阅读说明：本技术 一种基于双路正交检测的水下电流场探测系统及方法 (Underwater current field detection system and method based on double-path orthogonal detection ) 是由 李北明 胡友芳 薛伟 尚文静 刘明新 徐以东 李想 金荣璐 于 2021-06-22 设计创作，主要内容包括：本发明属于水下无线探测技术领域,具体涉及一种基于双路正交检测的水下电流场探测系统及方法。本发明通过2次的波谷波峰状态变化,进行水下金属物的探测和验证,大大提高水下或水底金属物探测的灵敏度和可靠性,使用探测信号的更多有用信息进行判决,比传统的只依靠幅度判断灵敏度更高,而且克服了由于环境变化引起检测门限变化导致检测效果较差的问题,避免了设置检测门限的困难。本发明解决了现有水下电流场探测方法检测电压变化太小或者由于环境变化引起检测门限变化导致检测效果较差和误报警高的问题,通过双路正交检测提高有效性和可靠性。(The invention belongs to the technical field of underwater wireless detection, and particularly relates to an underwater current field detection system and method based on double-path orthogonal detection. The invention carries out detection and verification on underwater metal objects through 2 times of wave trough and wave crest state changes, greatly improves the sensitivity and reliability of underwater or underwater metal object detection, judges by using more useful information of detection signals, has higher sensitivity than the traditional judgment method only depending on amplitude, overcomes the problem of poor detection effect caused by detection threshold changes due to environmental changes, and avoids the difficulty of setting the detection threshold. The invention solves the problems of poor detection effect and high false alarm caused by too small detection voltage change or detection threshold change caused by environment change in the existing underwater current field detection method, and improves the effectiveness and reliability through two-way orthogonal detection.)

1. The utility model provides an underwater current field detecting system based on double-circuit quadrature detection which characterized in that: the device comprises an antenna unit, a transmitting unit (4), a receiving unit (5), a digital control unit (6) and an upper computer two-way orthogonal detector decision unit (7); the antenna unit comprises a transmitting antenna unit (1), an A-end receiving antenna unit (2) and a B-end receiving antenna unit (3); the digital control unit (6) comprises a controller (601), a DA module (602), a first AD module (603) and a second AD module (604); the transmitting unit (4) comprises a power amplifier (401) and an impedance matching network (402); the receiving unit comprises a first balun frequency-selecting loop (501) and a second balun frequency-selecting loop (502); the upper computer two-way orthogonal detector decision unit (7) comprises a first chaotic detector (703) and a second chaotic detector (704);

the controller (601) generates a sine wave digital signal, and the sine wave digital signal is generated by the DA module (602) and transmitted to the power amplifier (401) of the transmitting unit (4); the power amplifier (401) amplifies the power of the sine wave signal and transmits the sine wave signal to the transmitting antenna unit (1) through the impedance matching network (402); the transmitting antenna unit (1) radiates the received power signal into water, and transmits the weak reflected signal received by induction to the A-end receiving antenna unit (2) and the B-end receiving antenna unit (3); the A-end receiving antenna unit (2) transmits the received and induced weak reflected electric field signals in water to a first balun frequency selection loop (501) of the receiving unit (5), and the B-end receiving antenna unit (3) transmits the received and induced weak reflected electric field signals in water to a second balun frequency selection loop (502) of the receiving unit (5); the first balun frequency-selecting loop (501) converts the received differential electric signal into a single-ended voltage signal, and transmits the single-ended voltage signal to a first AD module (603) of the digital control unit (6) after being processed by a low-noise amplifier, a band-pass filter and a secondary amplifier in sequence; the second balun frequency selection loop (502) converts the received differential electric signal into a single-ended voltage signal, and transmits the single-ended voltage signal to a second AD module (604) of the digital control unit (6) after being processed by a low noise amplifier, a band-pass filter and a secondary amplifier in sequence; the first AD module (603) and the second AD module (604) respectively carry out AD conversion on the received signals and then transmit the converted signals to the judgment unit (7) of the two-way orthogonal detector of the upper computer through the man-machine interaction interface (605);

after the upper computer two-way orthogonal detector decision unit (7) receives the signals transmitted by the first AD module (603) and the second AD module (604), the signals transmitted by the first AD module (603) and the same-direction branch signals (701) of the local carrier are multiplied and integrated to obtain a first multiplication integral value (703); multiplying and integrating the signal transmitted by the second AD module (604) with an orthogonal branch signal (702) of the local carrier to obtain a second product score (704); when no metal object exists underwater or underwater in the detection range of the A-end receiving antenna unit (2) and the B-end receiving antenna unit (3), adjusting the phases of a cocurrent branch signal (701) and an orthogonal branch signal (702) of a local carrier to enable the local carrier to be approximately orthogonal to signals transmitted by a first AD module (603) and a second AD module (604), and acquiring a ratio (705) of a first multiplied integral value (703) and a second multiplied value (704);

if metal objects exist underwater or on the water bottom in the detection range of the A-end receiving antenna unit (2), the ratio (705) of the first multiplied integral value (703) to the second multiplied integral value (704) becomes smaller, and a trough appears; if there is a metal object underwater or on the water bottom within the detection range of the B-end receiving antenna unit (2), the ratio 705 of the first multiplied integral value 703 to the second multiplied integral value 704 becomes large and a peak appears.

