A power combining system suitable for Marx ultra-wideband pulses

Abstract

The application discloses a power synthesis system suitable for Marx ultra-wideband pulse, comprising: a common output end for outputting an ultra-wideband high-voltage pulse signal after power synthesis; a plurality of continuous gradual transmission arms, pulse input ends of the continuous gradual transmission arms being connected with a plurality of ultra-wideband high-voltage pulse signals generated by a Marx generator, and output ends being connected with the common output end; wherein the continuous gradual transmission arm comprises a first transmission branch and a second transmission branch, impedances of the first transmission branch and the second transmission branch are continuously and gradually distributed along physical lengths, so as to realize smooth transition of the impedance and inhibit high-frequency reflection; and a discrete isolation absorption network is connected between the first transmission branch and the second transmission branch. The application combines the Klopfenstein tapered gradual change theory with the Wilkinson power divider and applies the same to ultra-wideband high-voltage pulse transmission, so that the ultra-high fidelity of a Marx pulse front edge is well maintained.

Description

Technical Field

[0001] This invention relates to the field of power combining system technology, and in particular to a power combining system suitable for Marx ultrawideband pulses. Background Technology

[0002] The development of high-power microwave technology and pulsed power technology is accelerating rapidly. Ultra-wideband high-voltage pulses with steep nanosecond or sub-nanosecond leading edges have irreplaceable application value in cutting-edge fields such as ultrafast electromagnetic environment simulation, high-resolution radar detection, particle acceleration, and strong electromagnetic countermeasures. Regarding pulse generation sources, Marx generators, with their modularity and easy expansion, have become the core means of generating such ultrafast high-voltage pulses. However, the power and voltage output of a single Marx generator are often limited by the physical limits of semiconductor switching devices. To further obtain ultra-high power density pulse signals, power combining technology is needed to converge and superimpose pulses from multiple Marx generators in space or circuitry.

[0003] Traditional broadband microwave power combining typically employs a cascaded multi-stage stepped impedance transformer approach. However, nanosecond / sub-nanosecond high-voltage pulse signals possess extremely wide spectral characteristics extending from DC baseband to the several GHz microwave band. Due to the impedance abrupt changes inherent in the traditional stepped structure, parasitic capacitance and inductance are introduced, leading to severe reflections of high-frequency electromagnetic waves. When a fast pulse containing abundant high-frequency components passes through, group delay distortion and ringing effects occur, disrupting the steep pulse leading edge and rendering the method unsuitable for high-fidelity lossless combining of extremely wideband pulses.

[0004] To address pulse front distortion caused by impedance abrupt changes, Faroq Razzaz et al. proposed a compact ultra-wideband Wilkinson power combining technique based on linearly tapered transmission lines (LTTLs). This technique replaces traditional stepped impedance lines with linearly tapered transmission lines (LTTLs), achieving a continuous physical impedance transition. A small number (1 to 3) of lumped isolation resistors are connected between the two transmission arms to broaden the bandwidth and absorb unbalanced energy. However, the linear taper used in this method is not the optimal impedance transformation distribution, and significant ripple still exists within its passband. Furthermore, this technique is primarily designed for microwave communication frequencies (tested in the 3 GHz to 27 GHz band), and its lower limit cannot extend to the DC baseband. Directly using it to synthesize Marx ultrawideband pulses containing a large number of low-frequency and DC components would result in severe pulse top collapse and waveform distortion, failing to meet the transmission requirements from baseband to the entire microwave frequency band.

