JP2007251909A - Signal peak voltage suppressor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a signal peak voltage suppressor which is small and whose power consumption can be reduced without triggering deterioration of modulation accuracy or bit error rate. <P>SOLUTION: Transmission signals are subjected to a hard clipping process and a filtering process in a conventional manner. The original transmission signals are deducted from the signals subjected to these processes and inversely signed signals corresponding to the suppressed ones are taken out. Suppression of the peak voltage is performed by giving a gain to the signals and adding them to the original transmission signals. A ratio between the decrease in the signals after hard clipping from the original transmission signals and the suppressed signals from the original signals after filtering is used or a value which is determined by simulation depending on a cut-off frequency of a low-pass filter used for the filtering process is used as the gain. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a hand apparatus for suppressing a peak amplitude of a transmission signal in a wireless communication apparatus.

  In the wireless communication apparatus, the generated signal is amplified by a power amplifier and transmitted. Since the amplifier consumes a lot of power, it is desired to use the amplifier with higher power utilization efficiency. However, the amplifier can improve the power utilization efficiency as it is used where the output power is large, but has the characteristic that the output is saturated from a certain point. When the amplifier is saturated, the output signal is distorted, the spectrum spreads outside the frequency band of the transmission signal, and becomes an interference wave to other frequencies. It is important to use an amplifier with high efficiency in a limited input voltage range where no distortion occurs.

Therefore, conventionally, a method has been adopted in which the ratio of peak components to the average power of transmission signals (PAPR: Peak Average Per Ratio) is made as small as possible. This is because if the signal having a high average power is amplified while keeping the limited input voltage range of the amplifier, the amplifier can be used with no generation of distortion and high operating efficiency. As a conventional method for suppressing the peak of a transmission signal, a method combining amplitude limitation (hard clipping (HC)) by non-linear processing and filtering (LPF: low-pass filter) has been proposed.

FIG. 13 is a diagram for explaining a conventional peak suppression method.
In the hard clipping process, amplitude restriction is performed on the suppression target value for a transmission signal having an amplitude exceeding the suppression target value. That is, a method of forcibly cutting the amplitude exceeding the suppression target value is adopted. In the filtering process, a component outside the signal frequency band of the transmission signal generated by the hard clipping process is cut. It can be seen that the amplitude of the peak component is smaller than the signal before suppression.

As a method for improving the efficiency of a conventional power amplifier, there is Patent Document 1. Patent Document 1 discloses a technique in which an envelope of a transmission signal is suppressed to a set level or less, band-limited by a filter, modulated, and then amplified by a power amplifier.
Japanese Patent Laid-Open No. 10-178414

  As shown in FIG. 13, in the case of performing peak suppression combining conventional hard clipping and filtering, there is a problem that the peak is restored after passing through the LPF (the amplitude exceeds the suppression target value again).

Therefore, in order to suppress the peak of the signal to a desired amplitude, the following two types of methods have been conventionally employed.
(1) Strict HC treatment assuming peak restoration after passing through LPF, and suppress the peak (2) Repeat the process of (HC + LPF) to suppress the restored peak However, in (1), peak suppression There is a problem that the modulation accuracy with respect to the quantity and the bit error rate characteristic deteriorate greatly. In (2), since the circuit scale becomes large, there is a problem that the power consumption is large and the processing delay is also large.

  An object of the present invention is to provide a signal peak voltage suppressing device that is small in size and can suppress power consumption without causing deterioration of modulation accuracy or bit error rate.

The peak voltage suppressing device of the present invention includes a temporary peak suppressing unit that temporarily suppresses the peak of the amplitude of the signal, and a difference signal acquiring unit that acquires a difference signal between the temporarily suppressed signal and the original signal. ,
Gain means for giving a gain to the difference signal, and final peak suppressing means for finally generating a signal in which the amplitude peak is suppressed by subtracting the difference signal given the gain from the original signal. It is characterized by.

