JP2007311887A - Amplitude variable device and characteristic correction method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an amplitude variable device capable of decreasing an error between a desired output setting value and an actual output signal level while improving the S/N of an analog output signal and to provide a characteristic correction method thereof. <P>SOLUTION: The amplitude variable device including two D/A converters 1, 2 is provided with: a first multiplier means 3 for multiplying a first coefficient by a digital signal; the first D/A converter 1 for converting the product into an analog signal; a second multiplier means 4 for multiplying a second coefficient by the digital signal; the second D/A converter 2 for converting the product into an analog signal; an output means 5 that outputs a sum of both the analog signal from the first D/A converter and the analog signal from the second D/A converter or a difference between the analog signals as an analog signal; and a correction multiplication means 12 that multiplies a correction coefficient obtained on the basis of a value of the analog output signal under a prescribed setting condition by the digital input signal led to one of the first and second multiplication means 3, 4. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an amplitude variable device and a characteristic correction method thereof.

  For example, a sound reproducing device that reproduces an audio signal from a digital signal or digital data generally has a function of adjusting the amplitude of the output audio signal. One such mechanism is a digital volume.

  In such a digital volume, a coefficient unit provided in the preceding stage of the DA converter multiplies the digital data (digital signal) by a coefficient, and the DA converter converts the digital data after the multiplication into DA (Digital-to-Digital). -Analog) Convert and output the converted analog signal. As a result, the amplitude of the audio signal (that is, the digital value) is reduced in the digital signal region, and as a result, the amplitude of the output analog signal is also reduced (see, for example, Patent Document 1).

  Normally, in such a digital volume, when the volume is maximum, the digital input signal is directly DA-converted and the converted analog signal is output as it is. On the other hand, when the volume is not maximum (when the volume is reduced), a digital signal multiplied by a coefficient of 0 or more and 1 or less is DA-converted, and the converted analog signal is output as it is. In other words, when the volume is maximum, the amount of attenuation at the digital volume is zero, and when the volume is not maximum, the amplitude of the analog signal is attenuated compared to the maximum value by the amount of attenuation according to the coefficient value at the time of multiplication. To do.

JP 2000-138585 A (FIG. 2 etc.)

  However, when the resolution of the digital signal and the resolution of the DA converter are approximately the same, the resolution of the attenuated digital signal input to the DA converter is reduced, so the digital signal is not attenuated. The distortion rate is worse than that. In particular, in a device with a wide volume adjustment range, during normal playback, playback is often performed at a volume attenuated from the maximum value, and degradation of sound quality in a normal use state becomes a problem.

  In order to solve this problem, for example, an apparatus shown in FIG. 4 can be considered. The apparatus shown in FIG. 4 has two DA converters 101 and 102. Then, one DA converter 101 receives the input signal as it is, and the other DA converter 102 receives the signal obtained by multiplying the input signal by the coefficient by the coefficient multiplier 103. The two analog signals output from the DA converters 101 and 102 are input to the adder 104 in opposite phases. Then, the adder 104 calculates the sum of the two signals and outputs it as an analog output signal. In the adder 104, the sum of the signals having opposite phases is calculated, so that the analog output signal is attenuated according to the coefficient value of the coefficient unit 103. The coefficient value of the coefficient unit 103 may be determined according to the output set value of the analog output signal. By using the two DA converters 101 and 102 in this way, the level of the signal input to each DA converter does not need to be attenuated so much, so that when the amplitude is varied in the digital signal domain, the analog output signal It becomes possible to suppress degradation of the.

  In the case of the above-described apparatus, when the variation in the input / output characteristics of the two DA converters 101 and 102 is relatively small, the error between the output set value and the actual output signal level is small, but the variation in the input / output characteristics is relatively small. When it is large, an error between the output set value and the actual output signal level becomes large. FIG. 5 shows an output set value and an actual output signal level when there is no variation in the input / output characteristics of the two DA converters 101 and 102, when the variation is +0.5 dB, and when the variation is −0.5 dB. FIG. As shown in FIG. 5, when the input / output characteristics of the DA converters 101 and 102 have a relatively large variation, the linearity between the desired output setting value and the actual output signal level is caused by the variation. Worsens and the error between them increases. In particular, the linearity deteriorates as the output setting value is smaller.

