Frequency / waveform adjustable bipolar Gaussian pulse source and working method thereof

Abstract

The invention discloses a frequency / waveform adjustable bipolar Gaussian pulse source and a working method thereof, and belongs to the field of electronic circuits. According to the pulse source, a bipolar pulse is obtained in a mode that a positive unipolar pulse and a negative unipolar pulse are subjected to delay synthesis. The main structure is divided into the following parts: a positive unipolar pulse circuit, a negative unipolar pulse circuit, a delay trigger circuit, a direct current input circuit, an isolation circuit and a filter shaping circuit. The unipolar pulse source adopts a multi-stage Marx circuit, a triode is used as a switch, and energy storage capacitors are connected in parallel for charging when the unipolar pulse source is closed; during triggering, the triodes are subjected to avalanche breakdown, the energy storage capacitors are connected in series for discharging, and the output amplitude is multiplied. Specific delay trigger signals are generated through the delay circuit to control the two unipolar sources to output in sequence, output pulses of the two unipolar sources are integrated through the isolation circuit, and final output is obtained through processing of the filter circuit. The frequency spectrum and the waveform of the output pulse can be flexibly adjusted by adjusting the capacitance, the circuit series and the filter circuit element parameters in the Marx circuit.

Description

Technical Field

[0001] The present invention belongs to the technical field of electronic circuits, relates to the design of a pulse signal source, and particularly relates to a frequency / waveform adjustable bipolar Gaussian pulse source and its working method. Background Art

[0002] Ultra-wideband narrow pulses have characteristics such as large bandwidth, low consumption, low cost, and high speed, and have very wide applications in the field of electromagnetic detection. In order to meet the requirements of ultra-wideband narrow pulses in fields such as impulse pulse regime ground penetrating radar, time-domain measurement instruments and equipment, and high-power microwaves, it is of important application value to research and design a narrow pulse signal source with high amplitude.

[0003] Based on the mechanism of parallel charging and series discharging of capacitors, a multi-stage Marx circuit based on avalanche transistors can generate narrow pulses with relatively high amplitudes and is often used to generate ultra-wideband pulse signals. As a solid-state switching device with various advantages such as fast response, small jitter, long lifespan, low cost, and small size, avalanche transistors are widely used in the design of pulse sources. The mechanism of avalanche transistors as switches in a pulse source circuit lies in their avalanche breakdown characteristics. By using the instantaneous breakdown voltage generated by avalanche breakdown, a pulse signal with an extremely fast rising edge, narrow width, and high voltage amplitude can be obtained; and then through the series voltage boost of a multi-stage Marx circuit, an extremely high amplitude output can be obtained, which is of great significance for the development of pulse sources towards modularization, miniaturization, and practicality.

[0004] At present, most of the pulse sources based on multi-stage Marx circuits are unipolar sources, and there are a large number of low-frequency components in their spectra, which is not conducive to antenna emission. The method for obtaining bipolar pulses is usually to add a high-pass filter at the output end of the circuit to filter out the low-frequency components and convert the waveform into a bipolar form. The signal waveform obtained by this method is poor, and the positive and negative peak values differ greatly, and there are a series of problems such as difficult spectrum adjustment and amplitude reduction.

[0005] Ground penetrating radar uses electromagnetic waves to detect and track image shallow underground targets, and is a non-invasive and non-destructive detection method with high resolution. The impulse radar has the advantages of simple structure, low production cost and high resolution, and has a wider application than the frequency modulation continuous wave radar. As one of the key technologies in the impulse radar system, the ultra-wideband narrow pulse technology directly affects the detection depth and accuracy of the ground penetrating radar. In addition to the amplitude and pulse width, the waveform and frequency spectrum distribution of the pulse also have an important impact on the entire ground penetrating radar system. The frequency spectrum range of the pulse signal should be consistent with the working frequency band of the ground penetrating radar antenna. Otherwise, the actually transmitted signal will be lost and deformed, which requires the main energy of the pulse signal to be concentrated in the working frequency band; the better the waveform of the pulse signal, the closer the echo received by the system is to the calculated result, which is more conducive to information extraction and processing. Therefore, developing a pulse source with better waveform and frequency spectrum and easy to adjust is of great significance for the application in actual system engineering. Summary of the Invention

[0006] The present invention provides a frequency / waveform adjustable bipolar Gaussian pulse source and its working method, which can output a better waveform and frequency spectrum and is easy to adjust.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions: A frequency / waveform adjustable bipolar Gaussian pulse source includes a DC input circuit, a delay trigger circuit, a positive polarity pulse circuit, a negative polarity pulse circuit, an isolation circuit and a filtering and shaping circuit; the DC input circuit is connected to the input ends of the positive polarity pulse circuit and the negative polarity pulse circuit through the delay trigger circuit, the output ends of the positive polarity pulse circuit and the negative polarity pulse circuit are connected to the input end of the isolation circuit, the output end of the isolation circuit is connected to the first end of the filtering and shaping circuit, and the second end of the filtering and shaping circuit is connected to the output of the positive polarity pulse circuit; Both the positive polarity pulse circuit and the negative polarity pulse circuit adopt a Marx circuit based on the avalanche effect of a triode; The DC input circuit includes a DC power supply, and inductors are arranged between the DC power supply and the positive polarity pulse circuit, and between the DC power supply and the negative polarity pulse circuit.

[0008] Further, the inductance value L of the inductor is: L = 1.5CR 2 / 4, where C is the capacitance value of the energy storage capacitor in the positive polarity pulse circuit and the negative polarity pulse circuit, and R is the resistance value of the current limiting resistor in the positive polarity pulse circuit and the negative polarity pulse circuit.

