A cable-type low-frequency electromagnetic field radiator and detection method

Abstract

The present invention discloses a cable-type low-frequency electromagnetic field radiator and a detection method, comprising a cable (1), two current-carrying conductors in the cable (1), a phase shifter (2) connected to the end of the cable (1), and the phase shifter (2) is driven by an external driving circuit (3) to change the phase of the current in the two current-carrying conductors in the cable. The invention provides a new method for the radiation of low-frequency electromagnetic fields, improves the stability and versatility of its design, and has significant military and economic benefits.

Description

Technical Field

[0001] The present invention belongs to the technical field of low-frequency electromagnetic field radiation, and in particular relates to a cable-type low-frequency electromagnetic field radiator and a detection method. Background Art

[0002] Low-frequency electromagnetic fields (below 300kHz) are mostly used to detect substances in conductive media such as underwater or underground. Currently, low-frequency electromagnetic field radiation is generally produced in two ways:

[0003] (1) Coil type: The structure of the coil type low frequency electromagnetic field radiator is as shown in the attached manual Figure 5 As shown, most of them are solenoid radiators with magnetic cores. The magnetic cores are mostly made of high-density materials such as silicon steel sheets. The radiation field strength is related to the core size, the number of coil turns and the current intensity in the coil. Therefore, this type of radiator is usually large in size and weight, which limits its use environment. In addition, the solenoid with a magnetic core has a large inductance value, which causes the coil radiator to have frequency selectivity and a narrow operating frequency band.

[0004] (2) Electrode type: The structure of the electrode type low-frequency electromagnetic field radiator is as shown in the attached manual Figure 6 As shown, its volume and weight are small. When in use, the two electrodes need to be placed in a conductive medium. An AC signal is applied to the electrodes through an external driving circuit. The electrodes will form a current loop through the conductive medium and radiate electromagnetic waves to the outside. The disadvantage is that part of the radiation loop is composed of the external medium, and the radiation performance and power consumption are greatly affected by the conductivity of the medium, and the versatility is poor. It is difficult to test in the air, which increases the complexity of design and testing.

[0005] The structure of the dual-electrode low-frequency electromagnetic field radiator towed by an underwater vehicle is shown in the attached figure. The current loop that generates the radiation field is composed of the tow cable current and the shunt current. The impedance of the entire current loop is affected by the conductivity of the water body, especially the conductivity of fresh water and sea water, which is quite different. The power consumption of the external power supply circuit is also quite different, and they cannot be universal. In addition, when used in water, there is also the risk of electrochemical corrosion to the underwater vehicle.

[0006] In summary, the current technology has many problems. Due to its large size and weight, the use environment of coil-type radiators is limited. In particular, it cannot be used for towing detection of underwater vehicles. Electrode-type radiators are affected by the conductivity of the external medium and have poor versatility. Summary of the invention

[0007] In order to solve the problems and shortcomings of the above-mentioned prior art, the present invention provides a cable-type low-frequency electromagnetic field radiator and a detection method, which take into account the versatility of the low-frequency electromagnetic field radiator in media with different conductivity and the volume and weight of the radiator, realize the functional requirements of on-land testing of the radiator, reduce the difficulty of product design, and improve the stability of product design.

[0008] The following design structures and solutions are specifically adopted:

[0009] A cable-type low-frequency electromagnetic field radiator comprises a cable (1), two current-carrying conductors are arranged in the cable (1), the ends of the cable (1) are connected to a phase shifter (2), and the phase shifter (2) is driven by an external driving circuit (3).

[0010] Preferably, the two current-carrying conductors in the cable (1) include a current-carrying conductor (11) and a current-carrying conductor (12).

[0011] Preferably, the length of the cable (1) is determined according to the radiation range and the frequency of the radiated low-frequency electromagnetic waves, and is from tens of meters to hundreds of meters.

[0012] Preferably, the current-carrying wire (11) and the current-carrying wire (12) are connected to the external driving circuit (3) and the phase shifter (2) at the end of the cable (1) to form a complete loop.

