JPH01257233A - Detecting method of signal - Google Patents

Abstract

PURPOSE:To enable the sure detection of a signal to be detected, by a method wherein a signal containing a noise component in the signal frequency band thereof is digitized by an A/D converter circuit. CONSTITUTION:A digital value of the signal value of an input signal at each sampling time is outputted at this time from an A/D converter circuit 2, and the digital value generated as a time series sequentially is inputted to a Fourier transform means 4. Then, each of spectral data at the sampling time is outputted sequentially from the means 4, and an added-up value of each spectral data in a predetermined frequency band out of each of the aforesaid spectral data is outputted from an addition means 6. The added-up value outputted sequentially from the means 6 at each sampling time is inputted to a moving average value generating means 8 and an average value at each sampling time is outputted sequentially from the means 8. The average value at each sampling time is used for detecting a signal containing a noise component in its signal detection frequency band.

Description

[Detailed Description of the Invention] [Summary] For detecting a signal containing a noise component in the same frequency band as a time-varying signal, the frequency of the signal -! Regarding the signal detection method that uses conversion to the 1F range, the purpose is to eliminate the influence of noise components whose frequency band is part or all of the frequency band of the signal to be detected, and to ensure reliable detection of the signal to be detected. An analog/digital conversion circuit for signals containing 11 frequencies in the signal frequency range, and a digital value time series part of each sampling time required for Fourier transformation from the analog/digital conversion circuit are used to sequentially convert each of the spectral data. A Fourier transform means that generates a Fourier transform, an addition means that adds each spectrum data within a predetermined frequency band at each sampling time, and a time series part of the total value necessary for generating an average value at each sampling time. The moving average value generating means sequentially generates average values, and the average value at each sampling time is used for detecting signal generation.

[Industrial application field]

The present invention relates to a signal detection method that uses conversion of a signal into a frequency domain to detect a signal that includes a noise component in the same frequency band as a temporally varying signal.

In the field of signal measurement, a signal to be measured usually contains a noise component, so that the signal to be measured is measured after taking steps to remove the noise component.

[Conventional technology]

Conventional techniques for removing noise components include filters (low-pass filters) that have blocking characteristics for noise components outside the frequency band of the signal to be measured.

The noise component is removed using a high-pass filter (high-pass filter).

[Problem to be Solved by the Invention] This filtering technique is effective when the noise component is outside the frequency band of the signal to be measured, but when the frequency band of the noise component is also within the frequency band of the signal to be measured. At that point, the filter technique no longer serves its purpose.

The present invention was created in view of such problems, and it is possible to reliably detect a signal to be detected by eliminating the influence of noise components whose frequency band is part or all of the frequency band of the signal to be detected. The purpose is to provide a signal detection method that can

[Means to solve the problem]

FIG. 1 shows a block diagram of the principle of the present invention. As shown in the figure, the present invention provides an analog/digital conversion circuit 2 that digitizes a signal that includes noise components in the signal frequency band.
The spectrum at each sampling time is calculated by using, at each sampling time, a digital value time series part necessary for generating each of the necessary spectral data regarding the signal frequency band of the signal from the analog/digital conversion circuit 2. Fourier transform means 4 that sequentially generates each piece of data, and addition means 6 that adds each spectrum data within a predetermined frequency band among the spectrum data at each sampling time of the analog/digital conversion circuit 2. and a moving average value generating means 8 that sequentially generates the average value at each sampling time by using the total value time series part necessary for generating the average value at each sampling time from the adding means 6 at each sampling time. The average value generated by the moving average value generating means 8 at each sampling time is used for detecting signal generation.

(Function) For each sampling time, the input signal is output from the analog/digital conversion circuit 2 as a digital value of the signal value at that sampling time.

Digital values sequentially generated as a time series are input to the Fourier transform means 4. Of the input digital value time series, the digital value time series portion necessary to generate each of the necessary spectral data within the signal frequency band of the input signal at the sampling time is determined at each sampling time. Each of the spectral data used at the sampling time is sequentially outputted from the Fourier transform means 4. The total value of each spectral data within a predetermined frequency band among the spectral data at each sampling time is outputted from the adding means 6.

The total value sequentially outputted from the adding means 6 at each sampling time is inputted to the moving average value generating means 8. Of the inputted total value time series, the total value time series part necessary for generating the average value at each sampling time is used for each sampling time, and the average value at each sampling time is calculated by the moving average value generating means 8. are output sequentially from

The average value at each sampling time is used to detect a signal containing a noise component in the signal detection frequency band. Used to detect incoming calls.

Since the above-mentioned noise component does not affect the detection,
Signals can be detected reliably.

