RU75060U1 - ACOUSTIC LOCATION SYSTEM OF NEAR ACTION - Google Patents

Abstract

A short-range acoustic location system containing an indicator, a control unit, n input adder, a high-frequency generator, a pulse modulator, a power amplifier, a switch and an acoustic antenna, n circuits consisting of a filter, an amplifier, a detector, an attenuator, and the filter inputs connected to the output of the switch, and the output of the attenuators connected to the inputs of the n-bit adder, the output of which is connected to the signal input of the indicator, controlling the input imp The pulse modulator, indicator and attenuators are connected to the outputs of the control unit, characterized in that (n-1) frequency multipliers, two analog keys, a frequency discriminator and a Doppler information processing unit are additionally introduced into it, the inputs of the first analog key connected to the output of the high-frequency generator and with the outputs (n-1) of the frequency multipliers, the inputs of which are connected to the output of the high-frequency generator, the inputs of the second analog key are connected to the outputs of the amplifiers, the outputs of the analog keys are connected to the inputs of the frequency discriminator, the output of which is connected to the input of the Doppler information processing unit, the control inputs of the analog keys, as well as the Doppler information processing unit are connected to the outputs of the control unit.

Description

The utility model relates to the field of acoustics, namely to acoustic location systems and can be used to obtain additional information about the characteristics of the movement of objects, which will allow to obtain a new volume of primary data on the underwater situation and expand the operational capabilities of the device.

The utility model can be applied to solve a variety of problems related to improving the safety of navigation on rivers and lakes, carrying out exploratory work on the shelf, with the aim of detecting and refining both the coordinates of ultrasound-reflecting objects and

characteristics of their movement. The preferred area of use is hydroacoustics, as well as fishing, atmospheric acoustics, and ultrasound diagnostics.

Known sonar for detecting underwater obstacles (echoral) and determining their coordinates in shallow water at distances of up to 50 meters, used for trawling in order to check the cleanliness of ship passages and identify underwater objects that are dangerous for navigation (see "Short-range sonars". .N. Yakovlev, G.P. Kablov. L .: Shipbuilding, 1983. p. 174-178), containing a high-frequency generator, pulse modulator, power amplifier, switch, acoustic antenna, amplifier, detector, indicator, control unit. The occurrence of underwater objects that are dangerous for shipping is associated with the natural process of changing the channel, and also due to the possibility of the current clutter of waterways by random objects, for example, sunken logs, etc. Solid trawling is distinguished (carried out within the established navigation time limits within the entire shipping lane) and local (It is carried out on the most dangerous sections - rapids, rifts, approaches to moorings, etc. with the aim of an operative search for drowned objects).

The work of echotral is as follows. The high-frequency generator generates a sinusoidal signal, which is fed to the signal input of a normally closed pulse modulator, to the control input of which are received from the control unit periodically repeated video pulses allowing the passage of the high-frequency signal. Harmonic-filled radio pulses with a frequency of 525 kHz, after amplification in the power amplifier, pass through the switch to an acoustic antenna that generates ultrasonic pulses propagating in the form of a narrow horizontal beam in the direction of possible detection of an underwater obstacle at the antenna installation depth (from 0.5 to 2 , 4 m). At

the location of the underwater object in the path of ultrasonic signals, it partially scatters them in the opposite direction to the acoustic antenna. Electrical signals corresponding to useful echo signals and masking noise are processed in the amplifier, detected and fed to the indicator input, where on the screen of a cathode ray tube with a long afterglow, the position of the mark on the scan of the electron beam determines the distance to the obstacle. In order to ensure viewing of the entire traversed strip, as well as in order to determine the course angle of the obstacle, the antenna rotates around a vertical axis in a given field of view.

During the testing and operation of this device, various designs of the acoustic antenna were used:

piezoelectric periscopic, horn and the so-called "cosecant", and, the latest design of the receiving-emitting antenna, according to the authors, ensured the formation of directivity (CH) radiation with a small level of the side field in the vertical plane down towards the bottom. The active element of the "cosecant" acoustic antenna consisted of four transducers having different spatial radiation characteristics, the acoustic fields of which as a result of a superposition of oscillatory processes in the location medium and created the desired shape of the directivity characteristic (XI) (figure 1). It should be noted that the formation of an HN antenna with a low level of the side field in the vertical plane down towards the bottom, unfortunately, led to an unacceptable increase in the level of radiation of the side field in the same plane up towards the water surface. So, when using a working radiation frequency of 525 kHz, the “cosecant” transducer formed an acoustic field with the following characteristics in the vertical plane — the width of the main lobe of the directivity characteristics at the level of 0.9 θ _0.9B ~ 4 °, the first side lobe in the direction (5 °) from the horizon with a level (- 1.4dB),

