JP2001326700A - Digital radio equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve problems of conventional digital radio equipment that has had extraordinary difficulty of matching its transmission output with a proper level because it is required to reduce the transmission time, in the case of burst transmission where transmission and transmission stop are repeated in a short time in the TDMA system or the like although the transmission characteristic requires control at a large time constant for gradual matching with a proper power level with respect to frequent fluctuations in the output level of a power amplifier due to its secular change and its temperature change to keep the stability of the transmission characteristic by means of maintaining the output level to be a specified value and that has caused a transmission output level in excess of a prescribed range until a peak level is averaged, to match the power level with the proper power level when a peak factor is high. SOLUTION: Feedback signal data whose level is detected are captured only during transmission to obtain an average value and a level of the feedback side is changed to bring the average value to a specified value. Furthermore, when a base band signal output level continues its maximum state, the level of the feedback side is changed by a fixed value obtained in advance to keep the output level at the specified value independently of the communication system and the modulation system, thereby preventing the transmission characteristics from being deteriorated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a negative-feedback type digital radio which performs control for maintaining an output level within a predetermined range by using digital signal processing.

[0002]

2. Description of the Related Art Linear digital modulation, for example, 16QAM
(Quadrature Amplitude Modulation) and π / 4 shift QPS
In a wireless system using K (Quadrature Phase Shift Keying) or the like, it is essential technology to compensate for nonlinear distortion of a power amplifier, and various nonlinear distortion compensation methods (linearizers) are used. Above all, a Cartesian loop negative feedback linearizer is widely used.

A conventional digital radio will be described with reference to FIG. FIG. 2 is a block diagram showing a configuration of a transmitting section of a digital wireless device using a Cartesian negative feedback type linearizer having a function of keeping the output level constant.

[0004] 18 is a digital signal source, 19 is a mapping unit,
20-1 and 20-2 are filter sections, 1 is a baseband signal generator composed of digital signal source 18 and mapping section 19 and filter sections 20-1 and 20-2, and 2-1 and 2-2 are additions Vessels, 3-1 and 3-2
Is a loop filter (LPF), 4 is a quadrature modulator, 5 is a first bandpass filter (BPF), 6 is a first mixer, and 7 is a second mixer.
Bandpass filter (BPF), 8 is a power amplifier (PA), 9 is an antenna, 10 is a directional coupler, 11 is a reference signal generator, 12
Is a first PLL (Phase Locked Loop) frequency synthesizer, 13 is a second PLL frequency synthesizer, 14 is a variable attenuator (variable ATT), 15 is a second mixer, 16 is a quadrature demodulator, 17 is a phase controller, 25 is a level detection unit, and 26 is a level control unit.

[0005] The output of the digital signal source 18 is
And the in-phase component output of the mapping unit 19 is connected to the filter unit 20-1. Similarly, the quadrature component output of the mapping unit 19 is connected to the filter unit 20-2. The output of the filter unit 20-1 is connected to the addition (+) input terminal of the adder 2-1. The output of the adder 2-1 is connected to the LPF3-1. The output of the LPF3-1 is the quadrature modulator 4. Connected to. Similarly, the output of the filter unit 20-2 is connected to the addition (+) input terminal of the adder 2-2, the output of the adder 2-2 is connected to the LPF 3-2, and the output of the LPF 3-2 is orthogonal. Connected to modulator 4. The output of the quadrature modulator 4 is the first BPF 5
And the output of the first BPF 5 is connected to the first mixer 6. The output of the first mixer 6 is connected to the second BPF 7, and the output of the second BPF 7 is connected to PA8. The output of PA8 is connected to directional coupler 10, and the output of directional coupler 10 is connected to antenna 9, variable ATT 14, and level detector 25. The output of the level detector 25 is connected to the level controller 26, and the output of the level controller 26 is connected to the control terminal of the variable ATT 14. The output of the variable ATT 14 is connected to a second mixer 15, and the output of the second mixer 15 is connected to a quadrature demodulator 16. The in-phase component output of the quadrature demodulator 16 is connected to the subtraction (-) input terminal of the adder 2-1. Similarly, the quadrature component output of the quadrature demodulator 16 is connected to the subtraction (-) input side of the adder 2-2. Connected to terminal. The output of the reference signal generator 11 is the first PLL frequency synthesizer 12
And the second PLL frequency synthesizer 13 and the second
The output of the PLL frequency synthesizer 13 is connected to the second mixer 15. The output of the first PLL frequency synthesizer 12 is connected to the quadrature modulator 4 and the phase controller 17,
Are connected to a quadrature demodulator 16.

In FIG. 2, a signal output from a digital signal source 18 is given to a mapping unit 19. Mapping unit 19
Is the modulation scheme specified by the radio (eg, QPSK
Modulation method). The mapped signal is output from the mapping unit 19 to the in-phase component signal I.
And the quadrature component signal Q, the in-phase component signal I passes through the filter unit 20-1 to remove unnecessary components, and the quadrature component signal Q passes through the filter unit 20-2 to remove unnecessary components. Thereby, the in-phase component signal I and the quadrature component signal Q of the baseband signal are output from the baseband signal generator 1, respectively.

The in-phase component I output from the baseband signal generator 1 is added to the in-phase signal i on the feedback side by an adder 2-1 and output, and the quadrature component Q is output by the adder 2-2. Is added to the quadrature component signal q and output. The output of adder 2-1 is LP
It is provided to F3-1, band-limited by LPF3-1, and provided to quadrature modulator 4. Similarly, the output of the adder 2-2 is provided to the LPF 3-2, band-limited by the LPF 3-2, and provided to the quadrature modulator 4.

[0008] A reference signal generator 11 generates a reference frequency signal, and provides the reference frequency signal to a first PLL frequency synthesizer 12 and a second PLL frequency synthesizer 13. First PL
The L frequency synthesizer 12 generates a first local oscillation signal (LO1) based on the input reference frequency signal, and supplies it to the quadrature modulator 4 and the phase controller 17. Further, the second PLL frequency synthesizer 13 generates a second local oscillation signal (LO2) based on the input reference frequency signal, and supplies it to the first mixer 6 and the second mixer 15. The phase controller 17 receives the input first
Of the local oscillation signal is supplied to the quadrature demodulator 16.

A quadrature modulator 4 converts an in-phase component I 'and a quadrature component Q' of an input baseband signal into an IF (intermediate) frequency band by using a first local oscillation signal given from a first PLL frequency synthesizer. And the modulated wave signal is
Give to BPF5. The first BPF 5 removes unnecessary frequency components from the input modulated wave and supplies the same to the first mixer 6. Next, the first mixer 6 converts the input signal to a desired frequency by the second local oscillation signal supplied from the second PLL frequency synthesizer 13 and supplies the signal to the second BPF 7. Second
The BPF 7 removes unnecessary spurious components from the input modulated wave and supplies the same to the PA 8. Further, the PA 8 amplifies the input signal to a specified output level and outputs the amplified signal from the antenna 9 via the directional coupler 10.

[0010] The transmitting section of this radio has a negative feedback linearizer configuration using a Cartesian loop. The directional coupler 10 separates a part of the output signal of the PA8, and
And the level detector 25. The signal passing through the variable ATT 14 is supplied to a second mixer 15. The second mixer 15 frequency-converts the frequency of the signal input from the variable ATT 14 to the IF frequency by the second local oscillation signal, and supplies the IF frequency to the quadrature demodulator 16. The quadrature demodulator 16 quadrature demodulates the input IF frequency signal based on the frequency signal given from the phase controller 17 and outputs the same. The in-phase component i of the baseband signal is subtracted (−) from the adder 2-1. And the orthogonal component q is applied to the subtraction (-) input side of the adder 2-2.

