JP2007110397A - Transmitter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To keep a transmitting analog output signal constant without being subject to the effect of a gain abnormality on the feedback side, even when the gain abnormality is generated on the feedback side of a gain-control loop. <P>SOLUTION: A detector 19, an A/D converter 20, and a feedback-gain monitor means composed of a comparison offset 21 are fitted to the gain control loop for controlling the gain of the transmitting analog output signal. The feedback-gain monitor means monitors the feedback gain of the gain control loop, that is the gain of a frequency down-converter 12; corrects a gain fluctuator generated in the gain control loop; and operates so as to keep a transmitting output constant by outputting a feedback-gain correction information S7 to a comparison control unit 18, when the generation of the abnormality of the feedback gain is detected. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a transmission apparatus for generating and transmitting an analog transmission output signal in a radio frequency band from an input digital baseband signal.

  In general, a transmission apparatus for wireless communication requires nonlinear distortion correction control for transmission output. As one method of this distortion correction control, a DPD (Digital PreDistortion) method has been proposed (see, for example, Patent Documents 1 and 2). This DPD method is a method of feeding back a transmission analog output signal and distortion of an amplification unit. In this method, components are detected and distortion is corrected by digital processing. The configuration of a conventional transmission apparatus that performs DPD gain control will be described with reference to FIG.

  As shown in FIG. 5, the conventional transmission apparatus includes a DPD unit 1, a digital analog (D / A) conversion unit 4, a frequency up-conversion unit 5, an amplification unit 9, a distribution unit 10, and a frequency. The down conversion unit 12, the analog / digital (A / D) conversion unit 16, the D / A conversion unit 17, and the comparison control unit 58 are configured.

  Further, the frequency up-conversion unit 5 includes a frequency conversion unit 6, a band pass filter (BPF) 7, and a variable attenuator 8. The frequency down-conversion unit 12 includes a frequency conversion unit 13, a band pass filter (BPF) 14, and an amplification unit 15.

  The DPD unit 1 detects a distortion component generated in the amplification unit 9 from the difference between the input baseband signal S1 and the feedback digital signal S8 by a distortion detection control unit (not shown). Then, the DPD unit 1 performs digital processing to give reverse distortion characteristics to the input baseband signal S1 so that the detected distortion component is compensated by an amplitude and phase correction unit (not shown), and transmits the transmitted digital signal. Output as S2.

  The D / A conversion unit 4 converts the transmission digital signal S2 from the DPD unit 1 into an analog signal and inputs the analog signal to the frequency conversion unit 6 of the frequency up-conversion unit 5. The frequency conversion unit 6 converts the analog signal converted by the D / A conversion unit 4 into a radio frequency band signal. The BPF 7 passes only the signal in the transmission frequency band with respect to the signal after the frequency conversion by the frequency conversion unit 6. The variable attenuator 8 attenuates the signal after passing through the BPF 7 based on the control signal from the D / A converter 17 and outputs the attenuated signal. The amplifying unit 9 amplifies the transmission analog output signal from the variable attenuator 8 with a constant gain.

  The distribution unit 10 distributes the transmission analog output signal amplified by the amplification unit 9 into a feedback input analog signal S3 and a signal to the antenna. The frequency conversion unit 13 converts the transmission analog output signal from the distribution unit 10 into a baseband signal. The BPF 14 passes only a certain frequency band with respect to the signal after the frequency conversion by the frequency conversion unit 13. The amplifying unit 15 amplifies the signal after passing through the BPF 14 with a constant gain and outputs it as a feedback analog signal. The A / D converter 16 converts the feedback analog signal amplified by the amplifier 15 into a digital signal and outputs it as a feedback digital signal S8.

  The comparison control unit 58 compares the transmission digital signal S2 output from the DPD unit 1 with the feedback digital signal S8 from the A / D conversion unit 16, and the difference between the transmission digital signal S2 and the feedback digital signal S8. The transmission gain is calculated from Then, the comparison control unit 58 compares the calculated transmission gain with preset transmission reference gain information, and outputs a transmission control signal S6 for correcting transmission.

  The D / A converter 17 D / A converts the transmission control signal S 6 from the comparison controller 58 and outputs it as a control signal for controlling the variable attenuator 8.

