KR101740363B1 - Wake detectors and wake detecting method thereof - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wake-up detector for detecting a wake of a ship moving in water and / or water, and a wake detection method thereof. The trajectory detector includes: a signal generator for generating a continuous wave having a single frequency as a transmission signal; A signal receiving unit for receiving, as a received signal, a signal that is reflected from the minute bubbles generated by the target by the transmission signal; A cepstrum calculator for calculating a cepstrum signal of the transmission signal and a cepstrum signal of the reception signal; A channel estimator for calculating an estimated value of an underwater channel using a cepstrum signal of the transmission signal and a cepstrum signal of the reception signal; Extracting a channel component by an anti-signal from the estimated value, and estimating the anti-signal using the extracted channel component; And an output unit for outputting the estimated alert signal.

Description

≪ Desc / Clms Page number 1 > WAKE DETECTORS AND WAKE DETECTING METHOD THEREOF &

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wake-up detector for detecting a wake of a ship moving in water and / or water, and a wake detection method thereof.

Faster and more accurate detection of targets (or vessels and vessels that move water or water) at sea is a critical challenge in marine detection technology. Sonar is the most widely used sonar, sonar, magnetic, electromagnetic wave, optical, etc.

There are two main methods for detecting ships: active detection and manual detection. Active detection is a method of generating a sound wave to analyze and detecting signals reflected on a target, and passive detection is a method of analyzing and detecting signals of a mechanical sound emitted from a target. Active detection suffers from degradation of detection performance due to reverberation and sounder expiration. Passive detection is characterized by difficulty in achieving high signal-to-noise ratio (SNR) due to advances in radiation noise reduction technology. have.

The present invention is directed to solving the above-mentioned problems and other problems.

Another object is to provide a wake detector capable of detecting a wake of a moving object at sea and its wake detection method.

Another object of the present invention is to provide a trajectory detector and its trajectory detection method capable of detecting the trajectory of a target even in a case where the amount of minute bubbles generated by a moving object in the sea is small.

According to an aspect of the present invention, there is provided a trajectory detector including: a signal generator for generating a continuous wave having a single frequency as a transmission signal; A signal receiving unit for receiving, as a received signal, a signal that is reflected from the minute bubbles generated by the target by the transmission signal; A cepstrum calculator for calculating a cepstrum signal of the transmission signal and a cepstrum signal of the reception signal; A channel estimator for calculating an estimated value of an underwater channel using a cepstrum signal of the transmission signal and a cepstrum signal of the reception signal; Extracting a channel component by an anti-signal from the estimated value, and estimating the anti-signal using the extracted channel component; And an output unit for outputting the estimated alert signal.

According to one embodiment, the navigation detector further includes an anti-signal detection unit for comparing the power of the estimated anti-aliasing signal with a predetermined reference, and selectively outputting the estimated anti-aliasing signal to the output unit according to the comparison result .

According to one embodiment, the anti-signal detection unit may calculate an average value for a predetermined time with respect to the power of the estimated anti-signal, and, when the calculated average value is larger than the preset reference, Can be output to the output unit.

According to one embodiment, the wake-up signal estimator may remove a channel component due to the sea level reflection signal from the estimated value using a threshold value.

According to an exemplary embodiment, the threshold value may be set differently according to the reception environment of the received signal.

According to an embodiment, the channel estimator may calculate a cepstrum signal of the underwater channel using a difference between a cepstrum signal of the received signal and a cepstrum signal of the transmit signal, The estimated value can be calculated through an inverse cepstrum computation on the strum signal.

In addition, one embodiment of the present invention for solving the above-mentioned problems relates to a method of detecting a wake of a wake-up detector. The trajectory detection method includes generating a continuous wave having a single frequency as a transmission signal; Receiving the transmission signal as a reception signal, the signal being reflected from the minute bubbles generated by the target; Calculating a cepstrum signal of the transmission signal and a cepstrum signal of the reception signal; Calculating an estimated value of an underwater channel using a cepstrum signal of the transmission signal and a cepstrum signal of the reception signal; Extracting a channel component by an anti-signal from the estimated value, and estimating the anti-aliasing signal using the extracted channel component; And outputting the estimated alert signal.