  The present invention has been made in view of the above problems, and an amplitude that can reduce an error between a desired output setting value and an actual output signal level while improving the S / N ratio of an analog output signal. An object is to obtain a variable device and a characteristic correction method thereof.

  In order to solve the above problems, the present invention is configured as follows.

  One of the amplitude variable devices according to the present invention is a first multiplication means for multiplying a digital input signal by a first coefficient, and a first for converting the digital input signal after being multiplied by the first coefficient to an analog signal. A DA converter, second multiplying means for multiplying the digital input signal by a second coefficient, a second DA converter for converting the digital input signal after being multiplied by the second coefficient to an analog signal, An output means for outputting the sum of the analog signal from the first DA converter and the analog signal from the second DA converter or the difference between one and the other as an analog output signal; and analog output under a predetermined setting condition Correction multiplier means for multiplying a digital input signal to one of the first multiplier means and the second multiplier means by a correction coefficient obtained based on the value of the signal.

  One of the amplitude variable devices according to the present invention is a first multiplication means for multiplying a digital input signal by a first coefficient, and a first for converting the digital input signal after being multiplied by the first coefficient to an analog signal. A DA converter, second multiplying means for multiplying the digital input signal by a second coefficient, a second DA converter for converting the digital input signal after being multiplied by the second coefficient to an analog signal, An output means for synthesizing the analog signal from the second DA converter in reverse phase with the analog signal from the first DA converter, and outputting the synthesized signal as an analog output signal; and under predetermined setting conditions Correction multiplication means for multiplying a digital input signal to either one of the first multiplication means and the second multiplication means by a correction coefficient obtained based on the value of the analog output signal.

  In addition to the amplitude variable device described above, the amplitude variable device according to the present invention may be configured as follows. That is, in this case, the correction coefficient is a value obtained from the first value of the analog output signal under the first setting condition and the second value of the analog output signal under the second setting condition.

  In addition to the amplitude variable device described above, the amplitude variable device according to the present invention may be configured as follows. In other words, in this case, the correction multiplication means applies to the digital input signal input to either the first multiplication means or the second multiplication means selected based on the first value and the second value. Only multiply by the correction factor.

  In addition to the amplitude variable device described above, the amplitude variable device according to the present invention may be configured as follows. That is, in this case, the correction coefficient is a value obtained from the maximum value of the analog output signal and the minimum value of the analog output signal when the amplitude of the analog signal by the first and second DA converters is maximized. The

  In addition to the amplitude variable device described above, the amplitude variable device according to the present invention may be configured as follows. In other words, in this case, the correction coefficient is calculated from the value of the analog output signal when the first coefficient is zero and the value of the analog output signal when the second coefficient is zero for the same digital input signal. The obtained value.

  In addition to the amplitude variable device described above, the amplitude variable device according to the present invention may be configured as follows. That is, in this case, the amplitude variable device includes a correction coefficient calculation unit that calculates a correction coefficient based on the value of the analog output signal and sets the correction coefficient in the correction multiplication unit.

  One of the characteristic correction methods according to the present invention is a first multiplication means for multiplying a digital input signal by a first coefficient, and a first for converting the digital input signal after being multiplied by the first coefficient to an analog signal. A DA converter, second multiplying means for multiplying the digital input signal by a second coefficient, a second DA converter for converting the digital input signal after being multiplied by the second coefficient to an analog signal, A characteristic correcting method for an amplitude variable device comprising: an output means for outputting a sum of both an analog signal from a first DA converter and an analog signal from a second DA converter or a difference between one and the other as an analog output signal. The digital input signal to one of the first multiplier and the second multiplier is multiplied by a correction coefficient obtained based on the value of the analog output signal under a certain condition. .

