A systematic verification method using magnetic fields instead of electromagnetic waves as a channel

Abstract

This invention claims protection for a systematic verification method that uses magnetic fields rather than electromagnetic waves as a communication channel. This method, pertaining to the field of communications technology, verifies the theory of magnetic induction communication from four perspectives: near-field electromagnetic wave theory, the transmission formula for magnetic induction communication, the relationship between the center frequency of electromagnetic waves and the optimal antenna length, and the impact of the properties of the transmission medium on communication. This method demonstrates from multiple perspectives that antennas with corresponding structures in magnetic induction communication theory transmit signals through magnetic induction rather than electromagnetic waves, thus avoiding the limitations and incompleteness of a single verification method.

Description

Technical Field

[0001] The present invention relates to the field of communication technology, and in particular to a systematic verification method using a magnetic field instead of an electromagnetic wave as a channel. Background Art

[0002] In recent years, the increasing utilization of underground space and resources for industrial production and urbanization in my country, as well as the development and application of marine resources in various countries around the world, have placed higher demands on underground and underwater wireless communication equipment. In such environments, wired networks, due to their complex wiring and high costs, are no longer able to meet these needs. Traditional wireless networks use electromagnetic wave propagation for wireless communication. However, in complex underground environments, electromagnetic waves are easily affected by complex media such as soil, sand, gravel, and moisture, resulting in high path loss, unstable channels, and large antenna sizes. Due to water absorption, radio waves also experience severe attenuation underwater, with the attenuation increasing with frequency. Therefore, the development of new wireless communication technologies is urgent.

[0003] Magnetic induction communication uses magnetic fields as a carrier, transmitting information by varying the magnetic field's strength. The advantages of magnetic induction communication include: wireless information transmission between transmitting and receiving antennas is achieved through magnetic coupling, eliminating multipath effects; and the magnetic permeability of the transmission medium, such as reefs and seawater, is approximately the same, so variations in the transmission medium in underwater and underground environments have minimal impact on wireless magnetic induction communication. Consequently, magnetic induction communication channels are stable. Furthermore, magnetic induction communication is highly concealed, making it difficult to detect with the precision of existing detection equipment. This makes it advantageous in both underwater and underground environments, and its application prospects are promising. Furthermore, magnetic induction communication antennas can be fabricated using ordinary copper wire, resulting in a simple structure and inexpensive production costs. Consequently, this method has garnered widespread attention in academia. However, existing research has primarily focused on the implementation of application functions, with the channel often overlooked, failing to fully demonstrate that the channel implementing these functions is indeed a magnetic field, rather than traditional electromagnetic waves. Summary of the Invention

[0004] The present invention aims to solve the above problems of the prior art. It proposes a systematic verification method that uses magnetic fields instead of electromagnetic waves as a channel. The technical solution of the present invention is as follows:

[0005] A systematic verification method using magnetic fields instead of electromagnetic waves as a channel, comprising the following steps:

[0006] S1: Establish a magnetic induction communication system model;

[0007] S2: Systematically verify that the communication system established in S1 uses magnetic fields rather than electromagnetic waves as the communication channel, including:

[0008] S21: Verification based on the near-field theory of electromagnetic waves;

[0009] S22: Verify by transmission formula or mutual inductance formula;

[0010] S23: reverse denial is performed by setting the carrier frequency and the theoretical formula of the optimal length of the electromagnetic wave antenna;

[0011] S24: Experimental verification of the impact of the properties of the transmission medium on communication;

[0012] S25: Analyze the verification results of S21-S24 and draw conclusions.

[0013] Furthermore, the S1 establishes a magnetic induction communication system model including the following physical devices and instruments:

[0014] Directional antenna: A circular coil with a certain number of turns and radius made of wire, with two endpoints;

[0015] Resonant capacitor: sets the resonant frequency f. Its capacitance is calculated based on the inductance of the directional antenna and the set resonant frequency.

[0016] Signal generator: outputs a modulation signal U with the resonant frequency f as the carrier frequency S ;

[0017] Oscilloscope: detects the received signal.