According to an exemplary embodiment, the method may further include comparing the power of the estimated anti-aliasing signal with a preset reference, and selectively outputting the estimated anti-aliasing signal to the output unit according to the comparison result.

According to an embodiment, the step of outputting the estimated anti-call signal to the output unit may include: calculating an average value for a predetermined time with respect to the power of the estimated anti-call signal; And outputting the estimated alarm signal to the output unit when the calculated average value is greater than the predetermined reference.

According to an embodiment, the estimating of the anti-signal may remove a channel component due to the sea level reflection signal from the estimated value using a threshold value.

According to an exemplary embodiment, the threshold value may be set differently according to the reception environment of the received signal.

According to an embodiment, the step of calculating the estimated value may include calculating a cepstrum signal of the underwater channel using a difference between a cepstrum signal of the received signal and a cepstrum signal of the transmitted signal. And computing the estimated value through an inverse cepstrum computation on the cepstrum signal of the underwater channel.

The effect of the image enhancement method according to the present invention will be described as follows.

According to the present invention, in order to detect a signal of a ship, a cepstrum is used to detect only a signal transmitted from the sum of the coherent sea level reflection signal and the call signal in the time and frequency domain, It is possible to effectively perform the wake detection even when the power of the anti-signal is low and the wake detection is difficult only by the power of the received signal. Therefore, the detection probability of the anti-collision signal can be improved when the amount of bubbles generated by the ship is small.

The effects obtained by the present invention are not limited to the above-mentioned effects, and other effects not mentioned can be clearly understood by those skilled in the art from the following description will be.

1 is a graph for illustrating the general shape of a signal received at the wake detector 100;
FIG. 2 is a graph showing the composition of a component due to sea level reflection signal and the component of an anti-signal signal in an underwater channel. FIG.
FIG. 3 is a conceptual diagram illustrating a process of obtaining a Cepstrum signal from an arbitrary signal included in a time domain; FIG.
4 is a block diagram illustrating a wake detector 100 in accordance with an embodiment of the present invention.
FIG. 5 is a flowchart for explaining a method of detecting a wake of the wake detector 100 of FIG. 4;
FIG. 6 is an exemplary diagram illustrating an example of a received signal and a generated anti-signal, and an estimated underwater channel and an anti-signal in the process of separating a sea level signal using cepstrum.
Figure 7 is a block diagram of signal processing in wake detection using cepstrum.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, wherein like reference numerals are used to designate identical or similar elements, and redundant description thereof will be omitted. The suffix "module" and " part "for the components used in the following description are given or mixed in consideration of ease of specification, and do not have their own meaning or role. In the following description of the embodiments of the present invention, a detailed description of related arts will be omitted when it is determined that the gist of the embodiments disclosed herein may be blurred. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. , ≪ / RTI > equivalents, and alternatives.

Terms including ordinals, such as first, second, etc., may be used to describe various elements, but the elements are not limited to these terms. The terms are used only for the purpose of distinguishing one component from another.

It is to be understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, . On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between.

The singular expressions include plural expressions unless the context clearly dictates otherwise.

In the present application, the terms "comprises", "having", and the like are used to specify that a feature, a number, a step, an operation, an element, a component, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

The present invention relates to a method for detecting a ship's wake in a wake detector, which separates a sea level reflection signal component from a received signal including a sea level reflection signal, a wake reflection signal, and a noise signal using a cepstrum Thereby extracting only the power of the enemy signal.

A ship moving in water and / or water creates microbubbles during navigation, and the flow of these microbubbles is called wake. Here, the ship includes all military and / or non-military vessels and includes warships, destroyers, torpedo boats, small vessels, aircraft carriers, and naval ships.

In addition to active and passive detection, a technique for generating a high frequency acoustic signal to detect a target using signals reflected from minute bubbles generated by the target is called wake detection. The trajectory detection is characterized in that it can be detected irrespective of the type of the target without being influenced by the acoustic deception device. The present invention relates to such trajectory detection.

Hereinafter, the characteristics of the received signal received by the navigation detector will be described.

S [n] consists of the sea level reflection signal, the anti-signal w [n], and the noise signal g [n], where s [n] is the received signal received by the navigation detector, Can be expressed.

When the signal is normally received at the wake detector, the received signal y [n] has a feature that it includes the sea level reflected signal s [n]. The sea level reflection signal s [n] is characterized in that it has a large value in a short time as shown in FIG.

On the other hand, the anti-signal w [n] exists over a relatively long period of time and is received only when there are minute bubbles generated by the ship's voyage. Also, the magnitude of the signal w [n] depends on the amount of microbubbles. The simplest way to detect this signal w [n] is to use the power of the received signal y [n].

If the magnitude of the wake signal w [n] is large and has a size similar to or larger than the sea level reflection signal s [n], the power of the wake signal w [n] Detecting w [n] is not difficult.

However, when the magnitude of the signal w [n] is relatively small compared to the sea level reflection signal s [n], the difference between the power of the received signal y [n] It is difficult to judge the presence or absence of the anti-signal w [n]. Therefore, in this case, a high detection probability can be obtained only by extracting the power for the anti-signal w [n] existing after separating the sea level reflection signal s [n].

However, since the signal w [n] is coherent with respect to the sea level reflection signal s [n] in terms of time and frequency, it is difficult to completely distinguish it by general time or frequency analysis.

Expressing the received signal y [n] of the trajectory detector in terms of the channel, Equation (1) can be expressed by Equation (2) below using the convolution of the transmitted signal and the channel.

Here, x [n] represents a continuous wave (CW) having a single frequency, h [n] denotes an underwater channel reflecting a transmitted signal, and * denotes a convolution operation.

As shown in FIG. 2, the sea level component is represented by one sample having a large value and the component by the anti-sea signal is represented by the sea level component Lt; RTI ID = 0.0 > a < / RTI > small value. By using these features to estimate the underwater channel and to separate the values corresponding to the sea surface components, it is possible to obtain the relative signals relatively accurately compared with the method by time or frequency domain analysis.

Channel estimation is commonly used in wireless communication, where channel estimation in wake detection is different from channel estimation in wireless communication in that the signal used for transmission is a narrowband signal. In the present invention, a cepstrum is used as a method for obtaining an underwater channel in a navigation detector using a narrowband signal.

Cepstrum is a word derived from the second-order frequency spectrum of G (t) which is Fourier-transformed again the spectrum G of the time domain function G (t). The concepts corresponding to frequency, amplitude and phase in the frequency domain are called quefrency, lampitude, and saphe in the cepstral domain, respectively. The concept corresponding to the filtering in the time domain or the frequency domain is called liftering. Cepstrum analysis is useful for analyzing a signal whose frequency spectrum has periodicity, and can be done by taking a log of the frequency spectrum and then performing a Fourier inverse transform.

Hereinafter, the cepstrum will be described in more detail.

Cepstrum is the result of Fourier transform, logarithm, and inverse Fourier transform from the time domain signal.

The spectrum of an arbitrary signal x [n] can be obtained by using Fourier transform as shown in the following equation (3).

When the logarithm of the frequency domain signal obtained from the equation (3) is taken, it can be expressed by the following equation (4).

(Cepstrum signal) x _c [n] for an arbitrary signal x [n] using an inverse Fourier transform operation from the equation (4).

FIG. 3 shows a process of obtaining cepstrum signal x _c [n] from an arbitrary signal x [n]. From the cepstrum operation described above, the signals in the convolution relationship in the time domain are expressed as products in the frequency domain and are expressed as sum in the cepstral domain by the log Using these features, we can separate signals in the convolution relationship into sum signals in the cepstral area. It is possible to separate the transmission signal and the channel signal by using this, and separating the convoluted signal into a sum signal or the like is called deconvolution.