  One of the characteristic correction methods according to the present invention is a first multiplication means for multiplying a digital input signal by a first coefficient, and a first for converting the digital input signal after being multiplied by the first coefficient to an analog signal. A DA converter, second multiplying means for multiplying the digital input signal by a second coefficient, a second DA converter for converting the digital input signal after being multiplied by the second coefficient to an analog signal, Characteristics of an amplitude variable apparatus comprising output means for synthesizing an analog signal from a second DA converter in reverse phase with an analog signal from a first DA converter and outputting the synthesized signal as an analog output signal A correction method that multiplies a digital input signal to one of the first multiplication means and the second multiplication means by a correction coefficient obtained based on the value of the analog output signal under a certain condition. Is.

  According to the present invention, it is possible to reduce an error between a desired output setting value and an actual output signal level while improving the S / N ratio of the analog output signal.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Embodiment 1 FIG.
1 and 2 are block diagrams showing the configuration of the amplitude variable device according to Embodiment 1 of the present invention. 1 and 2, a DA converter (DAC) 1 is a first DA converter that converts a digital input signal after being multiplied by a coefficient by a coefficient unit 3 into an analog signal. The DA converter (DAC) 2 is a second DA converter that converts the digital input signal after being multiplied by the coefficient by the coefficient unit 4 into an analog signal. The resolution of the DA converters 1 and 2 may be the same as the resolution of the digital input signal, or may be higher than the resolution of the digital input signal.

  The coefficient units 3 and 4 are circuits for multiplying the digital signal by the positive side coefficient Ap as the first coefficient and the negative side coefficient An as the second coefficient, respectively. The positive electrode side coefficient Ap and the negative electrode side coefficient An are each set to a value of −1 or more and 1 or less. The coefficient units 3 and 4 each have a storage unit such as a multiplier and a memory for storing coefficient data. The coefficient units 3 and 4 constitute an output level setting unit 11. The control circuit 21 is a circuit that sets the coefficient value in each of the coefficient units 3 and 4 in accordance with the output set value of the analog output signal.

  The synthesizer 5 is a circuit that functions as output means for subtracting the analog signal from the DA converter 2 from the analog signal from the DA converter 1 and outputting the calculation result as an analog output signal.

  The output error correction unit 12 is provided in the preceding stage of the output level setting unit 11, and calculates a correction coefficient obtained based on the value of the analog output signal under a certain condition, either the coefficient unit 3 or the coefficient unit 4. It is a circuit that functions as a correction multiplication means for multiplying the digital input signal to. When the digital input signal to the coefficient unit 3 is multiplied by the correction coefficient chATT, a coefficient unit 6 for multiplying the correction coefficient chATT having a value greater than 0 and less than 1 is provided as shown in FIG. On the other hand, when the digital input signal to the coefficient unit 4 is multiplied by the correction coefficient chATT, a coefficient unit 7 for multiplying the correction coefficient chATT having a value greater than 0 and less than 1 is provided as shown in FIG. It is done.

  Here, the value of the correction coefficient chATT and which of the coefficient unit 6 and the coefficient unit 7 are provided will be described.

  In a state where the output error correction unit 12 is not provided (when the coefficient units 6 and 7 are not provided, that is, when the value of the correction coefficient chATT is 1), a standing wave such as a sine wave having a predetermined frequency is input as a digital input signal. .

  As the first setting condition, the output voltage of the DA converter 1 is set to the maximum positive value, the output voltage of the DA converter 2 is set to the maximum negative value, the analog output signal is set to the maximum value, and the analog output at that time is output. The voltage value Vmax of the signal is measured. Vmax is a steady value such as an effective value, a peak value, or an average value, and a voltmeter, a noise meter, or the like may be used for the measurement.

  Next, as the second setting condition, the output voltage of the DA converter 1 is set to the maximum positive value, the output voltage of the DA converter 2 is set to the maximum positive value, and the analog output signal is set to the minimum value. The output signal value Vmin is measured.

  The value of the correction coefficient chATT is calculated from these voltage values Vmax and Vmin.