As described above, in the adders 2-1 and 2-2, the input signals I and Q are subtracted by the feedback signals i and q, respectively, and negative feedback is applied. By such an operation, a modulated signal in which nonlinear distortion is compensated is obtained. However, one of the performances of the wireless device is to stabilize the output level. Generally, for example, the output level of the PA8 shown in FIG. 2 is stabilized by keeping the output level constant. However, in the case of the feedback method, PA8
In order to keep the output level constant, adjustment on the feedback side is required. The technique will be described with reference to FIG.

FIG. 3 is a block diagram showing the principle of a feedback type linearizer. 31 is a signal input terminal, 32 is an adder,
33 is a forward section, 34 is a distortion input terminal, 35 is a distortion adder, 36 is a signal input terminal, and 37 is a feedback section.
The signal of the function x (t) is provided from the input terminal 31 and input to the addition (+) input side of the adder 32. The output of the adder 32 is amplified by the forward unit 33 and input to the distortion adder 35. In FIG. 3, the distortion component of the function D (t) generated in the forward unit 33 is provided from the distortion input terminal 34 to the distortion adder 35. Next, the output of the distortion adder 35 is output from the signal output terminal 36 to the function y.
The signal of (t) is output, and is provided to the feedback unit 37. The output of the feedback 37 is input to the subtraction (-) input side of the adder 32.

In FIG. 3, the forward section 33
A (forward gain) of A, feedback section 3
Assuming that the gain (feedback gain) of 7 is β and the loop gain is A · β, the signal output represented by the function y (t) under the condition of A · β≫1 becomes Can be represented.

(Equation 1)

That is, it is understood that the output level is determined only by the feedback gain β, and the output changes when the feedback gain β is moved. Therefore, in order to always adjust the power level to an appropriate level, in FIG. 2, the directional coupler 10 supplies the branched output of the PA 8 to the level detection unit 25, and the level detection unit 25 detects the output level and outputs the output. The level information is provided to the level control unit 26. The level control unit 26 varies the variable ATT control signal according to the input output level information.
The signal is supplied to the TT 14 to change the attenuation of the variable ATT 14, and the directional coupler 10 controls the level of the signal output from the antenna 9 to be constant.

At this time, in order to follow long-term fluctuations such as aging and temperature changes, and to adjust the output signal to an appropriate level, the output signal is gently adjusted to an appropriate power level.
The variable amount is controlled by the level control unit 26, for example, by giving a time constant (for example, several seconds) to the ATT control signal.

[0016]

The above-mentioned prior art includes the following:
In order to control the output level and follow long-term fluctuations such as aging and temperature changes, the time constant (for example, several seconds) should be adjusted slowly to the appropriate power level due to the nature of the fluctuation factors. Great control is needed. However, when performing burst transmission in which transmission and transmission stop are repeated in a short time, such as in the TDMA method, it is necessary to shorten the transmission time (for example, several msec). There was a drawback that it was very difficult. When performing wireless communication, the base station (control station) and the mobile station (terminal station) may transmit at the maximum baseband signal output level (maximum mapping movement distance) in order to synchronize. At this time, if the difference (peak factor) between the peak value and the average value of the transmission output level (baseband signal output level) is large, the transmission output level becomes a predetermined value until the peak value is averaged and adjusted to an appropriate power level. There is a disadvantage that it may exceed the range. In particular, in the case of a linear digital modulation system in which a combination of mapping points having different amplitudes, such as 16QAM, can be further displaced to a mapping point at a diagonal, the probability that the peak factor is large and the transmission output level is large Will be higher. An object of the present invention is to provide a radio device which eliminates the above-mentioned drawbacks and can maintain an output level at a specified value even when performing burst transmission regardless of a communication system and a modulation system. .