2. The underwater current field detection system based on two-way orthogonal detection as claimed in claim 1, wherein: the antenna unit is arranged on an antenna bracket (105); the antenna bracket (105) comprises a vertical rod piece and a horizontal cross-shaped bracket; the horizontal cross-shaped bracket consists of a first horizontal rod piece and a second horizontal rod piece which are vertically crossed with the point O; the lower end of the vertical rod piece is connected to a point O of the cross-shaped support; the transmitting antenna unit (1), the A-end receiving antenna unit (2) and the B-end receiving antenna unit (3) are electric dipole antennas, two conductors of the transmitting antenna unit (1) are respectively arranged on two sides of a point O on the first horizontal rod, two conductors of the A-end receiving antenna unit (2) are arranged on one side of the point O on the second horizontal rod, two conductors of the B-end receiving antenna unit (3) are arranged on the other side of the point O on the second horizontal rod, and all the conductors are arranged around the point O in a central symmetry mode.

3. The underwater current field detection system based on two-way orthogonal detection as claimed in claim 2, characterized in that: the conductors of the transmitting antenna unit (1), the A-end receiving antenna unit (2) and the B-end receiving antenna unit (3) adopt carbon rods or silver chloride metal rods, the surfaces of the conductors are smooth and have no burrs, the upper ends of the conductors are tightly wrapped by copper foils connected with wires to be used as antenna feeders, the connection points of the wires are insulated and sealed by polyester materials, and the upper ends of the conductors are sealed by adhesive tapes.

4. The underwater current field detection method based on the two-way orthogonal detection of the underwater current field detection system based on the two-way orthogonal detection as claimed in claim 1 is characterized by comprising the following steps:

step 1: mounting an antenna unit on an antenna mount (105); the antenna bracket (105) comprises a vertical rod piece and a horizontal cross-shaped bracket; the horizontal cross-shaped bracket consists of a first horizontal rod piece and a second horizontal rod piece which are vertically crossed with the point O; the lower end of the vertical rod piece is connected to a point O of the cross-shaped support; the transmitting antenna unit (1), the A-end receiving antenna unit (2) and the B-end receiving antenna unit (3) are all electric dipole antennas, two conductors of the transmitting antenna unit (1) are respectively arranged on two sides of a point O on the first horizontal rod piece, two conductors of the A-end receiving antenna unit (2) are arranged on one side of the point O on the second horizontal rod piece, two conductors of the B-end receiving antenna unit (3) are arranged on the other side of the point O on the second horizontal rod piece, and all the conductors are arranged around the point O in a central symmetry manner;

step 2: putting an antenna bracket (105) provided with an antenna unit under water, wherein the horizontal cross-shaped bracket part is parallel to the detection water bottom; the antenna bracket (105) is moved in parallel to detect, and the detection direction is the advancing direction of the A-end receiving antenna unit (2);

and step 3: when a wave trough appears when the ratio (705) of the first multiplied integral value (703) and the second multiplied integral value (704) is detected to be smaller, the A-end receiving antenna unit (2) is judged to be in the detection range and metal exists underwater or under the water;

and 4, step 4: as the antenna mount (105) on which the antenna unit is mounted continues to move forward, the ratio (705) of the first multiplied integral value (703) to the second multiplied integral value (704) increases until a peak occurs, verifying the metal object detected in step 3.

5. The underwater current field detection method based on two-way orthogonal detection as claimed in claim 4, characterized in that: the conductors of the transmitting antenna unit (1), the A-end receiving antenna unit (2) and the B-end receiving antenna unit (3) adopt carbon rods or silver chloride metal rods, the surfaces of the conductors are smooth and have no burrs, the upper ends of the conductors are tightly wrapped by copper foils connected with wires to be used as antenna feeders, the connection points of the wires are insulated and sealed by polyester materials, and the upper ends of the conductors are sealed by adhesive tapes.

Technical Field

The invention belongs to the technical field of underwater wireless detection, and particularly relates to an underwater current field detection system and method based on double-path orthogonal detection.