  When the maximum output voltage of the DA converters 1 and 2 is V, and the error of the output voltage of the coefficient unit 3 with respect to the output voltage of the coefficient unit 4 is α, equations (1) and (2) are established.

  The correction coefficient chATT for canceling the error voltage α is calculated according to the equation (3).

  chATT = 1- (α / V) (3)

  Then, when the output set value of the analog output signal (that is, the attenuation amount in the amplitude variable device) is set to a value that does not exceed the correction coefficient chATT and is closest to the correction coefficient chATT, the measured analog output signal When the value is larger than the output set value (that is, when the attenuation is small), a coefficient unit 6 having a correction coefficient chATT is provided in front of the positive-side coefficient unit 3, and the measured analog output signal value is output. When the value is smaller than the set value (that is, when the attenuation is large), a coefficient unit 7 having a correction coefficient chATT is provided in front of the negative-side coefficient unit 4.

  Next, the operation of the above apparatus will be described.

  As shown in FIG. 1, when a correction coefficient unit 6 is provided in front of the coefficient unit 3, the digital input signal is multiplied by the correction coefficient chATT by the coefficient unit 6 and the positive coefficient Ap is multiplied by the coefficient unit 3. Then, the calculated digital input signal is input to the DA converter 1. Also, the digital input signal is multiplied by the negative-side coefficient An by the coefficient unit 4, and the calculated digital input signal is input to the DA converter 2. Then, analog signals are supplied from the DA converters 1 and 2 to the combiner 5 respectively. The synthesizer 5 outputs a signal obtained by subtracting the analog signal from the DA converter 2 from the analog signal from the DA converter 1 as an output signal.

  On the other hand, as shown in FIG. 2, when the correction coefficient unit 7 is provided in the preceding stage of the coefficient unit 4, the correction coefficient chATT is applied to the digital input signal by the coefficient unit 7, and the negative side coefficient An is processed by the coefficient unit 4. And the digital input signal after the calculation is input to the DA converter 2. The digital input signal is multiplied by the positive coefficient Ap by the coefficient unit 3, and the calculated digital input signal is input to the DA converter 1. Then, analog signals are supplied from the DA converters 1 and 2 to the combiner 5 respectively. The synthesizer 5 outputs a signal obtained by subtracting the analog signal from the DA converter 2 from the analog signal from the DA converter 1 as an output signal.

  In any of the above cases, the error in the output voltage due to the variation in the characteristics of the DA converter 1 and the DA converter 2 is canceled out by the correction coefficient chATT, so that the error in the value of the analog output signal from the output set value Becomes smaller.

  As described above, according to the first embodiment, the output error correction unit 12 as the correction multiplying unit calculates the correction coefficient obtained based on the value of the analog output signal under the predetermined setting condition as the coefficient multiplier 3. And the digital input signal to one of the coefficient units 4 is multiplied. As a result, the output level setting unit 11 does not need to reduce the amplitudes of the two digital signals more than necessary in order to reduce the influence of variations in the DA converters 1 and 2, and the S / S of the analog output signal after DA conversion can be reduced. Since the N ratio can be improved and the influence of the variation of the DA converters 1 and 2 is reduced, the error between the desired output set value and the actual output signal level can be reduced.

Embodiment 2. FIG.
In the second embodiment of the present invention, the value of the correction coefficient chATT is changed. In the second embodiment, the output voltage on the positive electrode side and the output voltage on the negative electrode side are measured individually, and the value of the correction coefficient chATT obtained from these output voltage values is used.

  First, a standing wave similar to that of the first embodiment is input as a digital input signal, and as a first setting condition, the value of the negative side coefficient An of the coefficient unit 4 is set to zero, and the voltage value Vposi of the analog output signal is set. taking measurement. Next, as a second setting condition, the value of the positive coefficient Ap of the coefficient unit 3 is set to zero, and the voltage value Vnega of the analog output signal is measured.

  The value of the correction coefficient chATT is calculated from these voltage values Vposi and Vnega.

  Assuming that the difference between these voltage values Vposi and Vnega is Vdiff (Vdiff = Vposi−Vnega), when Vdiff is positive, Equation (4) holds for the error voltage α between the positive electrode side and the negative electrode side. When Vdiff is negative, Expression (5) is established.

  α / V = Vdiff / Vposi (4)

  α / V = −Vdiff / Vnega (5)

  Based on Equation (4) or Equation (5) and Equation (3), the value of the correction coefficient chATT is calculated.

  When Vdiff is positive, a coefficient unit 6 for correction coefficient chATT is provided, and when Vdiff is negative, a coefficient unit 7 for correction coefficient chATT is provided.

  As described above, according to the second embodiment, the output error correction unit 12 calculates the correction coefficient obtained based on the value of the analog output signal under a predetermined setting condition by the coefficient multiplier 3 and the coefficient multiplier 4. Multiply the digital input signal to either one. As a result, the output level setting unit 11 does not need to reduce the amplitude of the digital signal more than necessary, so that the S / N ratio of the analog output signal after DA conversion can be improved, and the DA converters 1 and 2 can be made. Therefore, the error between the desired output set value and the actual output signal level can be reduced.

Embodiment 3 FIG.
In the third embodiment of the present invention, a pulse signal is input as a digital input signal, and which of the correction coefficient units 6 and 7 is provided based on the polarity (positive or negative) of Vmin at that time. Judgment is made. Other configurations are the same as those in the first embodiment.

  When Vmin when a pulse signal is input is positive, a coefficient unit 6 having a correction coefficient chATT is provided on the positive electrode side. When Vmin at that time is negative, a correction coefficient is provided on the negative electrode side. A coefficient unit 7 having a chATT is provided. The value of the correction coefficient chATT may be calculated in the same manner as in the first embodiment.

  Whether the voltage of the analog output signal when a pulse signal is input is positive or negative may be measured by an oscilloscope, peak value detection, or the like.

Embodiment 4 FIG.
The amplitude variable apparatus according to the fourth embodiment of the present invention incorporates a processing unit that measures output variation between the DA converter 1 and the DA converter 2 and sets a correction coefficient chATT based on the measured output variation.

  FIG. 3 is a block diagram showing a configuration of an amplitude variable device according to Embodiment 4 of the present invention. In FIG. 3, an AD converter (ADC) 31 is an AD converter that converts an output of the synthesizer 5, that is, an analog output signal into a digital signal.

  In addition, the test signal generator 41 generates a standing wave that is a test signal used when determining the correction coefficient chATT. The input switching unit 42 selects and outputs either the output signal of the test signal generation unit 41 or the digital input signal. The correction coefficient calculation unit 43 is a processing unit that calculates the value of the correction coefficient chATT based on the value of the analog output signal in accordance with the method in the first or second embodiment. The control unit 44 is a processing unit that controls each unit in the digital signal area. In the amplitude variable apparatus according to the fourth embodiment, the digital signal region portion excluding the DA converters 1 and 2 and the AD converter 31 is realized by a digital signal processor (DSP) 51.

  The other components in FIG. 3 are the same as those in the first embodiment (FIGS. 1 and 2), and a description thereof will be omitted.

  Next, the operation of the above apparatus will be described.

  In the correction coefficient setting mode, the control unit 44 controls the input switching unit 42 to supply the test signal of the test signal generation unit 41 to the output error correction unit 12, and also controls the correction coefficient calculation unit 43, The coefficient values of the coefficient units 6 and 7 of the output error correction unit 12 are each set to 1, and predetermined coefficient values are set to the coefficient units 3 and 4 of the output setting unit 11.

  When calculating the correction coefficient chATT in the same manner as in the first embodiment, as a first setting condition, the control unit 44 sets the coefficient of the coefficient unit 3 to a predetermined positive value and sets the coefficient value of the coefficient unit 4 to a negative value. The correction coefficient calculation unit 43 measures the voltage value Vmax of the analog output signal at that time. Next, as a second setting condition, the control unit 44 sets the coefficient of the coefficient unit 3 as a positive predetermined value, sets the coefficient value of the coefficient unit 4 as a positive predetermined value, and the correction coefficient calculation unit 43 performs The voltage value Vmin of the analog output signal is measured. Then, the correction coefficient calculation unit 43 calculates the value of the correction coefficient chATT based on the above equations (2) and (3).

  Then, the control unit 44 sets the coefficient values of the coefficient multipliers 3 and 4 so that the output set value of the analog output signal does not exceed the correction coefficient chATT and is closest to the correction coefficient chATT, and the correction coefficient The calculation unit 43 measures the value of the analog output signal at that time. When the value of the analog output signal is larger than the output set value (that is, when the attenuation is small), the correction coefficient calculation unit 43 sets the coefficient value of the coefficient unit 6 as the correction coefficient chATT value, and The numerical value is 1. On the other hand, when the value of the analog output signal is smaller than the output set value (that is, when the attenuation is large), the correction coefficient calculation unit 43 sets the coefficient value of the coefficient unit 7 as the value of the correction coefficient chATT, and the coefficient unit 6 The coefficient value of is set to 1.

  On the other hand, when the correction coefficient chATT is calculated in the same manner as in the second embodiment, as a first setting condition, the control unit 44 sets the coefficient of the coefficient unit 3 to a predetermined positive value and sets the coefficient value of the coefficient unit 4 The correction coefficient calculation unit 43 measures the voltage value Vposi of the analog output signal at that time. Next, as a second setting condition, the control unit 44 sets the coefficient of the coefficient unit 3 to zero, sets the coefficient value of the coefficient unit 4 to a predetermined positive value, and the correction coefficient calculation unit 43 outputs the analog output signal at that time. The voltage value Vnega is measured. Then, the correction coefficient calculation unit 43 calculates the value of the correction coefficient chATT based on the above equations (3) to (5). Further, the correction coefficient calculation unit 43 calculates Vdiff, and based on the polarity, sets one coefficient value of the coefficient units 6 and 7 as the correction coefficient chATT value and sets the other coefficient value to 1.

  In the calculation execution mode after completion of the correction coefficient setting mode, the control unit 44 controls the input switching unit 42 to supply the output error correction unit 12 with a digital input signal. Therefore, the digital input signal is supplied to the output level setting unit 11 after correction processing by the output error correction unit 12, converted into an analog signal by the DA converters 1 and 2, and output from the synthesizer 5 as an analog output signal. . At that time, the control unit 44 operates in the same manner as the control circuit 21 of the first and second embodiments, and sets coefficient values corresponding to the output set values in the coefficient multipliers 3 and 4.

  As described above, according to the fourth embodiment, the correction coefficient calculation unit 43 as the correction coefficient calculation unit calculates the correction coefficient based on the value of the analog output signal and sets it in the output error correction unit 12. As a result, the amplitude variable device autonomously corrects the dispersion of the DA converters 1 and 2, so that an external measuring device is not necessary and the correction coefficient setting step can be omitted.

Embodiment 5 FIG.
The amplitude variable apparatus according to the fifth embodiment of the present invention is configured to perform output setting by the method previously proposed in Japanese Patent Application No. 2006-50676.

  Therefore, in the fifth embodiment, the control circuit 21 determines the positive-side coefficient Ap and the negative electrode corresponding to the output set value based on the correspondence set for each of the predetermined number of regions related to the output set value of the analog output signal. The value of the side coefficient An is determined.

  The control circuit 21 causes the coefficient units 3 and 4 to store digital data of coefficient values. When the analog output signal is attenuated, the control circuit 21 specifies an output set value (that is, an attenuation factor) of the analog output signal corresponding to an operation amount of a volume operation unit (not shown), for example, and according to the output set value The coefficient values are set in the coefficient multipliers 3 and 4, respectively.

  At that time, the output set value of the analog output signal is classified into a predetermined number (for example, 6) regions, and the positive-side coefficient Ap corresponding to the output set value based on the corresponding relationship that differs depending on the corresponding region and The value of the negative electrode side coefficient An is specified.

  Note that other configurations and operations of the amplitude variable apparatus according to the fifth embodiment are the same as those in any of the first to fourth embodiments, and thus the description thereof is omitted.

  As described above, according to the fifth embodiment, the output error correction unit 12 reduces the influence of the variation of the DA converters 1 and 2 to reduce the amplitude of the digital signal input to the DA converters 1 and 2. Since it is not necessary to make it small, the S / N ratio of the analog output signal can be improved. For example, when the variation in the output voltage of the DA converters 1 and 2 is 0.5 dB, according to the method of Japanese Patent Application No. 2006-50676, the output voltage of one DA converter is changed every time the output set value is lowered by 20 dB. Although it is set lower by 10 dB, in the amplitude variable device according to the fifth embodiment, every time the output set value decreases by 60 dB, the output voltage of one DA converter may be decreased by 10 dB. For this reason, when the variable width of the output set value is 80 dB, the output of one DA converter is set to a maximum of 30 dB lower, but in the amplitude variable device according to the fifth embodiment, it may be set to a lower 10 dB.

Embodiment 6 FIG.
The amplitude variable apparatus according to the sixth embodiment of the present invention is configured to perform output setting by the method previously proposed in Japanese Patent Application No. 2006-50684.

  In the sixth embodiment, the control circuit 21 determines the positive-side coefficient Ap and the negative-side coefficient An corresponding to the output set value based on the ratio set for each of the predetermined number of regions related to the output set value of the analog output signal. Determine the value of.

  The output set value of the analog output signal is classified into a predetermined number (for example, 4) regions, and based on the corresponding relationship that differs depending on the corresponding region, the positive side coefficient Ap and the negative side coefficient corresponding to the output set value The value of An is specified.

  In addition, since the other structure and operation | movement of an amplitude variable apparatus which concern on Embodiment 6 are the same as that of any of Embodiment 1-4, the description is abbreviate | omitted.

  As described above, according to the sixth embodiment, the output error correction unit 12 reduces the influence of the variation of the DA converters 1 and 2, thereby reducing the amplitude of the digital signal input to the DA converters 1 and 2. Since it is not necessary to make it small, the S / N ratio of the analog output signal can be improved.

  Each embodiment described above is a preferred example of the present invention, but the present invention is not limited to these, and various modifications and changes can be made without departing from the scope of the present invention. It is.

  For example, in each of the above embodiments, the output error correction unit 12 is provided before the output level setting unit 11, but may be provided between the output level setting unit 11 and the DA converters 1 and 2. Good.

  Further, in the first embodiment, both the coefficient units 6 and 7 are provided in the output error correction unit 12, and one coefficient value of the coefficient units 6 and 7 is set as the correction coefficient value, and the other coefficient value is set as 1. You may do it.

  In each of the above embodiments, the output level setting unit 11 and the output error correction unit 12 are provided separately. However, the output level setting unit 11 multiplies the correction coefficient chATT together with the level setting coefficient. May be. In that case, the coefficient units 6 and 7 of the output error correction unit 12 are not necessary.

  In each of the above embodiments, up to the previous stage of the synthesizer 5, the positive side and the negative side are in phase, and the synthesizer 5 calculates the difference between them. Instead, the output of the coefficient unit 4 on the negative side is obtained. The sum of both may be calculated by the synthesizer 5 in the reverse phase.

  The present invention is applicable to a volume of a digital audio device, for example.

It is a block diagram which shows the structure of the amplitude variable apparatus which concerns on Embodiment 1 of this invention. It is a block diagram which shows the structure of the amplitude variable apparatus which concerns on Embodiment 1 of this invention. It is a block diagram which shows the structure of the amplitude variable apparatus which concerns on Embodiment 4 of this invention. It is a block diagram which shows an example of an amplitude variable apparatus. It is a figure which shows the correspondence of the output setting value when an input / output characteristic of two DA converters has variation, and the case where there is no variation, and an actual output signal level.

Explanation of symbols

1 DA converter (first DA converter)
2 DA converter (second DA converter)
3 Coefficient multiplier (first multiplication means)
4 Coefficient multiplier (second multiplication means)
5 Synthesizer (output means)
12 Output error correction unit (correction multiplication means)
43 Correction coefficient calculation unit (correction coefficient calculation means)

Claims (9)

First multiplying means for multiplying the digital input signal by a first coefficient;
A first DA converter that converts the digital input signal after being multiplied by the first coefficient into an analog signal;
Second multiplying means for multiplying the digital input signal by a second coefficient;
A second DA converter that converts the digital input signal multiplied by the second coefficient to an analog signal;
Output means for outputting a sum of both of the analog signal from the first DA converter and the analog signal from the second DA converter or a difference between one and the other as an analog output signal;
A correction coefficient obtained based on the value of the analog output signal under a predetermined setting condition is multiplied by the digital input signal to one of the first multiplication means and the second multiplication means. Correction multiplication means;
An amplitude variable device comprising: First multiplying means for multiplying the digital input signal by a first coefficient;
A first DA converter that converts the digital input signal after being multiplied by the first coefficient into an analog signal;
Second multiplying means for multiplying the digital input signal by a second coefficient;
A second DA converter that converts the digital input signal multiplied by the second coefficient to an analog signal;
Output means for synthesizing the analog signal from the second DA converter in reverse phase with the analog signal from the first DA converter, and outputting the synthesized signal as an analog output signal;
A correction coefficient obtained based on the value of the analog output signal under a predetermined setting condition is multiplied by the digital input signal to one of the first multiplication means and the second multiplication means. Correction multiplication means;
An amplitude variable device comprising:   The correction coefficient is a value obtained from a first value of the analog output signal under a first setting condition and a second value of the analog output signal under a second setting condition. The amplitude variable device according to claim 1 or 2.   The correction multiplication unit is configured to output the digital input signal input to one of the first multiplication unit and the second multiplication unit selected based on the first value and the second value. 4. The amplitude variable apparatus according to claim 3, wherein the correction coefficient is multiplied only by the correction coefficient.   The correction coefficient is a value obtained from the maximum value of the analog output signal and the minimum value of the analog output signal when the amplitude of the analog signal by the first and second DA converters is maximized. The amplitude variable device according to claim 3.   The correction coefficient is calculated based on the value of the analog output signal when the first coefficient is zero and the value of the analog output signal when the second coefficient is zero for the same digital input signal. 4. The amplitude variable device according to claim 3, wherein the amplitude variable value is obtained.   The amplitude according to any one of claims 1 to 6, further comprising correction coefficient calculation means for calculating the correction coefficient based on a value of the analog output signal and setting the correction coefficient in the correction multiplication means. Variable device. First multiplying means for multiplying a digital input signal by a first coefficient, a first DA converter for converting the digital input signal after being multiplied by the first coefficient to an analog signal, and the digital input signal A second multiplier for multiplying the second coefficient; a second DA converter for converting the digital input signal after multiplication by the second coefficient to an analog signal; and an analog by the first DA converter. A method for correcting a characteristic of an amplitude variable device comprising: an output means for outputting a sum of both of a signal and an analog signal by the second DA converter or a difference between one and the other as an analog output signal,
Multiplying the digital input signal to one of the first multiplier and the second multiplier by a correction coefficient obtained based on the value of the analog output signal under a certain condition;
The characteristic correction method characterized by this. First multiplying means for multiplying a digital input signal by a first coefficient, a first DA converter for converting the digital input signal after being multiplied by the first coefficient to an analog signal, and the digital input signal A second multiplier for multiplying the second coefficient; a second DA converter for converting the digital input signal after multiplication by the second coefficient to an analog signal; and an analog by the first DA converter. A method for correcting a characteristic of an amplitude variable apparatus comprising: an output unit configured to combine an analog signal from the second DA converter with a reverse phase to a signal and output the combined signal as an analog output signal;
Multiplying the digital input signal to one of the first multiplier and the second multiplier by a correction coefficient obtained based on the value of the analog output signal under a certain condition;
The characteristic correction method characterized by this.

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