JP5019377B2 - Wireless transmitter - Google Patents

Description

  The present invention relates to a radio transmitter including a nonlinear distortion compensation circuit that is used in the field of mobile communications, for example, and compensates for nonlinear distortion of a power amplifier by a negative feedback method.

  In the mobile communication field, digital radio transmitters that use linear modulation schemes such as QPSK and multilevel QAM are generally used. In this type of wireless transmitter, leakage power to adjacent channels is strictly regulated from the viewpoint of effective use of frequencies. For this reason, it is necessary to compensate for interference to adjacent channels caused by nonlinear distortion of the power amplifier.

  Therefore, a wireless transmitter having a Cartesian negative feedback circuit has been proposed. A radio transmitter including a Cartesian negative feedback circuit performs negative feedback control on a transmission baseband signal separately for an in-phase component and a quadrature component, and is configured as follows, for example.

  That is, the transmission baseband signal output from the baseband circuit divided into the in-phase component (I component) and the quadrature component (Q component) is input to the quadrature modulator. In the quadrature modulator, a carrier wave generated from a frequency synthesizer is modulated by the transmission baseband signal. The modulated carrier wave (modulated wave signal) has its unwanted wave component removed by a band-pass filter, the signal level is adjusted by a variable attenuator, and then input to a power amplifier to set a preset transmission power level. Power is amplified up to. The modulated wave signal output from the power amplifier passes through an isolator, and then a harmonic component is cut by a low-pass filter and transmitted from an antenna.

  On the other hand, a part of the modulated wave signal output from the power amplifier is extracted by a directional coupler and input to a Cartesian negative feedback circuit. In the Cartesian negative feedback circuit, the signal level of the extracted modulated wave signal is detected, the detected value of the signal level is compared with a preset reference value, and a control signal corresponding to the difference is generated. The Then, the signal level of the modulated wave signal taken out by the directional coupler is adjusted by the control signal in the variable attenuator and then input to the quadrature demodulator. In the quadrature demodulator, the inputted modulated wave signal is demodulated by the carrier wave obtained by shifting the carrier wave generated from the frequency synthesizer to the opposite phase by the phase shifter. The feedback signal obtained by this demodulation is added to the transmission baseband signal for each in-phase component and quadrature component by an adder, and the transmission baseband signal after this addition is input to the quadrature modulator.

Thus, even if the modulated wave signal output from the power amplifier changes due to nonlinear distortion of the power amplifier, a feedback signal for canceling this change component is generated by the Cartesian negative feedback circuit and fed back to the transmission baseband signal. Thus, the level of the modulated wave signal is kept constant. The configuration of a wireless transmitter including the Cartesian negative feedback circuit described above is described in, for example, Patent Document 1.
JP 2006-86928 A

However, the wireless transmitter having the conventional Cartesian negative feedback circuit described above has the following problems to be solved.
That is, in the wireless transmitter, the transmission power may be set to a different value depending on the specifications of the system to be applied. For example, 10 W is set for a system with a large wireless communication area, 1 W is set for a medium-sized system, and 0.1 W is set for a small-sized system. In order to cope with a plurality of specifications with different transmission powers, conventionally, for example, the transmission power of a power amplifier is set to a maximum value (for example, 10 W), and a specification with a smaller transmission power is output from the power amplifier. A configuration has been proposed in which the transmission power level of the modulated wave signal is attenuated to a level required by a variable attenuator.

  However, in such a configuration, a variable attenuator must be provided between the power amplifier and the antenna, which leads to a complicated circuit configuration and an increase in the number of parts. Further, since the power amplifier always operates to generate the maximum power, the power consumption is large and the power efficiency is lowered.

  The present invention has been made paying attention to the above circumstances, and the object of the present invention is to cope with a plurality of specifications having different transmission powers without causing an increase in the number of parts or a complicated circuit configuration. It is to provide a wireless transmitter.

