Dual-mode series nanosecond narrow pulse generator and method

Abstract

The application discloses a dual-mode series nanosecond narrow pulse generator, which comprises a light trigger module, a microstrip line, a photoconductive switch unit and a ceramic discharge tube, wherein the light trigger module operates independently, laser emitted by the light trigger module irradiates on the surface of the photoconductive switch unit and is used for exciting the photoconductive switch unit, and the photoconductive switch unit and the ceramic discharge tube are integrated in series on the microstrip line. The dual-mode series nanosecond narrow pulse generator solves the problems that the rising edge of the waveform of the output pulse in the linear mode of the traditional photoconductive switch is subject to the trigger laser pulse and the falling edge is subject to the material characteristics, simultaneously avoids the defects that the parasitic parameters of the pure gas switch are large and conduction is not controlled, and finally realizes the output of the dual-mode stable and ring-free nanosecond narrow pulse.

Description

Technical Field

[0001] This invention belongs to the fields of pulse power technology and ultrafast electronics technology, specifically relating to a dual-mode cascaded nanosecond narrow pulse generator, and also to a dual-mode cascaded nanosecond narrow pulse generation method. Background Technology

[0002] Ultrafast electrical pulse generation technology is a core supporting technology in the fields of pulse power, ultrafast electronics, laser optoelectronics and precision testing. It features steep rise time, narrow pulse width, high instantaneous power and high time resolution, and is widely used in electro-optic modulator driving, ultrafast laser pulse selection, transient plasma excitation, high-speed semiconductor device testing, ultrawideband radar excitation and bioelectric stimulation.

[0003] Currently, conventional technologies for achieving nanosecond-level electrical pulses mainly include semiconductor switches, avalanche transistors, step recovery diodes, photoconductive switches, and traditional gas switches. Among them, electrically triggered solid-state switches are limited by gate / base parasitic capacitance and drive loop inductance, with pulse rise times typically ranging from a few nanoseconds to tens of nanoseconds, and pulse fall times largely relying on the device's natural turn-off, resulting in noticeable waveform tailing and ringing phenomena.

[0004] Photoconductive switches offer advantages such as fast response speed, low timing jitter, and high optical isolation. However, the output electrical pulse waveform in linear mode is limited by the waveform of the triggering optical pulse and the material properties. If ultrashort optical pulses (such as femtosecond lasers) are used for triggering, the laser becomes too large and expensive. In nonlinear mode, the semiconductor switch needs to withstand very high voltages, and the output electrical pulse has a long tail. Even in quenching mode, it is difficult to achieve adjustable output of ultrashort electrical pulses of a few nanoseconds.

[0005] Traditional gas switches are mostly used in high-voltage pulse systems ranging from kilovolts to megavolts, primarily for pulse steepening or high-voltage conduction. They are rarely used in medium- and low-voltage scenarios where the narrow pulse edges of several nanoseconds require precise shaping. The conduction of a gas switch depends mainly on the bias voltage, making it extremely difficult to precisely control the timing of its output electrical pulse. Gas switches have a narrow operating range near their withstand voltage. Below their withstand voltage, the switch does not trigger; when the bias voltage is too high, the gas flows through, preventing the generation of an electrical pulse. They only have a working space within an extremely narrow range near their withstand voltage, and the pulse width of the output electrical pulse is primarily limited by the energy storage device.

[0006] In summary, existing standalone gas switch and photoconductive switch technologies struggle to achieve adjustable, nanosecond-level stable, ringing-free electrical pulse waveforms. They generally suffer from drawbacks such as uncontrollable triggering, large waveform oscillations, weak parameter adjustment capabilities, large size, and high cost. To a certain extent, they cannot meet the stringent requirements for pulse waveform quality in ultrafast photoelectric systems, high-speed testing, and precision transient detection. Summary of the Invention

[0007] The first objective of this invention is to provide a dual-mode series nanosecond narrow pulse generator, which solves the problems that the rising edge of the output pulse waveform of a traditional photoconductive switch in linear mode is limited by the trigger laser pulse and the falling edge is limited by the material properties. At the same time, it avoids the defects of pure gas switches, such as large parasitic parameters and uncontrolled conduction. Ultimately, it achieves stable dual-mode, ringing-free output of nanosecond narrow pulses.

[0008] The second objective of this invention is to provide a dual-mode tandem nanosecond narrow pulse generation method.

[0009] The first technical solution adopted in this invention is a dual-mode series nanosecond narrow pulse generator, which includes an optical trigger module, a microstrip line, a photoconductive switch unit, and a ceramic discharge tube. The optical trigger module operates independently, and the laser emitted by the optical trigger module irradiates the surface of the photoconductive switch unit to excite the photoconductive switch unit. The photoconductive switch unit and the ceramic discharge tube are integrated in series on the microstrip line.

[0010] The invention is further characterized in that: The optical triggering module includes at least three pulsed laser emission branches. Each pulsed laser emission branch includes a driver circuit board, a pulsed laser diode, and an optical fiber connected in sequence. The driver circuit board controls the pulsed laser diode using a TTL signal. Multiple lasers are coupled through the optical fiber to synchronously irradiate the photoconductive switch unit. The trigger light energy is changed by adjusting the output light power of the optical fiber.

[0011] The microstrip line includes a metal backplate, a dielectric layer, and three signal lines arranged sequentially from top to bottom; the photoconductive switch unit and the ceramic discharge tube are connected in series on the upper surface of the dielectric layer through the three signal lines.

