Aero-electromagnetic composite stacked time-frequency pulse emission system and control method thereof

Abstract

This invention discloses an airborne electromagnetic composite superposition time-frequency pulse transmission system and its control method, belonging to the field of geophysical electromagnetic detection technology. The system includes: a dual-power supply switching circuit for providing low voltage (UL) and high voltage (UH); a full-bridge inverter circuit for converting DC voltage into a bipolar trapezoidal wave main pulse; an active clamping circuit for actively injecting energy to accelerate current establishment during the current rise phase and absorbing inductive load energy and clamping voltage spikes during the current fall phase; a control module for generating timing control signals; and a detection module for real-time acquisition of current and voltage and feedback to the control module. In terms of the control method, through parameter analysis calculation and timing partitioning, a high-frequency square wave is superimposed within the safe window of the flat-top segment of the time-domain main pulse, achieving rapid waveform establishment, stable superposition, and rapid shutdown. Time-domain detection and frequency-domain excitation are completed simultaneously within a single transmission cycle, effectively improving the information density and operational efficiency of airborne electromagnetic detection.

Description

Technical Field

[0001] This invention belongs to the field of geophysical electromagnetic detection technology, specifically relating to an airborne electromagnetic composite superposition time-frequency pulse transmission system and its control method. Background Technology

[0002] Electromagnetic exploration, with its highly sensitive response to differences in the electrical properties of subsurface media, has become one of the core geophysical methods for resource exploration and geological surveys. When this method is moved from ground-based platforms to airborne vehicles, its significant advantages of high efficiency, mobility, and independence from complex terrain make it a cutting-edge development direction in the field of exploration geophysics.

[0003] In the field of airborne electromagnetic detection, time-domain electromagnetic methods and frequency-domain electromagnetic methods constitute two fundamental technical approaches. Time-domain electromagnetic methods, by observing the transient response of the secondary field decaying over time after the transmit current is turned off, exhibit high sensitivity to low-resistivity anomalies and are suitable for detecting targets in the middle and deep layers. Frequency-domain electromagnetic methods, by transmitting continuous excitation signals of different frequencies and measuring the steady-state electromagnetic response, have unique advantages in characterizing fine structures and electrical stratification in shallow layers. However, due to fundamental differences in excitation field mechanisms and receiver response methods, a single method cannot independently complete full-scale electrical imaging of underground space from the surface to depth, resulting in inherent detection blind spots that limit the density of detection information and the accuracy of geological interpretation. Therefore, academia and industry are committed to exploring an integrated detection mode combining time-domain and frequency-domain electromagnetic methods, aiming to integrate the advantages of both and achieve wide-bandwidth, high-efficiency electromagnetic detection.

[0004] Several time-frequency electromagnetic detection schemes have been developed in existing technologies. One typical mode divides the working area into near-source and far-source regions based on the transmission and reception distance: in the near-source region, the time-domain electromagnetic method is used to acquire transient attenuated signals, while in the far-source region, the frequency-domain electromagnetic method is switched to transmit multi-frequency signals to obtain deep electrical information. Furthermore, it proposes a combined waveform that sequentially arranges the frequency-domain multi-frequency excitation segment and the time-domain shutdown observation segment within a single transmission cycle. Another technical scheme uses a ground-based high-power constant-current square wave transmission system to transmit square wave waveforms that do not cross zero. The receiving end converts the time-domain recorded data into frequency-domain data through Fourier transform, achieving joint inversion and processing of dual-domain data.

[0005] While the existing solutions formally combine the time and frequency domains, they are essentially time-division or spatially partitioned operating modes. The time and frequency components of the transmitted waveform are independent and sequentially arranged in the transmission sequence, failing to achieve true synchronous excitation of the two signals in the time domain. This time-division operating mode results in limited information density acquired in a single flight, and data splicing errors are prone to occur in mode switching areas, affecting the continuity and reliability of the inversion results. Furthermore, existing solutions are mostly based on high-power ground-based transmission platforms, resulting in large and heavy transmission systems, complex site deployment, and long preparation times, failing to fully leverage the inherent advantages of rapid and flexible deployment of airborne platforms.

[0006] Furthermore, the load of the airborne electromagnetic launch system is an inductive transmitting coil, and the current change is constrained by electromagnetic inertia, making it difficult to achieve high-quality superposition of high-frequency components in the flat-top segment of the main pulse in the time domain, and also difficult to achieve a balance between steep edges and flat-top stability. How to maintain the rapid establishment and shutdown of the current pulse while forming a stable and controllable high-frequency excitation component in the flat-top segment has become a technical problem that urgently needs to be solved in integrated time-frequency airborne electromagnetic detection. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides an airborne electromagnetic composite superposition time-frequency pulse transmission system and its control method. By synchronously combining the time-domain bipolar trapezoidal wave main pulse with a high-frequency square wave superimposed on its flat-top segment within a single transmission cycle, and by utilizing dual power supply switching and active clamping segmented collaborative control to overcome the inertia of inductive load current, simultaneous transmission of time-frequency domain signals is achieved.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] An airborne electromagnetic superposition time-frequency pulse transmission system includes:

[0010] The dual power supply switching module has its input terminals connected to a high-voltage DC power supply and a low-voltage DC power supply respectively, and its output terminal connected to the input terminal of the full-bridge inverter circuit module, which is used to switch the output of high-voltage DC power or low-voltage DC power as needed.

[0011] The full-bridge inverter circuit module has its input terminal connected to the output terminal of the dual power supply switching module, and its two output terminals are connected across the transmitting load to invert the input DC voltage into a bipolar trapezoidal wave main pulse.

[0012] An active clamping circuit and a high-voltage source module are connected in parallel to the two output terminals of the full-bridge inverter circuit module. They are used to actively inject energy during the current rise phase to accelerate current build-up, and to absorb inductive load energy and clamp voltage spikes during the current fall phase.

[0013] The control module has a first signal output terminal connected to the control electrode of each switching transistor in the full-bridge inverter circuit module to output a full-bridge inverter drive signal, a second signal output terminal connected to the control electrode of each switching transistor in the dual power supply switching module to output a high-low voltage switching control signal, and a third signal output terminal connected to the control electrode of the clamping switching transistor in the active clamping circuit and high-voltage source module to output a clamping intervention control signal.

[0014] The detection module has its sampling end connected to the current loop of the transmitting load and its signal output end connected to the feedback input end of the control module, which is used to collect the transmitting current and voltage in real time and feed them back to the control module.

[0015] The control module dynamically corrects the timing parameters of each control signal based on the current and voltage data fed back by the detection module, so that the flat-top segment of the bipolar trapezoidal wave main pulse is superimposed with a high-frequency square wave to form a time-frequency composite pulse.

