Extremely-low-frequency magnetic field communication receiver based on atomic magnetometer

Abstract

The invention discloses an extremely-low-frequency magnetic field communication receiver based on an atomic magnetometer in the technical field of wireless communication. A core sensor of the extremely-low-frequency magnetic field communication receiver is a scalar atom magnetometer based on a free induction attenuation working principle and a pulsed light pumping working mode, and comprises a gauge outfit and a controller electrically connected with the gauge outfit; the meter head comprises a VCSEL laser, a polarized magnetic field coil, a magnetic field gradient coil, an atomic gas chamber, a lambda / 4 wave plate, a photodiode and a heat preservation box; and the controller comprises a header driving circuit and an FPGA (Field Programmable Gate Array)-based signal processor for operating an automatic working algorithm to control the driving circuit. The receiver provided by the invention has higher detection sensitivity to the extremely low frequency magnetic field under the condition of the same probe volume, has the advantages of miniaturization and light weight, is suitable for a dynamic carrier platform and is easy to form a magnetic field gradiometer or array, the sensitivity of the receiver is improved, the communication distance is increased, and the covert communication capability is improved.

Description

Technical Field

[0001] The present invention relates to the field of wireless communication technologies, and in particular, to an extremely low frequency magnetic field communication receiver based on an atomic magnetometer. Background Art

[0002] High-frequency electromagnetic wave signals have large propagation losses, short propagation distances, and poor penetration capabilities in media such as metals, solid materials (concrete, rock, soil, etc.), and water. Since in a given medium, the penetration depth of electromagnetic waves is inversely proportional to the square root of the electromagnetic wave frequency. For example, the penetration depth of an electromagnetic wave with a frequency of 1 kHz is three orders of magnitude larger than that with a frequency of 1 GHz. Therefore, extremely low frequency (below 3 - 30 Hz) electromagnetic waves have small propagation losses, strong seawater penetration capabilities, and long propagation distances. However, a major drawback of extremely low frequency communication is that underwater platforms such as underwater vehicles need to use a towed buoyancy cable antenna hundreds of meters long for reception, which is not conducive to the concealment and mobility of underwater platforms.

[0003] For underwater extremely low frequency magnetic field communication, the traditionally used receiver is a magnetic induction coil receiver. The magnetic induction coil receiver is limited by Faraday's law of electromagnetic induction in the extremely low frequency band. Therefore, the sensor probe is long and heavy, not suitable for portable application scenarios, and the reduction of the induced signal intensity leads to a decrease in sensor sensitivity. On the other hand, the magnetic induction coil is a vector magnetic field sensor, and the magnetic field detection output is sensitive to the direction of the sensor probe. Therefore, it is greatly affected by the motion and vibration-induced noise of the dynamic platform. Moreover, when multiple receivers are combined to form a gradiometer or an array, the directions of the receiver probes need to be strictly aligned to effectively suppress the common-mode ambient magnetic field noise, increasing the installation and operation difficulty. Therefore, it is of great significance to provide an extremely low frequency magnetic field communication receiver with high sensitivity, miniaturization, light weight, and based on a scalar magnetic sensor. Summary of the Invention

[0004] The purpose of the present invention is to provide an extremely low frequency magnetic field communication receiver based on an atomic magnetometer, to solve the technical problems in the prior art that the magnetic field sensor of the magnetic induction coil receiver for extremely low frequency communication is large in volume, heavy in weight, and greatly affected by the motion and vibration-induced noise of the dynamic carrier platform, to meet the requirements of being highly sensitive, miniaturized, and light in weight, and to be suitable for application scenarios that require portability or installation on a dynamic carrier platform or a mechanical vibration platform.

[0005] To achieve the above purpose, the technical solution of the present invention is as follows:

[0006] An extremely low frequency magnetic field communication receiver based on an atomic magnetometer, the core sensor of the extremely low frequency magnetic field communication receiver is a scalar atomic magnetometer, and the extremely low frequency magnetic field communication receiver based on an atomic magnetometer includes a meter head and a controller electrically connected to the meter head;

[0007] The header includes:

[0008] A VCSEL laser, which is internally integrated with a beam expander lens and emits laser light for optical pumping of rubidium-87 atoms and detection of FID (Free Induction Decay) signals. The VCSEL laser contains a non-magnetic heating sheet for temperature control and a temperature measuring element; and

