JPS60144669A - Detector for variation in signal frequency - Google Patents

Abstract

PURPOSE:To detect frequency variance which is nearly actual frequency variation by amplifying the progressive averaged result of another frequency component when the progressive averaged result of a signal tends to decrease, and comparing it with the progressive averaged result which one analytic cycle before. CONSTITUTION:An acoustic input 11 is frequency-analyzed by a frequency analyzing circuit 1 and a progressive averaged curcuit 2 calculates the progressive mean of every frequency component. A memory circuit 3 is stored with the maximum value of the progressive averaged result which is one analytic cycle before and its frequency, and a coefficient calculating circuit 4 divides the value stored in the memory circuit 3 by the up-to-date progressive averaged result to employ ''1'' as a coefficient when the quotient is <=1 or the value obtained by multiplying the quotient by a constant as a coefficient when the quotient is >1. Then, a coefficient multiplying circuit 5 multiplies the progressive averanged result of the maximum value among up-to-date progressive averaged result except a progressive average corresponding to the signal frequency stored in the circuit 3 by the obtained coefficient, and a comparing circuit 6 compares it with the progressive averaged result which is one analytic cycle before to detect frequency variation.

Description

TECHNICAL FIELD The present invention relates to a signal frequency change detection device, and more particularly, to a signal frequency change detection device for detecting a change in the frequency of an underwater acoustic signal from a constant frequency to another frequency. Regarding a detection device.

Description of the Prior Art Conventionally, this type of frequency change detection involves frequency analysis of an acoustic input one after another in a predetermined frequency band and analysis period, cumulative averaging of the same frequency components, and the cumulative average result. It is determined that the signal frequency has changed when the maximum frequency is different from that one analysis cycle ago.

To further explain using figures, FIG. 1 shows a part of the frequency spectrum before and after the signal frequency changes from a certain frequency to another frequency.

In Fig. 1, time tn, tn+1 t tn+2+
-) The frequency spectrum at each time of tn+9 is shown, and the horizontal direction of each frequency spectrum shows the frequency, and the vertical direction shows the level, respectively. In addition, in FIG. 1, Xn, Xn+1. ..., Xn+9 is the level of the frequency analysis result at the frequency foK before the change,
Among these, Xn, Xnl, -., Xn+4 are signal levels, xn+s.

Xn+6..., Xn+9 are noise levels. Also, in Figure 1, %'/"e 'i"' +...
Xn+9 is the level of the frequency analysis result at the frequency f1 after the change, and yn, Xn+1,...
, Xn+4 is the noise level, Xn+5°Xn+4,
..., Xn+9 is the signal level. FIG. 1 shows that there was a frequency change between times tn+4 and Xn+5.

Conventional devices of this type for such signals have the disadvantage that the detection of frequency changes is delayed compared to the actual change. This will be explained with reference to FIG.

FIG. 2 shows the transition of the cumulative average level at each time with a cumulative number of 5 for the example shown in FIG. In FIG. 2, the mark indicates the cumulative average level of frequency f, and the mark X indicates the cumulative average level of frequency f1.

Also, in Figure 1, An+'4, An+5,...
An+9 is the value of the cumulative average level of the frequency fo at each time, Bn+4, Bn+5,...
Bn+9 is the value of the cumulative average level of frequency f at each time, and Aj and Bj are each given as follows.

Note that frequency components other than frequencies f0 and f1 in FIG. 1 are noise, and the cumulative average result is Aj.

Since both Bj and Bj are small, the wax is omitted in FIG. In Figure 1, if the signal level and noise level are each approximately constant, then Xn + 4 keys yn + s*yn + 6 keys yn + 7)
Xn+5 in Xn+6 in Xn+7 in yn+4 key yn+4
...... Since (3), the following equation (Hiroshi) holds true.

Bn+7=7 (yn+3+yn+4+yn+s+yn
+6+yn+7)> An+7=7 (xn+t+xn
+4-4-xn+4+xn+6+xn+7)---(p
) As shown in the above equation, although the frequency actually changes between times tn+4 and tn+5,
In conventional devices of this kind, the time tn+7 is later than that.
Detected in Generally, it is rare for a single underwater acoustic signal to have a good S/N ratio, and in order to improve the signal to noise ratio by 8/N, it is essential to take a cumulative average. Although the example in FIG. 2 shows the case where the cumulative number is 3, it is clear that even in other cases where the cumulative number is accompanied by a cumulative average, a time delay until the frequency change is detected cannot be avoided.

As mentioned above, conventional devices of this kind have the disadvantage that the detection of frequency changes in a signal is delayed after the actual change has occurred, and as a result, the information indicated by the frequency changes is There was a large error in real-time measurement of the closest time of the sound source due to frequency changes.

Purpose of the Invention □The present invention has been made in view of the above-mentioned conventional circumstances. Therefore, the purpose of the present invention is to eliminate the above-mentioned drawbacks and to reduce the cumulative average result of the signal by comparing the value K before the analysis cycle. If a trend is shown, the cumulative average results of other frequency components are amplified and 1
The objective is to provide a new detection device that can detect frequency changes at a point closer to the actual frequency change than conventional devices, rather than comparing it with the cumulative average result that was regarded as a signal until before the analysis cycle. .