Background

Modern underwater detection has increasingly high requirements for effectiveness and reliability. The traditional underwater detection technology mainly comprises sonar, underwater optical detection technology and traditional underwater current field detection technology. Because the underwater acoustic signals have good propagation characteristics under water, the sonar becomes the most widely applied technology in the underwater detection technology, and is commonly used for detecting submarine topography drawing, ship debris searching and other purposes. However, the sound waves are easy to refract, reflect and scatter in the process of underwater propagation, and the underwater noise environment is complex and changeable, which can interfere the detection effect of the sonar. And the active sonar needs to emit sound waves for detection, so that the position of the active sonar is easy to expose, and the position of the active sonar is exposed when the echo is received due to the low transmission speed of the sound waves, so that the active sonar is almost abandoned in many occasions. The underwater optical detection technology mainly comprises an underwater laser detection technology and an underwater television technology. The underwater laser technology is mainly used on an aerial anti-submarine aircraft, the principle of the underwater laser technology is similar to that of echo positioning, blue-green laser is transmitted and received by a laser radar, and the whole transmission link comprises air and seawater, so that the detection precision is seriously influenced by various interferences such as atmospheric attenuation, sea surface reflection, seawater attenuation and scattering, the influence of a seawater environment and the like, and the underwater laser technology is only suitable for a shallow sea area with a clear water body; the underwater television technology adopts a mode that a camera shoots underwater targets to realize detection. Because the light is in the process of propagating under water, the absorption effect of water and particles to light is very obvious, even if a blue-green light source which is influenced the least is used, the effective detection distance is only 30 meters at most, and under a turbid water body environment, the light generates a scattering effect on an underwater propagation path, cannot reach a detection target completely, and part of the light can be scattered back to the light source, so that the visibility is reduced, and the detection effect is greatly influenced.

The sonar technology and the underwater optical detection technology have defects and shortcomings in underwater detection, and cannot be well applied to various complicated and changeable underwater environments, particularly detection in underwater turbid and underwater reef cluster environments. For better detection of the marine environment, more diverse means are needed for underwater detection. The traditional underwater current field detection technology uses a hard decision threshold to judge, and if the electric field of the surrounding background environment changes, the hard decision threshold needs to be adjusted differently so as to adapt to the change of the electric field of the surrounding background environment. The underwater current field detection method based on the two-way orthogonal detection can overcome the problems of poor detection effect and high false alarm caused by detection threshold change caused by environment change in the traditional underwater current field detection method, improves the detection effectiveness and reliability, and makes up the defects of the traditional underwater detection technology to a certain extent. The underwater current field detection method based on the two-way orthogonal detection greatly reduces the dependence of the surrounding environment, has a simple detection system structure, is very suitable for being used in dark and turbid coastal water areas, greatly improves the detection precision, avoids the problem of low reliability and poor effectiveness caused by detection only depending on a hard threshold, and can be applied to the fields of large-scale underwater robots, AUV underwater detection and the like.

Disclosure of Invention

The invention aims to provide an underwater current field detection system based on double-path orthogonal detection.

The purpose of the invention is realized by the following technical scheme: the device comprises an antenna unit, a transmitting unit 4, a receiving unit 5, a digital control unit 6 and an upper computer two-way orthogonal detector decision unit 7; the antenna unit comprises a transmitting antenna unit 1, an A-end receiving antenna unit 2 and a B-end receiving antenna unit 3; the digital control unit 6 comprises a controller 601, a DA module 602, a first AD module 603, and a second AD module 604; the transmitting unit 4 comprises a power amplifier 401 and an impedance matching network 402; the receiving unit comprises a first balun frequency-selecting loop 501 and a second balun frequency-selecting loop 502; the upper computer two-way orthogonal detector decision unit 7 comprises a first chaotic detector 703 and a second chaotic detector 704;

the controller 601 generates a sine wave digital signal, and the sine wave digital signal is generated by the DA module 602 and transmitted to the power amplifier 401 of the transmitting unit 4; the power amplifier 401 amplifies the power of the sine wave signal and transmits the amplified sine wave signal to the transmitting antenna unit 1 through the impedance matching network 402; the transmitting antenna unit 1 radiates the received power signal into water and transmits the weak reflected signal received by induction to the A-end receiving antenna unit 2 and the B-end receiving antenna unit 3; the terminal a receiving antenna unit 2 transmits the received and sensed signal of the underwater weak reflection electric field to a first balun frequency-selective loop 501 of the receiving unit 5, and the terminal B receiving antenna unit 3 transmits the received and sensed signal of the underwater weak reflection electric field to a second balun frequency-selective loop 502 of the receiving unit 5; the first balun frequency-selecting loop 501 converts the received differential electrical signal into a single-ended voltage signal, and transmits the single-ended voltage signal to the first AD module 603 of the digital control unit 6 after being processed by a low-noise amplifier, a band-pass filter and a secondary amplifier in sequence; the second balun frequency-selecting loop 502 converts the received differential electrical signal into a single-ended voltage signal, and transmits the single-ended voltage signal to the second AD module 604 of the digital control unit 6 after being processed by the low-noise amplifier, the band-pass filter and the secondary amplifier in sequence; the first AD module 603 and the second AD module 604 respectively perform AD conversion on the received signals and transmit the converted signals to the decision unit 7 of the two-way orthogonal detector of the upper computer through the man-machine interaction interface 605;