Compared with the prior art, it can provide an excellent peak suppressor with a smaller error vector magnitude (EVM) and bit error rate, with a smaller circuit scale and reduced processing delay.

  In the embodiment of the present invention, a peak suppression component included in a frequency band of a transmission signal is extracted from a transmission signal subjected to HC processing and filtering processing, which is one of conventional peak suppression methods, and gain is given. The signal of the peak suppression component given the gain is subtracted from the transmission signal before peak suppression.

FIG. 1 is a diagram showing a basic configuration diagram of an embodiment of the present invention.
After peak suppression similar to the prior art by processing by the hard clipping unit 10 and the low-pass filter 11, a peak suppression component included in the frequency band of the transmission signal is extracted, and a gain is given to the suppression component to transmit the transmission signal before peak suppression. It becomes the composition added to.

  That is, the signal amplitude of the signal is cut by the suppression target value by the hard clipping unit 10, and the frequency component outside the signal frequency band caused by the discontinuity of the signal caused by the cut is removed by the low-pass filter 11. Thereby, a transmission signal turns into a signal with a low peak height. However, as described with reference to FIG. 13, the peak height returns to the suppression target value or higher due to the filtering by the low-pass filter 11. Therefore, the transmission signal is delayed by the delay unit 12 by the delay time of processing by the hard clipping unit 10 and the low-pass filter 11, and is subtracted from the output from the low-pass filter 11 by the subtractor 14. As a result, a signal having a reverse sign of a component obtained by subtracting the output of the low-pass filter 11 from the original transmission signal (this signal is hereinafter referred to as peak suppression information) is output from the subtractor 14. A predetermined gain is given to the gain multiplier 15. The original transmission signal is delayed by the delay unit 12 and then again delayed by the delay unit 13 and input to the adder 16. The amount of delay in the delay unit 13 is the same as the processing delay time in the gain multiplier 15. In the adder 16, the delayed transmission signal and the output of the gain multiplier 15 are added. Here, the output of the gain multiplier 15 and the output of the delay unit 13 are added at a synchronized timing because the delay amount is adjusted. Further, since the output of the subtracter 14 is obtained by subtracting the delayed transmission signal having a large peak value from the output of the low-pass filter 11 having a small peak value, the adder has a negative value. The calculation at 16 is actually an operation for subtracting the peak suppression information to which gain is given from the transmission signal.

  The diagrams (1) to (6) drawn on the configuration diagram of FIG. 1 schematically show the signal spectrum in the portion immediately below the diagrams (1) to (6) in the configuration diagram. It is a figure. (1) is a transmission signal, which is composed of components in a predetermined frequency band. When this is processed by the hard clipping unit 10, a component outside a predetermined frequency band is generated as shown in (2). When this is removed by the low-pass filter 11, a spectrum as shown in (3) is obtained. The subtracter 14 subtracts (1) from (3), and the peak suppression information (the opposite sign) obtained as a result is (4). In the gain multiplier 15, (4) is obtained by giving a gain to (4). The spectrum of the signal obtained by adding (1) and (5) is (6).

  The gain multiplication unit 15 can be configured with a digital multiplier. Compared to the case where hard clipping processing and low-pass filter processing are repeatedly performed as in the prior art, this configuration requires only one multiplier, and thus the configuration is simplified. In other words, a digital low-pass filter includes many taps and requires multipliers as many as the number of taps. Therefore, providing one low-pass filter in comparison with a single multiplier requires a lot of hardware configurations. Will be introduced.

In the above description, a complex signal having an I component and a Q component is assumed as a transmission signal handled in normal wireless communication. In the following description, what is shown as the amplitude of a signal is a value obtained by calculating √ (I ² + Q ² ) in the case of a complex signal. It should be noted that there is no difference in processing method when dealing with real signals or dealing with complex signals.