  In the conventional transmission device of the DPD system as described above, the digital analog processing is performed based on the distortion component generated in the amplification unit 9, and the transmission analog output signal of the amplification unit 9 is fed back to provide the feedback input analog signal S3. The feedback input analog signal S3 is converted into a digital signal. The difference between the transmission gain information S6 obtained by comparing the transmission digital signal S2 and the feedback digital signal S8 and the transmission reference gain information stored in advance in order to suppress the temperature fluctuation and the gain fluctuation due to the secular change in the transmission analog output signal. A gain control loop for controlling the variable attenuator 8 is applied so as to correct the above. This gain control loop controls the gain of the transmission analog transmission output signal so that the transmission digital signal S2 and the feedback digital signal S8 generated by feeding back the analog transmission output signal have a constant ratio.

However, since this gain control loop also includes a feedback side for converting the feedback input analog signal S3 to the feedback digital signal S8, when a gain abnormality occurs on the feedback side, the comparison control unit 58 is connected to the feedback side analog signal S3. There is a problem that the transmission analog output signal cannot be made constant by performing erroneous gain correction in order to recognize the difference from the transmission digital signal S2 caused by the gain abnormality as an abnormality of the transmission analog output signal. There is also a problem that a gain abnormality on the feedback side cannot be detected.
JP 2005-65211 A JP 2005-151119 A

  The conventional transmission apparatus described above has a problem in that when a gain abnormality occurs on the feedback side, incorrect gain correction is performed and the transmission analog output signal cannot be made constant.

  An object of the present invention is to provide a transmission device capable of making a transmission analog output signal constant without being affected by gain abnormality on the feedback side even when gain abnormality occurs on the feedback side.

In order to achieve the above object, the transmitting apparatus of the present invention detects a distortion component generated in the amplification unit from the difference between the input digital baseband signal and the feedback digital signal, and the detected distortion component is compensated. As described above, a digital predistortion unit that performs digital processing to give reverse distortion characteristics to the baseband signal and outputs it as a transmission digital signal;
A D / A converter for converting a digital signal transmitted from the digital predistortion unit into an analog signal;
A frequency up-conversion unit that converts the analog signal converted by the D / A conversion unit into a signal in a radio frequency band and performs gain control to output the analog signal as an analog transmission output signal;
An amplification unit that amplifies the analog transmission output signal from the frequency up-conversion unit with a constant gain;
In a transmission apparatus comprising: a gain control loop that performs gain control of the transmission analog transmission output signal so that a feedback digital signal generated by feeding back the transmission digital signal and the analog transmission output signal has a constant ratio;
A feedback gain for calculating a feedback gain of the gain control loop, and correcting a difference between the calculated feedback gain and preset feedback reference gain information for transmission control information for controlling a transmission gain of the gain control loop Feedback gain monitoring means for outputting as information is provided.

  According to the present invention, when a gain abnormality occurs on the feedback side of the gain control loop, the feedback gain monitoring means outputs the feedback gain correction information to the comparison control loop. In the comparison control loop, the feedback gain correction Since transmission control information is corrected by information so that transmission gain control does not malfunction, even if a gain abnormality occurs on the feedback side, the transmission analog output signal is made constant without being affected by this gain abnormality. be able to.

In addition, the feedback gain monitoring means,
A detector for detecting a feedback input analog signal input to the gain control loop;
An A / D converter that converts the signal detected by the detector into a feedback input digital signal by performing A / D conversion;
The feedback input digital signal from the A / D converter is compared with the feedback digital signal generated in the gain control loop, and the feedback gain is calculated from the difference between the feedback input digital signal and the feedback digital signal. The calculated feedback gain may be configured with a comparison offset unit that outputs feedback gain correction information for correcting the transmission gain by comparing the calculated feedback gain with preset feedback reference gain information.

Further, the comparison offset portion is
A delay unit that synchronizes the input timing of the feedback input digital signal and the feedback digital signal by delaying the feedback input digital signal by a predetermined time;
A first average processing unit that outputs first average transmission power data obtained by accumulating and averaging feedback input digital signals from the delay unit; and
A second average processing unit that outputs second average transmission power data obtained by accumulating and averaging the input feedback digital signal for a certain period of time;
A comparator that calculates a feedback gain by comparing the first average transmission power data and the second average transmission power data, and outputs the calculated feedback gain as feedback gain information;
A feedback reference gain memory unit for storing a reference value of feedback gain as feedback reference gain information;
A calculation unit that calculates a difference between feedback gain information from the comparator and feedback reference gain information stored in the feedback reference gain information memory unit and outputs the difference as feedback gain correction information; Also good.