[0016] Furthermore, the dual power supply switching module includes a first high-voltage switch, a second low-voltage switch, a first isolation diode, a second isolation diode, and a third isolation diode; the first high-voltage switch and the second isolation diode are connected in series to form a high-voltage branch, the second low-voltage switch and the third isolation diode are connected in series to form a low-voltage branch, the high-voltage branch and the low-voltage branch are connected in parallel and then connected in series with the first isolation diode, and the control terminals of the first high-voltage switch and the second low-voltage switch are respectively connected to the control module.

[0017] Furthermore, the full-bridge inverter circuit module includes a first switch, a second switch, a third switch, and a fourth switch. The source of the first switch is connected to the drain of the third switch, the source of the second switch is connected to the drain of the fourth switch, the drains of the first switch and the second switch are connected together to the positive output terminal of the dual power supply switching module, and the sources of the third switch and the fourth switch are connected together to the negative output terminal of the dual power supply switching module. The connection node between the first switch and the third switch, and the connection node between the second switch and the fourth switch serve as two output terminals bridging the transmitting load.

[0018] Furthermore, the active clamping circuit and high-voltage source module include a clamping switch, an energy storage capacitor, a power diode, a bleeder resistor, and an adjustable clamping power supply; the adjustable clamping power supply is connected in series with the power diode and then connected to the energy storage capacitor; the bleeder resistor is connected in parallel across the energy storage capacitor; one end of the energy storage capacitor is connected to the drain of the clamping switch, and the other end is grounded; the source of the clamping switch is connected to the positive output terminal of the full-bridge inverter circuit module.

[0019] Furthermore, the control module includes an MCU and an FPGA. The FPGA generates multiple timing control signals according to configuration parameters. The timing control signals include the alternating conduction signals of the diagonal switches of the full-bridge inverter circuit module, the high-low voltage switching signals of the dual power supply switching module, and the clamping intervention signals of the active clamping circuit and the high-voltage source module. The MCU and the FPGA communicate bidirectionally to transmit operating parameters and operating status.

[0020] Furthermore, the detection module includes a Hall current sensor and a high-speed analog-to-digital converter. The Hall current sensor is connected in series in the current loop of the transmitting load. The sampling rate of the high-speed analog-to-digital converter is not less than 1MHz. The detection module uploads the real-time sampled current data and voltage data to the control module. The control module dynamically corrects the clamping voltage amplitude, dead time, and switching point parameters based on the deviation between the measured waveform and the preset indicators.

[0021] Furthermore, the transmitting load includes a transmitting coil and a damping matching circuit. The damping matching circuit is connected in parallel across the transmitting coil to match the inductive impedance of the transmitting coil and absorb the residual oscillation energy of the falling edge of the pulse.

[0022] On the other hand, the present invention provides a control method applied to the aforementioned airborne electromagnetic composite superposition time-frequency pulse transmission system, comprising:

[0023] Step 1: Preset the main pulse parameters of the bipolar trapezoidal wave and the high-frequency square wave parameters, and record the load resistance and load inductance. Calculate the rising edge start clamping time, high-frequency superposition clamping time and synchronous turn-off time according to the full response formula of the first-order circuit.

[0024] Step 2: Output the full-bridge inverter drive signal to control the power switching transistors to conduct alternately, generating a bipolar trapezoidal main pulse;

[0025] Step 3: Using the preset pre-dead time and post-dead time as boundaries, within the safety window of the flat-top segment of the bipolar trapezoidal wave main pulse, the dual power supply switching module switches between low-voltage DC and high-voltage DC to superimpose a high-frequency square wave. During the current rising phase, the clamping switch is turned on to continue the clamping duration at the rising edge. When switching to high-voltage DC, the clamping switch is turned on again to continue the high-frequency superimposed clamping duration. When the main pulse is turned off, the full-bridge power circuit is simultaneously cut off and clamping energy discharge is initiated.

[0026] Step 4: Collect the transmission current data in real time, and dynamically fine-tune the control parameters based on the flatness of the measured waveform and the amplitude of the high-frequency spectrum.

[0027] Step 5: Lock the operation with the optimized parameters and continuously output time-frequency composite pulses.

[0028] Furthermore, the rising edge start clamping duration is determined by multiplying the time constant of the load resistance and load inductance by a first natural logarithm ratio, where the first natural logarithm ratio is the natural logarithm of the ratio of the clamping voltage to the difference between the clamping voltage and the low voltage; the high-frequency superposition clamping duration is determined by multiplying the time constant by a second natural logarithm ratio, where the second natural logarithm ratio is the natural logarithm of the ratio of the difference between the clamping voltage and the low voltage to the difference between the clamping voltage and the high voltage; the synchronous turn-off duration is determined by multiplying the time constant by a third natural logarithm ratio, where the third natural logarithm ratio is the natural logarithm of the ratio of the sum of the high voltage and the clamping voltage to the sum of the low voltage and the clamping voltage.

[0029] Furthermore, in step 4, when the current ripple coefficient of the flat-top segment exceeds a preset threshold, the clamping voltage is finely adjusted or the pre-dead time and the post-dead time are adjusted; when the spectral amplitude of the high-frequency superposition segment at the target frequency is lower than a preset value, the high-voltage power supply voltage is increased or the dead time is shortened; when the falling edge time exceeds the expected value, the clamping voltage is increased or the programming coefficient of the synchronous turn-off duration is extended; after iteration to ensure that all indicators meet the standards, the optimal parameter set is solidified into the control module.

[0030] Thirdly, the present invention provides an electronic device, comprising: one or more processors; a memory for storing one or more programs; wherein, when the one or more programs are executed by the one or more processors, the one or more processors implement the aforementioned control method.

[0031] Fourthly, the present invention provides a computer-readable storage medium having executable instructions stored thereon, which, when executed by a processor, enable the processor to implement the aforementioned control method.

[0032] The beneficial effects of this invention are as follows:

[0033] The invention achieves true synchronous transmission of time-frequency domain signals, enhancing information density and detection efficiency: Existing time-frequency electromagnetic schemes employ time-domain and frequency-domain time-division or zone-division operating modes, essentially a sequential arrangement of two methods. This results in limited information per measurement, and mode switching easily introduces data splicing errors. This invention, by synchronously superimposing a high-frequency square wave within the flat-top segment of the time-domain bipolar trapezoidal wave main pulse, enables continuous output of the frequency-domain excitation signal during the duration of the time-domain pulse. Without time-division switching, a single transmission can simultaneously acquire the time-domain attenuation response reflecting deep-seated information and the frequency-domain spectral information reflecting shallow structures, significantly improving the detection efficiency and information density of a single flight. The continuity and reliability of the inversion results are also effectively enhanced.