FIG. 2 is a diagram for explaining the operation of the basic configuration of the embodiment of the present invention shown in FIG.
FIG. 2 illustrates the state of hard clipping and filtering processing. As shown in FIG. 2A, it can be seen that even if the peak amplitude is limited to the target value by the hard clipping process, the peak is restored by the next filtering process. Here, the hatched portion in FIG. 2A is peak suppression information.

Therefore, as shown in FIG. 2B, if the peak suppression information is gained and subtracted from the original transmission signal (if the peak suppression information subtracted from the transmission signal before suppression is increased), filtering is performed. Peaks restored by processing can be suppressed.

FIG. 3 is a more detailed configuration example of the first embodiment of the present invention having a configuration in which the gain G is adaptively changed in accordance with the peak size.
3, the same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.

  The hard clipping unit 10 outputs the difference value between the peak value of the transmission signal and the suppression target value as the clip amount A. An appropriate delay is given to the clip amount A by the delay unit 20 and is input to the gain generation unit 22. Further, the amplitude of the output of the subtracter 14 is extracted by the amplitude extraction unit 21 and input to the gain generation unit 22 as a value B.

  The gain generation unit 22 calculates and outputs the gain G as (clip amount A) / (value B). The calculated gain G is input to the selector 25 through the limiter 24. The limiter 24 is provided to prevent the apparatus from operating abnormally when the gain G becomes an abnormal value. That is, since the gain G cannot be 1 or less, the lower limit value of the limiter value is 1. The upper limit value should be appropriately set by those skilled in the art. The selector 25 is for creating a window for measuring the timing for giving the gain. That is, the multiplication section determination circuit 23 receives the amplitude value from the amplitude extraction unit 21 and, when the amplitude value becomes equal to or greater than a predetermined value, determines that the timing for multiplying the gain has come, and controls the selector 25 to The gain G from the generation unit 22 is input to the gain multiplication unit 15. If it is not time to multiply the gain G, the selector 25 is made to select the value “1”. As a result, the gain multiplication unit 15 multiplies the output of the subtractor 14 by 1, and the peak suppression information to which no gain is given is input to the adder 16. When the amplitude of the transmission signal is smaller than the suppression target value, the output of the low-pass filter 11 and the delayed transmission signal are the same, so the output of the subtractor 14 is zero. Therefore, the output of the gain multiplication unit 15 is also 0, and the output of the adder 16 is a transmission signal that has not been processed at all.

FIG. 4 is a diagram for explaining how to obtain the gain G in the gain generation unit 22.
Amplitude A (clip amount A) in which the transmission signal before peak suppression exceeds the suppression target value with respect to the peak of the transmission signal exceeding the suppression target value, and difference B between the transmission signal after filtering and the peak before suppression ( Each value B) is acquired. Then, in order to suppress the peak of the signal restored after the filtering process to the suppression target, the gain given to the gain multiplier 15 is set to G = A / B.

  As described above, when the peak suppression information shown in the upper diagram of FIG. 4 exists, the gain G obtained by the method described above is multiplied by the signal of the opposite sign of the peak suppression information. When there is no peak suppression information, the selector 25 selects “1” as the gain. Therefore, the change in the gain value is as shown in the lower diagram of FIG.

FIG. 5 is a diagram for explaining the operation of the multiplication interval determination circuit 23.
The signal shown in FIG. 5 indicates the peak suppression information included in the frequency band of the transmission signal. The amplitude value of the peak suppression information is compared with a threshold value, and the selector 25 is controlled to multiply the gain G for a section where the relationship of “amplitude of peak suppression information> threshold value” is established. The threshold value should be appropriately set by those skilled in the art.