[0009] Further, the delay trigger circuit includes a capacitor C06. The first end of the capacitor C06 is connected to the first end of a capacitor C07. After the capacitor C06, an inductor L3, and a resistor R01 are connected in series, they are connected to the first end of a resistor R02 and the base of a triode Q1 in the positive polarity pulse circuit. The second end of the resistor R02 is grounded. The capacitor C07, an inductor L4, and a resistor R03 are connected in series and then connected to the first end of a resistor R04 and the base of a triode Q11 in the negative polarity pulse circuit. The second end of the resistor R04 is grounded.

[0010] Further, the first ends of both the capacitor C06 and the capacitor C07 are connected to the anode of a diode D2, and the cathode of the diode D2 is connected to the inductor.

[0011] Further, the isolation circuit includes inductors L5, L6, L7, and L8. The first end of a first parallel branch formed by the parallel connection of the inductor L5 and the inductor L6 is connected to the emitter of the triode Q1, and the second end is connected to the first end of an output port Pout. The second end of the output port Pout is grounded. The inductors L7 and L8 are connected in parallel to form a second parallel branch. The first end of the second parallel branch is connected to the first end of an output resistor Rout2, and the second end is connected to the second end of the first parallel branch.

[0012] Further, the filter shaping circuit is a first-order filter circuit or a second-order filter circuit.

[0013] Further, the filter shaping circuit includes an inductor L9. The first end of a third parallel branch formed by the parallel connection of the inductor L9 and a capacitor C19 is grounded, and the second end is connected to the first end of an inductor L12. The second end of the inductor L12 is connected to the first end of a capacitor C20. The second end of the capacitor C20 is connected to the first end of the output port Pout, and the second end of the output port Pout is grounded.

[0014] Further, the DC input circuit includes a DC power supply P0. One end of the DC power supply P0 is connected to the anode of a diode D1, and the cathode of the diode D1 is connected to the first end of a capacitor C01, the first end of an inductor L2, and the first end of an inductor L1. The second end of the capacitor C01 is connected to the first end of a capacitor C02. The second end of the capacitor C02, the second end of a resistor R0, and one end of the DC power supply P0 are grounded.

[0015] Further, a resistor R0 is connected between the cathode of the diode D1 and the second end of the capacitor C02.

[0016] The working method of the above frequency / waveform adjustable bipolar Gaussian pulse source includes: In the time period from t0 to t1, all triodes in the positive polarity pulse circuit and the negative polarity pulse circuit are in the cut-off state, the circuit is in the charging state, and the voltages across all energy storage capacitors gradually charge from zero to the DC power supply voltage. At time t1, the high-level trigger signal reaches the base of the first triode in the negative-polarity pulse circuit through the delay circuit. The first triode undergoes avalanche breakdown and enters the conducting state. The first energy storage capacitor starts to discharge through the current-limiting resistor and the first triode, and the generated current further triggers the avalanche breakdown and conduction of the second triode, and so on. The first to the Nth triodes enter the conducting state in sequence; at this time, all the energy storage capacitors become connected in series, and current is output through the triodes and the output resistor, causing a negative pulse voltage to be generated at the output end of the output resistor. Similarly, at time t2, the high-level trigger signal reaches the base of the first triode in the positive-polarity pulse circuit through the delay circuit. All the triodes conduct simultaneously, all the energy storage capacitors discharge in series, and the current flows into the output resistor through the triodes, generating a positive pulse voltage at the output end of the output resistor. The negative pulse voltage generated at time t1 and the positive pulse voltage generated at time t2 pass through the isolation circuit and reach the filtering circuit to complete integration and post-processing, and finally reach the output end, being converted into a bipolar Gaussian pulse. After time t3, the circuit output is completed, and all the triodes return to the cut-off state, and the circuit then enters the charging state of the next cycle.

[0017] Compared with the prior art, the present invention has at least the following beneficial technical effects: The present invention adopts the method of synthesizing a bipolar pulse from positive and negative unipolar pulses, and can obtain an output waveform with symmetric positive and negative pulses, better waveform, and closer to the standard first-order Gaussian pulse. Moreover, it has a more easily adjustable spectrum and a higher output frequency, thus being more convenient for flexible application in various systems and reducing difficulties for subsequent signal processing.

[0018] A frequency / waveform adjustable bipolar Gaussian pulse source based on a Marx circuit and delay control provided by the present invention can realize functions such as adjustable output amplitude, waveform, frequency, and bandwidth of the signal by adjusting the series stage number of the Marx circuit and the size of the energy storage capacitor, and can further optimize and adjust the signal waveform and spectrum by adjusting the component parameters of the terminal isolation circuit and the filtering circuit, and can design the corresponding output high-voltage bipolar Gaussian pulse signal according to the requirements of different application scenarios.

[0019] By synthesizing positive and negative unipolar pulses, the obtained bipolar pulse has a relatively symmetric positive and negative peak waveform. Even after further filtering, the difference between the positive and negative peak values does not exceed 50%. Compared with the waveform generated by a single Marx circuit, the synthesized pulse signal has a higher amplitude, a smaller tail, a better waveform, and is closer to the standard Gaussian pulse. The mechanism of generating pulses by a single Marx circuit is the capacitor discharge after the avalanche breakdown of the triode. It inevitably has a phenomenon that the rising edge is extremely fast but the falling edge is relatively slow, resulting in a steep front and gentle back of its waveform, and there are wrinkles and burrs, which is different from the Gaussian pulse waveform and is difficult to adjust, being not conducive to standardization in engineering. The pulse synthesis method adopted in the present invention fuses the rising edge and the falling edge of the two unipolar pulses, making the waveform more symmetric; at the same time, through the processing of the isolation circuit and the filtering circuit, the overall waveform becomes smoother and closer to the standard first-order Gaussian pulse waveform. At the same time, compared with the output of a single Marx circuit, the spectrum of this pulse signal has a very steep edge, and the main energy is highly concentrated within this frequency band, facilitating the docking with the entire system in engineering. The higher dimension enables this circuit to have a larger adjustment space, and can adjust the waveform and spectrum of the pulse more flexibly and accurately, and can be better applied to various engineering environments.

