JP2000284008A - Frequency measuring method and frequency measuring device - Google Patents

Abstract

(57) [Summary] A frequency measuring device for measuring a frequency component up to a sampling frequency FC by a simple procedure without having to take sampling data twice from an input signal is obtained. A spectrum data which does not include a folded component of a frequency DC to Fc / 2 is calculated, and a frequency D is calculated.
From the frequency Fc / 2 to the Fc component of the spectrum data including the aliasing component of the C to Fc components, the frequency DC to Fc / 2
By subtracting the aliasing component of the component, the frequency Fc / 2 to Fc
The spectrum data which does not include the aliasing component of the component is calculated 14, and the frequency DC to Fc / 2 component and the frequency Fc / 2 are calculated.
The spectrum data up to the sampling frequency Fs that does not include the aliasing component can be obtained by a simple procedure by synthesizing 15 with the spectrum data not including the aliasing component of the Fc component.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for digitizing and inputting an analog input signal and measuring a frequency characteristic mainly by using a fast Fourier transform (hereinafter abbreviated as FFT). The present invention relates to a frequency measurement method and a frequency measurement device capable of measuring a frequency component up to a sampling frequency.

[0002]

2. Description of the Related Art Conventionally, there has been such a frequency measuring device as shown in FIG. FIG. 4 is a block diagram showing the configuration of the conventional frequency measuring device 1. In such a conventional frequency measuring device 1, when measuring the frequency, L
The PF 400 passes only a component equal to or less than の of the sampling frequency Fs, and the A / D converter 401 converts the input signal into digital data and stores the digital data in the waveform memory 402. Next, FFT processing or the like is performed on the digital data stored in the waveform memory 402 by the frequency analysis unit 41,
Spectrum data can be obtained.

In the LPF 400 described above, only the frequency component of Fs / 2 or less of the input signal is passed through A /
When the input signal is sampled by the D converter 401, Fs
Since the component of / 2 or more is folded and added to the component of DC to Fs / 2 and cannot be determined, the component of Fs / 2 or more is removed in advance by the LPF 400 to obtain only the DC to Fs / 2 component. . According to the conventional frequency measuring apparatus 1 described above, spectrum data in the frequency domain DC to Fs / 2 can be obtained.

[0004] However, it can be seen that in the above-mentioned conventional frequency measuring apparatus 1, the upper limit of the measurable frequency is limited to 1/2 of the sampling frequency of the A / D converter. Generally, an A / D converter becomes expensive in proportion to the height of the sampling frequency, and therefore, to measure a high frequency, a more expensive A / D converter must be used.

[0005] As another conventional frequency measuring device which has attempted to solve this problem, there is one as shown in FIG. FIG. 5 is a block diagram showing the configuration of another conventional frequency measuring device 2. (Similar ones include, for example,
-200200). According to this device, the sampling speed minute change means 503 for changing the sampling speed by the minute value Δf, the peak detection means 53 and 54,
Providing a peak comparing means 55 and an aliasing component removing means 56, the peak of the frequency component of the data acquired without changing the sampling frequency Fs and the frequency component of the data acquired by changing the sampling frequency Fs by a small value Δf By comparing and judging and removing aliasing components, the frequency is measured up to a component equal to or more than １ ／ of the sampling frequency.

[0006]

However, such a conventional frequency measuring device 2 requires a technically difficult means for changing the sampling speed by a small value Δf, and the determination of the aliasing component is difficult. Since the comparison is performed by comparing peaks, it is necessary to repeat determination and removal of aliasing components by the number of peaks. Therefore, an algorithm for removing aliasing components becomes complicated. further,
When there is no peak or when the difference between the peak and the floor level is small, there is a problem that it is difficult to remove aliasing components.