[0034] Expanding the functionality of active clamping circuits to achieve accurate synthesis of composite waveforms under inductive loads: Traditional active clamping circuits are only used for voltage spike suppression and stray energy recovery during switch-off, limiting their function to device protection. This invention reconstructs the active clamping function, upgrading it from a passive protection unit to an active current dynamic regulation core unit: actively engaging a high-voltage clamping circuit during the current rise phase to accelerate current ramp-up; forcing the current to quickly follow the target value during voltage switching in the flat-top phase; and simultaneously completing energy dissipation and rapid current drop during the turn-off phase. Combined with a three-stage clamping duration quantitative calculation formula, this overcomes the technical bottleneck of rapid current step transitions under large inductive loads, making high-fidelity output of composite waveforms possible.

[0035] Quantitative parameter design combined with closed-loop adaptive optimization ensures waveform quality and engineering adaptability: This invention derives analytical calculation formulas for rising edge start-up clamping duration, high-frequency superposition clamping duration, and synchronous turn-off duration based on the full response of RL circuits, providing a theoretical basis for parameter setting and avoiding waveform distortion caused by traditional trial-and-error methods. Simultaneously, the transmitter current is acquired in real time by a Hall sensor and a high-speed ADC, and the FPGA's built-in closed-loop algorithm dynamically fine-tunes the dead time, clamping voltage, and high-voltage amplitude, achieving parameter self-optimization and solidification. This ensures that the system can stably output high-quality composite pulses that meet preset specifications under different load conditions and flight environments.

[0036] The system is lightweight and adaptable to rapid deployment on airborne platforms: This invention does not require a high-power ground-based transmitting device. All circuits are integrated into the airborne platform, making it small in size and light in weight. It can be quickly transferred and flexibly deployed, making it suitable for efficient electromagnetic detection operations under complex terrain conditions. Attached Figure Description

[0037] Figure 1 This is a block diagram of the airborne electromagnetic composite superposition time-frequency pulse transmission system of the present invention;

[0038] Figure 2 This is a circuit topology diagram of the aviation electromagnetic composite superposition time-frequency pulse transmission system of the present invention;

[0039] Figure 3 This is a flowchart of the control logic of the aviation electromagnetic composite superposition time-frequency pulse transmission system of the present invention;

[0040] Figure 4 This is a schematic diagram of the control signal timing and transmission waveform of the composite time-frequency pulse of the present invention;

[0041] Figure 5 The Simulink simulation diagram shows the composite pulse output voltage and current of this invention. Detailed Implementation

[0042] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0043] This invention proposes an airborne electromagnetic composite superposition time-frequency pulse transmission system and a precise time-frequency pulse control method. It outputs a composite pulse consisting of a time-domain bipolar trapezoidal main pulse and a high-frequency square wave superimposed within a single transmission cycle. Through active clamping and dual-power supply switching coordinated control, when the circuit switches voltage and the current changes towards a steady-state value, active clamping technology is used to quickly bring it to the target value. Unlike traditional active constant-voltage clamping technology, which typically intervenes during voltage switching to suppress voltage spikes, recover stray inductance energy, and protect devices, this solution reconstructs the active clamping function. During the current rise phase, a high-voltage clamping circuit is actively engaged, leveraging the large voltage difference to increase the current change rate and accelerate the current climb to a steady-state value. During the current fall phase, the main power switch is turned off, and the active clamping circuit automatically completes the inductive load energy discharge and voltage clamping, simultaneously achieving a rapid current drop. This approach expands the functionality of traditional clamping circuits, upgrading active clamping from a voltage protection unit to a core unit for dynamic current regulation. Combined with dual power supply switching logic, it addresses both the requirements of voltage clamping protection and rapid current step change, adapting to the requirements of aviation electromagnetic composite superposition time-frequency pulse transmission systems for pulse edge, current accuracy, and response speed.

[0044] The core concept of this invention lies in: designing an active clamping circuit to actively excite and clamp the rising and falling edges of the current in the full-bridge inverter circuit, thereby achieving rapid current build-up and rapid turn-off; designing a dual-power supply switching circuit to provide seamless switching between high-voltage and low-voltage power supplies for composite waveforms, meeting the different voltage requirements of the flat-top segment and the high-frequency superposition segment in the time domain; calculating key circuit parameters (such as clamping turn-on time, dual-power supply voltage, dead time, etc.) to preset the shape of the target waveform; precisely controlling the driving timing of the fast-turn-off MOSFET to ensure stable output coordinated by the full-bridge inverter, dual-power supply switching, and clamping circuit; accurately detecting the emitter current and voltage and feeding them back to the control module to provide real-time data for closed-loop regulation; and dynamically adjusting the control parameters based on the feedback emitter current and clamping current waveforms to ensure that the output current waveform meets the preset indicators.

[0045] Combination Figure 1 and Figure 2 As shown, a block diagram and main circuit topology of an airborne electromagnetic composite superposition time-frequency pulse transmission system are presented. The system includes:

[0046] The power management module internally includes a DC input unit, a DC / DC analog circuit power supply unit, a DC / DC digital circuit power supply unit, and a DC / DC power circuit power supply unit. The DC input unit serves as the overall power supply input, connecting to the DC bus voltage output from the onboard lithium battery. After passing through protection and filtering circuits, the voltage is distributed to the three subordinate DC / DC conversion units. Each unit employs electrical isolation design to physically block crosstalk interference from large current ripples in the power circuit to the control and sampling circuits. The DC / DC analog circuit power supply unit outputs a high-precision, low-ripple analog supply voltage, providing a stable operating power supply for the voltage and current sampling modules and the analog conditioning circuit of the clamping circuit, ensuring the accuracy of current and voltage sampling and the stability of the clamping control reference. The DC / DC digital circuit power supply unit outputs multiple digital logic supply voltages, providing core operating power for the control module and peripheral modules, while also providing isolated control-side power supply for the power transistor drive circuit. The DC / DC power circuit power supply unit outputs a power-stage DC voltage, providing power energy for the dual-power switching module, active clamping, and high-voltage source. The power management module has built-in surge suppression, overcurrent protection, and reverse connection protection circuits, which can withstand power fluctuations and complex electromagnetic interference on the aviation platform and ensure the long-term safe and stable operation of each power supply branch.

[0047] The dual power supply switching module is used to connect the high-voltage DC and low-voltage DC outputs from the corresponding units of the DC / DC power circuit in the power management module. It can switch the output of high-voltage DC or low-voltage DC as needed to power the subsequent full-bridge inverter circuit module. The dual power supply switching module includes two MOSFET switches and three isolation diodes. The two MOSFET switches act as voltage switching actuators, outputting high and low voltages in a time-division manner, enabling the full-bridge inverter circuit module to generate differentiated voltage waveforms containing a flat-top segment of the time-domain main pulse and a high-frequency superposition segment. The three isolation diodes work together to achieve dual protection functions of reverse voltage protection and overcurrent suppression, effectively suppressing transient impacts during switching and ensuring smooth and reliable operation during high-low voltage switching.

[0048] The full-bridge inverter circuit module mainly consists of four MOSFET power switches. It receives the DC voltage output from the front-end dual power supply switching module, converts the DC voltage into the voltage required for the composite superimposed time-frequency pulse, and then supplies it to the transmitting load to form the actual required composite superimposed time-frequency pulse current, which in turn generates the field source of the primary field required for detection.