In order to achieve the above object, a first aspect of the present invention includes a modulation circuit that modulates a carrier wave signal by a transmission baseband signal and outputs a modulated wave signal, and a plurality of amplifiers having different transmission power levels. An amplifier that outputs a transmission power level corresponding to a required system specification is selected from the amplifiers of the selected amplifier, and a modulated wave signal output from the modulation circuit is selected by the selected amplifier. a power amplifier circuit for amplifying and outputting the transmission power level corresponding to, this feedback modulated wave signal the carrier is taken out a part of the modulated wave signal output from the power amplifier circuit as a feedback modulated wave signal A nonlinear distortion compensation circuit that compensates for the nonlinear distortion of the power amplifier by demodulating by the demodulator and negatively feeding back the demodulated signal to the transmission baseband signal; In the radio transmitter comprising, in said nonlinear distortion compensating circuit, the extraction circuit for taking out a part of the modulated wave signal output from the power amplifier as a feedback modulated wave signal, transmission of the selected amplifier by the correction value corresponding to the power level, by correcting to the signal level of the feedback modulated wave signal extracted by said extraction circuit, the signal level of the feedback modulated wave signal, which of said plurality of amplifiers A correction circuit that corrects the signal to be constant even when selected, and a signal level of the feedback modulated signal corrected by the correction circuit is compared with a preset reference value, and a control signal corresponding to the difference is generated. Yes and the control signal generating circuit, a control signal generated by said control signal generating circuit, a signal level of the feedback modulated wave signal extracted by said extraction circuit The control to return the modulated wave signal whose signal level is variably controlled is obtained by configured with a variable control circuit for input to the demodulator.
A second aspect of the present invention is a modulation circuit that modulates a carrier wave signal with a transmission baseband signal and outputs a modulated wave signal , and can selectively output a plurality of transmission power levels, and A variable gain control type power amplifier in which a transmission power level is selectively set according to a system specification required from these transmission power levels is provided, and the modulated wave signal output from the modulation circuit is a power amplifier circuit for amplifying and outputting the variable gain controlled power amplifier, takes out a part of the modulated wave signal output from the power amplifier as a feedback modulated wave signal, said the feedback modulated wave signal A non-linear distortion compensation circuit that compensates for the non-linear distortion of the power amplifier by demodulating by a demodulator with a carrier wave and negatively feeding back the demodulated signal to the transmission baseband signal In the radio transmitter, to said nonlinear distortion compensating circuit, the extraction circuit for taking out a part of the modulated wave signal output from the power amplifier as a feedback modulated wave signal, the power amplifier of the variable gain control type the correction value corresponding to the set transmission power level, by correcting to the signal level of the feedback modulated wave signal extracted by said extraction circuit, the variable gain control signal level of the feedback modulated wave signal A correction circuit for correcting the transmission power level to be constant regardless of which transmission power level is set, and comparing the signal level of the feedback modulated signal corrected by the correction circuit with a preset reference value and a control signal generating circuit for generating a control signal corresponding to the difference, the control signal generated by said control signal generating circuit, taken by the extraction circuit Is the signal level of the feedback modulated wave signal is variably controlled has a feedback modulated wave signal whose signal level is variably controlled is obtained by configured with a variable control circuit for input to the demodulator.
As an example, the correction circuit has a correction table that stores correction values in association with each of a plurality of transmission power levels according to the specifications of the system to be applied, and the correction table is used according to the required specifications. The correction value corresponding to the transmitted power level is selectively read, and the read correction value is added to or subtracted from the signal level of the feedback modulated wave signal extracted by the extraction circuit .

  Therefore, even if power amplifiers with different transmission power values are used according to the required specifications, the nonlinear distortion compensation circuit corrects the signal level of the feedback modulated wave signal to be within the preset signal level range. Then, negative feedback control of the transmission baseband signal is performed according to the difference between the signal level of the corrected feedback modulated wave signal and the reference value. That is, even when power amplifiers having different transmission power values are used, negative feedback control is performed in the nonlinear distortion compensation circuit as in the case where one type of transmission power is output. For this reason, it is not necessary to provide a variable attenuator in the transmission output stage, and it is not necessary to provide negative feedback loops for nonlinear distortion compensation, for example, in accordance with the number of required transmission power values. The power efficiency can be reduced, and further increase in circuit scale can be prevented.

  That is, according to one aspect of the present invention, it is possible to provide a radio transmitter that can cope with a plurality of specifications having different transmission powers without increasing the number of parts or complicating the circuit configuration. .

