RU2810695C1 - Direction finder of hydroacoustic signals, forming static fan of spatial channels - Google Patents

Abstract

FIELD: hydroacoustics.

SUBSTANCE: hydroacoustic means of detecting signals used for small-sized carriers such as underwater vehicles, bottom hydrophysical stations, sonobuoys. The direction finder consists of a cylindrical sound-transparent antenna and a radio part. On the guide of the cylindrical antenna there are 2N hydroacoustic receivers, which are placed evenly at intervalsΔθ =360/2N. Signals from hydroacoustic receivers are transmitted to the spatial channel generation unit, in which a fan of 2N spatial channels with directional patterns (DP) of the “reverse” cardioid type is formed. The spatial channel with the maximum value of the received signal (RS_m) is selected and the direction to the θ_m signal source is determined, corresponding to the RS_m axis of the DP. By signal voltage difference Δ U=U_r -U_l, received by the RS_m channels adjacent to RS_m and RS_r and PC_l, as well as according to a pre-introduced correction dependenceξ_θ (Δ U) the true value is determined by the signal sourceθ_tr =θ_m+ξ_θ.

EFFECT: increasing the accuracy of the amplitude direction finding method used in the signal detection mode using a static RS fan, while maintaining the dimensions of the antenna, the number of receivers and without shielding the receivers.

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Description

The invention relates to hydroacoustic means for detecting signals and can be used for small-sized carriers such as underwater vehicles, bottom hydrophysical stations, radio sonobuoys.

Systems for detecting noisy objects and determining the direction to these objects are called direction finders. The general principles of constructing hydroacoustic signal direction finders are set out in the book [Handbook of hydroacoustics / ed. A.E. Kolesnikova. L.: Shipbuilding, 1988. P. 18-30]. For simultaneous viewing of sectors of space (up to 360°), a static fan of spatial channels (SC) is formed. The direction to the signal source is determined by the direction of the axis of the radiation pattern (DP) of the PC, in which the maximum value of the received signal is recorded, and the error in determining the direction is approximately half the angular width of the pattern at a level of - 3 dB [Reference...].

The direction finder antenna for detecting a signal in a 360° sector, as a rule, is a cylinder along the generatrix of which hydroacoustic receivers are located. For a cylinder in a free environment, the maximum number of spatial channels formed by the pattern is equal to the number of receivers located around the circumference of the antenna.

In the author's certificate for a device for omnidirectional reception of communication signals and identification of a hydroacoustic station [a.s. USSR No. 1840778, IPC G01S 7/52, publ. 07/27/2009] presents a scheme for the formation of a static DP fan, and in the patent for a hydroacoustic station for detecting small-sized objects [RF patent No. 2680673, IPC G01S 15/04, publ. 12/04/2017] a static pattern fan is formed using a cylindrical antenna. In the patent for a method for detecting objects making noise in the sea [RF patent No. 2694782, IPC G01S 3/80, publ. 07/16/2019] the features of time-frequency signal processing in each channel of the direction finder are considered.

A common disadvantage of the presented technical solutions is the significant size of the aperture of the cylindrical receiving antenna. Let us denote the width of the pattern at the -3 dB level as Δθ ₀₇ . If it is necessary to obtain the value Δθ ₀₇ =5° at a frequency of 3 kHz, the diameter of the cylinder should be 5.89 m. When the frequency decreases or if it is necessary to reduce the value of Δθ ₀₇ to improve direction finding accuracy, the diameter of the cylinder increases linearly [Smaryshev M.D. Elements of the theory of directionality of hydroacoustic antennas. St. Petersburg: Publishing house of St. Petersburg Electrotechnical University "LETI", 2003]. In addition, shielding of the rear surface of the receivers is required, which creates additional technical problems for the formation of patterns with high directivity at low frequencies. To build a screenless receiver, a receiver that forms a cardioid pattern can be used [Smaryshev M.D. … With. 56-60].

A known method and device for determining the direction to the source of a sound signal by a diver [RF patent No. 2439602, IPC G01S 7/52, publ. 08.27.2011], which proposes the formation of a “reverse” cardioid pattern. In this device, the pattern is formed by two omnidirectional hydrophones, the centers of which are located at a distance of a quarter of the wavelength of the carrier frequency of the received signal. The formation path consists of a signal delay device for a time equal to a quarter of the carrier frequency period of the received signal, a adder and an amplifier with automatic gain control (AGC). Moreover, the gain of an amplifier with automatic gain control (AGC) is inversely proportional to the level of the control signal. At the output of this amplifier, a pattern is formed that is “reverse” to the cardioid pattern, the axis of which is directed along the line connecting the receivers. However, the proposed device does not allow the formation of a pattern fan.