[0009] An atomic gas cell, a micro alkali metal atomic vapor cell of a mixture of rubidium-87 and buffer gas; and

[0010] An incubator, a box for placing the atomic gas cell and maintaining it in a constant temperature environment. The incubator contains a non-magnetic heating sheet and a temperature measuring element; and

[0011] A λ / 4 wave plate, which converts the laser light into a circularly polarized light beam; and

[0012] A photodiode, which detects the light intensity signal of the light beam passing through the atomic gas cell; and

[0013] A polarization magnetic field coil, a set of uniform magnetic field coils of the polarization magnetic field along the x direction surrounding the atomic gas cell; and

[0014] Magnetic field gradient coils, a set of magnetic field gradient coils along the z direction and a set of magnetic field gradient coils along the y direction surrounding the atomic gas cell.

[0015] Furthermore, the controller includes a header drive circuit and an FPGA-based signal processor ARM+FPGA that runs an automatic working algorithm to control the drive circuit using a digital feedback loop; the drive circuit includes:

[0016] A phototube preamplifier circuit, which is used to convert the current signal of the phototube PD into a voltage signal; and

[0017] A laser drive circuit, which provides and feedback-controls the injection current and temperature control heating current of the VCSEL laser to stabilize the optical power and wavelength; and

[0018] An atomic gas cell temperature control circuit, which provides and feedback-controls the temperature control heating current of the incubator; and

[0019] A polarization magnetic field drive circuit, which provides the polarization magnetic field coil current; and

[0020] A magnetic field gradient compensation circuit, which provides the magnetic field gradient coil current.

[0021] Furthermore, the FPGA-based signal processor ARM+FPGA includes:

[0022] A frequency meter, which measures the frequency of the rubidium-87 atomic FID signal output by the phototube preamplifier circuit and outputs a magnetic field value proportional to the frequency value; and

[0023] The lock-in amplifier further demodulates the magnetic field signal output by the frequency meter according to the known signal magnetic field frequency to obtain the magnetic field amplitude and phase information, so as to restore the symbol information of the amplitude-modulated or phase-modulated magnetic field signal.

[0024] Furthermore, the FPGA-based signal processor ARM+FPGA also includes a laser control program, an atomic gas chamber temperature control program, a polarized magnetic field drive program, and a magnetic field gradient compensation program; the laser control program feedback-controls the laser drive circuit, the atomic gas chamber temperature control program feedback-controls the atomic gas chamber temperature control circuit, the polarized magnetic field drive program controls the polarized magnetic field drive circuit, and the magnetic field gradient compensation program controls the magnetic field gradient compensation circuit.

[0025] Furthermore, when the environmental magnetic field gradient is too large and the Larmor precession signal decays rapidly and the frequency meter cannot effectively measure it, the magnetic field gradient compensation program controls the magnetic field gradient compensation circuit to provide the magnetic field gradient coil current through a compensation algorithm to compensate for the environmental magnetic field gradient and obtain an effectively measurable Larmor precession signal.

[0026] Furthermore, the extremely low-frequency magnetic field communication receiver can detect the signal magnetic field in any vibration direction. When the vibration direction of the signal magnetic field is consistent with the direction of the geomagnetic field at the position of the head of the extremely low-frequency magnetic field communication receiver, the change amplitude of the detected total magnetic field amplitude is the largest, that is, the detected signal magnetic field is the strongest; when the vibration direction of the signal magnetic field is perpendicular to the direction of the geomagnetic field at the position of the head of the extremely low-frequency magnetic field communication receiver, the change amplitude of the detected total magnetic field amplitude is the smallest, that is, the detected signal magnetic field is the weakest.

[0027] Furthermore, when two extremely low-frequency magnetic field communication receivers are combined together and the heads of the two extremely low-frequency magnetic field communication receivers are arranged in a mutually orthogonal manner according to the optical axis direction, it can be ensured that the extremely low-frequency magnetic field communication receiver can detect the magnetic field to be measured in any direction and eliminate the measurement "dead zone".

[0028] Furthermore, two extremely low-frequency magnetic field communication receivers separated by a certain distance can form a magnetic field gradiometer. The head directions of the two extremely low-frequency magnetic field communication receivers do not need to be strictly aligned. The magnetic field gradient of the transmitted signal magnetic field is detected through differential calculation to cancel the environmental magnetic field noise, improve the sensitivity of the extremely low-frequency magnetic field communication receiver, and increase the communication distance.