[0020] Furthermore, the present invention improves the DC charging circuit by setting a large inductor between the DC power supply and the current-limiting resistor. Since the width of the output pulse in the time domain is very small, the conduction time of the triode is mainly determined by its recovery time, which is about dozens to hundreds of nanoseconds; and the large inductor can effectively suppress the current output by the power supply through the current-limiting resistor during this time, making it almost zero, thereby significantly reducing the resistance heating and improving the circuit efficiency. It is measured by experiments that under the condition of using the same pulse source circuit and with the same trigger frequency and output amplitude, for the circuit with this inductor, the effective value of the current consuming the DC power supply is significantly reduced. At the same time, since the inductor undertakes the main current-limiting task, the current-limiting resistor can be appropriately reduced to increase the charging speed of the circuit, thereby increasing the available trigger frequency. For this kind of pulse source circuit with a relatively high output amplitude, its trigger frequency is generally low. And the stable trigger frequency of this circuit is high, up to more than 300 kHz, far exceeding that of similar high-amplitude pulse source circuits; at the same time, this design effectively reduces the power consumption of the power supply, improves the efficiency while significantly reducing the circuit heating, can reduce the volume of the circuit board and the radiator, and improves the utilization efficiency of space and system resources. Description of the Drawings

[0021] Figure 1 A bipolar Gaussian pulse source topology provided by the present invention; Figure 2(a) is the overall circuit schematic diagram of the unipolar pulse source circuit provided by the present invention; Figure 2(b) is the charging equivalent circuit of the unipolar pulse source provided by the present invention; Figure 2 (c) is the equivalent circuit of the unipolar pulse source discharge provided by the present invention; Figure 3 is the improved circuit diagram provided by the present invention; Figure 4 is the simulation curve of the change in the charging voltage of the capacitor; Figure 5 (a) is the circuit diagram of the negative-polarity pulse source provided by the present invention; Figure 5 (b) is the circuit diagram of the positive-polarity pulse source provided by the present invention; Figure 6 is the delay trigger circuit provided by the present invention; Figure 7 (a) is the output waveform of the pulse source when the negative pulse triggers first with delay provided by the present invention; Figure 7 (b) is the output waveform of the pulse source when the positive pulse triggers first with delay provided by the present invention; Figure 8 is the schematic circuit diagram of the 5-stage bipolar pulse source provided by the present invention; Figure 9 (a) is the output waveform of the 5-stage circuit provided by the present invention; Figure 9 (b) is the output waveform of the 8-stage circuit provided by the present invention; Figure 10 is the schematic circuit diagram of the 8-stage bipolar pulse source provided by the present invention; Figure 11 is the output waveform of the 8-stage bipolar pulse source circuit provided by the present invention; Figure 12 is the conduction timing diagram of each triode in the 5-stage circuit. Detailed implementation manners

[0022] The present invention will be described in detail below in conjunction with the accompanying drawings and specific implementation manners.

[0023] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0024] It should be noted that when an element is referred to as being "disposed on" another element, it can be directly on the other element or there can also be another element in the middle. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be another element in the middle at the same time. The orientation or positional relationship indicated by the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc. used in this article is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be construed as a limitation on the present invention.

[0025] Unless otherwise defined, all technical and scientific terms used in this article have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used in this article includes any and all combinations of one or more of the related listed items.

[0026] The present invention obtains bipolar pulses by synthesizing positive and negative unipolar pulses with time delay. It mainly includes: a DC input circuit, a delay trigger circuit, a positive polarity pulse circuit, a negative polarity pulse circuit, an isolation circuit, and a filtering and shaping circuit, as Figure 1 shown.

[0027] The DC input circuit is connected to the input ends of the positive polarity pulse circuit and the negative polarity pulse circuit through the delay trigger circuit. The output ends of the positive polarity pulse circuit and the negative polarity pulse circuit are connected to the input end of the isolation circuit. The output end of the isolation circuit is connected to the first end of the filtering and shaping circuit. The second end of the filtering and shaping circuit is connected to the output of the positive polarity pulse circuit.

[0028] The design process of each circuit will be introduced below.

[0029] The unipolar pulse source adopts a Marx circuit based on the avalanche effect of a triode. Using the triode as a switch, all energy storage capacitors are charged in parallel when it is turned off; when the trigger signal arrives, the triode undergoes avalanche breakdown and the energy storage capacitors discharge in series, thus multiplying the output amplitude. Its circuit schematic diagram is shown in Figure 2.

[0030] Charging process: Figure 2 (b) is the equivalent circuit of the circuit during charging. All triodes are not triggered and can be regarded as open circuits. Each energy storage capacitor is connected in parallel to the power supply VCC through a current-limiting resistor for charging. When the voltage on the energy storage capacitor reaches high enough, the triode enters the avalanche waiting state.

[0031] Discharge process: Figure 2(c) shows the equivalent circuit of the circuit during discharge. When the energy storage capacitor is fully charged, the triode is close to the critical voltage of reverse breakdown. At this time, if a trigger signal is input to the base of the triode, the breakdown voltage of the triode decreases, avalanche breakdown occurs, and the discharge of the energy storage capacitor triggers the avalanche breakdown of the subsequent triodes, ultimately forming a series connection path between the energy storage capacitors; while the resistance value of the current-limiting resistor is large, and the discharge speed of the energy storage capacitor through it is much slower than the discharge speed through the load terminal, so it can be regarded as an open circuit.