[0012] The metal backplane is made of copper; the dielectric layer is made of Rogers RO4350B; the dielectric layer is rectangular in shape, with a length of 6cm ± 0.5cm and a width of 3cm-9cm; the signal line is made of copper and has a width of 3mm ± 0.5mm.

[0013] The photoconductive switch unit includes a semi-insulated gallium arsenide photoconductive switch. Two electrodes are disposed on the upper surface of the semi-insulated gallium arsenide photoconductive switch. The two electrodes are located in the gap between two signal lines and are respectively connected to the adjacent signal line. The end of the optical fiber is located above the semi-insulated gallium arsenide photoconductive switch, and the laser emitted by the optical fiber irradiates the surface of the semi-insulated gallium arsenide photoconductive switch.

[0014] The electrodes are nickel-gold electrodes; the electrodes are rectangular in shape, with a width of 3mm±0.5mm and a length of 6mm±0.5mm. The right angles in the rectangle are chamfered, and the corresponding fillet radius after chamfering is 0.5mm±0.05mm; the distance between the two electrodes is 3mm±0.5mm; the semi-insulating gallium arsenide photoconductive switch is rectangular in shape, with a width of 8mm±0.5mm and a length of 10mm±0.5mm.

[0015] The ceramic discharge tube uses EPCOS ceramic gas discharge tube A71-H25X.

[0016] The semi-insulated gallium arsenide photoconductive switch is positioned near the input end of the microstrip line, and the ceramic discharge tube is positioned near the output end of the microstrip line. The horizontal distance between the input end of the semi-insulated gallium arsenide photoconductive switch and the SMA interface of the microstrip line input end is 20mm ± 0.5mm; the distance between the output end of the semi-insulated gallium arsenide photoconductive switch and the input end of the ceramic discharge tube is 10mm ± 0.5mm.

[0017] The second technical solution adopted in this invention is a dual-mode series nanosecond narrow pulse generation method. The generator described above is used as follows: when the required frequency is kHz or below, a TTL signal control mode is used: an external bias voltage is applied to the combination switch, and a TTL level signal is used to make the pulse laser diode output laser. The laser irradiates the surface of the semi-insulating gallium arsenide photoconductive switch. The bias voltage is adjusted below the self-breakdown voltage to control the amplitude of the output electrical pulse. When the usage requirement is within the MHz range, the self-trigger mode is used: an external bias voltage is applied to the self-breakdown value of the combination switch, and the bias voltage is adjusted when it is greater than the self-breakdown voltage to regulate the frequency of the output electrical pulse.

[0018] The invention is further characterized in that: The combination switch consists of a photoconductive switch unit, a ceramic discharge tube, and a signal line connecting the two.

[0019] The beneficial effects of this invention are: (1) Synergistic effect of device combination: This solution not only overcomes the dependence of the waveform of the output electrical pulse of the semi-insulating gallium arsenide photoconductive switch in linear mode on the trigger optical pulse, but also overcomes the defect that the ceramic discharge tube trigger cannot be precisely controlled by the TTL signal and the output pulse width is relatively wide, providing a unique composite switching technology. It can output electrical pulses with a pulse width shorter than the trigger optical pulse, achieve precise control of the TTL signal, and improve the overall withstand voltage capability of the switch, ultimately achieving stable dual-mode output of stable, ring-free nanosecond-level ultra-short electrical pulses.

[0020] (2) Excellent waveform quality: The present invention uses a three-way laser synchronous triggering semi-insulated gallium arsenide photoconductive switch to improve the stability and consistency of the primary electrical pulse. It also utilizes the active cut-off function of the ceramic gas switch and combines the impedance matching optimization of the microstrip line to make the output electrical pulse narrow, without ringing or overshoot, and with good waveform consistency.

[0021] (3) Dual-mode operation: Traditional pulse generators can only select one of two modes: TTL external trigger single pulse or high-voltage self-excited oscillation pulse. This invention has a single circuit that is compatible with both operating modes. Moreover, by changing the voltage withstand of the ceramic tube, a wide range of voltage withstand values ​​can be achieved, solving the pain points of fixed parameters and single function of existing equipment, and bringing significant engineering progress.

[0022] (4) In self-trigger mode, nanosecond electrical pulses with a repetition frequency of MHz are output. The operating voltage of the combination switch is higher than that of the individual ceramic gas switch, and the self-trigger voltage operating range of the combination switch is greater than that of the individual ceramic gas switch.

[0023] (5) Economical price and strong practicality: This device uses a pulsed laser diode as the trigger source. The device has a compact structure, reliable triggering, economical price, long service life, and adjustable electrical pulse amplitude. It can be widely used in many fields such as electro-optic modulator driving, ultrafast laser pulse selection, and high-speed semiconductor device testing, and has extremely high engineering application value. The generator of this invention solves the problem that the rising edge of the output pulse waveform of the traditional photoconductive switch in linear mode is limited by the trigger laser pulse and the falling edge is limited by the material properties. At the same time, it avoids the defects of large parasitic parameters and uncontrolled conduction of pure gas switches, and finally realizes stable dual-mode output of nanosecond narrow pulses without ringing. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of the dual-mode tandem nanosecond narrow pulse generator of the present invention; Figure 2 This is a performance test circuit diagram of the dual-mode cascaded nanosecond narrow pulse generator of the present invention; Figure 3 In Example 1, when the withstand voltage of the ceramic gas discharge tube in the combination switch is 3000V, the combination switch outputs an electrical pulse waveform under a bias voltage of 3516V. Figure 4 In Example 1, when the withstand voltage of the ceramic gas discharge tube in the combination switch is 3000V, the amplitude, rising edge, falling edge, and pulse width of the output electrical pulse of the combination switch vary with the bias voltage. Figure 5 This is a comparison diagram of typical electrical pulse waveforms output by a single gas switch, a single semi-insulating gallium arsenide photoconductive switch, and a combination switch in Example 1. Figure 6 In Example 2, when the withstand voltage of the ceramic gas discharge tube in the combination switch is 1000V, the combination switch outputs an electrical pulse waveform under a bias voltage of 978V. Figure 7 In Example 3, when the withstand voltage of the ceramic gas discharge tube in the combination switch is 500V, the combination switch outputs an electrical pulse waveform under a bias voltage of 533V. Figure 8 In Example 4, when the withstand voltage of the ceramic gas discharge tube in the combination switch is 150V, the combination switch outputs an electrical pulse waveform under a bias voltage of 363V. Figure 9 In Example 5, when the withstand voltage of the ceramic gas discharge tube in the combination switch is 500V, the waveform of the electrical pulse output by the combination switch in the 3000V bias voltage self-trigger mode is shown. Figure 10 In Example 5, when the withstand voltage of the ceramic gas discharge tube in the combination switch is 500V, the relationship between the repetition period of the electrical pulse output by the combination switch under different bias voltages and the bias voltage is shown.

