Carrier information modulation and demodulation method of controllable resonant magnetic pulse through-the-earth communication transmitter

Abstract

The application relates to a carrier information modulation and demodulation method of a controllable resonant magnetic pulse through-the-earth communication transmitter, and the method comprises the following steps: generating a magnetic pulse signal through a hardware topology of a magnetic pulse signal transmitter, wherein the hardware topology comprises a switch, a unidirectional conducting switch, a resonant capacitor and a solenoid; dividing the working period of an LC resonant system into four stages by controlling the conduction and shutdown of the switch and the unidirectional conducting switch; generating a non-continuous magnetic resonant signal pulse by dynamically adjusting the duration of each stage; designing an information modulation mechanism based on orthogonal code elements, generating the waveforms of code element 0 and code element 1, and ensuring the orthogonality by verifying the autocorrelation and cross-correlation; and realizing information demodulation at a receiving end by calculating the cross-correlation between the input non-continuous magnetic resonant signal and code element 0 and code element 1. The application solves the contradiction between radiation efficiency and signal bandwidth which cannot be considered in the existing through-the-earth system and modulation and demodulation method.

Description

Technical Field

[0001] This invention relates to the field of ground-penetrating communication technology, specifically a carrier information modulation and demodulation method for a controllable resonant magnetic pulse ground-penetrating communication transmitter, used to realize information transmission between the ground and underground or strata. Background Technology

[0002] Trans-ground communication technology originated in the early 20th century, initially relying mainly on low-frequency electromagnetic waves and elastic waves. However, due to limitations such as narrow bandwidth, low transmission efficiency, and poor anti-interference capabilities, it gradually became unable to meet modern communication needs. In recent years, with the rapid development of digital signal processing and wireless communication technologies, trans-ground communication technology has gradually evolved towards high efficiency, low latency, and high reliability, showing broad application prospects, especially in fields such as mine rescue, underground facility monitoring, and military communications.

[0003] Currently, mainstream ground-penetrating communication (PTC) systems are mainly based on the following three technologies: First, using low-frequency or extremely low-frequency electromagnetic waves to penetrate the strata for ground-penetrating transmission; second, generating low-frequency mechanical waves through mechanical elastic waves to penetrate rock masses for information transmission; and third, using low-frequency magnetic fields based on the principle of magnetic induction to achieve near-field energy and information transmission. In comparison, magnetic induction communication, with its superior penetration capability and anti-interference performance, has become an important technological direction in the field of TPC, and significant progress has been made in system design, signal processing, and modulation mechanisms. Patents (CN119560785A, Parallel Multi-Coil Magnetic Antenna and Ground-Penetrating Magnetic Communication System), (CN119135221A, A Method for Eliminating Inter-Channel Interference in a Magnetic Induction MIMO System Based on Zero-Forcing Precoding), and (CN118857273A, A Method and System for Detecting and Receiving Magnetic Induction Signals Based on an Unmanned Aerial Vehicle Platform) have made progress in transmitter antenna design, signal modulation, and technology application, respectively.

[0004] However, existing magnetic induction technologies employ traditional topologies (source, power amplifier, and antenna), which suffer from insurmountable theoretical bottlenecks (such as the contradiction between radiation efficiency and system bandwidth, and the inverse relationship between signal frequency and physical size). This not only makes it difficult to miniaturize deep-penetrating transmission systems but also limits the flexible application of modulation techniques, resulting in systems unable to support broadband information transmission.

[0005] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of the present invention, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0006] This invention provides a carrier information modulation and demodulation method for a controllable resonant magnetic pulse ground-penetrating communication transmitter, which solves the contradiction between radiation efficiency and signal bandwidth that is difficult to balance in existing ground-penetrating systems and modulation and demodulation methods.

[0007] Other features and advantages of the invention will become apparent from the following detailed description, or may be learned in part by practice of the invention.

[0008] According to a first aspect of the present invention, a carrier information modulation and demodulation method for a controllable resonant magnetic pulse ground-penetrating communication transmitter is provided, the method comprising:

[0009] The method includes:

[0010] A magnetic pulse signal is generated through a hardware topology of a magnetic pulse signal transmitter, the hardware topology including a first control switch K1 and a second control switch K2, a unidirectional conduction switch Q1, a resonant capacitor C, and a solenoid L;

[0011] By controlling the on and off states of the first control switch K1, the second control switch K2, and the unidirectional conduction switch Q1, the working cycle of the LC resonant system is divided into four stages: initial energy storage, alternating energy transfer between the capacitor and the inductor, energy recovery, and information loading window.