Structure of the Invention In order to achieve the above object, a signal frequency change detection device according to the present invention is a signal frequency change detection device for detecting that the frequency of an acoustic signal emitted by a sound source changes from a constant frequency to another frequency. , a frequency analysis circuit that analyzes frequencies one after another in a predetermined frequency band and analysis period; a cumulative averaging circuit that cumulatively averages the analysis results of the frequency analysis circuit for each same frequency component; a memory circuit for storing the frequency of the signal and its cumulative average result; and dividing the cumulative average result stored in this memory circuit by the latest cumulative average result corresponding to the frequency stored in the memory circuit; If the quotient is less than or equal to l, the coefficient is set to l, and if the quotient exceeds 7, the coefficient is multiplied by a preset constant of 7 or more. A coefficient multiplication circuit that multiplies the largest one by the coefficient determined by the coefficient calculation circuit and compares the multiplication result obtained by this coefficient multiplication circuit with the cumulative average result of the signal, and determines whether the cumulative average result of the signal is better. and a comparator circuit that generates an output when the voltage is small.

Next, a preferred embodiment of the present invention will be specifically explained with reference to the drawings.

FIG. 3 is a block diagram showing an embodiment of the signal frequency change detection device according to the present invention. An embodiment of the present invention shown in FIG. 3 includes an input terminal //, a frequency analysis circuit 11, an accumulating average circuit λ, a memory circuit 3, a coefficient calculation circuit DA, a coefficient multiplication circuit S, a comparison circuit 6, and an output terminal 61. It consists of

The acoustic input input at the input terminal // is sent to the frequency analysis circuit l
sent to. Frequency analysis circuit l is A/D conversion, high speed 7-
It is equipped with Rie transform, etc., and performs frequency analysis of acoustic input.

The cumulative averaging circuit λ cumulatively averages the output of the frequency analysis circuit for each frequency component. The memory circuit 3 stores the maximum value of the cumulative average result one analysis cycle ago and the frequency at which the maximum value is taken, that is, the signal frequency. On the other hand, the coefficient multiplication circuit divides the previous cumulative average result stored in the memory circuit 3 by the latest cumulative average result, and the quotient is l
In the following cases, l is used as a coefficient, and when the quotient exceeds /, the quotient is multiplied by a preset constant and the 1c value is used as a coefficient. Next K, coefficient multiplication circuit! Then, among the latest cumulative average results excluding the cumulative average corresponding to the signal frequency stored in the memory circuit 3, the coefficient output from the allocation coefficient calculation circuit 4 is added to the cumulative average result of the maximum value. Multiply.

Thereby, when the cumulative average result of the signal frequency before the change shows a decreasing tendency, it is possible to amplify the cumulative average result of the im signal frequency after the change. This will be explained with reference to FIG.

Fig. 1 shows the transition of the cumulative average results at each time for the frequencies fO and fl in the example of Fig. 1. 9th
The x marks and marks in the figure have the same meanings as in Fig. 2. The circle mark in FIG. 9 indicates the output of the coefficient multiplication circuit S for the frequency f1. Note that the frequency f in FIG. 1 and frequency components other than f1 are all noise levels, and the cumulative average result is the frequency f. Since it is smaller than the respective cumulative average results of fl and fl, it is omitted in FIG.

At time tn4-5 in FIG. 1, the coefficient calculation circuit DA first performs the next division.

From the diagram, An+4) Anu5, so this quotient is greater than /. Therefore, by multiplying the preset constant K by this quotient, the output kn+5 of the coefficient calculation circuit Da is obtained as follows. Similarly, the outputs kn+6 and kn+7 of the coefficient calculation circuit da at time in+61 tn+7 are as follows.

Therefore, the coefficient multiplier circuit multiplies time tn+51 'Gn+6 r tn+7 by 2! The output of is B'n+5, B'n
+6 and B'n+7 are each as follows.

In this way, in order to obtain B'i ) Bi, the comparator circuit 6
When comparing B'i and A1, compared to the conventional comparison of B1 and A1, B'1 is
) Ai, which is detected earlier than in the past, and its output is generated at the output terminal 61.

Although Fig. 6 shows how the frequency change can be detected at time tn+4, it is also possible to detect it at an earlier point in time by appropriately setting the value of the constant.

As described in detail, the present invention is equipped with a means for amplifying and determining other frequency components when the cumulative result of frequency components of a frequency-analyzed signal shows a decreasing tendency. This has the effect of detecting signal frequency changes at an early stage.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a frequency spectrum with a frequency change of a signal, FIG. 2 is a diagram showing calculated values in a conventional method, and FIG. 3 is a block diagram showing an embodiment of the present invention.
The figure is a diagram showing calculated values in one embodiment of the present invention shown in FIG. 3. l/...input terminal, l...frequency analysis circuit, λ...
・Cumulative average circuit, 3...memory circuit, da...coefficient calculation circuit,! ... Coefficient multiplication circuit, 6... Comparison circuit, Otsu C... Output terminal Patent applicant NEC Corporation Representative Patent attorney Yutabe Kumagai Foil 1 Flashing pile 4 Diagram

Claims (1)

[Claims] A signal frequency change detection device that detects when the frequency of an acoustic signal emitted by a sound source changes from a certain frequency to another frequency includes a frequency analysis circuit that sequentially analyzes frequencies in a predetermined frequency band and analysis period, and A cumulative averaging circuit that cumulatively averages the frequency analysis results of the analysis circuit for each same frequency component; a memory circuit that stores the frequency of the signal obtained I analysis period before and the cumulative average result; Divide the cumulative average result corresponding to the frequency stored in the memory circuit by the latest cumulative average result corresponding to the frequency stored in the memory circuit, and if the quotient is less than l, set the coefficient to 7, and if the quotient exceeds l, divide the quotient by the latest cumulative average result corresponding to the frequency stored in the memory circuit. A coefficient calculation circuit whose coefficient is a value multiplied by a preset constant of 7 or more, a coefficient multiplication circuit which multiplies the value of the coefficient by the maximum value of the cumulative average results excluding signals, and this coefficient multiplication circuit. A signal frequency change detecting device comprising: a comparison circuit that compares the obtained multiplication result with the cumulative average result of the signal and generates an output when the cumulative average result of the signal is smaller.