[0005] To address the impedance matching problem in ultra-wideband applications, Nagarakshith Mungara proposed using a gradient line structure (Design of Super Wide Band 3-Way Power Divider Combiner) to smooth the impedance transition. While this method eliminates physical abrupt changes, conventional gradient structures do not provide ideal control over the reflection coefficient within the passband for a given physical length, resulting in significant passband ripple. Furthermore, blindly extending the transmission line size to reduce low-frequency reflections leads to substantial pulse amplitude attenuation due to dielectric losses. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a power combining system suitable for Marx ultrawideband pulses.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows: A power combining system suitable for Marx ultrawideband pulses, comprising: The common output terminal is used to output the ultrawideband high-voltage pulse signal after power synthesis. Several continuously tapered transmission arms are provided. The pulse input terminals of the continuously tapered transmission arms are connected to the multi-channel ultra-wideband high-voltage pulse signals generated by the Marx generator, and the output terminals are connected to the common output terminal. The continuously tapered transmission arms include a first transmission branch and a second transmission branch. The impedance of the first transmission branch and the second transmission branch is continuously tapered with the physical length to achieve a smooth impedance transition and suppress high-frequency reflections. A discrete isolation absorption network is connected between the first and second transmission branches to absorb odd-mode reflected energy between multiple input pulses.

[0008] The shape and impedance distribution of the first and second transmission branches are constructed according to the Klopfenstein tapered gradient theory, so that the return loss of the network port exhibits equiripple response characteristics within the extremely wide operating frequency range.

[0009] The discrete isolation absorption network includes multiple discrete isolation resistor elements distributed sequentially along the signal transmission direction.

[0010] The discrete isolation absorption network adopts a multi-section discrete structure, and the number of discrete isolation resistor elements N≥4.

[0011] The resistance values ​​of the plurality of discrete isolation resistors are distributed in a step-like monotonically increasing manner along the signal transmission direction from the pulse input terminal to the common output terminal of the continuously gradually changing transmission arm.

[0012] A gap extending along a gradient curve is provided between the first transmission branch and the second transmission branch, and the plurality of discrete isolation resistor elements are equidistantly connected across both sides of the gap.

[0013] The beneficial effects of this invention are: 1. Continuous Gradual Lossless Transmission Architecture: Abandoning the traditional multi-stage stepped gradual impedance structure, it combines Klopfenstein's tapered gradual theory with Wilkinson power dividers and applies it to ultra-wideband high-voltage pulse transmission. This effectively avoids physical impedance abrupt change points and maintains the extremely high fidelity of the Marx pulse leading edge while achieving ultra-wideband impedance matching.

[0014] 2. Monotonically increasing discrete absorption network: Overcoming the problem that the isolation resistor of the traditional Wilkinson power divider is easily broken down by high voltage and has limited bandwidth, it innovatively adopts multiple discrete resistors for bridging and applies a physical constraint that the resistance value increases monotonically in a step-like manner from 150Ω to 1500Ω along the signal transmission direction.

[0015] 3. Ultra-wideband ripple response: Successfully extended the operating frequency band downward to DC and upward to 6GHz, achieving an equiripple response with S11 < -10dB and isolation S23 stably suppressed below -10dB across the entire frequency band.

[0016] 4. The power combining network of the present invention can cover the DC to microwave frequency bands, has no physical impedance abrupt changes, and has high voltage odd mode absorption capability, and achieves efficient and high-fidelity combining of ultra-wideband pulses. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the present invention; Figure 2 This is a topology diagram of a 4x3 level Marx pulse generation circuit in an embodiment of the present invention; Figure 3 This is a simulation diagram of the high-voltage wideband pulse waveform output by the Marx circuit in an embodiment of the present invention; Figure 4 This is a time-domain transient simulation circuit diagram for verifying the transmission line's fidelity to the pulse leading edge in an embodiment of the present invention; Figure 5 This is a waveform diagram of the fidelity test before and after the transmission of a 4kV high-voltage pulse with a sub-nanosecond leading edge in an embodiment of the present invention. Figure 6 This is a schematic diagram of the physical layout of the 8 sections of Klopfenstein-Discrete Wilkinson in an embodiment of the present invention; Figure 7 This is a diagram illustrating the principle and variable settings of the multi-objective optimization circuit for discrete isolation networks in an embodiment of the present invention. Figure 8The figure shows the joint simulation results of the equiripple S-parameters across the 0-6GHz full frequency band in this embodiment of the invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concepts of the invention.