Also, such a conventional frequency measuring device 2
Then, since it is necessary to acquire sampling data twice from the input signal, the frequency characteristics of the input signal may change between the two acquisitions. In such a case, the measurement result may not be accurate. There was a problem that did not become.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problem. Two types of LPs are provided before an A / D converter.
F is provided to calculate the spectrum data of the input signal based on the sampling data of the A / D converter, so that it is not necessary to take the sampling data twice from the input signal. The purpose is to measure.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides an A / D converter for converting a DC component of an analog input signal.
The signal of the frequency L component up to half the sampling frequency Fs of the converter is passed, the signal of the frequency L component is A / D-converted to obtain digital data of the frequency L component, and the obtained digital data of the frequency L component From the spectrum data that does not include the aliasing component of the frequency L component,
Similarly, the spectrum data including the aliasing component of the signal of the frequency A component from the DC component of the analog input signal to the sampling frequency Fs of the A / D converter is calculated, and the sampling frequency of the spectrum data including the aliasing component of the frequency A component is calculated. From the frequency H component from 1/2 of Fs to the sampling frequency Fs, the folded component obtained by symmetrically folding the spectrum data of the frequency L component around the sampling frequency Fs / 2 is subtracted to obtain the folded component of the frequency H component. The spectrum data that does not include the calculated frequency L component and the spectrum data that does not include the aliasing component of the frequency H component are synthesized, and the spectrum data that does not include the aliasing component of the frequency A component of the analog input signal is obtained. Things.

According to the present invention, the spectrum data not including the aliasing component of the frequency L component is calculated, and the aliasing component of the frequency L component is subtracted from the frequency H component of the spectrum data including the aliasing component of the frequency A component.
By calculating spectrum data that does not include the aliasing component of the component and combining the spectrum data that does not include the aliasing component of the frequency L component and the frequency H component, the A / D converter that does not include the aliasing component by a simple procedure. Spectrum data up to the sampling frequency Fs is obtained, and a frequency measurement method and a frequency measurement device capable of measuring the frequency band are obtained.

According to the present invention, in order to achieve the above object, A
The signal of the frequency L component up to 1/2 of the sampling frequency Fs of the / D converter or the signal of the frequency A component from the DC component of the analog input signal to the sampling frequency Fs of the A / D converter is selectively passed. A / D conversion is performed on the signal of the selected frequency L component or the frequency A component to obtain digital data of the frequency L component or the frequency A component. When the frequency L component is selected, the obtained frequency L Spectrum data including no aliasing component of the frequency L component and aliasing component spectrum data are calculated from the digital data of the component, and when the frequency A component is selected, the aliasing component of the frequency A component is obtained from the acquired digital data of the frequency A component. Is calculated, and the spectrum data including the aliasing component of the frequency A component is calculated. 1/2 of the sampling frequency Fs
To calculate the spectrum data not including the aliasing component of the frequency H component by subtracting the aliasing component spectrum data calculated from the frequency H component from the sampling frequency Fs to the spectrum data not including the aliasing component of the calculated frequency L component. The spectrum data that does not include the aliasing component of the frequency A component is synthesized by combining the spectrum data that does not include the aliasing component of the frequency H component.

The present invention selectively calculates spectrum data that does not include the aliasing component of the frequency L component, calculates spectrum data that includes the aliasing component of the frequency A component, and calculates the frequency H component of the frequency A component that includes the aliasing component. Subtracting the aliasing component of the frequency L component from the spectrum data of, calculating the spectrum data not including the aliasing component of the frequency H component, and synthesizing the spectrum data not including the aliasing component of the frequency L component and the frequency H component. Accordingly, spectrum data up to the sampling frequency Fs of the A / D converter that does not include aliasing components can be obtained by a simple procedure, and a frequency measurement method and a frequency measurement device capable of measuring the frequency band can be obtained.

Before describing the embodiments of the present invention in detail, the outline of the present invention will be described below to facilitate understanding of the present invention. A low-pass filter (hereinafter abbreviated as LPF_L) that passes frequency components from DC to Fs / 2, an A / D converter that operates with a sampling clock having a frequency of Fs, and A / D-converted digital data. The data input means L including the stored waveform memory L passes only the components from DC to Fs / 2 of the analog input signal, converts it into digital data, and stores it in the waveform memory L.

A low-pass filter (hereinafter abbreviated as LPF_H) for passing frequency components from DC to Fs, an A / D converter operating with the same sampling clock Fs as the data input means L, Data input means H including a waveform memory H for storing the / D-converted digital data, passes only the DC to Fs frequency component (frequency A component) of the analog input signal, converts the analog input signal into digital data, and converts the analog data into the waveform memory H Store.

The frequency L calculating means performs processing such as FFT conversion on the digital data in the waveform memory L, and calculates spectrum data of DC to Fs / 2 frequency components (frequency L components) that do not include aliasing components. Also, the frequency H
The calculating means performs FFT on the digital data in the waveform memory H.
Fs including aliasing components obtained by performing processing such as conversion
From the spectrum data of / 2 to Fs frequency component (frequency H component), the folded component obtained by folding the spectrum data of (frequency L component) calculated by the frequency L calculating means symmetrically around Fs / 2 is subtracted. , The spectrum data of the frequency H component not including the aliasing component is calculated.

The synthesizing means synthesizes the spectrum data of the frequency L component and the frequency H component which do not include the aliasing component respectively calculated by the frequency L calculating means and the frequency H calculating means, and obtains the spectrum data of the frequency A component which does not include the aliasing component. Is obtained. By configuring as described above and measuring the frequency characteristics, it is possible to measure the frequency band up to the sampling frequency Fs of the A / D converter.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention passes a signal of a frequency L component from a DC component of an analog input signal to a half of a sampling frequency Fs of an A / D converter. A / D conversion is performed on the signal of the frequency L component to obtain digital data of the frequency L component, and spectrum data that does not include the aliasing component of the frequency L component is calculated from the obtained digital data of the frequency L component. Passing the signal of the frequency A component from the DC component of the signal to the sampling frequency Fs of the A / D converter,
A / D conversion is performed on the signal of the frequency A component to obtain digital data including a folded component of the frequency A component, and a frequency A is obtained from the obtained digital data of the frequency A component.
The spectrum data including the aliasing component of the frequency component is calculated, and the frequency L component is calculated from the frequency H component from 1/2 of the sampling frequency Fs to the sampling frequency Fs of the spectrum data including the aliasing component of the frequency A component.
The spectrum data of the component is converted to
The spectrum data without the aliasing component of the frequency H component is calculated by subtracting the aliasing component obtained by symmetrically folding around the center 2, and the calculated spectrum data without the aliasing component of the frequency L component and the frequency H component are calculated. The method comprises the steps of synthesizing spectrum data that does not include the aliasing component of the analog input signal, and obtains spectrum data that does not include the aliasing component of the frequency A component of the analog input signal. To calculate the spectrum data not including the aliasing component of the frequency L component, subtracting the aliasing component of the frequency L component from the frequency H component of the spectrum data including the aliasing component of the frequency A component, and including the aliasing component of the frequency H component. Calculate the spectrum data without the frequency L component and the frequency H component By combining the spectrum data with no aliasing component, spectrum data up to the sampling frequency Fs of the A / D converter containing no aliasing component can be obtained by a simple procedure, and its frequency band can be measured. Has an action.

According to a second aspect of the present invention, A / D conversion is performed from the DC component of the analog input signal under the control of the control means.
The signal of the frequency L component up to 1/2 of the sampling frequency Fs of the converter or the signal of the frequency A component from the DC component of the analog input signal to the sampling frequency Fs of the A / D converter is selectively passed. A / D converting the selected signal of the frequency L component or the frequency A component to obtain digital data of the frequency L component or the frequency A component. When the frequency L component is selected, the obtained digital data is obtained. From the digital data of the frequency L component, spectrum data not including the aliasing component of the frequency L component and the aliasing component spectrum data are calculated. When the frequency A component is selected, the frequency A component is calculated from the acquired digital data of the frequency A component. Calculates spectrum data including the aliasing component of the frequency A component, and includes the aliasing component of the frequency A component. By subtracting the calculated return component spectrum data from the frequency H component from 1/2 of the sampling frequency Fs of the spectrum data to the sampling frequency Fs, spectrum data not including the return component of the frequency H component is calculated, and the calculated value is calculated. The spectrum data that does not include the aliasing component of the frequency L component and the spectrum data that does not include the aliasing component of the frequency H component are combined to generate spectrum data that does not include the aliasing component of the frequency A component. Selectively calculates spectrum data that does not include the aliasing component of the frequency L component, calculates spectrum data that includes the aliasing component of the frequency A component, and calculates the frequency L component from the spectrum data of the frequency H component of the frequency A component that includes the aliasing component. Fold By subtracting the frequency component and calculating the spectrum data that does not include the aliasing component of the frequency H component, and combining the frequency L component and the spectrum data that does not include the aliasing component of the frequency H component, the aliasing component can be calculated by a simple procedure. A not including
The spectrum data up to the sampling frequency Fs of the / D converter can be obtained, and the frequency band can be measured.

According to a third aspect of the present invention, there is provided an LPF_L for passing a signal of a frequency L component from a DC component of an analog input signal to a half of a sampling frequency Fs of an A / D converter, and the LPF_L L passed through
A data input means L including an A / D converter for sampling a component and outputting digital data of a frequency L component; a waveform memory L for storing the digital data of the frequency L component; From A /
An LPF_H that passes a signal of a frequency A component up to a sampling frequency Fs of a D converter, and a frequency A component that has passed through the LPF_H is sampled by a sampling clock common to the sampling clock of the frequency L component and a digital signal of the frequency A component is obtained. A to output data
Data input means H comprising a / D converter and a waveform memory H for storing the digital data of the frequency A component.
Frequency L calculating means for calculating, from digital data in the waveform memory L, spectrum data that does not include the aliasing component of the frequency L component; and spectrum data of the frequency H component including the aliasing component calculated from the digital data in the waveform memory H. From the calculated spectrum data of the frequency L component, the sampling frequency Fs / 2
Frequency H calculating means for calculating spectrum data that does not include the aliasing component of the frequency H component by subtracting the aliasing component calculated by folding back around the center, and spectrum data that does not include the aliasing component of the calculated frequency L component. And a synthesizer for synthesizing the spectrum data without the aliasing component of the frequency H component to generate the spectrum data without the aliasing component of the frequency A component. D-conversion is performed to calculate spectrum data that does not include the return component of the frequency L component. Then, the return component of the frequency L component is subtracted from the frequency H component of the spectrum data that includes the return component of the frequency A component, and the return of the frequency H component is performed. Calculate the spectrum data that does not include the component, and calculate the frequency L component and By combining the wave number H component with the spectrum data containing no aliasing component, spectrum data up to the sampling frequency Fs of the A / D converter containing no aliasing component is obtained by a simple procedure, and the frequency band is measured. It has the effect of being able to.

According to a fourth aspect of the present invention, there is provided an LPF_L for passing a signal of a frequency L component from a DC component of an analog input signal to a half of a sampling frequency Fs of an A / D converter; LPF_H for passing a signal of a frequency A component from a DC component of an input signal to a sampling frequency Fs of an A / D converter, a selecting means for selecting either the LPF_L or LPF_H under the control of a control means, LPF_L or L
The frequency L component or the frequency A component that has passed through the PF_H is sampled to obtain the frequency L component or the frequency A component.
Data input means having an A / D converter for outputting digital data of the component, a waveform memory for storing the digital data of the frequency L component and the frequency A component, and the waveform memory when the LPF_L is selected Frequency L calculating means for calculating spectrum data that does not include the aliasing component of the frequency L component from the digital data of
When the LPF_L is selected, the folded component spectrum data of the frequency L component is calculated and held from the digital data of the waveform memory, and when the LPF_H is selected, the folded component is included based on the digital data of the waveform memory. By subtracting the held-back component spectrum data from the frequency H component from 1/2 of the sampling frequency Fs of the spectrum data to the sampling frequency Fs, the frequency H for calculating the spectrum data not including the folded component of the frequency H component is calculated. Calculating means; and spectrum data which does not include the aliasing component of the calculated frequency L component;
Combining means for combining the spectrum data not containing the aliasing component of the component with the spectrum data not containing the aliasing component of the frequency A component, and selectively converting the aliasing component of the frequency L component. Calculate the spectrum data not including, calculate the spectrum data including the aliasing component of the frequency A component, subtract the aliasing component of the frequency L component from the spectrum data of the frequency H component of the frequency A component including the aliasing component,
By calculating spectrum data that does not include the aliasing component of the frequency H component and combines the frequency L component and the spectrum data that does not include the aliasing component of the frequency H component, A / D that does not include the aliasing component can be performed by a simple procedure.
The spectrum data up to the sampling frequency Fs of the converter can be obtained, and the frequency band can be measured.

Hereinafter, based on the attached drawings and FIGS. 1 to 3,
Embodiments 1 and 2 of the present invention will be described in detail. (Embodiment 1) First, a frequency measuring apparatus according to Embodiment 1 of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram showing a configuration of a frequency measurement device according to Embodiment 1 of the present invention. FIG. 3 is a diagram showing a procedure for calculating spectrum data in the Fs / 2 to Fs region in the frequency measurement device shown in FIG. is there.

In FIG. 1, 100 is a half of a sampling frequency (referred to as Fs) from a DC component (referred to as DC).
, A low-pass filter (referred to as LPF_L) that passes only a frequency component (referred to as a frequency L component), 101 is an A / D converter that converts an analog input signal into digital data with a sampling clock having a frequency of Fs, and 102 is an A / D converter.
A waveform memory L for storing D-converted digital data. The LPF_L100, the A / D converter 101, and the waveform memory L102 constitute a data input unit L10. Therefore, the data input means L10 outputs the DC signal of the input signal.
The Fs / 2 component (frequency L component) is converted into digital data and stored in the waveform memory L102.

Reference numeral 110 denotes a low-pass filter (referred to as LPF_H) that passes only the frequency components of DC to Fs (referred to as frequency A component).
A / D converter for converting an analog input signal into digital data at the same sampling clock Fs as 100;
Reference numeral 12 denotes a waveform memory H for storing the converted digital data. The LPF_L 110, the A / D converter 111, and the waveform memory H112 constitute a data input unit H11. Therefore, the data input means H11 outputs the D signal of the input signal.
The C to Fs components are converted into digital data and stored in the waveform memory H112. Here, the digital data stored in the waveform memory H is data to which a folded component centering on Fs / 2 is added.

Reference numeral 12 denotes A / D converters 101 and 111.
A sampling clock generating means for generating a sampling clock Fs to be supplied to the CPU, and a frequency L calculating means for converting digital data stored in the waveform memory L102 into spectrum data by performing an FFT process or the like. The spectrum data of the frequency L component is obtained from the means 13.

Next, reference numeral 14 denotes a frequency component between Fs / 2 and Fs based on the spectrum data of the frequency L component obtained by the frequency L calculating means 13 and the spectrum data to which the aliasing component stored in the waveform memory H112 is added. It is a frequency H calculating means for calculating spectrum data of (frequency H component). The method of calculating the spectrum data of the Fs / 2 to Fs frequency components (frequency H components) will be described later in detail with reference to FIG.

Finally, reference numeral 15 denotes a synthesizing means for synthesizing the calculation result of the frequency L calculating means 13 and the calculation result of the frequency H calculating means 14 on the frequency axis to obtain spectrum data of the frequency H component.

Next, referring to FIG. 3, the operation of the frequency measuring apparatus according to the first embodiment of the present invention
A method of calculating the spectrum data of the Fs frequency component (frequency H component) will be described. In FIG. 3, reference numeral 30 denotes an example of the original spectrum of the input signal.
Here, the characteristic of the LPF_L100 of the data input means L10 is up to Fs / 2 as shown by the solid line, and the characteristic of the LPF_H110 of the data input means H11 is passed from DC to Fs as shown by the dotted line. Accordingly, when the spectrum of the signal sampled by the waveform acquisition means L (not shown) of the A / D converter 101 is obtained, as shown in the spectrum 31 passing through the LPF_L, the frequency components of DC to Fs / 2 are obtained. Can be

On the other hand, the spectrum of the signal sampled by the waveform acquisition means H (not shown) of the A / D converter 111 is the spectrum 32 which has passed through the LPF_H.
As shown in FIG. 3, DC is obtained by adding a folded component (indicated by a dotted line) centered on Fs / 2 to the original spectrum 30.
The frequency component of Fs is obtained. Since the data desired to be acquired is spectrum data having no aliasing component in the frequency H component, it is necessary to remove the aliasing component from the spectrum data 32 by the following procedure.

First, Fs / 2 of the spectrum data 32
The spectrum 34 is obtained by cutting out the Fs region. Next, a spectrum (calculated aliasing component) 3 representing the spectrum data 31 symmetrically with respect to the frequency Fs / 2.
Get 3. This spectrum 33 is a spectrum 34
Have the same characteristics as the aliasing component (dotted line) in. Therefore, from the spectrum 34 to the spectrum 3
When 3 is subtracted for each corresponding frequency, the spectrum 35 of the difference becomes the spectrum component of the frequency H component from which the aliasing component has been removed.

The spectrum data 35 of the frequency H component having no aliasing component can be obtained from the input signal fetched at the sampling frequency Fs by the method as described above. By combining the obtained spectrum 31 without the aliasing component and the spectrum 35 without the aliasing component obtained from the frequency H calculating means 14, it is possible to calculate the spectrum 36 without the aliasing component of the frequency A component.

According to the frequency measuring method in the first embodiment, the aliasing component of the measured frequency can be removed by a simple operation of data rearrangement and subtraction.
With a simple system configuration, frequency measurement from DC to the sampling frequency Fs can be realized. In addition, in this configuration, since the data input means L10 and the data input means H11 have a common sampling clock, the data can be simultaneously captured. Therefore, there is no time difference between the captured data and the data can be measured more accurately. can do.

(Embodiment 2) Next, referring to FIG.
A frequency measuring device according to Embodiment 2 of the present invention will be described. FIG. 2 is a block diagram showing a configuration of the frequency measuring device according to Embodiment 2 of the present invention.

In FIG. 2, reference numeral 200 denotes an LPF that passes only the frequency L component. L, 201 is an LPF_H that passes only the frequency A component, and 202 is an LPF L200 or L
Selection means for selecting one of PF_H201, 2
A / 03 which converts an analog input signal into digital data with a sampling clock having a sampling frequency Fs.
A D converter 204 is a waveform memory for storing A / D converted digital data, and 21 is a sampling clock generating means for generating a sampling clock Fs to be supplied to the A / D converter 203. LPF_L200 and LPF_
The data input means 20 is constituted by the H 201, the selection means 202, the A / D converter 203, the waveform memory 204 and the sampling clock generation means 21. Therefore, the data input means 20 selectively converts the DC to Fs / 2 frequency component (frequency L component) of the input signal and the DC to Fs frequency component (frequency A component) of the input signal into digital data, and stores the digital data in the waveform memory 204. It is configured to store.

Reference numeral 23 denotes frequency L calculating means for reading digital data from the waveform memory 204 and calculating spectrum data of a frequency L component.
Frequency H calculating means for reading digital data from the H.04 and calculating spectrum data of a frequency H component; 25
Is a synthesizing means for synthesizing the calculation results of the frequency L calculating means 23 and the frequency H calculating means 24 to obtain spectrum data of the frequency A component, 22 is a selecting means 202 for selecting LPF_L or LPF_H, and a sampling clock generating means 21
And a control unit for controlling the operations of the frequency L calculating means 23 and the frequency H calculating means 24.

Next, referring to FIG. 2, the operation of the frequency measuring apparatus according to the second embodiment of the present invention
A method of calculating the spectrum data of the Fs frequency component (frequency H component) will be described. The selecting means 202 first operates to select the LPF_L 200 by the control means 22, and the A / D converter 203 converts the signal passing through the frequency range from DC to Fs / 2 into digital data and converts the signal into digital data. To be stored.

At this time, the frequency L calculating means 23 performs a process such as FFT on the data read from the waveform memory 204 to obtain and hold the spectrum data in the DC to Fs / 2 region. Further, the frequency H calculating means 24 calculates a folded component which represents the spectrum data of the DC to Fs / 2 frequency components obtained by performing processing such as FFT on the data in the waveform memory 204 symmetrically with respect to Fs / 2. And keep it.

Next, LPF_H2
01 is selected, the LPF_H 201
Passes C to Fs frequency components. A / D converter 203
Converts the frequency components passing through the DC-Fs frequency band into digital data and stores the digital data in the waveform memory 204.
During this period, the frequency L calculation means 23 is controlled by the control means 22 and does not perform any operation.

On the other hand, in the frequency H calculating means 24,
The data of the DC to Fs frequency components is read from the waveform memory 204 and subjected to processing such as FFT, and the held spectrum data of the folded components is subtracted from the spectrum data of the frequency H components including the folded components to remove the folded components. Spectrum data of the calculated frequency H component is calculated. Finally, in the synthesizing unit 25, the spectrum data of the frequency L component and the frequency H component that do not include the aliasing component, which are the calculation results of the frequency L calculating unit 23 and the frequency H calculating unit 24, are synthesized on the frequency axis, thereby obtaining the frequency A component. Is obtained.

According to the above-described frequency measurement method in the second embodiment, the first embodiment is applied to the case where the frequency component of the signal under measurement does not fluctuate within two acquisition periods.
Almost the same effect can be realized with a small circuit scale. Particularly, since an A / D converter, which is an expensive component, can be constituted by one, it can be realized at a lower cost than in the first embodiment.