FIG. 6 is a diagram showing a detailed configuration example of the second exemplary embodiment of the present invention.
In FIG. 6, the same components as those of FIG.
The ratio of the clip amount A to the peak value B of the peak suppression information obtained by the amplitude extraction unit 21 is calculated by the divider 30, and 1 is subtracted from the output of the divider 30 in the subtractor 31. The output of the subtractor 31 is latched by the latch 32 and is input to the selector 25 via the limiter 24. In this embodiment, the limiter value of the limiter 24 is a value obtained by subtracting 1 from the limiter value of FIG. The multiplication interval determination circuit 23 operates in the same manner as in FIG. 3, controls the latch 32, and inputs a value obtained by subtracting 1 from the gain value G to the limiter 24. In addition, the multiplication section determination circuit 23 controls the memory 33 to multiply the output of the selector 25 by the window function data. As the window function stored in the memory 33, a window function whose value is smoothly reduced before and after the time direction is used around the peak portion to be multiplied by maximizing the gain value. The window function data may have high-precision data over the multiplication section, or may be used after rough data is interpolated. Further, the window function data may have an asymmetric shape around the peak. Alternatively, the window function may be such that the peak portion is flat and the value suddenly decreases toward the end of the window function.

  The multiplication section determination circuit 23 outputs an appropriate window function value from the memory 33 in accordance with the input timing of the peak suppression information, and the multiplier 34 multiplies (gain value G−1). Unlike the case of FIG. 3, the selector 25 selects either the gain value G−1 or 0. Then, 1 is added by the adder 35, and the gain multiplication unit 15 multiplies the peak suppression information by the gain value. By doing so, the gain value multiplied by the peak suppression information gradually increases and, after reaching the peak, gradually decreases, so that the peak suppression information changes so as to increase rapidly. Can be suppressed. That is, when the gain suppression value is suddenly multiplied by the peak suppression information, the peak suppression information increases discontinuously, and an unnecessary frequency component is included in the output of the adder 16, but the gain value is smooth. Is multiplied by the peak suppression information, generation of unnecessary frequency components due to such discontinuity can be prevented.

The delay unit 36 delays the peak suppression information by a time required for calculating the gain value.
FIG. 7 is a diagram for explaining the effect of the window function.

  When a transmission signal as shown in the upper diagram of FIG. 7 is input, it is necessary to multiply the peak suppression information portion by the gain G. However, as shown in the lower diagram of FIG. By multiplying the window function to be changed, the value of the peak suppression information can be prevented from changing rapidly.

FIG. 8 is a diagram illustrating a configuration example of the third embodiment of the present invention.
In FIG. 8, the same components as those in FIG. 6 are denoted by the same reference numerals, and description thereof is omitted.
FIG. 8 shows an embodiment in which the gain value in the gain multiplier 15 is fixed. It is known that the magnitude of the peak restoration in which the signal peak becomes larger than the hard clipped value in the output of the low-pass filter 11 depends on the value of the cutoff frequency of the low-pass filter 11. The larger the cutoff frequency of the low-pass filter 11 is, the smaller the peak restoration is. Therefore, in the design stage of the apparatus of FIG. 8, the state of peak restoration is examined by simulation or the like, the designer examines in advance how much the gain value should be, and the gain value selected by the designer is gained. The multiplier 15 is set.

FIG. 9 is a diagram illustrating a configuration example of the fourth embodiment of the present invention.
9, the same components as those in FIG. 6 are denoted by the same reference numerals, and description thereof is omitted.
This configuration is effective for a signal having an unnecessary wave outside the desired frequency band, such as an OFDM signal generated using IFFT. In the case of an OFDM signal, since IFFT processing is performed in units of predetermined blocks, a discontinuous signal is generated at a block boundary. Therefore, when generating an OFDM signal, processing such as passing a signal through a low-pass filter or setting the signal amplitude of the discontinuous portion to 0 is performed in order to remove the discontinuous portion. For this reason, a configuration such as a low-pass filter is required in the generation of the transmission signal.