[0049] The control module is composed of an MCU and an FPGA, powered by the DC / DC digital circuit power supply unit within the power management module. The MCU interacts with the peripheral module to complete human-machine instruction parsing and peripheral unit control, and communicates bidirectionally with the FPGA to send working parameters and read back the system operating status. The FPGA generates multiple high-precision digital timing control signals according to the configuration parameters and outputs them to the MOSFET driver, coordinating the timing logic scheduling: planning the working timing of the full-bridge inverter to generate a bipolar trapezoidal wave main pulse, and synchronously outputting timing instructions within the safe timing window of the trapezoidal wave flat-top segment to control the dual power supply switching module to complete high-low voltage switching and schedule the working timing of the active clamping circuit, so that the transmitting load obtains a time-frequency composite pulse superimposed with a high-frequency square wave.

[0050] The MOSFET driver module receives digital timing signals output from the FPGA, converts the weak digital signals into dedicated drive voltages for high-power MOSFETs, and synchronously drives the dual power switching transistors, full-bridge inverter power transistors, and active clamping switching transistors. It precisely controls the turn-on and turn-off times of each power switch, ensuring that the pulse timing strictly matches the designed waveform.

[0051] An active clamping circuit and a high-voltage source module are connected in parallel to the circuit of the full-bridge inverter circuit module. The circuit includes a clamping switch, an energy storage capacitor, and an adjustable clamping power supply. When the current in the clamping switch rises, it is actively turned on to accelerate the establishment of the current in the coil. When the full-bridge inverter switch is turned off, that is, during the process of current decline, it absorbs the inductive energy stored in the transmitting load and clamps the voltage spike, thereby realizing the rapid linear rise and fall of the current waveform.

[0052] The voltage and current detection module collects the voltage and current of the transmitting load, active clamping circuit, and high-voltage source module in real time, and uploads the sampled data to the FPGA control terminal to form a closed-loop feedback of the power circuit. The system dynamically adjusts the supply voltage, inverter timing, clamping amplitude and duration based on the real-time acquired data to achieve adaptive waveform control.

[0053] The peripheral module includes indicator lights, a touch screen, a fan, an SD card storage module, and a GPS module. This module establishes a two-way interactive link with the control module. The peripheral module receives control signals output by the control module to realize status indication and heat dissipation regulation. At the same time, it uploads touch screen human-machine operation instructions, stored data, and GPS information to the control module to jointly complete the functions of human-machine interaction, system status indication, heat dissipation management, operation data recording, and location information acquisition.

[0054] The transmitting load includes a transmitting coil and a damping matching circuit, which are connected to the output circuit of the full-bridge inverter module. The damping matching circuit is used to match the inductive impedance of the transmitting coil, absorb the residual oscillation energy on the falling edge of the pulse, suppress the distortion of the excitation current tail, and optimize the quality of the primary field waveform. The transmitting coil receives the time-domain pulse excitation current output from the full-bridge inverter and radiates an alternating primary electromagnetic field, serving as the terminal execution component for the electromagnetic detection of underground media in this system.

[0055] according to Figure 2 The circuit topology shown in this disclosure includes a key circuit component: a dual-power switching module connected to the high-voltage DC source UH and the low-voltage DC source UL in the DC / DC power circuit power supply unit; the high-voltage DC source UH, the sixth MOSFET switch Q6, and the second diode D2 are sequentially connected to form a high-voltage power supply branch, and the low-voltage DC source UL, the seventh MOSFET switch Q7, and the third diode D3 are sequentially connected to form a low-voltage power supply branch. The high-voltage and low-voltage power supply branches are connected in parallel, and the output terminal of the parallel connection is connected in series with the first diode D1; the drive signals of the sixth MOSFET switch Q6 and the seventh MOSFET switch Q7 are output by the control module through the MOSFET driver. The dual-power switching module relies on Q6 and Q7 to achieve the selection and rapid switching of two voltage levels of power supply, providing the subsequent full-bridge inverter circuit module with different amplitude supply voltages required for generating the flat-top segment and high-frequency superposition segment of the time-domain main pulse; the first diode D1, the second diode D2, and the third diode D3 in the circuit work together to prevent reverse voltage backflow and transient overcurrent protection between the high-voltage DC source UH and the low-voltage DC source UL, ensuring a smooth and reliable voltage switching process.

[0056] The full-bridge inverter circuit module mainly consists of four MOSFETs: Q1, Q2, Q3, and Q4. Each MOSFET integrates a body diode. The source of Q1 is connected to the drain of Q3, and the source of Q2 is connected to the drain of Q4. The drains of Q1 and Q2 are connected to the positive output of the dual power supply switching module, while the sources of Q3 and Q4 are connected to the negative output. The connection points between Q1 and Q3, and between Q2 and Q4, serve as the two output terminals of the full-bridge inverter circuit module, with the transmitting load connected across them. The four MOSFETs form an H-type inverter topology, operating in a diagonal conduction mode. Q1 and Q4 form one diagonal pair, and Q2 and Q3 form another diagonal pair. The transmitting load includes a transmitting coil (equivalent to an inductor L1 and a resistor R1 connected in series) and a damping matching circuit. The full-bridge inverter module uses two sets of diagonal switches to alternately conduct in a time-division multiplexing manner, converting the input DC voltage into a bipolar trapezoidal pulse to provide the main pulse current in the time domain to the transmitting load. Each MOSFET switch has a built-in body diode that provides a freewheeling path for the inductive load current during the main switch's off period, working in conjunction with the active clamping circuit and the high-voltage source module to complete energy dissipation and voltage clamping. The damping matching circuit is connected in parallel across the transmitting coil and can selectively operate at the end of the pulse current's falling edge, matching the transmitting coil's inductive impedance, absorbing residual oscillation energy at the pulse's falling edge, suppressing distortion at the tail of the excitation current, and optimizing the primary waveform quality.

[0057] Without loss of generality, the MOSFET power switches in a full-bridge inverter circuit can be replaced by IGBTs or other controllable semiconductor switching devices, suitable for scenarios with higher voltages or different switching frequencies.

[0058] Without loss of generality, the structure of the dual-power supply switching circuit can be simplified. For example, only one switching transistor (such as the sixth MOSFET Q6) can be retained, while the low-voltage DC power supply UL can be directly connected or connected to the subsequent stage through an isolation diode, eliminating the need for the low-voltage branch switching transistor (such as the seventh MOSFET Q7). When a high-voltage DC power supply UH needs to be connected within the high-frequency superposition window, the control module outputs a control signal to turn on the sixth MOSFET Q6, and the low-voltage branch is automatically turned off due to the reverse bias of the isolation diode; when it is necessary to switch back to the low-voltage DC power supply UL, the sixth MOSFET Q6 is turned off, and the low-voltage branch automatically resumes conduction through the isolation diode. This simplified scheme can reduce one power switching transistor, reduce system conduction losses and drive circuit complexity, but precise timing coordination is required to avoid voltage conflicts and current surges during high-low voltage switching.