[0040]

The present invention is constructed as described above, and in particular, calculates spectrum data that does not include the return component of the frequency L component, and converts the spectrum data that includes the return component of the frequency A component from the frequency H component to the frequency L component. Is calculated by subtracting the aliasing component of the frequency component and calculating the spectrum data not including the aliasing component of the frequency H component, and combining the frequency L component and the spectrum data not including the aliasing component of the frequency H component, by the simple procedure. Sampling frequency Fs of A / D converter without component
Spectrum data up to this point, and an inexpensive frequency measurement method and apparatus capable of measuring its frequency band.

The present invention is configured as described above, and in particular, selectively calculates spectrum data that does not include the aliasing component of the frequency L component, calculates the spectrum data that includes the aliasing component of the frequency A component, and calculates the aliasing component. Subtracting the aliasing component of the frequency L component from the spectrum data of the frequency H component of the included frequency A component to calculate spectrum data not including the aliasing component of the frequency H component;
By combining the frequency L component and the spectrum data that does not include the aliasing component of the frequency H component, spectrum data up to the sampling frequency Fs of the A / D converter that does not include the aliasing component can be obtained by a simple procedure.
An inexpensive frequency measuring method and frequency measuring device capable of measuring the frequency band can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a frequency measurement device according to a first embodiment of the present invention;

FIG. 2 shows the frequency measuring device shown in FIG.
The figure which shows the procedure in which the spectrum data of Fs area | region is calculated,

FIG. 3 is a block diagram illustrating a configuration of a frequency measurement device according to a second embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of a conventional frequency measurement device 1.

FIG. 5 is a block diagram showing a configuration of another conventional frequency measuring device 2.

[Explanation of symbols]

Reference Signs List 10 data input means L 11 data input means H 12 sampling clock generation means 13 frequency L (frequency domain DC to Fs / 2) calculation means 14 frequency H (frequency domain Fs / 2 to Fs) calculation means 15 synthesis means 20 data input means Reference Signs List 21 sampling clock generating means 22 control means 23 frequency L (frequency domain DC to Fs / 2) calculating means 24 frequency H (frequency domain Fs / 2 to Fs) calculating means 25 combining means 30 original spectrum 31 spectrum through LPF_L 32 Spectrum passing through LPF_H 33 Calculated aliasing component 34 Spectrum of Fs / 2 to Fs area including aliasing component 35 Spectrum of Fs / 2 to Fs area with aliasing component removed 36 Calculated spectrum of DC to Fs 40 Data input Means 41 Frequency calculation means 50 in the wavenumber domain DC to Fs / 2 50 Data input means 51 Frequency calculation means 1 52 Frequency calculation means 2 53 Peak detection means 1 54 Peak detection means 2 55 Peak comparison means 56 Aliasing component removal means 100 DC to Fs / 2 Low-pass filter (LPF
L) 101 A / D converter 102 Waveform memory L 110 Low-pass filter (LPF) of DC to Fs H) 111 A / D converter 112 Waveform memory H 200 Low-pass filter (LPF) of DC to Fs / 2
L) 201 DC-Fs low-pass filter (LPF) H) 202 selection means 203 A / D converter 204 waveform memory 400 DC-Fs / 2 low-pass filter (LPF) 401 A / D converter 402 waveform memory 403 sampling clock generation means 500 low-pass filter (LPF) Reference numeral 501 A / D converter 502 Waveform memory 503 Sampling clock generating means 504 Sampling speed minute change means 505 Control means

Claims (4)