[0029] Furthermore, when multiple extremely low-frequency magnetic field communication receivers are arranged at a certain interval, and the head directions of each extremely low-frequency magnetic field communication receiver do not need to be strictly aligned, a receiver array can be formed. The method of coherent accumulation and beam synthesis is used to enhance the detection signal-to-noise ratio, improve the sensitivity of the extremely low-frequency magnetic field communication receiver, and increase the communication distance.

[0030] With the above technical solution, the present invention has the following advantages:

[0031] The present invention provides an extremely low-frequency magnetic field communication receiver based on an atomic magnetometer. The core sensor of this receiver is a scalar atomic magnetometer. Compared with traditional magnetic induction coil receivers, the receiver of the present invention is not limited by the electromagnetic induction law and the thermal noise limit of magnetic induction coils. Under the same probe volume condition, it has higher sensitivity for detecting extremely low-frequency magnetic fields, and has the advantages of miniaturization and light weight. The magnetic field detection output of the receiver is insensitive to the head direction, and is less affected by dynamic platform movement and vibration-induced noise. It is suitable for application scenarios that require portability or installation on dynamic carrier platforms and mechanical vibration platforms. Multiple receivers do not require strict alignment of the head directions, and it is easy to form a magnetic field gradiometer or array, which improves the receiver sensitivity, increases the communication distance, and enhances the covert communication ability. Description of the Drawings

[0032] Figure 1 It is a structural composition diagram of the head of the extremely low-frequency magnetic field communication receiver of the present invention;

[0033] Figure 2 It is a structural composition diagram of the controller of the extremely low-frequency magnetic field communication receiver of the present invention;

[0034] Figure 3 It is a working process diagram of the extremely low-frequency magnetic field communication receiver of the present invention;

[0035] Figure 4 It is the head arrangement mode of a combination of two extremely low-frequency magnetic field communication receivers for eliminating the measurement "dead zone" of the present invention;

[0036] Figure 5 It is for the extremely low-frequency magnetic field communication receiver of the present invention to detect the signal magnetic field in any vibration direction. Detailed Embodiments

[0037] The technical solution of the present invention will be specifically described below in conjunction with the drawings of the specification. It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover a non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements, but also other elements not expressly listed, or elements inherent to such process, method, article or device.

[0038] An extremely low-frequency magnetic field communication receiver based on an atomic magnetometer, whose core sensors include, but are not limited to, scalar atomic magnetometers with the free induction decay (FID) and other types of working principles. This embodiment is a scalar atomic magnetometer based on the free induction decay working principle and the pulsed optical pumping working mode. The receiver of the present invention consists of two parts: a head and a controller electrically connected to the head. The structure of the head is specifically as shown in Figure 1 shown, including a VCSEL laser 1, a λ / 4 wave plate 2, a polarization magnetic field coil A, magnetic field gradient coils B and C, an atomic gas cell 3, a thermostatic chamber 4, a photodiode PD5. All components inside the head are non-magnetic materials.

[0039] The working process of the head is as follows: The VCSEL laser 1 emits a 795 nm linearly polarized light resonant with the D1 line of rubidium-87 atoms, which becomes circularly polarized light after passing through the λ / 4 quartz wave plate 2. Through the laser driver circuit in the controller, the output optical power of the VCSEL laser 1 is about 0.2 mW, and the temperature control accuracy is less than 10 mK through the internal non-magnetic heating sheet and temperature measuring element.

[0040] The circularly polarized light irradiates the micro atomic gas cell 3 filled with a mixture of rubidium-87 and buffer gas along the x direction, which is used for optical pumping of rubidium-87 atoms and detection of FID signals; the thermostatic chamber 4 keeps the internal atomic gas cell 3 in a constant temperature environment, and the temperature is maintained at about 80 °C with a temperature control accuracy less than 10 mK through the internal non-magnetic heating sheet and temperature measuring element; the polarization magnetic field coil A in the x direction generates a uniform strong polarization magnetic field along the x direction close to 1 mT; the magnetic field gradient coils B and C in the z direction and y direction generate a gradient magnetic field for compensating the environment with a certain magnitude and direction; the photodiode PD5 detects the optical intensity signal of the light beam passing through the atomic gas cell 3.