[0013] Preferably, the phase shifter (2) changes the phase of the current in the current-carrying wire (11) and the current in the current-carrying wire (12).

[0014] Preferably, the driving circuit (3) comprises a signal generator (31) and a power amplifier (32).

[0015] A cable-type low-frequency electromagnetic field radiator and a detection method, the method comprising the following steps:

[0016] Step S1: placing the external driving circuit (3) outside the detection range, placing the cable (1) and the phase shifter (2) in the detection medium, and during underwater detection, placing the external driving circuit (3) on a ship or an underwater vehicle, and releasing the cable (1) and the phase shifter (2) in the water in a dragging manner;

[0017] Step S2: The signal generator (31) generates a small signal of a corresponding frequency. The small signal increases the current intensity after passing through the power amplifier (32). In a transient state, the current flows to the power amplifier (32), the current-carrying wire (11), the phase shifter (2), the current-carrying wire (12), and the power amplifier (32). Since the length of the cable (1) is much smaller than the wavelength of the current of the corresponding frequency transmitted in the conductor, the phase change of the current passing through the current-carrying wire (11) and the current-carrying wire (12) can be ignored.

[0018] Step S3: When the current flows through the phase shifter (2), the current phase changes, so that the current phases in the current-carrying conductor (11) and the current-carrying conductor (12) do not satisfy the inverse relationship. When the phase shifter (2) produces a 90° phase shift, the radiation field generated by the current 1 in the current-carrying conductor (11) and the current 2 in the current-carrying conductor (12) will not cancel each other out, and the cable (1) as a whole can radiate electromagnetic waves to the outside, generating electromagnetic waves radiated radially with the cable (1) as the axis.

[0019] The working principle of the present invention is as follows:

[0020] When an alternating current signal passes through a purely resistive load, the phase of the current changes continuously, that is, no phase shift occurs. In the current-carrying conductor (11) and the current-carrying conductor (12), the wavelength of the low-frequency electromagnetic wave is much greater than the length of the cable (1). When the end load is a purely resistive load, the phase of the current in the current-carrying conductor changes continuously, but due to the relationship between the spatial directions of the current, the current directions of the current-carrying conductor (11) and the current-carrying conductor (12) are opposite. When observed from the outside of the cable, the currents in the current-carrying conductor (11) and the current-carrying conductor (12) are in an anti-phase relationship, and the spatial positions of the current-carrying conductor (11) and the current-carrying conductor (12) coincide, and the generated radiation fields cancel each other out. When the end load is a phase shifter (2), the alternating current signal will be phase shifted after passing through the phase shifter (2), so that the current phases in the current-carrying conductor (11) and the current-carrying conductor (12) do not satisfy the anti-phase relationship, and the cable (1) as a whole can radiate electromagnetic waves to the outside, generating electromagnetic waves radiated radially with the cable (1) as the axis.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: the loop formed by the current-carrying wire connecting the external driving circuit and the phase shifter in the present invention is completely closed and can be used in media with different conductivity, thus solving the problem of universality in application in media with different conductivity; the radiator has a cable-like appearance, is small in size and weight, has no exposed electrodes in the entire structure, thus eliminating the hidden danger of electrochemical corrosion, and is not affected by external media, thus reducing the design requirements for the driving circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a structural schematic diagram of the present invention.

[0023] Figure 2 It is the internal structure diagram of the present invention.

[0024] Figure 3 is the current phase without phase shift at the end.

[0025] Figure 4 The terminal phase is shifted by 90°.

[0026] Figure 5 Schematic diagram of the structure of a coil-type low-frequency electromagnetic field radiator in the prior art

[0027] Figure 6 Schematic diagram of the structure of the electrode-type low-frequency electromagnetic field radiator in the prior art

[0028] Figure 7 Schematic diagram of the structure of a dual-electrode low-frequency electromagnetic field radiator towed by an underwater vehicle

[0029] Reference numerals: 1—cable; 11—current-carrying wire; 12—current-carrying wire; 2—phase shifter; 3—external driving circuit; 31—signal generator; 32—power amplifier. DETAILED DESCRIPTION

[0030] The specific implementation of the present invention will be described in more detail below with reference to the accompanying drawings and specific embodiments.