after receiving the signals transmitted by the first AD module 603 and the second AD module 604, the upper computer two-way orthogonal detector decision unit 7 performs multiplication and integration on the signal transmitted by the first AD module 603 and the same-direction branch signal 701 of the local carrier to obtain a first multiplication integral value 703; multiplying and integrating the signal transmitted by the second AD module 604 with the orthogonal branch signal 702 of the local carrier to obtain a second product score 704; in the detection range of the end-a receiving antenna unit 2 and the end-B receiving antenna unit 3, when no metal object exists underwater or underwater, the phases of the homodromous branch signal 701 and the orthogonal branch signal 702 of the local carrier are adjusted to make the local carrier approximately orthogonal to the signals transmitted by the first AD module 603 and the second AD module 604, and a ratio 705 of a first multiplied integral value 703 and a second multiplied value 704 is obtained;

if there is a metal object underwater or on the water bottom in the detection range of the receiving antenna unit 2 at the a end, the ratio 705 of the first multiplied integral value 703 to the second multiplied integral value 704 becomes smaller, and a valley appears; if there is a metal object underwater or on the water bottom in the detection range of the receiving antenna unit 2 at the B-end, the ratio 705 of the first multiplied integral value 703 to the second multiplied integral value 704 becomes large and a peak appears.

The present invention may further comprise:

the antenna unit is arranged on the antenna bracket 105; the antenna bracket 105 comprises a vertical rod and a horizontal cross-shaped bracket; the horizontal cross-shaped bracket consists of a first horizontal rod piece and a second horizontal rod piece which are vertically crossed with the point O; the lower end of the vertical rod piece is connected to a point O of the cross-shaped support; the transmitting antenna unit 1, the A-end receiving antenna unit 2 and the B-end receiving antenna unit 3 are all electric dipole antennas, two conductors of the transmitting antenna unit 1 are respectively arranged on two sides of a point O on a first horizontal rod, two conductors of the A-end receiving antenna unit 2 are arranged on one side of the point O on a second horizontal rod, two conductors of the B-end receiving antenna unit 3 are arranged on the other side of the point O on the second horizontal rod, and all the conductors are arranged around the point O in a central symmetry mode.

The conductors of the transmitting antenna unit 1, the A-end receiving antenna unit 2 and the B-end receiving antenna unit 3 adopt carbon rods or silver chloride metal rods, the surfaces of the conductors are smooth and have no burrs, the upper ends of the conductors are tightly wrapped by copper foils connected with wires to be used as antenna feeders, the connection points of the wires are insulated and sealed by polyester materials, and the upper ends of the conductors are sealed by adhesive tapes.

The invention also aims to provide an underwater current field detection method based on double-path orthogonal detection.

The purpose of the invention is realized by the following technical scheme: the method comprises the following steps:

step 1: mounting the antenna unit on the antenna mount 105; the antenna bracket 105 comprises a vertical rod and a horizontal cross-shaped bracket; the horizontal cross-shaped bracket consists of a first horizontal rod piece and a second horizontal rod piece which are vertically crossed with the point O; the lower end of the vertical rod piece is connected to a point O of the cross-shaped support; the transmitting antenna unit 1, the A-end receiving antenna unit 2 and the B-end receiving antenna unit 3 are all electric dipole antennas, two conductors of the transmitting antenna unit 1 are respectively arranged on two sides of a point O on a first horizontal rod, two conductors of the A-end receiving antenna unit 2 are arranged on one side of the point O on a second horizontal rod, two conductors of the B-end receiving antenna unit 3 are arranged on the other side of the point O on the second horizontal rod, and all the conductors are arranged around the point O in a central symmetry manner;

step 2: putting the antenna bracket 105 provided with the antenna unit under water, wherein the horizontal cross-shaped bracket part is parallel to the detection water bottom; the antenna bracket 105 is moved in parallel to detect, and the detection direction is the advancing direction of the A-end receiving antenna unit 2;

and step 3: when it is detected that a valley occurs in a ratio 705 between the first multiplied integral value 703 and the second multiplied integral value 704 becomes smaller, it is determined that metal is present underwater or underwater within the detection range of the a-terminal receiving antenna unit 2;

and 4, step 4: as the antenna mount 105 with the antenna unit mounted thereon continues to move forward, the ratio 705 of the first multiplied integral value 703 to the second multiplied integral value 704 gradually increases until a peak appears, verifying the metal object detected in step 3.