[0025] In the diagram, 1. Metal backplate, 2. Dielectric layer, 3. Signal line, 4. Anode, 5. Optical fiber, 6. Semi-insulated gallium arsenide photoconductive switch, 7. Ceramic discharge tube, 8. Driver circuit board, 9. Pulsed laser diode, 10. Oscilloscope, 11. Dual-mode series nanosecond narrow pulse generator, 12. Attenuator, 13. Protective resistor, 14. High voltage DC power supply. Detailed Implementation

[0026] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0027] This invention provides a dual-mode cascaded nanosecond narrow pulse generator, such as... Figure 1 As shown, it includes an optical trigger module, a microstrip line, a photoconductive switch unit, and a ceramic discharge tube 7. The optical trigger module operates independently, and the laser emitted by the optical trigger module irradiates the surface of the photoconductive switch unit to excite the photoconductive switch unit. The photoconductive switch unit and the ceramic discharge tube 7 are integrated in series on the microstrip line.

[0028] The optical triggering module includes at least three pulsed laser emission branches. Each pulsed laser emission branch includes a driver circuit board 8, a pulsed laser diode 9, and an optical fiber 5 connected in sequence. The driver circuit board 8 controls the three sets of pulsed laser diodes 9 using TTL signals. Multiple lasers are coupled and synchronously illuminate the photoconductive switch unit via the optical fiber 5. The trigger light energy is changed by adjusting the output light power of the optical fiber 5. Each pulsed laser emission branch is equipped with an independent driver circuit board 8. The three TTL trigger signals are synchronously connected to each driver circuit board to achieve synchronous emission of multi-channel lasers.

[0029] The driver circuit board 8 is a 905nm pulse driver circuit board from Shenzhen RELTE Optoelectronic Technology Co., Ltd., which is powered by 12V and 38V power supplies. Three TTL signals synchronously provide trigger signals to the three driver circuit boards 8, so that the three pulse laser diodes 9 can emit light synchronously and trigger the semi-insulated gallium arsenide photoconductive switch 6 synchronously. This method can improve the reliability and stability of the pulse generator triggering.

[0030] The PLD905-180W pulsed laser diode is used, with fiber-coupled output. The output wavelength is 905nm and the pulse width of the output light pulse is 40ns. The pulsed laser is coupled into the optical fiber, which has a diameter of 200μm. Three TTL signals are used as signal sources to simultaneously control the emission of three pulsed laser diodes, improving the stability and reliability of triggering, realizing synchronous emission of the three pulsed laser diodes, achieving stable triggering of photoelectric conversion, and ensuring low jitter of the output signal.

[0031] The microstrip line includes a metal backplate 1, a dielectric layer 2, and three signal lines 3 arranged sequentially from top to bottom; a photoconductive switch unit and a ceramic discharge tube 7 are connected in series on the upper surface of the dielectric layer 2 via the three signal lines 3. The metal backplate 1 is grounded, and the signal lines 3 are anode signal lines.

[0032] The metal backplate 1 is made of copper; a high-frequency, low-loss board material is used as the dielectric, the dielectric layer 2 is made of Rogers RO4350B; the dielectric layer 2 is rectangular in shape, with a length of 6cm±0.5cm and a width of 3cm-9cm, and the signal line 3 is made of copper with a width of 3mm±0.5mm.

[0033] The photoconductive switch unit includes a semi-insulated gallium arsenide photoconductive switch 6. Two electrodes 4 are disposed on the upper surface of the semi-insulated gallium arsenide photoconductive switch 6. The two electrodes 4 are located in the gap between two signal lines 3. The two electrodes 4 are respectively connected to the adjacent signal line 3. The end of the optical fiber 5 is located above the semi-insulated gallium arsenide photoconductive switch 6. The laser emitted by the optical fiber 5 irradiates the surface of the semi-insulated gallium arsenide photoconductive switch 6.

[0034] Under the action of the optical triggering module, the semi-insulating gallium arsenide photoconductive switch 6 quickly changes from a high-resistance state to a low-resistance state, generating an initial fast-edge electrical pulse, which provides a basis for subsequent pulse shaping.

[0035] Electrode 4 is a nickel-gold electrode; the shape of electrode 4 is rectangular, with a width of 3mm±0.5mm and a length of 6mm±0.5mm. The right angles in the rectangle are chamfered, and the corresponding rounded corner radius after chamfering is 0.5mm±0.05mm; the distance between the two electrodes 4 is 3mm±0.5mm; the semi-insulating gallium arsenide photoconductive switch 6 is rectangular, with a width of 8mm±0.5mm and a length of 10mm±0.5mm.