[0041] The controller is specifically as shown in Figure 2 shown, including a driver circuit and an FPGA-based signal processor ARM+FPGA that controls the driver circuit. The driver circuit includes the following modules: a phototube preamplifier circuit, a laser driver circuit, an atomic gas cell temperature control circuit, a polarization magnetic field driver circuit, and a magnetic field gradient compensation circuit; the FPGA-based signal processor ARM+FPGA runs the automatic working algorithm of the entire receiver and controls all driver circuits using a digital feedback loop, including the following modules: a frequency meter, a lock-in amplifier, a laser control program, an atomic gas cell temperature control program, a polarization magnetic field driver program, and a magnetic field gradient compensation program.

[0042] The working process of the controller is as follows: First, the laser driver circuit provides and feedback-controls the injection current and temperature control heating current of the VCSEL laser to stabilize the optical power and wavelength; the atomic gas cell temperature control circuit provides and feedback-controls the temperature control heating current of the thermostatic chamber.

[0043] Next, the working process is divided into two stages, the polarization stage and the measurement stage, which are repeated every 10 ms cycle time, specifically as Figure 3 shown.

[0044] Within t = 0 - 5 ms, the polarization magnetic field driving program controls the polarization magnetic field driving circuit to supply current to the polarization magnetic field coil, generating a strong polarization magnetic field Under the combined action of the laser and the longitudinal polarization field, the rubidium - 87 atoms undergo spin polarization along the polarization field direction, and the initial polarization rate According to the Bloch equation describing the spin dynamics The polarization rate along the polarization direction, i.e., the x - axis direction, is solved as The polarization rate P x (t) changes are reflected in the change of the light intensity absorption by the atomic gas cell 3. The pre - amplifier circuit of the phototube converts the current signal of the photodiode PD5 into a voltage signal, and outputs the change signal of the rubidium - 87 atom polarization stage as Figure 3 shown in the left - hand part.

[0045] At t = 5 ms, after the polarization rate P x (t) stabilizes, the polarization magnetic field driving program controls the polarization magnetic field driving circuit to quickly turn off the polarization field within a few μs The measurement stage t = 5 - 10 ms starts. Assume the total magnetic field to be measured is along the z - axis direction, where is the geomagnetic field, is the signal magnetic field. According to the Bloch equation, it is solved that That is, the spin of the rubidium - 87 atoms will perform Larmor precession with exponential decay around i.e., free induction decay FID. The precession frequency ω 0 is proportional to the magnitude of the magnetic field B to be measured 0 i.e., ω 0 = γB 0 , and the proportionality coefficient γ = 6.998 nT / Hz is the gyromagnetic ratio of the rubidium - 87 atom. The pre - amplifier circuit of the phototube outputs the FID signal of the rubidium - 87 atom in the measurement stage as Figure 3 shown in the right - hand part.

[0046] Then, a frequency meter measures the frequency ω 0 of the FID signal of the rubidium - 87 atom output by the pre - amplifier circuit of the phototube through a high - precision frequency - measuring algorithm, and calculates and outputs the exact value of the total magnetic field B 0 to be measured according to the gyromagnetic ratio γ. After the measurement stage of the current cycle ends, the polarization stage of the next cycle starts, and so on in a loop.

[0047] The frequency ω 0 of the FID signal of the rubidium - 87 atom depends only on the magnitude of the total magnetic field and is independent of the respective field components (B x , B y , B z ) of the field. Therefore, the core sensor of this receiver is a scalar atomic magnetometer. The magnetic field detection output result of the receiver is not sensitive to the head direction and is less affected by the motion and vibration-induced noise of the dynamic platform.

[0048] Since the sampling period of the magnetic field measurement is 10 ms, that is, the sampling rate is 100 Hz, the receiver bandwidth is 50 Hz. Assume that this receiver is used to detect the magnetic field of a signal with a known frequency of 10 Hz Next, a lock-in amplifier is used to demodulate the signal of the total magnetic field B 0 value output by the frequency meter for a period of time to obtain the amplitude and phase information of the signal magnetic field so as to recover the communication symbol information.

[0049] This receiver has a magnetic field measurement range. The lower limit of the range is limited by the requirement that the precession frequency of the FID signal is greater than the relaxation rate; the upper limit of the range is limited by the limited signal processing capabilities of modules such as the frequency meter.

[0050] When the environmental magnetic field gradient is too large, such as 1000 nT / cm, the FID signal decays rapidly during the measurement stage and the frequency meter cannot effectively measure it. At this time, the magnetic field gradient compensation program is started. Through the compensation algorithm, the magnetic field gradient compensation circuit is feedback-controlled to provide a certain magnetic field gradient coil current to compensate the environmental magnetic field gradient to, for example, below 100 nT / cm to obtain an effectively measurable FID signal. After compensating the environmental magnetic field gradient, it enters the polarization stage of the next working cycle.