In the case of cepstrum, it is common to use a cepstrum using a complex log to restore the original signal by maintaining the phase information. In the present invention, since it is intended to obtain the estimated signal power rather than the original signal restoration, there is no restriction on the cepstrum and the cepstrum.

FIG. 4 is a block diagram illustrating a wake detector 100 according to an embodiment of the present invention, and FIG. 5 is a flowchart illustrating a wake detection method of the wake detector 100 of FIG.

4, the navigation detector 100 according to the present invention includes a signal generator 110, a signal receiver 120, a cepstrum calculator 130, a channel estimator 150, 160, an emergency signal detection unit 170, and an output unit 180.

First, the signal generator 110 generates a transmission signal x [n] that is a continuous wave (CW) having a single frequency (S510). The transmission signal corresponds to time in the time domain.

Next, the signal receiving unit 120 receives the signal, which is reflected from the minute bubbles generated by the target, as a transmission signal, as a reception signal (S520). S [n] is composed of a sea level reflection signal, an anti-signal signal w [n], and a noise signal g [n], and expressed by Equation (1).

Next, the cepstrum calculator calculates the cepstrum signal of the transmission signal and the cepstrum signal of the reception signal (S430).

The cepstrum calculator may include a received signal envelope calculator 130 and a transmitted signal envelope calculator 140 so that faster calculations can be performed. The received signal cepstrum calculator 130 calculates the cepstrum signal x _c [n] of the received signal using Equation (2) to Equation (5). The transmission signal cepstrum computing unit 140 computes the cepstrum signal y _c [n] of the transmission signal using Equations (2) to (5).

Next, the channel estimator 150 calculates an estimation value of the underwater channel using the cepstrum signal of the transmission signal and the cepstrum signal of the reception signal (S540). More specifically, the step of calculating the estimated value may include calculating a cepstrum signal of the underwater channel using a difference between a cepstrum signal of the received signal and a cepstrum signal of the transmitted signal, And computing the estimated value through an inverse cepstrum computation on the cepstral signal of the channel.

Assuming that there is no noise signal, Equation (7) can be obtained through the process of Equation (6) below.

In this case, F ^{- 1} [·] denotes an inverse Fourier transform, and a cepstrum signal y _c [n] of the received signal is converted into a cepstrum signal x _c [n] And the cepstrum signal h _c [n] of the underwater channel.

Since the cepstrum signal x _c [n] of the transmission signal can be obtained from the transmission signal x [n], the cepstrum signal of the underwater channel can be expressed by Equation (8) below.

The inverse cepstrum computation of the cepstrum signal h _c [n] of the underwater channel obtained from Equation (8) yields an estimated value of the underwater channel as shown in Equation (9) .

That is, the tracking channel estimator 160 separates the channel component of the sea level reflection signal having a large value in a narrow region using the threshold value to obtain only the navigation channel.

Next, the anti-signal estimation unit 160 extracts an anti-aliasing channel component from the estimated value and estimates the anti-aliasing signal using the extracted channel component (S550).

과 항적신호에 의한 채널성분

의 합으로 표현된다. 해수면 반사신호에 의한 채널성분은 항적신호에 의한 채널성분에 비해 큰 값을 가지므로, 문턱 값을 이용하여 해수면 반사신호에 의한 채널성분을 제거하면, 상기 수중채널에는 항적신호에 의한 채널성분만 남게 되고, 이를

라고 한다. 즉, 상기 추정 값에서 해수면 반사신호에 의한 채널성분을 문턱 값을 이용하여 제거함으로써, 항적신호에 의한 채널성분을 추출할 수 있게 된다.The underwater channel includes a channel component

And the channel component

. Since the channel component due to the sea level reflection signal has a larger value than the channel component due to the anti-signal, if the channel component due to the sea level reflection signal is removed using the threshold value, only the channel component due to the anti- And

. That is, by removing the channel component due to the sea level reflection signal from the estimated value using a threshold value, it is possible to extract the channel component by the anti-signal.