[0012] Discontinuous magnetic resonance signal pulses are generated by dynamically adjusting the duration of each stage;

[0013] An information modulation mechanism is designed based on orthogonal symbols to generate waveforms of symbol 0 and symbol 1, and orthogonality is ensured by verifying their autocorrelation and cross-correlation.

[0014] At the receiving end, information demodulation is achieved by calculating the cross-correlation between the input discontinuous magnetic resonance signal and symbol 0 and symbol 1.

[0015] In some exemplary embodiments, the working cycle of the LC resonant system is divided into four stages by controlling the on and off states of the first control switch K1, the second control switch K2, and the unidirectional conduction switch Q1, specifically:

[0016] First stage: The first controllable switch is turned on and the second controllable switch is turned off. The input voltage charges the resonant capacitor and the excitation current is zero.

[0017] Second stage: The first controllable switch is turned off and the second controllable switch is turned on. The excitation current flows from the resonant capacitor to the resonant inductor, and energy is transferred from the capacitor to the inductor.

[0018] Third stage: Both the first and second controllable switches are turned off, and the excitation current is fed back from the resonant inductor to the resonant capacitor, and flows through the unidirectional conducting element to form a circuit;

[0019] Fourth stage: The first and second controllable switches remain off, the unidirectional conducting element is cut off, completing one resonance cycle and forming a time window for information loading.

[0020] In some exemplary embodiments, the waveform of symbol 0 consists of N magnetic pulse signals, each with a period of T0 and an interval of Δt between adjacent magnetic pulse signals; the waveform of symbol 1 is generated by phase shifting the waveform of symbol 0, with a phase shift time of Δt. Where, τ i The interval between two consecutive complete sinusoidal signals is the time interval between each other.

[0021] In some exemplary embodiments, the verification of the orthogonality of codeword 0 and codeword 1 includes:

[0022] Calculate the autocorrelation and cross-correlation functions of code symbol 0 and code symbol 1;

[0023] If the autocorrelation peak is significant and the cross-correlation peak is close to zero, then code symbol 0 and code symbol 1 are determined to be orthogonal.

[0024] In some exemplary embodiments, the specific steps of the information demodulation include:

[0025] Initialize the signal buffer and define the length of the calculation window;

[0026] Read data sequentially from the input signal and update the buffer;

[0027] Calculate the cross-correlation between the input signal window and symbol 0 and symbol 1;

[0028] Compare the cross-correlation values ​​and decode them as 0 or 1;

[0029] The process continues until all input signals have been processed.

[0030] In some exemplary embodiments, the interval time τ i The following boundary conditions must be met:

[0031] The minimum value is greater than the minimum charging time τ of the capacitor. min , that is, τ i >τ min ;

[0032] The maximum value is determined by the minimum code rate R required by the system. min Decision, that is Where N is the number of sine wave periods.

[0033] In some exemplary embodiments, the minimum charging time τ of the capacitor m i n Calculated using the following formula:

[0034] τ min The capacitor voltage rises from its initial value to 0.99U. in The required time, of which

[0035] Capacitor voltage

[0036] The carrier information modulation and demodulation method for a controllable resonant magnetic pulse ground-penetrating communication transmitter provided in the embodiments of the present invention has the following advantages compared with the prior art:

[0037] 1. This invention is based on a single-component LC resonant unit, which significantly simplifies the hardware structure and reduces system complexity. By optimizing the information modulation and demodulation mechanism, it significantly improves the signal's anti-interference capability and reduces the bit error rate. This mechanism is simple, efficient, and suitable for various communication scenarios.

[0038] 2. This invention does not rely on complex hardware upgrades; bandwidth gain can be achieved solely through the orthogonality design of the information modulation and demodulation mechanisms. The orthogonality of symbol 0 and symbol 1 expands the signal spectrum, significantly improving anti-interference capabilities and increasing channel capacity, providing a flexible bandwidth optimization scheme for communication systems.

[0039] 3. This invention proposes an algorithm for optimally controlling the delay time by analyzing the boundary conditions of capacitor charging time. This ensures sufficient capacitor charging time, avoids system anomalies, improves system stability, significantly increases transmission efficiency, and solves the problem of code rate reduction caused by excessive symbol length.