The closest technical and functional characteristics to the proposed device is the “Small-sized direction finder of hydroacoustic signals” [RF Patent No. 2793149, IPC G01S 1/801, publ. 03.29.2023], which was adopted as a prototype.

The prototype device contains a cylindrical, sound-transparent hydroacoustic antenna, on the circumference of which 2N hydroacoustic receivers (HAR) are located. The diameter of the circle is D=λ/4, where λ is the wavelength at the average frequency of the received signal, the centers of the receivers are at the same angular distance Δθ°=360/(2N) from each other,

The receivers are connected to a 2N-channel spatial channel generating unit, configured to form a static fan of 2N spatial channels (SC) in a range of angles of 360°, in each of which a “reverse” cardioid radiation pattern is formed. Also, the prototype device contains a 2N-channel bearing determination unit, where PC _m is determined, in which the maximum value of the received signal is recorded. The direction θ _m of the axis of the beam of this PC is accepted as the direction to the signal source and, using the transmission unit, the bearing value is transmitted to external devices.

The direction finder, declared in RF patent No. 2793149, forms a static fan of 2N spatial channels with a small diameter of the cylindrical antenna. The main disadvantage of the presented technical solution is the low angular resolution, i.e. large error in determining the bearing to the target, because the direction to the direction-finding signal source is determined with an accuracy of no more than half the width of the pattern Δθ ₀₇ . Increased accuracy in the prototype device can only be achieved by increasing the number of receivers.

The objective of the invention is to increase the accuracy of the amplitude direction finding method used in signal detection mode using a static PC fan, without increasing the number of receivers. The technical result of the invention is to significantly increase the accuracy of direction finding, while maintaining the dimensions of the antenna, the number of receivers and without shielding the receivers.

To solve the problem posed in a direction finder containing a sound-transparent multi-element cylindrical hydroacoustic antenna consisting of N omnidirectional hydroacoustic receivers A _n (n = 1, 2, ..., N) and N omnidirectional hydroacoustic receivers B _n , and the phase centers of all 2N hydroacoustic receivers are evenly placed with an angular step Δθ=(360/2N)° along a circle with a diameter of D=λ/4, where λ is the wavelength at the average frequency of the received signal; 2N-channel block for generating spatial channels, configured to form a static fan from 2N spatial channels (SC), with the formation in each of the PC of a directional pattern (DP) of the “reverse” cardioid type; 2N-channel block for selecting the spatial channel PC _m , configured to determine the PC with the maximum signal and a block for generating the bearing value θ _m corresponding to the direction of the maximum DP PC _m ; in this case, the outputs of all 2N hydroacoustic receivers are connected to 2N inputs of the spatial channel formation block, 2N outputs of the spatial channel formation block are connected to 2N inputs of the spatial channel selection block PC _m , and the output of the spatial channel selection block PC _m is connected to the input of the bearing value generation block,

additionally introduced

a key block consisting of 2N normally closed keys Cl _A1, ..., Cl _AN , Cl _B1, ..., Cl _BN ;

block for generating control signals;

comparison block;

memory block and bearing clarification block,

in this case, all 2N outputs of the spatial channel formation block are additionally connected to the signal inputs of the same keys Cl _A1, ..., Cl _AN , Cl _B1 , ... Cl _BN ;

the output of the spatial channel selection block PC _m is additionally connected to the input of the control signal generation block;

2N outputs of the control signal generation block are connected to the control inputs of keys of the same name, and the control signal generation block is configured to open two keys Key _left and Key _right corresponding to PCs adjacent to the channel PC _m on the left (PC _left ) and on the right (PC _right );

the outputs of 2N keys are connected to the 2N inputs of the comparison block, and its output is connected to the input of the memory block;

the output of the bearing value generation block is connected to the first input of the bearing clarification block, and the output of the memory block is connected to the second input of the bearing clarification block.

The technical result of the invention - increasing accuracy - is ensured by comparing signals in spatial channels adjacent to the selected channel PC _m , in which the signal received from the source has the maximum value. In this case, a correction is introduced to the direction θ _m , depending on the difference in voltages at the outputs of PC _right and PC _left .

The introduction of new features provides a significant increase in the accuracy of determining the direction to the signal source, while the increase in accuracy is achieved without increasing the number of receivers.

The essence of the invention is illustrated in Fig. 1-4. In fig. 1 shows the general functional diagram of the device; in fig. Figure 2 shows a functional diagram for selecting the PC _pr and PC _lev channels, the signals of which are used to clarify the bearing to the source. In fig. Figure 3 shows the dependence connecting the introduced angular correction with the difference in voltages of signals from the source coming from spatial channels adjacent to the PC channel _m (for ΔU≥0), and in Fig. 4 explains the principle of determining the voltage difference. In fig. 4 indicated: solid curve - angular dependence of voltage from PC channel _m , dotted line a similar dependence for the right channel PC _{m relative to PC m ,} and the dash-dotted line for the left channel PC _lion .

The direction finder consists of a cylindrical antenna 1 and a radio part. On the guide cylindrical antenna there are hydroacoustic receivers HAP _An 1 _An and also hydroacoustic receivers HAP _Bn 1 _Bn shifted by 180° (n=1,2, ..., N). The radio engineering part of the direction finder includes a 2N-channel spatial channel formation unit (BFPK 2), which is designed to form a static fan of PCs, in each of which a “reverse” cardioid pattern is formed. BFPK 2 is connected to a 2N-channel spatial channel selection block (BVPK 3), and each channel of BFPK 2 is connected to the signal inputs of the same keys Kl _Ap and Kl _Bn of key block 4. The output of BVPK 3 is connected to the input of the control signal generation block (BFUS 5 ) and with the input of the bearing value generation block (BFZP 6).

The output of BFUS 5 is connected to 2N control inputs of the key block 4, while only two channels transmit control signals to open two keys.

Two outputs of the public keys of the key block 4 are connected to the inputs of the comparison block (BSr 7), and the output of the BSr 7 is connected to the input of the memory block (BPm 8).

The output of the BFZP block 6 is connected to the first input of the bearing clarification block (BUP 9), and the second input of BUP 9 is connected to the output of the BPM 8 block.

From the output of the TCU 9, the updated bearing value _is transmitted to the signal source θ source for further processing.

The claimed device is completed from known acoustic and radio-electronic devices. Small-sized hydroacoustic receivers are mass-produced by domestic and foreign industry. The electronic blocks included in the processing circuits are implemented as hardware and software, and the additionally introduced key block 4, control signal generation block 5, bearing value transmission block 6, comparison block 7, memory block 8 and bearing clarification block 9 should be formed on the basis computer facilities

The proposed direction finder works as follows.

The acoustic signal from the source is received by cylindrical antenna 1, converted into an electrical signal and supplied to the inputs of the multichannel block for generating spatial channels BFPK 2. At the output of BFPK 2, an array of signals is formed corresponding to a static fan of 2N spatial channels (SC), and a diagram is formed in each channel directivity (DN) of the “reverse” cardioid type (a description of the method of such formation and the device that implements this method is presented in RF patent No. 2793149).

An array of signals from the generated spatial channels is transmitted to a 2N-channel spatial channel selection block (BVPK 3), where the maximum signal corresponding to the spatial channel PC _m is selected from the entire array. Simultaneously with the transmission of an array of signals to BVPK 3, the same signals are transmitted to the signal inputs of the keys of the same name key block 4.

From block BFPK 3, the channel number PC _m is transmitted to the block (see Fig. 2) for generating control signals (BFUS 5) and to the block for generating the bearing value (BFZP 6), where according to the number of the selected PC _m, the direction to the source signal θ _m is formed, in degrees. In the BFUS block 5, according to the value of the transmitted PC number _m , control signals are generated to open the keys in the key block 4 to the left and right of the key Kl _m : respectively, the key Kl _left and the key Kl _right . The remaining keys of key block 4 remain private.

Through public keys Kl _lev, Kl _pr, signals (voltages) from the spatial channels PC _{lev, pr} reach the inputs of the comparison block BSr 7. In the block BSr 7, a voltage difference ΔU=U _pr -U _left is formed, where U _lev is the voltage value from the spatial channel PC _left , U _np - voltage value from the spatial channel PC _right (all voltages in dB). The calculated voltage difference is transmitted to the input of the memory block BPM 8.

The memory block BPm 8 is designed to determine the correction for the direction finding angle to the source ξ _θ from the voltage difference between the signals from the right and left spatial channels relative to the spatial channel PC _m , equal to ΔU and transmitted to the input of BPm 8. The correction is determined by the dependence ξ _θ (ΔU) [see. Kranz V.Z., Ostrovsky D.B. On the use of cardioid radiation patterns for direction finding of hydroacoustic signals // Hydroacoustics, 2022, no. 51(3), p. 5-11]. The table of values of the function that determines the dependence ξ _θ (ΔU) is pre-loaded into the memory of the BPM 8 block, which makes it possible to determine the correction ξ _θ corresponding to the voltage ΔU (for illustration, a typical dependence of the correction ξ _θ in degrees, on voltage, in dB, is shown in Fig. 3).

In fig. Figure 4, which shows a fragment of the voltage fan from spatial channels depending on the angle of arrival of the signal, shows how the value of ΔU is determined. As was indicated, the maximum value of the signal from the source is fixed in PC _m , the axis of the pattern of this channel is in the direction of θ _m . However, the direction to the source θ _source may not coincide with θ _m , but be within angular limits equal to the width of the BP maximum. Shown in FIGS. 4, the curves do not adjoin each other, but intersect, from which it follows that signals of a lower level than in PC _m will also be detected in the channels PC _left and PC _right , the corresponding voltage levels are marked on the line θ source _with dots. The points of intersection of the curves of the dependences on the voltage angle of the PC _pr and PC _left channels with the line θ _source correspond to the voltages U _np and U _left , from which the difference ΔU is determined.

The rough value of the bearing θ _m (in degrees) from the output of the BFZP block 6 is supplied to the first input of the bearing clarification block BUP 9; its second input receives a correction ξ _θ , also in degrees. The direction to the source θ _source is determined in block BUP 9 by the formula θ _source =θ _m +ξ _θ .

Thus, the declared technical effect is achieved, consisting of a significant increase in direction finding accuracy, while maintaining the dimensions of the antenna, the total number of receivers, and there is no need for shielding of the receivers.

The claimed hydroacoustic direction finder can be used to monitor the underwater situation when installed on small-sized carriers where there is no possibility of placing large-diameter antennas, including for bottom hydrophysical stations and hydroacoustic stations lowered from helicopters.

Claims (1)

A direction finder of hydroacoustic signals containing a sound-transparent multi-element cylindrical hydroacoustic antenna consisting of N omnidirectional hydroacoustic receivers A _n (n=1, 2, ..., N) and N omnidirectional hydroacoustic receivers B _n , and the phase centers of all 2N hydroacoustic receivers are evenly spaced with an angular step Δθ=360/2N along a circle with diameter D=λ/4, where λ is the wavelength at the average frequency of the received signal; 2N-channel unit for generating spatial channels, configured to form a static fan from 2N spatial channels (SC), with the formation in each of the PC of a directional pattern (DP) of the “reverse” cardioid type; A 2N-channel block for selecting a spatial channel PC _m with a maximum signal and a block for generating a bearing value θ _m corresponding to the direction of the maximum DP PC _m , while the outputs of all 2N hydroacoustic receivers are connected to the 2N inputs of the spatial channel formation block, 2N outputs of the spatial channel formation block are connected with 2N inputs of the spatial channel selection block PC _m , and the output of the spatial channel selection block PC _m is connected to the input of the bearing value generation block, characterized in that a key block containing 2N normally closed keys Cl _A1 , ..., Cl _AN is introduced into the hydroacoustic signal direction finder , Cl _B1 , ..., Cl _BN, control signal generation block, comparison block, memory block and bearing clarification block, while all 2N outputs of the spatial channel generation block are additionally connected to the signal inputs of the same name keys Cl _A1 , ..., Cl _AN, Cl _B1 , …, Cl _BN ; the output of the spatial channel selection block PC _m is additionally connected to the input of the control signal generation block, 2N outputs of the control signal generation block are connected to the control inputs of keys of the same name, and the control signal generation block is configured to open two keys Cl _l and Cl _p corresponding to the PC adjacent with channel PC _m on the left (PC _lev ) and on the right (PC _pr ), the outputs of 2N keys are connected to the 2N inputs of the comparison block, and its output is connected to the input of the memory block, the output of the bearing value generation block is connected to the first input of the bearing clarification block, and the output The memory block is connected to the second input of the bearing clarification block.

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