[0018] Furthermore, the S1 magnetic induction communication system model includes a transmitting circuit, a receiving circuit and a channel;

[0019] Transmitter circuit: The number of turns is N t , radius a t Directional antenna L t and the resonant capacitor C t After connecting in parallel or series, connect the signal generator to form;

[0020] Receiving circuit: The number of turns is N r , radius a r Directional antenna L r and the resonant capacitor C r After connecting in parallel or in series, the oscilloscope is connected;

[0021] Channel: It is composed of the magnetic field excited by the directional antennas in the transmitting circuit and the receiving circuit placed coaxially with a distance d.

[0022] Furthermore, the specific process of verifying according to the near-field theory of electromagnetic waves in S21 includes the following steps:

[0023] S211: Calculate the wavelength according to the set carrier frequency;

[0024]

[0025] Where c represents the speed of light;

[0026] S212: Compare the calculation result of S211 with the set distance d. If the set distance d is much smaller than the calculation result of S211, the verification of S21 is successful.

[0027] Furthermore, the specific process of verifying by the transmission formula or the mutual inductance formula in S22 includes the following steps:

[0028] S221: Using Ansys Maxwell software to simulate the magnetic induction communication system and calculate the mutual inductance of the two directional antennas;

[0029] S222: Estimate the mutual inductance of the two directional antennas in the magnetic induction communication system according to an empirical formula for calculating the mutual inductance coefficient (as shown in the following formula);

[0030]

[0031] Where μ represents magnetic permeability;

[0032] S223: Analyze and compare the results of S221 and S222. If the two are the same within the allowable error range, the S22 verification is successful.

[0033] Furthermore, the specific process of performing reverse denial in S23 by setting the theoretical formula of the carrier frequency and the optimal length of the electromagnetic wave antenna includes the following steps:

[0034] S231: Calculating the optimal antenna length according to the set carrier frequency and the theoretical formula of the optimal length of the electromagnetic wave antenna;

[0035]

[0036] S232: Compare the calculation result of S231 with the size and shape of the directional antenna. If the two are very different, it can be said that the channel is not an electromagnetic wave, and S23 verification is successful.

[0037] Furthermore, the specific process of experimentally verifying the influence of the properties of the transmission medium on the communication in S24 includes the following steps:

[0038] S241: performing an experiment in free space, wherein the transmitting circuit transmits a sine wave having a frequency f, and recording a peak-to-peak value of a voltage of the signal received by an oscilloscope in the receiving circuit;

[0039] S242: Based on S241, while ensuring that other conditions remain unchanged, a non-magnetic and conductive barrier is added to the channel, and the experiment is conducted again, and the experimental results are recorded;

[0040] S243: Analyze and compare the experimental results of S241 and S242. If the two are the same within the allowable error range, the verification of S24 is successful.

[0041] Furthermore, the specific operation of analyzing the verification results of S21-S24 and drawing a conclusion in S25 is: if S21-S24 are all successfully verified, it can be verified that the magnetic induction communication system model established in S1 uses the magnetic field rather than the electromagnetic wave as the channel.

[0042] The advantages and beneficial effects of the present invention are as follows: the innovation of the present invention mainly combines the four separate verification methods S21-S24, analyzes the antennas of corresponding structures in the magnetic induction communication theory from different perspectives, and includes both theoretical analysis and derivation as well as computational simulation and experimental verification, which fully proves that the established system uses magnetic fields rather than electromagnetic waves as channels, avoiding the limitations and incompleteness caused by one-sided and single verification methods in existing studies, and has very important guiding significance for future research. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 The present invention provides a flowchart of a systematic verification method using a magnetic field instead of an electromagnetic wave as a channel according to a preferred embodiment;

[0044] Figure 2 This is a diagram of a communication model structure abstracted from a specific embodiment of the present invention;

[0045] Figure 3 A diagram showing the physical locations of two directional antennas for use in a specific embodiment of the present invention;

[0046] Figure 4 This is a graph showing how mutual inductance changes with radius in a specific embodiment of the present invention;

[0047] Figure 5 This is a graph showing how mutual inductance changes with distance in a specific embodiment of the present invention;

[0048] Figure 6 This is a graph showing how mutual inductance changes with the number of turns in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0049] The following will describe the technical solutions in the embodiments of the present invention in detail with reference to the accompanying drawings. The described embodiments are only a part of the embodiments of the present invention.