[0031] As shown in the accompanying drawings of the specification, a cable-type low-frequency electromagnetic field radiator comprises a cable (1), two current-carrying conductors are arranged in the cable (1), and a phase shifter (2) is arranged at the end of the cable (1).

[0032] Furthermore, the two current-carrying conductors in the cable (1) include a current-carrying conductor (11) and a current-carrying conductor (12), wherein the current generated by the current-carrying conductor (11) is current 1, and the current generated by the current-carrying conductor (12) is current 2.

[0033] Furthermore, the current-carrying wire (11) and the current-carrying wire (12) are connected to the external driving circuit (3) and the phase shifter (2) to form a complete current loop.

[0034] Furthermore, the current flowing through the phase shifter (2) will have a phase shift.

[0035] Furthermore, the driving circuit (3) comprises a signal generator (31) and a power amplifier (32).

[0036] Furthermore, the signal generator (31) generates a small signal, which is amplified into a large signal with a certain current intensity by the power amplifier (32).

[0037] Furthermore, the radiation field is generated by the current 1 in the current-carrying wire (11) and the current 2 in the current-carrying wire (12).

[0038] Furthermore, the length of the cable (1) is determined by the radiation range; the longer the length, the larger the radiation range.

[0039] Furthermore, the maximum length of the cable (1) is determined by the frequency of the radiated low-frequency electromagnetic waves, and is between tens of meters and hundreds of meters. The lower the frequency of the radiated electromagnetic waves, the longer the maximum length of the cable. The length of the cable (1) is no greater than one tenth of the wavelength of the electromagnetic waves of the corresponding frequency transmitted in the conductor.

[0040] Furthermore, the phase shifter (2) can be a passive device or an active device. When the phase shifter (2) is an active device, it also requires external power supply, and two DC conductors need to be added to the cable for powering the active phase shifter.

[0041] The specific implementation is as follows:

[0042] The external driving circuit (3) is placed outside the detection range, and the cable (1) and the end phase shifter (2) are placed in the detection medium. During underwater detection, the external driving circuit (3) is placed on a ship or in an underwater vehicle, and the cable (1) and the end phase shifter (2) are released in the water in the form of a towing cable.

[0043] According to the requirement of the radiation signal frequency, the signal generator (31) generates a small signal of the corresponding frequency; after the small signal passes through the power amplifier (32), the current intensity is increased; the external drive circuit (3) and the phase shifter (2) are connected through the current-carrying conductor (11) and the current-carrying conductor (12) in the cable (1) to form a complete current loop.

[0044] In a transient state, the current flows in the following directions: power amplifier (32), current-carrying conductor (11), phase shifter (2), current-carrying conductor (12), power amplifier (32). Since the length of the cable (1) is much smaller than the wavelength of the current of the corresponding frequency transmitted in the conductor, the phase change of the current passing through the current-carrying conductor (11) and the current-carrying conductor (12) can be ignored. If the position of the phase shifter (2) is replaced with a pure resistive load that does not cause phase change, the change in the spatial position of the current-carrying conductor causes the current direction in the current-carrying conductor to change. The phase relationship between the current-carrying conductor (11) and the current-carrying conductor (12) observed from the outside is shown in the attached figure. Figure 3 As shown, the current 1 in the current-carrying wire (11) and the current 2 in the current-carrying wire (12) have opposite phases and equal amplitudes. At the same time, since the spatial positions of the current-carrying wire (11) and the current-carrying wire (12) completely overlap, the radiation field generated by the current 1 in the current-carrying wire (11) and the current 2 in the current-carrying wire (12) completely cancel each other out, and no electromagnetic field of the corresponding frequency is generated in space.

