JP3472333B2 - Signal generator and distortion measuring device - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD OF THE INVENTION The present invention relates to the field of signal generators and strain gauges. In this specification, the signal generator includes a sine wave signal generator, an arbitrary function generator, a multi-tone signal generator, a sweep generator and the like.

[0002]

2. Description of the Related Art In the fields of electronic equipment and communication equipment, it is important to produce periodic signals with little distortion.
It is also important to measure the strain of electronic devices such as amplifiers and mixers. Heretofore, various methods of producing a periodic signal by an analog circuit have been considered. However, in the analog circuit system, distortion from oscillators, amplifiers, mixers, etc. is large, and at several hundred MHz or more, it is an inexpensive part of -6
It is difficult to achieve 0 dBc or less. Further, with the development of IC technology, a digital-analog converter (DA converter) that operates at high speed has become easily available. In recent years, a method (Direct Digital Synthesis) of directly generating an arbitrary waveform signal using such a DA converter has also been actively used. Direct Digital below
Synthesis is abbreviated as DDS.

FIG. 11 shows a basic block diagram of a typical DDS signal generator. The basic configuration of the DDS signal generator is the DDS
It comprises a signal source unit 3, a computer 2, and a timing clock generator 11. The DDS signal source section is composed of a RAM 4, a switch 7, a DA converter 8, a buffer amplifier 9 and an address counter 10. In the operation, first, the computer 2 calculates data obtained by digitizing one cycle of a desired output signal waveform, sets the switch 7 to the side b, and writes the calculated waveform data in the RAM. Then switch 7
To a side. The address counter 10 controlled by the timing clock 11 increases the output value by 1 every clock and is input to the address bus 6 of the RAM 4,
The waveform data stored in the AM is read from the data bus 5 and sent to the DA converter 8. DA converter is D
It is composed of an A conversion circuit and a filter. Therefore, the digital data is converted into an analog signal for each timing clock, smoothed, and output through the buffer amplifier 9. Since the address counter is designed to return to its original state at the next clock when one cycle is reached, the signal is periodically output. In the DDS system, the DA converter is the main source of distortion. In the case of a commercially available 12-bit high-speed DA converter, the distortion level is -50 to -60.
It is about dBc. Further, it is difficult to manufacture a high-speed and low-distortion DA converter, and even if it is technically possible, it is economically unfeasible and not generally available on the market. As described above, neither the analog circuit system nor the DDS system cannot produce a high frequency signal with low distortion.

[0004]

OBJECT OF THE INVENTION It is an object of the present invention to provide a method for realizing a low distortion signal generator and a low distortion measuring instrument at low cost.

[0005]

SUMMARY OF THE INVENTION The present invention realizes a low distortion signal generator by adding distortion canceling means to the DDS method. Moreover, a low distortion measuring instrument is also realized by applying this signal generation method.

[0006]

FIG. 1 shows an embodiment of the present invention. Figure 1
Components having the same functions as in 1 are designated by the same reference symbols. As shown in FIG. 1, the present invention comprises a DDS signal source unit 3, a strain sensor unit 13, a feedback control unit 1, and a timing clock generator 11. The DDS signal source unit 3 is composed of a RAM 4, an address counter 10, a DA converter 8, a buffer amplifier 9, and a switch 7, as in FIG. Strain sensor section 1
3 is composed of a buffer amplifier 14 and an analog-digital converter (AD converter) 15. The feedback control unit 1 is composed of a computer 2 and an algorithm for gradually reducing distortion. The diminishing distortion algorithm shows the procedure processed by the computer 2 and is therefore not shown in FIG. The contents will be described later. The thick lines in the figure showing the connections among the computer, the RAM, the AD converter, the DA converter and the address counter are digital signal lines, and one line of the display is composed of one or more connection lines. Therefore, one movable contact portion of the switch 7 also switches one or more connections. Although the switch 7 is a mechanical switch in order to show the operating principle, it is desirable that the actual circuit is a semiconductor switch.

The outline of the operation of this embodiment will be described below. DD
The S signal source unit 3 generates a periodic signal, the strain sensor unit 13 detects the strain, the feedback control unit 1 calculates the waveform data for canceling the strain, and the data in the RAM of the DDS signal source unit 3 is changed. And cancel the strain. The computer 2 of the feedback control unit 1 is R
In addition to calculating the data to be written in the AM and controlling the writing, it also controls other operations and calculates the data.