The threshold value may be set differently according to the reception environment of the received signal. For example, the threshold value may be set to a first threshold value in a non-exposure environment, and may be set to a second threshold value in an environment where a non-exposure condition is not met. In another example, it may be set differently depending on at least one of the magnitude of the sea level reflection signal and the magnitude of the anti-signal signal. The threshold value according to the reception environment can be variously modified according to the embodiment.

The anti-signal estimation unit 160 may estimate the anti-aliasing signal as shown in Equation (10) through the convolution of the transmission signal and the channel component by the extracted anti-signal.

Next, the output unit 180 outputs the estimated alarm signal (S460). The output unit 180 may generate at least one of a display unit, a sound output unit, a haptic module, and a light output unit to generate an output related to a visual, auditory or tactile sense.

If it is determined that an alarm signal exists, the output unit 180 may output a notification indicating that the alarm signal is detected. The notification may include information such as a wake-up of the target calculated from the anti-aliens signal, a speed, and the like.

For example, when the display unit is included in the output unit 180, the display unit may display the wakeup of the target on the map based on the wake-up signal together with the notification information indicating that the anti-signal is detected.

The alarm signal detector 170 compares the estimated signal strength of the alarm signal estimated by the alarm signal estimator 160 with a predetermined reference and selectively outputs the estimated alarm signal to the output unit 180 ).

Specifically, the emergency signal detecting unit 170 calculates an average value for a predetermined time with respect to the power of the estimated alarm signal, and when the calculated average value is greater than the preset reference, (180).

For example, in order to determine the presence or absence of the anti-signal from the estimated anti-signal, the power of the anti-signal estimated as Equation (11) can be used as a verification statistic.

The anti-signal detection unit 170 determines that an anti-signal exists when the verification statistic λ of Equation (11) is greater than or equal to the threshold value τ, and determines that no anti-signal exists when the verification statistic is lower than the threshold value.

The alert signal detector 170 may determine the threshold value based on at least one of the magnitude of the anti-signal signal and the magnitude of the background noise. In other words, the threshold may vary depending on the situation.

6 shows an example of segregation of sea level reflection signal and detection of anti-clock signal using cepstrum. The intermediate results of the process of estimating the underwater channel from the received signal including the anti-signal and the sea-level reflection signal and obtaining only the anti-signal are shown.

In order to effectively detect the anti-signal w [n] in the trajectory detector, it is essential to separate the sea level reflection signal s [n] and the anti-signal signal w [n]. In the present invention, the channel including only the anti-signal w [n] is separated by separating the sea level reflection signal s [n] and the anti-signal signal w [n] through the underwater channel estimation and the sea level reflection signal s [ n] is completely separated to obtain a signal including only the signal w [n], and the power of the obtained signal is calculated to detect the signal w [n] even when the amount of minute bubbles generated by the trap is small .

The trajectory detector according to the present invention separates the received signal y [n] represented by the convolution of the transmitted signal x [n] and the underwater channel into a sum of the transmitted signal and the underwater channel using cepstrum, The cepstrum of the underwater channel is obtained by using the cepstrum of the signal, the time-domain underwater channel is estimated by the inverse cepstrum operation from the cepstrum, and the estimated underwater channel The channel including only the anti-signal is reconstructed by removing the sea level reflection signal component from the threshold value, and the anti-signal is obtained by using the convolution of the reconstructed channel and the transmission signal.

According to the present invention, in order to detect a signal of a ship, a cepstrum is used to detect only a signal transmitted from the sum of the coherent sea level reflection signal and the call signal in the time and frequency domain, It is possible to effectively perform the wake detection even when the power of the anti-signal is low and the wake detection is difficult only by the power of the received signal. Therefore, the detection probability of the anti-collision signal can be improved when the amount of bubbles generated by the ship is small.