  In the configuration of FIG. 9, a hard clipping process is performed on a transmission signal such as an OFDM signal that does not pass through a low-pass filter or the like to obtain a difference from the transmission signal, and a gain is given to the gain multiplier 15. Thereafter, the difference between the signal after the hard clipping process and the transmission signal given the gain is added to the transmission signal and passed through the low-pass filter 11. Thereby, since the removal of the discontinuous portion of the transmission signal and the removal of the discontinuous portion by hard clipping can be performed at a time, there is an advantage that the configuration for removing the discontinuous portion of the transmission signal can be removed.

  The transmission signal (1) is a signal including a component outside the signal frequency band. In (2), by performing the hard clipping process, the signal further includes a component outside the signal frequency band. By subtracting the transmission signal from this, peak suppression information is obtained (3). A gain is given to (3), and (4) is added to the transmission signal to obtain (5). Finally, components outside the signal band are removed by the low-pass filter 11 to obtain a peak-suppressed signal.

FIG. 10 is a diagram illustrating a configuration example of the fifth embodiment of the present invention.
In this configuration, the signal whose peak is suppressed by the hard clipping and filtering processing is first multiplied by the gain. Then, a signal obtained by multiplying the transmission signal by a value obtained by subtracting 1 from the gain value is subtracted from the output of the gain multiplier 15 to obtain a desired peak-suppressed signal. This operation can be explained as follows. That is, the output signal of the low-pass filter 11 is A, and the transmission signal is A + B. Here, B is peak suppression information. When the gain multiplied by the gain multiplier 15 is G and the gain multiplied by the multiplier 40 is (G-1), the processing in the subtractor 41 is as follows.
A * G- (A + B) (G-1) = A- (G-1) * B = A + B-G * B
It becomes. That is, the peak suppression information B given the gain G is subtracted from the transmission signal A + B. As described above, it can be understood that the configuration of FIG. 10 can achieve the same effect as the configuration of FIG. In FIG. 10, the gain value G shows the case where the ratio between the output of the low-pass filter 11 and the clip amount from the hard clipping unit 10 is used. Of course, a simulation is used from the cutoff frequency of the low-pass filter 11. May be determined.

FIG. 11 is a diagram showing a configuration example of the sixth embodiment of the present invention.
In FIG. 11, the same reference numerals are assigned to the components corresponding to the components in FIG.

In the configuration of FIG. 11, filtering processing and peak suppression component amplification processing are performed in the frequency domain, and the signal is transmitted again to a time signal.
The transmission signal subjected to hard clipping by the hard clipping unit 10 and the transmission signal delayed by the delay unit 12-1 are Fourier-transformed by the FFT units 45-1 and 45-2, respectively, and converted into frequency domain signals. The An unnecessary frequency component removing unit 47 removes components outside the signal frequency band from the signal subjected to the hard clipping process and converted into the frequency domain signal. This is the same as the function of the low-pass filter. By subtracting the delayed transmission signal in the frequency domain from the output of the unnecessary frequency component removing unit 47, peak suppression information with an opposite sign can be obtained. This peak suppression information is multiplied by a gain G, the adder 16 subtracts the peak suppression information from the transmission signal, and the IFFT unit 46 performs inverse Fourier transform on the output of the adder 16 to obtain a time domain signal for transmission. .

11 shows that processing is performed in the frequency domain on the premise of the configuration of FIG. 3, it can be easily conceived by those skilled in the art that the same applies to the configuration of FIG. 10.
FIG. 12 is a diagram illustrating a configuration example of the seventh embodiment of the present invention.

12, components corresponding to the components in FIG. 6 are given the same reference numerals, and description thereof is omitted.
By performing the processing of the embodiment of the present invention a plurality of times, the performance can be further improved. That is, the peak suppression performance is improved by connecting the configurations of the first to sixth embodiments in a plurality of stages (two stages in FIG. 12) in series. In FIG. 12, the configuration of each part is described based on the basic configuration diagram of FIG. 1, but can be applied by arbitrarily combining the configurations of the first to sixth embodiments.

(Appendix 1)
Temporary peak suppression means for temporarily suppressing the amplitude peak of the signal;
Difference signal acquisition means for acquiring a difference signal between the temporarily suppressed signal and the original signal;
Gain means for giving a gain to the difference signal;
A final peak suppressing means for finally generating a signal whose amplitude peak is suppressed by subtracting the difference signal given the gain from the original signal;
A peak voltage suppressing device comprising:

(Appendix 2)
2. The peak voltage suppressing device according to claim 1, wherein the temporary peak suppressing unit includes a hard clipping unit that clips a signal amplitude to a predetermined value.

(Appendix 3)
Furthermore, the peak voltage suppression apparatus of Claim 2 provided with the filter means which performs a filtering process with respect to the output of the said last peak suppression means.

(Appendix 4)
The temporary peak suppression means includes
Hard clipping means for clipping the amplitude of the signal to a predetermined value;
Filter means for filtering the clipped signal;
The peak voltage suppressor according to appendix 1, characterized by comprising:

(Appendix 5)
The peak voltage suppressor according to appendix 3 or 4, wherein the filter means is a low-pass filter.

(Appendix 6)
The peak voltage suppression device according to appendix 5, wherein the gain is set to a value depending on a cutoff frequency of the low-pass filter.

(Appendix 7)
5. The peak voltage suppression device according to appendix 3 or 4, wherein the gain is determined from a ratio of a signal clipping amount and a suppression amount ratio of the filtered signal to the original signal.

(Appendix 8)
The peak voltage suppressor according to appendix 1, wherein the gain is given to the difference signal through a smoothly changing window function.

(Appendix 9)
The peak voltage suppressor according to appendix 1, wherein the gain is given to the difference signal through a limiter that defines an upper limit value and a lower limit value.

(Appendix 10)
The peak voltage suppression device according to appendix 1, wherein the gain is given to the difference signal when the amplitude of the difference signal becomes equal to or greater than a predetermined threshold value.

(Appendix 11)
Temporary peak suppression means for temporarily suppressing the amplitude peak of the signal;
First gain means for providing a gain to the temporarily suppressed signal;
Second gain means for giving the original signal a gain obtained by subtracting 1 from the gain in the first gain means;
Final peak suppression means for finally generating a signal whose amplitude peak is suppressed by subtracting the signal given gain by the second gain means from the signal given gain by the first gain means When,
A peak voltage suppressing device comprising:

(Appendix 12)
The temporary peak suppression means includes
Hard clipping means for clipping the amplitude of the signal to a predetermined value;
Filter means for filtering the clipped signal;
The peak voltage suppressor according to appendix 11, characterized by comprising:

(Appendix 13)
13. The peak voltage suppression device according to appendix 12, wherein the filter means is a low-pass filter.

(Appendix 14)
The peak voltage suppression device according to appendix 13, wherein the gain is set to a value depending on a cutoff frequency of the low-pass filter.

(Appendix 15)
14. The peak voltage suppression apparatus according to appendix 13, wherein the gain is determined from a ratio of a signal clipping amount and a suppression amount ratio of the filtered signal to the original signal.

(Appendix 16)
Fourier transform means for transforming a time domain signal into a frequency domain;
An inverse Fourier transform means for transforming the frequency domain signal into the time domain,
The peak voltage suppression device according to appendix 4 or 12, wherein the processing from the filter unit to the final peak suppression unit is performed in a frequency domain.

(Appendix 17)
A peak voltage suppressor comprising a plurality of the peak voltage suppressors of appendix 1 or 11 connected in series.

(Appendix 18)
Temporarily suppress signal amplitude peaks,
Obtaining a difference signal between the temporarily suppressed signal and the original signal;
Give a gain to the difference signal,
By adding the difference signal given the gain and the original signal, a signal whose amplitude peak is finally suppressed is generated.
The peak voltage suppression method characterized by the above-mentioned.