[0032] In application scenarios with high charging voltage and high output amplitude, the charging time of the above pulse source circuit is relatively long, resulting in a relatively low available trigger frequency. When the circuit releases a pulse, since the triode conducts, the charging DC power supply will be directly loaded on the current-limiting resistor. For a circuit with a high charging voltage, too small a current-limiting resistor will cause serious heating of the circuit, even burning out components, and will also increase the loss during discharge. Therefore, the resistance has to be increased; while increasing the current-limiting resistor will increase the charging time of the energy storage capacitor, and the maximum trigger frequency that the pulse source can reach will also decrease accordingly. At the same time, in order to pursue a high output amplitude, energy storage capacitors with a large capacitance value need to be used to provide a larger output current, which further increases the charging time. For a pulse source with an output amplitude of up to hundreds of volts, its trigger frequency is usually lower than 100 kHz. To reduce the circuit charging time, increase the pulse trigger frequency, improve the circuit efficiency, and reduce heating, a large inductor L is added at the DC power supply input terminal. Its schematic diagram is as Figure 3 shown.

[0033] A large inductor L is set between the DC power supply and the current-limiting resistor in this circuit, which can suppress the generation of instantaneous current. Since the width of the output pulse in the time domain is very small, the conduction time of the triode is mainly determined by its recovery time, which is about dozens to hundreds of nanoseconds; while the large inductor L can effectively suppress the current output by the power supply through the current-limiting resistor during this time, making it almost zero, thus significantly reducing the heating of the resistor and improving the circuit efficiency. It is measured through experiments that under the condition of using the same pulse source circuit with the same trigger frequency and output amplitude, for the circuit with the inductor L, the effective value of the current consuming the DC power supply is significantly reduced. It can be seen that with the input and output unchanged, the presence of the inductor L effectively reduces the power consumption of the power supply, improves the efficiency, and reduces the circuit heating at the same time.

[0034] At the same time, since the inductor L undertakes the main current-limiting task, the current-limiting resistor can be appropriately reduced to increase the charging speed of the circuit, thereby increasing the trigger frequency. The addition of the inductor L also changes the original RC charging circuit, Figure 4 which is the simulation curve of the voltage change at both ends of the energy storage capacitor during charging with the same capacitance and resistance parameters. It can be seen that when L = 1.5CR 2When it is 1 / 4, the RLC circuit is in a slightly underdamped state, and the voltage across the energy storage capacitor can reach the power supply voltage faster and quickly tend to be stable, with a smaller oscillation amplitude and the shortest charging time, thereby further increasing the available trigger frequency.

[0035] Through this method, a high-power pulse source with a high charging voltage and a high output amplitude can obtain a higher trigger frequency, while significantly reducing the power consumption of the power supply and the heat generation of the circuit. In the test results of this pulse source, when using a 150V - 180V DC power supply for charging, for a high-power pulse source with an output amplitude exceeding 200V, the trigger frequency at which it can maintain stable output can reach 300kHz or even 500kHz.

[0036] To obtain a pair of unipolar pulses with opposite polarities and similar waveforms, based on the above unipolar pulse source circuit, by adjusting the position of the output resistor and changing the direction of the output current I, two unipolar pulse circuits, one positive and one negative, are obtained, and their structure is shown in Figure 5. By delaying the trigger signal through two RLC circuits, a delayed trigger signal with a time difference at the nanosecond level can be obtained, and the circuit is as Figure 6 shown. By controlling the two pulse sources with different polarities to output pulses sequentially at a specific delay time, the two unipolar pulse waveforms with a time delay obtained are shown in Figure 7(a) and Figure 7(b). In Figure 7(a) and Figure 7(b), the yellow is the output waveform of the positive pulse source, and the blue is the output waveform of the negative pulse source.

[0037] To obtain bipolar pulses, the above two unipolar pulses need to be delayed and combined. If directly combined, that is, directly connecting the output terminals of the two-polarity pulse source circuits, there will be an influence between the circuits, resulting in a change in the output waveform. Therefore, an isolation element needs to be added between the two unipolar source circuits. After trying various elements, an nH-level small inductor is finally used as the isolation element, and a more ideal and adjustable output waveform can be obtained.

[0038] By adjusting the sizes of the energy storage capacitor and the isolation inductor, and adding a capacitor and / or an inductor as a passive filter at the circuit output terminal, the output waveform and spectrum can be adjusted. After the above adjustments, better output results of the 5-stage and 8-stage circuits are obtained respectively. The circuit diagram of the 5-stage circuit is as Figure 8 shown, and the output waveform is shown in Figure 9 (yellow is the signal waveform, and purple is the spectrum). When the charging voltage is 180V, the 3dB bandwidth of the bipolar pulse obtained by the 5-stage circuit is 110 - 440MHz, the pulse amplitude is about 214V (peak-to-peak), the maximum value is 101V, and the minimum value is -113V; the 3dB bandwidth of the bipolar pulse obtained by the 8-stage circuit is 150 - 620MHz, the pulse amplitude is about 202V (peak-to-peak), the maximum value is 93V, and the minimum value is -109V.

[0039] To further optimize the waveform and reduce the non-smooth components such as wrinkles, burrs, and mutations in the waveform, a second-order band-pass filter (8-stage) is added at the circuit output to make it as smooth as possible, so that the signal can obtain a standard second-order Gaussian pulse waveform after being transmitted and received by the antenna, facilitating subsequent waveform extraction and processing.

[0040] Adjust the input part of the circuit, merge the DC input port and the trigger signal input port; replace the avalanche triode model, and adjust the DC charging voltage to 150V to facilitate docking with the overall ground-penetrating radar system.