[0059] The active clamping circuit and high-voltage source module consist of a clamping MOSFET switch Q5, a high-voltage energy storage capacitor C1, a power diode D4, a bleeder resistor R2, and an adjustable high-voltage power supply, which is taken from the DC / DC power circuit power supply unit of the power management module. The active clamping circuit and high-voltage source are connected in parallel to the output of the full-bridge inverter module. The internal circuit connections are as follows: the adjustable high-voltage power supply is connected in series with the power diode D4 and then connected to the high-voltage energy storage capacitor C1; the bleeder resistor R2 is connected in parallel across the high-voltage energy storage capacitor C1; one end of the high-voltage energy storage capacitor C1 is connected to the drain of the clamping MOSFET switch Q5, and the other end is grounded. The active clamping circuit and high-voltage source module are connected in parallel to the full-bridge inverter module, and the source of the clamping MOSFET switch Q5 is connected to the drains of Q1 and Q2 in the full-bridge inverter module. This module combination actively injects energy into the load during the rising edge of the load current to accelerate current build-up, and absorbs the stored energy of the inductive load and clamps voltage spikes during the current decline, achieving a rapid linear rise and fall of the current waveform.

[0060] Without loss of generality, the high-voltage energy storage capacitor in the active clamping circuit and high-voltage source module can be achieved by using multiple capacitors connected in series and parallel to achieve the required withstand voltage and capacitance value, and the discharge resistor R2 can also be adjusted according to the discharge time requirements.

[0061] Without loss of generality, the dual-core architecture of MCU and FPGA in the control module can be replaced by a high-performance single FPGA with an embedded soft-core processor, or it can be implemented independently by a high-performance MCU with high-resolution timers and programmable logic units. These alternatives are suitable for engineering scenarios with limited system costs or hardware resources. While meeting timing control accuracy requirements, they can simplify circuit board design, reduce module size, and facilitate further weight reduction in aerospace platforms.

[0062] The control module generates high-precision real-time timing control signals, covering the full-bridge inverter circuit drive signals, the high-low voltage power switching control signals of the dual power supply switching circuit, and the clamping intervention signals of the active clamping circuit and the high-voltage source module. The module is internally equipped with multi-channel timers, enabling precise setting of the rising edge, falling edge, dead time, and clamping intervention window of the drive pulse with nanosecond-level resolution. The control module receives clamping voltage detection, clamping current detection, transmit current detection, and transmit voltage detection feedback signals from the voltage and current detection unit, and dynamically corrects the control parameters through a built-in adaptive closed-loop algorithm. The control module outputs signals to the MOSFET driver, which outputs drive signals to regulate the operating state of the full-bridge inverter circuit, outputs power control signals to select and switch between the low-voltage UL and high-voltage UH of the dual power supply switching circuit, and simultaneously outputs clamping control signals to precisely adjust the clamping voltage amplitude and clamping intervention time of the active clamping circuit and the high-voltage source module. This control module ensures nanosecond-level timing control accuracy and achieves closed-loop control of the entire circuit.

[0063] This invention also provides a control method for an airborne electromagnetic composite superposition time-frequency pulse transmission system, used to control the operation of the aforementioned time-frequency electromagnetic transmitter. The control method is as follows: Figure 3 As shown, it includes:

[0064] Step S1, Parameter Configuration: Preset the bipolar trapezoidal time-domain master pulse parameters (including fundamental frequency, duty cycle, low-voltage UL parameters) and high-frequency square wave parameters (including frequency, high-voltage UH) according to the detection requirements. Set the first dead time tdf and the last dead time tdb. The first dead time tdf ensures that the clamping t_cs at the rising edge is completely finished, and the current is stable under the low-voltage UL before high-frequency superposition begins, preventing edge oscillation from affecting the high-frequency quality. The last dead time tdb ensures that the turn-off transient of the last high-frequency pulse is completely finished before entering the falling edge of the master pulse, avoiding energy residue affecting the turn-off characteristics. Record the load resistance R and the load inductance L. Then perform the parameter calculation steps: based on the time constant τ=L / R of the RL series circuit, and the clamping voltage Uc, high-voltage UH, low-voltage UL, high current IH=UH / R, and low current IL=UL / R. Using the total response formula for a first-order circuit, calculate the rising-edge start-up clamping duration t_cs, the high-frequency superposition clamping duration t_ch, and the synchronous turn-off duration t_qo. The specific calculation formulas are as follows:

[0065] The formula for calculating the rising edge start clamping duration t_cs is:

[0066] ,

[0067] The formula for calculating the high-frequency superimposed clamping duration t_ch is:

[0068] ,

[0069] The formula for calculating the synchronous shutdown duration t_qo is:

[0070] ,

[0071] Where t_cs, t_ch, and t_qo are all in seconds (s), and ln represents the natural logarithm. Uc is always greater than UH, and UH is always greater than UL.

[0072] In the foregoing embodiments, the high-frequency excitation signal superimposed on the flat-top segment of the bipolar trapezoidal wave main pulse is in the form of a square wave. Without loss of generality, the form of this high-frequency superimposed waveform can also be replaced with other periodic waveforms such as sawtooth waves, triangular waves, or sine waves, depending on the specific requirements of the detection target. However, square waves, due to their steep rising and falling edges containing abundant odd harmonic components in the frequency domain, offer higher energy utilization efficiency for broadband electromagnetic excitation. Furthermore, they exhibit lower switching losses and simpler drive control in engineering implementation; therefore, square waves are the preferred embodiment. Those skilled in the art can select an appropriate waveform form based on the actual detection frequency band requirements, the switching frequency limitations of the transmitting system, and the tolerance capabilities of the power devices.

[0073] It should be noted that the analytical calculation formulas for the aforementioned rising edge start-up clamping duration, high-frequency superimposed clamping duration, and synchronous turn-off duration are derived based on an ideal RL series circuit model, i.e., neglecting the influence of non-ideal factors such as line parasitic resistance, power switch on-state voltage drop, and diode forward voltage drop on the equivalent impedance of the circuit. In practical engineering applications, these non-ideal factors will cause a certain deviation between the actual current response and the theoretical calculation value. To address this, the system uses a detection module to collect circuit current data in real time and feed it back to the control module. The control module then performs closed-loop adaptive fine-tuning of parameters such as clamping duration, clamping voltage, and dead time based on the deviation between the measured waveform and the preset target waveform, thereby effectively compensating for the influence of non-ideal factors and ensuring that the output waveform can still stably meet the preset performance requirements under actual operating conditions.

[0074] Step S2, Basic Waveform Generation: The control module outputs a full-bridge inverter drive signal to control the power transistors to conduct alternately, generating a bipolar trapezoidal time-domain main pulse.