(Appendix 19)
Temporarily suppress signal amplitude peaks,
Giving a gain to the temporarily suppressed signal;
Giving the original signal a gain obtained by subtracting 1 from the gain in the first gain means;
By subtracting the signal given gain by the second gain means from the signal given gain by the first gain means, a signal whose amplitude peak is finally suppressed is generated.
The peak voltage suppression method characterized by the above-mentioned.

It is a figure which shows the basic block diagram of embodiment of this invention. It is a figure explaining operation | movement of the basic composition of embodiment of this invention of FIG. It is a more detailed configuration example of the first embodiment of the present invention having a configuration in which the gain G is adaptively changed in accordance with the size of a peak. It is a figure explaining how to obtain the gain G in the gain generation unit 22. FIG. 6 is a diagram for explaining the operation of a multiplication interval determination circuit 23. It is a figure which shows the detailed structural example of the 2nd Embodiment of this invention. It is a figure explaining the effect of a window function. It is a figure explaining the structural example of the 3rd Embodiment of this invention. It is a figure explaining the structural example of the 4th Embodiment of this invention. It is a figure explaining the structural example of the 5th Embodiment of this invention. It is a figure explaining the structural example of the 6th Embodiment of this invention. It is a figure explaining the structural example of the 7th Embodiment of this invention. It is a figure explaining the conventional peak suppression method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Hard clipping part 11 Low pass filter 12, 13, 20 Delay device 14, 31 Subtractor 15 Gain multiplication part 16, 35 Adder 21 Amplitude extraction part 22 Gain generation part 23 Multiplication area determination circuit 24 Limiter 25 Selector 30 Divider 32 Latch 33 Memory 34, 40 Multiplier 45-1, 45-2 FFT unit 46 IFFT unit 47 Unnecessary frequency component removing unit

Claims (10)

Temporary peak suppression means for temporarily suppressing the amplitude peak of the signal;
Difference signal acquisition means for acquiring a difference signal between the temporarily suppressed signal and the original signal;
Gain means for giving a gain to the difference signal;
A final peak suppressing means for finally generating a signal whose amplitude peak is suppressed by subtracting the difference signal given the gain from the original signal;
A peak voltage suppressing device comprising:   2. The peak voltage suppressing device according to claim 1, wherein the temporary peak suppressing means comprises hard clipping means for clipping the amplitude of the signal to a predetermined value.   3. The peak voltage suppressing apparatus according to claim 2, further comprising filter means for performing a filtering process on the output of the final peak suppressing means. The temporary peak suppression means includes
Hard clipping means for clipping the amplitude of the signal to a predetermined value;
Filter means for filtering the clipped signal;
The peak voltage suppressor according to claim 1, further comprising:   The peak voltage suppressing apparatus according to claim 3 or 4, wherein the filter means is a low-pass filter.   The peak voltage suppression device according to claim 5, wherein the gain is set to a value depending on a cutoff frequency of the low-pass filter.   5. The peak voltage suppression device according to claim 3, wherein the gain is determined from a ratio of a signal clipping amount and a suppression amount ratio of a signal after filtering processing to an original signal. 6.   The peak voltage suppressor according to claim 1, wherein the gain is given to the difference signal through a smoothly changing window function.   2. The peak voltage suppression device according to claim 1, wherein the gain is given to the difference signal through a limiter that defines an upper limit value and a lower limit value. Temporary peak suppression means for temporarily suppressing the amplitude peak of the signal;
First gain means for providing a gain to the temporarily suppressed signal;
Second gain means for giving the original signal a gain obtained by subtracting 1 from the gain in the first gain means;
Final peak suppression means for finally generating a signal whose amplitude peak is suppressed by subtracting the signal given gain by the second gain means from the signal given gain by the first gain means When,
A peak voltage suppressing device comprising: