of the power amplifier 10 can be compensated by increasing the bias voltage Vb of the power amplifier 10 of the terminal 1. Therefore, transmission from the terminal 1 to the base station 21 can be performed using 16QAM having a high peak rate without deteriorating ACPR.

  In the fourth embodiment, when the usage request is detected by the usage request detector 51, the modulation scheme selector 52 increases the bias voltage Vb of the power amplifier 10 of the terminal 1 to increase the 16QAM with a high peak rate. It is set as the structure which transmits by.

  However, the present invention is not limited to this. For example, when the use request detection unit 51 detects a use request, the modulation method selection unit 52 cools the terminal 1 by using, for example, a cooling fan, a cooling element, etc. It is good also as a structure which transmits by high 16QAM.

  Even in this case, the linearity of the power amplifier 10 can be compensated by cooling the terminal 1 including the power amplifier 10 and its drive circuit. Therefore, transmission from the terminal 1 to the base station 21 can be performed using 16QAM having a high peak rate without deteriorating ACPR.

  Next, FIGS. 9 to 11 show a fifth embodiment according to the present invention. The feature of this embodiment is that a use request for detecting whether there is a use request for a modulation method having a high peak rate from a terminal. In addition to including a detection unit, the modulation scheme selection unit is configured to increase the bias voltage of the power amplifier of the terminal and transmit with a modulation scheme with a high peak rate when the usage request is detected by the usage request detection unit is there. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  61 is a use request detecting unit provided as a use request detecting means provided in the baseband processing unit 11. The use request detecting unit 61 is based on 16QAM from the terminal 1 in a state where the ACPR of the terminal 1 is in a deterioration condition. Detects whether transmission is requested.

  Specifically, first, consider a case where the ACPR of the terminal 1 deteriorates and the terminal 1 transmits to the base station 21 using π / 4 shift QPSK. In this case, for example, when the transmission data amount of the terminal 1 increases and exceeds a predetermined amount, the use request detection unit 61 detects that the terminal 1 has requested transmission by 16QAM.

  Reference numeral 62 denotes a modulation scheme selection unit as a transmission scheme selection unit according to the present embodiment. The modulation scheme selection unit 62 is substantially the same as the modulation scheme selection unit 12 according to the first embodiment. When the deterioration condition is determined, the transmission of the terminal 1 selects π / 4 shift QPSK. When the deterioration condition determination unit 13 determines that the deterioration condition is not the deterioration condition, the transmission of the terminal 1 selects 16 QAM.

  Even when the degradation condition determination unit 13 determines that the degradation condition is present, when the use request detection unit 61 detects a 16QAM transmission request, the modulation scheme selection unit 62 increases the bias voltage Vb to increase the bias voltage Vb. It is configured to perform transmission.

  The communication system according to the present embodiment uses the terminal 1 as described above. Next, modulation method selection processing by the communication system will be described with reference to FIGS.

  The communication system according to the present embodiment also performs the processing from step 1 to step 9 in substantially the same manner as the communication system according to the first embodiment, and the terminal 1 and the base station 21 according to the received electric field strength Er on the terminal 1 side. Select the modulation method between Even when 16QAM communication is performed between the terminal 1 and the base station 21, if the ACPR of the terminal 1 deteriorates, the modulation scheme of the terminal 1 is changed to π / 4 shift QPSK.

  However, in the present embodiment, after changing the modulation scheme of terminal 1 to π / 4 shift QPSK in step 8, the following steps 21 to 25 are performed to respond to a 16QAM transmission request from terminal 1. Thus, the first embodiment is different from the first embodiment in that the modulation scheme of the terminal 1 is changed to 16QAM.

  That is, in step 21 after step 8, the use request detection unit 61 determines whether or not the amount of transmission data transmitted from the terminal 1 to the base station 21 is greater than a predetermined amount. When the transmission data amount is equal to or smaller than the predetermined amount, it is determined as “NO” in step 21, and the use request detection unit 61 recognizes that there is no use request of 16QAM by the terminal 1. For this reason, the modulation scheme selection unit 62 maintains the state where π / 4 shift QPSK is selected as the modulation scheme of the terminal 1, and returns at step 9.