[0036] The ceramic discharge tube 7 uses an EPCOS ceramic gas discharge tube A71-H25X. Different withstand voltage values ​​can be selected for the ceramic gas discharge tubes, such as 150V, 300V, 500V, 1000V, and 3000V, thereby changing the operating voltage range and the amplitude of the output electrical pulse, but having little effect on the rising edge, falling edge, and pulse width of the output electrical pulse. Different withstand voltage values ​​correspond to output electrical pulses with different parameters. A gas discharge type switch is used to steepen the leading edge and actively truncate the trailing edge of the electrical pulse output from the semi-insulated gallium arsenide photoconductive switch, further suppressing pulse ringing and overshoot.

[0037] The semi-insulated gallium arsenide photoconductive switch 6 is positioned near the input end of the microstrip line, and the ceramic discharge tube 7 is positioned near the output end of the microstrip line; the horizontal distance between the input end of the semi-insulated gallium arsenide photoconductive switch 6 and the SMA interface of the microstrip line input end is 20mm±0.5mm; the distance between the output end of the semi-insulated gallium arsenide photoconductive switch 6 and the input end of the ceramic discharge tube 7 is 10mm±0.5mm.

[0038] The high-voltage access port is provided with a preset wiring length from the semi-insulated gallium arsenide photoconductive switch. The semi-insulated gallium arsenide photoconductive switch 6 and the ceramic discharge tube 7 are connected by a signal line 3. An SMA signal output interface is led out from the end of the circuit after the ceramic discharge tube 7.

[0039] This invention also provides a dual-mode cascaded nanosecond narrow pulse generation method, using the above-mentioned generator, specifically: When the required frequency is kHz or below, the TTL signal control mode is used. The operation is as follows: an external bias voltage is applied to the combination switch, and the TTL level signal is used to control the pulse laser diode 9 to output laser through the driver circuit board 8. The laser shines on the surface of the semi-insulated gallium arsenide photoconductive switch 6 through the optical fiber 5, causing the semi-insulated gallium arsenide photoconductive switch 6 to quickly switch from high resistance to low resistance to generate an initial electrical pulse. The ceramic discharge tube 7 connected in series steepens the leading edge and actively cuts off the trailing edge of the initial electrical pulse. With the impedance matching of the microstrip line, a ringing-free nanosecond pulse output is achieved, which can output an ultra-short electrical pulse. Then, the bias voltage is adjusted according to the actual needs at a level lower than the self-breakdown voltage to control the amplitude of the output electrical pulse. When the usage requirement is within the MHz range, the self-trigger mode is used. The operation method is as follows: apply an external bias voltage to the self-breakdown value of the combination switch, that is, output a MHz electrical pulse at the load end, and then adjust the bias voltage according to the requirement at a voltage greater than the self-breakdown voltage to control the frequency of the output electrical pulse.

[0040] The combination switch consists of a photoconductive switch unit, a ceramic discharge tube 7, and a signal line 3 connecting the two.

[0041] The generator of this invention has two working modes: (1) TTL signal control mode, which uses TTL signal to control the pulse laser diode 9 to trigger the output of nanosecond-level electrical pulses, realizing the output of nanosecond-level ultrashort electrical pulses shorter than the trigger light pulses by precise control of TTL signal. The amplitude of the output electrical pulse is adjustable from 8.48V to 109V, the pulse width is 3.4ns to 10ns, the rising edge and falling edge are 3ns to 10ns, and it is stable without ringing; (2) Self-triggering mode: self-triggering is achieved under high voltage, outputting nanosecond electrical pulses with a repetition frequency of MHz, and the output frequency is adjustable within a certain range.

[0042] Self-triggered mode: This mode outputs ultra-short electrical pulses with a pulse width of 5ns at a certain frequency without the need for optical pulse triggering. The repetition frequency of the output electrical pulses increases with the increase of the bias voltage.

[0043] In self-trigger mode, the operating voltage of the photoconductive switch unit and the ceramic discharge tube 7 is higher than the withstand voltage of the ceramic discharge tube 7 alone, and the self-trigger voltage operating range of the photoconductive switch unit and the ceramic discharge tube 7 is greater than the operating range of the ceramic discharge tube 7 alone. In self-trigger mode, ultra-short electrical pulses on the order of nanoseconds with adjustable repetition period can be output.

[0044] In summary, by using an impedance matching network to match the characteristic impedance of the load and the pulse generation circuit, the efficient transmission of pulse energy is ensured, resulting in the final output of nanosecond electrical pulses of different amplitudes.

[0045] like Figure 2The diagram shown is a circuit diagram for testing the dual-mode series-connected nanosecond narrow pulse generator of the present invention under DC bias voltage. It includes a protection resistor 13 connected in series, a dual-mode series-connected nanosecond narrow pulse generator 11, an attenuator 12, and an oscilloscope 10; it also includes a high-voltage power supply 14; the signal line 3 of the microstrip line in the dual-mode series-connected nanosecond narrow pulse generator 11 is connected to the positive terminal of the high-voltage power supply 14, and the negative terminal of the high-voltage power supply 14 is connected to the backplane 1 of the microstrip line in the dual-mode series-connected nanosecond narrow pulse generator 11. The dual-mode series-connected nanosecond narrow pulse generator 11, the attenuator 12, and the oscilloscope 10 are all connected by a 50-ohm coaxial cable.

[0046] The high-voltage power supply powers the photoconductive switch unit and the ceramic discharge tube 7 via a 1MΩ-10MΩ protective resistor 13. The protective resistor 13 protects the power supply. After passing through the photoconductive switch unit and the ceramic discharge tube 7, the current enters the oscilloscope 10 via a 40dB attenuator 12 (attenuated by 100 times). The entire circuit is connected using a 50Ω coaxial cable.

[0047] Example 1 TTL signal control mode: In the dual-mode series nanosecond narrow pulse generator 11, electrode 4 is a rectangle with a width of 3mm and a length of 6mm. The right angles of the rectangle are chamfered, and the corresponding rounded corner radius after chamfering is 0.5mm. The distance between the two electrodes 4 is 3mm. The semi-insulated gallium arsenide photoconductive switch 6 is a rectangle with a width of 8mm and a length of 10mm. The dielectric layer 2 has a length of 6cm and a width of 6cm. The signal line between the output terminal of the semi-insulated gallium arsenide photoconductive switch 6 and the input terminal of the ceramic discharge tube 7 has a width of 3mm and a length of 10mm. The horizontal distance between the input terminal of the semi-insulated gallium arsenide photoconductive switch 6 and the SMA interface of the microstrip line input terminal is 20mm. The distance between the output terminal of the semi-insulated gallium arsenide photoconductive switch 6 and the input terminal of the ceramic discharge tube 7 is 10mm. The photoconductive switch unit, the ceramic discharge tube 7, and the signal line connecting the two constitute a combined switch. The withstand voltage of the ceramic discharge tube 7 is 3000V.

[0048] like Figure 3 The figure shows the waveforms of multiple output electrical pulses at a bias voltage of 3516V. The average amplitude of the output electrical pulses is 107.33V, with a standard deviation of 3.47V and a variance of 10.82. The average rising time is 2.6ns, with a standard deviation of 0.089ns and a variance of 0.008. The average falling time is 3.24ns, with a standard deviation of 0.08ns and a variance of 0.006. The average pulse width is 3.52ns, with a standard deviation of 0.1327ns and a variance of 0.0176. It can be seen that this scheme is not only simple in structure and economical in price, but also produces output electrical pulses with good waveform stability, narrow pulse width, no ringing, and no overshoot.

[0049] like Figure 4 The figure shows the relationship between the output electrical pulse amplitude, rise time, fall time, and pulse width and the bias voltage under this combination of conditions. The output electrical pulse amplitude, rise time, fall time, and pulse width are the average values ​​of multiple measurements. The output electrical pulse amplitude ranges from 77.3V to 109.9V; the rise time ranges from 2.44ns to 2.82ns; the fall time ranges from 3.16ns to 4.05ns; and the pulse width ranges from 3.52ns to 4.4ns. It can be seen that this scheme not only produces a stable waveform for the output electrical pulse light, but also allows the parameters to be adjusted within a certain range.

[0050] like Figure 5 The diagram shows a comparison of typical waveforms output by a single ceramic discharge tube 7, a single photoconductive switch unit, and a combined switch. The waveform of the electrical pulse output by a single photoconductive switch unit, triggered by three pulsed laser diodes and with a bias voltage of 1000V, has a pulse width consistent with the pulsed laser light emitted by the laser diodes, approximately 40ns. The waveform of the electrical pulse output by a single ceramic gas discharge tube, under the same microstrip line structure and with a bias voltage of 4000V and the gas switch self-breaking down, has a pulse width of approximately 80ns, and can only be controlled by adjusting the bias voltage, not by a TTL signal. The combined switch technology, under TTL signal control, outputs an electrical pulse with a pulse width of approximately 5ns. Figure 5 As can be seen, the electrical pulse output by this invention not only achieves precise control of the output signal, but also has a pulse width that is much shorter than the ultra-short electrical pulse output of the two device characteristics, thus realizing the synergistic effect of the device combination.

[0051] Example 2 TTL signal control mode: The difference from Example 1 is that a ceramic discharge tube with a withstand voltage of 1000V is used. For example... Figure 6 The figure shows the waveform of the output electrical pulse under a bias voltage of 978V. The average amplitude of the output electrical pulse is 10.78V, the average rise time is 8.8ns, the average fall time is 5.7ns, and the average pulse width is 9.04ns. As can be seen from the figure, the waveform of the output electrical pulse is very stable, demonstrating the stability and reliability of this scheme.

[0052] Example 3 TTL signal control mode: In the dual-mode series nanosecond narrow pulse generator 11, electrode 4 is a rectangle of 3mm (width) × 6mm (length), with chamfered corners and a corresponding fillet radius of 0.5mm. The distance between the two electrodes 4 is 3mm. The semi-insulated gallium arsenide photoconductive switch 6 is a rectangle of 8mm (width) × 10mm (length). The dielectric layer 2 is 6cm long and 3cm wide. The signal line between the output terminal of the semi-insulated gallium arsenide photoconductive switch 6 and the input terminal of the ceramic discharge tube 7 is 3mm wide and 10mm long. The horizontal distance between the input terminal of the semi-insulated gallium arsenide photoconductive switch 6 and the SMA interface of the microstrip line input terminal is 20mm. The distance between the output terminal of the semi-insulated gallium arsenide photoconductive switch 6 and the input terminal of the ceramic discharge tube 7 is 10mm. The photoconductive switch unit, the ceramic discharge tube 7, and the signal line connecting them constitute a combined switch. The withstand voltage of the ceramic discharge tube 7 is 500V.