[0040] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit the invention. Attached Figure Description

[0041] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention. It is obvious that the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0042] Figure 1 It is a magnetic pulse signal generator;

[0043] Figure 2 It is a magnetic pulse modulated waveform;

[0044] Figure 3 The waveforms and magnified views of code elements 0 and 1 are shown.

[0045] Figure 4 The normalized spectrum of symbol 0;

[0046] Figure 5 The normalized spectrum of code symbol 1;

[0047] Figure 6 For the coding implementation process;

[0048] Figure 7 The autocorrelation and cross-correlation curves for code 0 and code 1 are shown.

[0049] Figure 8 The cross-correlation curves between symbol 0 and symbol 1 and the collected data;

[0050] Figure 9 The characteristic curves of the number of periods or code rate versus the correlation peak;

[0051] Figure 10 This is a flowchart of the method of the present invention. Detailed Implementation

[0052] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, they are provided so that the invention will be more comprehensive and complete, and will fully convey the concept of the exemplary embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0053] Furthermore, the accompanying drawings are merely illustrative of the invention and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore repeated descriptions of them will be omitted. Some block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities. These functional entities can be implemented in software, in one or more hardware modules or integrated circuits, or in different network and / or processor devices and / or microcontroller devices.

[0054] To address the shortcomings and deficiencies of existing technologies, this invention proposes a novel hardware topology for a ground-penetrating transmission system. This topology can efficiently radiate magnetic pulse signals on a small physical hardware platform, and the receiving device achieves communication by inducing the magnetic pulse signal. Furthermore, this invention proposes a random timing modulation and demodulation method tailored to the characteristics of the magnetic pulse signal in this topology, provides steps for designing information symbols for high-efficiency pulses, and methods for analyzing symbol correlation and boundary conditions. This resolves the contradiction between radiation efficiency and signal bandwidth that is difficult to balance in existing ground-penetrating systems and modulation / demodulation methods.

[0055] First, a hardware topology for generating magnetic pulse signals is proposed, and based on this topology, an information loading modulation and demodulation system is invented. The hardware topology of the magnetic pulse signal transmitter is as follows: Figure 1 As shown, the LC resonant system consists of a first control switch K1, a second control switch K2, a unidirectional conduction switch Q1, a resonant capacitor C, and a solenoid L. By controlling the switching devices (K1, K2) and the switching transistor (Q1) through a modulation strategy, the operating cycle of the LC resonant system is divided into four stages: initial energy storage, alternating energy transfer between the capacitor and inductor, energy recovery, and information loading window. The entire control strategy dynamically adjusts the duration of each stage based on real-time feedback of the excitation current state and bandwidth requirements, thereby achieving dynamic expansion of channel capacity and precise control of bandwidth while maintaining a high Q-value resonant state.

[0056] This invention also proposes a modulation mechanism with orthogonal information, based on a magnetic pulse signal generator to generate information symbol waveforms. The invention provides the design steps for symbol 0 and symbol 1 waveforms and proposes a method for analyzing the orthogonality of the symbol waveforms.

[0057] Assume the period of the magnetic pulse signal generated by the magnetic pulse signal generator is T0, and the interval between adjacent complete cycles of the sinusoidal signal is τ. i (i = 1, 2, 3…), here we assume that the number of pulses for both code element 1 and code element 0 is N. The waveform of code element 0 consists of several magnetic pulses and τ. i The signal consisting of (i = 1, 2, 3...) represents a phase shift of symbol 0 for symbol 1. Signals formed over time.

[0058] The specific design steps are as follows:

[0059] Step 1: Generate symbol 0: The waveform of symbol 0 consists of N magnetic pulse signals, each with a period of T0; the interval Δt between adjacent magnetic pulse signals is adjusted by precisely controlling the charging time window to ensure that the waveform of symbol 0 is continuous and complete in the time domain.

[0060] Step 2: Generating Symbol 1: The waveform of symbol 1 is generated by phase shifting the waveform of symbol 0. The phase shift time is...

[0061] Step 3: Verify the correlation between code elements 0 and 1, including the autocorrelation and cross-correlation of code elements 0 and 1: Calculate the autocorrelation function and cross-correlation function of code elements 0 and 1 and draw the correlation graph. If the autocorrelation peak is significant and the cross-correlation peak is close to zero, it means that code elements 0 and 1 are orthogonal; otherwise, return to step 1.

