JPH0476463A - Data collecting system - Google Patents

Abstract

PURPOSE:To remove noise component from a signal by operating frequency analysis against digital data in a memory device to obtain the repeating cycles, and averaging them. CONSTITUTION:Data taken from an external memory device 3, an A/D convertor 5, or a digital input port 7 are received into arrangement in a memory 2, and sampling frequency is given as processing information from an input device 402. When the obtained digital signal contains much noise component and is hard to be hereafter processed, frequency analysis of the data is performed. In the frequency analysis, FFT is performed, processing object is collected from the spectrum of all signal component containing noise in the data to count back the signal frequency from it, the number of data constituting one signal period is obtained by the ratio of the frequency to the sampling frequency, and they are averaged. Hereby, noise component can be removed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a digital signal processing system, and particularly has a function of collecting and storing digital signals at high speed, and is used to perform signal processing on the data. Concerning suitable digital signal processing systems. [Prior Art] Generally, in a digital signal processing device such as a digital oscilloscope that takes in an analog electrical signal from the outside, digitizes it, stores it in a storage device such as a memory, and outputs it to a display device such as a cathode ray tube. When dealing with digital signals, the period of the signal is determined by detecting the rise and fall of the analog input signal, and based on this, a trigger signal for sweeping is generated and displayed on the screen. Furthermore, in Japanese Patent Application Laid-Open No. 63-282665, even if the data has already been digitized and stored in a storage device, the frequency of the signal in the data can be calculated using frequency analysis means such as fast Fourier transform (hereinafter also referred to as FFT). By knowing the repetition period, you can know the repetition period without using a trigger using an analog signal, and even in cases where it is difficult to reproduce the waveform with one data collection due to the high frequency of human input, digital data can be obtained after repeatedly collecting the waveform of multiple periods. A method has been proposed in which the data is rearranged and interpolated for reproduction. On the other hand, you can enlarge the part of the sampled digital signal,
The method for averaging and displaying is described in JP-A-63
It has been proposed in Publication No. 247665 and the like. In this proposal, when capturing an analog signal, a frequency counter is used to obtain the frequency of the signal to be processed, and based on that frequency, the repetition period of the signal data that has been digitized and stored in memory is determined. Averaging is performed. [Problems to be Solved by the Invention] In the method proposed in Japanese Patent Application Laid-Open No. 63-247665, averaging cannot be achieved unless the frequency of the analog signal manually input using a single frequency counter is known. Such operations are not possible. In other words, if the signal frequency information is lost, such as when an analog signal is digitized and stored in a storage device and then processed separately using only that digital data, it cannot be dealt with as is. . Further, the method proposed in the above-mentioned Japanese Patent Application Laid-Open No. 63-282665 only mentions cases where the frequency of the input analog signal is high, waveform reproduction is impossible, and interpolation must be performed. Therefore, when a non-transient analog signal that does not require interpolation is digitized and stored in a storage device, and the data is processed separately, for example, the frequency of the analog signal to be processed may be slightly changed compared to the sampling frequency of the digitizer. When processing collected data, such as beat waveforms, if the reproduced waveform has large noise components due to the accuracy of the oscillator used at the time of collection or the effects of external disturbances, interfering with processing, interpolation is necessary. Although it is not necessary, it does not support cases where waveform shaping is necessary. The present invention provides a method for removing noise components from a digital signal such as a beat waveform that has been digitized and stored in a storage device when the signal contains noise components and is difficult to process. [Means for solving the problem] The above problem is that when the digital data in the storage device is
Frequency analysis operation is performed to calculate the repetition frequency J (
This is achieved by knowing JJ and performing averaging. (Operation) By using this method, the beat waveform of a high-frequency analog signal can be digitized and the data stored in the storage device can be processed such as averaging to remove noise. , processing can be performed without using a repeating periodic trigger using an analog signal. [Examples] Examples of the present invention will be described below with reference to the drawings. FIG. 1 is an example of a flowchart showing a first embodiment of the present invention, and FIG. 5 is an example of the configuration of this system. First, a brief explanation of the system will be given using FIG. In the figure, 1 is a CPU for calculation and processing, 2 is a memory for storing data, 3 is an external storage device for long-term storage of data, and 4 is a link between the CPU and the system user. 401 is an interface unit that mediates the CRT.
, a display device such as a plotter, and 402 a human-powered device such as a keyboard and mouse. 5 is an AD converter for manually inputting an analog signal from the outside and digitizing it; 6 is a DA converter for outputting the digital data in memory as an analog signal; 7 is a digital signal digitized by the external AD converter 8 is a digital output port for converting signals into analog signals using an external DA converter. Next, the overall processing flow will be explained using FIG. 1. First, in the first stage, the external storage device 3, A
Data taken in from the D converter 5 or the digital input port is stored in an array in the memory 2, and a sampling frequency is given from the human power device 402 as information necessary for processing. If the digital signal obtained here does not contain noise components, or if it does contain noise components, it can be ignored, then normal processing can be performed as is. However, if the frequency band is too high for the accuracy of the oscillator to keep up with, or if the disturbance is large, there are many noise components that make further processing difficult, then frequency analysis of the data is performed as a second step. FIG. 2 shows an example of a flowchart for frequency analysis. FFT and the like are generally known as frequency analysis methods. The present invention is realized using this FFT. In the frequency analysis flow, first, the number of data is divided by a power of 2, such as a number such as 512.1024.4096, and if necessary, a window function is applied, and F F 'I' is executed. By performing FFT, the spectrum of all signal components including noise contained in the data is obtained. From among these spectra, select a spectrum that is considered to be that of the signal to be processed, and then calculate the frequency by 4f. The total number of data to be processed is N, the number of spectrum data of the signal to be processed is M, the frequency of the signal to be processed is fLa,
The sampling frequency is f. If 1k is bound, fIfi
can be derived from the following formula. f t++ ” f elk The number of data that constitutes the signal period can be determined by the ratio of this signal frequency and the sampling frequency.If you simply want to know the repetition period, there is no need to manually set the sampling frequency f aim. If only the total number of data N and the data number M of the spectrum of the signal to be processed are known, the repetition period T can be obtained by the following formula: T = However, in order to supply the system user with the human signal frequency as information, In addition, in the present invention, f.1 is given in order for the user to confirm whether the selected signal spectrum is really the one to be processed.
In the present invention, it is assumed that the spectrum of the signal component to be processed has greater power than the spectrum of the noise component, and the spectrum with the maximum power is selected as that of the signal to be processed. If there is a spectrum with large power in addition to the signal to be processed, the user will need to take steps to select the target from the obtained information such as frequency. In the fifth step, the number of data constituting one cycle is calculated as 8 based on the A1-1 frequency obtained in the second step, and averaging is performed based on this. If a signal for L periods is desired, the averaging result can be obtained by l), = Σ il 1B+IXTLl. At the final stage, the results are output to the display device 401 or saved to the external storage device 3 according to the user's wishes, and the process ends. FIG. 3 is a flowchart showing a second embodiment of the present invention. In the first embodiment, the accuracy of the oscillator may become a problem due to an increase in the frequency of the analog signal such as in the case of a beat waveform, or an error may be included in the number of data forming one cycle due to factors such as calculation errors. Even if you simply perform averaging, you will not be able to obtain accurate results. In averaging, in the worst case, the calculation result will be the average value of all data. Therefore, in order to suppress the error in the number of data during the period,
The repetition cycle is slightly changed around the number of data in one cycle determined by calculation, and the calculation is performed several times, allowing the user to select the result that they think is the best. be. In the process flow shown in FIG. 3, the data repetition period is first determined from the result of the frequency analysis in the previous stage. Next, the number m given by the user is used to average m times before and after the repetition cycle, and if the user considers the repetition cycle to be the best, it is selected as the final result. It is. As a guideline for determining the best result, it is recommended to know the signal amplitude to be processed from the original digital data and select the result with the amplitude closest to that amplitude. A third embodiment of the present invention is one in which this is automatically performed, and FIG. 4 shows an example thereof. The process flow is to determine the repetition period from the signal frequency, calculate the amplitude of the original signal, change the repetition period slightly around the value of the repetition period, execute SIl equalization processing, and calculate each result. Calculate the i-d vibration for. - After completing the above processing, the averaged result whose amplitude is closest to the amplitude of the original signal is adopted as the final result,
It is for displaying and saving. (Effect of the invention 1 According to the present invention, the period of a digital signal that has already been digitized and stored in a storage device is known by frequency analysis without using a trigger using an analog original signal, and the waveform can be reproduced. Processing such as or s1i equalization can be performed.