[0017]

In order to achieve the above-mentioned object, a transmitter of a radio device according to the present invention converts, for example, a level detection output into a digital signal and obtains, for example, an average value of detection data. By controlling the variable attenuator so that the output level becomes a specified value based on the average value, the output level is maintained at an appropriate power level and transmission characteristics are prevented from deteriorating. At this time, if it is determined that the state of the maximum output level of the baseband signal continues due to the displaced moving distance of the mapping value obtained from the mapping unit in the baseband signal generator, the peak value adjusted in advance is Switching is performed so that the variable attenuator is controlled by a variable attenuator control amount for adjusting to an appropriate power level at the time of output. Also, by using the transmission start and stop signals obtained from the output signal source, the detection data is fetched only during transmission, and the average value is obtained. It is what prevented.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram showing a configuration of a transmission unit of a digital wireless device using the present invention. Components having the same functions as those in FIG. 2 described in the related art are denoted by the same reference numerals. In addition, 18 'is a digital signal source, 19' is a mapping unit, 21 is a control control unit, 22 is an output level control unit, and 1 'is a digital signal source 18', mapping unit 19 ',
A baseband signal generator composed of filter units 20-1 and 20-2, a control control unit 21, and an output level control unit 22;
23 is a D / A converter and 24 is an A / D converter.

The connection in FIG. 1 is almost the same as the connection described in FIG. However, the digital signal source 18 and the mapping unit
Instead of 19, a digital signal source 18 'and a mapping unit 19 are provided. The output of the level control unit 26 is variable ATT14.
Instead, it is connected to the A / D converter 24. Furthermore, the A / D converter 24
Is connected to the output level control unit 22, the output of the output level control unit 22 is connected to the D / A converter 23, and the output of the D / A converter 23 is connected to the variable ATT 14. Also, the mapping unit 1
The output of the moving distance information of the mapping from 9 'is newly connected to the control controller 21. Control control unit 21
Is connected to the digital signal source 18 ', and the control controller 21 turns on / off the average value calculation.
The off signal output is connected to the output level control unit 22, and the data output change signal output of the control control unit 21 is connected to the output level control unit 22.

Referring to FIG. 1, a baseband signal generator
From 1 ', the in-phase component signal I and the quadrature component signal Q of the baseband signal are output in the same operation as the operation described in FIG. Further, the in-phase component signal I and the quadrature component signal Q of the baseband signal output from the baseband signal generator 1 ′ are given to the adders 2-1 and 2-2, respectively, and are output from the antenna 9. The operation and the operation until the signal demultiplexed by the directional coupler 10 is fed back to the adders 2-1 and 2-2 are the same as the operations described in FIG.

However, in FIG. 1, control of whether or not to output a baseband signal from the baseband signal generator 1 'is performed by the control control unit 21 by an on / off signal (on / off signal).
The control signal is sent to the output level controller 22 at the same time. The output level control unit 22 receives the digital data supplied from the A / D converter 24 according to the on / off control signal, and performs a processing operation for calculating an average value or stops the processing operation. Perform switching.

In FIG. 1, when a part of the power of the output signal is fed back by the directional coupler 10 and the power level fed back by the variable ATT 14 is converted into an appropriate value, the directional coupler 10 feeds back. The output signal is supplied to a level detection unit 25, and the input signal is level-detected by the level detection unit 25 and supplied to the A / D converter 24. The A / D converter 24 converts the level-detected signal into digital data and supplies the digital data to the output level control unit 22. When the baseband signal is output, the output control unit 22 performs a processing operation of capturing digital data input from the A / D converter 24, calculates an average value of the captured data,
According to the average value, a control signal is supplied to the variable ATT 14 via the D / A converter 23 so that the output level of the PA8 becomes a specified value, and the power level of the feedback signal is controlled so that the transmission output becomes the specified level. I do.