Further, the comparison offset unit is
A feedback gain correction information from the computing unit is compared with a preset feedback gain threshold to detect a gain abnormality on the feedback side, and further includes a determination unit that generates an alarm when a gain abnormality is detected. It may be.

  According to the present invention, when a gain abnormality occurs on the feedback side of the gain control loop, a warning is issued from the determination unit to the user, so that the user can know the occurrence of the gain abnormality.

  As described above, according to the present invention, when an abnormality occurs in the gain on the feedback side, the abnormal amount of the gain on the feedback side is detected, and the gain control of the transmission analog output signal controlled by the gain control loop is performed. On the other hand, the effect that the transmission output can be made constant by correcting the gain fluctuation on the feedback side can be obtained.

  Next, embodiments of the present invention will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 is a block diagram showing the configuration of the transmission apparatus according to the first embodiment of the present invention. In FIG. 1, the same components as those in FIG. 5 are denoted by the same reference numerals, and description thereof is omitted.

  As shown in FIG. 1, the transmission apparatus according to the present embodiment includes a DPD unit 1, a digital analog (D / A) conversion unit 4, a frequency up-conversion unit 5, an amplification unit 9, and distribution units 10 and 11. A frequency down-conversion unit 12, an analog / digital (A / D) conversion unit 16, a D / A conversion unit 17, a comparison control unit 18, a detection unit 19, an A / D conversion unit 20, and a comparison offset Part 21.

  The transmission apparatus of the present embodiment is provided with a distributor 11, a detection unit 19, an A / D conversion unit 20, and a comparison offset unit 21 in addition to the conventional transmission apparatus shown in FIG. The comparison control unit 18 is replaced. The transmission apparatus of this embodiment is characterized in that feedback gain monitoring means for monitoring feedback gain is provided for a gain control loop for controlling the gain of the transmission analog output signal. The feedback gain monitoring means includes a detection unit 19, an A / D conversion unit 20, and a comparison offset unit 21.

  The feedback gain monitoring means, which is a characteristic part of the present embodiment, monitors the feedback gain of the gain control loop, that is, the gain of the frequency down-conversion unit 12, and corrects the feedback gain when detecting the occurrence of the feedback gain abnormality. By outputting the information S7 to the comparison control unit 18, an operation for correcting the gain fluctuation generated in the gain control loop and making the transmission output constant is performed.

  Specifically, the feedback gain monitoring means corrects the difference between the calculated feedback gain and the preset feedback reference gain information by correcting the transmission control information S6 for controlling the transmission gain of the gain control loop. Output as information S7.

  Next, each component constituting the transmission apparatus of this embodiment will be described.

  The distribution unit 11 is provided between the distribution unit 10 and the frequency down-conversion unit 12, distributes the feedback input analog signal S <b> 3 from the distribution unit 10, and outputs it to the detection unit 19. The detection unit 19 detects the signal distributed by the distribution unit 11 from the feedback input analog signal S3 input to the frequency down-conversion unit 12. The A / D conversion unit 20 converts the signal detected by the detection unit 19 into a feedback input digital signal S5 by performing A / D conversion.

  The comparison offset unit 21 compares the feedback input digital signal S5 from the A / D conversion unit 20 with the feedback digital signal S8, and calculates the feedback gain from the difference between the feedback input digital signal S5 and the feedback digital signal S8. To do. Then, the comparison offset unit 21 compares the calculated feedback gain with the feedback reference gain information set in advance, and outputs feedback gain correction information S7 for correcting the transmission gain.

  FIG. 2 shows a block diagram as an example of the comparison offset unit 21 constituting the feedback gain monitoring means.

  As shown in FIG. 2, the comparison offset unit 21 includes a delay unit 211, average processing units 212 and 213, a comparator 214, a calculator 215, and a feedback reference gain memory unit 216.

  The delay unit 211 synchronizes the input timings of the feedback input digital signal S5 and the feedback digital signal S8 by delaying the feedback input digital signal S5 for a certain time.

  The average processing unit 212 outputs average transmission power data S21 obtained by accumulating and averaging the feedback input digital signal S5 from the delay unit 211 for an arbitrary period of time.

  The average processing unit 213 outputs average transmission power data S22 obtained by accumulating and averaging the input feedback digital signal S8 for an arbitrary period of time.