[Brief explanation of drawings]

FIG. 1 is a flowchart 1-1 of the process showing the first embodiment of the present invention. FIG. 2 is a flowchart of the process of the frequency analysis part in FIG. 1, and FIG. 3 is the second embodiment of the present invention. FIG. 4 is a flowchart of the processing of the averaging part in the third embodiment of the present invention, and FIG. 5 shows an example of the configuration of a system for performing the processing of the present invention. This is a diagram. Explanation of symbols 1... CPU, 2... Data memory, 3... External storage device, 4... Interface, 401... Display device, 402... Human power device, 5... A, D converter,
6...DA converter, 7...digital human-powered boat, 8
...Digital exit boat "];>-t>', K

Claims (1)

[Claims] 1. Having a function of digitizing analog signals or collecting externally digitized digital data, and collecting and storing digital data obtained by either or both of the above means. Then, in a data acquisition system that can perform digital signal processing on that data, the collected data is a beat waveform obtained by changing the signal frequency by more than an integer multiple of the digitizer's sampling frequency. If the collected data is distorted and cannot be observed accurately due to insufficient accuracy of the oscillator used to generate the oscillator or the influence of disturbances, the signal frequency is obtained from the stored digital data using frequency analysis means, and the signal period of the data is determined from that. A data collection system characterized by averaging data and removing noise components. 2. In the data averaging means, as a means for correcting errors included in the number of data constituting one cycle of the signal calculated by calculation, the number of data in one cycle is automatically slightly changed and the averaging is performed. 2. The data collection system according to claim 1, further comprising a re-execution function and means for selecting the best result from among the re-execution functions. 3. In the data averaging means, as a means of correcting errors included in the number of data included in one cycle of the signal calculated by calculation, the number of data in one cycle is automatically slightly changed and averaged. Claim 1 characterized by the function of re-executing the waveform and calculating the amplitude of the waveform of the averaged result, selecting and outputting the one closest to the amplitude of the original signal as the result.
or 2. The data collection system described in 2.