The present invention can be embodied as computer-readable codes on a medium on which a program is recorded. The computer readable medium includes all kinds of recording devices in which data that can be read by a computer system is stored. Examples of the computer readable medium include a hard disk drive (HDD), a solid state disk (SSD), a silicon disk drive (SDD), a ROM, a RAM, a CD-ROM, a magnetic tape, a floppy disk, , And may also be implemented in the form of a carrier wave (e.g., transmission over the Internet). The computer may also include a wake detector (100).

Accordingly, the above description should not be construed in a limiting sense in all respects and should be considered illustrative. The scope of the present invention should be determined by rational interpretation of the appended claims, and all changes within the scope of equivalents of the present invention are included in the scope of the present invention.

100: wake detector 110: signal generator
120: Signal receiving unit 130: Received signal signal processing unit
140: transmission signal cepstrum computing unit 150: channel estimating unit
160: Anti-signal detection unit 170: Anti-signal detection unit
180: Output section

Claims (12)

A signal generator for generating a continuous wave having a single frequency as a transmission signal;
A signal receiving unit for receiving, as a received signal, a signal that is reflected from the minute bubbles generated by the target by the transmission signal;
A cepstrum calculator for calculating a cepstrum signal of the transmission signal and a cepstrum signal of the reception signal;
A channel estimator for calculating an estimated value of an underwater channel using a cepstrum signal of the transmission signal and a cepstrum signal of the reception signal;
Extracting a channel component by an anti-signal from the estimated value, and estimating the anti-signal using the extracted channel component; And
And an output unit for outputting the estimated anti-aliasing signal. The method according to claim 1,
Further comprising an anti-signal detection unit for comparing the power of the estimated anti-aliasing signal with a predetermined reference, and selectively outputting the estimated anti-aliasing signal to the output unit according to the comparison result. 3. The method of claim 2,
The anti-
Calculates an average value for a predetermined time with respect to the power of the estimated alarm signal, and outputs the estimated alarm signal to the output section when the calculated average value is larger than the preset reference. The method according to claim 1,
Wherein the trajectory signal estimating unit comprises:
And removing the channel component based on the sea level reflection signal from the estimated value using a threshold value. 5. The method of claim 4,
Wherein the threshold value is set differently according to a receiving environment of the received signal. The method according to claim 1,
Wherein the channel estimator comprises:
And calculating a cepstrum signal of the underwater channel by using a difference between the cepstrum signal of the received signal and the cepstrum signal of the transmit signal and performing a reverse cepstrum operation on the cepstrum signal of the underwater channel inverse cepstrum computation of the inverse cepstrum computation. Generating a continuous wave having a single frequency as a transmission signal;
Receiving the transmission signal as a reception signal, the signal being reflected from the minute bubbles generated by the target;
Calculating a cepstrum signal of the transmission signal and a cepstrum signal of the reception signal;
Calculating an estimated value of an underwater channel using a cepstrum signal of the transmission signal and a cepstrum signal of the reception signal;
Extracting a channel component by an anti-signal from the estimated value, and estimating the anti-aliasing signal using the extracted channel component; And
And outputting the estimated anti-aliasing signal. 8. The method of claim 7,
Wherein the step of outputting the estimated anti-
Comparing the estimated power of the anti-aliasing signal with a preset reference; And
And selectively outputting the estimated alarm signal to an output unit according to a result of the comparison. 9. The method of claim 8,
And outputting the estimated signal to the output unit,
Calculating an average value for a predetermined time with respect to the estimated power of the alarm signal; And
And outputting the estimated alarm signal to the output unit when the calculated average value is greater than the preset reference. 8. The method of claim 7,
Wherein the step of estimating the anti-
Wherein the channel component based on the sea level reflection signal is removed from the estimated value using a threshold value. 11. The method of claim 10,
Wherein the threshold value is set differently according to a receiving environment of the received signal. 8. The method of claim 7,
The step of calculating the estimated value includes:
Calculating a cepstrum signal of the underwater channel using a difference between a cepstrum signal of the received signal and a cepstrum signal of the transmit signal; And
And calculating the estimated value through an inverse cepstrum computation on the cepstrum signal of the underwater channel.

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