  The comparator 214 compares the average transmission power data S21 and the average transmission power data S22 to calculate a feedback gain, and outputs the calculated feedback gain as feedback gain information S23.

  The feedback reference gain memory unit 216 stores a reference value of feedback gain as feedback reference gain information S24. Here, the reference value of the feedback gain indicates the reference value of the feedback gain obtained when the frequency down-conversion unit 12 is normal.

  The arithmetic unit 215 calculates a difference between the feedback gain information S23 from the comparator 214 and the feedback reference gain information S24 stored in the feedback reference gain information memory unit 216, and outputs the difference as feedback gain correction information S7.

  FIG. 3 shows a block diagram of an example of the comparison control unit 18 constituting the gain control loop.

  As shown in FIG. 3, the comparison control unit 18 includes a delay unit 181, average processing units 182 and 183, a comparator 184, arithmetic units 185 and 186, and a transmission reference gain memory unit 187. Yes.

  The delay unit 181 synchronizes the timings of the transmission digital signal S2 and the feedback digital signal S8 by delaying the transmission digital signal S2 for a predetermined time.

  The average processing unit 182 outputs average transmission power data S31 obtained by accumulating and averaging the transmission digital signal S2 from the delay unit 181 for an arbitrary fixed time.

  The average processing unit 183 outputs average transmission power data S32 obtained by accumulating and averaging the input feedback digital signal S8 for an arbitrary period of time.

  The comparator 184 compares the average transmission power data S31 and the average transmission power data S32 to calculate a transmission gain, and inputs the calculated transmission gain as transmission gain information S33.

  The transmission reference gain memory unit 187 stores a transmission gain reference value in the gain control loop as transmission reference gain information S35.

  The calculator 185 calculates a difference between the transmission gain information S33 output from the comparator 184 and the transmission reference gain information S35 stored in the transmission reference gain information memory unit 187, and outputs the difference as transmission gain difference information S34. .

  The computing unit 186 corrects the transmission gain difference information S34 by performing computation on the transmission gain difference information S34 from the computing unit 185 and the feedback gain correction information S7 output from the comparison offset unit 21, thereby performing transmission control. Output as information S6.

  Next, the operation of the transmission apparatus of this embodiment will be described in detail with reference to the drawings.

  In the DPD unit 1, the feedback digital signal S 8 including the nonlinear distortion component of the amplification unit 9 and the baseband signal S 1 are input, and the distortion detection control unit (not shown) calculates a differential signal of the distortion component of the amplification unit 9. A reverse distortion characteristic signal is calculated based on the component difference signal. Then, the DPD unit 1 outputs a transmission digital signal S2 obtained by previously distorting the amplitude and phase of the baseband signal S1 with a signal having an inverse distortion characteristic by an amplitude and phase correction unit (not shown).

  The transmission digital signal S2 is frequency-converted to a radio frequency by the frequency conversion unit 6 of the D / A conversion unit 4 and the frequency up-conversion unit 5, a signal in the transmission frequency band is selected by the band limitation of the BPF 7, and the amplification unit 9 The signal is amplified and transmitted from the antenna through the distributor 10 as a transmission analog output signal.

  The feedback input analog signal S3 is distributed by the distributor 11, is frequency-converted by the frequency down-converter 12 to the baseband signal by the frequency converter 13, and only the baseband signal is selected by the band limitation of the BPF 14. Amplified by the amplifier 15 and converted into a feedback digital signal S8 by the A / D converter 16. Further, the other feedback input analog signal S3 distributed by the distribution unit 11 is detected by means such as envelope detection in the detection unit 19, and converted into a feedback input digital signal S5 by the A / D conversion unit 20.

  Then, the feedback input digital signal S5 and the feedback digital signal S8 are respectively input to the comparison offset unit 21, and the feedback input digital signal S5 is delayed by the delay unit 211 and averaged from the average processing unit 212 as shown in FIG. Output as transmission power data S21. Similarly, the input feedback digital signal S8 is output from the average processing unit 213 as average transmission power data S22. The comparator 214 receives the average transmission power data S21 and the average transmission power data S22.