  On the other hand, when it is determined “YES” in step 21, the transmission data amount of the terminal 1 is larger than the predetermined amount. At this time, the use request detector 61 recognizes that the terminal 1 has requested transmission by 16QAM. Therefore, the process proceeds to step 22, and the terminal 1 (modulation method selection unit 62) notifies the base station 21 that the modulation method of the high-frequency signal RF transmitted from the terminal 1 is changed.

  Next, in step 23, it is confirmed whether the base station 21 has permitted the change of the modulation method. When it is determined as “NO” in step 23, the base station 21 does not permit the change of the modulation scheme, and therefore stands by as it is. On the other hand, if “YES” is determined in step 23, the base station 21 permits the modulation scheme to be changed, and thus the process proceeds to step 24 where the modulation scheme selection unit 62 boosts the bias voltage Vb of the power amplifier 10. Thereby, although power consumption increases and the communication possible time of the terminal 1 is shortened, the linearity of the power amplifier 10 is improved.

  After that, in step 25, the modulation scheme selection unit 62 changes the modulation scheme of transmission from the terminal 1 to the base station 21 to 16QAM, moves to step 9 and returns. Thereby, the terminal 1 can perform transmission by 16QAM in a state in which deterioration of ACPR is compensated.

  Thus, also in this embodiment, it is possible to obtain substantially the same operational effects as those in the first embodiment. In particular, in the present embodiment, even when the terminal 1 performs transmission by π / 4 shift QPSK due to ACPR degradation, when the use request detection unit 61 detects a transmission request by 16QAM from the terminal 1, the power of the terminal 1 The bias voltage Vb of the amplifier 10 is increased, and the modulation scheme of the terminal 1 is changed to 16QAM having a high peak rate. Thereby, even when the terminal 1 is in the deterioration condition, the linearity of the power amplifier 10 can be compensated by increasing the bias voltage Vb of the power amplifier 10 of the terminal 1. Therefore, transmission from the terminal 1 to the base station 21 can be performed using 16QAM having a high peak rate without deteriorating ACPR.

  In the fifth embodiment, when the use request detecting unit 61 detects that there is a use request, the modulation scheme selecting unit 62 increases the bias voltage Vb of the power amplifier 10 of the terminal 1 to increase the peak rate. A high 16QAM transmission is used. However, the present invention is not limited to this. For example, when the use request detection unit 61 detects that there is a use request, the modulation method selection unit 62 cools the terminal 1 by using, for example, a cooling fan, a cooling element, etc. It is good also as a structure which transmits by 16QAM with a high rate.

  Next, FIGS. 12 and 13 show a sixth embodiment according to the present invention. The feature of this embodiment is that an ACPR detection circuit for detecting the ACPR of a terminal is provided in the base station. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  Reference numeral 71 denotes a base station according to this embodiment, and the base station 71 includes an antenna 72, a receiving circuit 73, a local oscillator 76, a baseband processing unit 82, and the like, which will be described later.

  Reference numeral 72 denotes an antenna that transmits and receives a high-frequency signal RF, and the antenna 72 is connected to a receiving circuit 73 and a transmitting circuit (not shown) described later. Between the antenna 72, the receiving circuit 73, and the transmitting circuit, for example, a duplexer or a switcher (not shown) is provided.

  Reference numeral 73 denotes a transmission circuit that outputs a reception signal RS made up of, for example, an I signal and a Q signal based on the high-frequency signal RF received from the antenna 72. It is connected. The receiving circuit 73 includes a mixer 75, a quadrature detector 79, and the like which will be described later. Then, the reception circuit 73 down-converts the high frequency signal RF into the intermediate frequency signal IF using the oscillation signal LO output from the local oscillator 76, and outputs the reception signal RS by orthogonally detecting the intermediate frequency signal IF. Is.

  75 is a down-conversion mixer connected to the antenna 72 via the low-noise amplifier 74. The mixer 75 is connected to the local oscillator 76, and uses the local oscillation signal LO from the local oscillator 76 to generate a high-frequency signal. RF is down-converted to an intermediate frequency signal IF. The output side of the mixer 75 is connected to a quadrature detector 79 via a band pass filter 77 that removes unnecessary signals such as sidebands from the intermediate frequency signal IF and an AGC amplifier 78.

  Reference numeral 79 denotes a quadrature detector connected to the output side of the AGC amplifier 78. The quadrature detector 79 is composed of, for example, a mixer, a local oscillator, or the like. Then, the quadrature detector 79 demodulates the received signal RS composed of the I signal and the Q signal from the intermediate frequency signal IF using the local oscillation signal from the local oscillator. The output side of the quadrature detector 79 is connected to a baseband processing unit 82 to be described later via a band pass filter 80 and an amplifier 81 having a constant gain.

  Reference numeral 82 denotes a baseband processing unit connected to the receiving circuit 73, and the baseband processing unit 82 is connected to the receiving circuit 73 and a transmitting circuit (not shown). At the time of reception, the baseband processing unit 82 decodes and outputs the baseband signal using the reception signal RS output from the reception circuit 73. On the other hand, at the time of transmission, the baseband processing unit 82 outputs the transmission signal TS to the transmission circuit using, for example, a baseband signal. At this time, the transmission circuit transmits a high-frequency signal RF based on the transmission signal TS from the antenna 72. The baseband processing unit 82 includes a modulation scheme selection unit 83 and a deterioration condition determination unit 84 which will be described later.

  Reference numeral 83 denotes a modulation scheme selection section as a modulation scheme selection means provided in the baseband processing section 82. The modulation scheme selection section 83 is substantially similar to the modulation scheme selection section 12 according to the first embodiment, for example, the terminal 1 One of 16QAM and π / 4 shift QPSK is selected as the modulation method of the high-frequency signal RF in accordance with the reception electric field strength Er on the side. In addition, when the degradation condition determination unit 84 determines that the terminal 1 is in the degradation condition, the modulation scheme selection unit 83 is in a state where 16QAM is selected as the modulation scheme of the high-frequency signal RF transmitted from the terminal 1 to the base station 71. Even if it exists, this modulation system is changed to π / 4 shift QPSK having a low peak rate.

  Reference numeral 84 denotes a deterioration condition determination unit as a deterioration condition determination unit provided in the baseband processing unit 82. The deterioration condition determination unit 84 is connected to an ACPR detection circuit 85 to be described later on the input side. Then, the deterioration condition determination unit 84 uses the output signal S3 output from the ACPR detection circuit 85 to determine whether or not the deterioration condition is such that the ACPR of the terminal 1 deteriorates.

  Reference numeral 85 denotes an ACPR detection circuit serving as an ACPR detection means for detecting the ACPR of the terminal 1. The ACPR detection circuit 85 includes first and second detection circuits 86 and 88, a band rejection filter 87, an operational amplifier 89, and A, which will be described later. / D converter 90 is comprised.

  Reference numeral 86 denotes a first detection circuit connected to the output side of the band-pass filter 77. The first detection circuit 86 is constituted by, for example, a mixer, a local oscillator, or the like. Then, the first detection circuit 86 outputs the first detection signal S1 similar to the reception signal RS from the intermediate frequency signal IF from which unnecessary signals are removed.

  Reference numeral 87 denotes a band rejection filter connected to the output side of the mixer 75. The band rejection filter 87 blocks a band corresponding to a desired reception signal RS in the intermediate frequency signal IF and passes the sideband. As a result, the band rejection filter 87 passes only the sideband signal generated by the nonlinearity of the power amplifier 10 on the terminal 1 side.

  Reference numeral 88 denotes a second detection circuit connected to the output side of the band rejection filter 87, and the second detection circuit 88 is configured in substantially the same manner as the first detection circuit 86. The second detection circuit 88 outputs a second detection signal S2 obtained by detecting the sideband component of the intermediate frequency signal IF.

