RU2719214C1 - Active sonar - Google Patents

Abstract

FIELD: hydro acoustics.SUBSTANCE: invention relates to hydroacoustic equipment, more specifically to active sonar, including to active sonars intended for detecting objects, measuring coordinates and motion parameters of detected objects. Invention objective is to provide the possibility of determining the radial velocity of the detected object on a single frequency-modulated signal.EFFECT: technical result of the invention consists in the procedure for determining the radial velocity of the detected object with reduction of the dead zone near the sonar and optimization of the load on the sonar equipment by emitting a single frequency-modulated signal.1 cl, 3 dwg

Description

The invention relates to sonar technology, and more particularly to the field of active sonar, including active sonar, designed to detect objects, measure coordinates and motion parameters of detected objects.

An important parameter of the motion of detected objects is their radial velocity. The probe signal should provide the ability to measure this parameter. A tonal signal provides a measurement of the radial velocity of a detected object, but in order to classify the detected object according to its flare structure, a high distance resolution must be provided, for which short-duration tonal probing signals should be used. A short-duration tonal sounding signals have a low radial speed resolution of the detected object and do not allow for long detection ranges.

Known active sonar with object classification (RF patent No. 35474), containing a series-connected device for generating a pseudo-random (PS) probe signal, a generator device and a radiating antenna, also containing a series-connected receiving acoustic antenna, a device for separating the processing of tonal and PS signals in frequency, multi-channel a device for Doppler matched filtering of the PS echo signal, a device for estimating the radial velocity of an object according to the PS echo signal and a device for determining the radial velocity of the object, also containing a device for generating a sounding probe signal and a series-connected multichannel device for Doppler filtering of a tone echo signal and a device for estimating the radial speed of an object from a tone signal, the output of the device for generating a sounding probe signal connected to the second input of the generator device, the second output of the processing separation device tonal and PS signals in frequency connected to the input of a multi-channel device for plerovskoy tone filtering the echo and the radial velocity estimator output facility tonal signal is coupled to the second input device determining the radial velocity of the object.

The disadvantage of this sonar is that in order to determine the radial speed of a detected object from a pseudorandom complex probing signal, it is necessary to perform multi-channel matched filtering, the tone signal at low radial speeds of the detected object has a signal / reverb ratio less than a complex signal to the root of the band times. A packet of signals is also emitted in this sonar, which leads to an increase in the dead zone near the sonar in comparison with the radiation of a single signal, since reception in the sonar is usually carried out after the end of the radiation of the entire probe signal according to a clock pulse. In addition, with a long duration of the tonal probe signal, the sonar has a high resolution in radial speed, but has a very low resolution in distance.

By the number of common features, the closest analogue of the invention is the active sonar described in Fangyong Wang, Shuanping Du, Wei Sun, Qiang Huang, and Jiao Su. A method of velocity estimation using composite hyperbolic frequency-modulated signals in active sonar // J. Acoust. Soc. Am. 31 (5) / 136.C. 316-312. This active sonar contains (Fig. 1) a series-connected device 1 for generating a frequency-modulated sounding signal with a decreasing law of frequency change from time to time, a generating device 2 and a radiating acoustic antenna 3, also contains a series-connected receiving acoustic antenna 4, a first matched filter 5 and device 6 for measuring the arrival time of the response of the first matched filter, while the second output of the device 1 is connected to the second input of the device 5. The active gy The scroller also includes a series-connected device 7 for generating a frequency-modulated probe signal with an increasing law of frequency change from time to time, a second matched filter 8, a device 9 for measuring the response time of the second matched filter, a device 10 for measuring the delay time between the responses of the first and second matched filters, and a device 11 determining the radial velocity of the detected object from the delay time between responses from the first and second matched filter, p By the way, the second output of device 7 is connected to the second input of device 2, the third output of device 7 is connected to the second input of device 11, the third output of device 1 is connected to the third input of device 11, the second output of antenna 4 is connected to the second input of device 8, and the output of device 6 connected to the second input of the device 10.

The radial velocity of the detected object is determined by estimating the mutual offset of the responses of the matched filters of each burst signal from two frequency-modulated (FM) signals.