The details of the operation will be described below. DA
The same clock is supplied from the timing clock generator 11 to the converter 8, the AD converter 15, and the address counter 10, and they operate in synchronization with each other. Note that the clocks do not necessarily have to be the same, but here, the clocks are simplified and described as the same clock. The case of different clocks will be described later. In the operation, first, the computer 2 calculates the digital data for one cycle of the desired output signal waveform using the equation (4) described later, and sets the switch 7 to the side b to write the calculated waveform data in the RAM. . Where DA
When the clock frequency of the converter is f _s and the cycle of the output signal is T, the number N of data is N = T · f _s . The N pieces of data are written in the RAM 4. This data is x
(N); n = 0, 1, 2, ..., N-1. Next, the switch 7 is switched to the a side. Since the address counter 10 increments the output value by one at each clock, the data x (n) of the RAM is sequentially D
It is sent to the A converter. The DA converter, like the prior art,
Since it is composed of a DA conversion circuit and a filter, digital data is converted into an analog signal, smoothed, and output via the buffer amplifier 9. The filter of the DA converter is a low-pass filter that removes frequencies above fs / 2. The address counter is designed to return to 0 at the next clock when it reaches N-1, so that the signal is output periodically.

At the output terminal 12, RAM data x
A signal obtained by analogizing (n) should appear, but in an actual circuit, a signal including distortion generated in an analog circuit including a DA converter appears. An output signal is sent to the strain sensor unit 13 to detect this strain. That is, the output signal is sent to the AD converter 15 via the buffer amplifier 14. The AD converter samples the output waveform with the same clock as the DA converter 8. Hereinafter, the sample value sequence output from the AD converter when the address counter is 0 to N−1 is y (n); n = 0, 1, 2, ..., N−1
Express. The computer 2 calculates data for canceling the strain from the strain component of y (n), switches the switch 7 to b, and updates the data in the RAM. Then, the switch is switched to a and a signal that cancels the distortion is generated. Normal,
The strain is greatly reduced by this single treatment. If the strain is equal to or more than the allowable value, the process of updating the data in the RAM again is repeated to generate a signal and detect the strain.
This process is repeated until the strain falls below the allowable value. Usually, if this process is repeated several times, the distortion will converge to zero. FIG. 2 is a flow chart showing an embodiment of the distortion reduction algorithm of the present invention. In addition to the above processing, the processing described in detail later is also shown.

Next, the method of calculating the data to be written first, which was previously announced, will be described. This calculation method is a preferred embodiment in which the strain can be converged to the allowable value or less with a small number of processing times. There are no special operational restrictions on the data to be written first, so various other examples are possible. First, assume that the system described above has no distortion. Even if there is no distortion, x (n) and y for the transfer function from the DA converter to the AD converter
(N) is not similar. However, since y (n) can be regarded as the output when x (n) is input to a certain linear system, the discrete Fourier transform X (k) and y (n) of x (n) can be obtained.
It can be expressed by the following relation using the discrete Fourier transform Y (k) of (n).

[0011]

[Equation 1]

G (k) is a transfer function from the input of the DA converter to the output of the AD converter. Also, G (N / 2) is f
It was removed from the range of k in order to make the gain zero at a frequency corresponding to s / 2. The discrete Fourier transform X (k)
And Y (k) are defined as follows.

[0013]

[Equation 2]

[0014] Here, the desired signal sequence output from the AD converter is expressed as y _g (n), it obtains a data string to be written from y _g (n) to the RAM in operation. This is the first data string to be written. Expression (1) indicates that if the data string written in the RAM is one in which the influence of the transfer function G (k) is corrected, the signal output from the AD converter becomes a desired output signal. . That is, the discrete Fourier transform of y _g (n) is corrected by G (k), and the inverse Fourier transform is performed on it to obtain a data string to be written in the RAM. That is,

[0015]

[Equation 3]

As shown in the flow chart of FIG. 2, G (k) is measured in advance. Further, G (k) may be an appropriate estimated value. In this case, the convergence speed only slows down.
The inverse discrete Fourier transform is defined as follows.

[0017]

[Equation 4]

The value x of the equation (4) obtained in this way
First write (n) to RAM. The above assumes that the system has no distortion. However, in an actual system, even if the value of expression (4) is written in the RAM, the distortion component exists in the output component. Therefore, an embodiment of a processing method for gradually reducing distortion will be described below. The distortion is the actual output y
It is the difference between (n) and the desired output y _g (n). This is y _d
(N).

[0019]

[Equation 5]

In order to cancel this y _d (n), the RAM data x (n) is modified. That is, y
_d values of RAM, such as (n) is obtained x _d (n) x
The operation subtracted from (n) is applied to the RAM. That is, the distortion can be canceled by rewriting the RAM data x (n) by the operation of the following equation.

[0021]

[Equation 6]

As a result, the first observed strain y _d
Although (n) is greatly reduced, the strain is not completely zero in this single treatment. If the strain is greater than or equal to the allowable value, the diminishing algorithm shown in FIG. 2, that is, the calculation of the updated data (7) in RAM, the writing to the RAM, the signal generation, the strain measurement, and the comparison with the allowable value are repeated. When the strain becomes less than the allowable value, this process ends, but normally when the process is repeated several times, the strain converges to zero. The above is the operation principle of the basic configuration of the low distortion signal source according to the present invention.

An embodiment in which the basic structure is modified and finally an embodiment of the strain measuring device will be described below. In the following figures, components having the same functions as those in FIG. 1 are designated by the same reference symbols. First, in the basic configuration of FIG. 1, if the DA converter does not have sufficient resolution, the DA converter may not produce a fine signal change and may not be able to cancel a small distortion. An example in which this is solved by using a plurality of DA converters will be shown. FIG. 3 shows an example in which two DA converters are used, but the principle is the same when three or more DA converters are used. R in contrast to FIG.
An AM 16, a DA converter 18, an attenuator 19, and an adder 20 are added. With the addition, the number of circuits of the switch 17 is larger than that of the switch 7 of FIG. RA
The M4 and the DA converter 8 are responsible for the upper digits of the waveform data numerical value. Since the RAM 16 and the DA converter 18 are in charge of the lower digits of the waveform data numerical value, the output of the DA converter is the attenuator 1
It is added to the adder via 9. In this way
The resolution of the DA converter can be made fine equivalently. In the processing of gradually reducing the distortion with this configuration, the distortion is gradually reduced as much as possible by only updating the data of the RAM 4 in the upper digit by the processing method described in the basic plan. After that, the distortion that cannot be removed by itself is gradually reduced by the lower digit RAM 16 and the DA converter 18. The present embodiment is characterized in that an inexpensive DA converter is used to obtain sufficient resolution and low distortion can be realized.

In the basic configuration, since the distortion generated by the DA converter is detected by the AD converter, the influence of the distortion generated by the AD converter cannot be eliminated. In order to reduce this effect as much as possible, an AD converter with higher accuracy than the DA converter is used. In addition, as a structural measure, (a) frequency conversion method, (b) filter method, (c) frequency component measurement method,
(D) Strain sensor external method is available. These methods will be described below.

(A) Frequency conversion method FIG. 4 shows an embodiment of the frequency conversion method. The output of the buffer amplifier 14 of the strain sensor unit 13 is the frequency converter 21.
Is converted into a low frequency and input to the AD converter 15. Therefore, the AD converter can operate at a lower speed than the DA converter. Therefore, an AD converter with higher accuracy and lower distortion than the DA converter can be used, and low distortion can be realized. Also,
An inexpensive AD converter can be used. Since the AD converter operates at a lower frequency than the DA converter, the clock of the AD converter is supplied via the frequency divider 22. Fig. 5 shows low speed D
This is a method of generating a high frequency signal using an A converter and an AD converter. The output of the DA converter 8 is converted to a high frequency by the frequency converter 23 and sent to the buffer amplifier 9, and the output of the buffer amplifier 14 is converted to a low frequency by the frequency converter 21 and input to the AD converter 15. It Since the DA converter and the AD converter are low speed, high accuracy and low distortion can be realized at low cost. In the present specification, the frequency converters 21 and 23 have a basic configuration of a combination of a mixer, a local oscillator, and a filter, and the basic configuration has one or more stages.