  Reference numeral 89 denotes an operational amplifier that outputs a signal corresponding to the voltage difference between the first and second detection signals S1 and S2. The operational amplifier 89 has an input side on the output side of the first and second detection circuits 86 and 88. And the output side is connected to the deterioration condition determination unit 84 of the baseband processing unit 82 via the A / D converter 90. Therefore, the A / D converter 90 inputs an output signal S3 composed of a digital signal corresponding to the voltage difference between the detection signals S1 and S2 to the deterioration condition determination unit 84.

  Here, as the ACPR deteriorates, the sideband component of the intermediate frequency signal IF increases, and the voltage difference between the detection signals S1 and S2 decreases. For this reason, the deterioration condition determination unit 84 compares the limit value (limit voltage) stored in advance in the storage unit (not shown) with the output signal S3, and when the output signal S3 is smaller than the limit value, the terminal It is determined that the ACPR of 1 has deteriorated. On the other hand, the deterioration condition determination unit 84 determines that the ACPR of the terminal 1 has not deteriorated when the output signal S3 is equal to or greater than the limit value.

  The communication system according to the present embodiment uses the base station 71 as described above. Next, modulation method selection processing by this communication system will be described with reference to FIGS.

  First, in step 31, the terminal 1 or the base station 71 detects the received electric field strength Er on the terminal 1 side. Next, in step 32, it is determined whether or not the received electric field strength Er is a strong electric field capable of communication by 16QAM. When it is determined “NO” in step 32, the received electric field strength Er on the terminal 1 side is weak, so the process proceeds to step 33, where the terminal 1 and the base station 71 select π / 4 shift QPSK as the modulation method, Move to step 39 and return. Thereby, communication is performed between the terminal 1 and the base station 71 using the high-frequency signal RF modulated by π / 4 shift QPSK.

  On the other hand, if “YES” is determined in step 32, the received electric field strength Er on the terminal 1 side is sufficiently strong, so the process proceeds to step 34, and the terminal 1 and the base station 71 select 16QAM as the modulation method. Thereby, communication is performed between the terminal 1 and the base station 71 using the high-frequency signal RF modulated by 16QAM.

  Next, in step 35, the ACPR of the terminal 1 is detected using the ACPR detection circuit 85 of the base station 71. In step 36, it is determined whether or not the ACPR of the terminal 1 has deteriorated (whether or not it is a deterioration condition) using the deterioration condition determination unit 84 of the base station 71. Specifically, the deterioration condition determination unit 13 determines whether or not the output signal S3 corresponding to the ACPR output from the ACPR detection circuit 85 is smaller than the limit value.

  When it is determined "NO" in step 36, the ACPR is not deteriorated because the output signal S3 is not less than the limit value. For this reason, since the use conditions of the terminal 1 are good, the routine proceeds to step 39 while returning the state where 16QAM is selected as the modulation method.

  On the other hand, when “YES” is determined in step 36, the output signal S3 is smaller than the limit value, and the ACPR is deteriorated. At this time, the use condition of the terminal 1 is deteriorated due to a temperature rise of the terminal 1, a power supply voltage drop (decrease in the bias voltage Vb of the power amplifier 10), etc., and the power amplifier 10 has a linearity between the input power and the output power. Is considered to have deteriorated. For this reason, moving to step 37, the base station 71 notifies the terminal 1 that the modulation method of the high-frequency signal RF of the terminal 1 should be changed.

  Thereby, in step 38, the terminal 1 changes the modulation scheme of transmission to the base station 71 to π / 4 shift QPSK. Thereafter, the process proceeds to step 39 and returns.

  Thus, also in this embodiment, it is possible to obtain substantially the same operational effects as those in the first embodiment. In particular, in the present embodiment, since the ACPR detection circuit 85 for detecting the ACPR of the terminal 1 is provided in the base station 71, it is not necessary to provide a circuit for detecting the ACPR on the terminal 1 side. For this reason, the terminal 1 can be reduced in size and weight, and the power consumption of the terminal 1 can be reduced.

  Next, FIG. 14 shows a seventh embodiment according to the present invention. The feature of this embodiment is that the deterioration condition determining means is configured by using a comparator. In the present embodiment, the same components as those in the sixth embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  Reference numeral 91 denotes an ACPR detection circuit as an ACPR detection means according to the present embodiment. The ACPR detection circuit 91 includes first and second detection circuits 86 and 88, a band rejection filter 87, and an operational amplifier according to the sixth embodiment. First and second detection circuits 92 and 94, a band rejection filter 93, and an operational amplifier 95 that are substantially the same as those of 89 are provided. The input side of the first detection circuit 92 is connected to the output side of the band pass filter 77 via an attenuator 96. On the other hand, the input side of the second detection circuit 94 is connected to the output side of the mixer 75 via the band rejection filter 93. Further, the output sides of the first and second detection circuits 92 and 94 are connected to an operational amplifier 95.

  Here, the attenuator 96 is connected to the first and second detection circuits 92 and 94 by the first and second detection circuits 92 and 94 when the ACPR of the end-to-end 1 becomes a standard value that is an allowable limit (for example, standard ACPR value). The amount of attenuation is set so that the detection signals S1 and S2 have substantially the same value.

  On the other hand, the operational amplifier 95 subtracts the first detection signal S1 from the second detection signal S2. For this reason, when the ACPR satisfies the standard value, the first detection signal S1 is larger than the second detection signal S2, so that the output of the operational amplifier 95 corresponds to the threshold voltage of the comparator 97 described later. It becomes below a predetermined voltage value. On the other hand, when the ACPR does not satisfy the standard value, the first detection signal S1 is smaller than the second detection signal S2, so that the output of the operational amplifier 95 is larger than a predetermined voltage value.

  A comparator 97 is connected to the output side of the operational amplifier 95 as a deterioration condition determining means. The output side of the comparator 97 is connected to the modulation method selection unit 83 of the baseband processing unit 82. For example, when the output of the operational amplifier 95 is equal to or lower than a predetermined voltage value, the comparator 97 outputs a determination signal S4 of the GND potential as an OFF signal, and when the output of the operational amplifier 95 is larger than the predetermined voltage value. The determination signal S4 having a constant voltage such as 5V is output as the ON signal. Thereby, the modulation method selection unit 83 can select the modulation method according to whether the determination signal S4 of the comparator 97 is an ON signal or an OFF signal.

  Thus, also in this embodiment, it is possible to obtain substantially the same operational effects as those in the first and sixth embodiments. In particular, in this embodiment, since the deterioration condition determining means is configured using the comparator 97, the A / D converter can be omitted. For this reason, the configuration of the ACPR detection circuit 91 can be simplified, and the manufacturing cost can be reduced.

  In the sixth and seventh embodiments, the use request of 16QAM by the terminal 1 or the base station 71 is not considered. However, the present invention is not limited to this, and the configurations according to the fourth and fifth embodiments may be applied to the communication systems according to the sixth and seventh embodiments. As a result, the modulation scheme of terminal 1 can be changed in response to a request for use of 16QAM by terminal 1 or base station 71.

  In the fourth and fifth embodiments, the deterioration condition determination unit 13 uses the ACPR detection circuit 14 to determine whether or not ACPR has deteriorated. However, the present invention is not limited to this, and as in the second and third embodiments, the deterioration condition determination unit determines whether the ACPR is deteriorated using a temperature detector or a voltage detector. It is good.

  In each of the above embodiments, π / 4 shift QPSK and 16QAM are used as two transmission systems having different peak rates. However, the present invention is not limited to this, and 8PSK, 32QAM, 128QAM, or the like may be used as a transmission method.