[0050] The technical solution of the present invention to solve the above technical problems is:

[0051] The present invention proposes a systematic verification method using magnetic field instead of electromagnetic wave as a channel. To explain the specific implementation method more clearly, the overall block diagram is given as follows: Figure 1 shown.

[0052] S1: Establish a magnetic induction communication system model; the abstracted communication model structure diagram is as follows Figure 2 Shown, including:

[0053] Directional antenna: Made of 1mm diameter enameled wire, it is a circular coil with a radius of 5cm and 3 turns. There is one in each of the transmitting and receiving circuits, and the two are coaxially placed. The physical location is as follows: Figure 3 As shown, the physical parameters of the two enameled coils are exactly the same, and the measured inductance of the coil is 2.46uH. Figure 2 The abstract representation is a pair of coupled inductors;

[0054] Capacitor: Match according to the resonant frequency set later;

[0055] Signal generator: Modeled as an ideal voltage source and a resistor R S The output is a modulation signal U with the resonant frequency f as the carrier frequency. S ;

[0056] Oscilloscope: Modeled as a resistor R L It is connected in parallel with an ideal voltmeter to detect the received signal;

[0057] A directional antenna L t and matching capacitor C t After parallel connection, connect the signal generator to form the sending end circuit of the communication model; a directional antenna L r and matching capacitor C r After parallel connection, connect to an oscilloscope to form the receiving end circuit of the communication model.

[0058] Due to physical device and site limitations, subsequent experiments were conducted with a communication distance d of no more than 3 meters and a resonant frequency f of no more than 30 MHz. Due to environmental interference, calculation accuracy, and measurement precision, errors are inevitable between simulation and experimental values. This verification system specifies an allowable error of no more than 20%.

[0059] S2: Systematically verify that the communication system established in S1 uses magnetic fields instead of electromagnetic waves as the channel. The specific verification steps are as follows:

[0060] S21: Verification based on the near-field theory of electromagnetic waves; details are as follows:

[0061] Typically, the near field refers to the range from the antenna to one wavelength (λ). Within this range, the magnetic field dominates for directional antennas, and the near field increases as the frequency decreases. The maximum resonant frequency f is set to 30 MHz, which means the maximum carrier frequency is 30 MHz. Therefore, the minimum near field range is 10 meters.

[0062] Since the maximum communication distance d is set to 3 meters and the minimum near-field range is 10 meters, the minimum near-field range is greater than the maximum communication distance, so S21 verification is successful.

[0063] S22: Verify using the transmission formula or mutual inductance formula, as follows:

[0064] According to the above communication system, let the current flowing through the signal generator be I t , the current flowing through the oscilloscope is I r , L t The current is I Lt , flows through L r The current is I Lr , flows through C t The current is I Ct , flows through C r The current is I Cr According to Kirchhoff's voltage law and Kirchhoff's current law, we can list the equations shown in formula (1), where t represents time.

[0065]

[0066] From formula (1), it can be seen that the attenuation of the signal during transmission depends on the mutual inductance of the two directional antennas. According to the empirical formula (2), when the magnetic permeability μ is constant, it can be seen that the mutual inductance M is mainly related to the number of turns N of the transmitting and receiving antennas. r 、N t 、Radius of the transmitting and receiving antenna a r 、a t , and the distance d between the two antennas. Next, the control variable method will be used for research.

[0067]

[0068] The wire diameter of the directional antenna is set to be 1mm, the number of turns is 3, the distance between the two directional antennas is 1 meter, and the radius varies from 3 to 7 cm. Ansys Maxwell software is used for simulation, and the same parameters are substituted into formula (2) for calculation. The mutual inductance changes with radius as shown in the following figure: Figure 4 shown.

