CN104199014A

CN104199014A - Coded signal based simultaneous multi-focus shallow water multi-beam emission focusing system

Info

Publication number: CN104199014A
Application number: CN201410452834.6A
Authority: CN
Inventors: 李海森; 鲁东; 魏玉阔; 徐超; 朱建军; 周天; 李若
Original assignee: Harbin Engineering University
Current assignee: Harbin Engineering University
Priority date: 2014-09-05
Filing date: 2014-09-05
Publication date: 2014-12-10
Anticipated expiration: 2034-09-05
Also published as: CN104199014B

Abstract

The invention discloses a coded signal based simultaneous multi-focus shallow water multi-beam emission focusing system. A spread spectrum sequence storage module outputs spread spectrum sequence codes to corresponding 2PSK modulators; the 2PSK modulators modulate received signals to central frequency points of underwater acoustic transducers and output the signals to corresponding near-field fixed-focus delayed emission focusing modules; the near-field fixed-focus delayed emission focusing modules generate spread spectrum code focusing signals of a first channel to an M-th channel and output the spread spectrum code focusing signals to corresponding accumulator modules; each accumulator module accumulates the received N spread spectrum code focusing signals of the same channel and outputs the accumulated result to each corresponding power emission module; each power emission module converts the received signals into high-power signals and outputs the high-power signals to emitting array elements of the underwater acoustic transducers; the M emitting array elements of the underwater acoustic transducers form multi-focus focusing beams. The coded signal based simultaneous multi-focus shallow water multi-beam emission focusing system effectively improves longitudinal resolution of the near-field multi-beam sounding, and improves the comprehensive precision of the shallow water multi-beam.

Description

A kind of multifocal some shallow water beam transmitting focusing system based on coded signal time

Technical field

The invention belongs to multibeam echosounding field, relate in particular to and can solve transmitting near-field effect, a kind of multifocal some shallow water beam transmitting focusing system based on coded signal time.

Background technology

Field angle is the measurement precision important indicator in multibeam echosounder, by flight path direction angle of release and path in elevation direction angle of release, is determined, directly affects regulation of longitudinal angle resolving power and lateral angles resolving power.In conventional multibeam echosounder, affected by near-field effect, lateral angles resolving power is guaranteed by near field dynamic focusing method, and near field regulation of longitudinal angle resolving power declines to some extent because transmitting does not focus on.

For solving near field transmitting problem, part multibeam echosounder has adopted single focus launching technique, but larger for single measurement coverage in multibeam echosounding, usually can only improve the resolving power on focal length, be distal to focus and will significantly decline with the along track resolution that is bordering on the depth measurement region of focus.

Summary of the invention

The object of this invention is to provide the along track resolution that can improve near field multibeam echosounding, a kind of multifocal some shallow water beam transmitting focusing system based on coded signal time.

The present invention is achieved by the following technical solutions:

A multifocal some shallow water beam transmitting focusing system in the time of based on coded signal, is characterized in that: comprise N frequency expansion sequence memory module, a N 2PSK modulator, a N near field fixed-focus delay emission focus module, a M accumulator module, a M power emission module and M underwater acoustic transducer transmitting array element;

In N frequency expansion sequence memory module, store respectively spread spectrum code sequence, the corresponding 2PSK modulator of each frequency expansion sequence memory module, outputs to For Spread Spectrum Sequences in corresponding 2PSK modulator with electrical signal form;

The corresponding near field fixed-focus delay emission focus module of each 2PSK modulator, is modulated to the spread spectrum code sequence receiving in the center frequency point of underwater acoustic transducer, with electrical signal form, outputs to corresponding near field fixed-focus delay emission focus module;

The respectively corresponding predefined near field focus point of each near field fixed-focus delay emission focus module, different delay according to predefined near field focus point to each underwater acoustic transducer transmitting array element, the signal receiving is converted and obtains M spreading code focus signal, M spreading code focus signal obtained to first passage to the spreading code focus signal of M passage by passage sequence, the corresponding accumulator module of each passage, exports to corresponding accumulator module by first passage to the spreading code focus signal of M passage;

The corresponding power emission module of each accumulator module, each accumulator module by receive N spreading code focus signal of same channels add up, with electrical signal form, export to corresponding power emission module;

Each power emission module is converted to high-power signal by the signal receiving, and outputs to a corresponding underwater acoustic transducer transmitting array element;

M underwater acoustic transducer transmitting array element is converted to acoustical signal by the high-power signal receiving, and forms multiple-point focusing wave beam.