〔Example〕

FIG. 2 shows an embodiment of the present invention. In this figure, 2
is an analog/digital conversion circuit that converts a signal including a noise component in the signal frequency band, such as a P-wave signal of an earthquake wave, into a digital value (see a in FIG. 3), and its sampling period is 1/2 fo. fo is the upper limit frequency of the frequency band of the signal to be detected. Reference numeral 12 denotes a memory circuit, which sequentially stores sampling digital values for a predetermined number of sampling circuits m (for example, 512) from the sampling time in the analog/digital conversion circuit 2 at each sampling time (FIG. 3(A)). (see b). The m is determined by the number of spectrum data in a predetermined frequency range. 13 is a Fourier transform circuit,
At each sampling time, the sampling digital value X(L) (third
(see a in FIG. 3(A)) and m sampling digital values from the memory circuit 12 (see b in FIG. 3(A)), and m+1 spectral data (see FIG. (See A) C). These spectral data are stored in the memory circuit 14. Reference numeral 15 denotes an adder circuit which extracts spectral data within a predetermined frequency band (see d in FIG. 3(A)) from among the spectral data stored in the memory circuit 14, and calculates the total value at each sampling time. a(t) (see C in FIG. 3(A)) is generated. The total value a(
Each time L) is input, the second
The total value for a predetermined number of α minutes shifts out the oldest total value of the storage column (time series) starting with the oldest total value, and the total value at the end of the storage column is calculated. The storage column is updated at each sampling time (see r in FIG. 3A) to store the total value of each sampling time input as . 17 is an average calculation circuit,
α total values a(L-Δt), a(t-2Δt), . . . given from the memory circuit 16 at each sampling time
・, the oldest value a(L-αΔL) of a(t-dΔL)
) is replaced with the total value a (L) from the adder circuit 15, and the arithmetic mean value Δ of the α total values (see g in FIG. 3(A)) is output at each sampling time.
In other words, the average calculation circuit 17 outputs a moving average value. Reference numeral 18 denotes a comparison circuit which looks at the magnitude relationship with a (L) described above and outputs a signal indicating that a signal has arrived if a (t) is greater than a specified level.

The memory circuit 12 and the Fourier transform circuit 13 in the above configuration correspond to the Fourier transform means 4 in FIG. 1, the memory circuit 14 and the addition circuit 15 correspond to the addition means 6 in FIG.
The memory circuit 16 and the average value calculation circuit 17 correspond to the moving average value generation means 8 in FIG.

The operation of the present invention in the above configuration will be explained below.

The signal input to the analog/digital conversion circuit 2 is converted into a digitized signal value at each sampling time. The digital values at each sampling time are stored in the memory circuit 12 for the required number of sampling m from the sampling time, excluding the oldest digital value at the beginning of the m digital value time series at each sampling time. The digital values at each sampling time are connected to the end and stored (see b in FIG. 3(A)).

Then, at each sampling time, each piece of spectral data is output from the Fourier transform circuit 13 which receives and receives each digital value of the memory circuit 12 and the digital value from the analog/digital conversion circuit 2, and is stored in the memory circuit 14 ( For example, if the human signal is a P-wave signal of a seismic wave, the spectrum in the range of 0.511z to 101[z] A total value for each piece of data is output from the adder circuit 15. The total value is sequentially stored in the memory circuit 16 as described above, and the average value at each sampling time is stored in the adding circuit 16.
The average calculation circuit 17 sequentially outputs the total value and each of the average calculation target total values from the memory circuit 16 (see 1 in FIG. 3(A)). A(L-Δ1) in Figure 3(A)
) (see h in FIG. 3(A)) indicates the arithmetic mean at the sampling time immediately before the sampling time when A (L) was output.

When the total value from the addition circuit 15 at a sampling time is greater than a predetermined value (specified level) with respect to the average value at that sampling time, the comparison circuit 18
A P-wave signal detection signal (trigger signal) is output from.

For example, the average value at sampling time L-+ is <A(L-1) as shown in FIG. 3(B), and this value almost represents a noise component. In this input signal state, when the signal S containing the noise component is input at the next sampling time, the average value becomes A (L). This average value Δ(1) is the average value A (L - 1) is larger, but still represents the signal background level. That's it.

a(L) at the sampling time has a value larger than the signal background level. This a (L) and A(t
) is determined by the comparison circuit 18, and the above-mentioned detection signal is obtained.

Note that the detection signal may be generated from an average value at a sampling time and an average value at a sampling time one sampling cycle before the sampling time. The average value may be anything other than the arithmetic average value as long as it can represent the background level of the signal, and the term signal frequency band used above also includes a single signal frequency. It will be clear from the above description of the invention that the invention may be interpreted as follows.

(Effects of the Invention) As described above, according to the present invention, even if the detection target signal contains noise having the same frequency component as the signal frequency band, the detection target signal can be reliably detected. I can do it.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the principle of the present invention, FIG. 2 is a diagram showing an embodiment of the present invention, and FIG. 3 is an explanatory diagram of the embodiment of the present invention. 1 and 2, 2 is an analog/digital conversion circuit, 4 is a Fourier transform means (memory circuit 12, Fourier transform circuit 13), 6 is an addition means (memory circuit 14, addition circuit 15), and 8 is a moving circuit. This is an average value generation means (memory circuit 16, average value calculation circuit 17).

Claims (1)

[Claims] (1) An analog/digital conversion circuit (2) that digitizes a signal that includes a noise component in the signal frequency band; and necessary spectral data about the signal frequency band of the signal from the analog/digital conversion circuit (2). Fourier transform means (4) that sequentially generates each of the spectral data at each sampling time by using the digital value time series part necessary for the generation of each sampling time, and the analog/digital conversion circuit (2).
) adding means (6) for adding each spectral data within a predetermined frequency band among the respective spectral data at each sampling time; moving average value generation means (8) that sequentially generates the average value at each sampling time using the time series part of the total value necessary for generation at each sampling time, and generates a signal from the average value at each sampling time. A signal detection method characterized by being used for the detection of.