Another embodiment of the frequency conversion method is shown in FIG.
This is a method that applies the phase shift method of single sideband carrier suppression modulation. The output end of the first DA converter 8 in the figure is I and the output end of the second DA converter 18 is Q. Data such that a desired output waveform signal appears at point I is stored in the first RAM 4
Write in. Further, data is written in the second RAM 16 such that a signal in which the phases of all the frequency components of the desired output waveform are shifted by 90 ° appears at point Q. The signal at point I is frequency-converted by the first balanced modulator 24, and the signal at point Q is frequency-converted by the second balanced modulator 25. The local signal 27 is directly applied to the balanced modulator 24. The local signal is phase-shifted by 90 ° by the phase shifter 26 and is applied to the balanced modulator 25. The signals whose frequencies have been respectively converted by the balanced modulators 24 and 25 are added by the adder 20 so as to have a difference therebetween, and then output. Since this method does not have unnecessary sidebands at the time of frequency conversion, a filter is not required, so that it is possible to convert to a high frequency in one stage. In this case, in addition to the distortion produced by each element, an image that occurs when the phase difference of the balanced modulation local signals is not 90 °, a local signal that leaks directly from the balanced modulator to the output, and the like are residual signals. However, it is possible to cancel it by treating all of them as distortion. This algorithm may be used by modifying the basic example or the one described in other examples.

(B) Filter method In the filter method, a filter is provided in front of the AD converter 15,
This is a method of removing or attenuating a signal component with a filter to increase the dynamic range of the AD converter with respect to the distortion component. This is particularly effective in applications where the number of frequencies at which distortion occurs is limited. Even when combined with the frequency conversion method, it is natural to install the filter at a position where the relative frequency difference between the signal frequency and the distortion frequency is large. Usually, the installation position is immediately before the AD converter.

(C) Frequency component measuring method The frequency component measuring method is a method in which the strain sensor section is replaced with a frequency component measuring device. As an example of the application of the signal generator, when the strain and the signal can be distinguished on the frequency axis, the strain can be converged to zero by using a device for measuring the frequency component. Reference numeral 28 in the embodiment shown in FIG. 7 is a frequency component measuring device. A spectrum analyzer can be cited as a typical example of an apparatus for measuring frequency components, and therefore an embodiment using a spectrum analyzer will be described here. In a spectrum analyzer, the distortion is obtained as a function of frequency, not the time series of equation (6).
However, equation (8) cannot be used because there is no phase information. Therefore, it is necessary to change the algorithm. Here, an example of an algorithm for converging the strain to be equal to or less than the allowable value based on only the amplitude information of the strain will be described. Here, the frequency of the strain of interest is f _d , and the effective value of the voltage of strain is V _d . Furthermore, transmission in f _d function _{G (f d · N / f} s)
Is easily measurable. Therefore, G (f _d · N / f _s )
Is known. To cancel this distortion, the frequency is f _d
Then, a sine wave having an effective value of V _d may be added to the output in a phase opposite to the distortion. Therefore, the following correction is applied to the data in the RAM.

[0029]

[Equation 7]

Θ is an unknown because the spectrum analyzer cannot measure the phase of the signal. Then, change the amplitude to V _d
/ G (f _d N / f _s ) is fixed, and the value of θ is variously changed, and x (n) is adjusted so that the amplitude of strain is minimized. Actually, if θ is changed several times and the strain amplitude is measured, it is possible to estimate θ that minimizes the strain amplitude. In this way, x which minimizes the amplitude of the strain
When (n) is obtained, the amplitude of this distortion is set as a new V _d , and the above-described processing is repeated, so that the distortion converges to the allowable value or less. If the distortion has multiple frequency components,
Strains are made to converge below the allowable value one by one. When the clocks of the DA converter and AD converter are not the same in the basic configuration of FIG. 1 and phase information cannot be obtained, the distortion is converged to the allowable value or less by the same method as the spectrum analyzer described here. Just do it.