[0041] After multiple experimental comparisons, an 8-stage bipolar pulse circuit is selected, and the above adjustment scheme is added. The final circuit diagram obtained is as shown in Figure 10 ; The output waveform is as shown in Figure 11 ; Figure 11 In it, the yellow is the waveform of the output signal, the purple is the spectrum of the output signal, and the cyan is the differential result of the output signal. The main body of the obtained signal is very smooth, the waveform is close to the first-order Gaussian pulse, and the waveform obtained by the differential operation conforms to the second-order Gaussian pulse waveform; the tail of the waveform has been controlled to be smaller after adjustment, and the full length of the waveform does not exceed 7 ns; the 3 dB bandwidth of the signal is 140 - 480 MHz, the pulse amplitude is about 132 V (peak-to-peak), the maximum value is 82 V, the minimum value is -50 V, and the difference between the positive and negative peaks is less than 50%.

[0042] The following details the 5-stage pulse source circuit. Referring to Figure 7, the 5-stage pulse source includes: a DC input circuit, a delay trigger circuit, a positive-polarity pulse circuit, a negative-polarity pulse circuit, an isolation circuit, and a filter shaping circuit. The resistance values of all current-limiting resistors in the positive-polarity pulse circuit and the negative-polarity pulse circuit are the same, the capacitance values of all energy storage capacitors are the same, and the parameters of all triodes are the same.

[0043] Among them, the DC input circuit includes a DC power supply P0, a diode D1, a resistor R0, a capacitor C01, a capacitor C02, an inductor L1, and an inductor L2. One end of the DC power supply P0 is connected to the anode of the diode D1, and the cathode of the diode D1 is connected to the first end of the resistor R0, the first end of the capacitor C01, the cathode of the diode D2, the first end of the inductor L2, and the first end of the inductor L1; the second end of the capacitor C01 is connected to the first end of the capacitor C02, and the second end of the capacitor C02, the second end of the resistor R0, and one end of the DC power supply P0 are grounded. The resistor R0 provides a discharge path for the large capacitor at the DC input end, enabling it to discharge quickly after the power is turned off.

[0044] The delay trigger circuit includes a trigger signal Pin, a diode D2, a capacitor C06, a capacitor C07, an inductor L3, an inductor L4, a resistor R01, a resistor R02, a resistor R03, and a resistor R04. The trigger signal Pin is connected to the anode of the diode D2, the first end of the capacitor C06, and the first end of the capacitor C07. The capacitor C06 is connected in series with the inductor L3 and the resistor R01 and then connected to the first end of the resistor R02 and the base of the triode Q1. The second end of the resistor R02 is grounded. The capacitor C07 is connected in series with the inductor L4 and the resistor R03 and then connected to the first end of the resistor R04 and the base of the triode Q11. The second end of the resistor R04 is grounded.

[0045] The diodes D1 and D2 play a rectifying role, and cooperate with the capacitors C06 and C07 to isolate the direct current, so that the input port Pin can be used as a common input port, and at the same time, the input direct current charging current and the trigger signal are input, that is, only one port can input the two inputs required by the pulse source.

[0046] The positive-polarity pulse circuit includes triodes Q1, Q2, Q3, Q4, Q5, current-limiting resistors R1, R2, R3, R4, R5, output resistor Rout1, resistor R9, current-limiting resistors R10, R11, R12, energy storage capacitors C1, C2, C3, C4, and C5.

[0047] The emitter of the triode Q1 is connected to the first end of the output resistor Rout1, the second end of the output resistor Rout1 is grounded, the collector of the triode Q1 is connected to the first end of the current-limiting resistor R1 and the first end of the energy storage capacitor C1. The second end of the current-limiting resistor R1 is connected to the second ends of the current-limiting resistors R2, R3, R4, and R5. The second end of the energy storage capacitor C1 is connected to the base of the triode Q2, the emitter of the triode Q2, and the first end of the resistor R9. The second ends of the resistor R9, the current-limiting resistors R10, R11, and R12 are grounded; The collector of transistor Q2 is connected to the first end of current-limiting resistor R2 and the first end of energy storage capacitor C2. The second end of energy storage capacitor C2 is connected to the base of transistor Q3, the emitter of transistor Q3, and the first end of current-limiting resistor R10. The collector of transistor Q3 is connected to the first end of current-limiting resistor R3 and the first end of energy storage capacitor C3. The second end of energy storage capacitor C3 is connected to the base of transistor Q4, the emitter of transistor Q4, and the first end of current-limiting resistor R11. The collector of transistor Q4 is connected to the first end of current-limiting resistor R4 and the first end of energy storage capacitor C4. The second end of energy storage capacitor C4 is connected to the base of transistor Q5, the emitter of transistor Q5, and the first end of current-limiting resistor R12. The collector of transistor Q5 is connected to the first end of current-limiting resistor R5 and the first end of energy storage capacitor C5. The second end of energy storage capacitor C5 is grounded.

[0048] The negative-polarity pulse circuit includes transistors Q11, Q12, Q13, Q14, Q15, current-limiting resistors R16, R17, R18, R19, R20, R24, R25, R26, R27, output resistor Rout2, and energy storage capacitors C11, C12, C13, C14, and C15.