[0062] like Figure 3The left half of the diagram shows the waveforms of code elements 0 and 1, while the right half shows a magnified view of code elements 0 and 1. The magnified view further proves that code elements 0 and 1 are orthogonal.

[0063] The methods for verifying the autocorrelation and cross-correlation of code element 0 and code element 1 are as follows:

[0064] Assuming the data of the symbol 1 waveform is sequence a, and the data of the symbol 0 waveform is sequence b, then

[0065] a = {a1, a2, a3, a4, ..., a} n}

[0066] b = {b1, b2, b3, b4, ..., b} n}

[0067] The autocorrelation function of symbol 1 is

[0068]

[0069] The autocorrelation function of symbol 1 is

[0070]

[0071] The cross-correlation function of code 1 and code 0 is:

[0072]

[0073] The cross-correlation function of code 0 and code 1 is

[0074]

[0075] by Figure 3 Taking data as an example, the autocorrelation and cross-correlation analysis of code elements 0 and 1 is shown below:

[0076] If the autocorrelation peaks of symbols 0 and 1 are significant and the sidelobes are low, while the cross-correlation peaks of symbols 0 and 1 are close to zero, it indicates that the autocorrelation between symbols 0 and 1 is very high, the cross-correlation between symbols 0 and 1 is very low, and their orthogonality is good. According to this modulation mechanism, the probability of mutual interference between the symbol signals 0 and 1 radiated by the magnetic pulse signal transmitter is low.

[0077] The demodulation mechanism of this invention demodulates the symbol waveform based on the cross-correlation between the input signal and symbol 0 and symbol 1. Through the modulation method proposed in this invention, symbol 0 and symbol 1 maintain orthogonality during transmission, thus ensuring that they do not interfere with each other. During demodulation, the receiving end determines the information type by calculating the cross-correlation between the input signal and symbol 0 and symbol 1: if the correlation between the input signal and symbol 0 is high, it is decoded as 0; if the correlation between the input signal and symbol 1 is high, it is decoded as 1. This demodulation mechanism based on orthogonality and correlation significantly improves the accuracy of signal transmission and its anti-interference capability.

[0078] The specific steps of the demodulation process are as follows:

[0079] Step 1: Initialize the signal buffer and define the calculation window data length, which is usually consistent with the length M of the symbol waveform. Define the variables corr0 and corr1 to store the cross-correlation calculation results between the input signal and symbol 0 and symbol 1.

[0080] Step 2: Read data sequentially from the input signal, reading one point at a time and updating the input signal buffer;

[0081] The third step is to calculate the cross-correlation between the input signal window and code 0 and code 1 according to formulas (1) and (2) for each sliding window position, and record the values ​​of corr0 and corr1.

[0082] Step 4: Determine the symbol type: Compare the values ​​of corr0 and corr1 in the current window. If corr0 > corr1, decode as 0; otherwise, decode as 1. Output the decoding result, clear the relevant value variables, and prepare to process the next window.

[0083] Step 4: Loop processing: Repeat steps 2 and 3 until all input signals have been processed.

[0084] The orthogonality of symbol 0 and symbol 1 plays a crucial role in spread spectrum communication: by multiplying the information signal with orthogonal symbols, the signal's spectrum is expanded, thereby improving anti-interference capability and concealment. Figure 4 and Figure 5 In the diagram, the spectrum of symbol 1 exhibits a peak at the center frequency f0, while the spectrum of symbol 0 is orthogonal to that of symbol 1 due to a half-cycle phase shift. By superimposing symbol 0 and symbol 1, the spectrum is significantly expanded.

[0085] In practical engineering, LC resonant systems, as damped oscillation systems, experience a gradual attenuation of their radiated signal strength over time. This leads to reduced communication distance, decreased signal quality, and reduced transmission reliability, impacting system stability and practicality. To overcome this problem, a charging mechanism must be introduced to periodically replenish energy and maintain signal strength. However, the choice of charging environment is crucial: capacitors (C) can be stably charged by an external power source, effectively replenishing energy; while inductors (L) release electric arcs during charging, causing energy loss and posing safety hazards, thus making them unsuitable as charging environments.

[0086] Based on the above analysis, a capacitor becomes the only feasible option. However, its charging time directly affects the stability of the pulse signal strength: too short a charging time results in insufficient energy replenishment; too long a time prolongs the system cycle and reduces communication efficiency. Therefore, it is essential to accurately analyze the capacitor charging time, determine a reasonable charging boundary, and ensure both energy replenishment and system efficiency and safety, thereby ensuring the stable operation of the communication system.