Embodiments according to the present invention will be described below with reference to the drawings.
FIG. 1 is a block diagram showing a configuration of a wireless transmitter according to the present invention.
In the figure, an in-phase component (I component) and a quadrature component (Q component) of a transmission baseband signal output from the baseband circuit (BB) 1 are input to a quadrature modulator (MOD) 2. In the quadrature modulator 2, the carrier wave generated from the frequency synthesizer (SYN) 3 is quadrature modulated by the transmission baseband signal. The modulated carrier wave (modulated wave signal) has its unwanted wave component removed by the band-pass filter 4 and the signal level is adjusted by the variable attenuator (ATT) 5, which is then input to the power amplifier 6 for power amplification. Is done. The modulated wave signal output from the power amplifier 6 passes through an isolator 7, and then a harmonic component is cut by a low-pass filter 8 and transmitted from an antenna 9.

  As the power amplifier 6, a plurality of amplifiers having different transmission powers are prepared in advance, and an amplifier having a transmission power according to a required specification is selected and used. If a variable gain control type power amplifier capable of selectively generating a plurality of transmission powers according to the required specifications can be prepared, this variable gain control type power amplifier can be used. Good.

  On the other hand, the nonlinear distortion compensation circuit 10 is composed of a Cartesian negative feedback circuit and is configured as follows. That is, a part of the modulated wave signal output from the power amplifier 6 is extracted by the directional coupler 11 and input to the variable attenuator (ATT) 12 as a feedback modulated wave signal. At the same time, the feedback modulated wave signal extracted by the directional coupler 11 is input to a level detector (DET) 16 where the signal level is detected. The detected value of the signal level is input to the control circuit (CONT) 20 after the individual adjustment of the detected value is absorbed by the fine adjustment circuit 17.

  The control circuit 20 corrects the signal level detection value of the feedback modulated wave signal to be a constant value regardless of the transmission power value set in the power amplifier 6, and then corrects the signal level detection value after the correction. And a control signal representing the difference between a predetermined reference value and a preset reference value, and the gain of the variable attenuator 12 is controlled by this control signal. The configuration of the control circuit 20 will be described in detail later.

  The variable attenuator 12 adjusts the signal level of the input feedback modulated wave signal according to the gain specified by the control signal, and inputs the adjusted feedback modulated wave signal to the quadrature demodulator (DEMOD) 13. To do. The quadrature demodulator 13 demodulates the adjusted feedback modulated wave signal with the demodulation carrier wave, and outputs a feedback signal composed of an in-phase component and a quadrature component. The in-phase component and the quadrature component of the feedback signal are respectively subtracted from the in-phase component and the quadrature component of the transmission baseband signal by the adders 15I and 15Q, and the transmission baseband signal after the subtraction is subjected to the quadrature modulation at the next transmission processing timing. Is input to the device 2. Thus, a negative feedback loop for compensating for the nonlinear distortion of the power amplifier 6 is formed.

  In order to stabilize the negative feedback loop, it is necessary that the in-phase component and the quadrature component of the feedback signal have opposite phases with respect to the in-phase component and the quadrature component of the transmission baseband signal. For this purpose, the carrier wave generated from the frequency synthesizer 3 is phase-shifted by the phase shifter 14 so as to have an opposite phase, and the carrier wave after the transfer is used as the demodulation carrier wave.

  By the way, the control circuit 20 is configured as follows. FIG. 2 is a block diagram showing the configuration. That is, the signal level detection value of the feedback modulated wave signal output from the fine adjustment circuit 17 is converted into a digital value by the analog / digital converter (A / D) 21 and then input to the adder 22. Further, the correction value read from the correction table 23 is also input to the adder 22.

  In the correction table 23, for example, as shown in FIG. 3, a correction value T2 is stored in association with each of a plurality of transmission powers T1 (0.01 W, 0.1 W, 1 W, 10 W) according to required specifications. A value corresponding to the transmission power value set in the power amplifier 6 is selectively read out from these correction values T2.

  The adder 22 subtracts the correction value read from the correction table 23 from the signal level detection value of the digitized feedback modulated signal, thereby obtaining the digitized feedback modulated signal. The signal level detection value is corrected so as to be constant regardless of the transmission power value.

  The comparator 24 compares the corrected signal level detection value output from the adder 22 with the reference value read from the reference value storage unit 25. Then, a comparison signal representing the magnitude relationship is given to the adder / subtractor 26. The adder / subtractor 26 adds / subtracts a constant step value read from the step value generator 27 to the control signal output from the adder / subtractor 26 at the previous timing according to the comparison signal.

  The addition / subtraction control signal output from the adder / subtractor 26 is added with the initial value read from the initial value storage unit 29 in the adder 28, and then added to the digital / analog converter (D / A) 30. It is converted into an analog signal and given to the variable attenuator 12 as a gain control voltage.