  The average transmission power data S21 is corrected for the delay amount on the feedback side including the frequency down-conversion unit 12 by the delay unit 211, and synchronized with the input timing of the average transmission power data S22. In the comparator 214, the average transmission power data S21 is converted into a transmission power level based on a conversion table of “average transmission power data versus transmission power level”. On the other hand, the average transmission power data S22 calculated from the feedback digital signal S8 is converted into a transmission power level by the comparator 214 in accordance with a standard in which the amplitude of the digital signal is constant. Then, the comparator 214 compares these transmission power levels to calculate a feedback gain, and outputs the calculated feedback gain as feedback gain information S23. The conversion table of “average transmission power data versus transmission power level” is individually held by the detection unit 19, and an error due to the detection capability of the detection unit 19 is minimized.

  The computing unit 215 compares the feedback gain information S23 with the feedback reference gain information S24 preset in the feedback reference gain memory unit 216, and outputs the difference as feedback gain correction information S7. The feedback gain correction information S7 is output to the comparison control unit 18 constituting the gain control loop.

  In the comparison control unit 18, as shown in FIG. 3, the transmission digital signal S2 and the feedback digital signal S8 are respectively input to the comparison control unit 18, and the transmission digital signal S2 is delayed by the delay unit 181, and the average processing unit 182 Is output as average transmission power data S31. Similarly, the input feedback digital signal S8 is output from the average processing unit 183 as average transmission power data S32.

  The average transmission power data S31 and the average transmission power data S32 are input to the comparator 184. The average transmission power data S31 is corrected by the delay unit 181 until the delay amount is output from the DPD unit 1 and fed back, and is synchronized with the input timing of the average transmission power data S32. In the comparator 184, the amplitude of the digital signal of the average transmission power data S31 and the average transmission power data S32 is converted into a transmission power level according to a certain standard, and is output as transmission gain information S33 as the gain of the gain control loop.

  The computing unit 185 compares the transmission gain information S33 and the transmission reference gain information S35 of the gain control loop preset in the transmission reference gain memory unit 187, and the difference is transmitted to the computing unit 186 as transmission gain difference information S34. Is output. In the calculator 186, the transmission gain difference information S34 is corrected by the feedback gain correction information S7, and is output to the D / A converter 17 as the transmission control information S6.

  The variable attenuator 8 receives the transmission control information S6 of the gain control loop in which the gain abnormality on the feedback side is corrected via the D / A converter 17, and amplifies the transmission analog output signal in which the abnormal gain on the feedback side is corrected Output to 9.

  In the transmission apparatus of the present embodiment, the comparison offset unit 21 calculates a feedback gain from the feedback digital signal S8 and the feedback input digital signal S5, and compares it with preset feedback reference gain information to correct a difference feedback gain. Information S7 is calculated and output to the comparison control unit 18 constituting the gain control loop.

  Then, the comparison control unit 18 to which the feedback gain correction information S7 is input calculates the gain of the gain control loop from the transmission digital signal S2 and the feedback digital signal S8, and the transmission reference gain information of the preset gain control loop and In comparison, difference transmission gain difference information is calculated, and control information S6 obtained by correcting the gain difference of feedback gain correction information S7 is output to variable attenuator 8.

  Therefore, in the transmission apparatus of the present embodiment, the comparison offset unit 21 outputs the feedback gain correction information S7 to the comparison control unit 18 when a gain abnormality occurs on the feedback side, and the comparison control unit 18 performs this feedback gain correction. Since the transmission control information S6 is corrected by the information S7, even when a gain abnormality occurs on the feedback side, the transmission analog output signal can be made constant without being affected by the gain abnormality.

(Second Embodiment)
Next, a transmission apparatus according to the second embodiment of the present invention will be described.

  The transmission apparatus according to the second embodiment of the present invention is obtained by replacing the comparison offset unit 21 with the comparison offset unit 21a illustrated in FIG. 4 in the transmission apparatus according to the first embodiment illustrated in FIG.

  In the present embodiment, the function of the comparison offset unit 21 is expanded with respect to the transmission apparatus of the first embodiment, so that an alarm is transmitted to inform the user of the abnormality on the feedback side.

  The comparison offset unit 21a in the present embodiment has a configuration in which a determination unit 217 is added to the output of the computing unit 215 with respect to the comparison offset unit 21 in the first embodiment shown in FIG.

  The determination unit 217 detects the feedback gain abnormality by comparing the feedback gain correction information S7 from the computing unit 215 with a preset feedback gain threshold, and generates an alarm when the gain abnormality is detected. To do.

  According to the transmission device of the present embodiment, in addition to the effects of the transmission device of the first embodiment described above, the user can know from the alarm that a gain abnormality has occurred on the feedback side.