[0019] like Figure 1 As shown, a power combining system suitable for Marx ultrawideband pulses includes: a common output terminal 2 for outputting the combined ultrawideband high-voltage pulse signal; several continuously tapered transmission arms 1, the pulse input terminals of which are connected to multiple ultrawideband high-voltage pulse signals generated by a Marx generator, and the output terminals of which are connected to the common output terminal 2; wherein, the continuously tapered transmission arm 1 includes a first transmission branch and a second transmission branch, the impedance of which is continuously tapered with the physical length to achieve a smooth impedance transition and suppress high-frequency reflections; and a discrete isolation absorption network 3, which is connected between the first and second transmission branches to absorb the odd-mode reflection energy between multiple input pulses.

[0020] like Figure 1 As shown, the shape and impedance distribution of the first and second transmission branches are constructed according to the Klopfenstein tapered gradient theory, so that the return loss of the network port exhibits equiripple response characteristics within the extremely wide operating frequency range.

[0021] like Figure 1 As shown, the discrete isolation absorption network 3 includes multiple discrete isolation resistor elements distributed sequentially along the signal transmission direction. The discrete isolation absorption network 3 employs a multi-section discrete structure, and the number of discrete isolation resistor elements N ≥ 4. The resistance values ​​of the multiple discrete isolation resistor elements are distributed in a step-like monotonically increasing manner along the signal transmission direction from the pulse input terminal of the continuously tapered transmission arm 1 to the common output terminal 2. A gap extending along the tapered curve is provided between the first transmission branch and the second transmission branch, and the multiple discrete isolation resistor elements are equidistantly connected across both sides of the gap.

[0022] Specifically, the complete system architecture and design steps are as follows: Phase 1: Construction and Verification of an Ultra-Wideband High-Voltage Pulse Excitation Source In this embodiment, the pulse input terminal of the continuously tapered transmission arm 1 is connected to a pulse generation module that generates an extremely wideband excitation signal. To obtain a high-voltage excitation signal with extremely high leading-edge steepness at the sub-nanosecond / nanosecond level, the pulse generation module in this embodiment preferably employs a Marx circuit topology based on avalanche transistors.

[0023] Before determining the specific circuit architecture, the dynamic characteristics of avalanche breakdown of the avalanche transistor under high-speed switching conditions were first modeled and simulated. Based on this, the comprehensive influence of the number of stages in the Marx circuit on the output pulse characteristics was further systematically simulated and analyzed. Research and extensive simulation results show that the number of stages in the pulse source directly affects the output pulse shape; appropriately increasing the number of stages can effectively improve the peak voltage of the output pulse, but too many stages will introduce additional parasitic inductance and distributed capacitance, resulting in a slower pulse leading edge and distortion of high-frequency spectral components.

[0024] Therefore, in order to achieve the best physical balance between "high voltage output" and "extremely steep leading edge", after multiple parameter scans, optimizations, and adjustments, the optimal result was finally selected as follows: Figure 2 As shown, a specific 4x3 Marx circuit architecture is used as the pulse generation source for this system. Combined with... Figure 2 circuit topology and Figure 3 The waveform simulation results show that the 4x3 Marx circuit can stably and efficiently generate high-voltage steep-front pulses in the nanosecond / sub-nanosecond range, and the actual physical circuit test results are consistent with the simulation results (pulse voltage peak value -2kV). The pulse signal has an extremely wide spectrum, covering the frequency band from DC to several GHz, providing an ideal physical excitation source for lossless power synthesis in subsequent stages.

[0025] Phase Two: Theoretical Derivation and Single-Arm Design Verification of Ultra-Wideband Lossless Transmission To address the issue of leading-edge distortion and dispersion of nanosecond-level pulses in traditional stepped transmission lines, we first verified the fidelity of continuously tapered long-distance transmission lines for pulse leading edges. Specifically, based on the low-loss RF substrate Rogers5880, a time-domain transient simulation model of a 50-cm-long transmission line with a corresponding ultra-wideband lower limit was constructed. By inputting a high-voltage transient pulse with a rise time of hundreds of picoseconds into this model, we extracted the amplitude attenuation and leading-edge degradation data of the signal after long-distance transmission.