The invention has the beneficial effects that:

the invention carries out detection and verification on underwater metal objects through 2 times of wave trough and wave crest state changes, greatly improves the sensitivity and reliability of underwater or underwater metal object detection, judges by using more useful information of detection signals, has higher sensitivity than the traditional judgment method only depending on amplitude, overcomes the problem of poor detection effect caused by detection threshold changes due to environmental changes, and avoids the difficulty of setting the detection threshold. The invention solves the problems of poor detection effect and high false alarm caused by too small detection voltage change or detection threshold change caused by environment change in the existing underwater current field detection method, and improves the effectiveness and reliability through two-way orthogonal detection.

Drawings

Fig. 1 is a structural diagram of an underwater current field detection system based on two-way orthogonal detection in the invention.

FIG. 2 is a schematic diagram of two-way quadrature detection of output trough and peak states (in the presence of metal).

Detailed Description

The invention is further described below with reference to the accompanying drawings.

The invention provides a system and a method for detecting an underwater current field based on two-way orthogonal detection, which are used for detecting and verifying underwater metal objects through 2 times of state changes of wave troughs and wave crests, greatly improving the sensitivity and reliability of underwater or underwater metal object detection, judging by using more useful information of detection signals, having higher sensitivity than the traditional method which only depends on amplitude judgment, overcoming the problem of poor detection effect caused by detection threshold change due to environmental change, avoiding the difficulty of setting a detection threshold, and being an underwater current field detection method with wide application prospect; the underwater detection system overcomes the defects of the traditional underwater detection technology to a certain extent, reduces the dependence on the surrounding environment, has a simple structure, and is very suitable for being used in dark and turbid water areas on the coastal areas. The invention relates to an underwater current field detection method applied to detecting underwater metal objects and insulators, which solves the problems of poor detection effect and high false alarm caused by too small detection voltage change or detection threshold change caused by environmental change in the existing underwater current field detection method, and improves the effectiveness and the reliability through two-way orthogonal detection.

An underwater current field detection system based on two-way orthogonal detection comprises an antenna unit, a transmitting unit 4, a receiving unit 5, a digital control unit 6 and an upper computer two-way orthogonal detector judgment unit 7; the antenna unit comprises a transmitting antenna unit 1, an A-end receiving antenna unit 2 and a B-end receiving antenna unit 3; the digital control unit 6 comprises a controller 601, a DA module 602, a first AD module 603, and a second AD module 604; the transmitting unit 4 comprises a power amplifier 401 and an impedance matching network 402; the receiving unit comprises a first balun frequency-selecting loop 501 and a second balun frequency-selecting loop 502; the upper computer two-way orthogonal detector decision unit 7 comprises a first chaotic detector 703 and a second chaotic detector 704;

the antenna unit is arranged on the antenna bracket 105; the antenna bracket 105 comprises a vertical rod and a horizontal cross-shaped bracket; the horizontal cross-shaped bracket consists of a first horizontal rod piece and a second horizontal rod piece which are vertically crossed with the point O; the lower end of the vertical rod piece is connected to a point O of the cross-shaped support; the transmitting antenna unit 1, the A-end receiving antenna unit 2 and the B-end receiving antenna unit 3 are all electric dipole antennas, two conductors of the transmitting antenna unit 1 are respectively arranged on two sides of a point O on a first horizontal rod, two conductors of the A-end receiving antenna unit 2 are arranged on one side of the point O on a second horizontal rod, two conductors of the B-end receiving antenna unit 3 are arranged on the other side of the point O on the second horizontal rod, and all the conductors are arranged around the point O in a central symmetry mode.

The controller 601 generates a sine wave digital signal, and the sine wave digital signal is generated by the DA module 602 and transmitted to the power amplifier 401 of the transmitting unit 4; the power amplifier 401 amplifies the power of the sine wave signal and transmits the amplified sine wave signal to the transmitting antenna unit 1 through the impedance matching network 402; the transmitting antenna unit 1 radiates the received power signal into water and transmits the weak reflected signal received by induction to the A-end receiving antenna unit 2 and the B-end receiving antenna unit 3; the terminal a receiving antenna unit 2 transmits the received and sensed signal of the underwater weak reflection electric field to a first balun frequency-selective loop 501 of the receiving unit 5, and the terminal B receiving antenna unit 3 transmits the received and sensed signal of the underwater weak reflection electric field to a second balun frequency-selective loop 502 of the receiving unit 5; the first balun frequency-selecting loop 501 converts the received differential electrical signal into a single-ended voltage signal, and transmits the single-ended voltage signal to the first AD module 603 of the digital control unit 6 after being processed by a low-noise amplifier, a band-pass filter and a secondary amplifier in sequence; the second balun frequency-selecting loop 502 converts the received differential electrical signal into a single-ended voltage signal, and transmits the single-ended voltage signal to the second AD module 604 of the digital control unit 6 after being processed by the low-noise amplifier, the band-pass filter and the secondary amplifier in sequence; the first AD module 603 and the second AD module 604 respectively perform AD conversion on the received signals and transmit the converted signals to the decision unit 7 of the two-way orthogonal detector of the upper computer through the man-machine interaction interface 605;