[0069] The number of turns of the directional antenna is set to 3, the radius is 5 cm, and the distance between the two directional antennas varies from 2 to 16 dm. Ansys Maxwell software is used for simulation, and the same parameters are substituted into formula (2) for calculation. The change of mutual inductance with distance is shown as follows: Figure 5 shown.

[0070] The radius of the directional antenna is set to 5 cm, the distance between the two directional antennas is 1 meter, and the number of turns varies from 1 to 10. Ansys Maxwell software is used for simulation, and the same parameters are substituted into formula (2) for calculation. The mutual inductance changes with the number of turns as shown in Figure 6 shown.

[0071] from Figure 4-6 It can be seen that, in ensuring d>>a r ,a t In this case, the theoretical formula and the simulation calculation results are roughly the same within the allowable error range, so S22 is successfully verified.

[0072] S23: Reverse denial is performed by setting the carrier frequency and the theoretical formula of the optimal length of the electromagnetic wave antenna; the details are as follows:

[0073] The optimal total length of an electromagnetic wave antenna is generally considered to be 1 / 4 of the wavelength, and its shape is rod-shaped. If the carrier frequency is set to 30 MHz, the optimal antenna length is approximately 2.5 meters. The directional antenna mentioned above is a circular coil with a radius of 5 cm. Both its shape and length are far from the calculated results. In addition, the lower the frequency, the longer the electromagnetic wave antenna required. If electromagnetic waves are used as the channel, the above antenna cannot meet the requirements, so S23 verification is successful.

[0074] S24: Conduct experimental verification based on the impact of the properties of the transmission medium on communication; details are as follows:

[0075] The resonant frequency was set to 10MHz. A 100pF capacitor (consisting of a 60pF capacitor and a 40pF distributed capacitance within the directional antenna) was connected in parallel with the directional antenna to achieve resonance at this frequency. The signal generator was set to produce a 5V peak-to-peak sine wave with a 50Ω impedance match. Experiments were conducted with a wooden door, a wall, and air between the two directional antennas. With the wooden door between the two, the oscilloscope measured a peak-to-peak voltage of 5.08V in the receiving circuit, while the same distance in air resulted in a peak-to-peak voltage of 4.44V. With the wall between the two, the oscilloscope measured a peak-to-peak voltage of 80mV in the receiving circuit, while the same distance in air resulted in a peak-to-peak voltage of 95.2mV. The experimental results show that the results obtained with a non-magnetic and conductive medium are roughly equivalent to those obtained in free space, within the specified error range. Therefore, S24 verification was successful.

[0076] S25: Analyze the verification results of S21-S24 and draw conclusions; the details are as follows:

[0077] Since S21-S24 were all successfully verified, it can be determined that the channel of this system is a magnetic field rather than an electromagnetic wave.

[0078] The systems described in the above embodiments may be implemented by computer chips or entities, or by products with certain functions.

[0079] It should also be noted that the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, commodity, or apparatus that includes a series of elements includes not only those elements but also other elements not explicitly listed, or includes elements inherent to such process, method, commodity, or apparatus. In the absence of further limitations, an element defined by the phrase "comprises a ..." does not exclude the presence of other identical elements in the process, method, commodity, or apparatus that includes the element.

[0080] The above embodiments should be understood as merely illustrating the present invention and not as limiting the scope of protection of the present invention. After reading the contents of the present invention, technicians may make various changes or modifications to the present invention, and these equivalent changes and modifications also fall within the scope defined by the claims of the present invention.