[0087] In the design of symbol 1 and symbol 0, the interval time τ i If the time interval (i = 1, 2, 3...) is too short, it will lead to insufficient capacitor charging, thus affecting the normal operation of the transmission system. By introducing a charging time boundary, it is ensured that τ... i (i = 1, 2, 3...) is greater than the minimum charging time τ of the capacitor. min ,Right now

[0088] τ i >τ min (5)

[0089] Assume the capacitor is C, the inductor is L, and the input voltage is U. in The equivalent resistance of the circuit is R.

[0090] Capacitor voltage U C (t) changes over time:

[0091]

[0092] Then the charging current i C (t) is:

[0093]

[0094] Charging time τ min It is the capacitor voltage U C (t) rises from an initial value (assumed to be 0) to a certain threshold of 0.99U in The required time,

[0095]

[0096] Simplifying, we get:

[0097] τ min =-RCln(0.01)≈4.6052RC (9)

[0098] From formula (9), we know that: τ i (i = 1, 2, 3...) depends on the system hardware, namely the system internal resistance R and the capacitor component C, whose values ​​serve as the lower limit of the random distribution in the encoding.

[0099] Assume the symbol contains N sine wave cycles, and the time interval between each sine wave cycle is τ. max Therefore, the symbol length τ max for

[0100]

[0101] The rate R is defined as the number of symbols transmitted per second, and its formula is:

[0102]

[0103] To maintain a high code rate, the symbol length T needs to be limited. code The upper limit of this requires setting an upper limit τ for the random interval. max .

[0104] Assume the minimum code rate required by the system is R. min Then the upper limit of the symbol length is

[0105]

[0106] From formula (10) we get

[0107] N·(T0+τ max )≤T code,max (13)

[0108] Solving

[0109]

[0110] From the above, we can see that: τ i The maximum value of (i = 1, 2, 3...) depends on the code rate, the period of the sinusoidal signal, and the number of periods; its value serves as the upper limit of the random distribution in the encoding.

[0111] In summary, τ i The range of values ​​for (i = 1, 2, 3...) is:

[0112]

[0113] The present invention will now be described in more detail with reference to the accompanying drawings and specific embodiments.

[0114] Example 1

[0115] Taking a resonant system with a center frequency f0 = 200Hz, number of periods N = 40 as an example, C = 0.636μF, inductance L = 1H, R in =100Ω, and assume the system requires a code rate R>=1bps.

[0116] but

[0117]

[0118] Substituting into formulas (9) and (14), we get:

[0119] τ min =-RCln(0.01)≈4.6052RC≈0.292ms

[0120]

[0121] Right now

[0122] 0.292ms≤τ i ≤20ms

[0123] Encoding process of code element 0 and code element 1: Randomly generate 40 τ i (i=1,2,3...) at 0.292ms≤τ i Between ≤29.31ms, symbol 1 was formed, during the shift phase. We can obtain the code element 0. For example... Figure 6 As shown, the comparison verified that code element 0 and code element 1 are orthogonal.

[0124] Based on the orthogonality of symbol 0 and symbol 1, the signal spectrum is expanded, achieving bandwidth gain.

[0125] Next, we verify the autocorrelation and cross-correlation of code element 0 and code element 1, and obtain... Figure 7 The curve shown is based on Figure 7 The display shows that the autocorrelation curves of code symbols 1 and 0 have significant peaks, indicating strong autocorrelation; while the cross-correlation curves of code symbols 0 and 1 fluctuate around 0, indicating weak cross-correlation. Therefore, this encoding / decoding system has strong anti-interference capabilities.

[0126] Figure 8 The relationship between the number of periods and the correlation peaks of symbol 0 / symbol 1 and the input signal.

[0127] By changing the number of periods, i.e. the symbol length, and calculating the cross-correlation peaks between symbol 0 and symbol 1 and the acquired signal, i.e. the correlation peaks, we can obtain... Figure 9 The curve shown.

[0128] from Figure 9As can be seen from this, the number of cycles is directly proportional to the peak value of the correlation domain, and the code rate is inversely proportional to the peak value of the correlation domain. Therefore, it is necessary to find the optimal balance point between the code rate and the correlation peak value, that is, the intersection of the two curves. When N=40, the system achieves the optimal balance between the code rate and the correlation peak, which not only achieves high transmission efficiency, but also ensures the reliability of signal detection.

[0129] Furthermore, the above figures are merely illustrative of the processes included in the method according to exemplary embodiments of the present invention, and are not intended to be limiting. It is readily understood that the processes shown in the above figures do not indicate or limit the temporal order of these processes. Additionally, it is readily understood that these processes may be executed synchronously or asynchronously, for example, in multiple modules.

[0130] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention herein. This application is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. The specification and embodiments are to be considered exemplary only, and the true scope and spirit of the invention are indicated by the claims.

[0131] It should be understood that the present invention is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is defined only by the appended claims.

Claims

1. A carrier information modulation and demodulation method for a controllable resonant magnetic pulse ground-penetrating communication transmitter, characterized in that, The method includes: A magnetic pulse signal is generated through a hardware topology of a magnetic pulse signal transmitter, the hardware topology including a first control switch K1 and a second control switch K2, a unidirectional conduction switch Q1, a resonant capacitor C, and a solenoid L; By controlling the on and off states of the first control switch K1, the second control switch K2, and the unidirectional conduction switch Q1, the working cycle of the LC resonant system is divided into four stages: initial energy storage, alternating energy transfer between the capacitor and the inductor, energy recovery, and information loading window. The entire control strategy dynamically adjusts the duration of each stage based on the real-time feedback of the excitation current status and bandwidth requirements through an algorithm. Discontinuous magnetic resonance signal pulses are generated by dynamically adjusting the duration of each stage; An information modulation mechanism is designed based on orthogonal symbols to generate waveforms of symbol 0 and symbol 1, and orthogonality is ensured by verifying their autocorrelation and cross-correlation. At the receiving end, information demodulation is achieved by calculating the cross-correlation between the input discontinuous magnetic resonance signal and symbol 0 and symbol 1.

2. The method according to claim 1, characterized in that, The LC resonant system's operating cycle is divided into four stages by controlling the on / off states of the first control switch K1, the second control switch K2, and the unidirectional conduction switch Q1. Specifically: First stage: The first controllable switch K1 is turned on and the second controllable switch K2 is turned off. The input voltage charges the resonant capacitor and the excitation current is zero. Second stage: The first controllable switch K1 is turned off and the second controllable switch K2 is turned on. The excitation current flows from the resonant capacitor to the resonant inductor, and energy is transferred from the capacitor to the inductor. Third stage: When both the first controllable switch K1 and the second controllable switch K2 are turned off, the excitation current is fed back from the resonant inductor to the resonant capacitor and flows through the unidirectional conducting element Q1 to form a circuit. Fourth stage: The first controllable switch K1 and the second controllable switch K2 remain off, the unidirectional conducting element Q1 is cut off, completing one resonance cycle and forming a time window for information loading.

3. The method according to claim 1, characterized in that, The waveform of code element 0 consists of N magnetic pulse signals, each magnetic pulse signal having a period of... The interval between adjacent magnetic pulse signals is Δt; the waveform of code element 1 is generated by phase shifting the waveform of code element 0, and the phase shift time is... ,in, The interval between two consecutive complete sinusoidal signals is the time interval between each other.

4. The method according to claim 3, characterized in that, The orthogonality of the verification code 0 and code 1 includes: Calculate the autocorrelation and cross-correlation functions of code symbol 0 and code symbol 1; If the autocorrelation peak is significant and the cross-correlation peak is close to zero, then code symbol 0 and code symbol 1 are determined to be orthogonal.

5. The method according to claim 1, characterized in that, The specific steps of the information demodulation include: Initialize the signal buffer and define the length of the calculation window; Read data sequentially from the input signal and update the buffer; Calculate the cross-correlation between the input signal window and symbol 0 and symbol 1; Compare the cross-correlation values ​​and decode them as 0 or 1; The process continues until all input signals have been processed.

6. The method according to claim 3, characterized in that, The interval time The following boundary conditions must be met: The minimum value is greater than the minimum charging time of the capacitor. ,Right now ; The maximum value is determined by the minimum code rate required by the system. Decision, that is , where N is the number of sine wave periods.

7. The method according to claim 6, characterized in that, The minimum charging time of the capacitor Calculated using the following formula: The capacitor voltage rises from its initial value to 0.

99. The required time, of which Capacitor voltage .

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