after receiving the signals transmitted by the first AD module 603 and the second AD module 604, the upper computer two-way orthogonal detector decision unit 7 performs multiplication and integration on the signal transmitted by the first AD module 603 and the same-direction branch signal 701 of the local carrier to obtain a first multiplication integral value 703; multiplying and integrating the signal transmitted by the second AD module 604 with the orthogonal branch signal 702 of the local carrier to obtain a second product score 704; in the detection range of the end-a receiving antenna unit 2 and the end-B receiving antenna unit 3, when no metal object exists underwater or underwater, the phases of the homodromous branch signal 701 and the orthogonal branch signal 702 of the local carrier are adjusted to make the local carrier approximately orthogonal to the signals transmitted by the first AD module 603 and the second AD module 604, and a ratio 705 of a first multiplied integral value 703 and a second multiplied value 704 is obtained;

if there is a metal object underwater or on the water bottom in the detection range of the receiving antenna unit 2 at the a end, the ratio 705 of the first multiplied integral value 703 to the second multiplied integral value 704 becomes smaller, and a valley appears; if there is a metal object underwater or on the water bottom in the detection range of the receiving antenna unit 2 at the B-end, the ratio 705 of the first multiplied integral value 703 to the second multiplied integral value 704 becomes large and a peak appears.

The invention solves the problems that the traditional underwater electric field detection is easily influenced by the surrounding environment and has low sensitivity and poor reliability, and solves the problem that the traditional underwater electric field detection needs self-adaptive adjustment when judging by using a hard judgment threshold. Through the change of trough crest state 2 times, carry out the detection and the verification of metal object under water, improve sensitivity and the reliability of detecting under water or submarine metal object greatly, use more useful information of detecting signal to judge, it is higher than traditional dependence amplitude judgement sensitivity, overcome moreover because the environmental change arouses that the detection threshold changes and leads to the relatively poor problem of detection effect, avoided setting up the difficulty that detects the threshold. The complexity of the method is the same as that of the conventional underwater electric field detection, but the complexity of the upper computer judgment algorithm is improved, the calculation amount is larger, but the algorithm can be realized by adopting a computer with higher main frequency, the complexity is also acceptable, the real-time monitoring can be realized, and the detection efficiency is improved.

Example 1:

with reference to fig. 1, an underwater current field detection method based on two-way orthogonal detection, the system includes a transmitting antenna unit 1, an a-end receiving antenna unit 2, a B-end receiving antenna unit 3, a transmitting unit 4, a receiving unit 5, a digital control unit 6 and an upper computer two-way orthogonal detector decision algorithm 7;

the transmitting antenna unit 1 is used for modulating a sine wave signal generated by the DA module 602 of the digital control unit 6 into a power signal through the transmitting unit 4 to be radiated into water, and transmitting a weak reflection signal received by induction to the a-end receiving antenna unit 2 and the B-end receiving antenna unit 3; the transmitting antenna unit 1 is composed of a transmitting wire and an antenna bracket 105, and is an electric dipole antenna; the transmitting antenna of the transmitting antenna unit 1 is an electric dipole antenna consisting of 2 carbon rods or silver chloride metal rods (101 and 102); the size of the transmitting antenna unit is determined according to the size of transmitting current, the transmitting antenna unit is smaller than 1 ampere, generally has the diameter of about 10mm and the length of 50mm, and has smooth and burr-free surface; one end of the transmitting antenna is tightly wrapped by copper foil firmly welded with a wire to be used as an antenna feeder, a welding spot is flatly insulated and sealed by using a polyester material, the end is sealed by using an adhesive tape, the wire is reliably connected to the transmitting unit 4, and the underwater wire connecting point is insulated and sealed by using the polyester material to manufacture one electric dipole transmitting antenna 101; the other electric dipole antenna rod 102 is also manufactured in the same manner; the A-end receiving antenna unit 2 also comprises an electric dipole antenna consisting of 2 carbon rods (201 and 202), the manufacturing method is the same as that of the electric dipole transmitting antenna 101, and the A-end receiving antenna unit is reliably connected to the receiving unit 5 through a lead; the B-end receiving antenna unit 3 also comprises an electric dipole antenna consisting of 2 carbon rods (301 and 302), is manufactured by the same method as the electric dipole transmitting antenna 101, and is reliably connected to the receiving unit 5 through a lead; the transmitting antennas 101 and 102 of the transmitting antenna unit 1 are arranged on a straight line, are symmetrical about a central point and are 150cm away from the central point, the A-end receiving antenna unit 2 and the B-end receiving antenna unit 3 are respectively placed on the perpendicular bisector of the connecting line of the transmitting antennas and are symmetrically placed on two sides of the central point, the distances from the central point are the same, are 100cm away from the central point, the length of each antenna is 50cm, and the detection advancing direction is the advancing direction of the A-end receiving antenna unit;