Claims

1. A systematic verification method using magnetic fields instead of electromagnetic waves as a channel, characterized in that: The following steps are involved: S1: Establish a magnetic induction communication system model; S2: Systematically verify that the communication system established in S1 uses magnetic fields rather than electromagnetic waves as the communication channel, including: S21: Verification based on the near-field theory of electromagnetic waves; S22: Verify by transmission formula or mutual inductance formula; S23: reverse denial is performed by setting the carrier frequency and the theoretical formula of the optimal length of the electromagnetic wave antenna; S24: Experimental verification of the impact of the properties of the transmission medium on communication; S25: Analyze the verification results of S21-S24 and draw conclusions; The specific process of verifying according to the near-field theory of electromagnetic waves in S21 includes the following steps: S211: Calculate the wavelength according to the set carrier frequency; Where c represents the speed of light; S212: Compare the calculation result of S211 with the set distance d. If the set distance d is much smaller than the calculation result of S211, then S21 verification is successful. The specific process of verifying by the transmission formula or the mutual inductance formula in S22 includes the following steps: S221: Using Ansys Maxwell software to simulate the magnetic induction communication system and calculate the mutual inductance of the two directional antennas; S222: Estimate the mutual inductance value of two directional antennas in the magnetic induction communication system according to an empirical formula for calculating the mutual inductance coefficient; Where, μ represents the magnetic permeability; N t Directional antenna L for the transmitting circuit t The number of turns, a t Directional antenna L for the transmitting circuit t Radius, N r Directional antenna L for the receiving circuit r The number of turns, a r Directional antenna L for the receiving circuit r The radius of , d is the directional antenna distance; S223: Analyze and compare the results of S221 and S222. If the two are the same within the allowable error range, S22 verification is successful. The specific process of performing reverse denial by setting the carrier frequency and the theoretical formula of the optimal length of the electromagnetic wave antenna in S23 includes the following steps: S231: Calculating the optimal length of the electromagnetic wave antenna according to the set carrier frequency and a theoretical formula for the optimal length of the electromagnetic wave antenna; S232: Compare the calculated result of S231 with the size and shape of the directional antenna. If the two are significantly different, it can be determined that the channel is not an electromagnetic wave, and S23 verification is successful. The specific process of experimentally verifying the influence of the properties of the transmission medium on the communication in S24 includes the following steps: S241: performing an experiment in free space, wherein the transmitting circuit transmits a sine wave having a frequency f, and recording the peak-to-peak value of the voltage of the signal received by an oscilloscope in the receiving circuit; S242: Based on S241, while ensuring that other conditions remain unchanged, a non-magnetic and conductive barrier is added to the channel, and the experiment is conducted again, and the experimental results are recorded; S243: Analyze and compare the experimental results of S241 and S242. If the two are the same within the allowable error range, the verification of S24 is successful.

2. A systematic verification method using magnetic fields instead of electromagnetic waves as a channel according to claim 1, characterized in that: The S1 magnetic induction communication system model includes the following physical devices and instruments: Directional antenna: A circular coil with a certain number of turns and radius made of wire, with two endpoints; Resonant capacitor: sets the resonant frequency f. Its capacitance is calculated based on the inductance of the directional antenna and the set resonant frequency. Signal generator: outputs a modulation signal U with the resonant frequency f as the carrier frequency S ; Oscilloscope: detects the received signal.

3. A systematic verification method using a magnetic field instead of an electromagnetic wave as a channel according to claim 2, characterized in that: The S1 magnetic induction communication system model includes a transmitting end circuit, a receiving end circuit and a channel; Transmitter circuit: The number of turns is N t , radius a t Directional antenna L t and the resonant capacitor C t After connecting in parallel or series, connect the signal generator to form; Receiving circuit: The number of turns is N r , radius a r Directional antenna L r and the resonant capacitor C r After connecting in parallel or in series, the oscilloscope is connected; Channel: It is composed of the magnetic field excited by the directional antennas in the transmitting circuit and the receiving circuit placed coaxially with a distance d.

4. A systematic verification method using magnetic fields instead of electromagnetic waves as a channel according to claim 1, characterized in that: The specific operation of analyzing the verification results of S21-S24 and drawing conclusions in S25 is: if S21-S24 are all successfully verified, it can be verified that the magnetic induction communication system model established in S1 uses magnetic field rather than electromagnetic wave as the channel.

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