(D) Strain sensor external attachment method The configuration of the signal generator according to this method is shown in FIG. Since there is no strain sensor part, it looks similar to the conventional method of FIG. 11, but the manufacturing method and the content of the data in the RAM are different. In the manufacturing method, a signal generator manufacturer prepares a highly accurate strain sensor as a manufacturing apparatus. When manufacturing a signal generator,
Input / output terminals and timing of this strain sensor manufacturing equipment
The clock input terminals are respectively connected to the strain sensor external terminals 29, 30, 31 of the signal generator to form the basic configuration of FIG. Next, the strain is reduced to the allowable value or less by the strain reduction algorithm shown in the basic configuration. The data of the RAM 4 in this state is stored in the non-volatile storage element before shipment. Since the RAM data has a value that cancels the distortion of the DA converter, the buffer amplifier, etc., it naturally differs from the data of the conventional system. The strain sensor unit is not added to each product, but is a manufacturing facility, so that expensive and highly accurate strain sensor units can be prepared. The user can store the waveform data stored in the non-volatile storage element in the RAM.
Can be written to and reproduced with a low distortion signal. Since this embodiment does not have a strain sensor section, it has a feature of realizing a low-distortion signal generator at a cost equivalent to that of a conventional DDS type signal generator. However, since the signal generator does not have a strain sensor, it is not possible to generate an arbitrary low-distortion waveform with the signal generator alone. However, if you connect your own spectrum analyzer to terminals 29 and 30,
It is possible to reduce the distortion of an arbitrary waveform by the method described in (c). The method for reducing the influence of strain generated by the strain sensor unit has been described above.

Next, an embodiment of the strain measuring device will be described. Harmonic distortion measurement and intermodulation distortion measurement are typical as distortion measurement of electronic devices. A single sine wave signal for the former measurement and two sine waves for the latter measurement.
It is common to use tone signals. Both measurements can be performed by applying the present invention. FIG. 9 shows an embodiment of the strain measuring device. The difference from the configuration of FIG. 1 is that
It is a circuit between the output terminal of the DDS signal source unit 3 and the input terminal of the strain sensor unit. Reference numeral 35 in FIG.
The entire left side of the terminals 33 and 34 is a strain measuring device. In operation, first, the double switch 32 is set to the d side, and a low distortion signal is generated from the DDS signal source unit 3 by the same configuration and method as the basic configuration of FIG. Next, with the data in the RAM unchanged, the switch 32 is switched to the c side, and this low distortion signal is applied from the terminal 33 to the electronic device under test 35.
The output of the electronic device under test 35 is connected to the strain sensor section from the terminal 34 via the switch 32. The strain sensor unit AD-converts the strain signal from the electronic device and sends it to the computer 2. The computer calculates the magnitude of strain from this data. Since this method applies a low strain signal to the electronic device under test, low strain measurement is possible. In addition, since the strain sensor unit also serves to measure the strain of the signal and the strain of the electronic device, it is possible to realize an economical strain measuring device with little cost to add to the signal generator. In addition, it is natural that the signal generator using the frequency converter of FIG. 5 or 6 can be applied to the high frequency strain measurement.

The measurement of intermodulation distortion due to the n-tone signal can also be realized in the embodiment shown in FIG. First, double switch 32
On the d side to generate an undistorted n-tone signal by the same configuration and method as the basic configuration of FIG. That is, x (n) may be obtained with the n-tone waveform as y _g (n). When such an n-tone signal is produced, the frequency for which low distortion is required is limited as compared with a general waveform generation device, so that the strain sensor unit can be simplified. This will be described by taking a two-tone generator as an example. In FIG. 10, fa and fb
Are the two frequencies of the two-tone signal. When a two-tone signal is applied to the electronic device under test, third-order intermodulation distortion occurs at the frequencies 2fa-fb and 2fb-fa near the signal. Usually, these two third-order intermodulation distortions occupy most of the distortions, so that distortions at other frequencies need not be considered. Therefore, the frequency of 2
A filter that passes only fa-fb and 2fb-fa is inserted to remove or attenuate fa and fb. As a result, AD
The dynamic range of the converter can be effectively utilized, the intermodulation distortion of the two-tone signal can be reduced, and the accuracy of measurement of the intermodulation distortion from the electronic device under test can be improved. The strain measuring device has been described above.

As an application example other than the above, if the capacity of the address of the RAM is increased, the period can be increased and a pseudo aperiodic signal can be generated. Two examples of the algorithm for gradually reducing the strain are given, that is, the case of the basic configuration and the case of using the spectrum analyzer as the strain sensor. However, such adaptive algorithms have been deeply studied in the field of adaptive filters, and most of the algorithms obtained from them can be applied.

[0035]

Industrial Applicability According to the present invention, a signal with little distortion can be easily produced, and strain measurement of an electronic device can be easily performed using the signal, which is particularly useful in the fields of electronic equipment and communication equipment. Both are beneficial. It should be noted that although the embodiments have been specifically described, modifications of the structure and the constituent elements are allowed as necessary without losing the gist of the present invention.

[Brief description of drawings]

FIG. 1 is a diagram showing a basic configuration of an embodiment of a signal generator of the present invention.