[0045] When the current flows through the phase shifter (2), the current phase changes, so that the current phases in the current-carrying wire (11) and the current-carrying wire (12) do not satisfy the anti-phase relationship. When the phase shifter produces a 90° phase shift, the phases of the current 1 in the current-carrying wire (11) and the current 2 in the current-carrying wire (12) are as shown in the attached figure. Figure 4 As shown, the radiation field generated by the current 1 in the current-carrying conductor (11) and the current 2 in the current-carrying conductor (12) will not cancel each other out, and the cable (1) as a whole can radiate electromagnetic waves to the outside, generating electromagnetic waves radiated radially with the cable (1) as the axis.

[0046] The phase shifter (2) can be an active device or a passive device. When the phase shifter is a passive device, there are only the two current-carrying conductors (11) and (12) in the cable. When the phase shifter is an active device, two phase shifter power supply lines need to be added to the cable to transmit direct current without affecting the radiation of alternating electromagnetic fields.

[0047] The protection scope of the present invention is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only for helping to explain and illustrate the present invention, rather than limiting the protection scope of the present invention. As long as the design is the same as the design of the present invention or as long as it is an equivalent replacement, it falls within the scope of protection required by the present invention.

Claims

1. A cable-type low-frequency electromagnetic field radiator, comprising a cable (1), characterized in that: There are two current-carrying conductors in the cable (1), the ends of the cable (1) are connected to a phase shifter (2), and the phase shifter (2) is driven by an external driving circuit (3); The two current-carrying conductors in the cable (1) include a first current-carrying conductor (11) and a second current-carrying conductor (12); The first current-carrying wire (11) and the second current-carrying wire (12) are connected to the external driving circuit (3) and the phase shifter (2) at the end of the cable (1) to form a complete loop; The first current-carrying wire (11) and the second current-carrying wire (12) overlap in spatial position; When the phase shifter (2) generates a 90° phase shift, the phases of the current 1 in the first current-carrying conductor (11) and the current 2 in the second current-carrying conductor (12) do not satisfy an anti-phase relationship, the generated radiation fields will not be offset, and the cable (1) as a whole can radiate electromagnetic waves to the outside, generating electromagnetic waves radiated radially with the cable (1) as the axis.

2. A cable-type low-frequency electromagnetic field radiator according to claim 1, characterized in that: The length of the cable (1) is determined according to the radiation range and the frequency of the radiated low-frequency electromagnetic waves, and is from tens of meters to hundreds of meters.

3. A cable-type low-frequency electromagnetic field radiator according to claim 1, characterized in that: The driving circuit (3) comprises a signal generator (31) and a power amplifier (32).

4. A detection method based on the cable-type low-frequency electromagnetic field radiator according to any one of claims 1 to 3, characterized in that: The method comprises the following steps: Step S1: placing the external driving circuit (3) outside the detection range, placing the cable (1) and the phase shifter (2) in the detection medium, and during underwater detection, placing the external driving circuit (3) on a ship or an underwater vehicle, and releasing the cable (1) and the phase shifter (2) in the water in a dragging manner; Step S2: the signal generator (31) generates a small signal having a corresponding frequency, and the small signal increases the current intensity after passing through the power amplifier (32). In a transient state, the current flows to the power amplifier (32), the first current-carrying conductor (11), the phase shifter (2), the second current-carrying conductor (12), and the power amplifier (32). Since the length of the cable (1) is much smaller than the wavelength of the current of the corresponding frequency transmitted in the conductor, the phase change of the current passing through the first current-carrying conductor (11) and the second current-carrying conductor (12) can be ignored. Step S3: When the current flows through the phase shifter (2), the current phase changes, so that the current phases in the first current-carrying conductor (11) and the second current-carrying conductor (12) do not satisfy the reverse relationship. When the phase shifter (2) generates a 90° phase shift, the radiation field generated by the current 1 in the first current-carrying conductor (11) and the current 2 in the second current-carrying conductor (12) will not cancel each other out, and the cable (1) as a whole can radiate electromagnetic waves to the outside, generating electromagnetic waves radiated radially with the cable (1) as the axis.

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