JPH05273326A - Sonar receiver - Google Patents

Abstract

PURPOSE:To prevent an increase in the number of display screens and a decrease in monitoring ability in a sonar receiver even when the number of channels of the receiver increases at the time of displaying the frequency analyzed results of signals received through a plurality of channels. CONSTITUTION:A peak selector 4 extracts the maximum value of detection levels from frequency analyzed results obtained by means of FFT analyzers 11-1N of a plurality channels 1-N. Based on the extracted maximum value, an LOFAR display screen 6 displays. In addition, the channel from which the maximum value is extracted is stored in a channel storage device 5 and, while the channel is stored in the device 5, the history of the arriving direction of a target signal is displayed on a history display screen 7 based on the stored channel.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a sonar receiver, and more particularly to a passive sonar receiver for receiving sound waves emitted from an object and obtaining information about the object.

[0002]

2. Description of the Related Art A sonar receiving apparatus of this type detects a spectrum generated from a target sound source by performing frequency analysis on a received signal. In this sonar receiver, for example, a LOFAR (Low Frequency Analyzin) as shown in FIG.
g and Recording) display is used for visual display on recording paper or a CRT display screen.

That is, a frequency spectrum as an analysis result is displayed on the display coordinates of frequency versus elapsed time, where the horizontal axis is frequency f and the vertical axis is elapsed time. The signal strength in this case is displayed as brightness information.

In this LOFAR display system, the frequency analysis result of the reception signal of one channel is displayed on one screen shown in FIG. 4, so that a wide range of monitoring is performed in a plurality of channels by multi-beam reception, reception of a plurality of sensors, or the like. In such a sonar receiving system, as many screens as LOFAR display are required for that number of channels.

Therefore, as shown in FIG.
A so-called paging method or the like in which display screens are prepared by the number of beams or sensors and monitored at the same time, or the display screens are scrolled to be switched is adopted. However, in these display systems, as the number of reception processing channels increases, the LOFAR display screen also increases accordingly, and there are operational problems such as the number of display devices and the monitoring capability being limited.

[0006]

SUMMARY OF THE INVENTION Therefore, the present invention has been made to solve the above-mentioned drawbacks of the prior art, and an object of the present invention is to increase the number of display screens and the monitoring ability as the number of channels increases. Another object of the present invention is to provide a sonar receiver which prevents the deterioration.

[0007]

The sonar receiver according to the present invention is provided with a plurality of frequency analyzing means for respectively corresponding to a plurality of channels for frequency-analyzing the received signals of the corresponding channels at a constant sampling period, and the level of these analysis results. Peak value detection means for detecting and extracting the maximum value for each sampling cycle, and display means for displaying the detected maximum value as display information in display coordinates of frequency versus elapsed time (or output level). It is characterized by including.

Another sonar receiver according to the present invention comprises a plurality of frequency analyzing means for respectively corresponding to a plurality of channels for frequency-analyzing a received signal of the corresponding channel at a constant sampling period, and a level of these analysis results. Peak value detecting means for detecting and extracting the maximum value for each sampling cycle, and channel detecting means for detecting the channel in which the level maximum value for each sampling cycle is detected,
Display means for displaying the history of the detected channel in display coordinates of the azimuth versus elapsed time.

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention. Each of the reception signals of the plurality of channels 1 to N (N is an integer of 2 or more) is a reception output of a directional beam having sensitivity only in a certain specific direction, and is generally a plurality of reception signals in order to cover a wide range. A large number of directional beams are formed over the entire coverage area.

For example, as shown in FIG. 3 (A), when N = 7, the directional reception beams of each channel are arranged at every 10 °, and cover the entire 60 ° range. .. At this time, each reception beam is assumed to have a sensitivity of 10 ° width only.

The channels 1 to N received signals having directivity from each direction divided into these N channels are input to the corresponding FFT (Fast Fourier Transform) analyzers 11 to 1N, respectively. Frequency analyzed. The frequency analysis band W and the frequency resolution Δf of these analyzers 11 to 1N are all the same.