  Further, in each of the above embodiments, two modulation schemes (π / 4 shift QPSK, 16QAM) are used as two transmission schemes having different peak rates. However, the present invention is not limited to this, and for example, a configuration in which the number of multiplexing in CDMA is changed as two transmission schemes or a number of carriers in OFDM may be changed.

It is a block diagram which shows the terminal and base station by 1st Embodiment. 2 is a flowchart showing a modulation scheme selection process by a terminal and a base station in FIG. 1. FIG. 2 is a characteristic diagram showing a relationship between input signal strength and output signal strength of the power amplifier in FIG. 1. FIG. 2 is a characteristic diagram showing a relationship between the frequency of an intermediate frequency signal output from a mixer of the ACPR detection circuit in FIG. 1 and signal intensity. It is a block diagram which shows the terminal and base station by 2nd Embodiment. It is a block diagram which shows the terminal and base station by 3rd Embodiment. It is a block diagram which shows the terminal and base station by 4th Embodiment. It is a flowchart which shows the selection process of the modulation system by the terminal and base station in FIG. It is a block diagram which shows the terminal and base station by 5th Embodiment. 10 is a flowchart showing a modulation scheme selection process by a terminal and a base station in FIG. 9. It is a flowchart following FIG. It is a block diagram which shows the terminal and base station by 6th Embodiment. 13 is a flowchart showing modulation scheme selection processing by a terminal and a base station in FIG. 12. It is a block diagram which shows the terminal and base station by 7th Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Terminal 3 Transmitter circuit 7 Mixer 8 Local oscillator 10 Power amplifier 11, 82 Baseband process part 12, 52, 62, 83 Modulation system selection part (transmission system selection means)
13, 31, 41, 84 Deterioration condition determination unit (deterioration condition determination means)
14, 85, 91 ACPR detection circuit (ACPR detection means)
21, 71 Base station 32 Temperature detector 42 Voltage detector 51, 61 Usage request detector 73 Receiver circuit 97 Comparator (degradation condition determination means)
Vb bias voltage (drive voltage)

Claims (6)

Communication between a terminal and a base station using a transmission method selection means for selecting any one of a plurality of transmission methods with different peak rates, and a signal of the transmission method selected by the transmission method selection means In a communication system that performs
Deterioration condition determination means for determining whether or not the adjacent channel leakage power rate of the terminal is a deterioration condition,
The transmission system selecting means is configured to select a transmission system having a low peak rate for transmission from the terminal to the base station when the deterioration condition determining means determines that the deterioration condition is satisfied. . The terminal or base station is provided with ACPR detection means for detecting the adjacent channel leakage power rate of the terminal,
2. The deterioration condition determining unit is configured to determine that a deterioration condition is present when the adjacent channel leakage power rate detected by the ACPR detection unit is high, and to determine that the deterioration condition is not satisfied when the adjacent channel leakage power rate is low. The communication system according to 1.   The communication system according to claim 1, wherein the deterioration condition determination unit is configured to determine that the deterioration condition is determined when the temperature of the terminal is high, and that the deterioration condition is not determined when the temperature of the terminal is low.   The communication system according to claim 1, wherein the deterioration condition determination unit is configured to determine that the deterioration condition is determined when the power supply voltage of the terminal is low and to determine that the deterioration condition is not satisfied when the power supply voltage of the terminal is high. Use request detecting means for detecting whether or not there is a request for using a transmission method with a high peak rate from the terminal or base station,
When the transmission request selecting means detects that there is a use request by the use request detecting means in a state where a transmission method having a low peak rate is selected for transmission from the terminal to the base station, the transmission method selecting means The communication system according to claim 1, 2, 3 or 4, wherein the drive voltage is increased to change to a transmission method having a high peak rate. Use request detecting means for detecting whether or not there is a request for using a transmission method with a high peak rate from the terminal or base station,
The transmission method selection means cools the terminal when the use request detection means detects that there is a use request in a state where a transmission method with a low peak rate is selected for transmission from the terminal to the base station. The communication system according to claim 1, 2, 3, or 4, wherein the communication system is changed to a transmission method having a high peak rate.

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