A kind of multifocal some shallow water beam transmitting focusing system based on coded signal time of the present invention, can also comprise:

1, spread spectrum code sequence adopts Kasami sequence.

2, the predefined near field focus point that first near field fixed-focus delay emission focus module calculates its correspondence arrives each underwater acoustic transducer transmitting array element and the path difference that arrives whole transducer array central point; Then according to path difference, calculate predefined near field focus point to the different delay of each underwater acoustic transducer transmitting array element; Finally according to different delay, produce M the spreading code focus signal that time delay is different, waveform is identical with the signal receiving.

Beneficial effect of the present invention is:

The present invention takes full advantage of autocorrelation performance and the their cross correlation that Kasami spread spectrum coded signal is good, by the present invention by different coding signal transmitting focusing on the focus of different distance, effectively reduce the field angle of near field launching beam, solve near field transmitting in conventional multibeam echosounder and do not focused on two problems that cause the single focus focusing of the decline of near-field resolution power and near field to cause non-focal length resolving power degradation, can carry out while multifocal some transmitting focusing by the present invention, can effectively improve the along track resolution of near field multibeam echosounding, improve the synthesis precision of shallow water multi-beam.

Accompanying drawing explanation

Fig. 1 system chart of the present invention;

Backward energy distribution plan when Fig. 2 beam transmitting does not focus on;

Backward energy distribution plan when Fig. 3 beam transmitting single-point focuses on;

Fig. 4 is the multifocal some backward energy distribution plan that shallow water beam transmitting focuses on based on coded signal time.

Embodiment

Below in conjunction with accompanying drawing, the present invention is described in further details.

A kind of multifocal some shallow water beam transmitting focusing system based on coded signal time of the present invention, comprises N group frequency expansion sequence memory module 11～1N, N group 2PSK modulator 21～2N, N group near field fixed-focus delay emission focus module 31～3N, M group accumulator module 51～5M, M group power emission module 61～6M and M group underwater acoustic transducer transmitting array element 71～7M; N represents the focus number in this device, and M represents the number of launching array element in multibeam echosounding.

Principle of work of the present invention is:

By N being organized to separate Kasami spread spectrum coded signal 11～1N, by 2PSK modulator 21～2N, be modulated in the center frequency point of transducer respectively, then respectively by near field fixed-focus delay emission focus module 31～3N, by presetting focus to every channel transmit signal 411～41M, 421～42M, 431～43M does respectively time delay, produce respectively M and organize transmitting of different passages, again N is organized to different focus signals and input to respectively cumulative being transmitted of M group accumulator module 51～5M, finally by power emission module 61～6M, will transmit and be converted into power signal and be sent to underwater acoustic transducer array element 71～7M and realize electroacoustic conversion, just can form multiple-point focusing wave beam thus.

Accumulator module, adopt digital accumulator or simulation totalizer, receive the spreading code focus signal that near field fixed-focus delay emission focus module produces, each channel signal is corresponding cumulative, wherein first group of accumulator module 51 receives first passage 411, 421, 431 signal adds up and outputs to first group of power emission module 61 with electrical signal form, second group of accumulator module 52 receives second channel 412, 422, 432 signal adds up and outputs to second group of power emission module 62 with electrical signal form, M group accumulator module 5M receives M passage 41M, 42M, the signal of 43M adds up and outputs to M group power emission module 6M with electrical signal form.

Specific embodiment is:

A multifocal some shallow water beam transmitting focusing system in the time of based on coded signal, its structure comprises 5 groups of frequency expansion sequence memory modules; 5 groups of 2PSK modulators; 5 groups of near field fixed-focus delay emission focus module; 80 groups of accumulator module; 80 groups of power emission modules; 80 groups of underwater acoustic transducers transmitting array elements, at this with implementation example explanation in programmable gate array.

5 groups of frequency expansion sequence memory modules, for storing 5 groups of separate spread spectrum code sequences, 5 groups of frequency expansion sequences adopt method for optimizing to select, to guarantee its good cross correlation and autocorrelation of self each other, because code element in frequency expansion sequence just forms and negligible amounts with 0 and 1, in programmable gate array, be put into storage in register;

5 groups of 2PSK modulators, adopt binary phase shift keying modulation method, for spread spectrum code sequence being modulated to the center frequency point of transducer, because underwater acoustic transducer itself has good narrow-band characteristic, this part can consider result to represent by single-bit form, it is convenient that this device is realized at programmable gate array, takies logical resource less;

5 groups of near field fixed-focus delay emission focus module, for every channel transmit signal being done to time delay by default focus, produce respectively transmitting of 5 groups of different passages, this part can be in programmable gate array realizes easily by the structure that shift register adds MUX;

80 groups of accumulator module, by the respective channel data accumulation of each focus, directly utilize programmable gate array internal logic resource conveniently to realize;

80 groups of power emission modules, are converted to high-power signal by digital signal, and this part can be used high efficiency D class power amplifier;

80 groups of underwater acoustic transducers transmitting array elements, for converting electrical signals to acoustical signal, adopt the underwater sound transmitting transducer of frequency centered by 180 KHz in this example.Concrete structure as shown in Figure 1.

For verifying advantage of the present invention, take 2 meters of dark flat seabeds is target, underwater sound transmitting transducer array element adopts 80, the half-wavelength mode of structuring the formation, simulation analysis each array element launch the backward energy distribution plan in same signal out-focus situation, as shown in Figure 2, can see clearly while forming multibeam echosounding band, outside has narrower wave beam, and arrives beam broadening nearby, and resolving power declines; Then simulation analysis 2 meters of backward energy distribution plans that focus in single-point focusing situations of each array element transmitting, as shown in Figure 3, can see clearly while forming multibeam echosounding band, only have at nearest 2 meters of and there is narrower wave beam, and broaden to outer beams, resolving power declines; Finally apparatus of the present invention are applied in this scene, 5 focuses are set, focal length is respectively 1.3 meters, 2.3 meters, 4 meters, 7 meters and 25 meters of simulation analysis and obtains backward energy distribution plan, as shown in Figure 4, can find out clearly, no matter near field and far field, beam angle is all narrower, and resolving power is all higher.Comparison diagram 2, Fig. 3 and Fig. 4, can find out superiority of the present invention.

Claims

1. a multifocal some shallow water beam transmitting focusing system in the time of based on coded signal, is characterized in that: comprise N frequency expansion sequence memory module, a N 2PSK modulator, a N near field fixed-focus delay emission focus module, a M accumulator module, a M power emission module and M underwater acoustic transducer transmitting array element;

2. a kind of multifocal some shallow water beam transmitting focusing system based on coded signal time according to claim 1, is characterized in that: described spread spectrum code sequence adopts Kasami sequence.

3. a kind of multifocal some shallow water beam transmitting focusing system based on coded signal time according to claim 1 and 2, is characterized in that: the predefined near field focus point that first described near field fixed-focus delay emission focus module calculates its correspondence arrives each underwater acoustic transducer transmitting array element and the path difference that arrives whole transducer array central point; Then according to path difference, calculate predefined near field focus point to the different delay of each underwater acoustic transducer transmitting array element; Finally according to different delay, produce M the spreading code focus signal that time delay is different, waveform is identical with the signal receiving.