For example, the frequency analysis band W in each channel (direction) is set to 0 Hz to 10 Hz, and the frequency resolution (frequency resolution unit of how fine the W band is analyzed) Δf is set to 10 Hz. If frequency analysis is performed on the received signal, the frequency range W of the input signal is W = 0 to 1
At 0 KHz, it is possible to perform spectrum analysis of the ratio of its components for 1000 frequency elements.
The FFT analysis will be performed with the number of FFT points.

The spectrum analysis results of these analyzers 11 to 1N are input to the corresponding standards 21 to 2N, respectively, and the spectral components are flattened. This averages the background noise level for each channel and determines which channel LOFA
This is to enable uniform display even in the R display without being affected by the strength of the background noise level.

In the sonar receiving system, the received signal includes not only the target signal but also ambient noise (background noise), so the analysis result by the FFT analyzer is shown in FIG.
And (B). Since the background noise level and the target signal level are different between the respective channels, it is difficult to judge which channel the target signal is detected by simply comparing the output levels of the respective channels.

For example, in the channel analysis result of FIG. 2 (A), the target signal is masked by the background noise, and it cannot be discriminated. However, in the channel analysis result of FIG. 2 (B), the background noise is low. Therefore, the target signal can be discriminated. However, comparing only the output levels, the channel in FIG. 2 (A) is higher.

Therefore, regarding the analysis result of each channel,
By normalizing the background noise level (for example, normalizing with an average level) and then performing level comparison processing between the respective channels, it is possible to eliminate the influence of the background noise between the respective channels.

FIGS. 2C and 2D show the results of the analysis results of FIGS. 2A and 2B after being normalized. The standardizers 21 to 2N normalize the background noise of the analysis result corresponding to each channel in this manner.

Since the spectrum analysis results of each of these channels are performed at a constant sampling period, these analysis results are sent out at each sampling period and temporarily input while being respectively input to the memories 31 to 3N corresponding to each channel. Is stored.

In the conventional method, the analysis results for each channel are sequentially fetched from each of the storage units 31 to 3N (at each sampling cycle), and the LO of the corresponding channel shown in FIG.
As described above, it is visually displayed on the FAR display screen, and N LOFAR displays are required.

On the other hand, in the present invention, the maximum level of the spectrum analysis results of all the channels at the same sampling time is extracted by the peak selector 4, and this is extracted as 1
This is the display information of the individual LOFAR display screens 6.

Now, the background noise level of each frequency band in each channel is averaged by the normalization process,
All channels have the same number of FFT points (M = 10
00), the LOFA is displayed on the display coordinates where the horizontal axis is frequency and the vertical axis is time, as shown in FIG.
It is possible to display R.

It should be noted that, as shown in FIG. 4, the display coordinates of frequency vs. elapsed time are used as LOFAR display, and luminance is used as output level information. In addition, horizontal axis is frequency and vertical axis is output level. There are also examples, and in this case, the display resolution is determined by the physical specifications of each display.

For example, in the case of a CRT screen display, if the horizontal axis (frequency) is 1000 dots (pixels), the frequency analysis band W = 0 to 10 KHz is displayed with 1000 dots as in the previous example, so that 1 dot per dot Since it is displayed with a resolution of 10 Hz, and the frequency resolution is 10 Hz in the above example, the number of frequency elements is M = 1000 points, which matches the display resolution.

Therefore, as shown in FIG. 1, the spectrum analysis results of a plurality of channels are normalized to extract the maximum output level of each channel for each display resolution (= frequency resolution) and use it as the output level. If this is done, the spectrum levels of a plurality of channels are combined and displayed equivalently on one screen.

The peak selector 4 may detect the peak value for each spectrum, and in this case, the LOWAR display for displaying the peak values of all the detected spectra is displayed.