[0026] like Figure 4 and Figure 5 By establishing a 50 cm long, 50 Ω Rogers 2880 microstrip line model in ADS simulation software, the fidelity of ultrafast pulse leading edge transmission over long distances and Rogers 5880 medium transmission was verified. The simulation was of 4KV pulse transmission with a leading edge of <100 ps.

[0027] The simulation results above show that, under the premise of meeting the high voltage insulation thickness, the dispersion effect of the underlying physical medium does not cause destructive broadening of the ultrafast pulse leading edge, thus demonstrating the feasibility of using a large-size continuous gradient structure to achieve low-distortion transmission.

[0028] like Figure 1 As shown, this invention employs a Klopfenstein continuously tapered transmission arm, abandoning the traditional stepped design. Instead, it constructs a continuous impedance variation based on theoretical calculations. In the specific design, numerical calculation software (such as MATLAB) is used to perform rigorous impedance calculations based on Klopfenstein's tapered theory. By setting the maximum permissible reflection coefficient within the target bandwidth (DC to 6GHz), a mathematical model of the optimal impedance distribution is constructed, thereby accurately calculating the continuous impedance variation curve of the single-arm transmission line along its physical length. Subsequently, a single-arm physical model is constructed based on the calculation results, and electromagnetic simulations are performed. The single-arm simulation results demonstrate that this continuously tapered structure effectively avoids abrupt changes in physical impedance, achieving ultra-wideband impedance matching while maintaining extremely high fidelity of the Marx pulse leading edge.

[0029] Phase 3: Construction of the power combining joint architecture and optimization of the discrete absorption network Based on the successful verification of the single-arm design, this embodiment combines them in a mirror image to construct a Y-shaped synthetic physical architecture, where the continuously tapered transmission arm 1 is constructed as the first and second transmission branches. To achieve extremely high isolation between multiple pulses and absorb odd-mode reflection energy over an extremely wide bandwidth, a discrete Wilkinson absorption network is innovatively introduced at the gap between the first and second transmission branches.

[0030] In the co-simulation and optimization phase, this embodiment takes into account the parasitic parameters of actual physical components, adds a model of a real-packaged resistor component to the circuit model, and performs co-optimization on the system. For example... Figure 6 As shown in the physical layout, a discrete Wilkinson absorption network is introduced at the gap between the two tapered transmission arms. Specifically, the discrete isolation absorption network 3 consists of multiple (preferably 8) discrete isolation resistor elements.

[0031] After determining the initial architecture of the discrete Wilkinson absorption network, this embodiment introduces a multi-objective collaborative optimization strategy to overcome the physical limit of broadband isolation. Specifically, in the co-simulation step of this embodiment, a multi-parameter optimization model is constructed. First, the preset optimization objective of the system is set: within the full frequency band from 0Hz to 6GHz, the return loss parameter S11 at the input end is constrained to be less than -10dB, and the isolation parameter S23 between each output port is simultaneously constrained to be less than -10dB. Second, the resistance values ​​of the eight discrete resistors are used as optimization variables. To avoid conventional optimization algorithms getting stuck in local optima under extremely wide bandwidth conditions and producing physically meaningless resistance values ​​(e.g., optimizing to 25Ω leading to the illusion of total reflection), and to overcome the physical limit of isolation exceeding four octaves, this invention innovatively introduces physical boundary constraints in this step: for example... Figure 7 In this multi-objective optimization circuit and variable allocation (VAR) configuration, strict physical constraints were imposed on the eight discrete resistors, mandating that the resistance variable along the signal transmission direction exhibit a monotonically increasing trend, and that the resistance value range be strictly constrained to between 150Ω and 1500Ω. Finally, a global random algorithm (Random) was used for large-scale calculations to determine the initial solution space, followed by local fine-tuning calculations using the gradient algorithm (Gradient). Through this multi-objective collaborative optimization process, the equiripple response of the system was ultimately approximated and realized, and the optimal stepped increasing resistance value sequence was determined.