[0049] The collector of transistor Q11 is connected to the first end of current-limiting resistor R16 and the first end of energy storage capacitor C11. The second end of current-limiting resistor R16 is connected to the second ends of current-limiting resistors R17, R18, R19, and R20. The second end of energy storage capacitor C11 is connected to the base of transistor Q12, the emitter of transistor Q12, and the first end of current-limiting resistor R24. The second ends of current-limiting resistors R24, R25, R26, and R27 are grounded. The collector of transistor Q12 is connected to the first end of current-limiting resistor R17 and the first end of energy storage capacitor C12. The second end of energy storage capacitor C12 is connected to the base of transistor Q13, the emitter of transistor Q13, and the first end of current-limiting resistor R25. The collector of transistor Q13 is connected to the first end of current-limiting resistor R18 and the first end of energy storage capacitor C13. The second end of energy storage capacitor C13 is connected to the base of transistor Q14, the emitter of transistor Q14, and the first end of current-limiting resistor R26. The collector of transistor Q14 is connected to the first end of current-limiting resistor R19 and the first end of energy storage capacitor C14. The second end of energy storage capacitor C14 is connected to the base of transistor Q15, the emitter of transistor Q15, and the first end of current-limiting resistor R27. The collector of transistor Q15 is connected to the first end of current-limiting resistor R20 and the first end of energy storage capacitor C15. The second end of energy storage capacitor C15 is connected to the first end of output resistor Rout2. The second end of output resistor Rout2 is grounded.

[0050] The isolation circuit includes inductors L5, L6, L7, and L8. Inductors L5 and L6 are in parallel. The first end of the formed first parallel branch is connected to the emitter of transistor Q1, and the second end is connected to the first end of output port Pout. The second end of output port Pout is grounded. Inductors L7 and L8 are in parallel. The first end of the formed second parallel branch is connected to the first end of output resistor Rout2, and the second end is connected to the second end of the first parallel branch.

[0051] The filtering and shaping circuit includes inductor L9. The first end of inductor L9 is grounded, and the second end is connected to the second end of the first parallel branch.

[0052] The circuit of the 8-stage circuit is described in detail below. The 8-stage pulse source includes: a DC input circuit, a delay trigger circuit, a positive-polarity pulse circuit, a negative-polarity pulse circuit, an isolation circuit, and a filtering and shaping circuit.

[0053] The DC input circuit of the 8-stage pulse source has two more inductors L10 and L11 than that of the 5-stage pulse source. The first end of inductor L10 is connected to the first end of inductor L1, and the second end is connected to the second end of current-limiting resistor R6. The first end of inductor L11 is connected to the first end of inductor L2, and the second end is connected to the second end of current-limiting resistor R21.

[0054] The delay trigger circuit is the same as that of the 5-stage pulse source.

[0055] The positive-polarity pulse circuit of the 8-stage pulse source has more transistors Q6, Q7, Q8, current-limiting resistors R6, R7, R8, R13, R14, R15, energy storage capacitors C6, C7, and C8 than that of the 5-stage pulse source. The second end of energy storage capacitor C5 is not grounded. The second end of current-limiting resistor R5 is not connected to inductor L1, but is connected to the second ends of inductor L10, current-limiting resistors R6, R7, and R8.

[0056] The second terminal of the energy storage capacitor C5 is connected to the base of the triode Q6, the emitter of the triode Q6, and the first terminal of the current limiting resistor R13. The collector of the triode Q6 is connected to the first terminal of the current limiting resistor R6 and the first terminal of the energy storage capacitor C6. The second terminal of the energy storage capacitor C6 is connected to the base of the triode Q7, the emitter of the triode Q7, and the first terminal of the current limiting resistor R14. The collector of the triode Q7 is connected to the first terminal of the current limiting resistor R7 and the first terminal of the energy storage capacitor C7. The second terminal of the energy storage capacitor C7 is connected to the base of the triode Q8, the emitter of the triode Q8, and the first terminal of the current limiting resistor R15. The collector of the triode Q8 is connected to the first terminal of the current limiting resistor R8 and the first terminal of the energy storage capacitor C8. The second terminals of the energy storage capacitor C8, the current limiting resistor R13, the current limiting resistor R14, and the current limiting resistor R15 are all grounded.

[0057] The negative pulse circuit of the 8-stage pulse source has more components than that of the 5-stage pulse source, including the current limiting resistors R21, R22, R23, the energy storage capacitors C16, C17, C18, the triodes Q16, Q17, Q18, and the current limiting resistors R28, R29, and R30. The second terminal of the energy storage capacitor C15 is not connected to the output resistor Rout2, and the second terminal of the current limiting resistor R20 is not connected to the inductor L2. Instead, it is connected to the second terminals of the inductor L12, the current limiting resistors R21, R22, and R23.

[0058] The second terminal of the energy storage capacitor C15 is connected to the base of the triode Q16, the emitter of the triode Q16, and the first terminal of the current limiting resistor R28. The collector of the triode Q16 is connected to the first terminal of the current limiting resistor R21 and the first terminal of the energy storage capacitor C16. The second terminal of the energy storage capacitor C16 is connected to the base of the triode Q17, the emitter of the triode Q17, and the first terminal of the current limiting resistor R29. The collector of the triode Q17 is connected to the first terminal of the current limiting resistor R22 and the first terminal of the energy storage capacitor C17. The second terminal of the energy storage capacitor C17 is connected to the base of the triode Q18, the emitter of the triode Q18, and the first terminal of the current limiting resistor R30. The collector of the triode Q18 is connected to the first terminal of the current limiting resistor R23 and the first terminal of the energy storage capacitor C18. The second terminal of the capacitor C18 is connected to the first terminal of the output resistor Rout2. The second terminals of the output resistor Rout2, the current limiting resistor R28, the current limiting resistor R29, and the current limiting resistor R30 are all grounded.

[0059] The isolation circuit of the 8-stage pulse source is the same as that of the 5-stage pulse source.