Further, a channel storage unit 5 for storing the channel when the peak selector 4 detects the maximum level value is provided. The channel memory 5 stores a channel corresponding to the spectrum analysis result data of which peaks have been detected (maximum level detection) from a plurality of channels, and based on this stored information, the history display screen 7 is displayed. The history of the arrival direction of the target signal is displayed.

For example, as shown in FIG. 3 (A), directional reception beams are arranged every 10 ° to cover a range of 60 ° as a whole, and each reception beam has a sensitivity of 10 ° width only. In the case of such a receiving system, the allocation of the seven channels is generally done in the arrival direction a of the target signal. Therefore, if the output of the channel memory 5 is taken out sequentially (at every sampling cycle) and displayed on the display coordinates of the azimuth (channel) versus the elapsed time as shown in FIG. 3B, the target at each sampling cycle is obtained. It is possible to determine the time course in which the detection position of the maximum level of the spectrum changes.
It can be seen that the history of the arrival direction of the target signal can be displayed.

In FIG. 1, the display unit 10 is shown as having two screens, a LOFAR display 6 and a history display 7, but these are shared by one screen and can be selectively displayed by an external command. It may be configured.

[0030]

As described above, according to the present invention, even if the number of receiving channels is increased to monitor a wide range, the spectrum analysis results of all channels are integrated and displayed. There is an effect that the screen monitoring is extremely easy because of the single requirement.

Further, not only one LOCAR display screen but also history display is performed, so that the arrival direction of the target signal can be easily determined.

[Brief description of drawings]

FIG. 1 is a system block diagram of an embodiment of the present invention.

2 (A) and 2 (B) show examples of frequency spectrum analysis results, and FIGS. 2 (C) and 2 (D) show examples when the analysis results of (A) and (B) are normalized. It is a figure.

FIG. 3A is a diagram showing a positional relationship between a history of target signal arrival directions and a reception channel, and FIG. 3B is a diagram showing an example of history display thereof.

FIG. 4 is a diagram showing an example of LOFAR display.

FIG. 5 is a diagram illustrating a conventional LOFAR display method.

[Explanation of symbols]

 4 Peak Selector 5 Channel Memory 6 LOFAR Display 7 History Display 11 to 1N FFT Analyzer 21 to 2N Normalizer 31 to 3N Memory

Claims (4)

[Claims] 1. A plurality of frequency analyzing means provided corresponding to a plurality of channels for frequency-analyzing a received signal of the corresponding channel at a constant sampling cycle, and a maximum level value among these analysis results for each sampling cycle. Sonar reception, characterized in that it includes peak value detection means for detecting and extracting the detected maximum value and display means for displaying the detected maximum value as display information at display coordinates of frequency versus elapsed time (or output level). apparatus. 2. A plurality of frequency analysis means provided corresponding to a plurality of channels and performing a frequency analysis on a reception signal of a corresponding channel at a constant sampling period, and a maximum level value among these analysis results for each sampling period. A peak value detecting means for detecting and extracting each, a channel detecting means for detecting a channel in which the maximum level of each sampling period is detected, and a history of the detected channel in display coordinates of azimuth versus elapsed time. A sonar receiving apparatus comprising: a display unit for displaying. 3. A plurality of frequency analyzing means provided corresponding to a plurality of channels for frequency-analyzing the received signals of the corresponding channels at a constant sampling period, and a maximum level value among these analysis results for each sampling period. Peak value detecting means for detecting and extracting each, and first display means for displaying the detected maximum level value as display information in display coordinates of frequency versus elapsed time (or output level),
Channel detection means for detecting a channel in which the maximum level value is detected for each sampling period, and second display means for displaying the history of the detected channel in display coordinates of azimuth versus elapsed time. Characterized sonar receiver. 4. The display by the first and second display means is configured to be selectively displayed on a common display screen in response to an external command.
The described sonar display device.