[0053] like Figure 7 The figure shows the waveforms of multiple output electrical pulses when the bias voltage of the combination switch is 533V. The average amplitude of the output electrical pulse is 12.46V, the average rise time is 4.42ns, the average fall time is 2.65ns, and the average pulse width is 4.1ns. This embodiment not only demonstrates the economy and reliability of the proposed solution, but also illustrates the replaceability of the gas discharge tube and the stability of the output electrical pulse.

[0054] Example 4 TTL signal control mode: In the dual-mode series nanosecond narrow pulse generator 11, electrode 4 is a rectangle of 3mm (width) × 6mm (length), with chamfered corners and a corresponding fillet radius of 0.5mm. The distance between the two electrodes 4 is 3mm. The semi-insulated gallium arsenide photoconductive switch 6 is a rectangle of 8mm (width) × 10mm (length). The dielectric layer 2 is 6cm long and 5cm wide. The signal line between the output terminal of the semi-insulated gallium arsenide photoconductive switch 6 and the input terminal of the ceramic discharge tube 7 is 3mm wide and 10mm long. The horizontal distance between the input terminal of the semi-insulated gallium arsenide photoconductive switch 6 and the SMA interface of the microstrip line input terminal is 20mm. The distance between the output terminal of the semi-insulated gallium arsenide photoconductive switch 6 and the input terminal of the ceramic discharge tube 7 is 10mm. The photoconductive switch unit, the ceramic discharge tube 7, and the signal line connecting them constitute a combined switch. The withstand voltage of the ceramic discharge tube 7 is 150V.

[0055] like Figure 8The figure shows the waveforms of multiple output electrical pulses when the bias voltage of the combination switch is 363V. The average amplitude of the output electrical pulse is 8.48V, the average rise time is 3.14ns, the average fall time is 3.06ns, and the average pulse width is 4.08ns. This embodiment demonstrates that the combination switch technology can significantly improve the withstand voltage capability of the gas discharge tube, and its output electrical pulse capability remains stable even when the ceramic gas discharge tube is modified.

[0056] Example 5 Self-triggering mode: In the dual-mode series nanosecond narrow pulse generator 11, electrode 4 is a rectangle of 3mm (width) × 6mm (length), with chamfered corners and a corresponding fillet radius of 0.5mm. The distance between the two electrodes 4 is 3mm. The semi-insulated gallium arsenide photoconductive switch 6 is a rectangle of 8mm (width) × 10mm (length). The dielectric layer 2 is 6cm long and 4cm wide. The signal line between the output terminal of the semi-insulated gallium arsenide photoconductive switch 6 and the input terminal of the ceramic discharge tube 7 is 3mm wide and 10mm long. The horizontal distance between the input terminal of the semi-insulated gallium arsenide photoconductive switch 6 and the SMA interface of the microstrip line input terminal is 20mm. The distance between the output terminal of the semi-insulated gallium arsenide photoconductive switch 6 and the input terminal of the ceramic discharge tube 7 is 10mm. The photoconductive switch unit, the ceramic discharge tube 7, and the signal line connecting them constitute a combined switch. The withstand voltage of the ceramic discharge tube 7 is 500V.

[0057] like Figure 9 As shown, the output electrical pulse has a period of 24.927μs, an amplitude of 10.38V, a rise time of 4ns, a fall time of 4ns, and a pulse width of 5ns.

[0058] like Figure 10 As shown, the repetition period gradually decreases while the repetition frequency gradually increases with increasing bias voltage. When the bias voltage is 1000V, the repetition period is 220μs. With further increases in bias voltage, when the bias voltage reaches 3000V, the repetition period becomes 24.927μs. Moreover, the pulse width remains consistently at 5ns throughout the voltage variation. This embodiment demonstrates that: firstly, the self-triggering operating range of the ceramic gas switch is expanded; secondly, the frequency of the combined switch output in self-triggering mode is adjustable within a certain range; thirdly, the switch combination produces a synergistic effect, resulting in an output electrical pulse superior to that of a single gas switch; and finally, it achieves a nanosecond narrow pulse output with no ringing in the self-triggering mode of the combined switch.

[0059] Example 6 The dual-mode tandem nanosecond narrow pulse generator includes an optical trigger module, a microstrip line, a photoconductive switch unit, and a ceramic discharge tube. The optical trigger module operates independently, and the laser emitted by the optical trigger module irradiates the surface of the photoconductive switch unit to excite the photoconductive switch unit. The photoconductive switch unit and the ceramic discharge tube are integrated in series on the microstrip line.

[0060] The optical triggering module includes at least three pulsed laser emission branches. Each pulsed laser emission branch includes a driver circuit board, a pulsed laser diode, and an optical fiber connected in sequence. The driver circuit board controls the pulsed laser diode using a TTL signal. Multiple lasers are coupled through the optical fiber to synchronously irradiate the photoconductive switch unit. The trigger light energy is changed by adjusting the output light power of the optical fiber.

[0061] The microstrip line includes a metal backplate, a dielectric layer, and three signal lines arranged sequentially from top to bottom; the photoconductive switch unit and the ceramic discharge tube are connected in series on the upper surface of the dielectric layer through the three signal lines.

[0062] The metal backplate is made of copper; the dielectric layer is made of Rogers RO4350B; the dielectric layer is rectangular in shape, with a length of 6cm and a width of 7cm; the signal line is made of copper and has a width of 3mm.

[0063] The photoconductive switch unit includes a semi-insulated gallium arsenide photoconductive switch. Two electrodes are disposed on the upper surface of the semi-insulated gallium arsenide photoconductive switch. The two electrodes are located in the gap between two signal lines and are respectively connected to the adjacent signal line. The end of the optical fiber is located above the semi-insulated gallium arsenide photoconductive switch, and the laser emitted by the optical fiber irradiates the surface of the semi-insulated gallium arsenide photoconductive switch.

[0064] The electrodes are nickel-gold electrodes; the electrodes are rectangular in shape, with a width of 3mm and a length of 6mm. The right angles in the rectangle are chamfered, and the corresponding rounded corner radius after chamfering is 0.5mm; the distance between the two electrodes is 3mm; the semi-insulating gallium arsenide photoconductive switch is rectangular in shape, with a width of 8mm and a length of 10mm.

[0065] The ceramic discharge tube uses EPCOS ceramic gas discharge tube A71-H25X.

[0066] The semi-insulated gallium arsenide photoconductive switch is positioned near the input end of the microstrip line, and the ceramic discharge tube is positioned near the output end of the microstrip line. The horizontal distance between the input end of the semi-insulated gallium arsenide photoconductive switch and the SMA interface of the microstrip line input end is 20mm. The distance between the output end of the semi-insulated gallium arsenide photoconductive switch and the input end of the ceramic discharge tube is 10mm.

[0067] Example 7 The dual-mode tandem nanosecond narrow pulse generator includes an optical trigger module, a microstrip line, a photoconductive switch unit, and a ceramic discharge tube. The optical trigger module operates independently, and the laser emitted by the optical trigger module irradiates the surface of the photoconductive switch unit to excite the photoconductive switch unit. The photoconductive switch unit and the ceramic discharge tube are integrated in series on the microstrip line.

[0068] The optical triggering module includes at least three pulsed laser emission branches. Each pulsed laser emission branch includes a driver circuit board, a pulsed laser diode, and an optical fiber connected in sequence. The driver circuit board controls the pulsed laser diode using a TTL signal. Multiple lasers are coupled through the optical fiber to synchronously irradiate the photoconductive switch unit. The trigger light energy is changed by adjusting the output light power of the optical fiber.

[0069] The microstrip line includes a metal backplate, a dielectric layer, and three signal lines arranged sequentially from top to bottom; the photoconductive switch unit and the ceramic discharge tube are connected in series on the upper surface of the dielectric layer through the three signal lines.

[0070] The metal backplate is made of copper; the dielectric layer is made of Rogers RO4350B; the dielectric layer is rectangular in shape, with a length of 5.5cm and a width of 3cm; the signal line is made of copper and has a width of 2.5mm.

[0071] The photoconductive switch unit includes a semi-insulated gallium arsenide photoconductive switch. Two electrodes are disposed on the upper surface of the semi-insulated gallium arsenide photoconductive switch. The two electrodes are located in the gap between two signal lines and are respectively connected to the adjacent signal line. The end of the optical fiber is located above the semi-insulated gallium arsenide photoconductive switch, and the laser emitted by the optical fiber irradiates the surface of the semi-insulated gallium arsenide photoconductive switch.

[0072] The electrodes are nickel-gold electrodes; the shape of the electrodes is rectangular, with a width of 2.5mm and a length of 5.5mm. The right angles in the rectangle are chamfered, and the corresponding rounded corner radius after chamfering is 0.45mm; the distance between the two electrodes is 2.5mm; the semi-insulating gallium arsenide photoconductive switch is rectangular, with a width of 7.5mm and a length of 9.5mm.

[0073] The ceramic discharge tube uses EPCOS ceramic gas discharge tube A71-H25X.

[0074] The semi-insulated gallium arsenide photoconductive switch is positioned near the input end of the microstrip line, and the ceramic discharge tube is positioned near the output end of the microstrip line. The horizontal distance between the input end of the semi-insulated gallium arsenide photoconductive switch and the SMA interface of the microstrip line input end is 19.5 mm; the distance between the output end of the semi-insulated gallium arsenide photoconductive switch and the input end of the ceramic discharge tube is 9.5 mm.

[0075] Example 8 The dual-mode tandem nanosecond narrow pulse generator includes an optical trigger module, a microstrip line, a photoconductive switch unit, and a ceramic discharge tube. The optical trigger module operates independently, and the laser emitted by the optical trigger module irradiates the surface of the photoconductive switch unit to excite the photoconductive switch unit. The photoconductive switch unit and the ceramic discharge tube are integrated in series on the microstrip line.

[0076] The optical triggering module includes at least three pulsed laser emission branches. Each pulsed laser emission branch includes a driver circuit board, a pulsed laser diode, and an optical fiber connected in sequence. The driver circuit board controls the pulsed laser diode using a TTL signal. Multiple lasers are coupled through the optical fiber to synchronously irradiate the photoconductive switch unit. The trigger light energy is changed by adjusting the output light power of the optical fiber.

[0077] The microstrip line includes a metal backplate, a dielectric layer, and three signal lines arranged sequentially from top to bottom; the photoconductive switch unit and the ceramic discharge tube are connected in series on the upper surface of the dielectric layer through the three signal lines.

[0078] The metal backplate is made of copper; the dielectric layer is made of Rogers RO4350B; the dielectric layer is rectangular in shape, with a length of 6.5cm and a width of 9cm; the signal line is made of copper and has a width of 3.5mm.

[0079] The photoconductive switch unit includes a semi-insulated gallium arsenide photoconductive switch. Two electrodes are disposed on the upper surface of the semi-insulated gallium arsenide photoconductive switch. The two electrodes are located in the gap between two signal lines and are respectively connected to the adjacent signal line. The end of the optical fiber is located above the semi-insulated gallium arsenide photoconductive switch, and the laser emitted by the optical fiber irradiates the surface of the semi-insulated gallium arsenide photoconductive switch.

[0080] The electrodes are nickel-gold electrodes; the shape of the electrodes is rectangular, with a width of 3.5mm and a length of 6.5mm. The right angles in the rectangle are chamfered, and the corresponding fillet radius after chamfering is 0.55. The distance between the two electrodes is 3.5mm. The semi-insulating gallium arsenide photoconductive switch is rectangular, with a width of 8.5mm and a length of 10.5mm.

[0081] The ceramic discharge tube uses EPCOS ceramic gas discharge tube A71-H25X.

[0082] The semi-insulated gallium arsenide photoconductive switch is positioned near the input end of the microstrip line, and the ceramic discharge tube is positioned near the output end of the microstrip line. The horizontal distance between the input end of the semi-insulated gallium arsenide photoconductive switch and the SMA interface of the microstrip line input end is 20.5 mm; the distance between the output end of the semi-insulated gallium arsenide photoconductive switch and the input end of the ceramic discharge tube is 10.5 mm.

Claims

1. A dual-mode cascaded nanosecond narrow pulse generator, characterized in that, It includes an optical trigger module, a microstrip line, a photoconductive switch unit and a ceramic discharge tube (7), wherein the optical trigger module operates independently and the laser emitted by the optical trigger module is used to excite the photoconductive switch unit; the photoconductive switch unit and the ceramic discharge tube (7) are integrated in series on the microstrip line.

2. The dual-mode tandem nanosecond narrow pulse generator according to claim 1, characterized in that, The optical triggering module includes at least three pulsed laser emission branches. Each pulsed laser emission branch includes a driving circuit board (8), a pulsed laser diode (9), and an optical fiber (5) connected in sequence. The driving circuit board (8) controls the pulsed laser diode (9) by using a TTL signal. Multiple lasers are coupled through the optical fiber (5) to synchronously irradiate the photoconductive switch unit.

3. The dual-mode tandem nanosecond narrow pulse generator according to claim 2, characterized in that, The microstrip line includes a metal backplate (1), a dielectric layer (2) and three signal lines (3) arranged sequentially from top to bottom; the photoconductive switch unit and the ceramic discharge tube (7) are connected in series on the upper surface of the dielectric layer (2) through the three signal lines (3).

4. The dual-mode tandem nanosecond narrow pulse generator according to claim 3, characterized in that, The metal backplate (1) is made of copper; the dielectric layer (2) is made of Rogers RO4350B; the dielectric layer (2) is rectangular in shape, with a length of 6cm±0.5cm and a width of 3cm-9cm; the signal line (3) is made of copper and has a width of 3mm±0.5mm.

5. The dual-mode tandem nanosecond narrow pulse generator according to claim 3, characterized in that, The photoconductive switch unit includes a semi-insulating gallium arsenide photoconductive switch (6), and two electrodes (4) are provided on the upper surface of the semi-insulating gallium arsenide photoconductive switch (6). The two electrodes (4) are located in the gap between two signal lines (3), and the two electrodes (4) are respectively connected to the adjacent signal line (3). The end of the optical fiber (5) is located above the semi-insulating gallium arsenide photoconductive switch (6), and the laser emitted by the optical fiber (5) irradiates the surface of the semi-insulating gallium arsenide photoconductive switch (6).

6. The dual-mode tandem nanosecond narrow pulse generator according to claim 5, characterized in that, The electrode (4) is a nickel-gold electrode; the electrode (4) is rectangular in shape, with a width of 3mm±0.5mm and a length of 6mm±0.5mm. The right angles in the rectangle are chamfered, and the corresponding rounded corner radius after chamfering is 0.5mm±0.05mm; the distance between the two electrodes (4) is 3mm±0.5mm; the semi-insulating gallium arsenide photoconductive switch (6) is rectangular in shape, with a width of 8mm±0.5mm and a length of 10mm±0.5mm.

7. The dual-mode tandem nanosecond narrow pulse generator according to claim 5, characterized in that, The ceramic discharge tube (7) is an EPCOS ceramic gas discharge tube A71-H25X.

8. The dual-mode tandem nanosecond narrow pulse generator according to claim 7, characterized in that, The semi-insulated gallium arsenide photoconductive switch (6) is positioned near the input end of the microstrip line, and the ceramic discharge tube (7) is positioned near the output end of the microstrip line; the horizontal distance between the input end of the semi-insulated gallium arsenide photoconductive switch (6) and the SMA interface of the input end of the microstrip line is 20mm ± 0.5mm; the distance between the output end of the semi-insulated gallium arsenide photoconductive switch (6) and the input end of the ceramic discharge tube (7) is 10mm ± 0.5mm.

9. A dual-mode cascaded nanosecond narrow pulse generation method, characterized in that, The generator described in any one of claims 1-8 is used as follows: when the required frequency is kHz or below, the TTL signal control mode is used: an external bias voltage is applied to the combination switch, and the pulse laser diode (9) is used to output laser using a TTL level signal. The laser irradiates the surface of the semi-insulating gallium arsenide photoconductive switch (6). The bias voltage is adjusted below the self-breakdown voltage to regulate the amplitude of the output electrical pulse. When the usage requirement is within the MHz range, the self-trigger mode is used: an external bias voltage is applied to the self-breakdown value of the combination switch, and the bias voltage is adjusted when it is greater than the self-breakdown voltage to regulate the frequency of the output electrical pulse.

10. The dual-mode tandem nanosecond narrow pulse generation method according to claim 9, characterized in that, The combined switch consists of a photoconductive switch unit, a ceramic discharge tube (7), and a signal line (3) connecting the two.

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