a second side lobe in the direction (7 °) from the horizon with a level (-3.7 dB), a third side lobe in the direction (10 °) from the horizon with a level (-9.7 dB); the fourth side lobe in the direction (30 °) from the horizon with a level (- 20 dB). The water surface is the interface for which the acoustic impedances of air and water (air - Z _air = 442 kg / m ² × s; water-Z _water = 1.5 × 10 ⁶ kg / m ² × s) are so different that all the energy of an acoustic wave falling from below to the surface returns to water, which caused the appearance of intense masking reverberation noise at all distances.

The design of the echotral piezoelectric interference antenna is as follows - two identical piezoelectric elements are glued onto a flat rectangular metal diaphragm (70 × 20) mm in size, the signal electrodes of which are sealed, and the one-sided radiation mode is ensured by the diaphragm being a cover for the air-filled housing of the antenna system. The estimated length of the near spotlight zone 1 ₉ (the “dead” zone) was about 1.4 m. When using the operating radiation frequency of 525 kHz and the indicated geometric dimensions, the antenna formed an acoustic field with the following characteristics:

- in the vertical plane - the width of the main lobe of the directivity characteristics at a level of 0.7 θ _0.7v , = 2 °, the first side lobe in directions (± 3.5 °) from the horizon with a level (-13.3 dB), the second side a lobe in directions (± 5.8 °) from the horizon with a level (-17.8 dB), a third side lobe in directions (± 8.2 °) from the horizon with a level (-21 dB);

- in the horizontal plane - the width of the main lobe of the directivity characteristics at the level of 0.7 θ _0.7Г = 7.2 °, the first side lobe in directions (± 12 °) from the vertical with a level (-13.3 dB), the second side lobe in directions (± 20 °) from the vertical with a level (-17.8 dB),

third lateral lobe in directions (± 30 °) from the vertical with a level (-21 dB).

With these parameters of the receiving-emitting antenna, the conclusions drawn by the authors themselves are logical: “In conditions of limited depth in the river channel (~ 4 m), the sound impulse could not pass a distance of more than 30 m without experiencing reflections from the surface of the water or the bottom; in some cases, these reflections caused intense interference on the indicator.

A small part of the sound impulses propagated with reflection from the water surface and from the bottom along the entire length, starting from the emitter itself.

To eliminate the reverberation noise on the indicator, the beginning of the sweep was artificially delayed, although the possibility of detecting underwater obstacles in the radius around the vibrator of about 3 m was excluded.

The image on the screen of the small obstacle indicator (echo from the buoy) caused the mark to triple due to the side lobes of the directivity of the vibrator. "

The disadvantages of the device also include the impossibility of determining the motion parameters of detected submerged objects relative to both the aquatic environment and relative to the carrier vessel of the echotral, as well as the lack of an echo signal processing channel for classifying objects according to the Doppler effect.

To increase the accuracy of detection of submerged objects and a more accurate examination of the water volume in the scheme of single-vibration (monostatic) echo direction finding used in this device, it is customary to reduce the duration of the probe pulse and narrow the main lobe of the directivity (CH) antenna. However, with a decrease in the angular dimensions of the acoustic beam on the accuracy of measuring the spatial coordinates of the target, rolling of the carrier ship begins to have a significant effect, which necessitates

expansion of the main lobe of CN. The arising contradiction can be resolved by using several space-stabilized different-sized main CN petals formed either by the same antenna or by a set of antennas.

The lateral radiation in the sonar antenna of the sonar station also has a significant impact on the accuracy and reliability of data on the underwater situation. In the presence of slopes of the bottom, a strongly dissected relief of the soil (the channel of the river channel, the navigable channel for entering the harbor, etc.), the amplitude of the echo received by the side lobes can exceed the amplitude of the echo received by the main lobe, which will lead to the recording of false information. Thus, to increase the accuracy of measurements, a decrease in the level of the side radiation field of the antenna is required.

The reasons that impede the achievement of the claimed technical result are the limited operational capabilities of the sonar to detect underwater obstacles (echo trawl) and determine their coordinates in shallow water, since the use of interference traditional receiving-emitting antennas in specific operating conditions - shallow water, “dumps” of depths, the presence extended interfaces, etc. it does not allow, in accordance with changing conditions of location, to regulate the severity of directional action and the value of the additional maximums of the XI of the receiving-emitting antenna, which reduces the accuracy of direction finding of targets, reduces the noise immunity of the device, increases the “dead” zone, and also does not provide for the possibility of distinguishing detected targets by such a classification criterion as the speed of movement. As a result, it is difficult to obtain reliable information about the underwater trawled water area due to the presence of masking reflections from the interface in combination with volumetric reverb, which leads to the registration of false data.

Signs that match the claimed object: high-frequency generator, pulse modulator, power amplifier switch, acoustic antenna, amplifier, detector, indicator, control unit.

Known sonar "Sargan-G" (see Kobyakov Yu.S., Kudryavtsev N.N., Timoshenko V.I. "Designing sonar fishing equipment." - L.: Shipbuilding, 1986, p.40-45), containing two high-frequency generators (LF and HF paths), a pulse modulator, a power amplifier, a switch, an acoustic antenna, two amplifiers, two detectors, an indicator, a control unit.

The work of sonar is as follows. If long-range target detection is required (maximum range of 1,500 m), the generator path generates radio pulses with a harmonic filling of 19.7 kHz, which are fed through the switch to a two-frequency acoustic antenna with two resonant frequencies of 19.7 kHz and 135 kHz, which produce acoustic pulse radiation at selected ultrasonic frequency. If it is necessary to clarify the picture of the near underwater environment (maximum range 500 m), the operator uses a path with a frequency of 135 kHz. When meeting with underwater objects, acoustic pulses are reflected at a particular frequency, echo signals are received by the antenna and fed to the amplifier of the corresponding receiving path. To detect the target, the sonar performs a survey of the water space: the acoustic antenna rotates around the vertical axis at predetermined angles, remaining in each fixed position for the time necessary for the acoustic wave to travel a double distance (to the target and back), corresponding to the range of the sonar. The location of the target is provided by the bearings (heading angle), distance (distance to the target) and the elevation angle of the target (angle of inclination of the axis of the directivity characteristics of the acoustic antenna in the vertical plane) determined by the location, and when switching the low and high frequencies of the sonar, the operator has

the ability to choose the optimal resolution in the direction (at LF 19.7 kHz, the width of the main lobe θ _0.7 = 14 °; at HF 135 kHz in the "Wide Day" mode - 4 °, in the "Narrow Day" mode - 2.5 ° ) The amplified and detected signals arrive at the cathode ray tube, on the screen of which echo signals are visually recorded, the distance to the target, the bearing, and the reflectivity of the target are determined. The presence of a path with a frequency of 135 kHz allows you to specify the bearing of the object and the distance to it.

The two-frequency acoustic antenna used in the sonar, which forms the directivity characteristic as a result of interference of coherent oscillations coming to each point of the medium from individual in-phase emitting sections of its surface, has a simple design, a high axial concentration coefficient, a minimum emitting surface with the smallest number of discrete active elements, but the level the lateral radiation of the antenna is large enough and amounts to approximately 20% of the magnitude of the main maximum, which can lead to STI to gross errors in determining the angular coordinates of the object, display and registration purposes as a point target system, etc., which limits the performance of sonar in shallow water and at an elevated excitement.

Detection of underwater targets in specific operating conditions of short-range acoustic location system - shallow water, “dumps” of depths, the presence of extended interfaces, etc. should be supplemented by the regime of distinguishing between stationary and moving objects, which is based on the use of the Doppler effect. Indeed, the presence of biological objects (moving schools of fish or individual individuals) in the treated zone will not pose a danger to the movement of ships, while the detection of objects of inanimate nature (macrobodies immobile relative to water) should be classified as potentially dangerous for navigation.

Signs that match the claimed object: high-frequency generator, pulse modulator, power amplifier, switch, acoustic antenna, amplifier, detector, indicator, control unit.

The reasons that impede the achievement of the claimed technical result are the limited operational capabilities of the sonar, since the use of an interference two-frequency acoustic antenna in specific operating conditions - shallow water, "dumps" of depths, the presence of extended interfaces, etc. - does not allow to eliminate lateral radiation in directions additional maximums and eliminate reflections from the interface, which reduces the noise immunity of the device, leads to the appearance of "false" targets, uv lichivaet "dead" zone, which may lead to inaccurate registration data. The sonar does not provide a mode for distinguishing between stationary and moving objects, which is based on the use of the Doppler effect.

Locational systems using nonlinear effects arising from the propagation of a finite-amplitude ultrasonic wave in an aqueous medium are free from a number of these shortcomings (see. "Hydroacoustic Encyclopedia", - Taganrog, TRTU Publishing House. 2000. S. 438 - 441). Nonlinear effects in an acoustic field can be considered as a result of a change in the properties of the medium during the propagation of a powerful sounding signal with a frequency f in it, which leads to a distortion of the wave shape of finite amplitude, i.e. generation of higher harmonic components with frequencies 2f, 3f, ... nf. The acoustic fields of the signals of higher harmonics have interesting spatial characteristics: - on the acoustic axis of the antenna, the change in the properties of the medium under the action of a powerful pump wave with frequency f occurs to the greatest extent, and therefore the main radiation maximum for each subsequent harmonic becomes narrower) in the directions of additional radiation maxima at the fundamental frequency, a change

properties of the medium occurs to a much lesser extent, which leads to a decrease in the efficiency of harmonic generation in these directions, i.e. the side field level for each subsequent harmonic is less than that of the previous one. The results of experimental studies of the spatial characteristics of acoustic fields for antennas of the existing RPA on the secondary acoustic signals — the higher harmonics 2f, 3f, .... of the emitted signal of the fundamental frequency f that are formed in the sonar channel (see V.Yu. Voloshchenko, Issues of studying acoustic signals are known higher harmonics for the modernization of fish-finding equipment (parts 1,2,3). University proceedings. North Caucasus region. Natural sciences. 2007. No. 2, p. 38-42; No. 3, p. 28-33, No. 4, p. 29-34). The results of experimental measurements of the sound pressure levels of acoustic signals of the fundamental frequency f and the higher harmonics nf formed in the aquatic environment when operating in standard low-frequency and high-frequency radiation modes for a two-frequency navigation and fish finder “Sargan-EM”, based on which using the equations sonar, the energy range of RPA on various signals was estimated, and the option of upgrading RPA “Sargan-EM” was proposed, which allows radiation paths without alterations to be made and with small changes in the receiving paths, transfer the product to a five-frequency navigation and fishfinding sonar and cover the frequency range of fishing sonar signals (20 kHz - 300 kHz) with the possibility of changing almost 10 times the width of the main radiation maximum and detecting a single fish / fish cluster at depths up to 500 m / 1700 m.

As a prototype, an acoustic echo-pulse locator was selected according to ed. SU No. 1228659 MKI G01S 7/52, publ. 12/20/1999, Bull.№35, containing indicator, control unit, n input adder, series-connected high-frequency signal generator, pulse modulator, power amplifier, switch, acoustic

antenna, n chains of series-connected filter, amplifier, detector and attenuator, connected in parallel so that the filter inputs are connected and connected to the switch, and the attenuator outputs, the control inputs of which are connected to the control unit, are connected to the n inputs of the adder, the output of which is connected to the signal input of the indicator.

The work of the acoustic echo-pulse locator is as follows. A high-frequency generator generates a sinusoidal signal of frequency f, which is fed to the signal input of a normally closed pulse modulator, to the control input of which are received from the control unit periodically repeated video pulses allowing the passage of the high-frequency signal. Radio pulses with a frequency f, after amplification in a power amplifier, pass through a switch to an acoustic antenna that emits ultrasonic vibrations propagating in an aqueous medium with non-linear elastic characteristics. When propagating in a medium, an acoustic signal of finite amplitude experiences cumulative distortion of the wave profile, which physically means the generation of higher harmonic components 2f, 3f, ... nf of the emitted signal with a frequency f. The polyharmonic location signal reaches the object, is reflected from it and, propagating back, reaches the acoustic antenna, which converts the reflected acoustic vibrations into their corresponding electric ones, arriving at the inputs of n circuits with frequencies f, 2f, 3f, .... nf, consisting of series-connected filter, amplifier, detector and attenuator. At the outputs of these chains, after filtering, amplification, detection, and reduction of the amplitudes of the electrical signals in the attenuators, the electrical signals of various amplitudes are extracted, which are fed to the n input adder, from the output of which the resulting voltage is supplied to the signal input of the indicator. So the resulting

the directivity characteristic in the receiving mode of the receiving-emitting antenna of the acoustic echo-pulse locator will be determined by the sum of the directivity characteristics in the receiving mode of this antenna for acoustic signals with frequencies f, 2f, 3f, .... nf. This will allow, by changing the transfer coefficients of the attenuators using the control unit, to regulate the severity of the directional action and the value of the additional maxima of the antenna’s antenna, which will increase the accuracy of direction finding of targets, increase the noise immunity of the device, and reduce the “dead” zone.

Signs that coincide with the claimed object: indicator, control unit, n input adder, high-frequency generator, pulse modulator, power amplifier, switch, acoustic antenna, n chains of series-connected filter, amplifier, detector and attenuator.

The reasons that impede the achievement of the claimed technical result are the limited operational capabilities of the acoustic echo-pulse locator due to the fact that with its help the operator can only detect the target, evaluate its reflectivity at several operating frequencies and measure with the required accuracy the parameters that carry information about its coordinates (range, azimuth and course angles), while measuring the characteristics of the target’s movement (direction and speed of movement) is not performed.

The objective of this utility model is to expand the operational capabilities of an acoustic echo-pulse locator by determining the motion characteristics of detected objects.

The technical result of the utility model is the possibility of obtaining additional information about the characteristics of the movement of objects, which will allow to obtain a new amount of primary data on the underwater situation and expand the operational capabilities of the device.

The technical result is achieved by the fact that in an acoustic echo-pulse locator containing a high-frequency generator connected through a series-connected pulse modulator, a power amplifier and a switch with an acoustic antenna, n chains of series-connected filter, amplifier, detector and attenuator, the outputs of which are connected to the inputs n input adder, the output of which is connected to the indicator; the control inputs of the pulse modulator, indicator, and attenuators are connected to the outputs of the control unit, the filter inputs are connected to the output of the switch, (n-1) frequency multipliers are additionally introduced, their inputs are connected to the output of the high-frequency generator, two n are input analog keys, the control inputs of which are connected with additional outputs of the control unit; the output of the analog keys are connected to the inputs of the frequency discriminator, the output of which is connected to the input of the Doppler information processing unit; the inputs of the first analog key are connected to the outputs of the high-frequency generator and frequency multipliers, the inputs of the second analog key are connected to the outputs of the amplifiers.

The entered blocks in combination with the described connections form an additional path for measuring the characteristics of the target’s movement.

The utility model is illustrated by drawings:

- figure 1 shows the directivity in the vertical plane of the "cosecant" sonar acoustic antenna to detect underwater obstacles (echo trail) and determine their coordinates in shallow water;

- figure 2 shows the directivity characteristic of the antenna of the complex "Sargan-K" ("Wide Beam") for the signal of the fundamental frequency f = 135 kHz and the emerging harmonics 2f = 270 kHz, 3f = 405 kHz, 4f = 540 kHz, 5f = 675 kHz

- figure 3 shows the directivity of the antenna complex "Sargan-K" ("Narrow DN") for the signal of the fundamental frequency f = 135

kHz and emerging harmonics 2f = 270 kHz, 3f = 405 kHz, 4f = 540 kHz, 5f = 675 kHz, 6f = 810 kHz;

- figure 4 - shows a structural diagram of the inventive device.

The short-range acoustic location system contains a high-frequency generator 1, which is connected through a series-connected pulse modulator 2, a power amplifier 3 and a switch 4 with an acoustic antenna 5, as well as with one of the inputs of the first analog key with inputs (n-1) of frequency multipliers 7, the outputs of which are connected to the remaining inputs of the first analog switch 6, the output of which is connected to the input of the frequency discriminator 8. The output of the switch 4 is connected to the inputs of n chains, each consisting of sequentially filter 9, amplifier 10, detector 11 and attenuator 12, moreover, the filters are tuned to frequencies f, 2f, 3f, .... nf. The outputs of the attenuators 12 are connected to the inputs n of the input adder 13, and its output is connected to the signal input of the indicator 14. The outputs of the amplifiers 10 are also connected to the inputs of the analog switch 15, the output of which is connected to the second input of the frequency discriminator 8, the output of which is connected to the Doppler information processing unit 16. The control inputs of the pulse modulator 2, analog switches 6 and 15, attenuators 12, indicator 14 and the Doppler information processing unit 16 are connected to the outputs of the control unit 17.

The work of the locator is as follows.

The high-frequency generator 1 generates a sinusoidal signal with a frequency f supplied to the signal input of a normally closed pulse modulator 2, to the control input of which periodically repeating video pulses are received from the control unit 17, allowing the passage of the high-frequency signal. Radio pulses with a frequency f, after amplification in a power amplifier 3, pass through a switch 4 to an acoustic antenna 5, which emits ultrasonic vibrations propagating in an aqueous medium having

nonlinearity of elastic characteristics. When propagating in a medium, an acoustic signal of finite amplitude experiences accumulated distortion of the wave profile, which physically means the generation of higher harmonic components 2f, 3f, ... nf of the emitted signal with a frequency f. When propagating in a medium, a polyharmonic location acoustic signal with frequencies f, 2f, 3f, ... nf reaches an object moving at a radial speed υ _p , is reflected from it, undergoes a corresponding Doppler frequency shift for each harmonic component (± f _{D (f)} ) , (± f _{D (2f)} ), ... (± f _{D (nf)} ), where (+) and (-) correspond to the approximation or removal of the object, and, propagating back, reaches antenna 5, which converts the reflected acoustic vibrations into corresponding electrical inputs to n circuits (for signals with frequencies (f ± _{fD (f)} ) ,, (2f ± _{fD (2f)} ), ... (nf ± f _{D (nf)} ) consisting of series-connected filters 9 {frequency (f ± f _{D (f)} )}, {frequency (2f ± f _{D (2f)} )} ... {frequency (nf ± f _{D (nf)} )}; amplifiers 10, detectors 11 and attenuators 12, the control inputs of which are connected to the control unit 17. After driving in the attenuators 12 amplitudes of electrical signals to the required values, they are fed to the n input adder 13, from the output of which the resulting voltage is supplied to the signal input of the indicator 14. Thus, the resulting directivity of the acoustic antenna 5 lock ion system is determined by the sum of the directivity characteristic in the reception mode of the antenna 5 to acoustic signals with frequencies f, 2f, 3f, ... nf. This will allow, by changing the transmission coefficients of the attenuators 12 in accordance with changing conditions of location, to regulate the severity of the directed action and the value of the additional maximums of the antenna’s antenna, which will increase the accuracy of direction finding of targets, increase the noise immunity of the device, and reduce the “dead” zone.

To measure the target’s motion characteristics, one of the electrical signals with the frequency (f ± f _{D (f)} ), (2f ± f _{D (2f)} ), ... (nf ± f _{D (nf)} ) from the outputs of the amplifiers

10 through an analog switch 15 is fed to the input of the frequency discriminator 16, to the second input of which from the output of the first analog switch 6 one of the signals with frequencies f, 2f, 3f, ... nf is supplied, respectively, without Doppler shift. For this, the analog key input 6 is connected to the output of the high-frequency generator 1 with a frequency f, as well as to the outputs (n - 1) of the frequency multipliers 7 with multiplication factors of 2, 3, ... n times. A signal is selected by supplying control signals from the control unit 17 to the control inputs of analog keys 6 and 15. At the output of the frequency discriminator 16, an electric signal with a frequency corresponding to the Doppler shift (f _{D (f)} ), (f _{D (2f)} ), ... or (f _{D (nf)} ), which makes it possible to calculate n values of the radial component of the target velocity in the Doppler information processing unit 16 based on the Doppler effect according to the relation

where: K _{V (nf)} = 2 × (nf) / s is the speed sensitivity of the Doppler meter for an acoustic signal at a frequency nf, which represents the increment of the Doppler frequency when the speed changes by 1 node; υ _{P (nf)} is the radial component of the speed of relative approach (+) or removal (-) of the object and the carrier vessel of the acoustic location system, measured on the corresponding acoustic signal; nf is the frequency used to measure the motion parameters of the target, the acoustic signal; n = 1, 2, 3, ... is the number of the harmonic used; C is the speed of sound in the aquatic environment.

The main tasks of the secondary processing unit 16 are as follows:

1) measurement of Doppler frequencies;

2) the transition from the frequency values to the speed values of the object;

3) the introduction of amendments to the measured values of the radial velocity of the object;

4) the conversion of information into a code of indicator elements and an indication of the radial velocity of the object. To perform these operations on the secondary processing of signals in a short-range acoustic location system, similar devices from radio-Doppler systems can be successfully used (see Digital Navigation Devices. Edited by VB Smolov. M., Sov. Radio, 1980).

The limited surface water volume, the mixing effect of wind waves and currents, the multidirectional effect of the Archimedes force and the gravitational field, etc. cause accumulation of objects hazardous to shipping in the surveyed layer, as a result of which short-range acoustic location systems must have sufficient resolution, i.e. the ability of the system to separate analysis of echo signals having close parameters. In our case, the analysis of sonar signals includes their detection and measurement of parameters that carry information about the coordinates (range and corresponding angles) and radial velocity of the detected objects that reflect the probing signals. For separate measurement of the coordinates of objects, informative echo signals should be enabled, respectively, in time, direction of arrival, and Doppler frequency offset. Thus, short-range acoustic location systems should be characterized by a resolution in time (range), direction of arrival of signals (angular coordinates) and frequency (radial velocity of objects), moreover, the resolution is not of practical interest in terms of any echo signal parameter, but according to its coordinate: range, angle, speed. In accordance with the foregoing, we write the wording (see the Handbook on the theoretical foundations of radio electronics. Edited by B.X. Krivitsky. In 2 volumes. T.2. - M .: Energy, 1977. p.166-180):

Range resolution is quantified by the minimum distance δ (z) between two point objects,

located in the same direction and having the same radial speed, at which it is possible to separately detect these targets and measure their ranges.

The resolution in angular coordinates is estimated by the minimum angle δ (φ) between the directions to objects having the same range and radial speeds, at which it is possible to separately detect and measure the angular coordinates.

The speed resolution is estimated by the minimum difference in radial velocities δ (υ _p ) of two objects that are not resolvable in range and angular coordinates, allowing separate detection and measurement of their radial velocities.

The energy signal-to-noise ratio, the shape of the signals, under other ideal conditions, determine the limiting value of the resolution, which is called the potential resolution - δ (φ) _sweat , δ (z) _sweat , δ (υ _р ) _sweat , and, in real conditions of reception and signal indications, there is always an additional extension of them with respect to the resolution parameter, which leads to a deterioration in resolution, as a result of which the real resolution is always worse than potential.

Known design relationships for potential resolution in the case of a pulsed input signal with a rectangular envelope:

in range -

radial speed -

in angular coordinate -

where c is the speed of sound in water, τ _and is the duration of a rectangular pulse, ω ₀ is the cyclic frequency of the harmonic signal, θ _0.7 is the width of the radiation pattern at half power level.

Let us consider as an example illustrating the achievement of the desired result when using a short-range acoustic location system with antennas identical to those used in the Sargan K navigation and fish-searching complex, which feature is the ability to change the width of radiation patterns by connecting more or less number of active elements (see Voloshchenko V.Yu. Issues of research of acoustic signals of higher harmonics for the modernization of fish-finding equipment, (parts 1, 2, 3). universities Ia. North Caucasus region. nature. Science. 2007. №2, s.38-42).

So, in the radiation mode, the antenna of the Sargan-K complex has:

in the “Wide Day” mode (Fig. 2):

1) at a frequency f = 135 kHz, the width of the radiation pattern at the level of 0.7 θ _{0.7 (f)} = 4.7 ° and the level of the side radiation P _{PSU (f)} = (- 15.5 dB);

2) at a frequency of 2f = 270 kHz, the radiation pattern width at the level of 0.7 θ _{0.7 (2f)} = 3.2 ° and the side radiation level P _{PSU (2f)} = (- 20 dB);

3) at a frequency of 3f = 405 kHz, the width of the radiation pattern at the level of 0.7 θ _{0.7 (3f)} = 2.8 ° and the level of side radiation P _{PSU (3f)} = (- 50 dB);

4) at a frequency of 4f = 540 kHz, the radiation pattern width at the level of 0.7 θ _{0.7 (4f)} = 2.4 ° and the side radiation level Р _{PSU (4f)} = (- 50 dB);

5) at a frequency of 5f = 675 kHz, the radiation pattern width at the level of 0.7 θ _{0.7 (5f)} = 2 ° and the side radiation level Р _{PSU (5f)} (-50 dB);

in the “Narrow NAM” mode (Fig. 3):

1) at a frequency f = 135 kHz, the width of the radiation pattern at the level of 0.7 θ _{0.7 (f)} = 2.1 ⁰ and the level of side radiation P _{PSU (f)} = (- 9 dB);

2) at a frequency of 2f = 270 kHz, the width of the radiation pattern at the level of 0.7 θ _{0.7 (2f)} = 1.7 ° and the level of side radiation P _{PSU (2f)} = (- 16 dB);

3) at a frequency of 3f = 405 kHz, the width of the radiation pattern at the level of 0.7 θ _{0.7 (3f)} = 1.3 ° and the level of side radiation R _{PSU (3f)} = (- 33dB);

4) at a frequency of 4f = 540 kHz, the width of the radiation pattern at the level of 0.7 θ _{0.7 (4f)} = 1 ° and the level of side radiation P _{PSU (4f)} = (- 25 dB);

5) at a frequency of 5f = 675 kHz, the radiation pattern width at the level of 0.7 θ _{0.7 (5f)} = 1 ° and the level of side radiation P _{PSU (5f)} = (- 31 dB);

6) at a frequency of 6f = 810 kHz, the radiation pattern width at the level of 0.7 θ _{0.7 (6f)} = 0.8 ° and the side radiation level R _{PSU (6f)} = (- 28 dB).

An analysis of the above experimental data and relations (2) - (4) allows us to draw the following conclusions. It follows from (2) that an increase in range resolution is achieved by decreasing the pulse duration, and, for the short-range acoustic location system under consideration, it is the same for all used signals. It follows from (3) that for unmodulated signals, the potential resolution in speed at a known time of arrival of the echo signal is inversely proportional to the signal duration and the cyclic frequency of the location signal and can be improved with their increase, i.e. for the considered short-range acoustic location system with the same probe signal duration for each subsequent harmonic, it is higher. It follows from (4) that the potential resolution in the angular coordinate for each subsequent harmonic is also higher.

The solution of various problems associated with improving the safety of navigation on rivers and lakes, carrying out exploratory work on the shelf, etc., carried out using short-range acoustic location systems, is associated with a detailed examination of the surface layer of various water areas in which the detected targets must be classified by speed:

- 1) dangerous objects (objects of inanimate nature) moving with the speed of the river or motionless relative to stagnant water, as a result of which they may be on the chosen course of the vessel;

2) potentially safe objects (wildlife) moving in different directions at their own speed and able to deviate from the course of a surface ship.

The use of the proposed short-range acoustic location system is also promising for navigating ships - when irradiating stationary objects (for example, the bottom of a reservoir, mooring wall, etc.), you can determine the speed of the vessel carrier device.

Thus, the proposed short-range acoustic location system can be used to solve a variety of tasks related to improving the safety of navigation on rivers and lakes, carrying out exploratory work on the shelf, aimed at detecting and refining both the coordinates of ultrasound-reflecting objects and their motion characteristics on multiple working signals of multiple frequencies with the necessary resolution.

The practical implementation of the inventive device is not difficult. A frequency discriminator, for example, may consist of a series-connected multiplier, a low-pass filter, and a frequency-voltage converter. If an oscilloscope indicator is used as a block for processing Doppler information, then on its screen we will obtain a sequence of video pulses with an amplitude proportional to the speed of movement of the detected objects.

Claims (1)

A short-range acoustic location system containing an indicator, a control unit, n input adder, a high-frequency generator, a pulse modulator, a power amplifier, a switch and an acoustic antenna, n circuits consisting of a filter, an amplifier, a detector, an attenuator, and the filter inputs connected to the output of the switch, and the output of the attenuators connected to the inputs of the n-bit adder, the output of which is connected to the signal input of the indicator, controlling the input imp The pulse modulator, indicator and attenuators are connected to the outputs of the control unit, characterized in that (n-1) frequency multipliers, two analog keys, a frequency discriminator and a Doppler information processing unit are additionally introduced into it, the inputs of the first analog key connected to the output of the high-frequency generator and with the outputs (n-1) of the frequency multipliers, the inputs of which are connected to the output of the high-frequency generator, the inputs of the second analog key are connected to the outputs of the amplifiers, the outputs of the analog keys are connected to the inputs of the frequency discriminator, the output of which is connected to the input of the Doppler information processing unit, the control inputs of the analog keys, as well as the Doppler information processing unit are connected to the outputs of the control unit.