the controller 601 in the digital control unit 6 generates a sine wave digital signal with the frequency of 250Hz by a table look-up method, and the power amplification is carried out on the sine wave signal generated by the DA module 602 through the power amplification circuit 401 of the signal transmitting unit 4 to obtain a high-power electric field signal of about 5W; sending the high-power electric field signal to an impedance matching network 402 to be connected with the transmitting antennas 101 and 102, realizing impedance matching between the power amplifier and the transmitting antennas through the impedance matching network, and meeting the optimal output impedance of the power amplifier through the turn ratio of the impedance matching network;

the signal receiving unit 5 sends 2 paths of weak electric signals in water sensed by the A-end receiving antenna unit 2 and the B-end receiving antenna unit 3 to 2 sets of balun frequency-selective loops 501 and 502 respectively to convert differential electric signals into single-end voltage signals, then outputs the single-end voltage signals to 2 sets of low-noise amplifiers 503 and 504 respectively for amplification, filters out-of-band noise through 2 sets of band-pass filters 505 and 506 respectively, inputs the single-end voltage signals into 2 sets of secondary amplifiers 507 and 508 respectively to become analog receiving signals with proper range, and sends the analog receiving signals to the digital control unit 6 for 2-path sampling;

the digital control unit 6 performs 100-time sampling on the signals received by the 2 paths through the AD modules 603 and 604, and the signals are transmitted to the upper computer two-path orthogonal detector decision algorithm 7 for decision at a high speed through the man-machine interaction interface 605 after AD conversion;

the balun frequency selection loops 501 and 502 are used for suppressing a common-mode electrical signal, converting a differential electrical signal sensed by the a-end receiving antenna unit and the B-end receiving antenna unit into a single-end voltage signal, filtering useless noise and interference outside a single-end voltage signal frequency band, and transmitting the signal to the low-noise amplifiers 503 and 504;

the low-noise amplifiers 503 and 504 are configured to receive the weak electrical signals input by the balun frequency selection loops 501 and 502, and perform low-noise appropriate amplification on the received weak electrical signals, so that the intensity of the received electrical signals reaches the range of the processing level of the band-pass filters 505 and 506, and send the amplified electrical signals to the band-pass filters 505 and 506;

the center frequency of the band-pass filters 505 and 506 is a sine wave signal frequency of 250Hz, the received electric signals are subjected to high-Q filtering, the Q value can reach 60-80, and the filtered signals are output to the rear-end secondary amplifiers 507 and 508;

the second-stage amplifiers 507 and 508 control the level of the filtered signal within the conversion range of the AD module, the level is controlled to about 1v, and the signal is input to 2 paths of AD modules 603 and 604 of the digital control unit 6 to be sampled by 100 times respectively; the 2-path digital signals after AD conversion are transmitted to an upper computer two-path orthogonal detector decision algorithm 7 for decision at a high speed through a man-machine interaction interface 605, a high-speed serial port can be generally selected as the man-machine interaction interface 605, and the transmission rate is 115200bps as high as possible so as to be capable of processing in time;

after receiving 2 paths of digital receiving signals, an upper computer two-path orthogonal detector decision algorithm 7 multiplies and integrates the 2 paths of digital signals and local co-frequency carrier homodromous and orthogonal signals respectively, wherein a path of signals and a co-frequency branch signal 701 are multiplied and integrated 702, a path of signals and an orthogonal branch 703 are multiplied and integrated 704, finally, a ratio 705 of the co-frequency branch integration to the orthogonal branch integration is calculated, local carrier phases 701 and 703 are continuously adjusted, so that the local carrier and the receiving signals are approximately orthogonal, the ratio is greater than 0.8 time of the ratio 705 when no metal object exists in an underwater or underwater detection range, the ratio 705 can be changed in a self-adaptive mode along with the change of the environment when no metal object exists in the underwater or underwater detection range, and the problem of poor detection effect caused by the change of detection threshold due to the change of the environment is solved; since the 2-way received signal is approximately orthogonal to the local carrier, the ratio 705 is larger for the tangent 705 of the approximate orthogonal angle; if metal objects exist in the underwater or water bottom detection range near the A-end receiving antenna, the A-end antenna receives and senses weak reflected electric field signals in water to jump, the amplitude and the phase of the signals received by the A-path are reduced, the integral value 702 of the homodromous branch is reduced, the tangent value is reduced 705, a trough is formed, metal is detected, and the tangent value 705 is greatly changed due to the fact that the system is approximately orthogonal and the very weak angle jump of the reflected electric field signals is generated, so that the trough is observed; then, as the receiving antenna continues to move forward, the B-end receiving antenna moves to a position near a metal object, and the A-end antenna is far away from the metal object, so that the signal amplitude is restored to the original degree, the B-end antenna receives and senses the weak reflected electric field signal in water and jumps, the amplitude of the signal received by the B-path is reduced, the weak jump is generated on the phase, the tangent value 705 is increased, a peak is generated, and the detection of the metal object is verified. The detection and verification of underwater metal objects are completed through the change of the adjacent wave troughs and wave crests, and the sensitivity and reliability of underwater metal object detection are greatly improved.