[0051] The measurement "dead zone" of the extremely low frequency magnetic field communication receiver is within a cone with an axis along the optical axis direction of the receiver's head and an included angle of several degrees. That is, when the optical axis direction of the receiver's head is close to parallel to the direction of the magnetic field to be measured, the extremely low frequency magnetic field communication receiver cannot detect the magnetic field. Two extremely low frequency magnetic field communication receivers (① and ②) can be combined together so that the two heads are arranged orthogonally according to the optical axis direction, as specifically shown in Figure 4 shown, so as to ensure that the extremely low frequency magnetic field communication receiver can detect the magnetic field to be measured in any direction, that is, the measurement "dead zone" is eliminated.

[0052] The extremely low frequency magnetic field communication receiver can detect the signal magnetic field in any vibration direction, as specifically shown in Figure 5As shown. When the vibration direction of the signal magnetic field is consistent with the direction of the geomagnetic field at the position of the head of the extremely low frequency magnetic field communication receiver, the change amplitude of the detected total magnetic field amplitude is the largest, that is, the detected signal magnetic field is the strongest; when the vibration direction of the signal magnetic field is perpendicular to the direction of the geomagnetic field at the position of the head of the extremely low frequency magnetic field communication receiver, the change amplitude of the detected total magnetic field amplitude is the smallest, that is, the detected signal magnetic field is the weakest.

[0053] Place two extremely low frequency magnetic field communication receivers at a distance of, for example, 10 m apart. The head directions of the two receivers do not need to be strictly aligned, and a magnetic field gradiometer can be formed. Then, perform differential calculation on the outputs of the two extremely low frequency magnetic field communication receivers to detect the magnetic field gradient of the transmitted signal, which can cancel the environmental magnetic field noise, improve the receiver sensitivity, and increase the communication distance.

[0054] Arrange multiple extremely low frequency magnetic field communication receivers in a matrix at intervals of, for example, 10 m in both horizontal and vertical directions. The head directions of each extremely low frequency magnetic field communication receiver do not need to be strictly aligned, and a receiver array can be formed. Use the methods of coherent accumulation and beam synthesis to enhance the detection signal-to-noise ratio, improve the receiver sensitivity, and increase the communication distance.

[0055] Finally, it should be pointed out that although the present invention has been described with reference to the current specific embodiments, those of ordinary skill in the art should recognize that the above embodiments are only used to illustrate the present invention and are not used to limit the present invention. Various equivalent changes or substitutions can be made without departing from the concept of the present invention. Therefore, as long as the changes and modifications of the above embodiments are within the scope of the spirit of the present invention, they will fall within the scope of the claims of the present invention.

Claims

1. An extremely low frequency magnetic field communication receiver based on an atomic magnetometer, characterized in that: The core sensor of the extremely low frequency magnetic field communication receiver is a scalar atomic magnetometer. The extremely low frequency magnetic field communication receiver based on the atomic magnetometer comprises a meter head and a controller electrically connected to the meter head. The table header includes: A VCSEL laser having an integrated beam expansion lens, emitting laser light for optical pumping of rubidium 87 atoms and detection of FID (free induction decay) signals, wherein the VCSEL laser contains a non-magnetic heating plate for temperature control and a temperature measuring element; and Atomic gas cells, miniature alkali metal atomic vapor cells of rubidium 87 and buffer gas mixture; and An insulated box, a box in which the atomic gas chamber is placed and maintained in a constant temperature environment, wherein the insulated box contains a non-magnetic heating sheet and a temperature measuring element; and λ / 4 wave plate, which converts the laser light into a circularly polarized light beam; and A photodiode for detecting a light intensity signal of the light beam after passing through the atomic gas chamber; and A polarized magnetic field coil, a group of uniform magnetic field coils with a polarized magnetic field along the x-direction surrounded by the atomic gas chamber; and The magnetic field gradient coils include a group of magnetic field gradient coils along the z direction and a group of magnetic field gradient coils along the y direction surrounded by the atomic gas chamber.