Next, the operation of the nonlinear distortion compensation circuit 10 configured as described above will be described.
The nonlinear distortion compensation circuit 10 is configured by a Cartesian negative feedback circuit. In the Cartesian negative feedback circuit, as shown in FIG. 4, the product of the forward gain A and the feedback gain β (open loop gain Aβ) is a compensation amount for the distortion D generated in the forward direction. In the closed loop, it is the reciprocal (1 / β) of the feedback direction gain.

Now, in a wireless transmitter equipped with such a nonlinear distortion compensation circuit, when a plurality of transmission outputs are selectively set according to the required specifications, the nonlinear distortion compensation circuit is To work.
(1) When the output power value is set to 1W
First, the output power value is adjusted to 1 W, the feedback gain β at this time is determined, and the forward gain A that satisfies the distortion compensation amount Aβ required at this time is determined.
Then, a part of the modulated wave signal output from the power amplifier 6 in this state is taken out by the directional coupler 11, and the signal level is detected by the level detector 16. The signal level detection value is finely adjusted by the fine adjustment circuit 17 to absorb individual differences in detection level, and then input to the control circuit 20.

  In the control circuit 20, the signal level detection value is converted into a digital value by the A / D 21 and then input to the adder 22. At this time, the signal level detection value when the transmission power is 1 W is, for example, 1.5 V as shown in FIG. On the other hand, at this time, the correction value (0.5 V) when the transmission power is 1 W is read from the correction table 23 and subtracted from the signal level detection value (1.5 V) in the adder 22. For this reason, the corrected signal level detection value (1 V) is output from the adder 22.

  In the comparator 24, the corrected signal level detection value output from the adder 22 is compared with the reference value (1V) read from the reference value storage unit 25, and a comparison signal representing the magnitude relationship is added or subtracted. Is provided to the vessel 26. In the adder / subtracter 26, a constant step value read from the step value generator 27 is added to or subtracted from the control signal output from the adder / subtractor 26 at the previous timing in accordance with the comparison signal.

  For example, it is assumed that the signal level detection value after correction is 1.1 V due to the influence of nonlinear distortion and is larger than the reference value of 1 V. In this case, the comparison signal “H” is output from the comparator 24, and accordingly, the adder / subtracter 26 adds a constant step value to the control signal output from the adder / subtractor 26 at the previous timing. On the other hand, it is assumed that the signal level detection value after correction is, for example, 0.9V, which is smaller than the reference value of 1V. In this case, the comparison signal “L” is output from the comparator 24, and accordingly, the adder / subtracter 26 subtracts a constant step value from the control signal output from the adder / subtractor 26 at the previous timing.

  The control signal after the addition / subtraction process output from the adder / subtractor 26 is added to the initial value read from the initial value storage unit 29 in the adder 28, and then converted to an analog signal by the D / A 30. This is given as a gain control voltage to the attenuator 12. Therefore, the gain of the variable attenuator 12 is controlled. As a result, the signal level of the feedback modulated signal extracted by the directional coupler 11 is adjusted, and the adjusted feedback modulated signal is converted into a quadrature demodulator. 13 is input.

  In the quadrature demodulator 13, the adjusted feedback modulated wave signal is demodulated by a demodulating carrier wave. Then, the in-phase component and the quadrature component of the feedback signal obtained by this demodulation are subtracted from the in-phase component and the quadrature component of the transmission baseband signal in the adders 15I and 15Q, respectively. The signal is input to the quadrature modulator 2 at the transmission processing timing. Thus, the nonlinear distortion of the power amplifier 6 is compensated.

(2) When the transmission power value is changed to 0.1W or 0.01W
When the transmission power value is 0.1 W, the signal level detection value of the modulated wave signal extracted by the directional coupler 11 is 1.1 V as shown in FIG. 3, for example. On the other hand, at this time, the correction value (0.1 V) when the transmission power is 0.1 W is read from the correction table 23 and subtracted from the signal level detection value (1.1 V) in the adder 22. For this reason, the corrected signal level detection value (1 V) is output from the adder 22.

When the transmission power value is 0.01 W, the signal level detection value of the modulated wave signal extracted by the directional coupler 11 is 1.01 V as shown in FIG. 3, for example. On the other hand, at this time, the correction value (0.01 V) when the transmission power is 0.01 W is read from the correction table 23 and subtracted from the signal level detection value (1.01 V) by the adder 22. For this reason, the corrected signal level detection value (1 V) is output from the adder 22.
That is, the signal level detection value of the modulated wave signal is always a constant value (1 V) as shown in FIG. 3 regardless of whether the transmission power value is set to 1 W, 0.1 W, or 0.01 W. It is corrected as follows.

Thereafter, similarly to the case where the transmission power described in (1) is 1 W, the corrected signal level detection value output from the adder 22 is compared with the reference value (1 V) in the comparator 24, and the The adder / subtracter 26 adds / subtracts a constant step value to / from the control signal in accordance with the comparison signal representing the magnitude relationship. The control signal after the addition / subtraction process output from the adder / subtractor 26 is added to the initial value by the adder 28, converted to an analog signal by the D / A 30, and given to the variable attenuator 12 as a gain control voltage. It is done. As a result, the signal level of the feedback modulated wave signal is adjusted in the variable attenuator 12, and the adjusted feedback modulated wave signal is demodulated by the demodulating carrier wave in the quadrature demodulator 13, and then the adders 15I and 15Q. Negative feedback.
Thus, even when the transmission power value is changed to 0.1 W or 0.01 W, the Cartesian negative feedback loop operates as in the case where the transmission power is set to 1 W, and the nonlinear distortion of the power amplifier 6 is compensated. The

  As described above, in this embodiment, the nonlinear distortion compensation circuit 10 stores correction values in association with transmission power specification lineups, that is, transmission power (0.01 W, 0.1 W, 1 W, 10 W). A correction table 23 is provided, and the signal level detection value of the feedback modulated wave signal is corrected by the correction value read from the correction table 23 and then used for Cartesian negative feedback control.

  Therefore, no matter what the transmission power is set, the nonlinear distortion compensation circuit 10 performs the Cartesian negative feedback control under the same conditions, thereby changing the circuit configuration of the nonlinear distortion compensation circuit for each transmission power. It becomes possible to cope without. In addition, since it is not necessary to provide a variable attenuator for variably setting the transmission power at the transmission output stage, the number of circuit components can be reduced accordingly.

  The present invention is not limited to the above embodiment. For example, in the embodiment, the gain of the variable gain control type power amplifier is variably set, or the power amplifier having a desired gain is selected from a plurality of power amplifiers having a fixed gain. The case where the transmission power value of the specification is set has been described as an example. However, the present invention is not limited to this, and the transmission power value may be variably set by variably setting the gain of the variable attenuator 12 provided in the nonlinear distortion compensation circuit 10 in accordance with the requested transmission power value. Good.

  This can be realized by the following configuration, for example. That is, the control circuit 20 stores a plurality of initial values corresponding to the required transmission power value in the initial value storage unit 29. Then, an initial value corresponding to the requested transmission power value is read from the initial value storage unit 29, and this initial value is added to the control signal by the adder 28 to generate a gain control voltage, which can be varied by this gain control voltage. The gain of the attenuator 12 is controlled. If comprised in this way, feedback direction gain (beta) can be variably set according to the required transmission power value.

  In the embodiment, the correction table 23 is provided, and the correction value corresponding to the required transmission power is read to correct the signal level detection value of the feedback modulated wave signal. However, the present invention is not limited to this, and a plurality of reference values corresponding to required transmission power values are stored in the reference value storage unit 25. Then, the reference value corresponding to the requested transmission power value may be read from the reference value storage unit 25 and compared with the signal level detection value of the feedback modulated signal by the comparator 24.

In addition, the application of the wireless transmitter, the modulation method, the circuit configuration of the nonlinear distortion compensation circuit, and the like can be variously modified without departing from the scope of the present invention.
In short, the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine suitably the component covering different embodiment.