The 2-path receiving signals input into the two-path orthogonal detector firstly need to continuously adjust the local carrier phases 701 and 703 through the controller, so that the local carrier and the receiving signals are approximately orthogonal, at the moment, the ratio is a threshold when no metal object exists in an underwater or underwater detection range, only the ratio is approximately orthogonal, generally, the tangent value 705 is preferably adjusted to be larger than 10000, at the moment, the tangent value 705 is larger, and the change of the tangent value is easy to observe; and the tangent value is adaptively changed along with the change of the environment, so that the problem of poor detection effect caused by the change of a detection threshold is solved, and the anti-interference capability is improved.

The transmitting antenna unit 1, the A-end receiving antenna unit 2 and the B-end receiving antenna unit 3 are placed in a plane and are parallel to the detection water bottom, and the detection is carried out by moving in parallel, wherein the detection direction is the advancing direction of the A-end receiving antenna unit.

The detection process comprises detection judgment and verification, wherein the tangent value 705 is reduced, and a trough appears, so that the detection judgment process is realized; the tangent value 705 is increased, and a peak appears, which is a detection verification process; through two processes of detection judgment and verification, the detection effectiveness and reliability are improved, real-time monitoring can be achieved, and the detection efficiency is improved.

The underwater current field detection method based on two-way orthogonal detection is shown in figure 1, and an electric field power signal output by a transmitting unit is radiated into water and an underwater stratum by a transmitting antenna, so that effective radiation of sine wave signals is realized to form a detection space; the 2-path receiving antenna sends the sensed weak reflected electric field signal in water to a low-noise amplifier for amplification at the same time, then the out-of-band noise is filtered by a band-pass filter to improve the receiving effect, then a secondary amplifier is carried out for amplification to a proper range waveform, then sampling is carried out by AD (analog-to-digital) with the sampling rate being 100 times of the sine wave frequency, the 2-path digital signal after sampling is transmitted to an upper computer at high speed through a serial port for double-path orthogonal detection algorithm judgment, the 2-path digital signal and local co-frequency carrier homodromous and orthogonal signals are respectively multiplied and integrated, wherein the signal of the A-path and the homodromous branch are multiplied and integrated, the signal of the B-path and the orthogonal branch are multiplied and integrated, finally the ratio of the homodromous branch integral to the orthogonal branch integral is calculated, the local carrier phase is continuously adjusted to enable the local carrier and the received signal to be approximately orthogonal, and at the ratio is more than 0.8 times of the ratio when no metal object exists in the underwater or underwater detection range, the ratio is a threshold when no metal object exists in an underwater or water bottom detection range, can change in a self-adaptive manner along with the change of the environment, and solves the problem of poor detection effect caused by the change of the detection threshold due to the change of the environment; because the 2 paths of received signals are approximately orthogonal to the local carrier, the ratio is the tangent value of the approximate orthogonal angle and is larger; if metal objects exist in the underwater or underwater detection range near the A-end receiving antenna, the A-end antenna receives and senses weak reflected electric field signals in water to jump, the amplitude and the phase of the signals received by the A-path are reduced, the integral value of the homodromous branch is reduced, the tangent value is reduced, a trough is formed, the metal is detected, and the tangent value is greatly changed due to the very weak angle jump of the reflected electric field signals because the system is in approximate orthogonality, so that the trough is observed; then, as the receiving antenna continues to move forward, the B-end receiving antenna moves to a position near a metal object, and the A-end antenna is far away from the metal object, so that the signal amplitude is restored to the original degree, the B-end antenna receives and senses the weak reflected electric field signal in water and jumps, the amplitude of the signal received by the B-path is reduced, the weak jump is generated on the phase, the tangent value is increased, a peak is generated, and the detection of the metal object is verified. The underwater current field detection method based on the two-way orthogonal detection completes the detection and verification of underwater metal objects by the occurrence of the adjacent wave trough and wave crest changes, greatly improves the sensitivity and reliability of underwater or underwater metal object detection, overcomes the problem of poor detection effect caused by the change of a detection threshold due to the change of the environment, avoids the difficulty of setting the detection threshold, can realize real-time monitoring, improves the detection efficiency, and is an underwater current field detection method with wide application prospect.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.