JPH037822Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a target movement direction display device used in a passive sonar device.

Conventional passive sonar equipment uses BDI (Bear-In), which directly compares the phases of received signals received by two separate receivers, to determine the target's moving direction.
ing Deviation Indicator), but they could only be used with a high S/N. Furthermore, rather than processing on the time axis, high S/N can be achieved by using the characteristic line spectrum emitted by the target.
Processing on the frequency axis has come to be performed because it has become possible to remove and identify the difference. In order to process this frequency axis, recent passive sonar devices use a receiver array with a large number of receivers to perform frequency analysis on the output signal of each directional beam created by phasing the received signal. and
From this analysis, the direction of the target is determined by comparing the strengths and weaknesses of the line spectrum emitted by the target.

However, the characteristic line spectrum emitted from the target is mostly in the low frequency range, and in order to obtain a directional beam width sufficient to determine direction in the low frequency range, the largest array of receivers is required. There was a drawback.

The purpose of this invention is to display the change in the phase difference of the target line spectrum that occurs between two separated receivers, so that only a small number of transducers are required, and at the same time, S/
To provide a display device in which the moving direction of a target can be known from a display pattern even when N is low.

The target movement direction display device of the present invention includes a plurality of omnidirectional wave receivers that are placed apart from each other and output signals according to sound waves from a received target, and a signal that each of the plurality of wave receivers outputs. a frequency analysis circuit that Fourier-transforms the signal and outputs each as a complex Fourier-transformed signal; an absolute value circuit that receives each of the complex Fourier-transformed signals, calculates an absolute value, and outputs the calculated absolute value; and one that receives each output of the absolute value circuit. a first indicator that displays changes in the absolute value with one as a frequency axis and the other as a time axis; and a first indicator that respectively receives the complex Fourier transform signal and displays a reference among the plurality of receivers for a specified line spectrum. a phase difference calculation circuit that calculates and outputs the phase with respect to the line spectrum of the receiver, and a change in the phase difference of the specified line spectrum with one of the outputs of the phase difference calculation circuit as the time axis; and a second display that respectively displays the first display output, and selects one of the target line spectra that is common to each display output and displays its frequency. It is configured to detect and input it to the phase difference calculation circuit for designation.

Next, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention. Omnidirectional receivers 1 and 2 arranged at a distance l output signals corresponding to the sound waves from the target. Amplifier 3 amplifies the output signals of receivers 1 and 2 to desired levels, and outputs the amplified signals. This output is input to a frequency analysis circuit 4 using FFH (Fast Fourier Transform). The frequency analysis circuit 4 performs Fourier transform on each of the input signals and outputs a complex Fourier transform signal having phase information. The absolute value circuit 5 calculates the absolute value of each complex Fourier transform signal and displays it on the spectrum display 6.
Send to. The spectrum display device 6 receives the output from the absolute value circuit 5, and displays changes in the absolute value, for example, in shading, with one axis being a frequency axis and the other being a time axis. The amplifier 3, frequency analysis circuit 4, absolute value circuit 5 and spectrum display 6 are as follows:
The outputs of receivers 1 and 2 are each divided into two channels for independent processing. By monitoring the display outputs of both channels of the spectrum display device 6, one of the characteristic line spectra from the target that appears in common in the display outputs of both channels can be detected.
One is selected visually, the frequency of the line spectrum is detected using a cursor or the like provided on the spectrum display 6, and the frequency is input to the phase difference calculation circuit 7 to designate the line spectrum. The phase difference calculation circuit 7 receives each complex Fourier transform signal output from the frequency analysis circuit 5, and calculates the phase difference of the line spectrum of the receiver 2 with respect to the specified line spectrum with respect to the line spectrum of the receiver 1 as a reference. is calculated and output to the phase difference display 8. The phase difference display 8 displays changes in phase difference with one axis as the time axis. The moving direction of the target can be determined from the pattern of changes in this phase difference.

Figure 2 is for the axis connecting the two receivers 1 and 2.
FIGS. 3 a to 3 c are diagrams showing display examples of the phase difference display 8 for the moving route shown in FIG. The changes in the phase difference of the paths with the same sign are indicated by the same sign. First, when moving parallel to the receivers 1 and 2, for example, 12, 14, 16 in FIG.
The movement course is from the left side of receiver 1 to receivers 1 and 2.
In this case, the phase difference is that the received signal to receiver 2 is delayed relative to receiver 1, so that receivers 1 and 2 are vertically bisected. It changes from 0 to progress on the line. On the contrary, 11,1
In the case of movement courses 3 and 15, the movement changes from advance to 0 and then to lag. A display example of this change in phase difference is shown in FIG. 3a. Examples of changes in phase difference when moving at right angles to the axes of receivers 1 and 2 and when moving at an arbitrary angle φ are shown in Figures 3b and 3c, respectively.
Shown below.

In this way, the moving direction can be determined depending on whether the change in phase difference crosses 0 and is a positive slope or a negative slope. The moving direction of a target moving perpendicular to the axis of the receiver can be determined from the phase difference between the two receivers, which are installed at right angles to the axes of receivers 1 and 2 and are combined at right angles. can. The maximum value of the phase difference θ varies depending on the frequency of the line spectrum and the distance l between the receivers. It is also possible to select several distances. However, since it is necessary to keep the phase advance and delay between the two receivers within π radians, the receiver spacing l is set so that the wavelength of the upper limit frequency of interest is λh.
Then, it is selected so that it becomes lλh/2.

According to the target movement direction display device of the present invention, as explained above, the change in the phase difference between the sound waves received by the two receivers is displayed in the line spectrum of the sound waves emitted by the target. As a result, only a small number of receivers are required, and the S/N ratio is low.
It is possible to know the direction of movement of the target relative to the receiver set even when the signal is low. In addition, with passive sonar equipment that performs frequency analysis using the FFT method, it is possible to easily know the target's movement by simply calculating the phase difference and adding a display section.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention.
FIG. 2 is a diagram showing the moving path of the target with respect to the axis connecting the receivers 1 and 2, and FIGS. be. 1, 2...Omnidirectional receiver, 3...Amplifier, 4
...Frequency analysis circuit, 5...Absolute value circuit, 6...
Spectrum display, 7... Phase difference calculation circuit, 8...
...Phase difference indicator.

Claims (1)

[Scope of utility model registration request] A plurality of omnidirectional wave receivers are placed apart from each other and output signals according to the sound waves from the received target, and the signals outputted by the plurality of receivers are Fourier-transformed and each is converted into a complex Fourier-transform signal. a frequency analysis circuit that receives the plurality of Fourier transform signals, calculates an absolute value, and outputs the calculated absolute value; a first indicator that respectively displays a change in absolute value; and a line spectrum of a receiver that receives the complex Fourier transform signal and is used as a reference among the plurality of receivers for a specified line spectrum. a phase difference calculation circuit that respectively calculates and outputs a phase difference; and a second display that receives the respective outputs of the phase difference calculation circuit and displays changes in the phase difference of the specified line spectrum with one of them as a time axis. monitors each display output of the first display, selects one of the target line spectra common to each display output, detects its frequency, and sends it to the phase difference calculation circuit. A target movement direction display device characterized by inputting and specifying.