On / off of the operation of calculating the average value in the output level control unit 22 is controlled by an average value calculation on / off signal given from the control control unit 21. Only during transmission, the digital data supplied from the A / D converter 24 is controlled to be fetched, and the average value of the fetched digital data is calculated. That is, the information on the mapping moving distance obtained by the mapping unit 19 'is given to the control control unit 21, and the control control unit 21 determines the moving distance of the mapping value. For example, when the moving distance of the mapping value is equal to or greater than a predetermined value, an average value calculation off signal is provided to the output level control unit 22. The output level control unit 22 to which the average value calculation off signal is input stops the operation of taking in the data supplied from the A / D converter 24 and the operation of calculating the average value.

The control control section 21 outputs an average value calculation off signal and, at the same time, supplies the output level control section 22 with a data output change signal for outputting fixed data. The fixed data is stored in the output level control unit 22 as a control value given to the variable ATT 14 by the output level control unit 22 via the D / A converter 23 at a predetermined constant value. The variable ATT14 is controlled so that the output becomes an appropriate power level when output. This value is obtained experimentally in advance. Thereby, the base station (control station)
And the mobile station (terminal station), so that the baseband signal output level is maximized, that is, when the transmission is performed with the mapping movement distance maximized, in particular, even in a modulation method having a large peak factor such as 16QAM, The transmission output level does not exceed a predetermined range before the peak value is averaged and adjusted to an appropriate power level.

When transmission is stopped (when the baseband signal is not output from the baseband signal generator 1 '), the variable ATT14 is fixed to the last calculated control value (fixed attenuation). Control. Therefore, at the start of the next transmission, the attenuation set immediately before
Held in T14.

The above-described averaging calculation process is performed, for example, by
This is continuously executed during transmission from when the power of the digital radio is turned on to when it is turned off (including reset). Therefore, the average value is held even when the transmission is stopped, and a control signal is given to the variable ATT 14 according to the held average value at the start of the next transmission. As a circuit for executing the averaging process, for example, a smoothing circuit is used.
Further, in the above embodiment, the transmission operation is turned on / off by the control control unit 21. Conversely, an on / off signal is added to the transmission signal output from the signal source 18 'to control the transmission operation. 21 may be controlled.

The relationship between the transmission operation and the control state of the variable ATT 14 in one embodiment of the digital radio of the present invention will be described with reference to FIG. FIG. 4 is a diagram for explaining the relationship between the operation state of the average value calculation processing in the output level control unit 22 and the control state of the variable ATT 14 when the wireless device is transmitting and not transmitting. . (a) is an average value calculation on / off signal output from the control control unit 21 according to the transmission state of the wireless device (the transmission level (ON) is the LO level, and the transmission state is off (OFF))
HI level), (b) shows a state in which the output level control unit 22 is executing the average value calculation processing (ON state: ON) and a state in which it is not executing (OFF state: OFF), and (c) shows The content of the control signal output from the output level control unit 22 to the variable ATT 14 is shown.

As shown in FIG. 4, when the transmission unit of the digital radio is transmitting (ON state), the output level control unit 22 takes in the input data, executes an average value calculation process, and executes the average value calculation. The attenuation of the variable ATT 14 is controlled in accordance with. When the transmission unit of the digital wireless device is in the transmission stop state (OFF state), the output level control unit 22 does not take in the input data, but executes the average value calculation processing last and retains the average value held. The control signal (fixed control value) according to the value is continuously transmitted to the variable ATT 14 or the transmission of the control signal is stopped. Give to. For example, in the TDMA system, when one frame is 40 msec and there are 4 CHs, the transmission time of each channel is 10 msec.

[0029]

As described above, according to the present invention, in order to keep the transmission output level within a predetermined range, the level detected data is converted into a digital signal, and the detected data is converted only when the radio is transmitting. The average value is acquired, the level on the feedback side is changed so that the average value becomes the specified value, and when the maximum output level of the baseband signal continues, the feedback side is determined by the fixed value obtained in advance. , The output level can be kept at a specified value irrespective of the communication system and the modulation system, and the stability of the transmission characteristics can be maintained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of a configuration of a transmission unit of a digital wireless device of the present invention.

FIG. 2 is a block diagram illustrating a configuration of a transmission unit of a conventional digital wireless device.

FIG. 3 is a principle configuration diagram of a feedback type linearizer.

FIG. 4 is a diagram for explaining a relationship between a transmission operation and a control state of a variable ATT 14 in one embodiment of the digital wireless device of the present invention.

[Explanation of symbols]

1, 1 ': baseband signal generator, 2-1 and 2-2: adder, 3-1 and 3-2: LPF, 4: quadrature modulator, 5: BPF,
6: mixer, 7: BPF, 8: PA, 9: antenna, 1
0: Directional coupler, 11: Reference signal generator, 12, 13: P
LL frequency synthesizer, 14: variable ATT, 15: mixer, 16: quadrature demodulator, 17: phase controller, 18, 18 ':
Digital signal source, 19, 19 ': mapping unit, 20-1,
20-2: Filter section, 21: Control section, 22:
Output level controller, 23: D / A converter, 24: A / D converter, 25: Level detector, 26: Level controller.

Claims (9)

[Claims] 1. A digital radio using a feedback-type linearizer for generating a baseband signal, amplifying the baseband signal, and transmitting the amplified signal, wherein a transmission output level of the digital radio is set within a predetermined range. A digital wireless device that varies and controls the signal level of a feedback signal in order to maintain the digital wireless device by controlling a signal level of the feedback signal and a generation and stop of the generation of the baseband signal. Transmission control means for controlling transmission and stop of transmission of the transmitter; level detection means for detecting the signal level of the feedback signal; and signal level for varying the signal level of the feedback signal based on the detected signal level. Calculating means for calculating variable information; and level control means for generating a level control signal corresponding to the signal level variable information. The control means, digital radios and controls the calculation means so as to stop the operation of calculating the signal level variable information in the average value calculating means at the time of the radio transmission stop state. 2. The digital wireless device according to claim 1, further comprising means for holding said variable level information when said transmission is stopped, and corresponding to said stored level variable information in said level control means when starting next transmission. A digital radio, wherein the signal level of the feedback signal is started to be varied by a level control signal. 3. The digital wireless device according to claim 1, wherein the signal level variable information is an average value of a signal level of the feedback signal detected by the level detection means during a predetermined time. Digital radio. 4. The digital wireless device according to claim 1, wherein said baseband signal output level is detected to be a maximum state, and said transmission output level is controlled to a specified value. Storage means for storing fixed data for performing the operation. When the baseband signal output level is in the maximum state, the level control means changes the feedback signal level based on the fixed data. A digital wireless device characterized by the above-mentioned. 5. The digital radio according to claim 4, wherein when said baseband signal output level is at a maximum, said calculation means stops calculating said signal level variable information. Digital radio. 6. The digital wireless device according to claim 5, wherein when the calculating means stops calculating the signal level variable information, the calculating means holds the signal level variable information, and the next signal level is held. The digital radio device according to claim 1, wherein when the calculation of the variable information is started, the signal level of the feedback signal is changed by a level control signal corresponding to the held signal level variable information. 7. The digital wireless device according to claim 5, wherein when the calculation unit stops calculating the signal level variable information, the level control unit holds the signal level variable information and outputs the next signal. A digital radio device, wherein, at the start of calculating variable level information, the signal level is changed by a level control signal corresponding to the held variable level information. 8. A digital wireless device using a negative feedback linearizer that generates a baseband signal, amplifies the baseband signal, and transmits the amplified baseband signal, wherein the generation and stop of the generation of the baseband signal are controlled. A control unit, an in-phase component adder for inputting an in-phase component of the baseband signal, a quadrature component adder for inputting a quadrature component, and an in-phase component signal output by the in-phase component adder and the quadrature component adder, respectively. A loop filter that inputs a quadrature component signal and limits the band, a quadrature modulator that quadrature modulates an in-phase component signal and a quadrature component signal respectively input from the loop filter with a first local oscillation signal, and outputs a modulated wave signal And a first bandpass filter for removing unnecessary components of the modulated wave signal, and a signal input from the first bandpass filter. A first mixer for converting the frequency to a desired frequency by using the second local oscillation signal, a second band-pass filter for removing unnecessary spurious components from a signal input from the first mixer, and a second band-pass filter. An amplifier for amplifying a signal input from the filter; a directional coupler for demultiplexing a part of the signal amplified by the amplifier; and an output unit for outputting the signal amplified by the amplifier via the directional coupler. A variable attenuator for attenuating a signal demultiplexed from the directional coupler; a second mixer for converting a signal input from the variable attenuator into a desired frequency by the second local oscillation signal; 2 is quadrature-demodulated by the first local oscillation signal, and the in-phase component of the baseband signal is subtracted from the input-subtracted input side of the in-phase component adder by the baseband signal. A quadrature demodulator that outputs quadrature components of the command signal to a subtracted input side of the quadrature component adder, a level detector that performs level detection on a signal that is split from the directional coupler, and a level detector that detects A D / A converter for digitally converting an input signal; calculating an average value by taking in data input from the D / A converter; calculating an attenuation amount of the variable attenuator so that the average value becomes a predetermined value. An output level control unit that provides a signal for control to the variable attenuator, wherein the control unit causes the average value calculation unit to calculate an average value of the signal level when generating the baseband signal, When the control unit stops generating the baseband signal, the control unit causes the average value calculating unit to stop calculating the average value of the signal level, and the baseband signal is generated. Digital radios only calculates the average value, characterized in that keeping the transmission output level to the specified value according to the average value when the time that. 9. A digital wireless device using a negative feedback linearizer that generates a baseband signal, amplifies the baseband signal, and transmits the amplified baseband signal, wherein the generation and stop of the generation of the baseband signal are controlled. A control unit, an in-phase component adder for inputting an in-phase component of the baseband signal, a quadrature component adder for inputting a quadrature component, and an in-phase component signal output by the in-phase component adder and the quadrature component adder, respectively. A loop filter that inputs a quadrature component signal and limits the band, a quadrature modulator that quadrature modulates an in-phase component signal and a quadrature component signal respectively input from the loop filter with a first local oscillation signal, and outputs a modulated wave signal And a first bandpass filter for removing unnecessary components of the modulated wave signal, and a signal input from the first bandpass filter. A first mixer for converting the frequency to a desired frequency by using the second local oscillation signal, a second band-pass filter for removing unnecessary spurious components from a signal input from the first mixer, and a second band-pass filter. An amplifier for amplifying a signal input from the filter; a directional coupler for demultiplexing a part of the signal amplified by the amplifier; and an output unit for outputting the signal amplified by the amplifier via the directional coupler. A variable attenuator for attenuating a signal demultiplexed from the directional coupler; a second mixer for converting a signal input from the variable attenuator into a desired frequency by the second local oscillation signal; 2 is quadrature-demodulated by the first local oscillation signal, and the in-phase component of the baseband signal is subtracted from the input-subtracted input side of the in-phase component adder by the baseband signal. A quadrature demodulator that outputs quadrature components of the command signal to a subtracted input side of the quadrature component adder, a level detector that performs level detection on a signal that is split from the directional coupler, and a level detector that detects A D / A converter for digitally converting an input signal; calculating an average value by taking in data input from the D / A converter; calculating an attenuation amount of the variable attenuator so that the average value becomes a predetermined value. An output level control unit that supplies a signal for control to the variable attenuator; a detection unit that detects whether or not the output level of the baseband signal is at a maximum; and a state where the baseband signal output level is at a maximum. Storage means for storing fixed data for the output level control unit to control the transmission output level to a specified value, wherein the baseband signal output level is maximum. In some cases, digital radio, characterized by varying the signal level by the fixed data.