The disadvantage of this prototype sonar is the radiation of a packet of probing signals, which leads to an increase in the need for parallel operation of two matched filters and to ensure their synchronization, as well as the need to provide a wider working frequency band of a sonar when a packet of FM signals separated in frequency is emitted, or, at emission of FM burst signals at a single carrier frequency, an increased level of reverberation noise in the frequency band of the emitted signals.

The objective of the invention is the ability to determine the radial velocity of the detected object from a single frequency-modulated signal.

The technical result of the invention consists in the implementation of the procedure for determining the radial velocity of the detected object while reducing the dead zone near the sonar and optimizing the load on the sonar equipment by emitting a single frequency-modulated signal.

To achieve this technical result, an active sonar containing a series-connected device for generating a frequency-modulated probing signal, a generator device and a radiating acoustic antenna, also containing a series-connected receiving acoustic antenna, a matched filter and a device for measuring the response time of a matched filter, the second output a device for generating a frequency-modulated sounding signal is connected to the second input with filter, new features are introduced, namely, a series-connected envelope extraction device, a device for measuring the temporal position of the echo envelope front, a device for measuring the offset of the response of the matched filter relative to the envelope of the echo signal and a device for determining the radial velocity from the offset of the response of the matched filter relative to the front of the echo signal are introduced the first input of which is connected to the output of the device for determining the response bias of the matched filter relative to the echo envelope front, and the second input is connected to the third output of the frequency-modulated probe signal generating device, while the output of the matched filter response arrival time measuring device is connected to the second input of the matched filter response bias detection device relative to the echo envelope front, and the second output is acoustic the antenna is connected to the input of the envelope extraction device.

The specified technical result is achieved due to the fact that when receiving a single frequency-modulated echo signal, the response maximum offset of the matched (with the reference signal) filter is measured relative to the front of the amplitude envelope of the echo signal at the input of the matched filter, by which the radial velocity of the detected object is determined. Using this estimate makes it possible to use single frequency-modulated sounding signals in the sonar, which will reduce the load on the processing system of the received echo signals due to the fact that for a single frequency-modulated signals one matched filter is sufficient, and also will lead to a reduction in the dead zone near the sonar due to reducing the overall duration of the emission of signals. Also, the use of single frequency-modulated sounding signals reduces the requirements for the radiating path. This technical result is obtained when the newly introduced devices work together, the connections between them and the connections of these devices with other sonar devices.

The invention is illustrated in FIG. 1, FIG. 2 and FIG. 3. In FIG. 1 shows a device diagram of a prototype active sonar, in FIG. 2 is a device diagram of the proposed active sonar. In FIG. Figure 3 shows the response of the matched filter to the echo from an object with a nonzero radial velocity (dashed line) and the envelope of the echo at the input of the matched filter (solid line).

The active sonar (Fig. 2) contains a series-connected device 1 for generating a frequency-modulated probing signal, a generator 2 and a radiating acoustic antenna 3. The active sonar also contains a series-connected receiving acoustic antenna 4, a matched filter 5, and a device 6 for measuring the response arrival time of a matched filter device 12 for measuring the offset of the response of the matched filter relative to the front of the echo envelope and device 13 for measuring the radial the bias of the response of the matched filter relative to the front of the echo envelope, as well as the device 14 for extracting the envelope and the device 15 for measuring the temporal position of the envelope of the echo signal, while the second output of the antenna 4 is connected to the input of the device 14, the second output of the device 1 is connected to the second input of the matched filter 5, the third output of the device 1 is connected to the second input of the device 13, and the output of the device 15 is connected to the second input of the device 12.

The practical implementation of the devices included in the invention is known from the practice of hydroacoustics and is implemented through the use of digital devices.

Device 6, 12, 13, 14, and 15 can be implemented using microprogram discrete devices, see, for example, the book Designing Pulse and Digital Devices of Radio Engineering Systems. / Grishin Yu.P., Kazarinov Yu.M., Katikov V.M. and etc.; Ed. Yu.M. Kazarinova. - M .: Higher. school., 1185. S. 4, 27, 31, 3 and Digital radio navigation devices / V.V. Barashenkov, A.E. Lutchenko, E.M. Skorokhodov et al .; under the editorship of B. B. Smolova. M .: Sov. Radio, 1180.S. 116-130.

The operation of the device is as follows.

The device 1 generates a frequency-modulated sounding signal, which is radiated into the water by the emitting acoustic antenna 3 using the generating device 2. The echo signals reflected from the object from the output of the receiving acoustic antenna 4 are sent to the device 5 and 14. The reference signal 5 is received at the other input of the device 5 from the device 1 signal needed for consistent filtering of frequency-modulated echo signals. The output device 5, after the matched filtering the frequency-modulated echo signal processes input to the device 6. The device 6 is performed measurement of time (t _off) the arrival of the echo response of the matched filter. Moreover, this measurement is made relative to the time corresponding to the end of the radiation of the probe signal. The output device 6 t _off is input to the device 12. The device 14 is performed while the selection of the envelope of the received echo signal, which enters the device 15 where the measurement of time position of the echo signal envelope front (i.e. _{the front)} with respect to time (at a sufficient signal / noise ratio ) corresponding to the end of the radiation of the probe signal. From the output of the device 15 tons of the _front goes to another input of the device 12, where the measurement of the response offset of the matched filter relative to the front of the echo envelope is performed:

_Fr.sm Δt = τ _off -τ _front,

Received in the device 12, the value Δt _{fr.sm is} supplied to the input of the device 13. In the device 13, the radial velocity of the detected object is determined by the offset of the response of the matched filter relative to the envelope front, taking into account the parameters (f ₀ , F and T) of the probe signal generated in the device 1:

where f ₀ is the carrier frequency of the frequency-modulated sounding signal; C is the speed of sound in water; T is the duration of the frequency-modulated sounding signal; F is the bandwidth of the frequency-modulated probe signal.

The use of devices 12, 13, 14 and 15, as well as the connection of these new devices with each other and with known active sonar devices, determine the radial speed of a detected object from a single frequency-modulated signal.

To illustrate the operation of the claimed active sonar below is an example of determining the radial speed of a detected object.

In FIG. 3, the solid line represents the envelope of the frequency-modulated echo signal at the input of the matched filter and the dashed line represents the response of the matched filter to the echo signal. Also in FIG. 3 by vertical dashed lines indicate the times t and t _{none front,} and shows the displacement response time matched filter relative to the front of the envelope of the echo signal (Δt _fr.sm). In this case, the echo was modeled with a radial velocity of 7.4 m / s, using the devices 6 and 15 defined by the value of m = 4.86 with _{the front} and _none t = 4.94 s, using the device 12 obtained by: Δt _fr.sm = t _off - t = 0.08 with _{the front.} The radial velocity of the detected object is determined in the device 13:

which indicates a good agreement of the results.

при использовании пачки из двух зондирующих сигналов мертвая зона была бы 480 м.The use of a single sounding signal instead of a packet of two sounding signals leads to a 2-fold reduction in the dead zone near the sonar. In this case, the dead zone will be:

when using a pack of two sounding signals, the dead zone would be 480 m.

Thus, the task to ensure the possibility of determining the radial velocity of the detected object from a single frequency-modulated signal is successfully solved.

Claims (1)

An active sonar comprising a series-connected device for generating a frequency-modulated sounding signal, a generator device and a radiating acoustic antenna, also containing a series-connected receiving acoustic antenna, a matched filter and a device for measuring the arrival time of the response of a matched filter, while the second output of the device for generating a frequency-modulated probing the signal is connected to the second input of the matched filter, characterized in that it an envelope extraction device, a device for measuring the temporal position of the echo envelope front, a device for measuring the response offset of the matched filter relative to the front of the echo signal and a device for determining the radial velocity by the offset of the response of the matched filter relative to the front of the echo envelope, the first input of which is connected to the output of the response bias detection device, are introduced matched filter relative to the front of the echo envelope, and the second input connected to the third output of the device forming a frequency-modulated probing signal, the measurement device output time of arrival of the matched filter response is coupled to the second input device displacement detecting the matched filter response relative to the front of the envelope of the echo signal and the second output of the receiving acoustic antenna connected to the input device isolation envelope.

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