[0032] To elaborate further, such as Figure 7 As shown, this co-simulation optimization platform mainly consists of a core electromagnetic parameter module, a discrete resistance variable module, a multi-objective function module, and an optimization engine module working together. Co-simulation topology and bandwidth settings: Figure 7 The central multi-port network module (SnP module) imported the passive electromagnetic simulation data of the previously constructed Klopfenstein continuously tapered transmission arm. Eight discrete isolation resistors were sequentially connected across each physical port corresponding to the slot. Meanwhile, the simulation controller (S-PARAMETERS) on the left side of the figure strictly set the frequency band to 0 GHz to 6 GHz, ensuring the effectiveness of the optimized ultra-wideband.

[0033] Multi-objective optimization function and algorithm engine: In order to suppress odd-mode reflections over an extremely wide bandwidth, Figure 7 The top right corner houses the Optimization Objective Function (GOAL) module, whose core expression is set to track and minimize dB(S(2,3)), which forces the system to achieve high isolation between each pulse input across the entire frequency band. Meanwhile, the bottom right corner's Optimization Engine (OPTIM) module employs a gradient algorithm for local fine-tuning and sets a maximum number of iterations (MaxIters=300) to ensure algorithm convergence.

[0034] Core physical boundary constraints and resistance verification: To prevent the optimization algorithm from getting trapped in local optima under ultra-wideband conditions, this invention imposes mandatory physical constraints. Combined with... Figure 7 The variable setting module (VAR) in the lower left corner shows that after multi-objective collaborative optimization, the resistance variables (R1_val to R8_val) of R1 to R8 eventually converge to a specific numerical sequence: that is, gradually and monotonically increasing from 149.904Ω near the input end to 1499.74Ω near the output end.

[0035] Figure 7 This intuitively confirms that the "discrete isolation resistor element resistance value exhibiting a step-like monotonically increasing distribution" proposed in this embodiment is not randomly set, but rather an optimal analytical solution obtained after overcoming the physical limits of traditional microwave devices through rigorous electromagnetic-circuit joint optimization methods. It is precisely based on... Figure 7 The incremental resistance architecture shown allows the system to achieve an extremely wideband ripple isolation response without being broken down by high voltage.

[0036] In an optimal co-simulation embodiment, the resistance values ​​of the eight isolation resistors were precisely set to monotonically increase from 150Ω near the input to 1500Ω near the output. Test and co-simulation data show that this combination of "Klopfenstein continuous gradient + discrete resistor network with increasing resistance at the gaps" architecture enables the system to achieve a classic equal-ripple response in RF. Ultimately, as... Figure 8 The S-parameter co-simulation results show that the input return loss S11 of the power combining network is always suppressed to below -10dB in the extreme broadband range of 0Hz (DC) to 6GHz; at the same time, the isolation S23 between each port is smoothly and uniformly suppressed and stabilized to below -10dB, realizing high-fidelity and high-isolation combining of ultra-wideband high voltage pulses.

[0037] To elaborate further, such as Figure 8 As shown in the figure, this diagram reflects the system's performance in multi-objective collaborative optimization (i.e., Figure 7 The final frequency domain response characteristics after completing the steps shown are illustrated. The horizontal axis in the figure represents frequency, and the vertical axis represents the amplitude of the S-parameters. These two core curves directly demonstrate the progress of this invention's embodiments: Ultra-wideband reflection-free matching characteristics (as shown by the red line S in the figure) 11 As shown): S 11 This represents the return loss at the pulse input. (The rest of the text appears to be a typo or incomplete sentence fragment.) Figure 8 As indicated by the red line, within the extreme bandwidth range of 0 Hz (DC) to 6 GHz, the system's S 11The parameters exhibit highly regular "equiripple" fluctuations, and their peak values ​​are remarkably suppressed to below -10 dB. This directly demonstrates physically that the use of the Klopfenstein continuously tapered transmission arm effectively reduces the abrupt changes in physical impedance of traditional step synthesizers. When Marx nanosecond-level pulses containing rich high- and low-frequency components enter this network, high-frequency reflections are effectively reduced, thereby ensuring efficient pulse energy transmission and extremely high fidelity of the pulse leading edge.