[0075] Step S3, High-Frequency Superposition and Segmented Clamping Control: Using the pre-dead zone and post-dead zone as boundaries, a safe window is extracted from the middle flat-top segment of the bipolar trapezoidal time-domain main pulse. Within this safe window, a dual-power switching circuit switches between the low-voltage DC and the high-voltage DC to superimpose a high-frequency square wave. During the rising phase of the bipolar trapezoidal time-domain main pulse, the clamping switch is activated to maintain the clamping duration from the rising edge. When the dual-power switching circuit switches to the high-voltage DC, the clamping switch is activated again to maintain the high-frequency superposition clamping duration, forcing the current to rise rapidly and forming a stable current flat-top. At the instant the bipolar trapezoidal time-domain main pulse turns off, the full-bridge power circuit is simultaneously cut off and clamping energy discharge is initiated, shortening the current falling edge duration.

[0076] Step S4, Closed-Loop Parameter Optimization: Utilizing a Hall effect sampling circuit in conjunction with a high-speed ADC, real-time loop current data is acquired at a sampling rate of at least 1MHz. Based on the flatness of the measured waveform and the high-frequency spectrum amplitude, the dead-time, clamping voltage, and high-voltage UH output parameters are dynamically fine-tuned. The FPGA in the control module calculates the acquired data, extracting the current ripple coefficient of the flat-top segment, the actual rise time, the actual fall time, and the spectrum amplitude of the high-frequency superposition segment, and compares them with preset thresholds.

[0077] If the flat-top ripple coefficient exceeds 5%, fine-tune the clamping voltage Uc or adjust the first dead time tdf and the last dead time tdb; if the spectral amplitude of the high-frequency superposition segment at the required frequency is lower than the preset value, increase the high-voltage power supply U_H or appropriately shorten the dead time to increase the high-frequency window; if the falling edge time exceeds the expected time, such as exceeding 5μs, increase the clamping voltage Uc or extend the programming coefficient of the synchronous turn-off duration t_qo.

[0078] After several iterations to ensure all indicators meet the standards, the current optimal parameter set is fixed to the FPGA and power module, and the system enters a steady-state working mode.

[0079] Step S5, Stable Output: The system operates with dynamically optimized parameters locked, continuously and stably sending time-frequency superimposed composite pulse waveforms that meet preset indicators. The time-domain portion of the time-frequency composite pulse is a bipolar trapezoidal wave, and the frequency domain portion is a high-frequency square wave, with the high-frequency square wave superimposed on the flat-top segment of the bipolar trapezoidal wave.

[0080] In the embodiments disclosed herein, such as Figure 4 As shown, they respectively demonstrate in Figure 2The circuit topology diagram shows the waveforms of the transmitting current I and transmitting voltage U when transmitting a time-frequency electromagnetic pulse, as well as the signal timing of switches Q1 and Q4, switches Q2 and Q3, clamping switch Q5, and dual-supply switching switch Q6. Q7 controls the low voltage UL, which is normally on; Q6 controls the high voltage UH and is interlocked with Q7, meaning that when one is on, the other is off. UH and UL are the high and low voltages, respectively, and Uc is the clamping voltage. The first dead time is denoted as tdf, and the last dead time is denoted as tdb. The dead time is used to prevent aliasing of the time-frequency waveform.

[0081] like Figure 4 As shown. The period before time t1 is the preparation phase for launch, during which the transmitter's main power is turned on and parameter settings are completed.

[0082] At time t1, a transmission cycle begins, transmitting a time-frequency composite electromagnetic pulse waveform. During this time, Q1 and Q4 are turned on, and current flows forward through the transmitting load. Simultaneously, Q5 is turned on for a short period until t2. This period from t1 to t2 is called the startup clamping duration t_cs, which refers to the duration during which the active clamping circuit is first activated during the current rise phase. At this time, the voltage is clamped to Uc, and the current rapidly rises to the low-voltage steady-state value IL.

[0083] At time t2, Q5 is turned off, the voltage drops to UL, and the current enters the flat-top segment. After the pre-dead time tdf, time t3 is reached, at which point the current has stabilized at IL. High-frequency waveform superposition begins: Q6 is turned on, a high-frequency voltage UH is applied, and Q5 is simultaneously turned on, the voltage rises to Uc, and after a short period, the current reaches IH. This period is called the high-frequency clamping duration t_ch. t_ch refers to the time during which the clamping circuit intervenes when switching voltages within the high-frequency superposition window. At this moment, Q5 is turned off, the voltage reaches UH, and the high-level half-cycle of the high-frequency square wave is maintained.

[0084] At time t4, the voltage is switched off, Q6 is turned off, and the power supply switches back to UL. Simultaneously, Q1 and Q4 are turned off. Active clamping automatically engages via the body diode, and the voltage reverses to -Uc. The bleeder resistor quickly absorbs energy, causing the current to drop rapidly to IL. This period is called the synchronous turn-off time t_qo. Then, Q1 and Q4 are turned on, and the voltage returns to UL, completing the superposition of a high-frequency square wave pulse. Repeating the above steps forms a continuous high-frequency square wave on the flat-top segment of the bipolar trapezoidal wave.

[0085] When the high-frequency superposition window ends, and a dead time tdb is reserved before the end of the positive cycle of the bipolar trapezoidal wave, no dual-power supply switching will occur during this period. At time t5, Q1 and Q4 are turned off, the active clamping circuit automatically intervenes, and the current rapidly decreases from IL to 0 until time t6, when the positive half-cycle of the time-frequency composite waveform ends.

[0086] The control logic of the negative half-cycle is completely symmetrical to that of the positive half-cycle. Only Q1 and Q4 are replaced with Q2 and Q3 to conduct, and the current flows through the load in reverse. Its clamping, high frequency superposition and dead time sequence are the same.

[0087] Thus, a complete bipolar time-frequency composite pulse cycle is completed. By repeating the above steps, the required time-frequency superimposed composite pulse waveform can be continuously transmitted. During transmission, the detection unit collects current and voltage data in real time and feeds it back to the control module. The control module automatically adjusts parameters such as clamping voltage, dead time, and switching point based on the deviation between the measured waveform and the preset indicators to ensure that the output waveform always meets the requirements and achieves stable closed-loop transmission.

[0088] The control method of the present invention for the airborne electromagnetic composite superposition time-frequency pulse transmission system is applied to the above-mentioned time-frequency electromagnetic transmitter. Through a five-step process of precise parameter configuration, theoretical parameter calculation, basic waveform generation, high-frequency superposition and segmented clamping control, closed-loop parameter iterative optimization, and steady-state locked output, high-precision and high-stability bipolar time-frequency superposition composite pulse transmission is achieved.

[0089] Step S1: Parameter configuration and parameter calculation.

[0090] First, parameter configuration is performed. Based on the actual requirements of airborne electromagnetic detection, the bipolar trapezoidal time-domain master pulse parameters and waveform superposition parameters are preset. The bipolar trapezoidal time-domain master pulse parameters include: fundamental frequency 25Hz, duty cycle 0.25; high-frequency superposition 5kHz; system high-voltage power supply UH0=52V; and low-voltage power supply UL0=47V. The pre-dead time is set to tdf=5×10⁻⁶. -4 s and after-dead time tdb = 5 × 10 -4 In this simulation example, the fixed load parameters are: load resistance R = 0.5Ω, load inductance L = 0.5mH, and clamping voltage Uc = 500V. Since the switching transistor and diode also have a certain voltage drop (simulated voltage drop is 2V), the equivalent high and low power supplies acting on the load are UH1 = 50V and UL1 = 45V. UH0 and UL0 are the actual voltage sources, while UH1 and UL1 are the voltage sources acting on the load.

[0091] The parameter calculation steps are then carried out. Based on the fixed load parameters in this simulation, the time constant of the RL series load circuit is determined by the load resistance R and the load inductance L.

[0092] The calculated time constant τ = L / R = 1 × 10 -3 ;

[0093] The clamping duration at the rising edge is t_cs = 94.3us;

[0094] The high-frequency superposition clamping duration t_ch = 11.0us;

[0095] Synchronization shutdown duration t_qo = 9.13us;

[0096] The calculated t_cs, t_ch, t_qo, as well as the dead zone parameters, power supply voltage parameters, and load parameters are all entered into the control module as the reference parameters for system waveform regulation.

[0097] Step S2: Generate basic waveform.

[0098] The control module outputs a full-bridge inverter drive signal to drive the power switching transistors of the full-bridge circuit to turn on and off alternately. Powered by the high-voltage power supply UH, it generates a standard bipolar trapezoidal time-domain main pulse, providing a stable time-domain base waveform for the waveform superposition of time-frequency composite pulses.

[0099] Step S3: High-frequency superposition and segmented clamping control.

[0100] Using the previous dead time tdf and the subsequent dead time tdb as boundary intervals, a flat-topped segment in the middle of the bipolar trapezoidal time-domain main pulse is selected as a waveform superposition safety window, and waveform superposition is performed only within this safety window. A dual-power supply switching circuit enables controllable switching between paired high and low voltage power supplies. Periodically switched waveforms are superimposed on the power circuit of the high-voltage trapezoidal main pulse to generate a time-frequency superimposed composite pulse waveform. Synchronous execution of segmented active clamping control: During the rising phase of the bipolar trapezoidal time-domain main pulse current, the clamping switch is turned on and the clamping duration t_cs is continuously started on the rising edge, forcing the loop current to rise rapidly, eliminating the slow rise edge variation and overshoot problem, and quickly establishing the high-voltage steady-state current corresponding to UH; at the instant when the dual power supply switching circuit completes the switching between UH and UL, the clamping switch is turned on again and the clamping duration t_ch is continuously superimposed to suppress the voltage and current fluctuations caused by the switching of UH and UL voltages, ensuring that the waveform is flat during the superposition process; at the instant when the bipolar trapezoidal time-domain main pulse is turned off, the full-bridge power loop is simultaneously cut off, and the active clamping energy discharge mechanism is started at the same time. Relying on the synchronous turn-off duration t_qo, the residual energy of the loop is quickly released, the current falling edge duration is significantly shortened, and the waveform turn-off characteristics are optimized.

[0101] Step S4: Closed-loop parameter optimization.

[0102] During system operation, the voltage and current detection module samples various voltages and currents and feeds them back to the control module. The FPGA chip inside the control module performs real-time calculations on the sampled data, extracting core waveform indicators such as the current ripple coefficient of the flat-top segment, the actual rise time, the actual fall time, and the spectral amplitude of the waveform superposition segment. The measured indicators are then compared with preset thresholds to achieve closed-loop dynamic parameter fine-tuning.

[0103] The specific optimization logic is as follows: If the ripple coefficient of the current flat-top segment exceeds 5%, then fine-tune the clamping voltage Uc, or adjust the first dead time tdf and the last dead time tdb to optimize the flatness of the flat-top; if the spectral amplitude corresponding to the target frequency of the waveform superposition segment is lower than the preset threshold, then fine-tune the low-voltage power supply voltage UL, match the working range of the high-voltage power supply voltage UH, or appropriately shorten the dead time and widen the waveform superposition safety window to improve the waveform superposition efficiency; if the current falling edge duration exceeds the preset expected value of 5μs, then increase the clamping voltage Uc, or increase the programming coefficient of the synchronous turn-off duration t_qo to accelerate the energy discharge speed.

[0104] Through multiple iterations of optimization until all waveform indicators meet the preset standards, the current optimal parameter set is then fixed to the FPGA control module and the high and low voltage power supply modules. The system locks the optimal parameters and enters a steady-state operating mode. The final iteration data are as follows: the rising edge start clamping duration t_cs is calculated to be 92.9 μs using the corresponding formula; the superimposed clamping duration t_ch is calculated to be 10.8 μs using the corresponding formula; and the synchronous turn-off duration t_qo is calculated to be 8.98 μs using the corresponding formula.

[0105] Step S5: Stabilize output.

[0106] The system operates stably and continuously, relying on the iteratively optimized fixed parameters, and continuously transmits time-frequency superimposed composite pulse waveforms that meet the preset accuracy indicators. The time-domain basis of this composite pulse is a bipolar trapezoidal wave, and the frequency-domain feature is a periodically switching waveform superimposed on the flat top segment of the trapezoidal wave, realizing the composite detection requirements of large-depth time-domain detection and high-precision frequency-domain resolution.

[0107] Final realization Figure 5 The simulated waveform for half a cycle shows the upper half of the curve as the transmitting load current waveform and the lower half as the transmitting load voltage waveform. The waveform fully meets the design goal of time-frequency composite superimposed pulse.

[0108] Thirdly, the present invention provides an electronic device, comprising: one or more processors; a memory for storing one or more programs; wherein, when the one or more programs are executed by the one or more processors, the one or more processors implement the aforementioned control method.

[0109] Fourthly, the present invention provides a computer-readable storage medium having executable instructions stored thereon, which, when executed by a processor, enable the processor to implement the aforementioned control method.