[0060] The filtering and shaping circuit includes inductor L9, inductor L12, capacitor C19 and capacitor C20. The first end of the third parallel branch formed by the parallel connection of inductor L9 and capacitor C19 is grounded, and the second end is connected to the first end of inductor L12. The second end of inductor L12 is connected to the first end of capacitor C20. The second end of capacitor C20 is connected to the first end of output port Pout, and the second end of output port Pout is grounded.

[0061] The bipolar Gaussian pulse source circuit provided by the present invention is based on the topological structure of the Marx circuit. The circuit structures and working principles of different series levels are the same. The overall working process is described below taking a five-stage circuit as an example. Refer to Figure 12 , the triodes used in this circuit are avalanche triodes, and when they are in the avalanche breakdown state, they are in the conducting state; when the avalanche breakdown ends, the triodes return to the cut-off state. Among them, triodes Q1, Q2, Q3, Q4, and Q5 in a group of positive sources conduct simultaneously; triodes Q11, Q12, Q13, Q14, and Q15 in a group of negative sources conduct simultaneously.

[0062] From t0 to t1, all triodes are in the cut-off state. At this time, the circuit is in the charging state, and the voltages across energy storage capacitors C1, C2, C3, C4, C5, C11, C12, C13, C14, and C15 are gradually charged from zero to the DC power supply voltage. The circuit of a single-polarity source in the circuit can be simplified to Fig. 2(a). At this time, the 5 energy storage capacitors in each single-polarity source are connected in parallel for charging, and the equivalent circuit is shown in Fig. 2(b).

[0063] At the moment of t1, the high-level trigger signal reaches the base of the negative-source triode Q11 through capacitor C07, inductor L4, and resistor R03 in the delay circuit. The triode Q11 undergoes avalanche breakdown and enters the conducting state. The energy storage capacitor C11 starts to discharge through the current-limiting resistor R24 and the triode Q11, and the generated current further causes the triode Q12 to undergo avalanche breakdown and conduct. And so on, this group of triodes Q11, Q12, Q13, Q14, and Q15 enter the conducting state in sequence; because the speed of avalanche breakdown and conduction is extremely fast, the whole process lasts for a very short time, and it can be regarded that the five triodes in this group conduct simultaneously at the moment of t1. At this time, because the resistance of the triode is very small when it conducts, far less than the current-limiting resistors R24, R25, R26, and R27 in the circuit, the discharging speed of the energy storage capacitor through the triode is much faster than other paths. Therefore, the discharging circuit at this time can be equivalent to Fig. 2(c), and the five energy storage capacitors become in series state, and output current through triodes Q11, Q12, Q13, Q14, and Q15 and output resistor Rout2, so that a negative pulse voltage is generated at the output end of the output resistor Rout2.

[0064] Similarly, at time t2, the high-level trigger signal reaches the base of the positive-source triode Q1 through the capacitor C06, inductor L3, and resistor R01 in the delay circuit. The five triodes Q1, Q2, Q3, Q4, and Q5 conduct simultaneously, and the five energy storage capacitors C1, C2, C3, C4, and C5 are connected in series to discharge. The current flows into the output resistor Rout1 through the triodes Q1, Q2, Q3, Q4, and Q5, and a positive pulse voltage is generated at the output terminal of the output resistor Rout1.

[0065] The negative pulse signal generated at time t1 and the positive pulse signal generated at time t2 reach the filter circuit through the inductors L5, L6, L7, and L8 in the isolation circuit, complete integration and post-processing, and finally reach the output terminal and are converted into a bipolar Gaussian pulse. After time t3, the circuit output is completed, and all triodes return to the cut-off state, and the circuit enters the charging state of the next cycle.

[0066] The present invention generates specific delay trigger signals through a delay circuit to control the sequential output of two unipolar sources, integrates the output pulses through an isolation circuit, and obtains the final output through processing by a filter circuit. By adjusting the size of the energy storage capacitors, the number of circuit stages, and the parameters of the filter circuit elements in the Marx circuit, the spectrum and waveform of the output pulse can be flexibly adjusted. This circuit can generate a relatively standard first-order Gaussian pulse signal, with a smooth main body of the signal, and the difference between the positive and negative peak values is less than 50%; the signal tail is very small; the circuit has a high stable trigger frequency, up to more than 300 kHz, far exceeding similar high-amplitude pulse source circuits; the circuit has high efficiency, low power consumption, and low heat generation. The present invention has the advantages of simple structure and easy control, and generates an excellent pulse waveform with high output efficiency, and is a product that can be flexibly applied to a variety of practical projects.

[0067] The term "consisting of" describing a combination should include the identified elements, components, parts, or steps and other elements, components, parts, or steps that do not substantially affect the basic novel features of the combination. Using the terms "comprising" or "including" to describe the combination of elements, components, parts, or steps here also contemplates embodiments consisting essentially of these elements, components, parts, or steps. Here, by using the term "may", it is intended to indicate that any attribute described as "may" included is optional.

[0068] Multiple elements, components, parts, or steps can be provided by a single integrated element, component, part, or step. Alternatively, a single integrated element, component, part, or step can be divided into multiple separate elements, components, parts, or steps. The disclosure of "a" or "an" used to describe an element, component, part, or step does not mean to exclude other elements, components, parts, or steps.

[0069] It should be understood that the above description is for illustrative purposes and not for limitation. Upon reading the above description, many embodiments and many applications beyond the provided examples will be apparent to those skilled in the art. Therefore, the scope of the present teachings should not be determined with reference to the above description, but rather should be determined with reference to the full scope of the foregoing claims and the equivalents thereof. For the sake of completeness, all articles and references, including patent applications and published announcements, are incorporated herein by reference. The omission of any aspect of the subject matter disclosed herein from the foregoing claims is not intended to abandon such subject matter, nor should it be considered that the applicant has not considered such subject matter to be a part of the disclosed inventive subject matter.