[0038] Full-band odd-mode energy absorption and high isolation characteristics, as shown by the blue line S in the figure. 23 As shown: S 23 This represents the isolation between each pulse input port. (The rest of the text appears to be a fragment and doesn't translate directly.) Figure 8 As shown by the blue line, within the same 0-6 GHz ultra-wideband, the isolation parameter S 23 It also exhibits excellent equiripple response, remaining stable below -10 dB. This demonstrates the crucial role played by the innovative "8-section discrete Wilkinson absorption network with monotonically increasing resistance in a stepped manner" introduced in this invention. It breaks the limitation of traditional Wilkinson power dividers, which can only operate within 20% of the bandwidth around the center frequency, and evenly distributes odd-mode reflected energy across 8 physical nodes for absorption. In practical multi-channel high-voltage Marx pulse synthesis applications, even with timing jitter, this system can provide sufficient isolation protection over an extremely wide frequency band, reducing the engineering problem of single-section resistors burning out due to instantaneous overload of high-voltage differential signals.

[0039] comprehensive Figure 8 The simulation results lead to the conclusion that this invention combines a Klopfenstein continuous gradient structure with an incremental discrete resistor network to achieve efficient and high-fidelity synthesis of ultra-wideband pulses, covering the DC to microwave frequency bands, without physical impedance abrupt changes, and possessing high voltage odd-mode absorption capability.

[0040] In this invention, different Marx circuit stages or isolation absorption networks with different number of sections can also be used. The pulse generation module at the front end is not limited to a 4x3 Marx circuit and can be replaced with Marx circuits of other stages or other types of sub-nanosecond broadband high-voltage pulse sources. The number of sections in the discrete Wilkinson isolation absorption network is not limited to 8 sections and can adopt a discrete resistor topology of 4 sections or more that satisfies the monotonically increasing law of resistance step.

[0041] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of the invention and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of the invention should be included within the protection scope of the invention. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

Claims

1. A power combining system suitable for Marx ultrawideband pulses, characterized in that, include: The common output terminal (2) is used to output the ultra-wideband high-voltage pulse signal after power synthesis; Several continuously tapered transmission arms (1) are provided. The pulse input end of the continuously tapered transmission arm (1) is connected to the multi-channel ultra-wideband high-voltage pulse signal generated by the Marx generator, and the output end is connected to the common output end (2). The continuously tapered transmission arm (1) includes a first transmission branch and a second transmission branch. The impedance of the first transmission branch and the second transmission branch is continuously tapered with the physical length to achieve a smooth impedance transition and suppress high-frequency reflection. A discrete isolation absorption network (3) is connected between the first transmission branch and the second transmission branch to absorb the odd-mode reflected energy between multiple input pulses.

2. The power combining system for Marx ultrawideband pulses according to claim 1, characterized in that, The shape and impedance distribution of the first and second transmission branches are constructed according to the Klopfenstein tapered gradient theory, so that the return loss of the network port exhibits equiripple response characteristics within the ultra-wideband operating frequency range.

3. The power combining system for Marx ultrawideband pulses according to claim 1, characterized in that, The discrete isolation absorption network (3) includes multiple discrete isolation resistor elements distributed sequentially along the signal transmission direction.

4. A power combining system suitable for Marx ultrawideband pulses according to claim 3, characterized in that, The discrete isolation absorption network (3) adopts a multi-section discrete structure, and the number of discrete isolation resistor elements N≥4.

5. A power combining system suitable for Marx ultrawideband pulses according to claim 4, characterized in that, The resistance values ​​of the plurality of discrete isolation resistor elements are distributed in a step-like monotonically increasing manner along the signal transmission direction from the pulse input terminal of the continuously gradually changing transmission arm (1) to the common output terminal (2).

6. A power combining system suitable for Marx ultrawideband pulses according to claim 5, characterized in that, A gap extending along a gradient curve is provided between the first transmission branch and the second transmission branch, and the plurality of discrete isolation resistor elements are equidistantly connected across both sides of the gap.

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