[0110] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An airborne electromagnetic composite superposition time-frequency pulse transmission system, characterized in that, include: The dual power supply switching module has its input terminals connected to a high-voltage DC power supply and a low-voltage DC power supply respectively, and its output terminal connected to the input terminal of the full-bridge inverter circuit module, which is used to switch the output of high-voltage DC power or low-voltage DC power as needed. The full-bridge inverter circuit module has its input terminal connected to the output terminal of the dual power supply switching module, and its two output terminals are connected across the transmitting load to invert the input DC voltage into a bipolar trapezoidal wave main pulse. An active clamping circuit and a high-voltage source module are connected in parallel to the two output terminals of the full-bridge inverter circuit module. They are used to actively inject energy during the current rise phase to accelerate current build-up, and to absorb inductive load energy and clamp voltage spikes during the current fall phase. The control module has a first signal output terminal connected to the control electrode of each switching transistor in the full-bridge inverter circuit module to output a full-bridge inverter drive signal, a second signal output terminal connected to the control electrode of each switching transistor in the dual power supply switching module to output a high-low voltage switching control signal, and a third signal output terminal connected to the control electrode of the clamping switching transistor in the active clamping circuit and high-voltage source module to output a clamping intervention control signal. The detection module has its sampling end connected to the current loop of the transmitting load and its signal output end connected to the feedback input end of the control module, which is used to collect the transmitting current and voltage in real time and feed them back to the control module. The control module dynamically corrects the timing parameters of each control signal based on the current and voltage data fed back by the detection module, so that the flat-top segment of the bipolar trapezoidal wave main pulse is superimposed with a high-frequency square wave to form a time-frequency composite pulse.

2. The airborne electromagnetic composite superposition time-frequency pulse transmission system according to claim 1, characterized in that, The dual power supply switching module includes a first high-voltage switch, a second low-voltage switch, a first isolation diode, a second isolation diode, and a third isolation diode. The first high-voltage switch and the second isolation diode are connected in series to form a high-voltage branch, and the second low-voltage switch and the third isolation diode are connected in series to form a low-voltage branch. The high-voltage branch and the low-voltage branch are connected in parallel and then connected in series with the first isolation diode. The control terminals of the first high-voltage switch and the second low-voltage switch are respectively connected to the control module.

3. The airborne electromagnetic composite superposition time-frequency pulse transmission system according to claim 1, characterized in that, The full-bridge inverter circuit module includes a first switch, a second switch, a third switch, and a fourth switch. The source of the first switch is connected to the drain of the third switch, and the source of the second switch is connected to the drain of the fourth switch. The drains of the first and second switches are connected to the positive output terminal of the dual power supply switching module, and the sources of the third and fourth switches are connected to the negative output terminal of the dual power supply switching module. The connection nodes of the first and third switches and the second and fourth switches serve as two output terminals bridging the transmitting load.

4. The airborne electromagnetic composite superposition time-frequency pulse transmission system according to claim 1, characterized in that, The active clamping circuit and high-voltage source module include a clamping switch, an energy storage capacitor, a power diode, a bleeder resistor, and an adjustable clamping power supply. The adjustable clamping power supply is connected in series with the power diode and then connected to the energy storage capacitor. The bleeder resistor is connected in parallel across the energy storage capacitor. One end of the energy storage capacitor is connected to the drain of the clamping switch, and the other end is grounded. The source of the clamping switch is connected to the positive output terminal of the full-bridge inverter circuit module.

5. The airborne electromagnetic composite superposition time-frequency pulse transmission system according to claim 1, characterized in that, The control module includes an MCU and an FPGA. The FPGA generates multiple timing control signals according to configuration parameters. The timing control signals include the alternating conduction signals of the diagonal switches of the full-bridge inverter circuit module, the high-low voltage switching signals of the dual power supply switching module, and the clamping intervention signals of the active clamping circuit and the high-voltage source module. The MCU and the FPGA communicate bidirectionally to transmit operating parameters and operating status.

6. The airborne electromagnetic composite superposition time-frequency pulse transmission system according to claim 1, characterized in that, The detection module includes a Hall current sensor and a high-speed analog-to-digital converter. The Hall current sensor is connected in series in the current loop of the transmitting load. The sampling rate of the high-speed analog-to-digital converter is not less than 1MHz. The detection module uploads the real-time sampled current data and voltage data to the control module. The control module dynamically corrects the clamping voltage amplitude, dead time, and switching point parameters based on the deviation between the measured waveform and the preset indicators.

7. The airborne electromagnetic composite superposition time-frequency pulse transmission system according to claim 1, characterized in that, The transmitting load includes a transmitting coil and a damping matching circuit. The damping matching circuit is connected in parallel across the transmitting coil to match the inductive impedance of the transmitting coil and absorb the residual oscillation energy of the falling edge of the pulse.

8. A control method applied to the airborne electromagnetic composite superposition time-frequency pulse transmission system according to any one of claims 1-7, characterized in that, include: Step 1: Preset the main pulse parameters of the bipolar trapezoidal wave and the high-frequency square wave parameters, and record the load resistance and load inductance. Calculate the rising edge start clamping time, high-frequency superposition clamping time and synchronous turn-off time according to the full response formula of the first-order circuit. Step 2: Output the full-bridge inverter drive signal to control the power switching transistors to conduct alternately, generating a bipolar trapezoidal main pulse; Step 3: Using the preset pre-dead time and post-dead time as boundaries, within the safety window of the flat-top segment of the bipolar trapezoidal wave main pulse, the dual power supply switching module switches between low-voltage DC and high-voltage DC to superimpose a high-frequency square wave. During the current rising phase, the clamping switch is turned on to continue the clamping duration at the rising edge. When switching to high-voltage DC, the clamping switch is turned on again to continue the high-frequency superimposed clamping duration. When the main pulse is turned off, the full-bridge power circuit is simultaneously cut off and clamping energy discharge is initiated. Step 4: Collect the transmission current data in real time, and dynamically fine-tune the control parameters based on the flatness of the measured waveform and the amplitude of the high-frequency spectrum. Step 5: Lock the operation with the optimized parameters and continuously output time-frequency composite pulses.

9. The control method according to claim 8, characterized in that, The rising edge start clamping duration is determined by multiplying the time constant of the load resistance and load inductance by a first natural logarithm ratio, where the first natural logarithm ratio is the natural logarithm of the ratio of the clamping voltage to the difference between the clamping voltage and the low voltage. The high-frequency superposition clamping duration is determined by multiplying the time constant by a second natural logarithm ratio, where the second natural logarithm ratio is the natural logarithm of the ratio of the difference between the clamping voltage and the low voltage to the difference between the clamping voltage and the high voltage. The synchronous turn-off duration is determined by multiplying the time constant by a third natural logarithm ratio, where the third natural logarithm ratio is the natural logarithm of the ratio of the sum of the high voltage and the clamping voltage to the sum of the low voltage and the clamping voltage.

10. The control method according to claim 8, characterized in that, In step 4, when the current ripple coefficient of the flat-top segment exceeds the preset threshold, the clamping voltage is finely adjusted or the front dead time and the rear dead time are adjusted; when the spectral amplitude of the high-frequency superposition segment at the target frequency is lower than the preset value, the high-voltage power supply voltage is increased or the dead time is shortened; when the falling edge time exceeds the expected value, the clamping voltage is increased or the programming coefficient of the synchronous turn-off duration is extended. After iterating until all indicators meet the standards, the optimal parameter set is fixed into the control module.

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