It is a circuit block diagram which shows the circuit structure of the radio transmitter concerning this invention. FIG. 2 is a block diagram illustrating a configuration of a control circuit that is a main part of the wireless transmitter illustrated in FIG. 1. FIG. 3 is a diagram illustrating an example of a configuration of a correction table provided in the control circuit illustrated in FIG. 2. FIG. 2 is an equivalent circuit diagram of the wireless transmitter illustrated in FIG. 1.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Baseband circuit (BB), 2 ... Orthogonal modulation circuit (MOD), 3 ... Frequency synthesizer, 4 ... Band pass filter, 5 ... Variable attenuator, 6 ... Power amplifier, 7 ... Isolator, 8 ... Low pass filter , 9 ... antenna, 10 ... nonlinear distortion compensation circuit, 11 ... directional coupler, 12 ... variable attenuator, 13 ... quadrature demodulator (DEMOD), 14 ... phase shifter, 15I, 15Q ... adder, 16 ... level Detector (DET), 17 ... fine adjustment circuit, 20 ... control circuit (CONT), 21 ... analog / digital converter (A / D), 22 ... adder, 23 ... correction table, 24 ... comparator, 25 ... Reference value storage unit, 26 ... adder / subtractor, 27 ... step value generator, 28 ... adder, 29 ... initial value storage unit, 30 ... digital / analog converter (D / A).

Claims (3)

A modulation circuit that modulates a carrier wave signal with a transmission baseband signal and outputs a modulated wave signal ;
A plurality of amplifiers having different transmission power levels, an amplifier that outputs a transmission power level corresponding to the required system specifications is selected from these amplifiers, and the modulated wave signal output from the modulation circuit is A power amplifier circuit that amplifies and outputs to a transmission power level according to the required system specifications by the selected amplifier;
Taking out a part of the modulated wave signal output from the power amplifier circuit as a feedback modulated wave signal, the demodulated signal the feedback modulated wave signal is demodulated by the demodulator by the carrier to the transmission baseband signal A non-linear distortion compensation circuit that compensates for non-linear distortion of the power amplifier by negative feedback,
The nonlinear distortion compensation circuit includes:
A circuit for extracting a part of the modulated wave signal output from the power amplifier circuit as a feedback modulated wave signal;
By the correction value corresponding to the transmission power level of the selected amplifier, by correcting to the signal level of the feedback modulated wave signal extracted by said extraction circuit, the signal level of the feedback modulated wave signal, A correction circuit for correcting so as to be constant when any of the plurality of amplifiers is selected;
A control signal generation circuit that compares the signal level of the feedback modulated wave signal corrected by the correction circuit with a preset reference value and generates a control signal according to the difference;
The control signal generated by said control signal generating circuit, wherein a signal level of the feedback modulated wave signal extracted by the extraction circuit is variably controlled, the demodulator feedback modulated wave signal whose signal level is variably controlled A wireless transmitter comprising: a variable control circuit that inputs the signal to the wireless transmitter. A modulation circuit that modulates a carrier wave signal with a transmission baseband signal and outputs a modulated wave signal ;
Variable gain control type power that can selectively output multiple transmit power levels and selectively set transmit power levels according to the system specifications required from these transmit power levels An amplifier, and a power amplification circuit that amplifies and outputs the modulated wave signal output from the modulation circuit by the variable gain control type power amplifier;
Taking out a part of the modulated wave signal output from the power amplifier circuit as a feedback modulated wave signal, the demodulated signal the feedback modulated wave signal is demodulated by the demodulator by the carrier to the transmission baseband signal A non-linear distortion compensation circuit that compensates for non-linear distortion of the power amplifier by negative feedback,
The nonlinear distortion compensation circuit includes:
A circuit for extracting a part of the modulated wave signal output from the power amplifier circuit as a feedback modulated wave signal;
By the correction value corresponding to the variable gain-controlled transmission power level set in the power amplifier, by performing the correction to the signal level of the feedback modulated wave signal extracted by said extraction circuit, the feedback modulated wave A correction circuit for correcting the signal level of the signal so that the signal level is constant regardless of which transmission power level is set in the variable gain control type power amplifier;
A control signal generation circuit that compares the signal level of the feedback modulated wave signal corrected by the correction circuit with a preset reference value and generates a control signal according to the difference;
The control signal generated by said control signal generating circuit, wherein a signal level of the feedback modulated wave signal extracted by the extraction circuit is variably controlled, the demodulator feedback modulated wave signal whose signal level is variably controlled A wireless transmitter comprising: a variable control circuit that inputs the signal to the wireless transmitter. The correction circuit has a correction table storing a correction value in association with each of a plurality of transmission power levels according to the specification of the system to be applied, and the transmission power corresponding to the required specification from the correction table The correction value corresponding to the level is selectively read out, and the read out correction value is added to or subtracted from the signal level of the feedback modulated signal extracted by the extraction circuit. 2. The wireless transmitter according to 2.

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