FIG. 2 is a flowchart of a distortion reduction algorithm of the signal generator of the present invention.

FIG. 3 is a diagram showing an embodiment using a plurality of DA converters of the signal generator of the present invention.

FIG. 4 is a diagram showing an embodiment of the frequency conversion method of the signal generator of the present invention.

FIG. 5 is a diagram showing a second embodiment of the frequency conversion method of the signal generator of the present invention.

FIG. 6 is a diagram showing a third embodiment of the frequency conversion method for the signal generator of the present invention.

FIG. 7 is a diagram showing an embodiment of a frequency component measuring method of the signal generator of the present invention.

FIG. 8 is a diagram showing an example of a strain sensor external attachment method for a signal generator according to the present invention.

FIG. 9 is a diagram showing an example of a strain measuring instrument of the present invention.

FIG. 10 is a diagram showing third-order intermodulation distortion of a two-tone signal.

FIG. 11 is a diagram showing an example of a signal generator according to a conventional DDS method.

[Explanation of symbols]

1: Feedback control unit 2: Calculator 3: DDS signal source unit 4: RAM 5: Data bus 6: Address bus 7: Switch 8: DA converter 9: Buffer amplifier 10: Address counter 11: Timing clock 12: Output terminal 13: Strain sensor unit 14: Buffer amplifier 15: AD converter 16: RAM 17: Switch 18: DA converter 19: Attenuator 20: Adder 21: Frequency converter 22: Frequency divider 23: Frequency conversion Device 24: Balanced modulator 25: Balanced modulator 26: 90 ° phase shifter 27: Local signal generator 28: Frequency component measuring device 29: Connection terminal with external strain sensor input 30: With external strain sensor output Connection terminal 31: Timing clock output terminal to external strain sensor 32: Switch 33: Signal output terminal 34 of strain measuring instrument : Signal input terminal 35 of strain measuring instrument: Electronic device under test

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-1-218201 (JP, A) JP-A-63-104523 (JP, A) JP-A-63-294131 (JP, A) JP-A-3- 88504 (JP, A) Actual opening 3-48915 (JP, U) Actual opening 5-20409 (JP, U) Actual opening 62-84215 (JP, U) Actual opening 5-63167 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) H03B 28/00 G01R 23/20

Claims (6)

(57) [Claims] 1. A signal generator, comprising: storage means, signal generation means, distortion detection means, and switch means, said storage means being means for storing digital waveform data. The means is means for generating a desired signal by performing digital-analog conversion on the digital waveform data, and the distortion detecting means detects distortion of the desired signal,
It is a means for measuring the frequency component of the distortion, and further, for each one of the distortions, a sine wave having the same frequency as the frequency of the distortion is measured so that the amplitude of the distortion is the smallest. A signal generator, comprising means for adjusting the phase and adding it to the digital waveform data to minimize the amplitude of all distortions detected by the distortion detecting means. 2. A signal generator, comprising: storage means, signal generation means, distortion detection means, and switch means, said storage means being means for storing digital waveform data. The means is means for generating a desired signal by performing digital-analog conversion on the digital waveform data, and the distortion detecting means detects distortion of the desired signal,
It is a means for measuring the frequency component of the distortion, and further, for each one of the distortions, a sine wave having the same frequency as the frequency of the distortion is measured so that the amplitude of the distortion is the smallest. in addition to the digital waveform data to adjust the phase, and the minimum amplitude is measured at that time as a new amplitude of the distortion, until the amplitude of the distortion becomes equal to or less than the allowable value, addition and of the strain to the digital waveform data A signal generator, characterized in that it comprises means for setting the amplitudes of all the distortions detected by the distortion detecting means to be equal to or less than an allowable value by repeating the updating of the amplitudes. 3. The amplitude of the sine wave is a value obtained by dividing the amplitude of the distortion by a transfer function value from the signal generating means to the distortion detecting means at the frequency of the distortion. The signal generator according to claim 1 or claim 2. 4. The signal generating apparatus according to claim 1, wherein the distortion detecting means is a spectrum analyzer. 5. The measured object when a signal is applied to the measured object.
Strain measuring device for measuring strain caused by objects
And the signal generation according to any one of claims 1 to 4.
A strain measuring device comprising: 6. The desired signal consists of one or more tones.
6. The device according to claim 1 , wherein the device is a signal that
Place