It is a block diagram which shows the structure of the transmitter of the 1st Embodiment of this invention. It is a block diagram which shows an example of the comparison offset part 21 of FIG. It is a block diagram which shows an example of the comparison control part 18 of FIG. It is a block diagram which shows the structure of the comparison offset part 21a in the transmission apparatus of the 2nd Embodiment of this invention. It is a block diagram which shows the structure of the conventional transmitter.

Explanation of symbols

1 DPD unit 4 D / A conversion unit 5 Frequency up-conversion unit 6 Frequency conversion unit 7 BPF
8 Variable source attenuator 9 Amplifying unit 10, 11 Distribution unit 12 Frequency down-conversion unit 13 Frequency conversion unit 14 BPF
DESCRIPTION OF SYMBOLS 15 Amplification part 16 A / D conversion part 17 D / A conversion part 18 Comparison control part 19 Detection part 20 A / D conversion part 21, 21a Comparison offset part 58 Comparison control part 181 Delay part 182, 183 Average processing part 184 Comparator 185, 186 arithmetic unit 187 transmission reference gain memory unit 211 delay unit 212, 213 average processing unit 214 comparator 215 arithmetic unit 216 feedback reference gain memory unit 217 determination unit S1 baseband signal S2 transmission digital signal S3 feedback input analog signal S5 feedback Input digital signal S6 Transmission control information S7 Feedback gain correction information S8 Feedback digital signal S21, S22 Average transmission power data S23 Feedback gain information S24 Feedback reference gain information S31, S32 Average transmission power data S33 Transmission gain information S34 Transmission gain difference information S35 Transmission Reference gain Broadcast

Claims (4)

The distortion component generated in the amplifying unit is detected from the difference between the input digital baseband signal and the feedback digital signal, and reverse distortion characteristics are applied to the baseband signal so that the detected distortion component is compensated. A digital predistortion unit that performs digital processing and outputs as a transmission digital signal;
A D / A converter for converting a digital signal transmitted from the digital predistortion unit into an analog signal;
A frequency up-conversion unit that converts the analog signal converted by the D / A conversion unit into a signal in a radio frequency band and performs gain control to output the analog signal as an analog transmission output signal;
An amplification unit that amplifies the analog transmission output signal from the frequency up-conversion unit with a constant gain;
In a transmission apparatus comprising: a gain control loop that performs gain control of the transmission analog transmission output signal so that a feedback digital signal generated by feeding back the transmission digital signal and the analog transmission output signal has a constant ratio;
A feedback gain for calculating a feedback gain of the gain control loop, and correcting a difference between the calculated feedback gain and preset feedback reference gain information for transmission control information for controlling a transmission gain of the gain control loop A transmission apparatus comprising feedback gain monitoring means for outputting information. The feedback gain monitoring means is
A detector for detecting a feedback input analog signal input to the gain control loop;
An A / D converter that converts the signal detected by the detector into a feedback input digital signal by performing A / D conversion;
The feedback input digital signal from the A / D converter is compared with the feedback digital signal generated in the gain control loop, and the feedback gain is calculated from the difference between the feedback input digital signal and the feedback digital signal. A comparison offset unit that compares the calculated feedback gain with feedback reference gain information set in advance and outputs feedback gain correction information for correcting the transmission gain;
The transmission device according to claim 1, comprising: The comparison offset portion is
A delay unit that synchronizes the input timing of the feedback input digital signal and the feedback digital signal by delaying the feedback input digital signal by a predetermined time;
A first average processing unit that outputs first average transmission power data obtained by accumulating and averaging feedback input digital signals from the delay unit; and
A second average processing unit that outputs second average transmission power data obtained by accumulating and averaging the input feedback digital signal for a certain period of time;
A comparator that calculates a feedback gain by comparing the first average transmission power data and the second average transmission power data, and outputs the calculated feedback gain as feedback gain information;
A feedback reference gain memory unit for storing a reference value of feedback gain as feedback reference gain information;
A calculator that calculates a difference between feedback gain information from the comparator and feedback reference gain information stored in the feedback reference gain information memory unit and outputs the difference as feedback gain correction information;
The transmission device according to claim 2, comprising: The comparison offset portion is
The feedback gain correction information from the computing unit is further compared with a preset feedback gain threshold to detect a feedback-side gain abnormality, and further includes a determination unit that generates an alarm when a gain abnormality is detected. Item 4. The transmission device according to Item 3.

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