2. The extremely low frequency magnetic field communication receiver based on an atomic magnetometer according to claim 1, characterized in that: The controller includes a meter drive circuit and an FPGA-based signal processor ARM+FPGA that runs an automatic working algorithm and controls the drive circuit using a digital feedback loop; the drive circuit includes: A photoelectric tube preamplifier circuit, used for converting the current signal of the photoelectric tube PD into a voltage signal; and Laser drive circuitry that provides and feedback controls the VCSEL laser injection current and temperature-controlled heating current to stabilize optical power and wavelength; and Atomic gas temperature control circuit, providing and feedback controlling the temperature control heating current of the incubator; and A polarization magnetic field driving circuit, providing a polarization magnetic field coil current; and The magnetic field gradient compensation circuit provides the magnetic field gradient coil current.

3. The extremely low frequency magnetic field communication receiver based on an atomic magnetometer according to claim 2, characterized in that: The FPGA-based signal processor ARM+FPGA includes: A frequency meter measures the frequency of the rubidium 87 atomic FID signal output by the photoelectric tube preamplifier circuit and outputs a magnetic field value proportional to the frequency value; and The phase-locked amplifier further demodulates the magnetic field signal output by the frequency meter according to the known signal magnetic field frequency to obtain the magnetic field amplitude and phase information, thereby recovering the code element information of the amplitude modulated or phase modulated magnetic field signal.

4. The extremely low frequency magnetic field communication receiver based on an atomic magnetometer according to claim 3, characterized in that: The FPGA-based signal processor ARM+FPGA also includes a laser control program, an atomic gas room temperature control program, a polarization magnetic field driver program and a magnetic field gradient compensation program; the laser control program feedback controls the laser drive circuit, the atomic gas room temperature control program feedback controls the atomic gas room temperature control circuit, the polarization magnetic field driver program controls the polarization magnetic field drive circuit, and the magnetic field gradient compensation program controls the magnetic field gradient compensation circuit.

5. The extremely low frequency magnetic field communication receiver based on an atomic magnetometer according to claim 4, characterized in that: When the ambient magnetic field gradient is too large, the Larmor precession signal decays quickly and the frequency meter cannot measure it effectively. The magnetic field gradient compensation program controls the magnetic field gradient compensation circuit to provide magnetic field gradient coil current through a compensation algorithm to compensate for the ambient magnetic field gradient and obtain a Larmor precession signal that can be effectively measured.

6. The extremely low frequency magnetic field communication receiver based on an atomic magnetometer according to claim 5, characterized in that: The extremely low frequency magnetic field communication receiver can detect signal magnetic fields of any vibration direction. When the signal magnetic field vibration direction is consistent with the geomagnetic field direction at the location of the extremely low frequency magnetic field communication receiver head, the detected total magnetic field amplitude change amplitude is the largest, that is, the detected signal magnetic field is the strongest; when the signal magnetic field vibration direction is perpendicular to the geomagnetic field direction at the location of the extremely low frequency magnetic field communication receiver head, the detected total magnetic field amplitude change amplitude is the smallest, that is, the detected signal magnetic field is the weakest.

7. The extremely low frequency magnetic field communication receiver based on an atomic magnetometer according to claim 6, characterized in that: The two extremely low frequency magnetic field communication receivers are combined together so that the two extremely low frequency magnetic field communication receiver heads are arranged in a manner orthogonal to each other in the direction of the optical axis, which can ensure that the extremely low frequency magnetic field communication receiver can detect the magnetic field to be measured in any direction and eliminate the measurement "dead zone".

8. The extremely low frequency magnetic field communication receiver based on an atomic magnetometer according to claim 7, characterized in that: Two extremely low frequency magnetic field communication receivers separated by a certain distance can constitute a magnetic field gradiometer. The directions of the two extremely low frequency magnetic field communication receivers do not need to be strictly aligned. The magnetic field gradient of the transmitted signal magnetic field is detected by differential calculation to offset the environmental magnetic field noise, improve the sensitivity of the extremely low frequency magnetic field communication receiver, and increase the communication distance.

9. The extremely low frequency magnetic field communication receiver based on an atomic magnetometer according to claim 8, characterized in that: A plurality of the extremely low frequency magnetic field communication receivers are arranged at a certain interval, wherein the header directions of each of the extremely low frequency magnetic field communication receivers do not need to be strictly aligned, and a receiver array can be formed. The coherent accumulation and beam synthesis methods are used to enhance the detection signal-to-noise ratio, improve the sensitivity of the extremely low frequency magnetic field communication receiver, and increase the communication distance.

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