Claims

1. A frequency / waveform adjustable bipolar Gaussian pulse source, characterized in that: It includes a DC input circuit, a time-delay trigger circuit, a positive polarity pulse circuit, a negative polarity pulse circuit, an isolation circuit and a filter shaping circuit; the DC input circuit is connected to the input ends of the positive polarity pulse circuit and the negative polarity pulse circuit through the time-delay trigger circuit, the output ends of the positive polarity pulse circuit and the negative polarity pulse circuit are connected to the input end of the isolation circuit, the output end of the isolation circuit is connected to the first end of the filter shaping circuit, and the second end of the filter shaping circuit is connected to the output of the positive polarity pulse circuit; The positive polarity pulse circuit and the negative polarity pulse circuit both adopt Marx circuit based on triode avalanche effect; The DC input circuit comprises a DC power supply, and inductors are arranged between the DC power supply and the positive polarity pulse circuit, and between the DC power supply and the negative polarity pulse circuit.

2. A frequency / waveform adjustable bipolar Gaussian pulse source according to claim 1, characterized in that: The inductance value L of the inductor is: L=1.5CR 2 / 4, where C is the capacitance of the energy storage capacitor in the positive polarity pulse circuit and the negative polarity pulse circuit, and R is the resistance of the current limiting resistor in the positive polarity pulse circuit and the negative polarity pulse circuit.

3. A frequency / waveform adjustable bipolar Gaussian pulse source according to claim 1, characterized in that: The delay trigger circuit includes a capacitor C06, a first end of which is connected to a first end of a capacitor C07, and after being connected in series with an inductor L3 and a resistor R01, the capacitor C06 is connected to a first end of a resistor R02 and a base of a transistor Q1 in a positive polarity pulse circuit, and a second end of the resistor R02 is grounded; after being connected in series with an inductor L4 and a resistor R03, the capacitor C07 is connected to a first end of a resistor R04 and a base of a transistor Q11 in a negative polarity pulse circuit, and a second end of the resistor R04 is grounded.

4. A frequency / waveform adjustable bipolar Gaussian pulse source according to claim 3, characterized in that: The first end of the capacitor C06 and the first end of the capacitor C07 are both connected to the anode of the diode D2, and the cathode of the diode D2 is connected to the inductor.

5. The frequency / waveform adjustable bipolar Gaussian pulse source according to claim 1, characterized in that: The isolation circuit includes an inductor L5, an inductor L6, an inductor L7 and an inductor L8. The first end of a first parallel branch formed by connecting the inductor L5 and the inductor L6 in parallel is connected to the emitter of the transistor Q1, and the second end is connected to the first end of the output port Pout. The second end of the output port Pout is grounded. The inductor L7 and the inductor L8 are connected in parallel to form a second parallel branch, the first end of which is connected to the first end of the output resistor Rout2, and the second end is connected to the second end of the first parallel branch.

6. A frequency / waveform adjustable bipolar Gaussian pulse source according to claim 1, characterized in that: The filtering and shaping circuit is a first-order filtering circuit or a second-order filtering circuit.

7. A frequency / waveform adjustable bipolar Gaussian pulse source according to claim 6, characterized in that: The filtering and shaping circuit includes an inductor L9, a third parallel branch formed by connecting the inductor L9 and the capacitor C19 in parallel, a first end of which is grounded, a second end of which is connected to a first end of the inductor L12, a second end of which is connected to a first end of the capacitor C20, a second end of which is connected to a first end of the output port Pout, and a second end of the output port Pout is grounded.

8. The frequency / waveform adjustable bipolar Gaussian pulse source according to claim 1, characterized in that: The DC input circuit includes a DC power supply P0, one end of the DC power supply P0 is connected to the anode of the diode D1, the cathode of the diode D1 is connected to the first end of the capacitor C01, the first end of the inductor L2 and the first end of the inductor L1; the second end of the capacitor C01 is connected to the first end of the capacitor C02, the second end of the capacitor C02, the second end of the resistor R0 and one end of the DC power supply P0 are grounded.

9. A frequency / waveform adjustable bipolar Gaussian pulse source according to claim 8, characterized in that: A resistor R0 is connected between the cathode of the diode D1 and the second end of the capacitor C02.

10. The working method of the frequency / waveform adjustable bipolar Gaussian pulse source according to claim 1, characterized in that: include: During t0~t1, all transistors in the positive polarity pulse circuit and the negative polarity pulse circuit are in the cut-off state, the circuit is in the charging state, and the voltage across all energy storage capacitors is gradually charged from zero to the DC power supply voltage; At time t1, the high level of the trigger signal reaches the base of the first transistor in the negative polarity pulse circuit through the delay circuit, and the first transistor undergoes avalanche breakdown and enters the on state. The first energy storage capacitor begins to discharge through the current limiting resistor and the first transistor, and the generated current further triggers the avalanche breakdown and conduction of the second transistor. Similarly, the first to the Nth transistors enter the on state in turn. At this time, all the energy storage capacitors become connected in series, and output current through the transistors and the output resistor, so that a negative pulse voltage is generated at the output end of the output resistor. Similarly, at time t2, the high level of the trigger signal reaches the base of the first transistor in the positive polarity pulse circuit through the delay circuit, all transistors are turned on at the same time, all energy storage capacitors are discharged in series, and the current flows into the output resistor through the transistor, and a positive pulse voltage is generated at the output end of the output resistor; The negative pulse voltage generated at time t1 and the positive pulse voltage generated at time t2 reach the filter circuit through the isolation circuit, complete integration and post-processing, and finally reach the output end and are converted into bipolar Gaussian pulses; After time t3, the circuit output is completed and all transistors return to the cut-off state, and the circuit enters the charging state of the next cycle.

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