[Claims] 1. A frequency L from a DC component of an analog input signal to a half of a sampling frequency Fs of an A / D converter.
A / D conversion of the signal of the frequency L component is performed to obtain digital data of the frequency L component, and the frequency L component is obtained from the obtained digital data of the frequency L component.
Calculates spectrum data that does not include a folded component of the component, passes a signal of a frequency A component from a DC component of the analog input signal to a sampling frequency Fs of an A / D converter, and converts the signal of the frequency A component into an A / D signal. The digital data including the folded component of the frequency A component is obtained by the conversion, the spectrum data including the folded component of the frequency A component is calculated from the acquired digital data of the frequency A component, and the folded data of the frequency A component is included. The frequency component is obtained by subtracting the folded component obtained by symmetrically folding the spectrum data of the frequency L component around the sampling frequency Fs / 2 from the frequency H component from 1/2 of the sampling frequency Fs of the spectrum data to the sampling frequency Fs. Spectra without H-folded components Each step of calculating data and combining the calculated spectrum data without the aliasing component of the frequency L component and the spectrum data without the aliasing component of the frequency H component, comprising the aliasing component of the frequency A component of the analog input signal. A frequency measurement method characterized by obtaining spectrum data that does not include a frequency. 2. A signal of a frequency L component from a DC component of an analog input signal to a half of a sampling frequency Fs of an A / D converter under control of a control means, or A / D conversion from a DC component of the analog input signal. The signal of the frequency A component up to the sampling frequency Fs of the D converter is selectively passed, and the signal of the selected frequency L component or the frequency A component is subjected to A / D conversion to obtain the frequency L component or the frequency A.
The digital data of the component is obtained, and when the frequency L component is selected, the spectrum data not including the folded component of the frequency L component and the folded component spectrum data are calculated from the obtained digital data of the frequency L component, When the A component is selected, the spectrum data including the aliased component of the frequency A component is calculated from the acquired digital data of the frequency A component, and is calculated as 1/1 of the sampling frequency Fs of the spectrum data including the aliased component of the frequency A component. By subtracting the calculated return component spectrum data from the frequency H component from 2 to the sampling frequency Fs, spectrum data that does not include the return component of the frequency H component is calculated and does not include the return component of the calculated frequency L component. Spectra Frequency measurement method characterized by the spectrum data which does not include aliasing components of data and the frequency H component synthesis to have to generate a spectrum data which does not include aliasing components in the frequency A component. 3. A frequency L from a DC component of an analog input signal to a half of a sampling frequency Fs of an A / D converter.
An LPF_L for passing a component signal, and the LPF_L
An analog-to-digital (A / D) converter for sampling the frequency L component passed through the circuit and outputting digital data of the frequency L component; a data input means L including a waveform memory L for storing the digital data of the frequency L component; From the DC component of the input signal, the sampling frequency Fs of the A / D converter
LPF_H that passes the signal of the frequency A component up to
The frequency A component that has passed through the LPF_H is
A data input means H comprising an A / D converter for sampling digital data of the frequency A component by sampling with a sampling clock common to the component sampling clock and a waveform memory H for storing the digital data of the frequency A component Frequency L calculating means for calculating, from digital data in the waveform memory L, spectrum data that does not include the aliasing component of the frequency L component; and spectrum data of the frequency H component including the aliasing component calculated from the digital data in the waveform memory H. From the calculated frequency H, the spectrum data without the aliasing component of the frequency H component is calculated by subtracting the aliasing component calculated by folding the calculated spectrum data of the frequency L component symmetrically around the sampling frequency Fs / 2. Calculation means and before A synthesizing unit that synthesizes the calculated spectrum data that does not include the aliasing component of the frequency L component and the spectrum data that does not include the aliasing component of the frequency H component to generate spectrum data that does not include the aliasing component of the frequency A component. A frequency measuring device characterized by the above-mentioned. 4. A frequency L from a DC component of an analog input signal to a half of a sampling frequency Fs of an A / D converter.
LPF_L that passes the signal of the component, and LPF_L that passes the signal of the frequency A component from the DC component of the analog input signal to the sampling frequency Fs of the A / D converter.
H and the LPF_L or LPF_ under the control of the control means.
Selecting means for selecting any one of H, and the selected L
An A / D converter that samples the frequency L component or the frequency A component that has passed through the PF_L or the LPF_H and outputs digital data of the frequency L component or the frequency A component; Data input means having a waveform memory for storing digital data; and frequency L calculating means for calculating spectrum data not including a folded component of the frequency L component from digital data of the waveform memory when the LPF_L is selected. When the LPF_L is selected, the folded component spectrum data of the frequency L component is calculated and held from the digital data of the waveform memory, and when the LPF_H is selected, the folded component is calculated based on the digital data of the waveform memory. Sample of spectrum data including Frequency H calculating means for calculating spectrum data that does not include the aliasing component of the frequency H component by subtracting the held aliasing component spectrum data from the frequency H component from 1/2 of the sampling frequency Fs to the sampling frequency Fs. Synthesizing means for synthesizing the calculated spectrum data without the aliasing component of the frequency L component and the spectrum data without the aliasing component of the frequency H component to generate spectrum data without the aliasing component of the frequency A component; A frequency measuring device comprising: